bluuebunny/crossref_metadata_2025 huggingface dataset:
Differential myelinogenic capacity of specific developmental stages of the oligodendrocyte lineage upon transplantation into hypomyelinating hosts
Authors: Warrington A. E. , Barbarese E. , Pfeiffer S. E.
Published: May 2005

The capacity of oligodendrocytes (OLs) and their progenitors to migrate, proliferate, and differentiate in vivo was evaluated by transplanting highly enriched populations of sequential stage of the OL lineage (A2B5+ O4−, O4+ GalC−, and GalC+) into the telencephalon of the hypomyelinating mouse, shiverer. The shiverer mouse neither expresses the major myelin basic protein (MBP) nor makes normal myelin due to a large deletion in the gene for MBP. Thirty days after transplantation, serial 225 μm sections of the host brain were immunostained with antiserum to MBP and analyzed by confocal microscopy. The presence of MBP+ patches of myelin in the otherwise MBP− host brain allowed a retrospective analysis of the myelinogenic activity of the transplanted progenitors cells. Both the extent of MBP+ myelin and the location of MBP+ structures relative to the initial site of cell deposition were highly dependent on the developmental stage of the transplanted cells. Specifically, A2B5+ O4− OL progenitors migrated distances of ≥ 600 μm and produced MBP+ patches in nearly every slice of the host brain. An average of over 250 separate patches were found per host brain, some of which had cross‐sectional areas of > 250,000 μm2 containing as many as 60 MBP+ OL cell bodies, and with densities of myelination rivaling that of normal brain. In marked contrast, transplantation of O4+ GalC− cells produced only small (1,000–25,000 μm2), scattered (25–40 per brain) patches of MBP+ myelin containing one to five cell bodies, all of which were within 50 μm of the needle track or the nearest ventricular surface. GalC+ cells produced MBP+ myelin at a level similar to that of O4+ CalC− cells. These data suggest that the developmental transition of OL progenitors from the O4− to the O4+ pheno‐type is accompanied by a dramatic reduction in the innate capacity of the cells to migrate and survive in vivo. The use of developmentally identified, enriched populations of OL progenitor cells offers the opportunity for more precise analyses of transplantation and remyelination behavior, and relates to clinically relevant studies indicating that contaminant cell types can seriously interfere with the stable integration of donor tissue into the host. © 1993 Wiley‐Liss, Inc.
Induction of myelin genes during peripheral nerve remyelination requires a continuous signal from the ingrowing axon
Authors: Gupta S. K. , Pringle J. , Poduslo J. F. , Mezei Catherine
Published: May 2005

The effect of a permanent transection on myelin gene expression in a regenerating sciatic nerve and in an adult sciatic nerve was compared to establish the degree of axonal control exerted upon Schwann cells in each population. First, the adult sciatic nerve was crushed, and the distal segment allowed to regenerate. At 12 days post‐crush, the sciatic nerve was transected distal to the site of crush to disrupt the Schwann cell‐axonal contacts that had reformed. Messenger RNA (mRNA) levels coding for five myelin proteins were assayed in the distal segment of the crush‐transected nerve after 9 days and were compared to corresponding levels in the distal segments of sciatic nerves at 21 days post‐crush and 21 days post‐transection using Northern blot and slot‐blot analysis. Levels of mRNAs found in the distal segment of the transected and crush‐transected nerve suggested that Schwann cells in the regenerating nerve and in the mature adult nerve are equally responsive to axonal influences. The crush‐transected model allowed the genes that were studied to be classified according to their response to Schwann cell‐axonal contact. The levels of mRNAs were (1) down‐regulated to basal levels (PO and MBP mRNAs), (2) down‐regulated to undetectable levels (myelin‐associated glycoprotein mRNAs), (3) upregulated (mRNAs encoding 2′3′‐cyclic nucleotide phosphodiesterase and β‐actin), or (4) not stringently controlled by the removal of Schwann cell‐axonal contact (proteolipid protein mRNAs). This novel experimental model has thus provided evidence that the expression of some of the important myelin genes during peripheral nerve regeneration is dependent on continuous signals from the ingrowing axons. © 1993 Wiley‐Liss, Inc.
Electrophysiologic and molecular properties of cultured enteric glia
Authors: Broussardy D. L. , Bannerman P. G. C. , Tang C.‐M. , Hardy M. , Pleasure D.
Published: May 2005

Enteric glia, the support cells of myenteric ganglia, have been widely studied with respect to their morphology and immunohistochemical phenotype, but little is known about their functional properties. We developed a method for the amplification of enteric glia from newborn guinea pigs to further characterize these cells. Treatment with a combination of basic fibroblast growth factor and the adenylate cyclase activator, cholera toxin, permitted expansion of enteric glial cultures to confluence and serial passage for up to 8 months. The long‐term cultured cells retained expression of (1) S100 protein, (2) GD3 ganglioside recognized by the monoclonal antibody LB1, and (3) the gene encoding glutamine synthetase. The electrophysiologic properties of cultured enteric glia were studied under whole‐cell patch clamp conditions. Most cells expressed “delayed rectifier”‐type potassium currents, and some also demonstrated tetrodotoxin‐sensitive sodium currents. Other subsets of voltage‐dependent potassium currents, calcium currents, and glutamate‐gated currents were not demonstrable. © 1993 Wiley‐Liss, Inc.
Transforming growth factor β as a neuronoglial signal during peripheral nervous system response to injury
Authors: Rogister B. , Delrée P. , Leprince P. , Martin D. , Sadzot C. , Malgrange B. , Munaut C. , Rigo J. M. , Lefebvre P. P. , Octave J.‐N. , Schoenen J. , Moonen G.
Published: May 2005

In contrast to the central nervous system (CNS), the peripheral nervous system (PNS) displays an important regenerative ability which is dependent, at least in part, on Schwann cell properties. The mechanisms which stimulate Schwann cells to adapt their behavior after a lesion to generate adequate conditions for PNS regeneration remain unknown.

In this work, we report that adult rat dorsal root ganglion (DRG) neurons are able, after a lesion performed in vivo or when they are dissociated and cultured in vitro, to synthesize transforming growth factor β (TGFβ), a pleiotropic growth factor implicated in wound healing processes and in carcinogenesis. This TGFβ is tentatively identified as the β‐1 isoform. Adult rat DRG neurons release a biologically active form of TGFβ which is able to elicit multiple Schwann cell responses including a stimulation to proliferate. Moreover, purified TGFβ‐1 produces a Schwann cell morphology alteration and decreases the secretion of tissue‐type plasminogen activator (tPA) and enhances the secretion of plasminogen activator inhibitor (PAI) by Schwann cells. This generates conditions which are thought to favor a successful neuritic regrowth. Furthermore, purified TGFβ‐1 stimulates type IV collagen mRNA expression in Schwann cells. This subtype of collagen is associated with the process of myelinization. Finally, TGFβ‐1 decreases nerve growth factor (NGF) mRNA expression by Schwann cells, an effect which could participate in the maintenance of a distoproximal NGF gradient during nerve regeneration.

We propose that neuronal TGFβ plays an essential role as a neuronoglial signal that modulates the response of Schwann cells to injury and participates in the successful regeneration processes observed in the PNS. © 1993 Wiley‐Liss, Inc.
Congruity of acetylcholine receptor, acetylcholinesterase, and Dolichos biflorus lectin binding glycoprotein in postsynaptic‐like sarcolemmal specializations in noninnervated regenerating rat muscles
Authors: Črne‐Finderle N. , Sketelj J.
Published: May 2005

Noninnervated regenerating muscles are able to form focal postsynaptic‐like sarcolemmal specializations either in places of the former motor endplates ( “junctional” specializations) or elsewhere along the muscle fibers (extrajunctional specializations). The triple labeling histochemical method was introduced to analyse the congruity of focalization in such specializations of 3 synaptic components: acetylcholinesterase (AChE), acetylcholine receptor (AChR), and a specific synaptic glycoprotein which binds Dolichos biflorus lectin (DBAR). Noninnervated regenerating soleus and extensor digitorum longus (EDL) muscles of the rat were examined and compared with denervated muscles of neonatal and adult rats.

All junctional sarcolemmal specializations in noninnervated regenerating muscles accumulated AChE and AChR. Localization of the 2 components was identical within the limits of resolution of the method. DBAR could not be demonstrated in junctional specializations in 17‐day‐old regenerating muscles. It seems that an agrin‐like inducing substance in the former junctional basal lamina invariably triggers the accumulation of both AChE and AChR in the underlying sarcolemma of the regenerating muscle fiber. However, accumulation of DBAR would probably require the presence of the motor nerve.

In most of the extrajunctional sarcolemmal specializations in 8‐day‐old regenerating soleus and EDL muscles, both AChE and AChR accumulated. However, about 10 percent of AChE accumulations lacked AChR and about 35% of AChR accumulations lacked AChE. Even greater variability was observed in 17‐day‐old regenerating muscles. The presence of DBAR in the extrajunctional postsynaptic‐like sarcolemmal specializations could not be demonstrated. Similar extrajunctional sarcolemmal specializations were observed in denervated postnatal rat muscles. About 70% contained both AChE and AChR, and 30% contained only AChR, but none contained DBAR. In denervated mature muscles, sparse extrajunctional AChR accumulations did not contain detectable amounts of AChE. The ability to form complex postsynaptic‐like sarcolemmal specializations in the absence of nerve, which is probably inherent to noninnervated immature muscle fibers, may be reduced with muscle maturation. Variable accumulation of individual components in the postsynaptic‐like specializations indicates that different triggering factors may be involved in their accumulation or, at least, the mechanisms of their accumulation can function relatively independently. © 1993 Wiley‐Liss, Inc.
Synaptophysin – a common constituent of presumptive secretory microvesicles in the mammalian pinealocyte: A study of rat and gerbil pineal glands
Authors: Redecker P. , Bargsten G.
Published: May 2005

Recent studies have established that pinealocytes of the mammalian pineal gland contain marker molecules of neuroendocrine cells or paraneurons like the synaptic vesicle‐associated protein synaptophysin (p38). The objective of this study was to identify the subcellular synaptophysin‐positive compartment and to characterize in detail the intracellular distribution of this protein in rat and gerbil pinealocytes. An analysis of serial semithin sections of plastic‐embedded pineals immunostained for synaptophysin, including computer‐assisted optical density measurements of synaptophysin immunoreactivities, demonstrated unequivocally that synaptosphysin was highly concentrated in dilated process terminals of the pinealocytes. More than 75% of these process terminals were found to border or lie within the pericapillary space. At the ultrastructural level, they contained accumulations of small clear vesicles of variable size that turned out to be the site of synaptosphysin immunoreactivity when immunogold staining was performed. In addition, microvesicles surrounding synaptic ribbons were also immunolabeled. Hence, the pinealocyte is the first neuroendocrine cell type that has now been shown to concentrate synaptophysin‐positive microvesicles in perivascular process endings. This observation lends strong support to the hypothesis that small clear vesicles in neuroendocrine cells in general, and in pinealocytes in particular, serve secretory functions. The quantitative analysis of completely sectioned process endings revealed that the microvesicles outnumber by far the amount of dense core vesicles and therefore cannot arise by endocytosis of dense core vesicle membranes. Thus, small synaptic‐like vesicles probably constitute an independent secretory pathway of the paraneuronal pinealocytes.

In the present study, we could also establish the absence of immunoreactivity for synapsin I (belonging to a family of neuron‐specific nerve terminal phosphorproteins) from pinealocytes. Synapsin I immunoreactivity was only detectable in intrapineal nerve terminals and varicosities. Taken together, the immunostaining patterns of the pineal gland obtained with antibodies directed against synaptic vesicle‐associated proteins render the mammalian pinealocyte a very special type of neuroendocrine cell or paraneuron rather than a “classic” neuron. © 1993 Wiley‐Liss, Inc.
Hydroxyl radical production and lipid peroxidation paralles selective post‐ischemic vulnerability in gerbil brain
Authors: Hall Edward D. , Andrus P. K. , Althaus J. S. , Von Voigtlander P. F.
Published: May 2005

The salicylate trapping method was used to investigate the changes in hydroxyl radical (·OH) levels in the selectively vulnerable hippocampus compared to the cerebral cortex of gerbils subjected to a 10 min period of near complete forebrain ischemia. Salicylate‐derived 2,5‐dihydroxybenzoic acid (2,5‐DHBA) was measured in sham‐operated animals and at 1, 5, and 15 min of reperfusion. A basal level of 2,5‐DHBA was also seen in non‐ischemic gerbil brain, both in the hippocampus and cortex. The hippocampal basal level was 160% higher than in the cortex (P < .01). Treatment with the cytochrome P450 inhibitor SKF‐525A (50 mg/kg s.c. 30 min before measurement) did not affect this basal level in either hippocampus or cortex, which argues against a contribution of metabolic salicylate hydroxylation as its source. In contrast, pretreatment with the arachidonic acid cyclo‐oxygenase inhibitor ibuprofen (20 mg/kg s.c.) decreased (−68.8%) the level of salicylate hydroxylation in the hippocampus, but not the cortex. In animals subjected to 10 min of forebrain ischemia, a selective increase in 2,5‐DHBA was observed in the hippocampus at 1 min of reprerfusion which subsided by 5 min. No increase in salicylate hydroxylation was apparent in the cortex within the same time frame. The increase in ·OH in the hippocampus at 1 min of reperfusion was accompanied by a significant decrease (−15%; P < .03) in the hippocampal levels of vitamin E. No loss of vitamin E was observed in the cortex at the same time. It is hypothesized that the selective ischemic vulnerability of the hippocampus is mechanistically related to a selective post‐ischemic burst in ·OH in that region. Moreover, this may be based upon an intrinsically higher level of oxidative stress in that region as a by‐product of greater arachidonic acid turnover. © 1993 Wiley‐Liss, Inc.
Temperature‐dependent Raman scattering studies of improper and antidistortive phase transitions in (NH4)2Cd2(SO4)3
Authors: Galzerani J. C. , Katiyar R. S.
Published: May 2005

Polarized Raman spectra of single crystals of (NH4)2Cd2(SO4)3 were studied at temperatures from room temperature to 13 K. Several temperature‐dependent variations in the phonon frequencies were observed that are related to the structural phase transitions in the material. The existence of a ferroelectric‐paraelectric phase transition was established at 91.5 K. The observed spectra suggested the existence of a new phase transition at about 162 K. This new transition is believed to be of antidistortive type, which is triggered by the softening of a phonon from the Brillouin zone boundary.
Molecular dynamics of antimony trichloride in crystals of bimolecular menshutkin complexes with benzene, diphenyl and phenanthrene by Raman spectroscopy
Authors: Kondyurin A. V. , Mikov S. N. , Kozulin A. T.
Published: May 2005

The Raman spectra of bimolecular complexes crystals of antimony trichloride with benzene, diphenyl and phenanthrene were studied at 77 K. A group theoretical analysis and normal coordinates analysis of the antimony trichloride vibrations in complexes was made. The variation of force field with the gas‐crystal phase change parameters of intermolecular interaction was defined. The interpretation of the lattice mode region was accomplished.
Novel approach for the rapid determination of water‐soluble organic acids in wine by co‐electroosmotic flow capillary zone electrophoresis
Authors: Bianchi Federica , Careri Maria , Corradini Claudio
Published: May 2005

An innovative protocol for the fast analysis of some organic acids in red wine by co‐electroosmotic capillary zone electrophoresis and indirect UV detection using hexadimethrine bromide (HDB) as coating agent was proposed. The adsorption of HDB onto the capillary wall provided a stable electroosmotic flow and separation of small anions was carried out using background electrolytes containing no polymer additive. Low RSD% values (<3.6%) in terms of migration times and effective mobilities were obtained from the analysis of a mixture of nitrate and nitrite and of a mixture of organic acids. An experimental design approach was used to investigate the effects of temperature, separation voltage, and percentage of methanol added to the running buffer solution on the separation of the analytes. A faster method allowing the separation of the organic acids involved in the malolactic fermentation of wine was developed. Using a running electrolyte consisting of 35% (v/v) methanol in a solution of 22 mM benzoic acid at pH 6.10 adjusted with 1.0 M TRIS‐base buffer, the separation of tartaric, malic, succinic, acetic, and lactic acids was feasible in less than 210 s. Application of the method to the quantification of the above‐mentioned organic acids in Italian red wine samples is reported.
Separation and analysis of the major constituents of cloves by micellar electrokinetic chromatography
Authors: Mandrioli Roberto , Musenga Alessandro , Ferranti Anna , Lasaponara Stefano Savino , Fanali Salvatore , Raggi Maria Augusta
Published: May 2005

A micellar electrokinetic chromatographic method was developed and applied for the first time to the separation and quantification of the main components of cloves, namely eugenol and β‐caryophyllene. The analytes were separated in less than ten minutes in an unmodified fused silica capillary (effective length: 40.0 cm) using a background electrolyte composed of 25 mM carbonate buffer (pH 10.0) and 60 mM sodium dodecylsulfate. Analyte concentrations were determined in clove oil and in methanolic clove extracts after simple sequential dilution with methanol and background electrolyte, and the resulting electropherograms showed no interference due to other components. Precision assays gave satisfactory results, with mean standard deviation of peak areas lower than 4.7% (lower than 1.5% for migration times). The eugenol content of a commercial clove oil was about 70% (RSD% = 3.2), while that of β‐caryophyllene was about 15% (RSD% = 4.2); in clove extracts, on the other hand, eugenol was approximately 15% (RSD% = 4.7) and β‐caryophyllene 4% (RSD% = 5.1). Accuracy was also good (mean recovery >98%)
Untersuchungen über die Korrosion einiger Metalle und Metalloxyde in Natriumhydroxydschmelzen
Authors: Rahmel A. , Krüuger H.‐J.
Published: May 2005

Ziel der Untersuchungen war, einen Beitrag zur Aufklärung der Reaktionsabläufe zu leisten, die in den besonders für die Entzunderung von hochlegierten Chrom‐ und Chrom‐Nickel‐Stählen benutzten

Die Untersuchungen erfolgten an den Metallen Silber, Gold, Platin, Nickel und Eisen und an den Metalloxyden FeO, Fe3O4, Fe2O3 und Cr2O3 in NaOH‐Schmelzen bei Temperaturen um 500°C. Besondere Aufmerksamkeit wurde dem Einfluß der Gasatmosphäre auf die Korrosionsgeschwindigkeit gewidmet.

Mit Ausnahme des Silbers ist die Korrosion aller untersuchten Metalle und Oxyde unter Sauerstoff erheblich größer als unter Stickstoff, wobei ein Zusatz von Wasserdampf besonders unter Sauerstoff die Korrosion stark inhibiert. Unter wasserdampfhaltigem Stickstoff ist der Angriff der reinen NaOH‐Schmelzen praktisch vernachlässigbar. Nur Silber korrodiert bei Gegenwart von Wasserdampf stärker als unter trockenen Gasen. Die Korrosionsprodukte wurden chemisch, metallographisch sowie durch Röntgen‐ und Elektronenbeugung untersucht.

Die geringe Korrosion unter Stickstoff zeigt, daß die Reaktion zwischen Metallen bzw. Metalloxyden und der NaOH‐Schmelze nicht oder nur recht langsam abläuft. Die beschleunigende Wirkung des Sauerstoffs und die inhibierende des Wasserdampfes deuten darauf hin, daß der Natriumperoxydgehalt der Schmelze in den meisten Fällen entscheidend für die Korrosionsgeschwindigkeit ist.
NaDDC as a corrosion inhibitor of brass
Authors: Shah R. S. , Trivedi A. M.
Published: May 2005

The carbamate turns out to be a good inhibitor of the corrosion of brass (80/20 and 59/41) in 0.5 N sodium chloride, 1.0 n sodium hydroxide and buffer solutions (NaOH and citric acid, pH 4.4‐6.0). The inhibiting effect depends on inhibitor concentration, so that in some cases corrosion may even be stimulated. The inhibitor effect is attributed to the formation of insoluble complexes with the two alloy components.
Schutz von Materialien vor mikrobieller Zerstörung
Authors: Brill H.
Published: May 2005

Der allgemeine Materialschutz hat zum Ziel, ein gegebenes Material über einen ausreichend langen Zeitraum unter den vorliegenden Bedingungen unverändert zu erhalten. Hierzu müssen möglichst alle schädigenden oder zerstörenden Einflüsse ausgeschaltet werden, da hierdurch hohe wirtschaftliche Verluste auftreten. Die produktschädigenden Einflüsse können physikalisch oder chemisch sowie biologisch bedingt sein. Zum Schutz der Materialien bieten sich verschiedene Maßnahmen an. Es sind dieses physikalische, chemische Verfahren und Schutzmaßnahmen durch Überzüge und Beschichtungen. Häufig werden Kombinationen verschiedener Schutzverfahren eingesetzt. Ziel der Forschungsaufgaben hinsichtlich des allgemeinen Materialschutzes ist es, die vorliegenden physikalischen und chemischen Verfahren zu verbessern und neue Methoden oder Technologien zu entwickeln, welche zu den bestehenden Vorteile bieten, insbesondere in Bezug auf die Wirksamkeit, Verträglichkeit und Toxizität.
Pitting of austenitic stainless steel clad metals
Authors: Krishnan K. N. , Prasad Rao K.
Published: May 2005

Austenitic stainless steel welds with different ferrite contents (4 and 12 FN) were obtained by the Submerged Arc Welding (SAW) strip cladding process, and some clads were remelted by TIG. The welds were post weld heat treated (PWHT) at 600, 800, 1000°C for 1 h. Pitting potentials were measured in 1 N H2SO4 + 0.5 N NaCl. Etching at the pitting potentials was carried out in the same solution in order to locate the pit sites; pitting studies were also conducted in 10% FeCl3 solution.

The results showed that an increase in ferrite content decreases pitting resistance. PWHT at 800°C decreases pitting resistance, too, whereas PWHT at 1000°C results in increased pitting resistance at austenite/ferrite interfaces. TIG samples showed less pits than their SAW counterparts.
The extraction of cholesterol from solid and liquid matrices using supercritical CO2
Authors: Ong Chye Peng , Ong Hui Ming , Li Sam Fong Yau , Lee Hian Kee
Published: May 2005

The design and construction of a relatively simple supercritical CO2 system capable of extracting compounds from solid and liquid matrices are described. The system consists of a conventional liquid chromatography pump, a cooler, a stainless steel extraction chamber, and a modified collection system. A preliminary evaluation of the extractor is carried out here by using it to extract cholesterol from egg yolk and blood serum. The extracts were analyzed by supercritical fluid chromatography, and the results compared with those obtained by Soxhlet extraction.
Determination of pyruvate, acetoacetate, lactate, and 3‐hydroxybutyrate in plasma of patients with diabetes mellitus by capillary isotachophoresis
Authors: Kr̆ivánková Ludmila , Boc̆ek Petr
Published: May 2005

An isotachophoretic method was developed and optimized for simultaneous determination of pyruvate, acetoacetate, lactate, and 3‐hydroxybutyrate in 1–10 μL of untreated heparin plasma of patients with diabetes mellitus. A commercial instrument with a column switching system was used. The preseparation capillary was filled with the leading electrolyte of pH 4.2 and the analytical capillary was filled with leading electrolyte of pH 3.0. The concentrations of individual ketone bodies and lactate found in human plasma varied within 0.01–1.4 mmol/L and 0.8–11.8 mmol/L, respectively. Analysis time was about 30 min.
Application of capillary supercritical fluid chromatography–double focusing mass spectrometry under negative ion chemical ionization conditions
Authors: Huang Eric C. , Jackson Bruce J. , Markides Karin E. , Lee Milton L.
Published: May 2005

The application of mass spectrometry in the negative ion mode with capillary column supercritical fluid chromatography is described. The supercritical fluid chromatography mobile phase (CO2) was used as the primary reagent gas to generate thermalized electrons and reagent anions (such as O− and CO2−). When trace amounts of CH4 or NH3 gas were also introduced into the chemical ionization source, the mass spectrometer sensitivity was increased. Detection limits (S/N = 5) for heptachlor were determined to be 20 pg and 200 fg for full scan and selected ion monitoring modes, respectively. Mass spectra of a cyclic peptide, valinomycin, obtained with these mixed reagents (CH4 + CO2 and NH3 + CO2) gave the molecular anion at m/z 1110 as the most abundant ion and additional fragment ions that yielded peptide sequence information.
Evaluation of injection systems for open tubular liquid chromatography
Authors: Claessens Henk A. , Burcinova Andrea , Cramers Carel A. , Mussche Philippe , van Tilburg Chris C. E.
Published: May 2005

The main advantages of open tubular liquid chromatography (OTLC) over conventional packed‐column liquid chromatography are the gain in resolution and the increased permeability. At present the reproducible preparation of narrow‐bore columns and the lack of suitable commercial chromatographic equipment delay the development of OTLC. There are stringent requirements for injectors and detectors for OTLC with respect to their volumes, geometry, and contributions to the total band broadening. In this work some properties of two different sampling systems for OTLC were studied with respect to the accuracy and repeatability of the injected volumes. An approach is presented and discussed to determine the profile factors of these injection systems.
Detection limits of an ion mobility detector after capillary gas chromatography
Authors: St. Louis Robert H. , Siems William F. , Hill Herbert H.
Published: May 2005

A method for setting gating parameters is presented that maximizes response in ion mobility detection following capillary gas chromatography. The method requires knowledge of the drift times of the product ion or ions of interest and the drift times of the reactant ions. These values are obtainable from ion mobility spectra captured after capillary gas chromatography.

The capillary insertion distance into the ion source and the presence or absence of an aperture grid were also found to have considerable effect on chromatographic response. Under optimized conditions, minimum detectable limits of <1 fmol/s are reported for tributylamine, phenyl sulfide, and tributyl phosphate. These values demonstrate significant improvements over reported detection limits of organics by the flame ionization detector and sulfur‐containing species by the flame photometric detector. The values show slight improvement over those reported for detection of nitrogen and are comparable to those reported for detection of phosphorus‐containing species by the thermionization detector.
Metal‐element‐selective detection in packed microcolumn supercritical fluid chromatography combined with inductively coupled plasma atomic emission spectrometry
Authors: Fujimoto Chuzo , Yoshida Hiroyuki , Jinno Kiyokatsu
Published: May 2005

An interfacing technique between packed‐microcolumn (0.5‐mm i.d.) supercritical fluid chromatography and inductively coupled plasma atomic emission spectrometry was investigated. The loading limit of carbon dioxide gas into the plasma system was determined, and the results suggest that the detection system cannot be used for conventional 4.6‐mm i.d. columns. The potential of 0.5‐mm i.d. microcolumns was studied with respect to quantitation and use with unconventional elution modes such as modifier addition and step pressure programming. An analysis of ferrocenes and acetylacetonates was used to evaluate the total system performance.
Ion mobility detection following liquid chromatographic separation
Authors: McMinn Dennis G. , Kinzer Jeffery A. , Shumate Christopher B. , Siems William F. , Hill Herbert H.
Published: May 2005

Coronaspray ion mobility spectrometry was used in sample detection following reversed‐phase liquid chromatographic separation. Samples were introduced by coronaspray using a fused silica transfer line that was inserted through a stainless steel needle. Ion mobility spectra and chromatographic responses via monitoring of reactant‐ion depletion in the software second gate mode were shown for esters of para‐hydroxy benzoic acid, isomers of nitroaniline, and a mixture of acetaminophen, caffeine, and phenacetin.
COLOC‐S: A modified COLOC sequence for selective long‐range X‐H correlation 2D NMR spectroscopy
Authors: Krishnamurthy V. V. , Casida John E.
Published: May 2005

The COLOC‐S pulse sequence (a modification of COLOC) provides rapid and selective long‐range correlation 2D NMR spectra. It combines the advantages of the COLOC and Freeman sequences. This modification is analysed in terms of the Product Operator Formalism, and its application is illustrated by spectral peak assignments of two insecticides, ryanodine and 1R, cis‐phenothrin.
Application of two‐dimensional dipolar exchange spectroscopy with multiple mixing periods
Authors: Meyerhoff Dieter J. , Nunlist Rudi , O'Connell John F.
Published: May 2005

A NOESY‐type experiment with multiple mixing periods and acquisitions within a single pulse sequence was used to obtain a complete NOE correlation map of a small organic molecule. Incorporating multiple mixing periods and acquisitions into a single sequence can eliminate the need for repeating NOESY experiments with different mixing periods to observe dipolar exchange of considerably different rates or to determine exchange rates. The sequence has been applied to the molecular structure elucidation of cis‐8a‐vinyloctahydro‐3H‐2‐benzopyran‐3,7‐dione, a small organic molecule where the use of a single mixing period does not reveal all protons undergoing dipolar exchange.
Time‐resolved EPR studies of covalently linked porphyrin—crown ether—quinones, dissolved in liquid crystals
Authors: Batchelor Stephen N. , Sun Licheng , Möbius Klaus , Kurreck Harry
Published: May 2005

Time‐resolved EPR spectra are reported for photoexcited porphyrin—quinones with butylene and cis‐ or trans‐ cyclohexylene spacers between porphyrin donors and crown ether—quinone acceptors. In the nematic phases of liquid crystals, polarized triplet EPR spectra of the porphyrin moiety could be observed at early delay times (0.1–0.6 μs) after laser flash irradiation. At later delay times (1–2 μs) the triplet EPR spectra of the charge‐separated radical pair state, created by intramolecular electron transfer from the porphyrin donor to the crown ether quinone acceptor, could be detected. The similarity of the zero‐field splitting parameters D of the cyclohexylene‐ and butylene‐linked compounds shows that the radical pair of the flexible butylene‐linked compound is in a stretched conformation. However, longer laser irradiation of the species with the flexible bridge results in the formation of a novel triplet radical pair species with a shorter porphyrin—quinone separation indicating a photoinduced backfolding of the quinone over the porphyrin plane. Comparison of the cis‐ and trans‐cyclohexylene‐linked compounds reveals a distortion of the cyclohexylene spacer in the cis compound.
Magnetic characterization of the geometry and chemistry of small metal clusters
Authors: Mile Brynmor , Sillman Philip D.
Published: May 2005

The application of electron paramagnetic resonance (EPR) spectroscopy in determining the geometric and electronic structures of small naked clusters, Mn, of the alkali and coinage metals (n < 9) is assessed. The EPR spectra and the paramagnetic parameters derived therefrom provide stringent tests of quantitative molecular orbital calculations. Perturbations of the cluster shape by interaction with substrate molecules are readily detected and have a bearing on the dynamic nature of the active sites of heterogeneous catalysts. Previous studies of the metal trimers in hydrocarbon matrices are extended to the preparation of an unusual acute Na3 cluster associated with water and the heteronuclear clusters Na2Li and Au2Ag. Both adopt static obtuse 2B2 geometries and show no fluxionality, in contrast to the homonuclear pseudo‐rotating Jahn—Teller clusters Li3 and Na3. There is a reversal in paramagnetic parameters in the series Cu3, Ag3, Au3 which is due in part to the emergence of relativistic effects because of the high charge on the gold nucleus. The first ENDOR spectrum is reported of a metal cluster Li3, the parameters fitting exactly those determined from the more complex EPR spectrum of Li3. A new heteronuclear septameric species, Na2K5, has been examined which has the pentagonal bipyramidal structure seen for homonuclear septamer clusters. There is an unpaired spin density of 0.41 on the apical sodium nuclei with only 0.004 at the basal potassium nuclei.
EPR and ENDOR characterization of semiquinone anion radicals related to photosynthesis
Authors: MacMillan Fraser , Lendzian Friedhelm , Lubitz Wolfgang
Published: May 2005

EPR and ENDOR experiments were performed on the radical anions of 1,4‐benzoquinone, 2,3‐dimethyl‐1,4‐benzoquinone, 2,3,5,6‐tetramethyl‐1,4‐benzoquinone, 2,3‐dimethyl‐5‐ethyl‐1,4‐benzoquinone, plastoquinone‐1, plastoquinone‐9 and ubiquinone‐10. In liquid solutions the isotropic hyperfine coupling constants could be determined. In the frozen state hyperfine tensors for α‐protons and the freely rotating methyl groups were measured whereas other β‐protons (CH2) were broadened beyond detection probably caused by several superimposed chain conformations. In the immobilized radicals proton hyperfine couplings of hydrogen bonds formed between the alcoholic solvent and the CO groups of the quinones could be determined by experiments in protonated and deuterated solvents. Two different types of strong hydrogen bonds exist in these systems: in‐plane with aiso > 0 and out‐of‐plane with aiso ≈︁ 0. The latter type is observed if substituents at both carbons adjacent to the CO groups force the hydrogen bond out of the molecular plane. By use of the point‐dipole model and oxygen spin densities obtained from 17O hyperfine couplings, hydrogen bond lengths could be determined from the measured dipolar proton hyperfine tensors. These findings are very important for the binding and function of quinones in biological systems such as the photosynthetic reaction centres of plants and bacteria.
Electron paramagnetic resonance and Mössbauer studies of metal chelation by adriamycin
Authors: Zweier Jay L. , Levy Abraham
Published: May 2005

EPR and Mössbauer studies demonstrate that iron chelation by adriamycin is complex, with several different chelation structures. At physiological pH in aqueous solution, three different EPR spectra are observed: a spectrum at g = 4.2 of Fe3+ in a rhombic crystal field (type 1); a spectrum at g = 2.01 with symmetric Gaussian lineshape linewidth 225 G (1 G = 10−4 T), suggestive of Fe3+ bound in an octahedral crystal field (type 2); and a broad spectrum centered at g = 2.0 suggestive of ferromagnetically coupled Fe3+ (type 3). The type 1 and 2 spectra are observed at adriamycin/Fe3+ ratios >4, the type 3 spectrum is observed at ratios <4 and at ratios <2 an increasing amount of Fe3+ gives rise to EPR silent iron(III) hydroxide polymers. At 4 K the type 1 and 2 complexes exhibit a broad doublet Mössbauer signal with an isomer shift δ = 0.56 (1) mm s−1 and quadrupole splitting δEQ = 0.74 (1) mm s−1. The type 3 complex gives rise to a sextet signal with isomer shift ΔEq = 0.47 (1) mm s−1 and hyperfine splitting HF = 476 (1) kG with exhibits superparamagnetic relaxation behavior with a blocking temperature of 23 K, consistent with a microcrystal size of 25 Å. Cu2+ binds to adriamycin at adriamycin/Cu2+ ratios >4:1 giving rise to an EPR spectrum with axial symmetry g∥ = 2.26, g⟂ = 2.066, A∥ = 188 G, while 2:1 complexes exhibit a single Gaussian line at g = 2.09 indicative of exchange‐coupled Cu2+. The exchange‐coupled Cu2+ and ferromagnetically coupled Fe3+ complexes can be explained by the formation of stacked 2:1 adriamycin‐metal polymers. On titration of adriamycin with Fe3+‐nitrilotriacetate a different spectrum is observed at g = 4.3 and its intensity plateaus at an adriamycin/iron ratio of 2. The iron adriamycin complexes cycle to reduce molecular oxygen and this cycle has been hypothesized to be a mechanism mediating the therapeutic and toxic effects of the drug. Both EPR and Mössbauer experiments demonstrate that the type 1 and 2 chelates reduce their Fe3+ to Fe2+ while the type 3 chelate does not. Therefore, the stoichiometry and method of complex preparation can profoundly effect the properties of these complexes.
Pharmacological compartment viscosity and polarity measured with very low‐frequency EPR in tumors of living animals
Authors: Halpern Howard J. , Chandramouli G. V. R. , Yu Cheng , Peric Miroslav , Barth Eugene D. , Teicher Beverly A. , Grdina David
Published: May 2005

Quantitative measurements of the viscosity of a non‐vascular pharmacological compartment in a living animal are presented. Using novel, very low‐frequency electron paramagnetic resonance spectroscopy, capable of measurements in humans, novel analytical techniques and partially deuterated spin probes, the viscosity of the body water of murine fibrosarcomas implanted in the leg of a living animal were measured. The average viscosity was 1.9 ± 0.2 cP. Variation of the viscosity with tumor size and histology did not appear to be significant.
Rotational isomerism—XII Rotamer energies and 3JHF and 4JHH couplings in 1‐chloro‐2‐bromo‐2‐fluoropropane (1)
Authors: Abraham R. J. , Oliver W. L.
Published: May 2005

The complete analysis of the NMR spectrum of CH2Cl.CFBr.CH3 in CCl4 and acetone is given. The long range 4JHH couplings in this molecule differ considerably and surprisingly are both positive. An analysis of the solvent dependence of the couplings enables the rotamer couplings and energies to be obtained. The rotamer energies and their variation with solvent are in accord with quantitative predictions and results from similar halogenated ethanes. The values of the 4JHH couplings can be rationalised in terms of substituent electronegativity effects.
Nuclear magnetic resonance studies of hydrazyl radicals
Authors: Sagdeev R. Z. , Molin Yu. N. , Koryakov V. I. , Cheerkov A. K. , Matevosyan R. O.
Published: May 2005

A study of the nuclear magnetic resonance spectra of six hydrazyl radicals in solution, including α,α′‐diphenyl‐β‐picryl‐hydrazyl (DPPH), has been carried out. From the values of the paramagnetic shifts the constants (αH) of hyperfine coupling with the protons were found. For DPPH these have the following values:
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On the basis of the analysis of the hyperfine constants a conclusion is drawn concerning the substantial role of σ‐electron spin density delocalization in aromatic rings. The geometric structure of radicals investigated is also discussed in the paper.
NMR‐untersuchungen an piperidinen—III. 1H‐messungen an alkylpiperidinen
Authors: Wendisch Detlef , Reiff Helmut , Schubart Rüdiger
Published: May 2005

Es werden die 1H‐220 MHz‐Spektren von verschiedenen Alkylpiperidinen beschrieben. Alle Protonen des Ringes Können weitgehend zugeordnet werden. Die Effekte von N‐Methyl‐ und C‐Methylgruppen auf benachbarte Ringprotonen werden eingehend diskutiert.
Der Einfluss des anomer verknüpften Adeninrestes auf die 13C‐chemischen Verschiebungen von Pyranosen
Authors: Voelter Wolfgang , Breitmaier Eberhard
Published: May 2005

Der Einfluß des anomer verknüpften Adeninrestes auf die 13C‐chemischen Verschiebungen von Aldopyranosen wird für eine Reihe von Pyranosyladeninen diskutiert. Anomere Kohlenstoffatome mit axial verknüpftem Heterocyclus absorbieren stets bei höherem Feld als entsprechende mit äquatorial orientiertem Adenin. Diese Regel kann zur Bestimmung der Pyranosekonformation verwendet werden. Wird die anomere Hydroxylgruppe durch einen Adeninrest ersetzt, dann verschiebt sich die Resonanz von C‐5 des Pyranoserestes nach tieferem Feld.
Sexually dimorphic mechanosensitive swimmeret sensilla affect abdominal posture in the lobster
Authors: Kotak Vibhakar C. , Page Charles H.
Published: May 2005

The sensilla on the male and female second swimmerets are sexually dimorphic. Female swimmerets contain many long “smooth hairs” (long simple setae) on the coxa and rami. The endopodite of the male swimmeret has an accessory lobe covered with short “bristly spines” (serrate setae). In both sexes the swimmeret rami are lined by “feathered hairs” (plumose setae). The influence of mechanosensory stimulation of these sensilla upon abdominal tonic motor activity was analyzed in an in vitro swimmeret‐nerve cord preparation. Movement of several clusters of smooth hairs produced an abdominal extension program by exciting the flexor inhibitor f5, inhibiting the flexor excitors, and activating several extensors. Stimulation of the male bristly spines excited the medium‐sized flexor excitors f3 and f4. In both sexes the feathered hairs did not generate any response to mechanical stimulation. We infer that in nongravid females the smooth hairs are involved in receiving mechanosensitive cues to support abdominal extension. Bristly spines may contribute to postural adjustments that assist mating. The long latencies of these responses and their propagation to adjacent ganglia suggest that they are mediated by postural interneurons rather than by direct afferent terminations on postural motoneurons.
Differential Pavlovian conditioning in the mollusc Pleurobranchaea
Authors: Mpitsos George J. , Cohan Christopher S.
Published: May 2005

The present differential Pavlovian conditioning experiments on the sea slug Pleurobranchaea californica extend conditioning described in a preceding paper and provide the conditioning foundation for studies reported in another accompanying paper comparing learned behavior in whole animals with the behavior and motor patterns of electrophysiological preparations. All animals received two appetitive‐conditioned stimuli (CSs), one derived from beer (Sbr) and the other derived from squid muscle (Ssq), in different temporal relationships to an electric shock unconditioned stimulus (UCS). Two groups of animals were run concurrently. One group (n = 19) received Sbr as the CS+ in close temporal pairing with the UCS, and Ssq as the CS− explicitly unpaired with the UCS (Sbr+/Ssq−). The second group (n = 20) received the opposite contingencies (Sbr−/Ssq+). All animals received only one day of conditioning involving 5 trials with an intertrial interval of 2 h. There were two replicate experiments, each involving about half of the total n, and each yielding similar results as the sum we report here. Before conditioning, animals exhibited feeding behavior (extension of the proboscis and bite‐strike responses) to both stimuli at similar low thresholds. Conditioning produced long‐term behavioral changes in all animals throughout the 4.5‐day postconditioning observation period. However, only the Sbr+/Ssq− animals consistently exhibited the appropriate differentially conditioned food‐aversion behavior which consisted of strong withdrawal and high‐threshold feeding responses to Sbr, and low‐threshold feeding responses to Ssq. We discuss the possibility that such differences between Sbr+/Ssq − and Sbr−/Ssq+ conditioning may arise either from inherent differences in the responses of the animals to Sbr and Ssq, or, as seems more likely to us, from training and testing effects produced by differences in the compositions of the two stimuli.
The serotoninergic system in Cryptomphalus aspersa. Immunocytochemical study with an anti‐5‐HT antiserum
Authors: Flores Vladimir , Brusco Alicia , Saavedra Jorge Pecci
Published: May 2005

This immunocytochemical study of 5‐HT neurons and fibers in the nervous system of C. aspersa corroborate previous findings and describe new 5‐HT neurons and their connections, mainly between the central nervous system and the tentacular sensory organs. We found a number of networks, fascicles, and neurons that show constant and symmetrical location. Three networks were found at the tip of the posterior tentacle: (1) underlying the olfactory epithelium, (2) in the neuropil of the tentacular ganglion (TG), and (3) in the ocular capsule. The TG also contains a ventral 5‐HT fascicle. A group of 30–40 serotoninergic fibers run through the tentacular connective from the postcerebrum to the tentacular ganglion. This 5‐HT fascicle has a lateral position in the postcerebrum (lateral fascicle of the postcerebrum) and a subcortical location in the procerebrum (subcortical fascicle of the procerebrum). The optic nerve also has a small group of 5‐HT fibers. Seven serotoninergic neurons were found in each cerebral ganglion: two giant neurons, one medium‐sized, and four small neurons. Three different types of fascicles are in the postcerebrum: (1) fascicles proceeding from the suboesophageal connectives, (2) a lateral fascicle, and (3) a commisural fascicle. Each cerebral ganglion region (pro‐, meso‐ and postcerebrum) has a 5‐HT network with a particular pattern of distribution and morphology. The suboesophageal ganglia show the highest concentration of 5‐HT neurons (large, medium‐size, and small neurons).
The kinematics of turnaround and retrograde axonal transport
Authors: Snyder R. E.
Published: May 2005

Rapid axonal transport of a pulse of 35S‐methionine‐labelled material was studied in vitro in the sensory neurons of amphibian sciatic nerve using a position‐sensitive detector. For 10 nerves studied at 23.0 ± 0.2°C it was found that a pulse moved in the anterograde direction characterized by front edge, peak, and trailing edge transport rates of (mm/d) 180.8 ± 2.2 (±SEM), 176.6 ± 2.3, and 153.7 ± 3.0, respectively. Following its arrival at a distal ligature, a smaller pulse was observed to move in the retrograde direction characterized by front edge and peak transport rates of 158.0 ± 7.3 and 110.3 ± 3.5, respectively, indicating that retrograde transport proceeds at a rate of 0.88 ± 0.04 that of anterograde. The retrograde pulse was observed to disperse at a rate greater than the anterograde. Reversal of radiolabel at the distal ligature began 1.49 ± 0.15 h following arrival of the first radiolabel. Considerable variation was seen between preparations in the way radiolabel accumulated in the end (ligature) regions of the nerve. Although a retrograde pulse was seen in all preparations, in 7 of 10 preparations there was no evidence of this pulse accumulating within less than 2–3 mm of a proximal ligature; however, accumulation was observed within less than 5 mm in all preparations.