bluuebunny/crossref_metadata_2025_split huggingface dataset:
Para/autocrine regulation of estrogen receptors in hippocampal neurons
Authors: Prange‐Kiel Janine , Wehrenberg Uwe , Jarry Hubertus , Rune Gabriele M. 
Published: March 2003

AbstractPrevious studies have shown that estrogens, originating from ovaries, have a wide variety of estrogen receptor (ER)‐mediated effects in the hippocampus. In the present study, we have investigated whether estrogens, which are synthesized in the hippocampus, could induce these effects as well. As a parameter, we used ER expression in response to estrogen synthesis, because estrogen receptors are ligand‐inducible transcription factors. The experiments were carried out with cultures of isolated adult rat hippocampal cells, which contained about 95% neurons and about 5% oligodendrocytes in serum‐free and steroid‐free medium. Hippocampal neurons express both estrogen receptor isoforms (ERα and ERβ), as shown by reverse transcription‐polymerase chain reaction (RT‐PCR) and in situ hybridization. The release of estrogens by hippocampal neurons was quantified by radioimmunoassay (RIA). The ER isoforms (α and β) were studied by semiquantitative immunocytochemical image analysis. Hippocampal cells precultured for 4 days were found to synthesize 17β‐estradiol for the next 8 days. This synthesis was completely inhibited by letrozol, an aromatase inhibitor. Inhibition of estrogen synthesis by letrozol induced a significant decrease in ERα expression, but an increase in ERβ. As a control, supplementation of the medium with 17β‐estradiol resulted in a significant increase of ERα expression, whereas ERβ was downregulated. Our findings provide evidence for a de novo synthesis of estrogens in the hippocampus, differential regulation of estrogen receptor isoforms by estrogen and consequently for a para/autocrine loop of estrogen action in the hippocampus. Hippocampus 2003;13:226–234. © 2003 Wiley‐Liss, Inc.
Hippocampal damage equally impairs memory for single items and memory for conjunctions
Authors: Stark Craig E.L. , Squire Larry R. 
Published: March 2003

AbstractIn a prior study of continuous recognition performance, data were reported in support of the hypothesis that the hippocampus is not needed to remember the individual components of a stimulus but is important for remembering associations between its components (Kroll et al. 1996. J Mem Lang 35:176–196). Patients with left hippocampal damage were able to endorse recently encountered words and to reject novel words, as well as disyllabic words in which one of the syllables had been previously encountered. However, they failed to reject words in which both syllables had been encountered independently in different words. We present data from five experiments designed to examine this finding in more detail. In each experiment, five patients with bilateral hippocampal damage and eight controls were tested using the same protocol as Kroll et al. (1996). On each trial, a two‐component stimulus was presented. Stimuli could be entirely novel, novel with one previously encountered (repeated) component, novel but with both components repeated, or a true repetition. The first experiment was a direct replication using the same disyllabic words as Kroll et al. (1996). The second experiment used pseudo‐words, constructed of two monosyllabic words (e.g., jambark). The third experiment used the same pairs of monosyllabic words, but presented separately on the screen to encourage participants to treat each component independently. The fourth experiment used pairs of objects, and the fifth experiment used face–house pairs. In all five experiments, patients with hippocampal damage exhibited impaired recognition memory. The impairment extended across all trial types with no evidence that hippocampal damage selectively (or disproportionately) impaired the associative or conjunctive component of memory. We discuss our findings in the light of the work by Kroll et al. (1996) and other recent neuropsychological, electrophysiological, and neuroimaging studies of hippocampal function and single‐item and associative memory. Hippocampus 2003;13:281–292. © 2003 Wiley‐Liss, Inc.
Phosphorus Pentachloride (PCl5) Mediated Synthesis of Tetraarylporphyrins
Authors: Sharghi Hashem , Nejad Alireza Hassani 
Published: March 2003

AbstractA new synthesis of porphyrins from pyrrole and substituted benzaldehydes is described, with PCl5 as catalyst. Aromatic aldehydes condense irreversibly with pyrrole in the presence of this catalyst, and aerobic oxidation of porphyrinogen provides functionalized porphyrins in yields of 20–65%.
Chemical Transformations of Phyllocladane (=13β‐Kaurane) Diterpenoids
Authors: Liu Gui , Müller Ralph , Rüedi Peter 
Published: March 2003

AbstractEarlier phytochemical work on Plectranthus ambiguus (Lamiaceae) afforded a series of tetracyclic phyllocladane‐type (=13β‐kaurane) diterpenoids (see 1a–f). In the course of investigations concerning the reaction behavior of this rare natural‐products, a new constituent of P. ambiguus was isolated, (2S,3R,16R)‐phyllocladane‐2,3,16,17‐tetrol 2,3‐diacetate (1g), and another eighteen new phyllocladanes were prepared by chemical transformations and characterized. The main constituent 1b of P. ambiguus was chemically transformed to the known natural diterpenoid calliterpenone (=(16R)‐16,17‐dihydroxyphyllocladan‐3‐one; 2) thus unambiguously establishing its structure (Scheme 1). Epimerization at C(16) via the epoxy derivative 20 yielded 16‐epicalliterpenone (21), 17‐hydroxyphylloclad‐15‐ene‐3‐one (22), and (16R)‐3‐oxophyllocladan‐17‐al (23) (Scheme 6). Comparing this reaction sequence with the corresponding one starting from diastereoisomeric (16R)‐16,17‐dihydroxy‐ent‐kauran‐3‐one (=abbeokutone; 27) showed basically the same outcome (Scheme 7). Furthermore, three new C(16)‐substituted ent‐kauran‐3‐ones were characterized.Reliable spectroscopic arguments for the determination of the configuration at C(16) in phyllocladanes and kauranes as well as for the differentiation of the diastereoisomeric skeletons are presented.
An Unexpected (3→2)‐Hydride Shift in Phyllocladane (=13β‐Kaurane) Diterpenoids and in Related Trimethyl‐Substituted Bi‐ and Tricyclic Compounds
Authors: Müller Ralph , Rüedi Peter 
Published: March 2003

AbstractThe conversion of 2α,3α‐dioxy‐substituted phyllocladane derivatives into the corresponding 3‐ketone proceeds in an unexpected manner: Depending on the reaction conditions, the corresponding 3β‐hydroxy‐substituted compound is formed almost quantitatively, or the desired ketone can be isolated directly (see preceding paper). The reaction mechanism is now disclosed to be a stereospecific C(3)→C(2)‐hydride shift by investigating the reactions of the synthesized (±)‐trans‐decalin‐type (trans‐1,5,5‐trimethylbicyclo[4.4.0]decanes) and (±)‐podocarpane‐type (trans‐1,2,3,4,4a,9,10,10a‐octahydro‐1,1,4a‐trimethylphenanthrenes) model compounds 25 and 35 and of their D‐labeled isomers 25′ and 35′ (Scheme 6). The latter afforded the corresponding 3β‐hydroxy (2β‐D)‐derivatives 38 and 39 as well as the (2β‐D)‐3‐ketones of the general type 5b′ (e.g., 36′), thus evidencing a suprafacial (C3)→C(2)‐deuteride shift. This reaction mechanism seems to be a general feature of such 3α,4α‐dioxy‐substituted 1,5,5‐trimethylbicyclo[4.4.0]decane congeners.
The Macrocyclic Spermidine Alkaloid (−)‐(S)‐Neoperiphylline: Revision of the Structure Based on the Total Synthesis
Authors: Sergeyev Sergey A. , Hesse Manfred 
Published: March 2003

AbstractThe total synthesis of the two isomeric macrocyclic enamides 2 and 17 is described. The precursor 14 was synthesized by means of template‐assisted macrocyclization (Scheme 2). Isomerization of 14 in the presence of [Fe(CO)5] gave 2 and 17 (Scheme 4). Structure 2 was previously assigned to the alkaloid neoperiphylline. However, the synthetic 2 showed completely different properties compared to the earlier described data of the natural compound. Surprisingly, analytical data of the second synthetic product 17 were very close to those of the natural neoperiphylline. We conclude that the previously assigned structure of neoperiphylline is erroneous and should be corrected to that of (−)‐(4S,12Z)‐4‐phenyl‐9‐[(2E)‐3‐phenylprop‐2‐enoyl]‐1,5,9‐triazacyclotridec‐12‐en‐2‐one (17).
Understanding referral from primary care clinics in rural Kenya: using health information systems to prioritize health services
Authors: Macintyre Kate , Lochigan Mohamed , Letipila Frederick 
Published: March 2003

AbstractThis study analyses the referral patterns of patients, over time, from primary care to secondary or tertiary level facilities in rural Africa. The data come from a health information system of a non‐governmental organization with a decade of experience in health services delivery in Samburu District, Kenya. The differential referral patterns from two communities are examined in some detail to shed more light on the meaning of a ‘referral rate’ in this context. First, referral rates over time for two clinics are calculated and compared. These quantitative data, obtained from monthly reports from 1989 to 1997, are interpreted in the light of qualitative data obtained from interviews with community health workers, nurses and members of the communities. The main differences in referral between these ostensibly similar communities are for malaria, trauma and anaemia. Social, environmental and specific health services factors are used to explain these differences. We demonstrate that basic information from health information systems, which tell us little on their own because referral in this context is a rare event, can be combined with local knowledge from the community to provide evidence for health managers to set priorities for public health and clinical interventions. Copyright © 2003 John Wiley & Sons, Ltd.
Organizing health care within political turmoil: the Palestinian case
Authors: Hamdan Motasem , Defever Mia , Abdeen Ziad 
Published: March 2003

AbstractPalestinians were given control over their own health services in late 1994. Since then they have been facing the challenge of reorganizing disordered health services into a cohesive, regulated and sustainable health care system.This paper focuses on the experience of organizing health care during political instability. It considers the ways that health care is currently provided and funded in the Palestinian Territories. The patterns of accessibility to health care services in terms of insurance coverage and provision (physical allocation) of services are discussed. Finally, the major health care policy changes in this transitional period are examined. Copyright © 2003 John Wiley & Sons, Ltd.
Influence of macroinvertebrates on physico‐chemical and microbial processes in hyporheic sediments
Authors: Mermillod‐Blondin Florian , Gaudet Jean‐Paul , Gérino Magali , Desrosiers Gaston , Creuzé des Châtelliers Michel 
Published: March 2003

AbstractThe objective of this study was to measure the effects of invertebrates on the physical characteristics and microbial processes in hyporheic sediments. We investigated the impacts of an assemblage of three taxa (asellids, chironomid larvae, and tubificid worms) on sediment distribution, water fluxes, sediment organic carbon, biofilm (attached bacteria) characteristics, and O2, dissolved organic carbon NO3−, NO2−, and NH4+ concentrations in slow filtration sand–gravel columns. The results showed that invertebrates clearly modified the distribution of particles in the sediment column, probably because of the structures (tubes, macropores, and faecal pellets) produced by the three taxa in the sediment. Our assessment of water fluxes indicated that invertebrate activities led to an increase in the porosity of the sediment columns. In addition, aerobic (O2 consumption) and anaerobic (denitrification and fermentative decomposition of organic matter) microbial processes occurring in the sediment were stimulated in the presence of invertebrates. Finally, the present study demonstrates that invertebrates can act as ecosystem engineers in heterogeneous sediments that are under the influence of an advective flux of water. The solute residence time increased in columns containing the faunal assemblage. Micro‐organisms used more dissolved organic matter and nutrients in the presence of invertebrates because invertebrate activities increased the contact between the biofilm and water. We conclude that engineering by invertebrates in natural conditions modifies characteristics of the hyporheic zone and thereby enhances both the porosity of the sediment and the solute transport across the benthic interface. Copyright © 2002 John Wiley & Sons, Ltd.
Stimulation of bone formation with an in situ setting tricalcium phosphate/rhBMP‐2 composite in rats
Authors: Niedhart Christopher , Maus Uwe , Redmann Eva , Schmidt‐Rohlfing Bernhard , Niethard Fritz U. , Siebert Christian H. 
Published: March 2003

AbstractThe aim of the study was to determine bone‐regenerative effects of an in situ setting tricalcium phosphate (TCP) cement combined with rhBMP‐2 and to compare it with autologous bone graft. A trepanation defect of 1.5 mm in the femur diaphysis of Sprague–Dawley rats was filled with an in situ setting TCP cement combined with 0, 0.25, 2.5, or 25 μg of rhBMP‐2, an autologous bone graft, or left empty. The rats were euthanized after 1 and 3 weeks and examined by radiography, histology, histomorphometry, and bending tests. All TCP groups with or without BMP‐2 showed a good bony ingrowth with a close bone–cement contact. Histomorphometric analysis showed no increase of new bone formation in the defect, but a dose‐dependent increase in callus formation with a maximum at 25 μg of rhBMP‐2. As shown with intravital fluorochrome staining, new bone formation started earlier using rhBMP‐2. Bone strength, measured in a three‐point bending test and expressed in percentage of the contralateral healthy femur, was 75% for TCP + 25 μg rhBMP‐2, 44% for TCP + 2.5 μg rhBMP‐2, and 34% for autologous bone graft. TCP particles were detectable in all groups after 3 weeks. Callus formation and bending strength of the TCP + 25 μg rhBMP‐2 group was superior to autologous bone graft. So TCP/rhBMP‐2 composites may prove to be an effective substitute for autologous bone grafts. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 65A: 17–23, 2003
Macrophages at the skeletal tissue–device interface of loosened prosthetic devices express bone‐related genes and their products
Authors: Zreiqat H. , Kumar R. K. , Markovic B. , Zicat B. , Howlett C. R. 
Published: March 2003

AbstractAseptic loosening of prosthetic arthroplasty is the most common reason for implant failure in adult orthopaedic reconstruction. At the interface of aseptic loosened prostheses, there is an abundance of particle‐activated macrophages and other inflammatory cells. The role of these particle‐laden macrophages in the osteogenic arm of the remodeling skeleton in this pathological condition is poorly understood. Molecular signaling by mesenchymal cells and mononuclear inflammatory cells residing in the interfacial tissues between bone and cement or prosthetic material of aseptically loosened joint prostheses was studied using in situ hybridization and immunohistochemical techniques. We found that a range of collagenous and noncollagenous matrix proteins, including osteopontin, osteocalcin, bone sialoprotein, and type I collagen, were produced in the periprosthetic tissue by foamy macrophages, as well as nearby osteogenic cells. The former accumulated in profusion in the three zones of interfacial tissues: pseudomembranous, fibrous, and osseous. Spindle mesenchymal cells in the fibrous zone failed to express any of the osteogenic mRNAs or proteins sought. The expression of bone‐related genes and proteins by foamy macrophages at the interface of an aseptic loosened prosthesis may contribute to the disturbance of bone remodeling at this site. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 65A: 109–117, 2003
Cell attachment and growth on films prepared from poly(depsipeptide‐co‐lactide) having various functional groups
Authors: Ohya Yuichi , Matsunami Hideaki , Yamabe Etsuro , Ouchi Tatsuro 
Published: March 2003

AbstractIn tissue engineering related to the regeneration of damaged or lost tissue, excellent biodegradable materials are desired as temporary scaffolds to support cell growth and then disappear with the progress of tissue regeneration. We previously synthesized biodegradable poly(depsipeptide‐co‐lactide), poly[(Glc‐Asp)‐co‐LA], and poly[(Glc‐Lys)‐co‐LA] with reactive side‐chain groups. In this study, to evaluate the utility of these copolymers as functional scaffolds for tissue regeneration, the effects of reactive and ionic side‐chain groups on cell attachment and growth were investigated using copolymer films with various numbers of carboxyl or amino groups. Poly[(Glc‐Lys)‐co‐LA] and poly[(Glc‐Asp)‐co‐LA] films having appropriate positive or negative charges exhibited higher cell attachment ability than did poly‐L‐lactide. Good cell growth was observed on the copolymer films. During cell culture, the copolymer films exhibited higher degradation rates related to the depsipeptide content. Biodegradable polymer matrices with reactive surfaces for cell growth successfully were prepared using copolymers with various numbers of depsipeptide units. Varying the depsipeptide unit numbers in the copolymer could change the degradation rate of these matrices. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 65A: 79–88, 2003
Proanthocyanidin: A natural crosslinking reagent for stabilizing collagen matrices
Authors: Han Bo , Jaurequi Jason , Tang Bao Wei , Nimni Marcel E. 
Published: March 2003

AbstractWhile attempting to find a suitable crosslinking reagent for biopolymers, a naturally occurring proanthocyanidin (PA) obtained from grape seeds was selected to fix biological tissues. The cytotoxicity and crosslinking rate, reflected by the in vitro and in vivo degradation of fixed matrices has been studied. The shrinkage temperature of the fixed bovine pericardium increased from 66 to 86°C. A cytotoxicity assay using fibroblast cultures revealed that PA is ∼120 times less toxic than glutaraldehyde (GA), a currently used tissue stabilizer. In vitro degradation studies showed that fixed tissue was resistant to digestion by bacterial collagenase. Crosslinks between PA and tissues can be stabilized by decreasing the dielectric constant of the solution during storage. After subcutaneous implantation for periods ranging between 3 and 6 weeks, we found no apparent degradation of the GA‐ or PA‐fixed tissues, whereas fresh tissue controls rapidly disintegrated. Beyond 6 weeks PA crosslinks began to degrade. More fibroblasts migrated and proliferated inside the PA‐fixed implants compared with GA counterparts. Tissues crosslinked with PA manifested an enhanced collagen expression and deposition and did not calcify after implantation. GA, on the other hand, even after thorough rinsing continued to be cytotoxic, inhibited collagen synthesis and encouraged dystrophic calcification. Collagen matrices crosslinked with PA are expected to be of value in the design of matrices that will encourage cell ingrowth and proliferation, which are temporary in nature, and that are intended to regenerate or replace missing tissues, which can delay the biogradation of collagen. As such they should be of significant value in the emerging field of tissue engineering. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 65A: 118–124, 2003
Composition and in vitro biocompatibility of corroding tungsten coils
Authors: Peuster Matthias , Kaese Volker , Wuensch Gerold , von Schnakenburg Christian , Niemeyer Matthias , Fink Christoph , Haferkamp Heinz , Hausdorf Gerd 
Published: March 2003

AbstractThe purpose of the article is to evaluate composition and biocompatibility of corroding mechanically detachable spirals (MDS, Balt Extrusion, Montmorency, France). Analysis of the material composition of corroding MDS coils was assessed by inductively coupled plasma atomic emission spectroscopy, inductively coupled plasma mass spectroscopy, and wavelength‐dispersive x‐ray spectrometry. Toxicity assays were performed with human venous endothelial cells, venous smooth muscle cells and fibroblasts. The analyses of the MDS coils demonstrated a tungsten content of the dissolving MDS spirals of > 99.9 mas%. In vitro, human endothelial, vascular smooth muscle cells and fibroblasts were not adversely affected by markedly elevated tungsten concentrations (60,500 μg/l) after 12 days in the culture medium. The examined cells showed an extensive vital growth on the coil surface. Corrosion of tungsten coils leads to markedly elevated tungsten levels in the culture medium. However, growth and vitality of endothelial cells, fibroblasts, and vascular smooth muscle cells are not adversely affected by elevated tungsten concentrations. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 65B: 211–216, 2003
Human aldehyde dehydrogenases: Potential pathological, pharmacological, and toxicological impact
Authors: Sládek Norman E. 
Published: March 2003

AbstractAldehyde dehydrogenases catalyze the pyridine nucleotide‐dependent oxidation of aldehydes to acids. Seventeen enzymes are currently viewed as belonging to the human aldehyde dehydrogenase superfamily. Summarized herein, insofar as the information is available, are the structural composition, physical properties, tissue distribution, subcellular location, substrate specificity, and cofactor preference of each member of this superfamily. Also summarized are the chromosomal locations and organization of the genes that encode these enzymes and the biological consequences when enzyme activity is lost or substantially diminished. Broadly, aldehyde dehydrogenases can be categorized as critical for normal development and/or physiological homeostasis (1) even when the organism is in a friendly environment or (2) only when the organism finds itself in a hostile environment. The primary, if not sole, evolved raison d'être of first category aldehyde dehydrogenases appears to be to catalyze the biotransformation of a single endobiotic for which they are relatively specific and of which the resultant metabolite is essential to the organism. Most of the human aldehyde dehydrogenases for which the relevant information is available fall into this category. Second category aldehyde dehydrogenases are relatively substrate nonspecific and their evolved raison d'être seems to be to protect the organism from potentially harmful xenobiotics, specifically aldehydes or xenobiotics that give rise to aldehydes, by catalyzing their detoxification. Thus, the lack of a fully functional first category aldehyde dehydrogenase results in a gross pathological phenotype in the absence of any insult, whereas the lack of a functional second category aldehyde dehydrogenase is ordinarily of no consequence with respect to gross phenotype, but is of consequence in that regard when the organism is subjected to a relevant insult. © 2003 Wiley Periodicals, Inc. J Biochem Mol Toxicol 17:7–23, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.10057