bluuebunny/crossref_metadata_2025 huggingface dataset:
Blockage of methylcitrate cycle inhibits polyketide production in Aspergillus nidulans
Authors: Zhang Yong‐Qiang , Keller Nancy P.
Published: April 2004

Aspergillus nidulans produces the polyketide toxin sterigmatocystin (ST) of which the biosynthetic and pathway specific regulatory genes compose a stc gene cluster. A previous mutagenesis screen identified 23 mutants defective in production of ST. Five mutants constitute a single locus. Genetic complementation and sequencing analysis revealed the mutant locus to be mcsA encoding methylcitrate synthase that converts propionyl‐CoA to methylcitrate. Feeding downstream products of methylcitrate synthase, methylcitrate and pyruvate, did not restore ST production in mcsA mutants, indicating that loss of methylcitrate cycle products is not the cause of the ST defect. However, propionate, a precursor for propionyl‐CoA, inhibited ST production and induced transcription of mcsA in the wild type. Furthermore, propionate impaired formation of two polyketide spore pigments whereas overexpression of mcsA relieved inhibition of ST production by propionate. Transcription analyses revealed that disruption of mcsA did not affect expression of the specialized fatty acid synthase genes (stcJ and stcK) or polyketide synthase gene (stcA) required for formation of norsolorinic acid (NOR), the first stable intermediate in the ST biosynthetic pathway. Feeding studies showed that NOR but not hexanoic acid (the fatty acid produced by StcJ/StcK and primer unit of StcA) or malonate (source of the extender unit of StcA) restored ST production in the mcsA mutant. We hypothesize that excess buildup of propionyl‐CoA in mcsA mutants interferes with polyketide synthase activity.
The ShdA adhesin binds to the cationic cradle of the fibronectin13FnIII repeat module: evidence for molecular mimicry of heparin binding
Authors: Kingsley Robert A. , Keestra A. Marijke , De Zoete Marcel R. , Bäumler Andreas J.
Published: April 2004

Introduction ofSalmonella entericaserotype Typhimurium into food products results from its ability to persist in the intestine of healthy livestock by mechanisms that are poorly understood. The non‐fimbrial adhesin ShdA is a fibronectin binding protein required for persistent intestinal carriage ofS.Typhimurium. We further investigated the molecular mechanism of ShdA‐mediated intestinal persistence by determining the binding‐site of this receptor in fibronectin. Analysis of ShdA binding to fibronectin proteolytic fragments and to recombinant fibronectin fusion proteins identified the13FnIII repeat module of the Hep‐2 domain as the primary binding site for this adhesin. The13FnIII repeat module of fibronectin contains a cationic cradle formed by six basic residues (R6, R7, R9, R23, K25 and R54) that is a high affinity heparin‐binding site conserved among fibronectin sequences from frogs to man. Binding of ShdA to the13FnIII repeat module of fibronectin and to a second extracellular matrix protein, Collagen I, could be inhibited by heparin. Furthermore, binding of ShdA to the Hep‐2 domain was sensitive to the ionic buffer strength, suggesting that binding involved ionic interactions. We therefore determined whether amino acid substitutions of basic residues in the cationic cradle of the Hep‐2 domain that inhibit heparin binding also abrogate binding of ShdA. Combined substitution of R6S and R7S strongly reduced ShdA binding to13FnIII. These data suggest that ShdA binds the Hep‐2 domain of fibronectin by a mechanism that may mimic binding of the host polysaccharide heparin.
Genes governing swarming in Bacillus subtilis and evidence for a phase variation mechanism controlling surface motility
Authors: Kearns Daniel B. , Chu Frances , Rudner Rivka , Losick Richard
Published: April 2004

Undomesticated strains of Bacillus subtilis, but not laboratory strains, exhibit robust swarming motility on solid surfaces. The failure of laboratory strains to swarm is caused by a mutation in a gene (sfp) needed for surfactin synthesis and a mutation(s) in an additional unknown gene(s). Insertional mutagenesis of the undomesticated 3610 strain with the transposon mini‐Tn10 was carried out to discover genes needed for swarming but not swimming motility. Four such newly identified swarming genes are reported, three of which (swrA, swrB, and efp) had not been previously characterized and one of which (swrC) was known to play a role in resistance to the antibacterial effect of surfactin. Laboratory strains were found to harbour a frameshift mutation in the swrA gene. When corrected for the swrA mutation, as well as the mutation in sfp, laboratory strains regained the capacity to swarm and did so as robustly as the wild strain. The swrA mutation was an insertion of an A:T base pair in a homopolymeric stretch of eight A:T base pairs, and readily reverted to the wild type. These findings suggest that the swrA insertion and its reversion take place by slipped‐strand mispairing during DNA replication and that swarming motility is subject to phase variation.
The Pseudomonas siderophore quinolobactin is synthesized from xanthurenic acid, an intermediate of the kynurenine pathway
Authors: Matthijs Sandra , Baysse Christine , Koedam Nico , Tehrani Kourosh Abbaspour , Verheyden Lieve , Budzikiewicz Herbert , Schäfer Mathias , Hoorelbeke Bart , Meyer Jean‐Marie , De Greve Henri , Cornelis Pierre
Published: April 2004

To cope with iron deficiency fluorescent pseu‐domonads produce pyoverdines which are complex peptidic siderophores that very efficiently scavenge iron. In addition to pyoverdine some species also produce other siderophores. Recently, it was shown that Pseudomonas fluorescens ATCC 17400 pro‐duces the siderophore quinolobactin, an 8‐hydroxy‐4‐methoxy‐2‐quinoline carboxylic acid (Mossialos, D., Meyer, J.M., Budzikiewicz, H., Wolff, U., Koedam, N., Baysse, C., Anjaiah, V., and Cornelis, P. (2000) Appl Environ Microbiol 66: 487–492). The entire quinolobactin biosynthetic, transport and uptake gene cluster, consisting out of two operons comprising 12 open reading frames, was cloned and sequenced. Based on the genes present and physiological complementation assays a biosynthetic pathway for quinolobactin is proposed. Surprisingly, this pathway turned out to combine genes derived from the eukaryotic tryptophan‐xanthurenic acid branch of the kynurenine pathway and from the pathway for the biosynthesis of pyridine‐2,6‐bis(thiocarboxylic acid) from P. stutzeri, PDTC. These results clearly show the involvement of the tryptophan‐kynurenine‐xanthurenic acid pathway in the synthesis of an authentic quinoline siderophore.
Genetic evidence that the Vibrio cholerae monolayer is a distinct stage in biofilm development
Authors: Moorthy Sudha , Watnick Paula I.
Published: April 2004

Biofilm development is conceived as a developmental process in which free swimming cells attach to a surface, first transiently and then permanently, as a single layer. This monolayer of immobilized cells gives rise to larger cell clusters that eventually develop into the biofilm, a three‐dimensional structure consisting of large pillars of bacteria interspersed with water channels. Previous studies have shown that efficient development of the Vibrio cholerae biofilm requires a combination of pili, flagella and exopolysaccharide. Little is known, however, regarding the requirements for monolayer formation by wild‐type V. cholerae. In this work, we have isolated the wild‐type V. cholerae monolayer and demonstrated that the environmental signals, bacterial structures, and transcription profiles that induce and stabilize the monolayer state are unique. Cells in a monolayer are specialized to maintain their attachment to a surface. The surface itself activates mannose‐sensitive haemagglutinin type IV pilus (MSHA)‐mediated attachment, which is accompanied by repression of flagellar gene transcription. In contrast, cells in a biofilm are specialized to maintain intercellular contacts. Progression to this stage occurs when exopolysaccharide synthesis is induced by environmental monosaccharides. We propose a model for biofilm development in natural environments in which cells form a stable monolayer on a surface. As biotic surfaces are degraded with subsequent release of carbohydrates, the monolayer develops into a biofilm.
The histone‐like nucleoid structuring protein H‐NS represses the Escherichia coli bgl operon downstream of the promoter
Authors: Dole Sudhanshu , Nagarajavel V. , Schnetz Karin
Published: April 2004

Specificity of repression by the histone‐like nucleoid structuring protein and pleiotropic regulator, H‐NS, is exceptionally high in case of the Escherichia coli bgl (β‐glucoside) operon. Here we present evidence that H‐NS represses the operon at two levels. The binding of H‐NS to an upstream silencer results in an ∼threefold repression of the catabolite gene regulator protein (CRP) dependent bgl promoter. In addition, H‐NS binds to a silencer region located approximately 600–700 base pairs downstream of the promoter, within the coding region of first gene, bglG, resulting in a ∼sevenfold further decrease of expression. Repression by H‐NS at the downstream silencer requires termination factor Rho and is reduced by translation of the bglG mRNA, but is independent of the promoter. This suggests that H‐NS induces polarity of transcription by acting as a roadblock to the elongat‐ing RNA polymerase. The control of the bgl operon by H‐NS at two levels results in a highly specific repression.
Nuclear localization and interaction of RolB with plant 14‐3‐3 proteins correlates with induction of adventitious roots by the oncogene rolB
Authors: Moriuchi Hiroshi , Okamoto Chiho , Nishihama Ryuichi , Yamashita Ichiro , Machida Yasunori , Tanaka Nobukazu
Published: April 2004

The rooting‐locus gene B (rolB) on the T‐DNA of the root‐inducing (Ri) plasmid in Agrobacterium rhizogenes is responsible for the induction of transformed adventitious roots, although the root induction mechanism is unknown. We report here that the RolB protein of pRi1724 (1724RolB) is associated with Nicotianatabacum14‐3‐3‐like protein ωII (Nt14‐3‐3 ωII) in tobacco bright yellow (BY)‐2 cells. Nt14‐3‐3 ωII directly interacts with 1724RolB protein. Green fluorescent protein (GFP)‐fused 1724RolB is localized to the nucleus. GFP‐fused mutant 1724RolB proteins having a deletion or amino acid substitution are unable to interact with Nt14‐3‐3 ωII and also show impaired nuclear localization. Moreover, these 1724RolB mutants show decreased capacity for adventitious root induction. These results suggest that adventitious root induction by 1724RolB protein correlates with its interaction with Nt14‐3‐3 ωII and the nuclear localization of 1724RolB protein.
Canopy studies on ethylene‐insensitive tobacco identify ethylene as a novel element in blue light and plant–plant signalling
Authors: Pierik Ronald , Whitelam Garry C. , Voesenek Laurentius A. C. J. , De Kroon Hans , Visser Eric J. W.
Published: April 2004

Plants growing at high densities express shade avoidance traits as a response to the presence of neighbours. Enhanced shoot elongation is one of the best researched shade avoidance components and increases light capture in dense stands. We show here that also leaf movements, leading to a more vertical leaf orientation (hyponasty), may be crucial in the early phase of competition. The initiation of shade avoidance responses is classically attributed to the action of phytochrome photoreceptors that sense red:far‐red (R:FR) ratios in light reflected by neighbours, but also other signals may be involved. It was recently shown that ethylene‐insensitive, transgenic (Tetr) tobacco plants, which are insensitive to the gaseous plant hormone ethylene, have reduced shade avoidance responses to neighbours. Here, we report that this is not related to a reduced response to low R:FR ratio, but that Tetr tobacco plants are unresponsive to a reduced photon fluence rate of blue light, which normally suppresses growth inhibition in wild‐type (WT) plants. In addition to these light signals, ethylene levels in the canopy atmosphere increased to concentrations that could induce shade avoidance responses in WT plants. Together, these data show that neighbour detection signals other than the R:FR ratio are more important than previously anticipated and argue for a particularly important role for ethylene in determining plant responses to neighbours.
Characterization of heterotrimeric G protein complexes in rice plasma membrane
Authors: Kato Chiyuki , Mizutani Tomohiro , Tamaki Hisanori , Kumagai Hidehiko , Kamiya Takehiro , Hirobe Ayumi , Fujisawa Yukiko , Kato Hisaharu , Iwasaki Yukimoto
Published: April 2004

Two genes in the rice genome were identified as those encoding the γ subunits, γ1 and γ2, of heterotrimeric G proteins. Using antibodies against the recombinant proteins for the α, β, γ1, and γ2 subunits of the G protein complexes, all of the subunits were proven to be localized in the plasma membrane in rice. Gel filtration of solubilized plasma membrane proteins showed that all of the α subunits were present in large protein complexes (about 400 kDa) containing the other subunits, β, γ1, and γ2, and probably also some other proteins, whereas large amounts of the β and γ (γ1 and γ2) subunits were freed from the large complexes and took a 60‐kDa form. A yeast two‐hybrid assay and co‐immunoprecipitation experiments showed that the β subunit interacted tightly with the γ1 and γ2 subunits, and so the β and γ subunits appeared to form dimers in rice cells. Some dimers were associated with the α subunit, because few β, γ1, and γ2 subunits were present in the 400‐kDa complexes in a rice mutant,d1, which was lacking in the α subunit. When a constitutively active form of the α subunit was prepared by the exchange of one amino acid residue and introduced intod1, the mutagenized subunit was localized in the plasma membrane of the transformants and took a free, and not the 400‐kDa, form.
Immunohistochemical analysis of nervous system regeneration in chimeric individuals of Dorvillea bermudensis (Polychaeta, Dorvilleidae)
Authors: Müller Monika C. M.
Published: April 2004

In regeneration experiments, 0.5% of the two‐ or five‐segmented fragments of the polychaete Dorvillea bermudensis were found unexpectedly transplanted: two fragments of each that were lying close together during the initial period, fused and regenerated a chimeric individual. Of the three theoretical possibilities (i.e. fusion of (i) two posterior ends; (ii) one anterior and one posterior end; (iii) or two anterior ends) only the last two were realized. The similarly oriented fragments regenerated a normal animal while anterior–anterior fused ones produced two heads or a double head. Whether the ventral cords of the fragments are located vis‐à‐vis or adjacent, influences the course of regeneration as well. Immunohistochemical methods (anti‐acetylated α‐tubulin) in conjunction with confocal laser scanning microscopy were used to investigate the wiring pattern of the nervous systems of the grafts. In all cases, at least two supraesophageal ganglia were formed and palps, antennae and nuchal organs were innervated by the correct nerves but, in special cases, were innervated vice versa from the other brain. From these results it can be concluded that fusion of a regenerating connective with another connective results in formation of a new brain, irrespective of whether it belongs to the same nerve cord or not.
Defect in peroxisomal multifunctional enzyme MFE1 affects cAMP relay in Dictyostelium
Authors: Matsuoka Satomi , Kuwayama Hidekazu , Ikeno Daisuke , Oyama Masakazu , Maeda Mineko
Published: April 2004

We have previously reported that cells of Dictyostelium discoideum lacking the fatty acid oxidation enzyme MFE1 accumulate excess cyclopropane fatty acids from ingested bacteria. Cells in which mfeA– is disrupted fail to develop when grown in association with bacteria but form normal fruiting bodies when grown in axenic media. Bacterially grown mfeA– cells express the genes for the cyclic AMP (cAMP) receptor (carA) and adenylyl cyclase (acaA) but fail to respond to a cAMP pulse by synthesis of additional cAMP which normally relays the signal. Moreover, they do not accumulate the adhesion protein, gp80, which is encoded by the cAMP‐induced gene, csaA. As a consequence, they do not acquire developmentally regulated EDTA‐resistant cell–cell adhesion. When mutant cells are mixed with wild‐type cells and allowed to develop together, they co‐aggregate and differentiate into both spores and stalk cells. Thus, most of the developmental consequences of excess cyclopropane fatty acids appear to result from impaired cAMP relay.
The mechanism of Drosophila leg development along the proximodistal axis
Authors: Kojima Tetsuya
Published: April 2004

During development of higher organisms, most patterning events occur in growing tissues. Thus, unraveling the mechanism of how growing tissues are patterned into final morphologies has been an essential subject of developmental biology. Limb or appendage development in both vertebrates and invertebrates has attracted great attention from many researchers for a long time, because they involve almost all developmental processes required for tissue patterning, such as generation of the positional information by morphogen, subdivision of the tissue into distinct parts according to the positional information, localized cell growth and proliferation, and control of adhesivity, movement and shape changes of cells. The Drosophila leg development is a good model system, upon which a substantial amount of knowledge has been accumulated. In this review, the current understanding of the mechanism of Drosophila leg development is described.
Ophthalmic techniques described by Şerefeddin Sabuncuoğlu (1385−1468 ad)
Authors: Oguz Halit , San Imran , Verit Ayhan , Uzel Ilter
Published: April 2004

¸Serefeddin Sabuncuoglu (1385−1468 ad) was a Turkish surgeon who lived in the Ottoman Empire during the fifteenth century, a time of progressive expansion. When in his eighties, he wrote Cerrahiyyetü’l‐Haniyye, which means Imperial Surgery. His book is the first example of an illustrated surgical textbook in the Turkish−Islamic medical literature. The importance of his book rests upon the inclusion of colour miniatures of the surgical procedures, incisional techniques and instruments, all drawn by Sabuncuog˘lu himself. Only three hand‐written copies exist, two of which were originally written by the author and are currently exhibited in Paris and Istanbul. The book was rediscovered in 1936, but some parts of it are still suspected to be missing. At present, the book consists of three chapters divided into 193 known sections. The sections deal with all fields of surgery including ophthalmology, and cite relevant Greek, Arabic and Persian textbooks. In this historical article the sections of Cerrahiyyetü’l‐Haniyye pertinent to ophthalmology are critically reviewed, including a selection of the coloured drawings.
Corneal epithelial cellular dysfunction from benzalkonium chloride (BAC) in vitro
Authors: Cha Seung‐Heon , Lee Jong‐Soo , Oum Boo‐Sup , Kim Chi‐Dae
Published: April 2004

Purpose: To investigate the functional and morphological toxicity of benzalkonium chloride (BAC) on corneal epithelial cells in vitro.

Methods: Primary corneal epithelial cells were cultured from rabbit cornea. Corneal epithelial cells containing radioactive 51Cr were exposed for 5 min, 10 min, 30 min and 60 min to concentration of BAC 0.001%, 0.005%, 0.01%, 0.05% and 0.1%. Control cells were treated with phosphate buffer solution alone. 51Cr release from epithelial cells into the supernatant was used as an index of epithelial cell lysis. Cell detachment (index of cell dysfunction) was analysed by measuring 51Cr activity in the supernatant and wash fluid. Morphological cell damage was investigated with transmission electron microscopy.

Results: With the higher concentration and the longer duration of BAC exposure, corneal epithelial cell lysis was increased significantly (P < 0.05). Cells showed severe damage at BAC concentration over 0.05% during 5 min of exposure. Cell dysfunction appeared markedly at BAC concentrations of 0.005% for 30 min of exposure, but decreased with longer exposure times. There was an increase in significant cytoplasmic damage with longer BAC exposure times, although not with a minimal dose of 0.001%. Disrupted cytoplasmic membranes of corneal epithelial cells appeared at the higher BAC concentration of 0.1%, and at the longer exposure time of 30 min with BAC concentration of at least 0.001%.

Conclusions: BAC can induce corneal epithelial dysfunction, which can damage the corneal epithelial barrier. This effect occurs when BAC is used frequently or for periods over 30 min, even when the BAC concentration is low (0.001%).
Clinical Case Notes
Authors: Narendran Niro , Doyle Eddie , Laidlaw Alistair
Published: April 2004

Vitreous cysts are rare structural entities of uncertain aetiology. Although most do not produce troublesome visual symptoms, they can cause diagnostic difficulties in clinical practice. Two different types are described and the possible aetiologies of congenital and acquired vitreous cysts are discussed.
Clinical Case Notes
Authors: Kumar Nikhil , Zeldovich Alina , Chang Andrew
Published: April 2004

A case is reported of a 72‐year‐old man with an intruded scleral buckle presenting 30 years after retinal detachment repair. The lesion was noted incidentally and occupied the superotemporal retinal periphery. The diagnosis was confirmed by B‐scan ultrasonography and external examination of the globe. The patient was treated conservatively. No clinical change was evident after 12 months follow up.
Longevity‐associated mitochondrial DNA 5178 A/C polymorphism is associated with intraocular pressure in Japanese men
Authors: Kokaze Akatsuki , Yoshida Masao , Ishikawa Mamoru , Matsunaga Naomi , Makita Ryuji , Satoh Masao , Sekiguchi Kanako , Masuda Yumi , Uchida Yoshiko , Takashima Yutaka
Published: April 2004

Background: Mitochondrial DNA 5178 adenine/cytosine (mt5178 A/C) polymorphism has been reported to be associated with longevity in Japanese individuals, with experimental findings concluding that mt5178 A is an anti‐atherogenic genotype. The aim of this study was to determine whether mt5178 A/C polymorphism influences intraocular pressure (IOP), and its relationship with the development of arteriosclerosis.

Methods: Four hundred and forty‐nine male volunteers who had visited a general hospital for medical check‐up between August 1999 and August 2000 were enrolled. Of these, 386 Japanese men who had not undergone any medical treatment for hypertension, ocular hypertension or glaucoma were selected as subjects of this study. After these subjects were genotyped, a cross‐sectional study regarding the relationship between genotype and IOP was conducted.

Results: Mean IOP was significantly higher in men with mt5178 C (13.3 mmHg) than in those with mt5178 A (12.7 mmHg) (P = 0.037). This significant difference in mean IOP between the two genotypes remained evident after adjusting for age, body mass index, blood pressure, habitual smoking and habitual drinking. Interactions between mt5178 A/C polymorphism and habitual smoking or daily alcohol consumption with regard to IOP were observed. According to multiple regression analysis, habitual smoking was significantly associated with IOP in men with mt5178 A (P for trend = 0.020), while daily alcohol consumption was significantly associated with IOP in those with mt5178 C (P for trend = 0.021).

Conclusion: Longevity‐associated mitochondrial DNA 5178 A/C polymorphism may be associated with IOP in Japanese men.
Clinical Case Note
Authors: Sekhar G Chandra , Onam K Sreelatha , Kunjam Vallam
Published: April 2004

Plateau iris syndrome is considered to be a rare entity and has been classified into two subtypes, the complete and the incomplete forms. Herein a case is reported of plateau iris syndrome that had a postmydriatic rise in intraocular pressure (IOP) in one eye (complete syndrome) and no increase in IOP in the other (incomplete syndrome). The pre‐ and post‐mydriasis ultrasound biomicroscopic findings were documented. These findings suggest that incomplete plateau iris syndrome may be caused by a difference in the extent of closure of the angle circumferentially over the 360 degrees of the angle.
Glial fibrillary acidic protein gene promoter is differently modulated by transforming growth factor‐beta 1 in astrocytes from distinct brain regions
Authors: De Oliveira Sousa Vivian , Romão Luciana , Neto Vivaldo Moura , Gomes Flávia Carvalho Alcantara
Published: April 2004

The expression of glial fibrillary acidic protein (GFAP), the major intermediate filament protein of mature astrocytes, is regulated under developmental and pathological conditions. Recently, we have investigated GFAP gene modulation by using a transgenic mouse bearing part of the GFAP gene promoter linked to the β‐galactosidase reporter gene. We demonstrated that cerebral cortex neurons activate the GFAP gene promoter, inducing transforming growth factor‐beta 1 (TGF‐β1) secretion by astrocytes. Here, we report that cortical neurons or conditioned medium derived from them do not activate the GFAP gene promoter of transgenic astrocytes derived from midbrain and cerebellum suggesting a neuroanatomical regional specificity of this phenomenon. Surprisingly, they do induce synthesis of TGF‐β1 by these cells. Western blot and immunocytochemistry assays revealed wild distribution of TGF receptor in all subpopulations of astrocytes and expression of TGF‐β1 in neurons derived from all regions, thus indicating that the unresponsiveness of the cerebellar and midbrain GFAP gene to TGF‐β1 is not due to a defect in TGF‐β1 signalling. Together, our data highlight the great complexity of neuron–glia interactions and might suggest a distinct mechanism underlying modulation of the GFAP gene in the heterogeneous population of astrocytes throughout the central nervous system.
Anxiety and cognition in histamine H3 receptor−/− mice
Authors: Rizk Angela , Curley Justine , Robertson Jennifer , Raber Jacob
Published: April 2004

Histamine H3 receptors (H3Rs) were first characterized as autoreceptors modulating histamine release and synthesis via negative feedback. Acute H3R stimulation or blockade with selective agonists and antagonists suggests a role for H3R in anxiety and cognition. However, little is known about the long‐term effects of H3R blockade on brain function. In the current study, mice lacking H3 receptors (H3R−/−) were used to investigate the role of H3R‐mediated signalling in anxiety and cognition. H3R−/− mice showed enhanced spatial learning and memory in the Barnes maze. In addition, H3R−/− mice showed reduced measures of anxiety in the elevated plus and zero mazes involving exploratory behaviour and avoidable anxiety‐provoking stimuli, but enhanced acoustic startle responses involving unavoidable anxiety‐provoking stimuli. These behavioural alterations were associated with higher arginine vasopressin levels in the central and basolateral nuclei of the amygdala. These findings support a role for H3Rs in mediating histamine effects on spatial learning and memory and measures of anxiety.
Characterization of the inhibitory glycine receptor on entorhinal cortex neurons
Authors: Breustedt Jörg , Schmitz Dietmar , Heinemann Uwe , Schmieden Volker
Published: April 2004

In addition to the well‐established functional description of the glycine receptor (GlyR) in the spinal cord, GlyR expression has recently been found in higher brain regions, such as the striatum or hippocampus. In this study we have investigated the electrophysiological response of glycine in the rat entorhinal cortex slice. In all recorded cells we found significant current responses to glycine with an EC50 value of about 100 µm. Most importantly, we detected a cross‐inhibition of glycine responses by GABA but not vice versa. These findings are in line with recent published data of cross‐talks between GABAAR and GlyR but indicate a novel type of cross‐inhibition of these receptors in the entorhinal cortex.
Differential regulation of hippocampal progenitor proliferation by opioid receptor antagonists in running and non‐running spontaneously hypertensive rats
Authors: Persson Anders I. , Naylor Andrew S. , Jonsdottir Ingibjörg H. , Nyberg Fred , Eriksson Peter S. , Thorlin Thorleif
Published: April 2004

Voluntary running in mice and forced treadmill running in rats have been shown to increase the amount of proliferating cells in the hippocampus. Little is known as yet about the mechanisms involved in these processes. It is well known that the endogenous opioid system is affected during running and other forms of physical exercise. In this study, we evaluated the involvement of the endogenous opioids in the regulation of hippocampal proliferation in non‐running and voluntary running rats. Nine days of wheel running was compared with non‐running in spontaneously hypertensive rats (SHR), a rat strain known to run voluntarily. On the last 2 days of the experimental period all rats received two daily injections of the opioid receptor antagonists naltrexone or naltrindole together with injections of bromodeoxyuridine to label dividing cells. Brain sections from the running rats showed approximately a five‐fold increase in newly generated cells in the hippocampus, and this increase was partly reduced by naltrexone but not by naltrindole. By contrast, both naltrexone and naltrindole increased hippocampal proliferation in non‐running rats. In non‐running rats the administration of naltrexone decreased corticosterone levels and adrenal gland weights, whereas no significant effects on these parameters could be detected for naltrindole. However, adrenal gland weights were increased in naltrexone‐ but not in naltrindole‐administered running rats. In addition, in voluntary running rats there was a three‐fold increase in the hippocampal levels of Met‐enkephalin‐Arg‐Phe compared with non‐runners, indicating an increase in opioid activity in the hippocampus during running. These data suggest an involvement of endogenous opioids in the regulation of hippocampal proliferation in non‐running rats, probably through hypothalamic–pituitary–adrenal axis modulation. During voluntary running in SHR naltrexone altered hippocampal proliferation via as yet unknown mechanisms.
Automatic detection of motion direction changes in the human brain
Authors: Pazo‐Alvarez P. , Amenedo E. , Cadaveira F.
Published: April 2004

The possibility that the visual system is able to register unattended changes is still debated in the literature. However, it is difficult to understand how a sensory system becomes aware of unexpected salient changes in the environment if attention is required for detecting them. The ability to automatically detect unusual changes in the sensory environment is an adaptive function which has been confirmed in other sensory modalities (i.e. audition). This deviance detector mechanism has proven to be based on a preattentive nonrefractory memory‐comparison process. To investigate whether such automatic change detection mechanism exists in the human visual system, we recorded event‐related potentials to sudden changes in a biologically important feature, motion direction. Unattended sinusoidal gratings varying in motion direction in the peripheral field were presented while subjects performed a central task with two levels of difficulty. We found a larger negative displacement in the electrophysiological response elicited by less frequent stimuli (deviant) at posterior scalp locations. Within the latency range of the visual evoked component N2, this differential response was elicited independently of the direction of motion and processing load. Moreover, the results showed that the negativity elicited by deviants was not related to a differential refractory state between the electrophysiological responses to frequent and infrequent directions of motion, and that it was restricted to scalp locations related to motion processing areas. The present results suggest that a change‐detection mechanism sensitive to unattended changes in motion direction may exist in the human visual system.
Temporal and spatial expression patterns of canonical clock genes and clock‐controlled genes in the suprachiasmatic nucleus
Authors: Hamada Toshiyuki , Antle Michael C. , Silver Rae
Published: April 2004

In mammals, the suprachiasmatic nuclei (SCN) of the hypothalamus control endogenous circadian rhythms and entrainment to the environment. A core SCN region of calbindin (CalB)‐containing cells is retinorecipient and the cells therein lack rhythmic expression of clock genes and electrical activity. The core is surrounded by a ‘shell’ of rhythmic oscillator cells. In the present experiments, we studied the spatial arrangement of oscillator cells by examining the spatial and temporal patterns of expression of the canonical clock genes Per1, Per2 and vasopressin mRNA, a clock‐controlled gene. Surprisingly, in the SCN shell, the dorsomedial cells were the first to rhythmically express both Per1 and VP mRNA, with gene expression then spreading very slowly through much of the nucleus for the next 12 h then receding to baseline levels. Following a light pulse, Per expression increased after 1 h in the core SCN and after 1.5 h in the shell. Although expression in the shell occurred earlier in light‐pulsed animals than in those housed in constant darkness, it still followed the same spatial and temporal expression pattern as was observed in constant darkness. The results suggest that not only is the SCN organized into light‐responsive and rhythmic regions but also that the rhythmic region of the SCN itself has an ordered arrangement of SCN oscillator cells.
Stereological analysis of the reorganization of the dentate gyrus following entorhinal cortex lesion in mice
Authors: Phinney A. L. , Calhoun M. E. , Woods A. G. , Deller T. , Jucker M.
Published: April 2004

Denervation of the dentate gyrus by entorhinal cortex lesion has been widely used to study the reorganization of neuronal circuits following central nervous system lesion. Expansion of the non‐denervated inner molecular layer (commissural/associational zone) of the dentate gyrus and increased acetylcholinesterase‐positive fibre density in the denervated outer molecular layer have commonly been regarded as markers for sprouting following entorhinal cortex lesion. However, because this lesion extensively denervates the outer molecular layer and causes tissue shrinkage, stereological analysis is required for an accurate evaluation of sprouting. To this end we have performed unilateral entorhinal cortex lesions in adult C57BL/6J mice and have assessed atrophy and sprouting in the dentate gyrus using modern unbiased stereological techniques. Results revealed the expected increases in commissural/associational zone width and density of acetylcholinesterase‐positive fibres on single brain sections. Yet, stereological analysis failed to demonstrate concomitant increases in layer volume or total acetylcholinesterase‐positive fibre length. Interestingly, calretinin‐positive fibres did grow beyond the border of the commissural/associational zone into the denervated layer and were regarded as sprouting axons. Thus, our data suggest that in C57BL/6J mice shrinkage of the hippocampus rather than growth of fibres underlies the two morphological phenomena most often cited as evidence of regenerative sprouting following entorhinal cortex lesion. Moreover, our data suggest that regenerative axonal sprouting in the mouse dentate gyrus following entorhinal cortex lesion may be best assessed at the single‐fibre level.
Co‐localization of endomorphin‐2 and substance P in primary afferent nociceptors and effects of injury: a light and electron microscopic study in the rat
Authors: Sanderson Nydahl Katarina , Skinner Kate , Julius David , Basbaum Allan I.
Published: April 2004

Endomorphin‐2 (EM2) is a tetrapeptide with remarkable affinity and selectivity for the mu‐opioid receptor. In the present study, we used double‐fluorescence and electron microscopic immunocytochemistry to identify subsets of EM2‐expressing neurons in dorsal root ganglia and spinal cord dorsal horn of adult rats. Within the lumbar dorsal root ganglia, we found EM2 immunoreactivity mainly in small‐to‐medium size neurons, most of which co‐expressed the neuropeptide substance P (SP). In adult rat L4 dorsal root ganglia, 23.9% of neuronal profiles contained EM2 immunoreactivity and ranged in size from 15 to 36 µm in diameter (mean 24.3 ± 4.3 µm). Double‐labelling experiments with cytochemical markers of dorsal root ganglia neurons showed that approximately 95% of EM2‐immunoreactive cell bodies also label with SP antisera, 83% co‐express vanilloid receptor subtype 1/capsaicin receptor, and 17% label with isolectin B4, a marker of non‐peptide nociceptors. Importantly, EM2 immunostaining persisted in mice with a deletion of the preprotachykinin‐A gene that encodes SP. In the lumbar spinal cord dorsal horn, EM2 expression was concentrated in presumptive primary afferent terminals in laminae I and outer II. At the ultrastructural level, electron microscopic double‐labelling showed co‐localization of EM2 and SP in dense core vesicles of lumbar superficial dorsal horn synaptic terminals. Finally, 2 weeks after sciatic nerve axotomy we observed a greater than 50% reduction in EM2 immunoreactivity in the superficial dorsal horn. We suggest that the very strong anatomical relationship between primary afferent nociceptors that express SP and EM2 underlies an EM2 regulation of SP release via mu‐opioid autoreceptors.
Involvement of brain‐derived neurotrophic factor in cannabinoid receptor‐dependent protection against excitotoxicity
Authors: Khaspekov Leonid G. , Brenz Verca Maria S. , Frumkina Lidia E. , Hermann Heike , Marsicano Giovanni , Lutz Beat
Published: April 2004

Cannabinoid type 1 (CB1) receptors play a central role in the protection against excitotoxicity induced by treatment of mice with kainic acid (KA). As inactivation of CB1 receptor function in mice blocks KA‐induced increase of brain‐derived neurotrophic factor (BDNF) mRNA levels in hippocampus, the notion was put forward that BDNF might be a mediator, at least in part, of CB1 receptor‐dependent neuroprotection [Marsicano et al. (2003) Science, 302, 84–88]. To assess this signalling cascade in more detail, organotypic hippocampal slice cultures were used, as this in vitro system conserves morphological and functional properties of the hippocampus. Here, we show that both genetic ablation of CB1 receptors and pharmacological blockade with the specific CB1 receptor antagonist SR141716A increased the susceptibility of the in vitro cultures to KA‐induced excitotoxicity, leading to extensive neuronal death. Next, we found that the application of SR141716A to hippocampal cultures from wild‐type mice abolished the KA‐induced increase in BDNF protein levels. Therefore, we tried to rescue these organotypic cultures from neuronal death by exogenously applied BDNF. Indeed, BDNF was sufficient to prevent KA‐induced neuronal death after blockade of CB1 receptor signalling. In conclusion, our results strongly suggest that BDNF is a key mediator in CB1 receptor‐dependent protection against excitotoxicity, and further underline the physiological importance of the endogenous cannabinoid system in neuroprotection.
Mice lacking 5‐HT7 receptors show specific impairments in contextual learning
Authors: Roberts Amanda J. , Krucker Thomas , Levy Coree L. , Slanina Kristen A. , Sutcliffe J. Gregor , Hedlund Peter B.
Published: April 2004

Using 5‐HT7 receptor knockout mice it has been shown that the 5‐HT7 receptor is the main mediator of serotonin‐induced hypothermia but very little is known about the relevance of 5‐HT7 receptors in behaviour. We here report that lack of 5‐HT7 receptors leads to a specific learning deficit that is not due to general sensory or behavioural deficits. The knockout mice show impaired contextual fear conditioning but no significant deficits in motor and spatial learning or cued and operant conditioning. In addition, we demonstrate that 5‐HT7 receptor knockout mice display decreased long‐term synaptic plasticity within the CA1 region of the hippocampus. The results indicate an important role for the 5‐HT7 receptor in contextual hippocampal‐dependent learning and suggest a possible neuronal correlate for such a role is present within the CA1 region of the hippocampus.
Context‐dependent effects of CB1 cannabinoid gene disruption on anxiety‐like and social behaviour in mice
Authors: Haller J. , Varga B. , Ledent C. , Barna I. , Freund T. F.
Published: April 2004

Contrasting data were reported regarding the effects of cannabinoids on anxiety and social behaviour in both animals and humans. The cognitive effects of cannabinoids and their interactions with the HPA‐axis raise the possibility that cannabinoid effects are context but not behaviour specific. To assess this hypothesis, we submitted CB1 receptor knock‐out (CB1‐KO) and wild‐type (WT) mice to tests, which involved similar behaviours, but the behavioural context was different. The elevated plus‐maze test was performed under less and more anxiogenic conditions, i.e. under low and high light, respectively. We also compared the social behaviour of the two genotypes in the resident/intruder and social interaction tests. Both tests represent a social challenge and induce similar behaviours, but involve different contexts. The behaviour of CB1‐KO and WT mice was similar under low light, but CB1 gene disruption increased anxiety‐like behaviour under the high light condition. CB1 gene disruption promoted aggressive behaviour in the home‐cage, whereas it inhibited social behaviour in the unfamiliar cage. Thus, the anxiogenic‐like effect was restricted to the more stressful unfamiliar environment. These data suggest that the effects of CB1 gene disruption were context and not behaviour specific. Novelty stress resulted in higher ACTH levels in CB1‐KOs than in WTs, which suggests that context dependency occurred in conjunction with an altered HPA axis function. The present data at least partly explain contrasting effects of cannabinoids in different contexts as well as in different species and strains that show differential stress responses and coping strategies.
Neurons in hippocampal afferent zones of rat striatum parse routes into multi‐pace segments during maze navigation
Authors: Mulder Antonius B. , Tabuchi Eiichi , Wiener Sidney I.
Published: April 2004

Hippocampal ‘place’ neurons discharge when rats occupy specific regions within an environment. This finding is a cornerstone of the theory of the hippocampus as a cognitive map of space. But for navigation, representations of current position must be implemented by signals concerning where to go next, and how to get there. In recordings in hippocampal output structures associated with the motor system (nucleus accumbens and ventromedial caudate nucleus) in rats solving a plus‐maze, neurons fired continuously from the moment the rat left one location until it arrived at the next goal site, or at an intermediate place, such as the maze centre. While other studies have shown discharges during reward approach behaviours, this is the first demonstration of activity corresponding to the parsing of complex routes into sequences of movements between landmarks, similar to the lists of instructions we often employ to communicate directions to follow between points on a map. As these cells fired during a series of several paces or re‐orientation movements, perhaps this is homologous to ‘chunking’. The temporal overlaps in the activity profiles of the individual neurons provide a possible substrate to successively trigger movements required to arrive at the goal. These hippocampally informed, and in some cases, spatially selective responses support the view of the ventral striatum as an interface between limbic and motor systems, permitting contextual representations to have an impact on fundamental action sequences for goal‐directed behaviour.
On the regulation of NMDA receptors by nitric oxide
Authors: Hopper Rachel , Lancaster Barrie , Garthwaite John
Published: April 2004

Nitric oxide (NO) is generated in central synapses on activation of N‐methyl‐d‐aspartate (NMDA) receptors and exerts physiological effects by changing cGMP levels. NO has frequently also been claimed to engage a different mechanism, namely the covalent modification of thiol residues (S‐nitrosation), and thereby exert a negative feedback on NMDA receptors. Tests of this hypothesis were conducted by recording NMDA receptor‐mediated synaptic potentials in the CA1 area of rat hippocampal slices. Manipulations designed to increase or decrease endogenous NO levels had no effect. Addition of exogenous NO using a NONOate donor in concentrations up to 30‐fold higher than those needed to evoke maximal cGMP accumulation also had no effect. Nevertheless, in agreement with previous findings, photolysis of a caged NO derivative with UV light led to an enduring block of synaptic NMDA receptors. To address these contradictory results, NMDA receptor‐mediated currents were recorded from HEK‐293 cells transfected with NR1 and NR2A subunits. As found in slices, photolysis of caged NO inhibited the currents whereas perfusion of NO (up to 5 µm) was ineffective. However, when NO was supplied at a concentration found to be effective when released photolytically (5 µm) and the cells simultaneously exposed to the UV light used for photolysis, NMDA receptor‐mediated currents were inhibited. This effect was not observed at more physiological NO concentrations (10 nm range). The results indicate that neither endogenous NO nor exogenous NO in supra‐physiological concentration inhibits synaptic NMDA receptors; the combination of high NO concentration and UV light can give an artifactual result.
Differential distribution of calpain small subunit 1 and 2 in rat brain
Authors: Friedrich Peter , Papp Henrietta , Halasy Katalin , Farkas Attila , Farkas Bence , Tompa Peter , Kása Peter
Published: April 2004

Calpains, the Ca2+‐dependent thiol proteases, are abundant in the nervous tissue. The ubiquitous enzyme forms in mammals are heterodimers consisting of a specific, µ or m, large (catalytic) subunit and, apparently, a common small (regulatory) subunit (CSS1). Recently, however, we described a second form of small subunit (CSS2), which is of restricted occurrence [Schád, E., Farkas, A., Jékely, G., Tompa, P. & Friedrich, P. (2002) Biochem. J., 362, 383–388]. Here we analysed the distribution of immunoreactivity in various parts of rat brain against two anti‐CSS1 and two anti‐CSS2 antibodies by correlated light and electron microscopy. Remarkably, the antibodies showed differential distribution in various parts of rat cortex: anti‐CSS1 reacted mainly with perikarya and dendrites, whereas anti‐CSS2 was more prominent in axons. In serial sections CSS2 and synaptophysin gave very similar patterns, i.e. these epitopes seem to colocalize. Electron microscopy confirmed that CSS1 was mainly localized postsynaptically in dendrites and somata, whereas CSS2 was found presynaptically. The hypothesis is advanced that these distinct distributions of calpain subunits may be related to the transport of these enzymes in nerve cells.
People, Place and Party: Describing Party Activism
Authors: Young David M.
Published: April 2004

The aim of this article is to present a structure for the historical study of party activism. Based on research carried out on the activities of the Social Democratic Federation (SDF) between 1884 and 1911, the article puts forward the case that current understandings of that organisation should be reassessed to include the notion of the ‘political journeys’ of the activists. Instead of focusing exclusively on ideology, the article suggests that other poles or features such as locality and collective biography should be used. If the organisation is viewed from a wider perspective and with a longer exposure time, then, this article argues, a clearer picture presents itself.