bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sympathoadrenal System Differentially Affects Photoperiodic Changes in Humoral Immunity of Siberian Hamsters (Phodopus sungorus)
Authors: Demas G. E. , Drazen D. L. , Jasnow A. M. , Bartness T. J. , Nelson R. J. 
Published: March 2003

AbstractSiberian hamsters (Phodopus sungorus) rely on photoperiod as a primary cue to coordinate seasonally appropriate changes in physiology and behaviour. Among these seasonal changes is reduced immune function in short ‘winter‐like’ days, compared to long ‘summer‐like’ days. Previous evidence suggests that immune function is regulated, in part, by the sympathoadrenal system. The precise role of the sympathoadrenal system in regulating photoperiodic changes in immune function, however, remains unspecified. The goal of the present study was to examine the differential contributions of direct sympathetic innervation of immune target tissue, as well as adrenal medullary catecholamines, to photoperiodic changes in immune function in male Siberian hamsters. In Experiment 1, hamsters underwent either bilateral surgical removal of the adrenal medulla (ADMEDx), or sham surgeries, and were maintained in long (LD 16 : 8) or short days (LD 8 : 16). In Experiment 2, hamsters received either surgical denervation of the spleen, or sham surgeries, and were then housed in long or short days. Serum anti‐KLH IgG concentrations and splenic norepinephrine (NE) content were determined in both experiments. Short‐day hamsters had reduced humoral immunity compared to long‐day hamsters. ADMEDx reduced immune function, but only in long‐day hamsters. In contrast, splenic denervation reduced humoral immunity, but only in short‐day hamsters. Splenic NE content was increased in short days and by ADMEDx. NE content was markedly reduced in denervated hamsters compared to sham‐operated hamsters. Collectively, these results suggest that the sympathoadrenal system is associated with photoperiodic changes in immune function.
Evidence in Favour of a Direct Input from the Ventromedial Nucleus to Gonadotropin‐Releasing Hormone Neurones in the Ewe: An Anterograde Tracing Study
Authors: Goubillon M.‐L. , Caraty A. , Herbison A. E. 
Published: March 2003

AbstractThe mechanism by which oestrogen activates the gonadotropin releasing hormone (GnRH) neurones to induce the preovulatory luteinizing hormone (LH) surge is not understood. Previous work in the ewe has suggested that the primary site of action for oestradiol in stimulating the GnRH neurones was in the region of the ventromedial nucleus (VMN) within the mediobasal hypothalamus (MBH). In the present study, we used anterograde tracing techniques in the ewe to investigate whether direct neuronal projections may exist from neurones located in the region of the VMN to the GnRH neurones. Following the injection of biotinylated dextran amine into the VMN of four ewes, anterogradely labelled fibres were found located principally within the ipsilateral diagonal band of Broca (DBB), septum, preoptic and anterior hypothalamic areas, and periventricular, paraventricular, dorsomedial and arcuate nuclei of the MBH. Dual‐labelling for GnRH revealed that fibres containing anterograde tracer were adjacent to the soma and/or dendrites of approximately 50% of all ipsilateral GnRH neurones located throughout the DBB and hypothalamus. Few anterogradely labelled fibres were detected within the median eminence. Although such studies cannot define the presence of direct synaptic connections between VMN neurones and the GnRH cells, these observations support further the hypothesis that oestrogen‐sensitive VMN neurones represent a direct transsynaptic input to the GnRH cell bodies which are involved in the generation of the LH surge in the ewe.
Distribution of Gonadotropin‐Releasing Hormone Neurones in the Chick Forebrain is Independent of Lineage Relationships Among Cells of the Early Nasal Placode
Authors: Silverman A.‐J. , Cserjesi P. , Kanter E. 
Published: March 2003

AbstractThe regulation of reproduction depends upon the successful migration of gonadotropin‐releasing hormone (GnRH) neurones from the nasal placode to the ventral forebrain during embryogenesis. Within the central nervous system (CNS), these neurones migrate to stereotyped, highly reproducible locations in septal, preoptic and hypothalamic nuclei. We postulated that lineage relationships (descent from a common precursor) might predict the final location of these neurones. To test this hypothesis, a complex retroviral library was used to label dividing cells in the placode and subsequently to identify them by the presence of the alkaline phosphatase marker. GnRH was detected immunocytochemically and lineage relationships determined by single cell polymerase chain reaction and sequencing of the degenerate oligonucleotide component of the retrovirus. GnRH‐positive and GnRH‐negative neurones were confined to the side ipsilateral to the injection; many cells derived from the placode that entered the CNS did not contain GnRH. This precise method of identifying and mapping the progeny of single neurones revealed that GnRH cells in any given area were derived from multiple precursors. This developmental pattern may contribute to assuring that all CNS locations critical to the orchestration of reproductive events will be populated by GnRH neurones.
Interactive effects of ozone and drought stress on pigments and activities of antioxidative enzymes in Pinus halepensis
Authors: Alonso R. , Elvira S. , Castillo F. J. , Gimeno B. S. 
Published: March 2003

AbstractThe aim of this study was to investigate the interactive effects of ozone (O3) and drought on pigments and antioxidant enzymes of Aleppo pine (Pinus halepensis). Two‐year‐old seedlings were exposed in open‐top chambers to charcoal‐filtered air or non‐filtered air plus an additional  40 nL L−1 of ozone. After 20 months of O3 exposure, a subset of plants was subjected to drought stress by withholding water supply for 11 d. Ozone induced higher guaiacol peroxidase, catalase and KCN‐resistant superoxide dismutase (SOD) activities in young needles, while drought stress increased glutathione reductase and CuZnSOD. One‐year‐old needles showed lower capacity to activate these enzymes in response to stress. Both ozone and drought activated the xanthophyll cycle pool and reduced chlorophyll contents in both current and 1‐year‐old needles. The combined effects of ozone and drought decreased antioxidant enzyme activities and the capacity of recovering after re‐watering. Similarly, interactive effects of O3 and drought reduced xanthophyll‐mediated photoprotection capacity in 1‐year‐old needles but induced a higher conversion of the cycle in current‐year needles. These results showed that ozone modified the Aleppo pine response to drought stress, suggesting that this pollutant might be reducing the ability of this species to withstand other environmental stresses.
Drought‐ and desiccation‐induced modulation of gene expression in plants
Authors: Ramanjulu S. , Bartels D. 
Published: March 2003

AbstractDesiccation is the extreme form of dehydration. Tolerance of desiccation is acquired by seeds and in resurrection plants, a small group of angiosperms. Desiccation tolerance is the result of a complex cascade of molecular events, which can be divided into signal perception, signal transduction, gene activation and biochemical alterations leading to acquisition of tolerance. Many of these molecular processes are also observed during the dehydration of non‐tolerant plants. Here we try to give an overview of the gene expression programmes that are triggered by dehydration, with particular reference to protective molecules and the regulation of their expression. Potential transgenic approaches to manipulating stress tolerance are discussed.
Local measurements of nitrate and potassium fluxes along roots of maritime pine. Effects of ectomycorrhizal symbiosis
Authors: PlassarD C. , Guérin‐LaguettE A. , VérY A.‐A. , Casarin V. , Thibaud J.‐B. 
Published: March 2003

AbstractIn order to assess the actual role of ectomycorrhizae in ion uptake by the ectomycorrhizal root system, we used a microelectrode ion flux estimation methodology that provided access to local values of net fluxes. This made it possible to investigate the heterogeneity of ion fluxes along the different types of roots of Pinus pinaster associated or not with ectomycorrhizal species. We compared two fungi able to grow with nitrate in pure culture, Rhizopogon roseolus and Hebeloma cylindrosporum, the former having a positive effect on host tree shoot growth (c. +30%) and the latter a negative effect (c.− 30%). In non‐mycorrhizal plants (control), NO3– was taken up at higher rates by the short roots than by the long ones, whereas K+ uptake occurred mainly in growing apices of long roots. In mycorrhizal plants, H. cylindrosporum did not modify K+ uptake and even decreased NO3– uptake at the level of ectomycorrhizal short roots, whereas R. roseolus strongly increased K+ and NO3– fluxes at the level of ectomycorrhizal short roots without any modification of the fluxes measured along the fungus‐free long roots. The measurement of ion influxes at the surface of the ectomycorrhizal roots can provide a way to reveal actual effects of mycorrhizal association on ion transport in relation to mycorrhizal efficiency in natural conditions.
Dynamics of stomatal water relations during the humidity response: implications of two hypothetical mechanisms
Authors: Buckley T. N. , Mott K. A. 
Published: March 2003

AbstractThe feasibility of two hypothetical mechanisms for the stomatal response to humidity was evaluated by identifying theoretical constraints on these mechanisms and by analysing timecourses of stomatal aperture following a step change in humidity. The two hypothetical mechanisms, which allow guard cell turgor pressure to overcome the epidermal mechanical advantage, are: (1) active regulation of guard cell osmotic pressure, requiring no hydraulic disequilibrium between guard and epidermal cells, and (2) a substantial hydraulic resistance between guard and epidermal cells, resulting in hydraulic disequilibrium between them. Numerical simulations of the system are made possible by recently published empirical relationships between guard cell pressure and volume and between stomatal aperture, guard cell turgor pressure, and epidermal cell turgor pressure; these data allow the hypothetical control variables to be inferred from stomatal aperture and evaporative demand, given physical assumptions that characterize either hypothesis. We show that hypothesis (1) predicts that steady‐state πg is monotonically related to transpiration rate, whereas hypothesis (2) suggests that the relationship between transpiration rate and the steady‐state guard to epidermal cell hydraulic resistance may be either positive or negative, and that this resistance must change substantially during the transient phase of the stomatal response to humidity.
A three‐dimensional model of CO2transport in airspaces and mesophyll cells of a silver birch leaf
Authors: Aalto T. , Juurola E. 
Published: March 2003

AbstractA realistic numerical three‐dimensional (3D) model was constructed to study CO2transport inside a birch leaf. The model included chloroplasts, palisade and spongy mesophyll cells, airspaces, stomatal opening and the leaf boundary layer. Diffusion equations for CO2were solved for liquid(mesophyll) and gaseous(air) phases. Simulations were made in typical ambient field conditions varying stomatal opening, photosynthetic capacity and temperature. Doubled ambient CO2concentration was also considered. Changes in variables caused non‐linear effects in the total flux, especially when compared with the results of double CO2concentration. The reduction in stomatal opening size had a smaller effect on the total flux in doubled concentrations than ambient CO2. The reduced photosynthetic capacity had a similar effect on the flux in both cases. The palisade and spongy mesophyll cells had unequal roles mainly due to the light absorption profile. Results from the 3D simulation were also compared to the classical one‐dimensional resistance approach. Liquid and gas phase resistances were estimated and found strongly variable according to changes in temperature and degree of stomatal opening. For the birch leaves modelled, intercellular airspace resistance was small (2% of the total resistance in saturating irradiance conditions at 25 °C at stomatal opening diameter of 4 µm) whereas the liquid phase resistance was significant (23% for mesophyll and chloroplasts in the same ‘base case’). The absorption of CO2into water at cell surfaces caused additional (strongly temperature dependent) resistance which accounted for 36% of the total resistance in the base case.
Vocal identification of individual African Wood Owls Strix woodfordii: a technique to monitor long‐term adult turnover and residency
Authors: Delport Wayne , Kemp Alan C. , Ferguson J. Willem H. 
Published: March 2003

The hoot‐calls of Wood Owls Strix woodfordii, recorded in the Kruger National Park, South Africa, from 1986 to 1998, are sufficiently different to distinguish individuals. Thirteen hoot‐call variables, measured from recordings over this period, show that male and female Wood Owls have such temporal stability that these calls can be used reliably as a long‐term census technique. manova, based on ordinations from principal component analysis, was used to identify individuals statistically between sampling periods. A forward stepwise discriminant function analysis achieved 100% classification success of individual male (n = 3) and female (n = 4) owls from a single sampling period. For all the individuals recorded over the whole study period we achieved a classification success of 80.9% (n = 9) for male hoot calls and of 96.3% (n = 13) for female calls. We found mean occupation periods of 82.25 and 65 months and annual turnover rates of 19.3% and 13.65% for males and females, respectively. Our survey, using vocalizations, is unique since we use data collected over a 12‐year period to derive estimates of population turnover in Wood Owls, and consider what questions can be addressed in similar studies.
Macrophages present exogenous antigens by class I major histocompatibility complex molecules via a secretory pathway as a consequence of interferon‐γ activation
Authors: Martín‐Orozco Natalia , Isibasi ArMando , Ortiz‐Navarrete Vianney 
Published: March 2003

SummaryMacrophages can process and present exogenous antigens on major histocompatibility complex (MHC) class I molecules through an alternative mechanism involving the internalization of antigens and the secretion of peptides loading MHC class I molecules at the cell surface. In this paper, we found that interferon‐γ (IFN‐γ) ‐activated macrophages infected with Salmonella typhimurum secreted peptides able to load empty MHC Kb molecules on co‐cultured TAP‐2‐deficient RMA‐S cells, added as targets for peptide loading. The increase in class I Kb on the RMA‐S cells, resulting from the macrophage‐derived peptides, exhibited a comparable stability as the direct addition of an exogenous Kb‐binding peptide (OVA257–264) to the RMA‐S cells. In both cases, the Kb complexes were stable for at least 3 hr after separating the RMA‐S cells from the macrophages. The endosomal inhibitors, leupeptin and ammonium chloride, did not inhibit the release of peptides and the increase in Kb staining on the RMA‐S cells in the co‐culture systems. Brefeldin A also had no effect. P815 cells previously co‐cultured with Salmonella‐infected macrophages became targets for cytotoxic T lymphocytes isolated from Salmonella‐infected BALB/c mice. Taken together, our data suggest that IFN‐γ‐activated macrophages process exogenous antigens in an intracellular compartment where serine proteases generate peptides released to the external environment for loading empty MHC class I molecules at the cell surface. This TAP‐independent mechanism for the MHC class I presentation may be involved in priming cytotoxic T lymphocytes against intracellular pathogens in vivo.
Epithelial cells respond to proteolytic and non‐proteolytic detachment by enhancing interleukin‐6 responses
Authors: Miller Tabbi L. , McGee Dennis W. 
Published: March 2003

SummaryIntestinal inflammatory disease or infection often results in the loss of the epithelial layer as a result mainly of the action of proteases, including the leucocyte serine proteinases (neutrophil elastase), lysosomal cathepsins and the matrix metalloproteinases from recruited inflammatory cells. Previous studies have shown that bronchial or intestinal epithelial cells (IEC) can respond to proteolytic attack by producing cytokines. In this study, we have determined the effect of protease treatment on interleukin‐6 (IL‐6) and monocyte chemoattractant protein‐1 (MCP‐1) production by IEC lines. Both neutrophil elastase and trypsin treatment induced elevated levels of mRNA for IL‐6 in rat IEC‐6 cells. Non‐proteolytic detachment of the IEC‐6 cells also induced elevated levels of IL‐6 mRNA, suggesting that the effect was not caused by a specific protease or degradation product, but probably by an effect on cell shape or cell detachment. Similar results were seen with the IEC‐18 cell line. Trypsin treatment of the IEC‐6 cells also enhanced unstimulated and IL‐1β costimulated IL‐6 secretion, but not MCP‐1 secretion or mRNA levels. Finally, nuclear levels of the CCAAT/enhancer binding protein‐β (C/EBP‐β) were rapidly enhanced after proteolytic detachment of the IEC‐6 cells, suggesting a mechanism for the enhancement of IL‐6 mRNA responses. These data indicate that epithelial cells can respond to proteolytic attack or cell detachment by producing IL‐6, a cytokine with several anti‐inflammatory and antiprotease effects, which may be important in moderating the loss of the epithelial layer by its effects on nearby epithelial or inflammatory cells.
Conditional ablation of T‐cell development by a novel viral ion channel transgene
Authors: Smith Claire A. , Graham Christine M. , Mathers Kathleen , Skinner Anita , Hay Alan J. , Schroeder Cornelia , Thomas D. Brian 
Published: March 2003

SummaryA novel conditional‐lethal transgene system is defined in which a mutated influenza A virus ion‐channel protein, which is permeable to monovalent cations, is lethal to cells on heterotypic expression and whose activity can be blocked by an antiviral drug (amantadine), is used to reversibly disrupt T‐cell development. In vivo expression of the M2 ion channel, as a transgene under control of the T‐cell specific p56Lck proximal promoter, resulted in total ablation of T‐cell development with the accumulation of three distinct populations of early progenitor cells (CD44+ CD25−; CD44+ CD25+; CD44+ CD25hi) in the thymic rudiment. In vitro development of transgenic fetal thymic progenitors to single‐positive T cells could be rescued by antiviral drug treatment. Moreover, there was a radical reduction in B‐cell lymphopoiesis, evident at the pre‐B‐cell stage, with a twofold increase of lymphoid cells ‘in cycle’ in transgenic bone marrow, indicative of major changes in haematopoietic homeostasis. This system may provide a generic protocol for conditional, lineage‐specific cell ablation with available tissue‐specific promoters for any eukaryotic developmental system, and provide a window on early T‐cell development.
Predominant neuronal B‐cell loss in L5 DRG of p75 receptor‐deficient mice
Authors: Dreetz Gjerstad M. , Tandrup T. , Koltzenburg M. , Jakobsen J. 
Published: March 2003

AbstractThe significance of the p75 low‐affinity neurotrophin receptor, for the maintenance and survival of DRG cells, was studied in p75‐deficient mice. Perikarya of the L5 DRG of 12‐week‐old p75 receptor‐deficient mice and healthy Balb C mice were compared using stereological techniques. Following systematic sampling, the optical fractionator and the planar vertical rotator were used to estimate the number and mean volume of the cell bodies of the two neuronal subpopulations. The loss of B‐cells was 57% (P < 0.00001), numbers being 7300 (CV = 0.12) in controls and 3100 in p75 receptor‐deficient mice (CV = 0.18). Also, A‐cells showed a significant loss of 39% (P < 0.0001), numbers being 2600 (CV = 0.12) in control mice and 1500 (CV = 0.16) in p75 receptor‐deficient mice. The volume of A‐cells was reduced by 30% (P < 0.01), from 24.700 µm3 (CV = 0.17) perikarya in p75 knock‐out mice to 15.100 µm3 (CV = 0.17) in controls. B‐cell volume did not change significantly. It is concluded that the p75 receptor plays a major role in the survival of DRG cells. The predominant loss of small B‐cells indicates that the effect of neurotrophins is dependent upon the presence of the p75 low‐affinity receptor.
The transcription factor cSox2 and Neuropeptide Y define a novel subgroup of amacrine cells in the retina
Authors: Le Rouëdec D. , Rayner K. , Rex M. , Wigmore P. M. , Scotting P. J. 
Published: March 2003

AbstractThe retina has been extensively used as a model to study the mechanisms responsible for the production of different neural cell phenotypes. The importance of both extrinsic and intrinsic cues in these processes is now appreciated and numerous transcription factors have been identified which are required for both neuronal determination and cell differentiation. In this study we have analysed the expression of the transcription factor Sox2 during development of the chick retina. Expression was found in the proliferating cells of the retina during development and was down regulated by nearly all cell types as they started to differentiate and migrate to the different layers of the retina. In one cell type, however, Sox2 expression was retained after the cells have ceased division and migrated to their adult location. These cells formed two rows located on either side of the inner plexiform layer and were also positive for Neuropeptide Y, characteristics which indicate that they were a subpopulation of amacrine cells. The expression of Sox2 by only this population of post‐mitotic neurones makes it possible to follow these cells as they migrate to their adult location and shows that they initially form a single row of cells which subsequently divides to form the double row seen in the adult tissue. We suggest that retained expression of Sox2 is involved in directing the differentiation of these cells and is an early marker of this cell type.
Monolateral hypoplasia of the motor vagal nuclei in a case of sudden infant death syndrome
Authors: Macchi Veronica , Snenghi Rossella , De Caro Raffaele , Parenti Anna 
Published: March 2003

AbstractDuring the development of motor vagal nuclei (MVN), the neuroblasts of the myeloencephalic basal plate migrate in the dorsolateral direction to form the dorsal motor vagal nucleus (DMVN) and ventrolaterally to form the ventral motor vagal nucleus (VMVN). Those neuroblasts that remain close to the median sulcus will form the hypoglossal nucleus. In support of the congenital origin of the alteration of the MVN in sudden infant death syndrome (SIDS), we report the case of an 8‐month‐old female child who was found dead in her cot. The neuropathological assessment revealed that the medullary triangle of the 4th ventricle floor was asymmetric, owing to the presence of three prominences to the left side of the median sulcus. The medial prominence corresponded to the hypoglossal nucleus, which showed a marked increase in the number of large neurons; the intermediate prominence corresponded to the DMVN whose large neurons were reduced and were recognizable mainly at the level of the medial fringe; the lateral prominence corresponded to the solitary nucleus. The left solitary tract showed a reduction of the transverse diameter. Also, the left VMVN showed marked reduction in the number of neurons. Inflammatory and astrocytic reactions were absent. We suggest that in SIDS cases the hypocellularity of the MVN and the increased number of neurons of the hypoglossal nucleus are intimately related, indicating a congenital alteration due to incomplete migration of the vagal neuroblasts with abnormality of the autonomic cardio‐respiratory control.