bluuebunny/crossref_metadata_2025 huggingface dataset:
Targeted Cytotoxic Analogue of Luteinizing Hormone‐Releasing Hormone (LH‐RH) Only Transiently Decreases the Gene Expression of Pituitary Receptors for LH‐RH
Authors: Kovacs M. , Schally A. V. , Csernus B. , Busto R. , Rekasi Z. , Nagy A.
Published: March 2003

A cytotoxic analogue of LH‐RH, AN‐207, consisting of 2‐pyrrolinodoxorubicin (AN‐201) linked to carrier [D‐Lys6]LH‐RH, was developed for targeted therapy of cancers expressing LH‐RH‐receptors. To determine its possible side‐effects on the pituitary gland, we investigated the gene expression of pituitary LH‐RH‐receptors and LH secretion in ovariectomized female and normal male rats after treatment with the maximum tolerated dose of AN‐207. The effect of AN‐207 on the gene expression of the pituitary GH‐RH‐receptors and GH secretion was also assessed in male rats. Five hours after a single i.v. injection of AN‐207 at 175 nmol/kg, there was a 39–51% decrease in mRNA expression for the pituitary LH‐RH‐receptors in male and female rats. The carrier, at an equimolar dose, caused a similar reduction (37–39%), whereas the cytotoxic radical AN‐201, at an equitoxic dose (110 nmol/kg), produced only a 12–24% decrease (NS) in the mRNA expression of LH‐RH‐receptors. AN‐207 and the carrier analogue induced a comparable 90–100‐fold increase in serum LH concentrations in male rats, and the same 12‐fold elevation in OVX rats at 5 h. Seven days after treatment with AN‐207, the mRNA levels for the LH‐RH receptors and the serum LH concentration were back to normal in both sexes. AN‐207, the carrier, and AN‐201 had no significant effect on the expression of mRNA for GH‐RH‐receptors in the pituitary. In vitro, a continuous perfusion of pituitary cells with 10 nM AN‐207 did not affect the hormone‐releasing function of the targeted LH cells or the nontargeted GH cells. Our results demonstrate that cytotoxic LH‐RH analogue AN‐207, at the maximum tolerated dose causes only a transient decrease in the gene expression of the pituitary LH‐RH receptors, and the levels of mRNA for LH‐RH receptor fully recover within 7 days. Moreover, the carrier hormone moiety, and not the cytotoxic radical in AN‐207 is responsible for this transient suppression. Our findings suggest that the therapy with cytotoxic LH‐RH analogues will not inflict permanent damage to pituitary function.
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

Siberian 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

The 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

The 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

The 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

Desiccation 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

In 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

The 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

A 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.
Sex ratio comparisons between nestlings and dead embryos of the Sparrowhawk Accipiter nisus
Authors: Van Den Burg A. B. , Van Diermen J. , Müskens G. J. D. M. , Van Rijn S. , Zollinger R.
Published: March 2003

Sex ratios that differ from unity have been reported for several bird species, but are poorly understood. Skewed sex ratios may originate at ovulation (primary sex ratio) or arise through differential mortality between the sexes (secondary sex ratio). To estimate the primary sex ratio from nestlings is difficult because in some nests not all the offspring can be sexed. Both when including and excluding such nests, there is a risk of overestimating the proportion of the better‐surviving sex. Here we sexed dead Sparrowhawk embryos to determine whether unhatched eggs affect primary sex ratio estimates that are based on nestling data. In nests in which embryo mortality occurred, there was up to a 9% discrepancy in the primary sex ratio estimates based on nestlings alone compared to nestlings and dead embryos together. There was no evidence that these differences were based on sex‐specific causes of mortality of embryos.
Moult strategies in the Common Whitethroat Sylvia c. communis in northern Nigeria
Authors: Waldenström Jonas , Ottosson Ulf
Published: March 2003

Moult strategies in the Common Whitethroat Sylvia c. communis trapped in northern Nigeria in April 1999 are analysed. Differences in the extent of moult between age and sex classes are presented. The secondary moult of adult birds is considered to belong to a new pre‐breeding moult or an arrested moult, beginning at the normal starting positions on the wing, and not as a continuation of a suspended post‐breeding moult. Eccentric moult of primaries was found in nearly 19% of the yearling birds, a pattern that is unusual for Western Palearctic passerines. Some individuals showed resemblance to the split moult pattern described for the Barred Warbler S. nisoria.
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

Macrophages 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

Intestinal 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

A 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

The 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

The 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

During 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.
Early detection of declining populations using floor and ceiling models
Authors: Kshatriya Mrigesh , Cosner Chris , Van Jaarsveld Albert S.
Published: March 2003

Within Caughley’s (1994) declining population paradigm for conservation, we develop a realistic method of detecting population changes using floor and ceiling population models.

A theoretical framework for detecting declining populations is presented and applied to four ungulate species from Kruger National Park, South Africa.

Census data are fitted to a non‐linear autoregressive population model. Based on this model two auxiliary models, called the floor and ceiling models, are derived. These models predict the upper and lower threshold densities (or abundance values) for the non‐linear population model.

Threshold floor and ceiling estimates can be used as a benchmark for monitoring population status. In particular, when abundance values (densities) tend to fall below the floor estimate, this may merit concern that a population is declining.

In conjunction with appropriate response by management, the presence of such an early warning system may prevent a population from becoming low in numbers, possibly making it less susceptible to stochastic processes and a less likely candidate for local extinction.
Community organization of tree species along soil gradients in a north‐eastern USA forest
Authors: Bigelow Seth W. , Canham Charles D.
Published: March 2003

A study was carried out in oak‐northern hardwood forest in NW Connecticut USA involving measurements of growth, light and soil environment of saplings of six canopy trees that are strongly associated with particular soil types as adults. The objectives were to determine patterns of growth response along soil factor gradients, and to discriminate among modes of community organization (fundamental niche differentiation, shifting competitive hierarchy or continuum concept).

Relationships were found between tree species distributions and all measured soil factors (pH and exchangeable calcium, magnesium, potassium, aluminium, ammonium and nitrate).

Growth and light data were fitted to a nested series of functions based on the Michaelis‐Menten equation. For five of six species, likelihood‐ratio tests indicated that functions that incorporated pH or other soil factors predicted growth better than functions based only on light availability.

Species differed in the direction and strength of response to soil factors. Fraxinus americana had decreased growth on high‐magnesium soils, Acer rubrum had increased growth on high‐aluminium soils, Quercus rubra and Fagus grandifolia had increased growth on high‐calcium soils and Tsuga canadensis had increased growth on high‐nitrate soils.

Growth responses were consistent with either fundamental niche differentiation and continuum concept (Acer rubrum), shifting competitive hierarchy and continuum concept (Fagus grandifolia, Quercus rubra and Tsuga canadensis) or were not consistent with any theory (Acer saccharum and Fraxinus americana).

Because saplings are associated with the same soil‐types as mature trees, further studies in this system should focus on earlier stages of the plant life cycle: dispersal, germination and seedling establishment.
Near field optical microscopy in aqueous solution: implementation and characterization of a vibrating probe
Authors: Mannelquist A. , Iwamoto H. , Szabo G. , Shao Z.
Published: March 2003

Near field optical microscopy (NSOM) is one of the possible solutions to circumvent the diffraction limit, but the control of the optical probe in solution has been a technical challenge for practical applications. Most recently, it has been shown that the pipette used in the scanning ion conductance microscope can be modified to form a high resolution near field optical probe. When combined with a novel distance modulation mechanism, a robust near field microscope can be constructed for operation in aqueous solution. In this paper, we present technical details of this design and a further characterization of the NSOM system for imaging in solution. Fundamental limitations of this approach in comparison to other systems are also discussed. Based on the current technology, it is concluded that better than 50 nm resolution should be achievable with this technique for fluorescence, as well as fluorescence resonance energy transfer, imaging of biological specimens.
Sequential induction of embryonic and adult forms of glutamic acid decarboxylase during in vitro‐induced neurogenesis in cloned neuroectodermal cell‐line, NE‐7C2
Authors: Varju Patricia , Katarova Zoya , Madarász Emília , Szabó Gábor
Published: March 2003

The expression of different forms of glutamate decarboxylases and GABA was investigated in the course of retinoic acid‐induced neuronal differentiation of NE‐7C2 cell‐line established from brain vesicles of 9‐day‐old mouse embryos lacking functional p53 gene. Non‐induced NE‐7C2 cells expressed embryonic GAD mRNAs with a low level of embryonic GAD25 protein and did not contain detectable amounts of GABA. Addition of 10−6m retinoic acid induced the expression of N‐tubulin and a significant increase in the level of embryonic GAD messages and GAD25 protein in early stage differentiating neurones. The enzymatically active embryonic GAD44 was detected at later stages of induction in neurone‐like cells and showed a maximum of expression at the time of neurite elongation and network formation. With the advance of neuronal maturation, the expression of embryonic forms declined while the adult GAD65 and GAD67 transcripts became dominant. GABA‐containing neurones were first demonstrated on the sixth day of induction coinciding with the peak of GAD44 expression and the beginning of GAD65 expression. The sequential induction of different GAD forms and the stage‐dependent GABA synthesis in NE‐7C2 cells is highly reminiscent of the temporal pattern found in vivo and suggests that these processes might be involved in the differentiation of neuronal progenitors.
Effects of serotine receptors agonists, TFMPP and CGS12066B, on regional serotonin synthesis in the rat brain: an autoradiographic study
Authors: Tohyama Yoshihiro , Yamane Fumitaka , Fikre Merid Maraki , Blier Pierre , Diksic Mirko
Published: March 2003

The effects of acute and repeat administration of the serotonin (5‐HT)1 agonists TFMPP [N‐(3‐trifluoromethyl)phenylpiperazine hydrochloride] and CGS12066B [7‐trifluoromethyl‐4‐ (4‐methyl‐1‐piperazinyl)pyrrolo[1,2‐a]‐quinoxaline dimaleate] were evaluated on 5‐HT synthesis rates using the α‐[14C]methyl‐l‐tryptophan (α‐MTrp) autoradiographic method. In the acute treatment study, TFMPP (10 mg/kg) and CGS12066B (5 mg/kg) were injected intraperitoneally 30 min before an α‐MTrp injection. In an acute study TFMPP reduced overall brain 5‐HT synthesis, in the dorsal and median raphe, and in almost all of their projection areas, with the exception of the parietal, sensory‐motor, and frontal cortices, the accumbens nucleus, and the caudate. Acute CGS12066B treatment did not have overall significant effect, but the rates did decrease in the cell body areas of 5‐HT neurons. In a 7‐day treatment with TFMPP (10 mg/kg/day) or CGS12066B (5 mg/kg/day), the 5‐HT synthesis rates (24 h after last dose) decrease, with both compounds, in almost all of the nerve terminal structures. TFMPP reduced the synthesis in the dorsal and median raphe, while CGS12066B reduced it only in the dorsal raphe. This data suggests that after a 7‐day treatment with TFMPP and CGS12066B, the rate of 5‐HT synthesis in the dorsal raphe is restored and is reduced in many projection areas. The observed effects in the 7‐day treatment could also be related to actions through the postsynaptic 5‐HT1B sites and/or other 5‐HT receptors since this compounds have limited selectivity.
Effects of estrogen treatment on glutamate uptake in cultured human astrocytes derived from cortex of Alzheimer's disease patients
Authors: Liang Zhe , Valla Jon , Sefidvash‐Hockley Sepideh , Rogers Joseph , Li Rena
Published: March 2003

Estrogen is thought to play a protective role against neurodegeneration through a variety of mechanisms including the activation of growth factors, the control of synaptic plasticity, and the reduction of response to various insults, such as iron and glutamate. Increasing evidence indicates an increased level of extracellular glutamate and a down‐regulation of glutamate transporters in Alzheimer's disease (AD). In this study, we show that glutamate uptake in astrocytes derived from Alzheimer's patients is significantly lower than that from non‐demented controls. Estrogen treatment increases glutamate uptake in a dose‐dependent pattern. Two glutamate transporters, GLT‐1 and GLAST, are expressed in the astrocytes. Up‐regulation of the glutamate transporters is induced by estrogen treatment in AD astrocytes only. Our data suggest that the action of estrogen on glutamate uptake by astrocytes might contribute to its potential neuroprotective role in AD.
A direct role of the homeodomain proteins Phox2a/2b in noradrenaline neurotransmitter identity determination
Authors: Seo Hyemyung , Hong Seok Jong , Guo Su , Kim Hee‐Sun , Kim Chun‐Hyung , Hwang Dong‐Youn , Isacson Ole , Rosenthal Arnon , Kim Kwang‐Soo
Published: March 2003

Development of noraderenergic (NA) neurons in the vertebrate brain is dependent on the homeodomain proteins Phox2a and 2b. Here, we show that Phox2a directly controls the NA identity by activating NA‐synthesizing dopamine β‐hydroxylase (DBH) gene. Single point mutations in the homeodomain of Phox2a resulted in a failure to transactivate the DBH promoter in vitro and resulted in the loss of NA neurons in vivo. In addition, injection of Phox2a‐specific antisense oligonucleotide induced the loss of NA neurons in developing zebrafish. Phox2a and 2b activate the DBH promoter and bind to three domains (PBD1–3). PBD1 is composed of two overlapping sites with which monomers of Phox2a can interact. In contrast, PBD2 and 3 interact with the dimeric form of Phox2a. Mutations in three or four, but not one or two, of the binding sites completely abolished activation of the DBH promoter by Phox2a or 2b, while the conversion of PBD3 to a consensus motif (ATTA) improved the DBH promoter activity by > 10‐fold. Taken together, these findings establish that Phox2a and 2b control the development of NA neurons in part by directly transactivating DBH transcription through interactions with four binding sites clustered in the proximal promoter.
Fra‐1 substitutes for c‐Fos in AP‐1‐mediated signal transduction in retinal apoptosis
Authors: Wenzel Andreas , Iseli Hans Peter , Fleischmann Alexander , Hafezi Farhad , Grimm Christian , Wagner Erwin F. , Remé Charlotte E.
Published: March 2003

Lack of the AP‐1 member c‐Fos protects photoreceptors against light‐induced apoptosis, a model for retinal degeneration. In mice, light damage increases the activity of the transcription factor AP‐1, while pharmacological suppression of AP‐1 prevents apoptosis, suggesting the involvement of pro‐apoptotic AP‐1 target genes. Recently, however, it was shown that photoreceptors expressing Fra‐1 in place of c‐Fos (FosFosl1/Fosl1) are apoptosis competent despite the lack of transactivation domains in Fra‐1. Here, we show that morphological features of light‐induced apoptosis were indistinguishable in FosFosl1/Fosl1 and wild‐type mice. Furthermore, light exposure comparably increased AP‐1 activity in both genotypes. Opposite to wild‐type mice, Fra‐1, but not c‐Fos, was detectable in AP‐1 complexes of FosFosl1/Fosl1 mice. Importantly, AP‐1 responsiveness for glucocorticoid receptor‐mediated inhibition was preserved in FosFosl1/Fosl1 mice. Thus, Fra‐1 takes over for c‐Fos in pro‐ and anti‐apoptotic signal transduction. As Fra‐1 lacks transactivation domains, AP‐1 may not induce, but rather suppress genes in retinal light damage.
Plant hormones and the control of physiological processes
Authors: Weyers Jonathan D. B. , Paterson Neil W.
Published: March 2003

This review examines contemporary views of the role of plant hormones in the control of physiological processes. Past and present difficulties with nomenclature encapsulate the problems inherent in using the ‘classic’ hormone concept in plants, with their distinctive multicellular organization. Chemical control may be a more relevant notion. However, control may also reside in the responding tissue via changes in sensitivity, or as combined control, where response is dictated by both sensitivity and concentration. Criteria for demonstrating these modes of action are reviewed, as well as frameworks for deciding whether hormone transport is involved. Problems of measuring relevant hormone concentrations are discussed. Methods for measuring and comparing tissue sensitivity to hormones are outlined and relative control is introduced as a means of assessing the importance of hormonal control against a background of other influences. While animals and plants appear to have coinherited homologueous intracellular signalling systems, at the whole organism level modes of hormone action may diverge. It is postulated that the synthesis‐transport‐action mechanism of action may be just one of several possible ways that phytohormones could control physiological processes. Twelve separate roles are discussed, and it is suggested that some of these could operate simultaneously to the plant’s advantage.ContentsSummary 375I.Introduction376II.The history of the hormone concept in plant systems376III.Issues of nomenclature380IV.The need for sound conceptual frameworks in plant hormone research382V.Development of criteria for chemical control384VI.Identification and quantitative analysis of plant hormones387VII.Hormone transport in plants389VIII.Hormone sensitivity and its quantification390IX.Roles of receptors, second messengers and signal amplification in hormone sensitivity changes393X.Relative control as a pivotal concept395XI.Diversity of physiological roles for chemical influences in plants397XII.Concluding remarks400Acknowledgements402References402
Limit Loads for Axially Loaded Cylinders Having Full Circumferential Cracks: Experimental, Analytical and Numerical Studies
Authors: Lynch M. A. , Moreton D. N. , Moffat D. G.
Published: March 2003

The limit load of an axially loaded cylinder, containing a fully circumferential part‐penetrating crack, has been established by three techniques. These were a stress analysis to find a lower bound to the limit load, a finite element analysis and an experimental programme which utilised extensively strain‐gauged precision‐made specimens. This article reports the results of these approaches and demonstrates the value of each.
Naturally acquired immunoglobulin (Ig)G subclass antibodies to crude asexual Plasmodium falciparum lysates: evidence for association with protection for IgG1 and disease for IgG2
Authors: Ndungu Francis M. , Bull Peter C. , Ross Amanda , Lowe Brett S. , Kabiru Ephantus , Marsh Kevin
Published: March 2003

There is longstanding evidence for a role of immunoglobulin (Ig)G in protection against malarial disease and infection. IgG1 and IgG3 have been shown to be particularly efficient at associating with monocytes in potentially protective mechanisms (i.e. antibody‐dependent cellular inhibition, opsonization and phagocytosis). Conversely, there is some evidence that IgG2 (and possibly IgG4) antibodies may be antagonistic to this protection. The protective effect of IgG subclass antibody activity present before the beginning of a malaria transmission season (preseason antibody levels) against severe malaria has not been tested in longitudinal studies. We measured IgG class and subclass antibody levels specific to crude Plasmodium falciparum lysates by enzyme linked immunosorbent assay in a case–control study of 76 children on the coast of Kenya. The mean optical density values for both IgG class and subclass antibodies were not significantly different between the children who developed severe malaria and those who remained healthy during an observation period of two malaria transmission seasons. However, elevated levels of IgG1 in relation to levels of IgG2 and IgG4 antibodies were associated with protection from severe malaria (P = 0·02). Conversely, elevated levels of IgG2 in relation to IgG1 and IgG3 antibodies were associated with a higher risk of developing severe malaria (P = 0·006).
Effect of three root canal sealers on the retentive strength of endodontic posts luted with a resin cement
Authors: Hagge M. S. , Wong R. D. M. , Lindemuth J. S.
Published: March 2003

Hagge MS, Wong RDM, Lindemuth JS. Effect of three root canal sealers on the retentive strength of endodontic posts luted with a resin cement. International Endodontic Journal, 35, 372–378, 2002.

Aim  This investigation examined what effect three different sealers had on retention of endodontic posts (Parapost) luted with a resin cement (Panavia 21 OP).

Methodology Sixty‐four single‐rooted teeth were decoronated, filed, cleaned, and shaped with a size 5 Gates–Glidden drill and 0.12 taper G.T. rotary instrumentation (Dentsply/Tulsa Dental). Teeth were then divided into four groups of 16 each. Group 1 was not obturated, and served as a control. The other three groups were obturated with gutta‐percha using a different sealer for each group. Group 2 used a eugenol containing sealer (Kerr Pulp Canal Sealer), group 3 a resin sealer (AH‐26), and group 4 a calcium hydroxide sealer (Sealapex). After 1 week’s storage at 100% humidity, 10‐mm deep post spaces were prepared with a size 6 Gates–Glidden drill, and size 5 Paraposts were cemented. Following 48 h of storage, samples were mounted in a PVC pipe with acrylic, and the posts were removed vertically using a universal testing machine at 1 mm min−, with data recorded in kilograms.

Results The mean values of force required to remove the posts were: group 1 = 61.80, SD = 16.21; group 2 = 43.14, SD = 14.66; group 3 = 48.54, SD = 17.84; group 4 = 53.52, SD = 18.77. Using anova and Bonferroni tests, group 1 demonstrated significantly greater mean retention strength values than group 2, but no other significant differences existed between groups.

Conclusion The chemical formulation of root canal sealers did not significantly affect the retention of endodontic posts luted with resin cement.
Endodontic implications of the maxillary sinus: a review
Authors: Hauman C. H. J. , Chandler N. P. , Tong D. C.
Published: March 2003

The anatomical and clinical significance of the maxillary sinus in relation to conventional and surgical endodontic therapy is considered. The discussion includes a review on the development, anatomy and physiology of the maxillary sinus, the diagnostic evaluation of the sinus and the differential diagnosis of sinusitis. Endodontic implications of the maxillary sinus include extension of periapical infections into the sinus, the introduction of endodontic instruments and materials beyond the apices of teeth in close proximity to the sinus and the risks and complications associated with endodontic surgery.