bluuebunny/crossref_metadata_2025_split huggingface dataset:
The evolution of electron image processing and its potential debt to image algebra
Authors: Hawkes P. W. 
Published: March 2003

The types of digital electron microscope image processing of greatest interest are not the same in the three major types of electron microscope. In the TEM, electron tomography and crystallography, particularly for 3‐D reconstruction of biological specimens, and procedures that enable the physicist to establish the atomic structure, and especially defects in crystalline material, from one or more of a host of different records — bright‐ and dark‐field images, traditional or convergent‐beam diffraction patterns, energy‐loss spectra, holograms — have attracted the greatest attention. In the SEM, image enhancement and image analysis (counting and measurement of geometrical or compositional features of the image) have always been important and the earliest attempts to process SEM images were in these fields. In the STEM, it is the possibility of using all the information in the far‐field diffraction pattern from every element of the object that has provoked the most exciting and original ideas.Electron images began to be processed by computer or by analog means just 30 years ago and during those years, images of every kind have likewise been enhanced or restored or analysed: in astronomy and medicine, in forensic science and in agriculture, in textile studies and the geosciences, similar algorithms have been developed, often with little awareness of related work. In order to harmonize all this material, an attempt to find a common language for representing it has been sought and the result is ‘image algebra’. This is a simple mathematical structure in which the basic element is not the pixel value but the image, which is a general notion: an array, the elements of which may be real or complex numbers or one‐ or two‐dimensional arrays of such numbers. An image whose pixel values are themselves images plays a very important part and is referred to as a ‘template’.We show how the various image processing algorithms that have been found useful in electron microscopy can be expressed in terms of this algebra. Moreover, image algebra is not merely a convenient way of representing these algorithms; its simplicity and conciseness make it easy to recognize generalizations and variants of the original procedures. We draw attention to some of these and point out promising directions for future work, including the use of a new transform, the ‘slope transform’, for interpreting scanning tunnelling microscope images.
Probability estimations for fitted parameters — the EXPHER package
Authors: Taupin D 
Published: March 2003

The general problem of fitting unknown parameters to experimental data is addressed in terms of probability laws, that is, answering the fundamental question: ‘what is the probability law of the various unknowns, knowing the data yielded by the experiments?’ The question appears to be an inverse problem whose solution is simple in theory, but whose practical implementation is so difficult that many an experimentalist reverts to heuristic methods of questionable reliability.As an alternative solution, a freeware computer package — EXPHER — is presented which performs most of the tedious work involved in rigorous treatments, including related algebraic calculus.
Local variations of the chemistry in as‐cast γ‐TiAl (TiBx) alloys and its consequence for thermomechanical treatments
Authors: Sternitzke  , Appel  , Wagner  
Published: March 2003

The first part of the paper presents an accompanying investigation to a thermomechanical processing route of γ‐TiAl turbine blades. By means of scanning electron microscopy and energy dispersive X‐ray (EDX) analysis, the chemical homogeneity and the microstructures of γ‐TiAl as‐cast ingots, work pieces and the final turbine blades are determined. We find that the local Al‐content in as‐cast ingots can vary by more than 1.5 at.%. Large chemical inhomogeneities present in as‐cast ingots can only be eliminated to a certain degree by subsequent thermomechanical processing. An additional aim of the study is to assess the influence of a thermomechanical processing on the morphology of titanium boride precipitates and the α2‐Ti3Al‐phase.The second part of the paper contains a detailed analytical study devoted to homogenization of a range of γ‐TiAl cast alloys. Different microstructures are generated in a laboratory‐scale argon‐arc furnace by both rapid and slow solidification rates and an additional homogenization treatment, respectively. Quantitative EDX analysis shows that only rapid solidification of ingots with a subsequent homogenization treatment leads to a nearly chemically homogeneous microstructure.
Assessment of chloride secretion in human nasal epithelial cells by X‐ray microanalysis
Authors: Dragomir A. , Andersson C. , Åslund M. , Hjelte L. , Roomans G. M. 
Published: March 2003

The genetic disease cystic fibrosis (CF) is due to defective epithelial chloride transport. Different treatments have been proposed that could restore chloride transport in CF patients. A new method is proposed for measuring the chloride secretion in easily accessible epithelial cells.Fresh nasal epithelial cells were obtained by nasal brushing and made to attach to titanium grids for electron microscopy. Chloride efflux through the cystic fibrosis transmembrane regulator channel was stimulated by 20 µm forskolin and 100 µm isobutyl‐methylxanthine (IBMX), in standard Ringer's solution (SR). Chloride efflux through the calcium‐regulated channel was stimulated by 200 µm adenosine triphosphate (ATP) in SR. The cells were rinsed after the exposure, in order to remove the experimental medium, frozen and freeze‐dried. The elemental composition of the cells was determined by X‐ray microanalysis.Rinsing with distilled water or ammonium acetate appeared to cause damage to the cells, whereas rinsing with isotonic mannitol preserved the ionic composition. Stimulation of cells from healthy controls with forskolin and IBMX in a chloride‐containing medium caused a significant (28 ± 6%) decrease in chloride concentration, which is indicative of net chloride efflux. In similar conditions, stimulation with ATP induced a 29 ± 5% decrease in the chloride concentration.Stimulation of cells from CF patients with forskolin and IBMX in a chloride‐containing medium caused no significant change in the intracellular chloride concentration, whereas ATP stimulation induced a response similar to that obtained in cells from healthy controls.It is concluded that X‐ray microanalysis of nasal epithelial cells may be used to determine chloride secretion in CF patients in an easily accessible cell type.
Evaluation of global analysis algorithms for single frequency fluorescence lifetime imaging microscopy data
Authors: Verveer P. J. , Bastiaens P. I. H. 
Published: March 2003

SummaryGlobal analysis of fluorescence lifetime image microscopy (FLIM) data can be used to obtain an accurate fit of multi‐exponential fluorescence decays. In particular, it can be used to fit a bi‐exponential decay to single frequency FLIM data, which is not possible with conventional fitting techniques. Bi‐exponential fluorescence decay models can be used to analyse quantitatively single frequency FLIM data from samples that exhibit fluorescence resonance energy transfer (FRET). Global analysis algorithms simultaneously fit multiple measurements acquired under different experimental conditions to achieve higher accuracy. To demonstrate that bi‐exponential models can indeed be fitted to single frequency data, we derive an analytical solution for the special case of two measurements and use this solution to illustrate the properties of global analysis algorithms. We also derive a novel global analysis algorithm that is optimized for single frequency FLIM data, and demonstrate that it is superior to earlier algorithms in terms of computational requirements.
Labelling quality and chromosome morphology after low temperature FISH analysed by scanning far‐field and near‐field optical microscopy
Authors: Winkler R. , Perner B. , Rapp A. , Durm M. , Cremer C. , Greulich K.‐O. , Hausmann M. 
Published: March 2003

SummaryA non‐enzymatic, low temperature fluorescence in situ hybridization (LTFISH) procedure was applied to metaphase spreads and interphase cell nuclei. In this context ‘low temperature’ means that the denaturation procedure of the chromosomal target DNA usually applied by heat treatment and chaotropic agents such as formamide was completely omitted so that the complete hybridization reaction took place at 37 °C. For LTFISH, the DNA probe had to be single‐stranded, which was achieved by means of separate thermal denaturation of the DNA probe only. The DNA probe pUC1.77 was used for all LTFISH experiments. The labelling quality (number of binding sites, relative background intensity, relative intensity of major and minor binding sites) was analysed by confocal laser scanning microscopy (CLSM). An optimum in specificity and signal quality was obtained for 15 h hybridization time. For this hybridization condition of LTFISH, the chromosomal morphology was analysed by scanning near‐field optical microscopy (SNOM). The results were compared with the morphology of chromosomes after (a) labelling of all centromeres using the same chemical treatment in the FISH procedure but with the application of target denaturation, and (b) labelling of all centromeres using a standard FISH protocol including thermal denaturation of the DNA probe and the chromosomal target. Depending on the FISH‐procedure applied, SNOM images show substantial differences in the chromosome morphology. After LTFISH the chromosome morphology appeared to be much better preserved than after standard FISH. In contrast, the application of the LTFISH chemical treatment accompanied by heat denaturation had a very destructive influence on chromosomal morphology. The results indicate that, at least for certain DNA probes, specific chromosome labelling can be obtained without the usually applied heat and chemical denaturation of the DNA target, resulting in an apparently well preserved chromatin morphology as visualized by SNOM. LTFISH may be therefore a useful labelling technique whenever the chromosomal morphology had to be preserved after specific labelling of DNA regions. Binding mechanisms of single‐stranded DNA probes to double‐stranded DNA targets are discussed.
Ontogeny of Aromatase and Tyrosine Hydroxylase Activity and of Aromatase‐Immunoreactive Cells in the Preoptic Area of Male and Female Japanese Quail
Authors: Balthazart J. , Tlemçani O. , Harada N. , Baillien M. 
Published: March 2003

AbstractThe aromatization of testosterone into oestrogens plays a key role in the control of many behavioural and physiological aspects of reproduction. In the quail preoptic area (POA), aromatase activity and the number of aromatase‐immunoreactive (ARO‐ir) cells are sexually differentiated (males > females). This sex difference is implicated in the control of the sexually dimorphic behavioural response of quail to testosterone. We analysed the ontogenetic development of this sex difference by measuring aromatase activity and counting ARO‐ir cells in the POA of males and females from day 1 post hatch to sexual maturity. We investigated in parallel another enzyme: tyrosine hydroxylase, the rate limiting step in catecholamine synthesis. Between hatching and 4 weeks of age, aromatase activity levels were low and equal in males and females. Aromatase activity then markedly increased in both sexes when subjects initiated their sexual maturation but this increase was more pronounced in males so that a marked difference in aromatase activity was present in 6 and 8 week‐old subjects. Tyrosine hydroxylase activity progressively increased with age starting immediately after hatching and there was no abrupt modification in the slope of this increase when birds became sexually mature. No sex difference was detected in the activity of this enzyme. The number of ARO‐ir cells in the POA progressively increased with age starting at hatching. No sex difference in ARO‐ir cell numbers could be detected before subjects reached full sexual maturity. The analysis of the three‐dimensional organization of ARO‐ir cells in the POA revealed that, with increasing ages, ARO‐ir cells acquire a progressively more lateral position: they are largely periventricular in young birds but they are found at higher density in the lateral part of the medial preoptic nucleus in adults. These data indicate that aromatase activity differentiates sexually when birds reach sexual maturity presumably under the activating effects of the increased testosterone levels in males. The number of ARO‐ir cells, however, begins to increase in a non sexually differentiated manner before the rise in plasma testosterone in parallel with the increased tyrosine hydroxylase activity. Whether this temporal coincidence results from a general ontogenetic pattern or from more direct causal links remains to be established.
Seasonal Changes in the Expression of Neuropeptide Y and Pro‐Opiomelanocortin mRNA in the Arcuate Nucleus of the Ovariectomized Ewe: Relationship to the Seasonal Appetite and Breeding Cycles
Authors: Clarke I. J. , Scott C. J. , Rao A. , Pompolo S. , Barker‐Gibb M. L. 
Published: March 2003

AbstractSheep experience well‐documented seasonal changes in reproductive activity and voluntary food intake (VFI). Within the hypothalamus, neurones that express neuropeptide Y (NPY) and pro‐opiomelanocortin (POMC) have been implicated in the regulation of reproduction and appetite. In this study, we aimed to determine the extent to which the expression of these two neuronal systems is linked to the seasonal reproductive cycle and/or the seasonal appetite cycle. VFI in our sheep reaches a nadir in August with no difference occurring between December and February. We examined the brains of ovariectomized (OVX) female sheep (n = 5–7) that were killed during the breeding season (February) or during the early or late nonbreeding season (August and December, respectively). The brains of these animals were perfused with paraformaldehyde and processed for in situ hybridization histochemistry, using ribonucleotide probes labelled with 35S. The number of NPY and POMC cells and the number of silver grains per cell were counted using an image analysis system. For NPY, the number of cells counted in the arcuate nucleus/median eminence region and the number of silver grains per cell was significantly lower in animals killed during August than in animals killed in February or December. The number of grains per cell over NPY cells was also significantly lower in animals killed during August. For POMC, the number of cells was lower in February than in August and December. Similarly, the number of grains per cell for POMC were lower in February than in August and December. VFI was significantly lower in animals during August than at other times of the year. We conclude that in OVX ewes: (i) NPY gene expression is lower at the time of the year when VFI is reduced and (ii) POMC gene expression is greater at the time of the nonbreeding season than during the breeding season. Because these results were obtained in OVX animals, the changes appear to be independent of alterations in the secretion and/or action of ovarian steroids. Thus, the activity of NPY neurones appears to relate to changes in appetite whereas changes in POMC expression may be relevant to the seasonal breeding cycle.
Androgens Alter Corticotropin Releasing Hormone and Arginine Vasopressin mRNA Within Forebrain Sites Known to Regulate Activity in the Hypothalamic‐Pituitary‐Adrenal Axis
Authors: Viau V. , Soriano L. , Dallman M. F. 
Published: March 2003

AbstractTo reveal direct effects of androgens, independent of glucocorticoids, we studied the effects of gonadectomy (GDX) in adrenalectomized (ADX) rats with or without androgen replacement on corticotropin releasing hormone (CRH) and arginine vasopressin (AVP) mRNA expression within various forebrain sites known to regulate the hypothalamic‐pituitary‐adrenal axis. These included the medial parvocellular portion of the paraventricular nucleus of the hypothalamus (mp PVN), the central and medial nuclei of the amygdala and bed nuclei of the stria terminalis (BNST). In the mp PVN, ADX stimulated both CRH and AVP mRNA expression. Combined ADX + GDX inhibited only AVP, and testosterone and dihydrotestosterone (DHT) restored AVP mRNA. In the central nucleus of the amygdala, ADX decreased CRH mRNA expression, and this response was unaffected by GDX ± testosterone or DHT replacement. In the medial amygdala, AVP mRNA expression was decreased by ADX, abolished by ADX + GDX, and restored by androgen replacement. ADX had no effect on CRH and AVP mRNA expression in the BNST. GDX + ADX, however, reduced CRH mRNA expression only within the fusiform nuclei of the BNST and reduced the number of AVP‐expressing neurones in the posterior BNST. Androgen replacement reversed both responses. In summary, in ADX rats, AVP, but not CRH mRNA expression in the amygdala and mp PVN, is sensitive to GDX ± androgen replacement. Both CRH‐ and AVP‐expressing neurones in the BNST respond to GDX and androgen replacement, but not to ADX alone. Because androgen receptors are not expressed by hypophysiotropic PVN neurones, we conclude that glucocorticoid‐independent, androgenic influences on medial parvocellular AVP mRNA expression are mediated upstream from the PVN, and may involve AVP‐related pathways in the medial amygdala, relayed to and through CRH‐ and AVP‐expressing neurones of the BNST.
The Role of Neuropeptide Y in Orexin‐Induced Hypothalamic‐Pituitary‐Adrenal Activation
Authors: Jászberényi M. , Bujdosó E. , Telegdy G. 
Published: March 2003

AbstractThe role of neuropeptide Y (NPY) in the mediation of orexin‐induced hypothalamic‐pituitary‐adrenal (HPA) activation was investigated in the rat. The HPA system was stimulated by intracerebroventricular (i.c.v.) administration of orexin‐A or orexin‐B (140 or 280 pmol, respectively) and the plasma concentration of corticosterone was used as an index of the degree of activation. i.c.v. pretreatment with NPY antagonist or NPY antiserum (30 min or 24 h before orexin administration, respectively) inhibited the orexin‐induced corticosterone release. The inhibitory actions of the antagonist and the antiserum were revealed by the dose–response curve; the highest concentrations practically abolished the HPA activation evoked by the orexins. These data suggest that the HPA system‐stimulating effect of the orexins may be mediated by NPY.
Hypothalamic Transforming Growth Factor β1 and Basic Fibroblast Growth Factor mRNA Expression is Modified During the Rat Oestrous Cycle
Authors: Galbiati M. , Magnaghi V. , Martini L. , Melcangi R. C. 
Published: March 2003

AbstractThe present observations show that the mRNA levels of two growth factors, previously described to be involved in the control of neurones synthesizing the luteinizing hormone releasing hormone (LHRH) [i.e. transforming growth factor β1 (TGFβ1) and basic fibroblast growth factor (bFGF)], fluctuate in the hypothalamus of adult female rats during the oestrous cycle. In particular, the expression of TGFβ1‐mRNA shows a peak on the morning of the day of proestrus, which precedes the increased secretion of the two gonadotrophins that occurs on that day. In the case of bFGF, the peak is evident in the evening of the same day and is concomitant with that of the gonadotrophins. We evaluated the effects of ovariectomy and of exogenous oestrogens on the mRNA levels of these two growth factors in the hypothalamus. The data indicate that 3 weeks of ovariectomy are not able to change the hypothalamic messenger levels of the two growth factors considered, which remain at the levels found in diestrus 1, and that 17β‐oestradiol is able to induce a significant increase of both TGFβ1‐ and of bFGF‐mRNA levels in the hypothalamus of the ovariectomized rat. The present in vivo observations support the concept, previously proposed on the basis of in vitro data, that growth factors, such as TGFβ1 and bFGF, play a role in the hypothalamic control of reproduction, and suggest that the control of LHRH dynamics involves a strict cooperation between gonadal steroids and growth factors.
High Voltage‐Activated Ca2+ Currents in Rat Supraoptic Neurones: Biophysical Properties and Expression of the Various Channel α1 Subunits
Authors: Joux N. , Chevaleyre V. , Alonso G. , Boissin‐Agasse L. , Moos F. C. , Desarménien M. G. , Hussy N. 
Published: March 2003

AbstractThe diversity of Ca2+ currents was studied in voltage‐clamped acutely dissociated neurones from the rat supraoptic nucleus (SON), and the expression of the various corresponding pore‐forming α1 subunits determined by immunohistochemistry. We observed the presence of all high voltage‐activated L‐, N‐, P/Q‐ and R‐type currents. We did not observe low‐voltage‐activated T‐type current. The multimodal current/voltage relationships of L‐ and R‐type currents indicated further heterogeneity within these current types, each exhibiting two components that differed by a high (−20 mV) and a lower (−40 mV) threshold potential of activation. L‐ and R‐type currents were fast activating and showed time‐dependent inactivation, conversely to N‐ and P/Q‐type currents, which activated more slowly and did not inactivate. The immunocytochemical staining indicated that the soma and proximal dendrites of SON neurones were immunoreactive for Cav1.2, Cav1.3 (forming L‐type channels), Cav2.1 (P/Q‐type), Cav2.2 (N‐type) and Cav2.3 subunits (R‐type). Each subunit exhibited further specificity in its distribution throughout the nucleus, and we particularly observed strong immunostaining of Cav1.3 and Cav2.3 subunits within the dendritic zone of the SON. These data show a high heterogeneity of Ca2+ channels in SON. neurones, both in their functional properties and cellular distribution. The lower threshold and rapidly activating L‐ and R‐type currents should underlie major Ca2+ entry during action potentials, while the slower and higher threshold N‐ and P/Q‐type currents should be preferentially recruited during burst activity. It will be of key interest to determine their respective role in the numerous Ca2+‐dependent events that control the activity and physiology of SON neurones