bluuebunny/crossref_metadata_2025_split huggingface dataset:
Retaining ionic concentrations during in vitro storage of tissue for microanalytical studies
Authors: HONGPAISAN J. , ROOMANS G. M. 
Published: March 2003

SummaryWhen human or animal tissue is to be investigated by X‐ray microanalysis, it is sometimes necessary to store the tissue between removal from the organism and freezing. However, when excised tissue is stored in buffer, the elemental concentrations in the cell may change. In the present study, it was attempted to develop a storage buffer that would retain the cellular elemental concentrations close to their in situ values. To start, the NaCl component in Krebs–Ringer buffer was exchanged for K‐gluconate and KCl for NaCl. This buffer was called a ‘100% high K+ solution’. Starting from this solution, part of the K‐gluconate was replaced by an equivalent amount of NaCl. Incubation of excised rat liver (4 °C, 4 h) in 85% high K+ solution resulted in retention of cellular Na, K, Ca, S and Mg concentration most closely to the in situ state, whereas cellular Cl was retained best when the tissue was incubated in 75% high K+ solution. For rat submandibular gland, incubation in 80% high K+ solution resulted in optimal retention of cellular Na, K, Ca, P, S and Mg, while Cl was retained best in a 70% high K+ solution. Based on these results, an optimally modified Krebs–Ringer solution for the liver

would consist of 119 mM K+, 26 mM Na+ and 45 mM Cl−. An optimally modified Krebs–Ringer bicarbonate solution for the submandibular gland would be composed of 96 mM K+, 53 mM Na+ and 46 mM Cl−. After incubation in the modified solutions (at 4 °C), cellular Na, Mg, S, Cl, K and Ca in both tissues were maintained close to the in situ state throughout a 6‐h incubation. The cellular P concentration was reduced after incubation for 1 h; thereafter, in the liver cells it remained at this lower level for the rest of the incubation, whereas in the submandibular gland tissue it increased again after 4 h. The increase in cell volume (oedema) was less in tissue stored in the modified solutions, than in the 100% high K+ solutions. Incubation in high Na+ buffers (4 °C, 6 h) resulted in a progressive increase in the percentage of cells showing trypan blue uptake. A similar increase in trypan blue uptake was seen in the modified solution, but this increase levelled off after 4 h. After cholinergic stimulation in high Na+ solution (25 °C, 1 min), the expected decrease in cellular Cl concentration was seen in submandibular gland cells that had previously been preserved (4 °C, 4 h) in the modified solution, but not in those that had been preserved in the 100% high K+ solution.
Sub‐wavelength region spectroscopy and local morphology of individual mesoscopic quantum systems
Authors: Vacha M. , Takei S. , Suzuki H. , Hashizume K.‐I. , Tani T. 
Published: March 2003

Results of reflection microscopy and local reflection spectroscopy of J‐aggregates of two pseudoisocyanine dyes in a thin film polymer matrix are reported. The individual J‐aggregates assemble into fibre‐like shapes of large structural heterogeneity. Reflectance spectra obtained at different samples, different locations on one sample and even at different positions of the same aggregate fibre reveal a wide distribution of optical properties. The shapes and absolute reflectivities of the spectra are suggested to originate from varying strengths of exciton–photon interaction and from the effect of finite thickness of the aggregate fibres. Polarization dependence measurements of local reflectivities provide orientations of the exciton transition dipole moments at 572 nm and 540 nm with respect to the orientation of the aggregate fibres. Furthermore, modified synthesis of capped semiconductor nanocrystals of CdSe is presented. The method yields high quality quantum dots suitable for microscopic imaging and spectroscopy.
Direct interpretation of near‐field optical images
Authors: Dereux A. , Devaux E. , Weeber J. C. , Goudonnet J. P. , Girard C. 
Published: March 2003

The interpretation of the detection process in near‐field optical microscopy is reviewed on the basis of a discussion about the possibility of establishing direct comparisons between experimental images and the solutions of Maxwell equations or the electromagnetic local density of states. On the basis of simple physical arguments, it is expected that the solutions of Maxwell equations should agree with images obtained by collecting mode near‐field microscopes, while the electromagnetic local density of states should be considered to provide a practical interpretation of illumination mode near‐field microscopes.We review collecting mode near‐field microscope images where the conditions to obtain good agreement with the solutions of Maxwell equations have indeed been identified. In this context of collecting mode near‐field microscopes, a fundamentally different functionality between dielectric and gold‐coated tips has been clearly identified experimentally by checking against the solutions of Maxwell equations. It turns out that dielectric tips detect a signal proportional to the optical electric field intensity, whereas gold‐coated tips detect a signal proportional to the optical magnetic field intensity. The possible implications of this surprising phenomenon are discussed.
Super‐resolution microscopy using normal flow decoding and geometric constraints
Authors: Danuser G. 
Published: March 2003

Prior knowledge about the observed scene provides the key to restoration of frequencies beyond the bandpass of an imaging system (super‐resolution). In conjunction with microscopy two super‐resolution mechanisms have been mainly reported: analytic continuation of the frequency spectrum, and constrained image deconvolution. This paper describes an alternative approach to super‐resolution. Prior knowledge is imposed through geometric and dynamic models of the scene. We illustrate our concept based on the stereo reconstruction of a micropipette moving in close proximity to a stationary target object. Information about the shape and the movement of the pipette is incorporated into the reconstruction algorithm. The algorithm was tested in a microrobot environment, where the pipette tip was tracked at sub‐Rayleigh distances to the target. Based on the tracking results, a machine vision module controlled the manipulation of microscopic objects, e.g. latex beads or diamond mono‐crystals. In the theoretical part of this paper we prove that knowledge of the form ‘the pipette has moved between two consecutive frames of the movie’ must result in a twofold increase in resolution. We used the normal flow of an image sequence to decode positional measures from motion evidence. In practice, super‐resolution factors between 3 and 5 were obtained. The additional gain originates from the geometric constraints that were imposed upon the stereo reconstruction of the pipette axis.
Iso‐butanol saturated water: a simple procedure for increasing staining intensity of resin sections for light and electron microscopy
Authors: Roberts I. M. 
Published: March 2003

SummaryThe addition of the alcohol iso‐butanol (2‐methylpropan‐1‐ol) to water was found to improve the post‐staining procedures for semi‐thin and ultrathin resin sections, for both light and electron microscopy. Stain penetration was enhanced with samples embedded in both acrylic and epoxy resins and provided structural information not previously seen. These improvements were found with general (non‐specific) stains and a fluorescence stain for light microscopy, as well as for a range of heavy metal stains for electron microscopy. The use of this water/solvent medium also gave improved results when used in a variety of immunogold labelling procedures, resulting in a greater specific label density without affecting background gold levels. The use of this solvent/water medium may have wider applications for other types of staining.
In situ high temperature microscopy study of the surface oxidation and phase transformations in titanium alloys
Authors: Malinov S. , Sha W. , Voon C. S. 
Published: March 2003

SummaryTwo popular commercial titanium alloys, Ti‐6Al‐4V and Ti‐6Al‐2Sn‐4Zr‐2Mo‐0.08Si, were used for in situ high temperature microscopy study. The experiments were performed on an optical microscope equipped with high temperature stage using both normal and florescence lights. Two kinds of experiments were performed, at continuous heating/cooling with different rates and in isothermal conditions at different temperatures. The changes taking place on the sample surface during the experiments were monitored. The morphology of the α⇒β⇒α phase transformation was recorded at different heat treatment conditions using the effect of thermal etching. An effect of sample surface oxidation and deoxidation was observed during continuous heating. The appearance and disappearance of ordered titanium oxides Ti3O and Ti2O are discussed based on the phase equilibrium diagram. The kinetics of the surface oxidation was monitored in both isothermal and continuous cooling conditions.
Determination of the water droplet size distribution of fat spreads using confocal scanning laser microscopy
Authors: Van Dalen G. 
Published: March 2003

SummaryKnowledge of the water droplet size distribution of fat spreads is necessary for the development and production of high quality microbiological safe products. Fat spreads are water‐in‐oil emulsions. The water droplet size distribution can be determined by confocal scanning laser microscopy (CSLM) after staining the fat with Nile Red. The profiles of the non‐fluorescent water droplets in the 2D images are identified and measured using image analysis. The ‘true’ water droplet size distribution is calculated from the distribution of the measured profile diameters using a Wicksell transformation of log‐normal distributions. The influence of the fluorescent staining and CSLM parameters on the information were studied. The CSLM method was tested on fat spreads with a fat content ranging from 40% to 80%. The results were compared with those obtained by nuclear magnetic resonance spectroscopy (NMR). The distribution parameters [volume weighed geometric mean diameter (D̄3,3) and the standard deviation (σ) of the logarithm of the droplet diameter] calculated for 80% fat spreads are in good agreement with those obtained by NMR (within ± 7% relative). Small differences were found for 65% fat spreads and large differences were identified for 40% fat spreads. The precision for the determination of the D̄3,3 value by CSLM is worse than that of NMR, even when three images were used to calculate this parameter [3–11% and 1–6% relative standard deviation (RSD), respectively]. The precision for the determination of exp(σ) by CSLM is comparable or better than that of NMR (1–5% and 3–6% RSD, respectively). CSLM proved to be a reliable method for the determination of the water droplet size distribution of margarines (80% fat). The advantage of CSLM compared to NMR is that visual information is given about the water droplet size distribution in the sample.
Precise 3D image alignment in micro‐axial tomography
Authors: Matula P. , Kozubek M. , Staier F. , Hausmann M. 
Published: March 2003

SummaryMicro (µ‐) axial tomography is a challenging technique in microscopy which improves quantitative imaging especially in cytogenetic applications by means of defined sample rotation under the microscope objective. The advantage of µ‐axial tomography is an effective improvement of the precision of distance measurements between point‐like objects. Under certain circumstances, the effective (3D) resolution can be improved by optimized acquisition depending on subsequent, multi‐perspective image recording of the same objects followed by reconstruction methods. This requires, however, a very precise alignment of the tilted views. We present a novel feature‐based image alignment method with a precision better than the full width at half maximum of the point spread function. The features are the positions (centres of gravity) of all fluorescent objects observed in the images (e.g. cell nuclei, fluorescent signals inside cell nuclei, fluorescent beads, etc.). Thus, real alignment precision depends on the localization precision of these objects. The method automatically determines the corresponding objects in subsequently tilted perspectives using a weighted bipartite graph. The optimum transformation function is computed in a least squares manner based on the coordinates of the centres of gravity of the matched objects. The theoretically feasible precision of the method was calculated using computer‐generated data and confirmed by tests on real image series obtained from data sets of 200 nm fluorescent nano‐particles. The advantages of the proposed algorithm are its speed and accuracy, which means that if enough objects are included, the real alignment precision is better than the axial localization precision of a single object. The alignment precision can be assessed directly from the algorithm's output. Thus, the method can be applied not only for image alignment and object matching in tilted view series in order to reconstruct (3D) images, but also to validate the experimental performance (e.g. mechanical precision of the tilting). In practice, the key application of the method is an improvement of the effective spatial (3D) resolution, because the well‐known spatial anisotropy in light microscopy can be overcome. This allows more precise distance measurements between point‐like objects.
The Effect of the Alpha‐2‐Adrenergic Agonist, Clonidine, on Secretion Patterns and Rates of Adrenocorticotropic Hormone and its Secretagogues in the Horse
Authors: Alexander S. L. , Irvine C. H. G. 
Published: March 2003

AbstractAlpha‐2‐adrenoceptor activation may lower adrenocorticotropic hormone (ACTH) by reducing secretagogue input and/or increasing the release of an inhibitory factor (CIF). To investigate this, we gave clonidine, an α‐2‐agonist, to seven horses, and collected pituitary venous blood every minute for 20 min before treatment and 40 min after treatment. Six horses were given saline vehicle. Mean secretion rates of corticotrophin‐releasing hormone (CRH), arginine vasopressin (AVP) and ACTH were calculated before and during four 5‐min then two 10‐min periods after clonidine or saline. Reduction in ACTH secretion without corresponding changes in CRH and/or AVP would imply the presence of CIF. Secretion rates of ACTH (P = 0.008) and AVP (P = 0.0005) fell after clonidine and remained lower than baseline values for 20 min and 10 min, respectively. The CRH secretion rate decreased slightly but not significantly after clonidine. In controls, hormone secretion rates did not alter during the experiment. Multiple linear regression showed that CRH and AVP secretion accounted for 69% (treated) or 45% (controls) of the variation in ACTH secretion (P < 0.0001 for each). CRH alone contributed 80% (treated) or 76% (controls) of the fit to this model, which is consistent with the concept that CRH ‘sets the gain’ of the response of corticotrophs to fluctuations in AVP. Accordingly, minute‐to‐minute changes in pituitary concentrations of AVP and ACTH were synchronous when all data were considered (% concordant changes: controls, 68%, P < 0.0001; treated, 76%, P < 0.0001) and the percentage of concordant movement was unaffected by clonidine (before 72%; after 73%; P = 0.80). In treated horses but not controls, the ratio between the secretion rates of ACTH and AVP fell (P = 0.009), while the ACTH : CRH ratio tended to fall after clonidine, implying reduced responsiveness to stimulation. Moreover, one horse showed a drop in ACTH and a rise in CRH and AVP secretion after clonidine. We conclude that in horses α‐2‐adrenoceptor activation lowers ACTH secretion primarily by reducing the secretion of AVP and possibly CRH. While there was some evidence that a CIF may participate in the clonidine‐induced suppression of ACTH, the subtlety of the discordance between ACTH and its secretagogues in most horses and the rarity of complete dissociation indicate that it does not play a major role.
Differential Regulation of Leptin Receptor But Not Orexin in the Hypothalamus of the Lactating Rat
Authors: Brogan R. S. , Grove K. L. , Smith M. S. 
Published: March 2003

AbstractDuring lactation, hypothalamic levels of neuropeptide Y (NPY) and agouti related protein (AGRP) mRNA are increased, while pro‐opiomelanocortin (POMC) mRNA is decreased. Serum leptin levels are also decreased during lactation. These changes may underlie the large increases of both food and water intake that occur in concert with milk production. However, additional hypothalamic substances, such as the novel peptide, orexin, may be involved. In addition, in the presence of chronically suppressed levels of serum leptin, there may be a change in leptin receptor expression in the hypothalamus. The objectives of the present study were to determine if orexin and leptin receptor mRNA levels were changed during lactation. Rats were studied on dioestrus of the oestrous cycle or on day 10 postpartum (the lactating animals were suckling eight pups). Orexin mRNA levels in the lateral hypothalamus did not differ between dioestrus and lactation. There was a significant increase in leptin receptor mRNA levels in the supraoptic nucleus during lactation compared to dioestrus. Furthermore, leptin receptor protein, as determined by immunocytochemistry, was colocalized in virtually all vasopressin and oxytocin cells in the supraoptic nucleus. Lactating animals exhibited a decrease in leptin receptor mRNA in the ventromedial hypothalamic nucleus whereas no change was apparent in other hypothalamic areas compared to the dioestrus animals. These results demonstrate that changes in orexin do not appear to contribute to the increase in food intake during lactation. It is likely that the increases in NPY and ARGP, coupled with the decrease in POMC, are primarily responsible for sustaining the chronic hyperphagia of lactation. The changes observed in leptin receptor expression in the hypothalamus, along with the suppression of serum leptin levels, also suggest that the leptin signalling system may play a significant role in the regulation of food and water intake during lactation.
Seasonal Variation in Androgen‐Metabolizing Enzymes in the Diencephalon and Telencephalon of the Male European Starling (Sturnus vulgaris)
Authors: Riters L. V. , Baillien M. , Eens M. , Pinxten R. , Foidart A. , Ball G. F. , Balthazart J. 
Published: March 2003

AbstractIn seasonally breeding songbirds, seasonal fluctuations occur in serum testosterone (T) concentrations and reproductive behaviours. Many T‐dependent behaviours are regulated by the activity of androgenic and oestrogenic metabolites within specific brain regions. Male European starlings breed in spring when circulating T concentrations peak. T and its metabolites act within portions of the diencephalon to regulate the pituitary‐gonadal axis and to activate courtship and copulation. Song in male starlings is critical for mate attraction during the breeding season and is regulated by steroid‐sensitive nuclei in the telencephalon and diencephalon. Outside the breeding season, T is undetectable, however, males continue to sing at high levels. This suggests that singing outside of the breeding season might not be T‐dependent as it appears to be in the spring. Alternatively, singing when T is low might continue to be regulated by T due to increased sensitivity of the brain to the action of the steroid. This increased sensitivity could be mediated by changes in intracellular T metabolism leading to increased production of active or decreased production of inactive metabolites. To explore the relationship between T‐metabolism and reproductive behaviour, we analysed seasonal changes in the activity of four brain T‐metabolizing enzymes: aromatase, 17β‐hydroxysteroid dehydrogenase (17β‐HSDH), 5α‐reductase (all three convert T into active metabolites) and 5β‐reductase (converts T into an inactive metabolite) in the diencephalon and telencephalon. In the anterior and posterior diencephalon, the highest aromatase was observed in spring when this region is critical for courtship and copulation. In the telencephalon, aromatase was highest and 5β‐reductase was lowest throughout the winter months well prior to the reproductive season and these enzymes presumably maximize T‐activity within this region. Although these data do not indicate whether the metabolic changes occur specifically within song nuclei, these findings are compatible with the idea that singing in male starlings outside the breeding season may be regulated by steroids despite the presence of low serum T concentrations. Overall, seasonal changes in T‐metabolizing enzymes appear to play a significant role in seasonal changes in behaviour and reproductive physiology.
β‐Endorphin Cells in the Arcuate Nucleus: Projections to the Supraoptic Nucleus and Changes in Expression During Pregnancy and Parturition
Authors: Douglas A. J. , Bicknell R. J. , Leng G. , Russell J. A. , Meddle S. L. 
Published: March 2003

AbstractSupraoptic nucleus oxytocin neurone activity and secretion are inhibited in late pregnancy and parturition by endogenous opioids. Here, we investigated alterations in the projections and gene expression of β‐endorphin/pro‐opiomelanocortin neurones in the arcuate nucleus in the pregnant rat. All regions of the arcuate nucleus were found to contain cells immunoreactive for β‐endorphin fluorescent microbeads retrogradely transported from the supraoptic nucleus, and double‐labelled neurones (β‐endorphin plus microbeads), showing that β‐endorphin neurones throughout the arcuate nucleus project to the supraoptic nucleus. There was an increase in the number of β‐endorphin‐immunoreactive cells in the arcuate nucleus and an increase in the density of β‐endorphin fibres within the supraoptic nucleus and peri‐supraoptic region in late pregnancy and parturition, suggesting enhanced expression of β‐endorphin and increased β‐endorphin innervation of the supraoptic nucleus. Pro‐opiomelanocortin mRNA expression in the arcuate nucleus increased in late compared to early pregnancy: the number of positive neurones significantly increased in the caudal region. Fos expression (an indicator of neuronal activation) in the arcuate nucleus was colocalized in β‐endorphin neurones in both proestrus and parturient rats, but the number of positive cells did not increase during parturition, suggesting lack of activation of β‐endorphin neurones at birth. Thus, β‐endorphin cells in the arcuate nucleus project to the supraoptic nucleus and increased innervation during pregnancy may explain the enhanced endogenous opioid inhibition of oxytocin neurones.