bluuebunny/crossref_metadata_2025_split huggingface dataset:
Biological ultrastructure as revealed by high resolution cryo‐SEM of block faces after cryo‐sectioning
Authors: Walther  , Müller  
Published: March 2003

Ultrastructural information was obtained by imaging the block face of high‐pressure‐frozen cryo‐sectioned biological samples in a high‐resolution cryo‐SEM. Cryo‐sectioning leads to a well‐defined flat artificial surface in contrast to cryo‐fracturing. Typical artefacts of cryo‐sections such as compression and crevasses were not visible on the block face. The ultrastructural features known from resin sections and from freeze‐fractures could also be found on the block faces. The cytoplasms show particles of different size which most likely represent proteins. The effects of radiation damage could be reduced considerably by applying the double layer coating technique and backscattered electron imaging.High quality cryo‐sections are only obtained from vitrified material. Reasonably flat block faces were, however, also obtained from adequately frozen microcrystalline samples, thereby facilitating ultrastructural studies in the frozen hydrated state.
Wavelets as chromatin texture descriptors for the automated identification of neoplastic nuclei
Authors: Van De Wouwer  , Weyn  , Scheunders  , Jacob  , Van Marck  , Van Dyck  
Published: March 2003

Chromatin distribution reflects the organization of the DNA of a nucleus and contains important cellular diagnostic and prognostic information. Feulgen staining of breast tissue enables the chromatin distribution of the nucleus to be visualized in the form of texture. Describing texture in an objective and quantitative way by means of a set of texture parameters, combined with the study of the relationship of such parameters to the pathobiological cell properties, is useful both for reduction of the subjectivity inherently coupled to visual observation and for more accurate prognosis or diagnosis.We have presented an automated classification scheme for the diagnosis and grading of invasive breast cancer. The input to this scheme was a digitized microscopical image, from which nuclei were segmented. Chromatin texture was described using a set of textural parameters that include first‐ and second‐order statistics of the image grey levels. The more recently developed wavelet energy parameters were also included in our study. Classification was performed by a Knn‐classifier, which is a versatile multivariate statistical classification technique.We investigated the role of the tissue preparation technique and found that parameters derived from cytospins were better texture descriptors than those from sections. A 100% correct classification was achieved in a patient diagnosis experiment and 82% in a nuclear grading experiment.
A preliminary electron backscattered diffraction study of sintered NdFeB‐type magnets
Authors: Lillywhite S. J. , Williams A. J. , Davies B. E. , Harris I. R. 
Published: March 2003

SummaryThis paper reports, for the first time, the use of electron backscattered diffraction (EBSD) to study orientation in sintered NdFeB type magnets. The magnetic properties of NdFeB magnets are greatly improved if a strong crystallographic texture is firstly achieved, namely, the direction of the c‐axis is along the direction of magnetization. A systematic survey of sample preparation techniques showed that samples that were mechanically polished and then etched gave the most reliable EBSD data. Analyses were made using both fully automated EBSD scans and by EBSD measurements taken after manual movement of the beam. The EBSD results are presented as secondary electron SEM micrographs, orientation images and 001 pole figures. For the selection of grains investigated, the deviation of the c‐axis was shown to be between 10° and 30° from the ideal [001]//magnetization direction. It is demonstrated that EBSD is a valuable tool for characterizing the microstructure and texture relationships and for assessing the performance of the processing routes of NdFeB magnets.
Adaptive correction of depth‐induced aberrations in multiphoton scanning microscopy using a deformable mirror
Authors: Sherman L. , Ye J. Y. , Albert O. , Norris T. B. 
Published: March 2003

SummaryWe demonstrate adaptive aberration correction for depth‐induced spherical aberration in a multiphoton scanning microscope with a micromachined deformable mirror. Correction was made using a genetic learning algorithm with two‐photon fluorescence intensity feedback to determine the desired shape for an adaptive mirror. For a 40×/0.6 NA long working distance objective, the axial scanning range was increased from 150 mm to 600 mm.
The distribution of caveolin‐3 immunofluorescence in skeletal muscle fibre membrane defined by dual channel confocal laser scanning microscopy, fast Fourier transform and image modelling
Authors: Ockleford C. D. , Cairns H. , Rowe A. J. , Byrne S. , Scott J. J. A. , Willingale R. 
Published: March 2003

SummaryMembrane domains rich in caveolin‐3 overlie sarcomeric actin in skeletal muscle. The membrane exhibits a regular array of caveolin‐3 immunofluorescence using confocal laser scanning microscopy (CLSM). Fourier analysis of tissue imaged by CLSM accurately defines a repeating intensity with a long‐axis spacing of 1.48 µm confirmed by measurement of direct images. Reverse fast Fourier transform (FFT) and image‐modelling allow reconstruction of the pattern. Mathematical modelling has allowed replication of several features of the FFT, including the second order maxima that confirm the relatively high information content of the original images. Measurements of membrane‐pattern primary long‐axis spacings are consistent with our measurements of the I‐band sarcomere repeat in similarly prepared specimens labelled with fluorescent phalloidin or imaged using differential interference contrast microscopy. Dual‐channel CLSM analysis of the sarcomeric banding pattern of actin and the repeating pattern of muscle fibre membrane caveolin showed that caveolae overlie the I‐band. The anti‐caveolin immunofluorescence is deficient over the Z‐disc and maximal toward each of the I‐band extremities. A mechanism of membrane shape change in which membrane–lipid molecules are interposed between more stable anchored rafts associated with caveolae can be envisaged. Thus, increasing girth and reducing length of the sarcolemma in rapid contraction may be explained.
A new high‐aperture glycerol immersion objective lens and its application to 3D‐fluorescence microscopy
Authors: Martini N. , Bewersdorf J. , Hell S. W. 
Published: March 2003

SummaryHigh‐resolution light microscopy of glycerol‐mounted biological specimens is performed almost exclusively with oil immersion lenses. The reason is that the index of refraction of the oil and the cover slip of ~1.51 is close to that of ~1.45 of the glycerol mountant, so that refractive index mismatch‐induced spherical aberrations are tolerable to some extent. Here we report the application of novel cover glass‐corrected glycerol immersion lenses of high numerical aperture (NA) and the avoidance of these aberrations. The new lenses feature a semi‐aperture angle of 68.5°, which is slightly larger than that of the diffraction‐limited 1.4 NA oil immersion lenses. The glycerol lenses are corrected for a quartz cover glass of 220 µm thickness and for a 80% glycerol‐water immersion solution. Featuring an aberration correction collar, the lens can adapt to glycerol concentrations ranging between 72% and 88%, to slight variations of the temperature, and to the cover glass thickness. As the refractive index mismatch‐induced aberrations are particularly important to quantitative confocal fluorescence microscopy, we investigated the axial sectioning ability and the axial chromatic aberrations in such a microscope as well as the image brightness as a function of the penetration depth. Whereas there is a significant decrease in image brightness associated with oil immersion, this decrease is absent with the glycerol immersion system. In addition, we show directly the compression of the optic axis in the case of oil immersion and its absence in the glycerol system. The unique advantages of these new lenses in high‐resolution microscopy with two coherently used opposing lenses, such as 4 Pi‐microscopy, are discussed.
Structure of the (110) antiphase boundary in gallium phosphide
Authors: Cohen D. , Carter C. B. 
Published: March 2003

SummaryThe morphology of antiphase boundaries in GaP films grown by molecular beam epitaxy on Si (001) has been studied by transmission electron microscopy. The inversion of the crystal polarity between antiphase domains was confirmed by convergent‐beam electron diffraction. The APBs were often found to facet parallel to {110} planes. Strong‐beam α‐fringe contrast observed along the (110) facets indicates that adjacent antiphase domains are related by an additional rigid‐body lattice translation. Diffraction‐contrast analysis shows that this R corresponds to a shear parallel to the [001] direction and a small expansion. The magnitude of the translation was inferred, quantitatively, through a comparison between energy‐filtered zero‐loss images of the α‐fringe contrast with numerical calculations. The components of the rigid‐body lattice translation were determined to be 0.023 ± 0.0033 nm in the [001] direction and 0.005 ± 0.002 nm in the 0 direction. Based upon a geometric model of the {110} antiphase boundary, the lengths of the Ga and P antisite bonds were calculated to be 254 ± 2 pm and 227 ± 4 pm, respectively.
Modification of Nitric Oxide Synthase Activity and Neuronal Response in Rat Striatum by Melatonin and Kynurenine Derivatives
Authors: León Josefa , Vives Francisco , Crespo Elena , Camacho Encarnación , Espinosa Antonio , Gallo MigueL. A. , Escames Germaine , Acuña‐Castroviejo Darío 
Published: March 2003

Tryptophan is mainly metabolized in the brain through methoxyindole and kynurenine pathways. The methoxyindole pathway produces (among other compounds) melatonin, which displays inhibitory effects on human and animal central nervous systems, including a significant attenuation of excitatory, glutamate‐mediated responses. The kynurenine pathway produces kynurenines that interact with brain glutamate‐mediated responses. Nitric oxide (NO) increases glutamate release, and melatonin and kynurenines may act via modification of NO synthesis. In the present study, the effects of melatonin and four synthetic kynurenines were studied on the activity of rat striatal nitric oxide synthase (NOS) and on the response of rat striatal neurons to sensorimotor cortex (SMCx) stimulation, a glutamate‐mediated response. Melatonin inhibited both NOS activity and the striatal glutamate response, and these effects were dose‐related. Compound A (2‐acetamide‐4‐(3‐methoxyphenyl)‐4‐oxobutyric acid) did not inhibit NOS activity but inhibited the striatal response similarly to melatonin. Compound B (2‐acetamide‐4‐(2‐amino‐5‐methoxyphenyl)‐4‐oxobutyric acid) was more potent than melatonin in inhibiting both NOS activity and the striatal response. Compound C (2‐butyramide‐4‐(3‐methoxyphenyl)‐4‐oxobutyric acid) did not change NOS activity, but increased the striatal response. Compound D (2‐butyramide‐4‐(2‐amino‐5‐methoxyphenyl)‐4‐oxobutyric acid) showed potent inhibitory effects on both NOS activity and striatal glutamate‐mediated response. A structure‐related effect of the kynurenine derivatives was observed, and those with an amino group in position 2 of the benzenic ring had more potent effects than melatonin itself in inhibiting striatal NOS activity and the response of striatal neurons to SMCx.
The Effects of Ionotropic Agonists of Excitatory Amino Acids on the Release of Arginine Vasopressin in Rat Hypothalamic Slices
Authors: Joanny P. , Steinberg J. , Guerrero F. , Sauze N. , Oliver C. , Grino M. 
Published: March 2003

AbstractThe effects of ionotropic excitatory amino acids agonists on the release of vasopressin from rat hypothalamic slices were studied. Incubation with increasing doses of NMDA, kainate or AMPA decreased the release of vasopressin in a dose‐dependent manner. The values of the IC50 were 1.0, 9.6, or 3.7 × 10−8 M, respectively. The inhibitory effect of the various excitatory amino acids tested was blocked by coincubation with their respective antagonists. Vasopressin secretion was stimulated to 140.3 ± 7.6% of controls when the slices were obtained from chronically (7 days) salt‐loaded rats. Addition of 1 × 10−7 M NMDA or 1 × 10−6 M kainate to the incubation medium antagonized the salt loading‐induced increase in vasopressin release. Incubation with 1 × 10−4 M tetrodotoxin did not change basal vasopressin release, but it blocked the decrease in vasopressin secretion induced by 1 × 10−7 M NMDA or 1 × 10−6 M kainate or 1 × 10−6 M AMPA. Incubation with 1 × 10−5 M phaclophen (a GABAB antagonist) and 1 × 10−5 M bicuculline (a GABAA antagonist) was without effect on basal vasopressin secretion while it reversed the inhibition of vasopressin release induced by 1 × 10−7 M NMDA. Incubation with 1 × 10−6 M GABA alone decreased vasopressin secretion to 64.6 ± 6.9% of control values. The inhibitory effect of GABA did not change when 1 × 10−7 M NMDA was added to the incubation medium. These findings demonstrate that ionotropic excitatory amino acids agonists inhibit vasopressin secretion from hypothalamic slices. They strongly suggest that this inhibitory effect is mediated through local GABAergic interneurones.
Calcium‐Independent, Tyrosine Phosphorylation‐Dependent Effects of Serum on the Morphology of Cultured Neurohypophysial Astrocytes
Authors: Ramsell K. D. , Cobbett P. 
Published: March 2003

AbstractActivation of adenylate cyclase induces cultured neurohypophysial astrocytes (pituicytes) to change from a protoplasmic, nonstellate form to a stellate form. Stellation is inhibited and reversed (destellation) by serum. The objective of the present studies was to examine the roles of Ca2+ and tyrosine phosphorylation in mediating these morphological changes. The effects of forskolin (to induce stellation) and serum (to inhibit and reverse stellation) were not affected by replacement of Ca2+ with Co2+ in the medium or by treatment of cultures with thapsigargin. However, genistein, a specific inhibitor of tyrosine kinase(s), significantly reduced the effect of serum on forskolin‐induced stellation. Also, dephostatin, a specific inhibitor of tyrosine phosphatase, inhibited forskolin‐induced stellation. In contrast, genistein did not have a dramatic effect on serum‐induced destellation. The data demonstrate that morphological changes exhibited by cultured pituicytes are independent of Ca2+ but may be modulated by the activity of tyrosine kinase(s) and phosphatase(s).
Oestrogen Upregulates Noradrenaline Release in the Mediobasal Hypothalamus and Tyrosine Hydroxylase Gene Expression in the Brainstem of Ovariectomized Rhesus Macaques
Authors: Pau K.‐Y. F. , Hess D. L. , Kohama S. , Bao J. , Pau C. Y. , Spies H. G. 
Published: March 2003

AbstractNoradrenaline plays a key role in the initiation of ovulation in nonprimate species. A similar noradrenaline role in the primate has not been established experimentally. We utilized the ovariectomized‐oestrogen‐supplemented (OVX + E) rhesus macaque to examine the effects of intravenous (i.v.) infusion of oestradiol‐17β (E2) on the activity of the brain noradrenaline system. Experiment 1 established the induction of a preovulatory surge‐like release of luteinizing hormone in OVX + E monkeys by i.v. infusion of E2 (OVX + E + E2). In experiment 2, a marked increase in hypothalamic microdialysate noradrenaline concentrations occurred after identical E2 infusion into the OVX + E monkeys that were used in experiment 1. In experiment 3, tyrosine hydroxylase (TH) mRNA expression in the locus coeruleus of the brainstem increased at various times after E2 infusion as determined by semiquantitative in situ hybridization. The amount of TH mRNA in OVX + E + E2 animals was higher (P < 0.05) than that in either the OVX + E or OVX monkeys; no difference was found in the latter two groups. Moreover, selected locus coeruleus sections from E2‐infused monkeys were examined for the localization of oestrogen receptors (ER) by in situ hybridization. Both ER‐α and ER‐β mRNAs were expressed in the locus coeruleus, although the expression was greater for ER‐α than for ER‐β. We conclude that i.v. infusion of E2, which induces a preovulatory surge‐like release of LH, stimulates brain noradrenaline activity; this enhanced activity likely involves an ER‐mediated process and is reflected by hypothalamic noradrenaline release and locus coeruleus TH mRNA expression. The results support the concept that noradrenaline can influence the E2‐stimulated ovulation in nonhuman primates and that the brainstem is one of the components in this neuroendocrine process.
Variations in Maternal Behaviour are Associated with Differences in Oxytocin Receptor Levels in the Rat
Authors: Francis D. D. , Champagne F. C. , Meaney M. J. 
Published: March 2003

AbstractFemale Long‐Evans rats exhibit stable individual differences in maternal behaviours such as pup licking/grooming and arched‐back nursing posture (LG‐ABN). These variations in maternal behaviour are accompanied by differences in lactation‐induced increases in oxytocin receptor levels in brain regions known to mediate the expression of maternal care in this species (i.e. the bed nucleus of the stria terminalis, the medial preoptic area and the lateral septum). Oxytocin receptor levels in the central nucleus of the amygdala were significantly higher in high compared to low LG‐ABN females regardless of reproductive status. These findings suggest that individual differences in maternal behaviour may be directly related to variations in oxytocin receptor expression.
Effects of Chronic Bromocriptine Treatment on Tyrosine Hydroxylase (TH) mRNA Expression, TH Activity and Median Eminence Dopamine Concentrations in Ageing Rats
Authors: MohanKumar P. S. , MohanKumar S. M. J. , Quadri S. K. , Voogt J. L. 
Published: March 2003

AbstractThe purpose of this study was to investigate the age‐related changes in the responsiveness of tuberoinfundibular dopamine (TIDA) neurones to chronic hypoprolactinemia induced by treatment with bromocriptine, a dopamine receptor agonist. In one experiment, TIDA neuronal activity after acute hypoprolactinemia or exogenous prolactin was monitored by measuring tyrosine hydroxylase (TH) activity in the stalk median eminence of middle‐aged cycling female rats (10–12 months), old constant oestrous rats (18–20 months) and old pseudopregnant rats (22–24 months). In another experiment, middle‐aged cycling (10–12 months) rats were treated with bromocriptine for 6 or 12 months. TH activity was measured in the stalk median eminence, TH mRNA levels were measured in the arcuate nucleus and dopamine concentrations were measured in the arcuate nucleus and median eminence. Responsiveness of TIDA neurones to exogenous prolactin and to the withdrawal of bromocriptine in these rats was also tested. While the TIDA neurones in all three age groups responded to acute hypoprolactinemia by showing a reduction in TH activity, older rats failed to respond to exogenous prolactin administration. In contrast, chronic hypoprolactinemia for 12 months enabled the rats to retain TIDA neuronal responsiveness to exogenous prolactin. It also decreased TIDA neuronal function as measured by dopamine concentrations in the median eminence, TH activity in the stalk median eminence and TH mRNA in the arcuate nucleus of ageing rats. The restoration of the responsiveness of these neurones to prolactin stimulation in older rats demonstrates for the first time that hypoprolactinemia produced by chronic bromocriptine treatment indeed provides a neuroprotective effect on TIDA neurones. These results indicate that maintaining a low level of neuronal activity by lowering prolactin levels may be a contributing factor in retaining the plasticity of TIDA neurones.
The Insulin Hypoglycemia Test: Hypoglycemic Criteria and Reproducibility
Authors: Nye E. J. , Grice J. E. , Hockings G. I. , Strakosch C. R. , Crosbie G. V. , Walters M. M. , Torpy D. J. , Jackson R. V. 
Published: March 2003

AbstractThe insulin hypoglycemia test (IHT) is widely regarded as the ‘gold standard’ for dynamic stimulation of the hypothalamic‐pituitary‐adrenal (HPA) axis. This study aimed to investigate the temporal relationship between a rapid decrease in plasma glucose and the corresponding rise in plasma adenocorticotropic hormone (ACTH), and to assess the reproducibility of hormone responses to hypoglycemia in normal humans. Ten normal subjects underwent IHTs, using an insulin dose of 0.15 U/kg. Of these, eight had a second IHT (IHT2) and three went on to a third test (IHT3). Plasma ACTH and cortisol were measured at 15‐min intervals and, additionally, in four IHT2s and the three IHT3s, ACTH was measured at 2.5‐ or 5‐min intervals. Mean glucose nadirs and mean ACTH and cortisol responses were not significantly different between IHT1, IHT2 and IHT3. Combined data from all 21 tests showed the magnitude of the cortisol responses, but not the ACTH responses, correlated significantly with the depth and duration of hypoglycemia. All subjects achieved glucose concentrations of of ≤ 1.6 mmol/l before any detectable rise in ACTH occurred. In the seven tests performed with frequent sampling, an ACTH rise never preceeded the glucose nadir, but occurred at the nadir, or up to 15 min after. On repeat testing, peak ACTH levels varied markedly within individuals, whereas peak cortisol levels were more reproducible (mean coefficient of variation 7%). In conclusion, hypoglycemia of ≤ 1.6 mmol/l was sufficient to cause stimulation of the HPA axis in all 21 IHTs conducted in normal subjects. Nonetheless, our data cannot reveal whether higher glucose nadirs would stimulate increased HPA axis activity in all subjects. Overall, the cortisol response to hypoglycemia is more reproducible than the ACTH response but, in an individual subject, the difference in peak cortisol between two IHTs may exceed 100 nmol/l.