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  • 1
    ISSN: 0584-8539
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0568
    Keywords: Key words Claustrum ; Visual cortex ; Visual zones Comparative anatomy ; Rat ; Guinea pig ; Rabbit ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The retrograde axonal transport method was used to compare the topography and organization of the visual zone of the claustrum in rat, guinea pig, rabbit and cat. First, massive Fluoro-Gold injections were placed into the primary visual cortex and the secondary areas. Experiments showed differences in the location of the visual zone among the animals under study. In rat, the visual zone occupied the posteroventral part of the claustrum and spread to its anterior pole. In guinea pig, neurons projecting to the visual cortex were located dorsally in the posterior half of the claustrum. In rabbit, similarly to the rat, they were localized in the posteroventral part; however, they did not reach the anterior pole. In cat, neurons that project to the visual cortex were concentrated dorsally in the posterior fourth of the claustrum. In double-injection experiments, Fast Blue and Diamidino Yellow were placed into the primary and secondary visual areas in various combinations. The experiments showed that in the rat and the rabbit claustral neurons project to primary visual cortex (area 17) as well as to both secondary visual areas (areas 18a and b). Populations of neurons sending axons to the primary and secondary areas showed full overlap. The presence of double-labeled neurons indicates that some claustral neurons project both to the primary and secondary fields. In cat, neurons that project to the primary visual cortex appear to be clearly separated from those connected with the secondary visual area, as no double-labeled neurons were found. In all studied species, the double injections placed into the visual and primary somatosensory cortex did not result in any double-labeling neurons. Our results indicate that the location of the visual zone in the posterior part of the claustrum is a phylogenetically stable feature, whereas its dorsoventral shift as well as the extent toward the anterior pole is related to the particular species. The overlap of neurons projecting to the primary and secondary visual areas in the rat and rabbit as well as the separation of both projections in cat appear to reflect the higher degree of complexity of the visual system in the latter.
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  • 3
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. Obstruction of the upper airway could be an initiating factor in the Sudden Infant Death Syndrome (SIDS). Responses to upper airway obstruction include augmentation of respiratory efforts, active dilation of the upper airway and electrocortical arousal. Vulnerable individuals may fail to mount these responses effectively.2. Respiratory and arousal responses to obstruction of the upper airway have been investigated in newborn lambs. In conscious lambs, nasal obstruction causes a profound augmentation of inspiratory efforts, mild asphyxiation and eventual formation of an oral airway. The ability to establish an oral airway involves both chemoreception and mechanoreception and improves with age.3. In sleeping lambs, obstruction of tidal airflow leads to progressive hypoxaemia, augmentation of inspiratory efforts, bradycardia and arousal. Arousal occurs earlier and with less hypoxaemia and bradycardia in non-REM sleep than in REM sleep. Arousal occurs after inspiratory efforts have increased to the same extent during both sleep states, suggesting that mechanoreception, or a sense of inspiratory effort, is important in initiating arousal.4. Obstruction of nasal tubes tends to cause arousal from sleep earlier, and with less hypoxaemia and less augmentation of inspiratory effort, than when a more compliant face mask is obstructed. This supports the suggestion that mechanoreception, which may be involved in the perception of inspiratory effort, is a determinant of arousal.5. With increasing postnatal age, lambs become less arous-able in response to airflow obstruction when in REM sleep. This suggests that lambs may become progressively more vulnerable to the effects of airway obstruction during the immediate newborn period.6. The ability to respond to upper airway obstruction is well developed at birth in normal lambs. Responses are affected by sleep-wake states, mode of airflow obstruction and postnatal age. Future studies will determine whether prenatal compromises, such as those thought to have influenced neural development in some SIDS victims, affect the ability of the neonate to respond adequately to upper airway obstruction.
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  • 4
    ISSN: 1434-4475
    Keywords: Photocatalysis ; Ruthenium ; Titania
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es wurde festgestellt, daß die„in situ“ Photodepositierung von Ruthenium auf Anatas-TiO2 eine effiziente Methode darstellt, um Ru/TiO2-Pulver herzustellen, das eine hohe Aktivität bei der Photoevolution von Wasserstoff aus Wasser-Methanol besitzt. Die Effizienz des Katalysators war höher, wenn das TiO2-Pulver vor der Bestrahlung einem Kationenaustausch unterworfen wurde. Die Reaktionsbedingungen wurden optimiert; TiO2, bedeckt mit 0.76 Gew% Ru, zeigte sich als aktivster Katalysator. Anatas-TiO2 selbst erwies sich als porös mit einem mittleren zylindrischen Porenradius von 37 Å. Mittels SEM und Mikrosondenanalyse wurde festgestellt, daß die Photodepositierung von Ruthenium auf dem porösen Substrat eine nichthomogene Verteilung auf der TiO2-Oberfläche ergibt. Das Ausmaß und die Größe der Ruthenium-Anhäufungen scheinen die Stabilität von Ru/TiO2-Katalysatoren bei der Photoevolution von Wasserstoff aus Wasser-Methanol zu beeinflussen.
    Notes: Summary “In situ” ruthenium photodeposition on anatase TiO2 was found to be an efficient method of obtaining Ru/TiO2 powders highly active in hydrogen photoevolution from water-methanol. The efficiency of the catalyst was higher when the TiO2 powder was subjected to a cation exchange prior to illumination in water-methanol. Reaction conditions were optimized; it was found that the most active sample was TiO2 covered with 0.75 wt% Ru. Anatase TiO2 itself was found to be porous with an average cylindrical pore radius of 37 Å. SEM and electron microprobe analysis showed that the photodeposition of ruthenium on the porous substrate resulted in a nonhomogeneous distribution on the TiO2 surface. The size of ruthenium islets seems to influence the stability of Ru/TiO2 catalysts in hydrogen photoevolution from water-methanol.
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  • 5
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1-O-(indole-3-acetyl)-β-d-glucose: myo-inositol indoleacetyl transferase (IA-myo-inositol synthase) is an important enzyme in IAA metabolism. This enzyme catalyses the transfer of the indole acetyl (IA) moiety from 1-O-(indole-3-acetyl)-β-d-glucose to myo-inositol to form IA-myo-inositol and glucose. IA-myo-inositol synthase was purified to an electrophoretically homogenous state from maize liquid endosperm by fractionation with ammonium sulphate, anion-exchange, adsorption on hydroxylapatite, affinity chromatography on ConA-Sepharose, preparative PAGE and isoelectric focusing. We thus obtained two enzyme preparations which differ in their Rf on 8% polyacrylamide gel. The preparation of Rf 0.36 contained a single 56.4 kDa polypeptide, whereas the preparation of Rf 0.39 consisted of two polypeptides of 56.4 and 53.5 kDa. Both purified preparations of IAInos synthase also exhibited the activity of an IAInos hydrolase, showing that the dual activity was associated with a single protein. Results of gel filtration and analytical SDS-PAGE suggest that the native enzyme exists as both a monomeric (65 kDa) and homo- or heterodimeric form (110–130 kDa). Analysis of peptide maps and amino acid sequences of two 21 amino-acid peptides showed that polypeptides of 56.4 and 53.5 kDa have the same primary structure and that the 3 kDa difference in molecular mass is probably caused by different glycosylation levels. Comparison of this partial and internal amino acid sequence with sequences of other plant acyltransferases indicated similarity to several proteins which belonged to the serine carboxypeptidase-like (SCPL) acyltransferase family.
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  • 6
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Plant ecology 124 (1996), S. 45-59 
    ISSN: 1573-5052
    Keywords: Ecological regression ; Quantitative and qualitative changes of structure and species composition ; Secondary succession ; Thermophilous oak-wood
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The historical process of the decline of the thermophilous oak forest was studied at 11 selected localities within the whole area of the association in Poland. The comparative analysis of phytosociological data from the periods of 1929–1981 and 1987–1991 has shown the total decline of Potentillo albae-Quercetum at nine localities as well as symptoms of regression at two localities. It has been stated that in Eastern Pomerania and in Greater Poland in the places of Potentillo albae-Quercetum phytocoenoses the communities of Galio-Carpinetum and Calamagrostio-Quercetum have appeared. In the central, north-east, south-east and southern part of the country, the thermophilous oak forest has changed into Tilio-Carpinetum phytocoenoses. The results of the study indicate that the recession of Potentillo albae-Quercetum is taking place in the whole area of the association in Poland. The size of the area is changing, the number of localities is decreasing. The consequence of the thermophilous oak forest decline is the unification and impoverishment of woodland vegetation and flora. These localities of the association which exist up to date are ‘refuges’ for many interesting helio- and thermophilous species. Their presence to a great extent determines the genetic pool and diversity of Polish flora.
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  • 8
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Oestrogen produces a positive feedback effect on the secretion of gonadotropin releasing hormone (GnRH) and luteinizing hormone (LH) when implanted into the ventromedial/arcuate nucleus of the ovariectomized (OVX) ewe. This has led to the belief that it is in this area of the hypothalamus that oestrogen causes the preovulatory surge in GnRH/LH. To date, however, the cell types that are integral to this response have not been identified. The present study aimed to examine cellular responsiveness to oestrogen in this region of the brain using Fos immunohistochemistry and further aimed to determine the cell type that shows an acute response to oestrogen. OVX ewes (n = 4–6 per group) were given i.m. injections of oestradiol benzoate or oil (vehicle) and were killed 1–6 h later. Brains were perfused for immunohistochemistry. The number of cells in the arcuate nucleus which were immunopositive for Fos was greater (two- to fourfold) in the oestradiol benzoate-treated OVX ewes (n = 5) 1 h after injection. The number of Fos-positive cells in the ventromedial hypothalamic nucleus was 10-fold greater in the oestradiol benzoate-treated ewes 1 h after injection. Because there were high levels of Fos-immunoreactive cells in oil-treated ewes, we repeated the experiment with i.v. injection of 50 µg oestrogen or vehicle (n = 5). With this latter procedure, we found that oestrogen injection caused a significant increase in the number of Fos immunoreactive cells in the arcuate nucleus within 1 h, but there was no response in the ventromedial hypothalamus. To further characterize the types of cells that might respond to oestrogen, we double-labelled cells for Fos and either adrenocorticotropin hormone, neuropeptide Y or tyrosine hydroxylase (a marker for dopaminergic cells). These cell types could account for less than 30% of the total number of cells that were Fos-positive and oestrogen treatment did not cause an increase in the Fos labelling of any of these types of cell. These data show that oestrogen activates cells of the arcuate/ventromedial hypothalamus within 1 h of injection and that this response could relate to the feedback effects of this gonadal hormone. The majority of cells that produce Fos following oestrogen injection are of unknown phenotype. The data further suggest that induction of cells of the ventromedial hypothalamic nucleus require more prolonged oestrogen stimulus than cells of the arcuate nucelus.
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  • 9
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Previous studies have shown that there is a population of noradrenergic cells in the caudal A1 field of the brainstem of the ewe that contain oestrogen receptors and project to the preoptic area, where gonadotrophin releasing hormone (GnRH) neurones are located. There are some discrepancies in the literature regarding the extent of this projection and the location of the cells in the A1 region. The issue has been a focus of attention because the positive feedback response to oestrogen that causes the ovulatory GnRH/luteinizing hormone surge may originate from this brainstem region. The aim of the present study was to determine the extent of the projections to the preoptic area and to determine whether the caudal A1 cells are activated by oestrogen. Eleven ovariectomized ewes received an injection of the retrograde tracer FluoroGold into the preoptic hypothalamus and four of these also received an i.m. injection of oestrogen 2 h before tissue collection. A further three sheep received i.m. oil injections to act as controls for those receiving oestrogen. Dopamine-β-hydroxylase (DBH)-positive, retrogradely labelled cells were found within the A1 field in sheep that received preoptic FluoroGold injections. Cells in the vicinity of the A2 and A6 fields, that were retrogradely labelled with FluoroGold, were not DBH-positive. Thus, cells in the A1 field provide a direct noradrenergic projection to the preoptic area and may be involved in the control of the secretion of GnRH in this species. Cells that project to the preoptic hypothalamus from more rostrally located areas of the brainstem are not noradrenergic. In the animals that received oestrogen, double-labelling immunohistochemistry was performed throughout the A1 field for FluoroGold, DBH and Fos. DBH cells of the A1 field expressed Fos only in the oestrogen-treated animals and not in the oil-treated animals. There was a decline in the number of DBH cells that were retrogradely labelled from the caudal region of A1 towards obex. There was a similar gradient in the number of cells that were double-labelled for Fos and FluoroGold. We conclude that there is a population of noradrenergic cells in the caudal A1 field that project to the preoptic area; this is a larger group of cells than previously reported. Oestrogen elicits an acute Fos response in these cells, which may be involved in the time-delayed positive feedback response on GnRH cells. The caudal-to-rostral gradient in the labelling with FluoroGold and Fos in DBH-positive cells is similar to that seen previously for oestrogen receptor in DBH-positive cells in the A1 field.
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  • 10
    ISSN: 1432-1459
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
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