Браузер не даёт сохранять данные (например, приватный режим): закладки пропадут после закрытия вкладки.
Поиск статей PubMed
Ключевые слова, автор, журнал, годы — результаты из PubMed, аннотации с переводом на русский, закладки в браузере.
Найдено: 5 468
Страница 183 из 547-
Responses of the teleost pituitary (goldfish, eel) to deionized water.
The cytological responses of the pituitary gland during adaptation to deionized water (DW) were investigated in the goldfish and the eel. In both teleost species, a stimulation of the prolactin (PRL) cells could not be detected, although the levels of blood electrolytes (Na+, Ca2+, Cl-) are reduced in the eel. PRL cells appear less active in DW-adapted eels. A striking stimulation of the PAS-positive cells of the pars intermedia occurs in both species after 3 weeks and, in the eel, is still present after 11 weeks. Cell and nuclear hypertrophy, mitoses and a well-developed endoplasmic reticulum are observed. MSH cells are partially degranulated when pigmentation is affected; a reduced activity of MSH cells is evident after 11 weeks. The amount of neurohypophysial tissue is reduced. In the goldfish and the eel, during adaptation to DW, an unknown factor secreted by the PAS-positive cells of the pars intermedia appears to play a more important role than the secretion of PRL. These two species are able to survive in fresh water without the pituitary. The control of the PAS-positive cells by external sodium or calcium is discussed.
-
Comparative morphometric study of cerebellar neurons. I. Granule cells.
Several differences concerning granule cell characteristics have been reported in phylogenetic studies. In this work, the granule cell features of 4 frogs, 4 pigeons, 4 rats, 4 cats and 6 human subjects were determined using morphometric methods. Frog granule cells showed a significantly greater volume and a significantly lower numerical density in comparison with the other species; nevertheless no significant differences were found concerning their organelles. The volume of granule cells was significantly smaller in man than in the other two mammal species but no significant differences were observed in their numerical densities. A significant negative correlation was found between the mean cellular volume and the numerical density of granule cells in every species. These results support the assumption that the biological development of the human cerebellar granular layer is accompanied by a miniaturization of the granule cells, in a way similar to that previously suggested for cerebral neurons.
-
Ultrastruct and origin of epiplexus cells in the telencephalic choroid plexus of postnatal rats studied by intravenous injection of carbon particles.
Epiplexus cells in the telencephalic choroid plexus of postnatal rats were shown with the electron microscope to be of two kinds, one with monocyte features including an indented nucleus with coarse chromatin, numerous polyribosomes, long profiles of rough endoplasmic reticulum, a well-developed Golgi apparatus, lysosomes, microtubules and coated vesicles, long cytoplasmic process and filopodia; the other with the addition of highly vacuolated cytoplasm. In order to clarify the origin of these cells, rats were given two intravenous injections of carbon particles. Shortly after the second carbon injection (1-4 days) none of the epiplexus cells were tagged with carbon. Five and six days after the second carbon injection, however, a variable number of epiplexus cells were labelled with intracytoplasmic carbon. Their number decreased later and by 9 days hardly any were seen. The present evidence suggests that the carbon-labelled epiplexus cells are derived from circulating monocytes which have ingested the carbon particles while in the blood. The labelled cells then cross the walls of subependymal blood vessels, penetrate the multilayered subspendyma and ependymal lining and enter the lumen of the lateral ventricle.
-
Synapses of optic nerve afferents in the rat suprachiasmatic nucleus. II. Structural variability as revealed by morphometric examination.
The identification of optic synapses in the rat suprachiasmatic nucleus (Güldner, 1978) has made it possible to study them morphometrically. The measurements followed the check-list introduced by Palay and Chan-Palay (1976). There are several items which could usefully be added to this list. The structure of essential synaptic components varies considerably in what is apparently one synaptic population based on morphological criteria. The possible reasons for the variable sizes of the optic boutons containing different amounts of clear and dense core vesicles are discussed in terms of different activities or metabolic states of the individual boutons and/or different metabolic states of neuronal and glial elements in their vicinity. The active zones of optic synapses are also extremely variable. One optic bouton can form several active zones of very different sizes, or form Gray-type-I ("asymmetric"), Gray-type-II ("symmetric") and intermediate contacts at the same time. The function and/or functional efficiency of a single optic bouton therefore could then be quite different with respect to its various postsynaptic elements. The different appearance of the active zones is discussed mainly in terms of possible regulative influences from neighboring synapses via the postsynaptic neuron.
-
Synaptology of neurosecretory cells in the nucleus paraventricularis of the domestic fowl.
Processes of magnocellular neurosecretory cells (MNCs) are easily identifiable on the basis of their content in neurosecretory granules in the neuropil of the rostral division of the paraventricular nucleus (PVN) of the domestic fowl. In specimens sacrificed during the winter the synaptic organization of the neuropil and the pattern of synapses ending on neurosecretory processes were studied at the ultrastructural level. Synapses in the rostral part of the PVN neuropil may be divided into three main categories on the basis of their morphology and their content of clear and dense-core synaptic vesicles. These different types of terminals can be attributed to aminergic, peptidergic or other types of synapses. The percent distribution of synapses within these categories differs when all synapses observed in the neuropil or only those ending on MNC processes are compared. Present ultrastructural data obtained in birds support two physiological hypotheses already suggested for mammals, i.e., the probable existence of a recurrent pathway to MNCs via an interneuron, and the importance of aminergic and peptidergic input in regulating the electrical activity ov MNCs.
-
Transition metal dichalcogenides to optimize the performance of peptide-imprinted conductive polymers as electrochemical sensors.
Molecularly imprinted polymer (MIP)-based electrochemical sensors for the protein α-synuclein (a marker for Parkinson's disease) were developed using a peptide epitope from the protein. MIPs doped with various concentrations and species of transition metal dichalcogenides (TMDs) to enhance conductivity were electropolymerized with and without template molecules. The current during the electropolymerization was compared with that associated with the electrochemical response (at 0.24~0.29 V vs. ref. electrode) to target peptide molecules in the finished sensor. We found that this relationship can aid in the rational design of conductive MIPs for the recognition of biomarkers in biological fluids. The sensing range and limit of detection of TMD-doped imprinted poly(AN-co-MSAN)-coated electrodes were 0.001-100 pg/mL and 0.5 fg/mL (SNR = 3), respectively. To show the potential applicability of the MIP electrochemical sensor, cell culture medium from PD patient-specific midbrain organoids generated from induced pluripotent stem cells was analyzed. α-Synuclein levels were found to be significantly reduced in the organoids from PD patients, compared to those generated from age-matched controls. The relative standard deviation and recovery are less than 5% and 95-115%, respectively. Preparation of TMD-doped α-synuclein (SNCA) peptide-imprinted poly(AN-co-MSAN)-coated electrodes.
-
Ultrastructure of the cell types of the anterior hypophysis in a lizard. II. Somatotrophs and lactotrophs.
Somatotrophs of the teiid lizard Cnemidophorus lemniscatus are strictly localized in the rostral zone of the anterior hypophysis. Cells are prismatic and elongated, with basal nuclei. A dense hyaloplasm, a basal, serried system of stacked cisternae of rough endoplasmic reticulum, and predominantly spherical, medium-sized secretory granules that fill the supranuclear region characterize these cells. Secretory granules have moderate opacity, uniform dimensions, and a close bounding membrane. The well developed Golgi apparatus lies at one side of the nucleus. Regular variations correlative with environmental or experimental changes could not be verified in somatotrophs. Lactotrophs are mainly situated in the caudal and intermediate zones of pars distalis, reaching the rostral region when numerous and hypertrophic. They are avoid or pear-shaped, with a central nucleus. A basal system of stacked cisternae of rough endoplasmic reticulum, and the completely irregular shape of the secretory granules are typical of these cells. The granules, supranuclear and often large, have low density, a finely granular structure and a close bounding membrane. A fibrillar substance affords a mottled appearance to the hyaloplasm. The well developed Golgi apparatus is frequently found in the center of the basal region. The activity of lactotrophs, denoted by the size and number of cells, their spread in the gland, the amount of granules, and the development of the organelles, is much greater during the annual period of enhanced sexual function, and particularly in females.
-
Ultrastructural and quantitative study on development of neuropil of dLGN and SCN around the eye-opening in mice.
The postnatal development of some neural organizations in the dorsal lateral geniculate nucleus (dLGN) and superior colliculus (SCN) of 24 mice from 3 litters from birth to the 22nd day of age (especially around the eye-opening) and of the 3 adults was examined by means of ultrastructural and morphometrical methods. In the dLGN of 6 mice from one liter the density of the optic axon terminals which were differentiated by their mitochondrial characteristics, as well as the density of the undifferentiated axon terminals, of the dendrites and the mitochondria in the neuropil increased strikingly from the 16th day of age (2 days after the eye-opening) and almost reached the adult level on the 18th day of age. On the other hand, numerous thin cell processes in the dLGN disappeared by half in density during this period. Also the density of the synaptic structure of the dLGN and SCN from the other 2 liters markedly increased during this period. The cross sectioned areas of the optic and the undifferentiated axon terminals and the postsynaptic dendrites were measured on the 14th and 20th day and the third month of age by a tablet digitizer provided with a computer device, but no obvious change in these areas could be detected during this period. The present results revealed a facilitated increase of some neural elements from 2 days after eye-opening, which suggested that the facilitation might be caused by the light stimuli.
-
Development and cytodifferentiation of the rabbit pars intermedia. I. Fetal and perinatal stages.
The developing pars intermedia (PI) of rabbits of between 14 days post coitum (PC) and one day post partum (PP) have been studied by light and electron microscopy. Cell division is marked until 4th week PC, after which it is reduced. The (PI) loses its homogeneity by the 5th week PC due to localisation both intrinsic and invading cells and blood vessels. Four groups of parenchyma cells are recognisable: PI-glandular cells, interstitial cells, ACT-type cells and a heterogeneous group of dark cells. The ultrastructure of the ACT-type cells in the rabbit PI are here described for the first time. The differentiation of these cell types has been traced from 14 days PC to 32 days PC, in particular ACT-type cells are shown to develop in situ and the significance of this is discussed. In the PI-glandular cells dense cored granules appear first on the 15th day PC which is one day before any nerve connection is made with the primitive neural lobe and more than a week before vascularisation. Thereafter granularity increases until parturition when there is a phase of degranulation. Relatively electron lucent, larger vesicles are not found until 4th week PC.
-
Interleukin 10 Restores Lipopolysaccharide-Induced Alterations in Synaptic Plasticity Probed by Repetitive Magnetic Stimulation.
Systemic inflammation is associated with alterations in complex brain functions such as learning and memory. However, diagnostic approaches to functionally assess and quantify inflammation-associated alterations in synaptic plasticity are not well-established. In previous work, we demonstrated that bacterial lipopolysaccharide (LPS)-induced systemic inflammation alters the ability of hippocampal neurons to express synaptic plasticity, i.e., the long-term potentiation (LTP) of excitatory neurotransmission. Here, we tested whether synaptic plasticity induced by repetitive magnetic stimulation (rMS), a non-invasive brain stimulation technique used in clinical practice, is affected by LPS-induced inflammation. Specifically, we explored brain tissue cultures to learn more about the direct effects of LPS on neural tissue, and we tested for the plasticity-restoring effects of the anti-inflammatory cytokine interleukin 10 (IL10). As shown previously, 10 Hz repetitive magnetic stimulation (rMS) of organotypic entorhino-hippocampal tissue cultures induced a robust increase in excitatory neurotransmission onto CA1 pyramidal neurons. Furthermore, LPS-treated tissue cultures did not express rMS-induced synaptic plasticity. Live-cell microscopy in tissue cultures prepared from a novel transgenic reporter mouse line [C57BL/6-Tg(TNFa-eGFP)] confirms that ex vivo LPS administration triggers microglial tumor necrosis factor alpha (TNFα) expression, which is ameliorated in the presence of IL10. Consistent with this observation, IL10 hampers the LPS-induced increase in TNFα, IL6, IL1β, and IFNγ and restores the ability of neurons to express rMS-induced synaptic plasticity in the presence of LPS. These findings establish organotypic tissue cultures as a suitable model for studying inflammation-induced alterations in synaptic plasticity, thus providing a biological basis for the diagnostic use of transcranial magnetic stimulation in the context of brain inflammation.