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881.
Erik N. T. P. Bakker Brian J. Bacskai Michal Arbel-Ornath Roxana Aldea Beatrice Bedussi Alan W. J. Morris Roy O. Weller Roxana O. Carare 《Cellular and molecular neurobiology》2016,36(2):181-194
The lymphatic clearance pathways of the brain are different compared to the other organs of the body and have been the subject of heated debates. Drainage of brain extracellular fluids, particularly interstitial fluid (ISF) and cerebrospinal fluid (CSF), is not only important for volume regulation, but also for removal of waste products such as amyloid beta (Aβ). CSF plays a special role in clinical medicine, as it is available for analysis of biomarkers for Alzheimer’s disease. Despite the lack of a complete anatomical and physiological picture of the communications between the subarachnoid space (SAS) and the brain parenchyma, it is often assumed that Aβ is cleared from the cerebral ISF into the CSF. Recent work suggests that clearance of the brain mainly occurs during sleep, with a specific role for peri- and para-vascular spaces as drainage pathways from the brain parenchyma. However, the direction of flow, the anatomical structures involved and the driving forces remain elusive, with partially conflicting data in literature. The presence of Aβ in the glia limitans in Alzheimer’s disease suggests a direct communication of ISF with CSF. Nonetheless, there is also the well-described pathology of cerebral amyloid angiopathy associated with the failure of perivascular drainage of Aβ. Herein, we review the role of the vasculature and the impact of vascular pathology on the peri- and para-vascular clearance pathways of the brain. The different views on the possible routes for ISF drainage of the brain are discussed in the context of pathological significance. 相似文献
882.
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884.
Michal Sorek Jacob Douek Tamar Guy-Haim Noa Simon-Blecher Baruch Rinkevich 《Zoology in the Middle East.》2016,62(4):331-341
Fluorescent-amplified fragment length polymorphism (FAFLP) fingerprinting assay was used to compare the genetic diversity within and between tadpole shrimps (Notostraca) populations of Lepidurus apus (n=7) and Triops cancriformis (n=2) from rain pools in Israel. Each ephemeral water body has revealed a unique fingerprint pattern with an entailed genetic drift between nearby ponds. High similarity of genotypic diversity within each geographic area led to three clusters of water bodies, north, south and center of Israel. FAFLP assays on several newly hatched individuals of T. cancriformis revealed high identity amongst kin, as compared to L. apus where newly hatched from the same maternal source showed high diversity. Results indicate that T. cancriformis populations from Israel are probably parthenogenetic as indicated by clonal structures. The higher genetic variability in the L. apus populations and in laboratory-hatched specimens indicates the existence of sexual reproduction. 相似文献
885.
Up-regulation of NPY gene expression in hypothalamus of rats with experimental chronic renal failure
Sucajtys-Szulc E Karbowska J Kochan Z Wolyniec W Chmielewski M Rutkowski B Swierczynski J 《Biochimica et biophysica acta》2007,1772(1):26-31
Anorexia is possibly one of the most important causes of malnutrition in uremic patients. The cause of this abnormality is still unknown. Considering that: (a) NPY is one of the most important stimulants of food intake; (b) eating is a central nervous system regulated process and (c) NPY is expressed in hypothalamus, we hypothesized that the decrease of NPY gene expression in the hypothalamus could be an important factor contributing to anorexia associated with uremic state. In contrast to the prediction, the results presented in this paper indicate that the NPY gene expression in the hypothalamus of chronic renal failure (CRF) rats was significantly higher than in the hypothalamus of control (pair-fed) rats. Moreover, we found that serum NPY concentration in CRF rats was higher than in control (pair-fed) animals. The increase of plasma NPY concentration in CRF rats may be due to the greater synthesis of the neuropeptide in liver, since higher level of NPY mRNA was found in liver of CRF rats. The results obtained revealed that experimental chronic renal failure is associated with the increase of NPY gene expression in hypothalamus and liver of rats. 相似文献
886.
We applied the Cocktail method to a large data set of 4 117 relevés of all Slovak vegetation types with the aim to create
formalised definitions of all Slovakian mire plant associations. We defined 21 groups of species with the statistical tendency
of joint occurrences in vegetation. These groups differed substantially in their position along the pH/calcium gradient. We
further defined 24 plant associations according to presence and/or absence of certain groups and/or strong dominance of some
species. Only six traditional plant associations were not possible to be reproduced this way. We applied our formalised definitions
to the regional data set of mires from the surrounding of the Vysoké Tatry Mts. Combined with frequency-positive fidelity
index this method has led to the classification of the majority of vegetation plots into ten associations. When the vegetation
types obtained from Cocktail-based classification and from cluster analysis were compared with respect to measured pH and
conductivity in the study region, 82% of pairs differed significantly either in pH or in water conductivity in the former
classification and 69% in the latter one. 相似文献
887.
Jiří Masojídek Giuseppe Torzillo Michal Koblížek Jiří Kopecký Paola Bernardini Angelo Sacchi Josef Komenda 《Planta》1999,209(1):126-135
The role of the xanthophyll cycle in the adaptation of two chlorococcal algae Scenedesmus quadricauda and Chlorella sorokiniana to high irradiance was studied under laboratory and outdoor conditions. We wished to elucidate whether the xanthophyll cycle
plays a key role in dissipating the excesses of absorbed light, as in higher plants, and to characterise the relationship
between chlorophyll fluorescence parameters and the content of xanthophyll-cycle pigments. The xanthophyll cycle was found
to be operative in both species; however, its contribution to overall non-photochemical quenching (NPQ) could only be distinguished
in Scenedesmus (15–20% of total NPQ). The Scenedesmus cultures showed a larger pool of xanthophyll-cycle pigments than Chlorella, and lower sensitivity to photoinhibition as judged from the reduction of maximum quantum yield of photosystem II. In general,
both algae had a larger xanthophyll-cycle pool when grown outdoors than in laboratory cultures. Comparing the two species,
Scenedesmus exhibited a higher capacity to adapt to high irradiance, due to an effective quenching mechanism and high photosynthetic
capacity; in contrast, Chlorella represents a species with a larger antennae system, less-efficient quenching and lower photosynthetic performance. Non-photochemical
quenching (NPQ) induced through the xanthophyll cycle can, to a limited extent, represent a regulatory factor in diluted algal
cultures grown in outdoor solar photobioreactors, as well as in natural algal phytoplankton populations exposed transiently
to high irradiance. However, it does not play an appreciable role in dense, well-mixed microalgal suspensions.
Received: 6 August 1998 / Accepted: 12 February 1999 相似文献
888.
Characterization of the C-terminal domain essential for toxic activity of adenylate cyclase toxin 总被引:1,自引:0,他引:1
Michal Bejerano Israel Nisan Albrecht Ludwig Werner Goebel & Emanuel Hanski 《Molecular microbiology》1999,31(1):381-392
Adenylate cyclase toxin (CyaA) of Bordetella pertussis belongs to the RTX family of toxins. These toxins are characterized by a series of glycine- and aspartate-rich nonapeptide repeats located at the C-terminal half of the toxin molecules. For activity, RTX toxins require Ca2+ , which is bound through the repeat region. Here, we identified a stretch of 15 amino acids (block A) that is located C-terminally to the repeat region and is essential for the toxic activity of CyaA. Block A is required for the insertion of CyaA into the plasma membranes of host cells. Mixing of a short polypeptide composed of block A and eight Ca2+ binding repeats with a mutant of CyaA lacking block A restores toxic activity fully. This in vitro interpolypeptide complementation is achieved only when block A is present together with the Ca2+ binding repeats on the same polypeptide. Neither a short polypeptide composed of block A only nor a polypeptide consisting of eight Ca2+ binding repeats, or a mixture of these two polypeptides, complement toxic activity. It is suggested that functional complementation occurs because of binding between the Ca2+ binding repeats of the short C-terminal polypeptide and the Ca2+ binding repeats of the CyaA mutant lacking block A. 相似文献
889.
S Paraskevas R Aikin D Maysinger J R Lakey T J Cavanagh B Hering R Wang L Rosenberg 《FEBS letters》1999,455(3):203-208
Isolation and purification of islet cells exposes them to ischemic, osmotic and mechanical stresses. The objective of this study was to determine the roles of the MAP-kinases in islets immediately following isolation. During the first 48 h, activity of JNK1 and JNK2 declined markedly. Activity of p38 increased steadily with time in culture while extracellular signal regulated kinase (ERK) activity declined dramatically within 24 h post-isolation. High p38 activation relative to ERK activation immediately following isolation correlated with a decrease in islet survival after 36 h in culture. Absence and/or transiency of ERK signaling in conjunction with sustained activation of p38 pathway could be an important regulator of cell death in islets during and following their isolation by commonly employed procedures. 相似文献
890.
Production of fungal protein from oat hulls 总被引:1,自引:0,他引:1