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Central nervous system (CNS) stem cells have become the subject of many laboratories' efforts, presentations, and publications. Yet, in the stem cell world, CNS cells are viewed with skepticism. This is likely due to a dearth of biology (in vivo function) to accompany a flurry of phenomenological and restorative neurology studies. In this article, we compare and contrast the biological knowledge of adult forebrain epidermal growth factor-responsive neural stem cells that has emerged from our laboratories with that of hematopoietic stem cells, using two recent papers in the latter field as specific examples. A comparison of stem cell location, lineage, and repopulation suggests that our understanding of CNS stem cell biology is immature. We conclude that a greater focus on in vivo biology will enhance our knowledge and understanding of CNS stem cells. © 1998 John Wiley & Sons, Inc. J Neurobiol 36: 307–314, 1998 相似文献
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Pavlov's concept of conditioned reflexes and Ukhtomskii theory of dominanta fall within the biological line in physiology. They unravel the integral adaptive and active nature of the organism behavior in the environment. It is impossible to develop modern concepts about the determinants of goal-directed behavior of animals and voluntary activity of humans without in-depth study of the achievements of these Russian physiological schools which not only formed the methodological basis for the current studies but also directed the way for their further development. 相似文献
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Jany Renz 《Plant Systematics and Evolution》1987,155(1-4):3-5
K. H. Rechinger's great botanical life-work and its impulses on plant geography and taxonomy are estimated.Address toKarl Heinz Rechinger, held on October 18, 1986. 相似文献
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André F. Lotter Oliver Heiri Wolfgang Hofmann Willem O. van der Knaap Jacqueline F. N. van Leeuwen Ian R. Walker Lucia Wick 《Vegetation History and Archaeobotany》2006,15(4):295-307
Palaeobotanical analysis and radiocarbon dating of lake sediments from Bachalpsee (2265 m a.s.l.), a small lake above the present-day timber-line in the northern Swiss Alps reveals that the region was already deglaciated during the Younger Dryas. The sediment record is dominated by long-distance transported pollen that originates from lowland vegetation but the plant macrofossils give evidence of the local vegetation development. Comparison with palaeobotanical results from three sites along an altitudinal transect permits the reconstruction of the regional timber-line history. Throughout the entire Holocene the catchment of Bachalpsee consisted of a mosaic of open meadows and dwarf shrubs (Salix, Vaccinium, Rhododendron). Chironomid and cladoceran assemblages suggest that the early to mid-Holocene was the warmest interval at Bachalpsee. Comparison of the palaeobotanical results with those from the mire “Feld” (2130 m a.s.l.) in the vicinity of Bachalpsee showed that during the mid-Holocene the timber-line was formed by Pinus cembra and Picea abies with some scattered Abies alba trees and was situated close to Bachalpsee but never reached its catchment. The maximum timber-line in the Northern Alps was reached between 6000 and 3000 cal b.p. which is several millennia later than in the Central Alps. The species composition of the tree-line (Abies alba, Pinus cembra and the absence of Larix decidua) points to less continental and moister climatic conditions compared with the central Alps during the early to mid-Holocene. From 3000 cal b.p. onwards the timber-line was lowered by human deforestation with the most intense pulses of human impact occurring since the Middle Ages. The catchment of Bachalpsee has been used as alpine pasture since the Bronze Age. 相似文献
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Chen Chia-Jui 《植物分类学报:英文版》1980,18(4):476-481
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M. Th. Smith J. P. van der Walt W. H. Batenburg-van der Vegte 《Antonie van Leeuwenhoek》1995,67(2):177-179
The species described asLipomyces anomalus Babjeva & Gorin shows significant genetic and phenotypic divergence from the type speciesLipomyces starkeyi Lodder & Kreger-van Rij in terms of rRNA base sequence substitution and ascosporal and septal ultrastructure. The species is consequently reclassified in the new, unispecific genusBabjevia, asBabjevia anomala. 相似文献
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《中国实验动物学报》2016,(6)
目的在我们的前期研究工作中,通过Tol2转座子介导的插入突变,筛选到了一批组织特异性表达绿色荧光蛋白GFP的斑马鱼品系。其中一个品系Tol2:20141221t的GFP在神经系统中表达,但还没有鉴定到Tol2转座子插入到基因组什么位置,造成了哪个基因的突变。本文的主要研究目标就是对这一由Tol2转座子插入诱导的斑马鱼突变品系进行鉴定。方法使用交错式热不对称PCR(thermal asymmetric interlaced PCR,TAIL-PCR)鉴定Tol2转座子插入的基因组位置;利用原位杂交检测被突变的基因的时空表达是否与该品系GFP表达具有一致性;筛选鉴定纯合体突变体,并进一步分析该基因突变造成的发育缺陷。结果在该品系中,Tol2转座子插入到了亚精胺/精胺N1-乙酰基转移酶1a(spermidine/spermine N1-acetyltransferase 1a,sat1.a)的第八个内含子区域,致使sat1.a基因转录提前终止。我们筛选到了sat1.a纯合突变体,但是没有检测到明显的发育缺陷。结论筛选鉴定的Tol2转座子介导的斑马鱼sat1.a突变体没有明显的发育缺陷,但可以作为研究神经系统发育的有力工具。 相似文献
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Angiopteris sparsisora Ching, sp. nov.
Species nova ab omnibus affinibus adhuc cognitis recedit rhizomate repente, dorsiventrali, habitu minore stipite tenui, levi, paleis brunneis lineari-lanceolatis margine
irregulariter fimbriatis peltati-fixis, pinnulis basi cuneatis vel late cuneatis, distincte
breviterque petiolulatis, soris longitudine variis, inter se separatis a margine magis remotis, paraphysibus rudimentalibus brevibus sparse praesentibus.
Tota planta 1—1.2 m alata, rhizomate repente, carnoso, cylindrico, dorsiventrali, 5—6 cm diametro, radicoso, apice frondes 2—3 emittente, stipite 35—70 cm longo, 4—8 mm crasso, levi viridi, supra medium uni-geniculato (in frondibus pinnatis usque subbipinnatis), paleis brunneis lineari-lanceolatis basi rotunda peltati-fixis margine varie fimbriatis sparse vestito; lamina stipite longiore, bipinnata aut subb ipinnata raro superne simpliciter pinnata; pinnis 2—3(—7)-jugis, ,alternis vel suboppositis, oblongis, 45—55 cm longis, 18—23 cm latis, petiolo 4—16 cm longo suffultis, basi tumidis, pinnatis vel interdum simplicibus vel basi pinnatifidis; pinnulis plerumque 8—12-jugis, alternis vel
suboppositis, patentibus, 8—18 cm longis, medio 1.5—3cm latis, lanceolatis, acuminatis,
basin versus cuneatis vel late cuneatis, breviter petiolatis, pinnula terminali confomi
paulo majore, petiolulata, hasi baud in alas decurrente, margine serrulatis; venis utrinquo distinctis, patentibus, simplicibus vel furcatis, prope marginem curvatis; pagina
frondis textura in sicco virescente, chartacea, rachi, costis, costulis venisque subtus
sparsim minuteque paleaceis. Soris breviter linearibus, 2—4 mm longis, 10—32-sporangiatis, inter se separatis, a margine 2—3 mm, remotis; paraphysibus sparsis brevibusrudimentalibus. Sporis globulosis, suparficie dense tubuculatis.
Yunnan austro-orientalis: Xichou Xian, Fadou, S. K. Wu 4203 (typus, PE), 4198,
8, October, 1962; ibidem, Z. R. Wang 566-1, 566-2, 566-3, 566-4, 566-5, 15, January,
1978; ibidem V. M. Chu 8212, 15, January, 1978. in valley under evergreen broadleaved forests, alt. 1500—1550m.
In the tropical rain forest in southeastern Yunnan, China, the members of Angiopteris Hoffm. and Archangiopteris Christ et Gies. are often growing side by side in great
abundance. In January 1978 the second writer made a botantical trip there and collected in one locality ample herbarium material of an Angiopteris, which is identical
with A. sparsisora Ching (ined.), based upon type specimens gathered by Mr. S. K. Wu
from the same locality in 1962. To our great surprise, however, this distinct taxon
reveals a number of important morphological characteristics intermediate between Angiopteris and Archangiopteris as diagnosed above.
The present species resembles Archangiopteris in small build with creeping dorsiventral rhizome, unigeniculate, thin, smooth stipe in pinnate to bipinnatifid fronds, sparingly clad in linear-lanceolate peltately affixed scales with variously fimbriate margin,
lamina 1—2 pinnate or subbipinnate, pinnules distinctly and shortly stipitate, base
cuneate or broadly cuneate, sori of different length separated from each other by broad
spaces, and rather far away (2—3 mm) from the margin, paraphyses few, rudimentary
and short, but, on the other hand, it also similar to Angiopteris in usually bipinnate
fronds, the petiole of pinnae with swollen base (blackish upon drying), short (2—4 mm
long) linear sori consisting of 5—16 pairs of sporangia and globulax spores with densely
tubucular sporoderms. All the above characteristics combined clearly indicate the species is in all likelihood a natural hybrid between Angiopteris and Archangiopteris,
pending cytological investigation and the reason for presently placing it in Angiopteris
rather than in Archangiopteris is because of the fact that in overall impression the newtaxon appears more like the former than the latter. 相似文献
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Anaerobic enrichment culture with thiocyanate as electron donor and nitrate as electron acceptor at 2 M NaCl inoculated with
a mixture of sediments from hypersaline lakes in Kulunda Steppe (Altai, Russia) resulted in a selection of a binary consortium
of moderately halophilic, obligately chemolithoautotrophic sulfur-oxidizing bacteria (SOB) capable of complete denitrification
of nitrate with thiosulfate as the electron donor. One consortium member, strain HRhD 3sp, was isolated into pure culture
with nitrate and thiosulfate using a density gradient. This strain was responsible for the reduction of nitrate to nitrite
in the consortium, while a second strain, HRhD 2, isolated under microoxic conditions with thiosulfate as substrate, was capable
of anaerobic growth with nitrite and thiosulfate. Nitrite, either as substrate or as product, was already toxic at very low
concentrations for both strains. As a result, optimal growth under anaerobic conditions could only be achieved within the
consortium. On the basis of phylogenetic analysis, both organisms were identified as new lineages within the Gammaproteobacteria. As well as thiosulfate, strain HRhD 2 can also use thiocyanate as electron donor, representing a first halophilic SOB capable
of growth with thiocyanate at 2–4 M NaCl. Product and enzymatic analysis identified the “carbonyl sulfide (COS) pathway” of
primary thiocyanate degradation in this new species. On the basis of phenotypic and genetic analysis, strain HRhD 2 is proposed
to be assigned to a new genus and species Thiohalophilus thiocyanoxidans.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献