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Basal Component (basal + component)
Selected AbstractsA Polygenetic Landform At Stígá, Örćfajökull, Southern IcelandGEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 2 2004Tim Harris Abstract Recent research has identified problems inherent in the identification and description of landforms. Morphologically similar small-scale glacial and periglacial landforms can be misinterpreted, thus hindering environmental reconstruction. This study reveals that a landform resembling a moraine at Stígárjökull, southern Iceland, is the product of both glacial deposition and mass movement. The landform has two distinct morphological and sedimentological components: a basal, lithologically diverse component, and an upper, lithologically homogenous component. Clast lithological analysis, particle shape and particle size measurements demonstrate that the basal component of the landform consists of sediment whose characteristics match nearby moraines. In contrast, the source of the upper component is a narrow outcrop of rock above the valley floor. Evidence suggests that frost-shattered material was transported across a perennial snow patch to a small moraine, leading to growth of the ,moraine'. This combination of processes is unlikely to be unique, but the geological peculiarities of the field site permitted their identification. It is possible that many similar ,moraines' could be enlarged by subaerial feeding, leading to false reconstruction of glacier form and/or associated rates of erosion and sedimentation. Such polygenetic landform genesis therefore has implications for environmental reconstruction. [source] Neurokinin B-producing projection neurons in the lateral stripe of the striatum and cell clusters of the accumbens nucleus in the ratTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 2 2004Ligang Zhou Abstract Neurons producing preprotachykinin B (PPTB), the precursor of neurokinin B, constitute 5% of neurons in the dorsal striatum and project to the substantia innominata (SI) selectively. In the ventral striatum, PPTB-producing neurons are collected mainly in the lateral stripe of the striatum (LSS) and cell clusters of the accumbens nucleus (Acb). In the present study, we first examined the distribution of PPTB-immunoreactive neurons in rat ventral striatum and found that a large part of the PPTB-immunoreactive cell clusters was continuous to the LSS, but a smaller part was not. Thus, we divided the PPTB-immunoreactive cell clusters into the LSS-associated and non-LSS-associated ones. We next investigated the projection targets of the PPTB-producing ventral striatal neurons by combining immunofluorescence labeling and retrograde tracing. After injection of Fluoro-Gold into the basal component of the SI (SIb) and medial part of the interstitial nucleus of posterior limb of the anterior commissure, many PPTB-immunoreactive neurons were retrogradely labeled in the LSS-associated cell clusters and LSS, respectively. When the injection site included the ventral part of the sublenticular component of the SI(SIsl), retrogradely labeled neurons showed PPTB-immunoreactivity frequently in non-LSS-associated cell clusters. Furthermore, these PPTB-immunoreactive projections were confirmed by the double-fluorescence method after anterograde tracer injection into the ventral striatum containing the cell clusters. Since the dorsalmost part of the SIsl is known to receive strong inputs from PPTB-producing dorsal striatal neurons, the present results indicate that PPTB-producing ventral striatal neurons project to basal forebrain target regions in parallel with dorsal striatal neurons without significant convergence. J. Comp. Neurol. 480:143,161, 2004. © 2004 Wiley-Liss, Inc. [source] Cell kinetic studies in murine ventral tongue epithelium: cell cycle progression studies using double labelling techniquesCELL PROLIFERATION, Issue 2002C. S. Potten Abstract. The dorsal and ventral epithelia on the murine tongue exhibit very pronounced circadian rhythms in terms of the cell cycle. These rhythms are such that three injections of tritiated thymidine 3 h apart spanning the circadian peak in S phase cells labelled between 40 and 50% of the basal cells. Injection of bromodeoxyuridine generally gave slightly lower labelling indices. Approximately the same proportion (54% of the basal cells) could be accumulated in metaphase over a 24-h period using vincristine as a stathmokinetic agent. The experiments reported here using mouse ventral tongue epithelium use double-labelling approaches to address the question: what proportion of the approximately 50% of the basal cells that are proliferating have a 24-h cell cycle and can therefore be labelled by a similar labelling protocol the following day? The results suggest a heterogeneity amongst the proliferating basal cells, similar to the heterogeneity proposed for the dorsal tongue epithelium. Although not all the basal component has been accounted for, the data presented here suggest that about 20% of the basal cells may have a cell cycle time of 24 h, about 30% appear to have a longer cell cycle time (48 or 72 h), while about 20% of the basal cells appear to be postmitotic maturing G1 cells, awaiting the appropriate signals for migration into the suprabasal layer. [source] Effects of phosphorylation by protein kinase CK2 on the human basal components of the RNA polymerase II transcription machineryJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 1 2004María Eugenia Cabrejos Abstract We have investigated the role of phosphorylation by vertebrate protein kinase CK2 on the activity of the General Transcription Factors TFIIA, TFIIE, TFIIF, and RNAPII. The largest subunits of TFIIA, TFIIE, and TFIIF were phosphorylated by CK2 holoenzyme. Also, RNA polymerase II was phosphorylated by CK2 in the 214,000 and 20,500 daltons subunits. Our results show that phosphorylation of TFIIA, TFIIF, and RNAPII increase the formation of complexes on the TATA box of the Ad-MLP promoter. Also, phosphorylation of TFIIF increases the formation of transcripts, where as phosphorylation of RNA polymerase II dramatically inhibits transcript formation. Furthermore, we demonstrate that CK2, directly interacts with RNA polymerase II, TFIIA, TFIIF, and TBP. These results strongly suggest that CK2 may play a role in regulating transcription of protein coding genes. © 2004 Wiley-Liss, Inc. [source] | ||||||||||