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241.
A N and N Nuclear Magnetic Resonance Study of Nitrogen Metabolism in Shoot-Forming Cultures of White Spruce (Picea glauca) Buds 下载免费PDF全文
Nitrogen-14 and nitrogen-15 nuclear magnetic resonance (NMR) spectra were recorded for freshly dissected buds of Picea glauca and for buds grown for 3, 6 and 9 weeks on shoot-forming medium. Resonances for Glu (and other αNH2 groups), Pro, Ala, and the side chain groups in Gln, Arg, Orn, and γ-aminobutyric acid could be detected in in vivo15N NMR spectra. Peaks for α-amino groups, Pro, NO3− and NH4+ could also be identified in 14N NMR spectra. Perfusion experiments performed for up to 20 hours in the NMR spectrometer showed that 15N-labeled NH4+ and NO3− are first incorporated into the amide group of Gln and then in the αNH2 pool. Subsequently, it also emerges in Ala and Arg. These data suggest that the glutamine synthetase/ glutamate synthase pathway functions under these conditions. The assimilation of NH4+ is much faster than that of NO3−. Consequently after 10 days of growth more than 70% of the newly synthesized internal free amino acid pool derives its nitrogen from NH4+ rather than NO3−. If NH4+ is omitted from the medium, no NO3− is taken up during 9 weeks and the buds support limited growth by utilizing their endogenous amino acid pools. It is concluded that NH4+ and NO3− are both required for the induction of nitrate- and nitrite reductase. 相似文献
242.
Peter?B.?GrayEmail author Judith?Flynn?Chapman Terence?C.?Burnham Matthew?H.?McIntyre Susan?F.?Lipson Peter?T.?Ellison 《Human nature (Hawthorne, N.Y.)》2004,15(2):119-131
Previous research in North America has supported the view that male involvement in committed, romantic relationships is associated
with lower testosterone (T) levels. Here, we test the prediction that undergraduate men involved in committed, romantic relationships
(paired) will have lower T levels than men not involved in such relationships (unpaired). Further, we also test whether these
differences are more apparent in samples collected later, rather than earlier, in the day. For this study, 107 undergraduate
men filled out a questionnaire and collected one saliva sample (from which a subject’s T level was measured) at various times
across the day. As in previous studies, men involved in committed, romantic relationships had lower salivary T levels, though
only during later times of the day. Furthermore, additional analysis of the variation among unpaired subjects indicated that
men without prior relationship experience had lower T levels than experienced men. Finally, while paired men as a group had
lower T levels than unpaired men, those men at the earliest stage (less than six months) of a current relationship had higher
T levels than unpaired men as well as men in longer-term relationships. These results suggest that variation in male testosterone
levels may reflect differential behavioral allocation to mating effort.
Peter Gray recently completed his Ph.D. in biological anthropology at Harvard with a dissertation entitled, "Human Male Reproductive
Strategies: Cross-Cultural and Endocrine Aspects." He is now a postdoctoral fellow at Charles Drew University of Medicine
and Science, working with Dr. Shalender Bhasin on human androgen research. Judith Flynn Chapman and Matthew McIntyre are Ph.D.
candidates inbiological anthropology at Harvard University. Judith Flynn Chapman focuses on variation in human ovarian function.
Matthew McIntyre studies the role of testosterone in psychological development.
Terry Burnham is an economist at the Harvard Business School. He studies economic behavior in a framework based in evolution
by natural selection.
Susan Lipson is a Lecturer in Anthropology and director of the Reproductive Ecology Laboratory at Harvard University. Her
research includes work on the effects of age and energy balance on female reproductive function, and on hormonal correlates
of conception and cancer risk.
Peter Ellison is John Cowles Professor of Anthropology and Dean of the Graduate School of Arts and Sciences at Harvard University.
He studies hormones, behavior, and the reproductive ecology of humans and nonhuman primates. 相似文献
243.
Proliferative effects of apical, but not basal, matrix metalloproteinase-7 activity in polarized MDCK cells 总被引:2,自引:0,他引:2
Harrell PC McCawley LJ Fingleton B McIntyre JO Matrisian LM 《Experimental cell research》2005,303(2):308-320
Matrix metalloproteinase-7 (MMP-7) is primarily expressed in glandular epithelium. Therefore, its mechanism of action may be influenced by its regulated vectorial release to either the apical and/or basolateral compartments, where it would act on its various substrates. To gain a better understanding of where MMP-7 is released in polarized epithelium, we have analyzed its pattern of secretion in polarized MDCK cells expressing stably transfected human MMP-7 (MDCK-MMP-7), and HCA-7 and Caco2 human colon cancer cell lines. In all cell lines, latent MMP-7 was secreted to both cellular compartments, but was 1.5- to 3-fold more abundant in the basolateral compartment as compared to the apical. However, studies in the MDCK system demonstrated that MMP-7 activity was 2-fold greater in the apical compartment of MDCK-MMP-7(HIGH)-polarized monolayers, which suggests the apical co-release of an MMP-7 activator. In functional assays, MMP-7 over-expression increased cell saturation density as a result of increased cell proliferation with no effect on apoptosis. Apical MMP-7 activity was shown to be responsible for the proliferative effect, which occurred, as demonstrated by media transfer experiments, through cleavage of an apical substrate and not through the generation of a soluble factor. Taken together, our findings demonstrate the importance of MMP-7 secretion in relation to its mechanism of action when expressed in a polarized epithelium. 相似文献
244.
McIntyre M Eade JK Cox PW Thomas CR White S Berry DR McNeil B 《Canadian journal of microbiology》2001,47(4):315-321
An image analysis method is described for the characterization of empty (autolyzed and inactive) regions within the mycelia of filamentous fungi. It extends a previous method that characterized only regions filled with cytoplasm or vacuoles (i.e., the active biomass). The method is semiautomatic, requiring some manual editing before automated measurements. When the method was used for samples from a batch fermentation of an industrial strain of Penicillium chrysogenum, the empty regions were observed to constitute up to 15% (by projected area) of the biomass during the growth phase. After nutrient exhaustion, however, the proportion of empty regions rose rapidly, eventually representing more than 50% of the biomass by the end of fermentation. The increase in the percentage of empty regions coincided with a decrease in biomass (as measured by dry cell weight) and a fall in penicillin titre. Further morphological analysis revealed that fragmentation of mycelia, particularly clumps, coincided with increases in the levels of empty regions. This new image analysis method gave additional information on hyphal differentiation and a measure of autolysis. It was also a useful indicator of the processes leading to autolysis. 相似文献
245.
DNA sequencing has been used to construct two molecular phylogenies at the intrafamily and intrageneric level within the Rutaceae. Analysis oftrnL-trnF sequence data for five Rutaceae subfamilies has shown that there is no molecular support for the current subfamily classifications within the Rutaceae. The Dictyolomatoideae and Spathelioideae belong to a clade separate from the clades containing the remaining Rutaceae subfamilies. Rutoideae and Citroideae do not form discrete clades which suggests a reassessment of the subfamily classification is necessary, particularly asRuta falls within the majority Citroideae clade. Flindersioideae forms a clade within the Rutaceae and does not form a separate family or form a clade with Meliaceae.Sequencing of 17Flindersia species produces a similar phylogeny to that proposed by other authors using morphological methods with two exceptions. The molecular phylogeny indicatesF. amboinensis is associated withF. fournieri andF. laevicarpa and, in addition,F. oppositifolia andF. pimenteliana were found to be genetically identical. 相似文献
246.
247.
Pacofsky GJ Stafford JA Cox RF Cowan JR Dorsey GF Gonzales SS Kaldor I Koszalka GW Lovell GG McIntyre MS Tidwell JH Todd D Whitesell G Wiard RP Feldman PL 《Bioorganic & medicinal chemistry letters》2002,12(21):3219-3222
The ultrashort-acting benzodiazepine (USA BZD) agonists reported previously have been structurally modified to improve aqueous solubility. Lactam-to-amidine modifications, replacement of the C5-haloaryl ring, and annulation of heterocycles are presented. These analogues retain BZD receptor potency and full agonism profiles. 相似文献
248.
Introduction
While the directionality of tactile motion processing has been studied extensively, tactile speed processing and its relationship to direction is little-researched and poorly understood. We investigated this relationship in humans using the ‘tactile speed aftereffect’ (tSAE), in which the speed of motion appears slower following prolonged exposure to a moving surface.Method
We used psychophysical methods to test whether the tSAE is direction sensitive. After adapting to a ridged moving surface with one hand, participants compared the speed of test stimuli on the adapted and unadapted hands. We varied the direction of the adapting stimulus relative to the test stimulus.Results
Perceived speed of the surface moving at 81 mms−1 was reduced by about 30% regardless of the direction of the adapting stimulus (when adapted in the same direction, Mean reduction = 23 mms−1, SD = 11; with opposite direction, Mean reduction = 26 mms−1, SD = 9). In addition to a large reduction in perceived speed due to adaptation, we also report that this effect is not direction sensitive.Conclusions
Tactile motion is susceptible to speed adaptation. This result complements previous reports of reliable direction aftereffects when using a dynamic test stimulus as together they describe how perception of a moving stimulus in touch depends on the immediate history of stimulation. Given that the tSAE is not direction sensitive, we argue that peripheral adaptation does not explain it, because primary afferents are direction sensitive with friction-creating stimuli like ours (thus motion in their preferred direction should result in greater adaptation, and if perceived speed were critically dependent on these afferents’ response intensity, the tSAE should be direction sensitive). The adaptation that reduces perceived speed therefore seems to be of central origin. 相似文献249.
Nicholas M. Selby Nitin V. Kolhe Christopher W. McIntyre John Monaghan Nigel Lawson David Elliott Rebecca Packington Richard J. Fluck 《PloS one》2012,7(11)
Background
The high mortality rates that follow the onset of acute kidney injury (AKI) are well recognised. However, the mode of death in patients with AKI remains relatively under-studied, particularly in general hospitalised populations who represent the majority of those affected. We sought to describe the primary cause of death in a large group of prospectively identified patients with AKI.Methods
All patients sustaining AKI at our centre between 1st October 2010 and 31st October 2011 were identified by real-time, hospital-wide, electronic AKI reporting based on the Acute Kidney Injury Network (AKIN) diagnostic criteria. Using this system we are able to generate a prospective database of all AKI cases that includes demographic, outcome and hospital coding data. For those patients that died during hospital admission, cause of death was derived from the Medical Certificate of Cause of Death.Results
During the study period there were 3,930 patients who sustained AKI; 62.0% had AKI stage 1, 20.6% had stage 2 and 17.4% stage 3. In-hospital mortality rate was 21.9% (859 patients). Cause of death could be identified in 93.4% of cases. There were three main disease categories accounting for three quarters of all mortality; sepsis (41.1%), cardiovascular disease (19.2%) and malignancy (12.9%). The major diagnosis leading to sepsis was pneumonia, whilst cardiovascular death was largely a result of heart failure and ischaemic heart disease. AKI was the primary cause of death in only 3% of cases.Conclusions
Mortality associated with AKI remains high, although cause of death is usually concurrent illness. Specific strategies to improve outcomes may therefore need to target not just the management of AKI but also the most relevant co-existing conditions. 相似文献250.