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941.
Rainer Scharf Malte Meesmann Jan Boese Dante R. Chialvo Klaus -D. Kniffki 《Biological cybernetics》1995,73(3):255-263
Counting statistics in the form of the variance-time curve provides an alternative to spectral analysis for point processes exhibiting 1/f β-fluctuations, such as the heart beat. However, this is true only for β<1. Here, the case of general β is considered. To that end, the mathematical relation between the variance-time curve and power spectral density in the presence of 1/f β-noise is worked out in detail. A modified version of the variance-time curve is presented, which allows us to deal also with the case β?1. Some applications to the analysis of heart rate variability are given. 相似文献
942.
Smooth-pursuit eye movements were recorded in two rhesus monkeys in order to compare the influence of structured visual backgrounds
on smooth-pursuit initiation, steady-state pursuit and pursuit termination. Different target trajectories were used in order
to study smooth-pursuit initiation and termination. The influence of visual backgrounds on pursuit initiation was characterized
by recording ocular responses elicited by step-ramp target displacements starting from straight ahead. Pursuit termination
was characterized by analysing the transition from steady-state smooth-pursuit to fixation when a centripetally directed target
ramp was terminated by a small target step in the direction of the ramp as soon as the target had come close to the straightahead
position. The quantification of steady-state pursuit was based on ocular responses elicited by either paradigm. In accordance
with previous work, we found that the onset of smooth-pursuit eye movements was delayed and initial eye acceleration reduced
in the presence of a structured visual background. Likewise, mean eye velocity during steady-state pursuit was reduced by
structured visual backgrounds. However, neither the latency nor the time course of smooth-pursuit termination was altered
when the homogeneous background was replaced by a structured visual background. The lack of sensitivity of pursuit termination
to the presence of visual structured backgrounds supports a previous contention that pursuit termination is mediated by a
process which is different from the ones mediating smooth-pursuit initiation and steady-state pursuit. The absence of any
noticeable effect of structured backgrounds on pursuit termination suggests that at least the fast component of the optokinetic
reflex is suppressed during pursuit termination.
Received: 24 October 1994/Accepted in revised form: 16 December 1994 相似文献
943.
Peter N. Robinson Annett Böddrich Hartmut Peters Sigrid Tinschert Annegret Buske Dieter Kaufmann Peter Nürnberg 《Human genetics》1995,96(1):95-98
We screened a total of 92 unrelated patients with neurofibromatosis type 1 (NF1) for mutations in exon 37 of the NF1 gene, by using temperature gradient gel electrophoresis. Two novel mutations were found: a 4 bp deletion in a so-called quasi-symmetric element (6789delTTAC) and a recurrent nonsense mutation, which was identified in two unrelated patients, at codon 2264 (C6792A). The independent origin of the latter mutation in two families was confirmed by haplotype analysis. The nonsense mutation and the 4 bp deletion are both predicted to lead to a truncated protein product lacking the Cterminal 20% (aproximately) of its sequence. The occurrence of three independent mutations among 92 NF1 patients at codons 2263–2264 (exon 37) suggests that a specific search for mutations in this area should be undertaken in screening programs for NF1 mutations. 相似文献
944.
Therapy of bovine ocular squamous-cell carcinoma with local doses of interleukin-2: 67% complete regressions after 20 months of follow-up 总被引:1,自引:1,他引:0
F. W. Willem Den Otter Graham Hill Wim R. Klein Jan Willem Koten Peter A. Steerenberg Pieter H. M. De Mulder Christopher Rhode Rachel Stewart Joop A. J. Faber E. Joost Ruitenberg Victor P. M. G. Rutten 《Cancer immunology, immunotherapy : CII》1995,41(1):10-14
We have tested the therapeutic potency of peritumorally injected low doses of interleukin-2(IL-2). Seventy tumours of the bovine ocular squamous-cell carcinoma (BOSCC), 1–3 cm in diameter, were treated with 5000, 20 000 or 200 000 U IL-2 from Eurocetus (Chiron) to find the optimal dose for treatment. Injections were given peritumorally on Monday to Friday on 2 consecutive weeks. The size of the tumours was measured before treatment and 1, 3, 4, 9 and 20 months after treatment. After 9 months complete regression was observed in 89% of the tumours treated with 5000 U IL-2, 80% treated with 20 000 U and 67% treated with 200 000 U. After 20 months, there was complete regression of 35%, 31% and 67% of the tumours respectively. The 9-and 20-month results of the 200 000-U treatment are significantly better than those of the 5000-U and 20 000-U treatments taken together. This protocol may be useful to treat advanced inoperable tumours (e.g. of the nasopharynx or skin) of human patients. 相似文献
945.
The heat shock and ethanol stress responses of yeast exhibit extensive similarity and functional overlap 总被引:19,自引:0,他引:19
Peter W. Piper 《FEMS microbiology letters》1995,134(2-3):121-127
Abstract We examined the penicillin-binding proteins (PBPs) of certain field strains of Streptococcus suis , as well as those from laboratory variants having different degrees of resistance to penicillin. Results indicated that (i) S. suis possesses three distinct groups of PBPs, arbitrarily named here PBP 1, PBP 2, and PBP 3, with approximate molecular weights of 97, 82, and 45 kDa respectively; (ii) PBP profiles of field strains of S. suis having different MICs (≤ 0.03 to 16.0 μg/ml) were not uniform (PBP 2 being difficult to detect in strains whose MICs exceeded 0.10 μg/ml, and PBP 3 which exhibited shifts in molecular weight of approximately 5 kDa); (iii) laboratory variant PBPs 1 and 2 showed decreased affinity for penicillin as compared to the parent strain in antibiotic competition experiments, even though the PBP profiles of both were similar. We suggest that PBP modifications (altered molecular weight and/or decreased affinity for penicillin) are involved in the mechanism of resistance to penicillin by S. suis . 相似文献
946.
Peter F. Hall 《Molecular neurobiology》1995,10(1):1-17
Endozepine has recently been isolated from various steroid-forming organs. The following article explores the role of endozepine
in the regulation of steroid synthesis. Steroid hormone synthesis from cholesterol begins in the inner mitochondrial membrane,
where cytochrome P450 converts cholesterol to pregrenolone. Scientists thought that ACTH would stimulate this conversion,
but experiments showed no such stimulation. However, addition of aminoglutethimide to block side-chain cleavage caused the
expected reaction of ACTH to take place. Next the role of protein synthesis on the actions of ACTH was explored. Then endozepine
was isolated from bovine fasciculata based on stimulation of pregnenolone production by freshly prepared mitochondria. After
further experimentation it was concluded that endozepine is a peptide with at least two groups of actions: It binds GABAA receptors in the central nervous system, and it increases the mitochondrial synthesis of pregnenolone. 相似文献
947.
948.
Frieder Schauer Kirsten Henning Helmut Pscheidl Rolf M. Wittich Peter Fortnagel Heinz Wilkes Volker Sinnwell Wittko Francke 《Biodegradation》1995,6(2):173-180
Trichosporon beigelii SBUG 752 was able to transform diphenyl ether. By TLC, HPLC, GC, GC-MS, NMR- and UV-spectroscopy, several oxidation products were identified. The primary attack was initiated by a monooxygenation step, resulting in the formation of 4-hydroxydiphenyl ether, 2-hydroxydiphenyl ether and 3-hydroxydiphenyl ether (48:47:5). Further oxidation led to 3,4-dihydroxydiphenyl ether. As a characteristic product resulting from the cleavage of an aromatic ring, the lactone of 2-hydroxy-4-phenoxymuconic acid was identified. The possible mechanism of ring cleavage to yield this metabolite is discussed. 相似文献
949.
Peter Sowig 《Ecography》1995,18(2):147-154
Paracoprid dung beetles build brood chambers in the soil beneath a dung pat and provide them with dung Onthophagus species lay one egg into each chamber This paper deals with the influence of soil type and soil moisture on micro-habitat selection and survival of offspring m three middle-European Onthophagus-species ( O coenobita, O fracticonis and O vacca) Discrimination between sandy soils with three different loam contents (0%, 20%, 40%) and four different water contents (4%, 8%, 12%, 16%) was tested in the laboratory During the first 24 h of each replicate beetles which colonized one of the patches did not distinguish between different soil conditions Emigration rates, measured as time when 50% of all individuals had left the patch, and numbers of brood chambers proved to be species specific and depended on soil moisture and soil type Survival rates of the larvae in the brood chambers were influenced nearly exclusively by soil moisture The results are discussed in relation to the ecology of the three species and in context with optimal foraging theories 相似文献
950.
Summary Proton chemical shifts of a series of disordered linear peptides (H-Gly-Gly-X-Gly-Gly-OH, with X being one of the 20 naturally
occurring amino acids) have been obtained using 1D and 2D 1H NMR at pH 5.0 as a function of temperature and solvent composition. The use of 2D methods has allowed some ambiguities in
side-chain assignments in previous studies to be resolved. An additional benefit of the temperature data is that they can
be used to obtain ‘random coil’ amide proton chemical shifts at any temperature between 278 and 318 K by interpolation. Changes
of chemical shift as a function of trifluoroethanol concentration have also been determined at a variety of temperatures for
a subset of peptides. Significant changes are found in backbone and side-chain amide proton chemical shifts in these ‘random
coil’ peptides with increasing amounts of trifluoroethanol, suggesting that caution is required when interpreting chemical
shift changes as a measure of helix formation in peptides in the presence of this solvent. Comparison of the proton chemical
shifts obtained here for H-Gly-Gly-X-Gly-Gly-OH with those for H-Gly-Gly-X-Ala-OH [Bundi, A. and Wüthrich, K. (1979) Biopolymers, 18, 285–297] and for Ac-Gly-Gly-X-Ala-Gly-Gly-NH2 [Wishart, D.S., Bigam, C.G., Holm, A., Hodges, R.S. and Sykes, B.D. (1995) J. Biomol. NMR, 5, 67–81] generally shows good agreement for CH protons, but reveals significant variability for NH protons. Amide proton chemical
shifts appear to be highly sensitive to local sequence variations and probably also to solution conditions. Caution must therefore
be exercised in any structural interpretation based on amide proton chemical shifts. 相似文献