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151.
M Huber M Lindgren P Hammarstr?m L G M?rtensson U Carlsson G R Eaton S S Eaton 《Biophysical chemistry》2001,94(3):245-256
Phase memory relaxation times (T(M) or T(2)) of spin labels in human carbonic anhydrase II (HCA II) are reported. Spin labels (N-(1-oxyl-2,2,5,5-tetramethyl-3-pyrrolidinyl)iodoacetamide, IPSL) were introduced at cysteines, by site-directed mutagenesis at seven different positions in the protein. By two pulse electron paramagnetic resonance (EPR), electron spin echo decays at 45 K are measured and fitted by stretched exponentials, resulting in relaxation parameters T(M) and x. T(M) values of seven positions are between 1.6 micros for the most buried residue (L79C) and 4.7 micros for a residue at the protein surface (W245C). In deuteriated buffer, longer T(M) are found for all but the most buried residues (L79C and W97C), and electron spin echo envelop modulation (ESEEM) of deuterium nuclei is observed. Different deuterium ESEEM patterns for W95C and W16C (surface residue) indicate differences in the local water concentration, or accessibility, of the spin label by deuterium. We propose T(M) as a parameter to determine the spin label location in proteins. Furthermore, these systems are interesting for studying the pertaining relaxation mechanism. 相似文献
152.
G U Braga S D Flint C D Miller A J Anderson D W Roberts 《Journal of invertebrate pathology》2001,78(2):98-108
The effects of irradiances of 920 and 1200 mW m(-2) (biologically effective weighted irradiance) were examined in 2 Metarhizium album strains, 26 M. anisopliae strains, 1 M. flavoviride strain, and 1 M. taii strain isolated from sites located at latitudes from 61 degrees N to 54 degrees S. Conidia were exposed to UV-B from 1 to 6 h and subsequently examined for relative percentage culturability. Total dosage received at the end of the exposure periods ranged from 3.3 to 19.9 kJ m(-2) for the lower irradiance and from 4.3 to 25.9 kJ m(-2) for the higher irradiance. Both the irradiance values and the doses are environmentally realistic and can be observed even in temperate regions. The relationships between latitude of origin and UV-B tolerance were compared for the two levels of irradiance for the data from 1 and 2 h exposure. Exposure to both irradiances drastically reduced the relative percentage culturability of all strains. Tolerance to UV-B varied widely among strains and high variation was observed for both irradiances after all periods of exposure. After 1 h of exposure, a difference between the two irradiance levels was detectable, and this difference was magnified at longer irradiations. A significant quadratic relationship of decreasing UV-B tolerance with increasing latitude was observed after exposure of 1 and 2 h. The shape of the relationship did not differ for the two levels of irradiance. Also, we studied the effect of 1200 mW m(-2) irradiance on conidial germination time in 1 M. album strain, 7 M. anisopliae strains, and 1 M. taii strain. Exposure to UV-B delayed the germination of surviving conidia of all strains. In general, the delay in germination was directly proportional to the dose. 相似文献
153.
The aim of this study was to examine whether the spectral characteristics of tidal flow waveform reflect the interaction between the control of breathing and lung mechanics in 10 healthy infants (H), 10 infants with a history of wheezing disorders (W), and 10 infants with chronic lung disease (CLD). From the flow waveform, we calculated a shape index, the harmonic distortion (k(d)), which quantifies the extent to which a periodic signal deviates from a sine wave. The k(d) of the entire tidal flow waveform did not significantly discriminate between diagnostic groups. However, k(d) was sensitive to maturation: it increased from 0.26 at 1 mo to 0.37 at 6 mo of age (P < 0.002). Furthermore, the frequency (f) spectra of the flow (V) amplitudes between 0.13 and 10 Hz followed a power law: V(f) approximately f(-s), where s (slope) is the exponent in the power law. The exponent of the healthy infants s(H) was 4.24 [95% confidence interval (CI) = 0.2] at 1 mo, 4.39 (CI = 0.16) at 6 mo, and 4.35 (CI = 0.19) at 12 mo and not significantly changing with age. The mean value of s(W) was marginally lower (4.09 +/- 0.28; P < 0.05) than that of s(H). The mean s(CLD) was significantly lower (3.04 +/- 0.31; P < 0.001). Lower values of s and higher values of k(d) indicate an increased complexity of the feedback mechanisms determining tidal flow waveform and may be associated with disease. 相似文献
154.
Apterous is a LIM-homeodomain protein that confers dorsal compartment identity in Drosophila wing development. Apterous activity requires formation of a complex with a co-factor, Chip/dLDB. Apterous activity is regulated during wing development by dLMO, which competes with Apterous for complex formation. Here, we present evidence that complex formation between Apterous, Chip and DNA stabilizes Apterous protein in vivo. We also report that a difference in the ability of Chip to bind the LIM domains of Apterous and dLMO contributes to regulation of activity levels in vivo. 相似文献
155.
156.
R. Scheiden C. Wagener U. Knolle A. Wehenkel W. Dippel C. Capesius 《Cytopathology》2003,14(5):235-240
For quality assurance purposes, the results of the 1990's obtained by the National Cervical Cancer Screening Programme (NCCSP) launched in 1962 were reviewed. The positive cytodiagnosis, the histologically verified in situ and invasive cervical cancers and the mortality rates were reported. 相似文献
157.
DNA minor groove-binding compounds (polyamides) that target insect and vertebrate telomeric repeats with high specificity were synthesized. Base pair recognition of these polyamides is based on the presence of the heterocyclic amino acids pyrrole and imidazole. One compound (TH52B) interacts uniquely and with excellent specificity (K(d) = 0.12 nM) with two consecutive insect-type telomeric repeats (TTAGG). A related compound, TH59, displays high specificity (K(d) = 0.5 nM) for tandem vertebrate (TTAGGG) and insect telomeric repeats. The high affinity and specificity of these compounds were achieved by bidentate binding of two flexibly linked DNA-binding moieties. Epifluorescence microscopy studies show that fluorescent derivatives of TH52B and TH59 stain insect or vertebrate telomeres of chromosomes and nuclei sharply. Importantly, the telomere-specific polyamide signals of HeLa chromosomes co-localize with the immunofluorescence signals of the telomere-binding protein TRF1. Our results demonstrate that telomere-specific compounds allow rapid estimation of relative telomere length. The insect-specific compound TH52 was shown to be incorporated rapidly into growing Sf9 cells, underlining the potential of these compounds for telomere biology and possibly human medicine. 相似文献
158.
T J Kreeger A M Faggella U S Seal L D Mech M Callahan B Hall 《Journal of wildlife diseases》1987,23(3):463-470
Adult wolves (Canis lupus) were immobilized with 6.6 mg/kg ketamine hydrochloride (KET) and 2.2 mg/kg xylazine hydrochloride (XYL) administered intramuscularly. Induction time was 4.6 +/- 0.3 min (mean +/- SE). Immobilization resulted in significant bradycardia and hypertension (P less than 0.05). Twenty min after induction, the wolves were given 0.05-0.60 mg/kg yohimbine hydrochloride (YOH). Yohimbine given intravenously produced dose-related increases in heart rate (HR) with doses greater than 0.15 mg/kg resulting in extreme tachycardia (greater than 300 bpm). All doses of YOH caused a temporary decrease in mean arterial blood pressure (MABP) with some individual animals manifesting profound hypotension (less than 30 torr) at doses greater than 0.15 mg/kg. Increasing the dose of YOH above 0.15 mg/kg did not significantly decrease either arousal or ambulation times. Administering YOH at 40 or 60 min after induction resulted in decreased arousal and ambulation times. Stimulation by weighing and taking repeated blood samples during anesthesia did not shorten arousal times. We recommend that wolves immobilized with XYL-KET be antagonized with doses of YOH less than 0.15 mg/kg. 相似文献
159.
160.
Variation in the C:P ratio of suspended and settling seston and its significance for P uptake calculations 总被引:2,自引:0,他引:2
SUMMARY. 1. In 1981–84 limnocorral (LC) experiments were performed in Lake Lucerne. Switzerland, to manipulate the planktonic community by varying P fertilization and by removing large zooplankton (with a 95 μm screen).
2. The C:P ratios in both suspended and entrapped seston exceeded the 'ideal' C:P ratio of 106 proposed by Redfield, Ketchum & Richards (1963) when P was limiting algal growth.
3. P fertilization could decrease the sestonic C:P ratio to 106 only when P did not limit algal growth; P additions far exceeding the P loading of eutrophic lakes were necessary to obtain this situation.
4. Changes in epilimnetic C:P ratios were usually related to short- term changes in primary production, caused by variable in situ light conditions and turbulence, and subsequent variation in POC concentrations.
5. Entrapped seston in the 95 μm-filtered LCs showed C:P ratios slightly higher than those of suspended seston, indicating fast P release and slower C mineralization in the epilimnetic nutrient cycle.
6. Removing large crustacean zooplankton enhanced epilimnetic P mineralization, and C:P ratios of entrapped seston in the 95 μm-filtered LCs were increased.
7 Detritus formed a relatively high proportion of the seston and amounted to more than two-thirds of the measured POC concentration.
8. Calculations of algal P uptake using information on sestonic C:P ratios and14 C uptake rates are questionable, as long as detritus cannot be separated from algae and net carbon uptake cannot be accurately measured. 相似文献
2. The C:P ratios in both suspended and entrapped seston exceeded the 'ideal' C:P ratio of 106 proposed by Redfield, Ketchum & Richards (1963) when P was limiting algal growth.
3. P fertilization could decrease the sestonic C:P ratio to 106 only when P did not limit algal growth; P additions far exceeding the P loading of eutrophic lakes were necessary to obtain this situation.
4. Changes in epilimnetic C:P ratios were usually related to short- term changes in primary production, caused by variable in situ light conditions and turbulence, and subsequent variation in POC concentrations.
5. Entrapped seston in the 95 μm-filtered LCs showed C:P ratios slightly higher than those of suspended seston, indicating fast P release and slower C mineralization in the epilimnetic nutrient cycle.
6. Removing large crustacean zooplankton enhanced epilimnetic P mineralization, and C:P ratios of entrapped seston in the 95 μm-filtered LCs were increased.
7 Detritus formed a relatively high proportion of the seston and amounted to more than two-thirds of the measured POC concentration.
8. Calculations of algal P uptake using information on sestonic C:P ratios and