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1.
Abstract

Long‐period (1948–1967) correlations have been statistically determined for the frequency of occurrence of solar flares associated with type IV radio bursts, negative variation of cosmic ray level, geomagnetic indices AP, lower ionospheric absorption, polar vortex activity in the circumpolar pressure field pattern and long‐term microseismic activity, expressed in statistical variations of amplitudes and periods of meteorological microseisms down to latitudes of about 35° N. All of the characteristics mentioned exhibit the same type of changes even in the time position of secondary maxima while only a rough similarity was observed with respect to the correlation of sunspot numbers and A= 10.7 cm solar radio flux. As a whole this represents a wide scale of interactions between the space‐solar phenomena and physical fields of the earth.  相似文献   

2.
This study aimed to evaluate the ability of commercial soy protein isolate (SPI) to form cold-set gels under different pHs (5–11), pre-heating temperatures (60 °C, 80 °C), CaCl2 (0–15 mM) and SPI (5–15%, w/v) concentrations, and also select a formulation for the investigation of the effects of incorporating locust bean gum (LBG) (0–0.3%, w/v) and solid lipid microparticles (SLM) on gels rheological and microstructural properties. Gels were evaluated in terms of visual aspect, water-holding capacity, microstructure (using confocal laser scanning microscopy and cryo-scanning electronic microscopy) and rheological properties. SPI showed higher solubilities at pHs 7 (32.0%), 9 (51.6%) and 11 (100%). Self-supported gels were obtained under several conditions at alkaline pHs. At pH 7, only systems pre-heated to 80 °C with 15% (w/v) SPI and 10 or 15 mM CaCl2 gave self-supported gels. At neutral pH, samples showed relative structural instability, which was minimized with LBG incorporation. Formulations GSPI (pH 7, preheated to 80 °C, 15% (w/v) SPI, 10 mM CaCl2) and GMIX (pH 7, preheated to 80 °C, 15% (w/v) SPI, 0.2% (w/v) LBG, 15 mM CaCl2) were selected for emulsion-filled gels (EFG) production. Power law parameters (K′, K″), calculated from frequency sweep results, revealed that non-filled GMIX (K′: 472.1; K″: 77.6) was stronger than GSPI (K′: 170.4; K″: 33.6). Besides, GMIX showed microphase separation. SLM stabilized with Tween 80-Span 80 were active fillers in EFG, altering microstructures and increasing G’, G” and the Young’s modulus (1.8 to 2.1 kPa for GSPI and 1.4 to 2.2 kPa for GMIX).  相似文献   

3.
Variation in particular biochemical indicators, cytokine and adipokine profile parameters of the blood, and the structural and functional parameters of the liver have been studied in patients with nonalcoholic fatty liver disease (NAFLD) and different genotypes by the polymorphic locus A313G of GSTP gene (rs 1695). It has been established that the G allele of the GSTP gene (A313G) is significantly more frequently met in NAFLD patients than in healthy individuals. Higher activity of alanine aminotransferase and higher level of leptin, as well as lower adiponectin blood content, were recorded in the carriers of the G allele of the GSTP gene (A313G) as compared to patients with the given gene AA genotype. Higher interleukin-10 blood content was also observed in homozygous G allele carriers of NAFLD patients compared with the patients with the AA and AG genotypes. The patients with the G allele of the GSTP1 gene had a larger right lobe of liver than homozygous carriers of the given gene A allele.  相似文献   

4.
An extensive analysis of Ulysses observations of the solar wind speed V from 1990 to 2008 is undertaken. It is shown that the evolution of V with heliocentric distance r depends substantially on both the heliolatitude and the solar activity cycle. Deviations from the predicted Parker’s profile of V(r) are so considerable that cannot be explained by a scarcity of measurements or other technical effects. In particular, the expected smooth growth of the solar wind speed with r is typical only for the solar activity maximum and for low heliolatitudes (lower than ±40°), while at high latitudes, there are two V(r) branches: growing and falling. In the solar activity maximum, V increases toward the solar pole in the North hemisphere only; however, in the South hemisphere, it decreases with heliolatitude. In the minimum of solar activity, the profile of V(r) at low heliolatitudes has a local minimum between 2 and 5 AU. This result is confirmed by the corresponding data from other spacecraft (Voyager 1 and Pioneer 10). Unexpected spatial variations in V at low heliolatitudes can be explained by the impact of coronal hole flows on the V(r) profile since the flows incline to the ecliptic plane. To reproduce the impact of spatial variations of V in the polar corona on the behavior of V at low heliolatitudes, a stationary one-fluid ideal MHD-model is developed with account of recent results on imagery of the solar wind speed in the corona up to 5.5 solar radii obtained on the basis of combined observations from SOHO/UVCS, LASCO, and Mauna Loa.  相似文献   

5.
Eggshells of Nematodirus battus leaked trehalose 4 hr after being stimulated to hatch, and became permeable to trypan blue at their poles; 80% of eggs were stained blue 24 hr later. Exogenous application of ruthenium red significantly inhibited chill- and sodium fluoride-stimulated hatching, 50% hatch inhibition occurring in 44.67 ± 2.2 and 8.5 ± 1.5 μM, respectively. Lanthanum chloride, however, was not as inhibitory as ruthenium red on fluoride-stimulated hatching, 50% occurring at 31.60 ± 1.25 μM. A Scatchard plot of the competitive binding of ruthenium red to eggshells demonstrated a high-affinity binding site for calcium, KCa′ = 1.92 μM and a second, low-affinity site, KCa′ = 1169.60 μM. Ruthenium red binding was significantly reduced by several enzymes, e.g., EGTA-buffered trypsin reduced binding by 73%. Radioiodinated concanavalin A also bound competitively to the eggshells in the presence of α-d-glucosyl-α-d-glucopyranoside and α-methyl-d-mannopyranoside. Eggshells incorporated phosphorus-32 from ATP after chilling or on exposure to sodium fluoride; gel filtration of solubilized homogenates of these samples showed that two proteins were radiolabelled with molecular weights of 38 × 103 and 8 × 103 Da, respectively. This phosphorylation was inhibited by N-ethylmaleimide, which also prevented hatching.  相似文献   

6.
The dependence of the heterotrophic activity of bacterioplankton (V, μg C L–1 h–1) on the concentration of chlorophyll a (Chl, μg L–1) and the water temperature (T) was examined for lakes (37°29′–80°36′ N) and marine polar waters (69°16′–80°36′ N). It was shown that ~76% of the V variations was related to changes in Chl and T.  相似文献   

7.
《Developmental biology》1987,119(1):210-216
Recently, it has been demonstrated that mouse sperm contain a protein with properties similar to the inhibitory guanine nucleotide-binding regulatory protein, Gi (Kopf, G. S., Woolkalis, M. J., and Gerton, G. L. 1986. J. Biol. Chem., 261, 7327–7331). Since sperm-zona pellucida interaction represents a specialized form of intercellular communication and signal transduction we examined the role of the mouse sperm Gi-like protein in the zona pellucida-induced acrosome reaction using mechanically isolated, structurally intact zonae pellucidae. Sperm capacitated for 90 min in the presence of increasing concentrations of islet-activating protein (IAP) bind to the zona pellucida to a similar extent as control sperm incubated in the absence of this toxin. The zona pellucida-induced acrosome reaction, however, is inhibited in a concentration dependent manner by IAP, with half-maximal effects at 0.1-1.0 ng/ml IAP. IAP does not affect the ability of the sperm to become capacitated, but inhibits the cells from progressing into an intermediate stage prior to the completion of the acrosome reaction. When sperm are capacitated in the presence of 100 μM guanosine-5′-O-(3-thiotriphosphate) for 60 min prior to the addition of IAP during the final 30 min, the IAP-induced inhibition of the zona pellucida-induced acrosome reaction is abolished; capacitation in the presence of 100 μM guanosine-5′-O-(2-thiodiphosphate) does not abolish the inhibitory effects of IAP. The target of the IAP effect on intact sperm appears to be at the level of the Gi-like protein since IAP-catalyzed 32P-ADP-ribosylation of the Mr = 41,000 substrate in detergent extracts of sperm is reduced when intact sperm are preincubated with IAP during capacitation. These data suggest that the mouse sperm Gi-like protein plays an intermediary role in the zona pellucida-induced acrosome reaction.  相似文献   

8.
9.
To determine the combined effects of temperature and minimal change in food size on small-sized cladocerans, we fed Moina micrura with unicells and small colonies of Scenedesmus obliquus at different temperatures (20, 25, and 30 °C) and evaluated the parameters related to development and reproduction. Results showed that development to maturity was not affected by food sizes but significantly promoted by increasing temperature. The number of broods and total offspring significantly increased at 30 °C when M. micrura fed on unicellular S. obliquus but was not significantly different among the three temperatures when fed on colonial S. obliquus, i.e. only at 30 °C, the reproductive performance of M. micrura fed on unicellular S. obliquus was significantly higher than those fed on colonial S. obliquus, indicating that the effect of food size on the reproductive performances of M. micrura is dependent on temperature.  相似文献   

10.
Apurinic/apyrimidinic (AP) endonucleases are key enzymes involved in the repair of abasic sites and DNA strand breaks. Pathogenic bacteria Mycobacterium tuberculosis contains two AP endonucleases: MtbXthA and MtbNfo members of the exonuclease III and endonuclease IV families, which are exemplified by Escherichia coli Xth and Nfo, respectively. It has been shown that both MtbXthA and MtbNfo contain AP endonuclease and 3′  5′ exonuclease activities. However, it remains unclear whether these enzymes hold 3′-repair phosphodiesterase and nucleotide incision repair (NIR) activities. Here, we report that both mycobacterial enzymes have 3′-repair phosphodiesterase and 3′-phosphatase, and MtbNfo contains in addition a very weak NIR activity. Interestingly, depending on pH, both enzymes require different concentrations of divalent cations: 0.5 mM MnCl2 at pH 7.6 and 10 mM at pH 6.5. MtbXthA requires a low ionic strength and 37°C, while MtbNfo requires high ionic strength (200 mM KCl) and has a temperature optimum at 60 °C. Point mutation analysis showed that D180 and N182 in MtbXthA and H206 and E129 in MtbNfo are critical for enzymes activities. The steady-state kinetic parameters indicate that MtbXthA removes 3′-blocking sugar-phosphate and 3′-phosphate moieties at DNA strand breaks with an extremely high efficiency (kcat/KM = 440 and 1280  μM-1∙min−1, respectively), while MtbNfo exhibits much lower 3′-repair activities (kcat/KM = 0.26 and 0.65 μM-1∙min−1, respectively). Surprisingly, both MtbXthA and MtbNfo exhibited very weak AP site cleavage activities, with kinetic parameters 100- and 300-fold lower, respectively, as compared with the results reported previously. Expression of MtbXthA and MtbNfo reduced the sensitivity of AP endonuclease-deficient E. coli xth nfo strain to methylmethanesulfonate and H2O2 to various degrees. Taken together, these data establish the DNA substrate specificity of M. tuberculosis AP endonucleases and suggest their possible role in the repair of oxidative DNA damage generated by endogenous and host- imposed factors.  相似文献   

11.
《BBA》1986,848(3):402-410
Effects of temperature and dehydration on the efficiency of electron transfer from membrane-bound high-potential cytochromes ch to the reaction-center bacteriochlorophyll (P-890) in Ectothiorhodospira shaposhnikovii have been studied. A kinetic analysis of the cytochrome oxidation suggests that there are at least two conformational states of the ch-P-890 complex, of which only one allows photoinduced electron transfer from cytochrome to P-890+. Lowering the temperature of dehydration leads to a change in the proportion of the populations in the two conformations. The observed 2-fold deceleration of cytochrome oxidation can be related only to the diminution of the amount of photoactive cytochromes per reaction center. The rate constant for the transfer of an electron from cytochrome ch to bacteriochlorophyll is 2.8 · 105 s−1 and is independent of temperature and dehydration (as estimated within the accuracy of the experiments). The effects produced by low temperature and dehydration are completely reversible. The thermodynamic parameters of the transition of the cytochrome from the nontransfer to electron-transfer conformation were estimated. For room temperature (+ 20°C) in chromatophore preparations, ΔG = −5.4 kJ · M−1, ΔH = 60 kJ · M−1, ΔS = 0.22 kJ · M−1 · K−1. For Triton X-100 subchromatophore preparations, the absolute values of the above parameters are significantly lower: ΔG = −2.8 kJ · M−1, ΔH = 18 kJ · M−1, and ΔS = 0.075 kJ · M−1 · K−1. To a larger extent, the above parameters are diminished for chromatophore preparations in an 80% glycerol solution: ΔG = −1.7 kJ · M−1, ΔH = 6 kJ · M−1, ΔS = 0.025 kJ · M−1 · K−1. The data suggest the hydrophobic character of the forces that maintain the P-890-ch complex in the electron-transfer conformation. The results obtained suggest that electron tunneling within the complex cannot occur until a specific conformational configuration of the complex is formed. The efficiency of cytochrome ch oxidation is determined by the temperature, the degree of dehydration and the environmental conditions, whereas the transfer of an electron itself in the electron-transfer configuration is essentially independent of temperature and hydration.  相似文献   

12.
The relationships of total length (Lt) to girth at opercula (Gope) and maximum girths (Gmax) were estimated for 39 and 22 fish species, respectively, captured off the Portuguese coast between Póvoa do Varzim and Santo André (38°05′54′′–41°15′36′′N and 8°46′54′′–9°31′13′′W). The data were collected between April 1994 and September 1995. The best‐represented family was Sparidae (five species), followed by Soleidae and Triglidae (four species each). Gope and Gmax were found to increase linearly with length for all species, all r2 values being statistically significant (P < 0.01) and higher than 0.81. When Gope and Gmax were plotted against length for all species combined, three groups were identified, corresponding to general girth–length relationships: G1 = 1.408 + 0.238 ×Lt, G2 = 2.455 + 0.328 × Lt and G3 = ?0.72 + 0.60 × Lt for opercula girth and G1 = 3.402 + 0.195 × Lt, G2 = 2.211 + 0.374 × Lt and G3 = ‐2.514 + 0.717 × Lt for maximum girth. These groups correspond to different body shapes of fishes: G1‐round, G2‐torpedo‐form and G3‐compressed body.  相似文献   

13.
The operon for the Bacillus stearothermophilus SE-589 nickase-modification system (NM.BstSEI, recognition site 5′-GAGTC-3′) includes two DNA methyltransferase (M.) genes, bstSEIM1 and bstSEIM2. The gene encoding M2.BstSEI was cloned in pJW and expressed in Escherichia coli cells. M2.BstSEI was purified by chromatography and displayed maximal activity at 55° C and pH 7.5. The enzyme modified adenine in the nickase recognition site 5′-GAGTC-3′ and was specific for 5′-GASTC-3′ substrates. The kinetic parameters of the methylation reaction were determined. The catalytic constant was 2.2 min?1, and the Michaelis constant was 9.8 nM on T7 DNA and 5.8 μM on SAM.  相似文献   

14.
In this paper we establish a relation between the spread of infectious diseases and the dynamics of so called M/G/1 queues with processor sharing. The relation between the spread of epidemics and branching processes, which is well known in epidemiology, and the relation between M/G/1 queues and birth death processes, which is well known in queueing theory, will be combined to provide a framework in which results from queueing theory can be used in epidemiology and vice versa.In particular, we consider the number of infectious individuals in a standard SIR epidemic model at the moment of the first detection of the epidemic, where infectious individuals are detected at a constant per capita rate. We use a result from the literature on queueing processes to show that this number of infectious individuals is geometrically distributed.  相似文献   

15.
To find out the relative importance of the geomagnetic and solar cues for the orientation at the time of sunset, dunnocks were tested outdoors during the spring migration periods of 1982 and 1983. Experimental magnetic fields were produced by Helmholtz coils. In the various magnetic conditions, the following results were obtained:
  • 1 In the local geomagnetic field, the dunnocks oriented in a seasonally appropriate northerly direction.
  • 2 In a magnetic field the north of which was shifted 120° clock-wise to ESE, the birds showed a corresponding shift in their orientation.
  • 3 In a vertical magnetic field without meaningful directional information, birds previously tested in either the local geomagnetic field or the shifted magnetic field now displayed axially bimodal orientation, with the axes of the two groups differing.
These findings indicate that for migratory dunnocks, the magnetic field plays a dominant role in determining their orientation at the time of sunset, and that magnetic information may affect the dunnocks' response to other directional, presumably solar cues as well.  相似文献   

16.
Cytoskeletal filaments of the α-keratin type (cytokeratins) are a characteristic of epithelial cells. In diverse mammals (man, cow and rodents) these cytokeratins consist of a family of approximately 20 polypeptides, which may be divided into the more acidic (I) and the more basic (II) subfamilies. These two subfamilies show only limited amino acid sequence homology. In contrast, nucleic acid hybridization experiments and peptide maps have been interpreted to show that polypeptides of the same subfamily share extended sequence homology.We compare two polypeptides of the acidic cytokeratin subfamily, VIb (Mr 54,000) and VII (Mr 50,000), which are co-expressed in large amounts in bovine epidermal keratinocytes. These two epidermal keratins can be distinguished by specific antibodies and show different patterns of expression among several bovine tissues and cultured cells. In addition, they differ in the stability of their complexes with basic keratin polypeptides and in their tryptic peptide maps. The amino acid sequences deduced from the nucleotide sequences of complementary DNA clones containing the 3′ ends of the messenger RNAs for these keratins are compared with each other and with available amino acid sequences of human, murine and amphibian epidermal keratins. Bovine keratins VIb and VII share considerable sequence homology in the α-helical portion (68% residues identical) but lack significant homology in the extrahelical portion. Bovine keratin VIb shows, in its α-helical region, a pronounced sequence homology (88% identity) to the murine epidermal keratin of Mr 59,000. In addition, the non-helical carboxy-terminal regions of both proteins are glycinerich and contain a canonic sequence GGGSGYGG, which may be repeated several times. Moreover, their mRNAs present a highly conserved stretch of 236 nucleotides containing, in the murine sequence, the end of the coding and all of the non-coding region (81% identical nucleotides). Bovine keratin VII is considerably different from the murine Mr 59,000 keratin but is almost identical to the human cytokeratin number 14 of Mr 50,000, both in the α-helical and in the non-α-helical regions of the proteins, and the mRNAs of the human and the bovine keratins also display a high homology in their 3′ non-coding ends.The results show that in the same species keratins of the same subfamily can differ considerably, whereas equivalent keratin polypeptides of different species are readily identified by characteristic sequence homologies in the α-helical and the non-helical regions as well as in the 3′ non-coding portions of their mRNAs. Among the members of the acidic subfamily I of cytokeratin polypeptides that are co-expressed in bovine epidermis, at least two types can be distinguished by their carboxy-terminal sequences. One type is characterized by its abundance of glycine residues, a consensus GGGSGYGG heptapeptide sequence, which may be repeated several times, and an extended stretch of high RNA sequence homology in the 3′ non-coding part. The other type shows a predominance of serine and valine residues, a subterminal GGGSGYGG sequence (which has been maintained in Xenopus, cow and man) and also a high level of homology in the 3′ non-coding part of the mRNA. The data indicate that individual keratin type specificity overrides species diversity, both at the protein and the mRNA level. We discuss the evolutionary conservation and the tissue distribution of these two types of acidic keratin polypeptides as well as their possible biological functions.  相似文献   

17.
Many cetaceans are known to be acoustically active at night. However, for most dolphin species, there is little information about their nocturnal acoustic activities. To study the acoustic repertoire of Sotalia guianensis, diurnal and nocturnal sounds (whistles, burst pulses, low-frequency narrowband (LFN) sounds, and clicks) were identified in the Cananéia estuary (25° 01′ S–25° 13′ S/47° 52′ W–48° 06′ W), south of the state of São Paulo, southeastern Brazil, during April, June, and November of 2012. The emission rate of these sounds was compared between daytime and nighttime using the chi-squared statistical test. The mean values of the acoustic parameters of whistles, burst pulses, LFN sounds, and clicks were compared using the t test. Whistles, burst pulses, and LFN sounds were more frequent at night, as these individuals require greater acoustic communication in the absence of light, mainly for social communication. Echolocation emission rates were similar in both day and nighttime. Dolphin sound structure also varied throughout the day, with dolphins emitting lower-frequency sounds at night. Low-frequency sounds, with longer wavelengths, provide many advantages for dolphins active at night because such sounds propagate greater distances. This study demonstrates that the sounds produced by S. guianensis are dependent on the time of day, with social communication sounds being more influenced by the presence of light.  相似文献   

18.
Preferred direction of motion under influence of geomagnetic field and its modifications was registered in zebrafish (Danio rerio) raised in laboratory culture and in roach (Rutilus rutilus) from the Rybinsk Reservoir. In the geomagnetic field, specimens of zebrafish prefer two opposite directions oriented towards the north and south, while they prefer towards east and west at 90° turning of the horizontal component of geomagnetic field. The specimens of roach in the geomagnetic field prefer only the direction oriented towards east–northeast. This direction coincides with the direction along the canal where roach was sampled to the main river channel part of the Rybinsk Reservoir. At 90° rotation of the horizontal component of geomagnetic field, the direction turns to the south–southeast. The reasons for selection of certain directions in the geomagnetic field are discussed.  相似文献   

19.
Multipurpose NTFP species typically experience higher harvest demand because of their multiple uses, which, when combined with unsustainable land use practices, may threaten population viability. We assessed local knowledge on the uses, habitat, and population status of Mimusops andongensis and Mimusops kummel, both multipurpose NTFP species in Benin, to promote their valorization and conservation and thus sustain local knowledge on their uses for domestication issues. One hundred households were randomly selected for structured interviews for M. andongensis and 500 for M. kummel. The relationship between age, sex, and ethnic groups and the species uses was assessed using comparison and correspondence analyses. Nearly all organs of the species were used. Both species were mainly exploited for medicinal purposes but also in construction and as firewood. We found similarities in some uses of the species organs, although the species occur in different ecological zones and are used by different ethnic groups. This result should be considered for the valorization of the species. Most informants reported that populations of M. andongensis were decreasing, although some felt that they were increasing, whereas less than one-third said that M. kummel was decreasing. There were strong relationships between gender, age, and ethnic affiliation of the users and the exploited organs of both species. Potential uses exist based on both the past and current uses of the species and in comparison to other countries where they are exploited. Local ethnoecological knowledge and practices will help to valorize and conserve the species. However, further research on the species’ seed germination and propagation ability are also necessary.  相似文献   

20.
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