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1.
The initial heat induced increase in permeability of beet (Beta vulgaris L.) root cell membranes, as measured by betacyanin efflux, is reversible. The leakage of betacyanin stopped when tissue held for 90 min at 45°C was transferred to 27°C. Stronger heat treatments, 10 min at 60°C or 150 min at 45°C, resulted in a continuous release of betacyanin indicating an irreversible change in membrane structure. Calcium ions inhibited the heat induced betacyanin efflux only if this was due to a reversible increase in permeability. 相似文献
2.
A sequential study of electrolyte leakage from roots inoculated with Phytophthora cinnamomi demonstrated changes in leakage in response to infection. These changes may be characterised in terms of susceptibility and resistance. Field resistant species showed two types of response (i) rapid leakage 2—4 h after inoculation, such as in Eucalyptus calophylla, E. maculata and Gahnia radula, (ii) no significant increase in leakage with infection, for example in cereals and in juncus bufonius. Susceptible species, such as Xanthorrhoea australis, E. sieberi and E. marginata showed slow but continually increasing leakage after inoculation, and usually lost significantly more electrolyte than field resistant species. Both electrolyte leakage and susceptibility of two Eucalyptus species varied with root temperature. Roots of both the susceptible and field resistant Eucalyptus species grown at 14°C showed similar leakage patterns to those grown at 24°C although no lesions formed at 14°C. Both amount of leakage and lesion length increased at 28°C. E. marginata (susceptible) lost significantly greater quantities of electrolyte than E. calophylla at each temperature tested. Leakage from artificially wounded roots did not vary with either temperature or with host susceptibility. No significant changes in conductivity were recorded with saprophytic colonization of roots, or with incubation in either low molecular weight culture filtrate or β-glucan solutions. Vacuum infiltration with the culture filtrate or the β-glucan slightly increased initial electrolyte loss in comparison with that of the controls. The increased leakage from infected roots may be toxin mediated or due to enzymie degradation of host plasma membranes, and occurred within the region of the limited lesion in the case of field resistant species, compared with the larger zone of extending necrosis characteristic of susceptible species. 相似文献
3.
Dana Ment Naim Iraki Galina Gindin Asael Rot Itamar Glazer Rula Abu-Jreis Michael Samish 《BioControl》2011,56(1):81-89
Temperature is one of the main obstacles for on-host applications of entomopathogenic fungi for ectoparasite control. The
effects of temperatures typical of the body surfaces of warm-blooded animals on the germination, growth and virulence of four
strains of Metarhizium anisopliae toward engorged Rhipicephalus (Boophilus) annulatus females were evaluated. The M. anisopliae strains studied can be divided according to their thermal characteristics: (1) strains which germinate (90–100%), grow and
infect ticks similarly at 25, 30 and 35°C; and (2) strains which recover their ability to germinate relatively quickly following
a thermal shock (37 or 40°C for 6–48 h) before incubation at a favorable temperature. These latter strains could recover their
infectivity after a short thermal shock (6 h at 37–40°C), but not after more prolonged exposure to these temperatures (48–72 h).
These two thermal characteristics do not interact, but reflect the efficacy of strains used to control ectoparasites on warm-blooded
vertebrates. 相似文献
4.
Tamara Pustovoitova 《Biologia Plantarum》1987,29(5):338-341
Effect of abscisic acid on cell permeability in leaves ofIresine u allisi hort. and roots ofBeta vulgaris L. were examined. An increase of betacyanin leakage from leaf cells was shown by ABA at 10−4, 10−7 or 10−9 M concentrations in water solution at 25 °C. The efflux of batacyanin from tissues did not change during the joint action
of ABA and PEG 1000. ABA could lower the betacyanin leakage fromIresine leaves and beet-root slices under severe osmotic stress, as was found by deplasmolysis. The results suggest that ABA elicits
some alteration in density of tonoplast membranes under dehydration.
Presented at the International Symposium “Plant Growth Regulators” held on June 18–22, 1984 at Liblice, Czechoslovakia. 相似文献
5.
State III respiration rates were measured in mitochondria isolated from hearts of Antarctic notothenioid fishes that differ
in the expression of hemoglobin (Hb) and myoglobin (Mb). Respiration rates were measured at temperatures between 2 and 40°C
in Gobionotothen gibberifrons (+Hb/+Mb), Chaenocephalus aceratus (–Hb/–Mb) and Chionodraco rastrospinosus (–Hb/+Mb). Blood osmolarity was measured in all three species and physiological buffers prepared for isolating mitochondria
and measuring respiration rates. Respiration rates were higher in mitochondria from G. gibberifrons compared to those from C. aceratus at 2°C, but were similar among all species at temperatures between 10 and 26°C. Respiration rates were significantly lower
in icefishes at 35 and 40°C compared to G. gibberifrons. The respiratory control ratio of isolated mitochondria was lower in C. aceratus compared to G. gibberifrons at all temperatures below 35°C. At 35 and 40°C, mitochondria were uncoupled in all species. The Arrhenius break temperature
of state III respiration was similar among all three species (30.5 ± 0.9°C) and higher than values previously reported for
Antarctic notothenioids, likely due to the higher osmolarity of buffers used in this study. These results suggest that differences
in mitochondrial structure, correlated with the expression of oxygen-binding proteins, minimally impact mitochondrial function. 相似文献
6.
Seeds stored under various conditions showed deteriorative changesin extremely dry (1% r.h. at 10 °C) or humid (93% r.h. at25 °C) conditions after 6 weeks storage, when little orno loss of viability had taken place; no changes were detectedin intermediate conditions (45% r.h. at 10 °C). The lossof electrolytes from seeds into water increased after 3 weeksof humid storage, and subsequently dead areas developed on thecotyledons of seeds held in either humid or dry conditions.With time in storage some of the seeds in dry conditions showeda reduction in the rate of imbibition, and consequently a lowlevel of electrolyte leakage. Other seeds showed an increasein leakage following dry storage. No change in solute content(sugars, potassium, and electrolytes) was detected in seedsstored in humid conditions, suggesting that the increased electrolyteleakage was caused by an impaired ability to retain solutes.Thus increased leakage was recorded in seeds whose cotyledonscontained no dead areas as revealed by vital staining, and wastherefore attributable to changes in living cells, possiblydeterioration in cell membranes. Viability began to declineafter 6 weeks in humid storage at 25 °C and after 2 d in94% r.h. at 45 °C, but was maintained in both dry and intermediateconditions. The rate at which viability fell in humid storagewas greatly influenced by the initial condition of the seed. 相似文献
7.
Among other temperature-sensitive mutants ofLactobacillus acidophilus the mutant “ts 9” with temperature-sensitive initiation of DNA synthesis was isolated. In this mutant, the course of DNA synthesis under
non-permissive conditions proceeds in two phases. During the first 90–120 min, a slight increase (20–50%) of DNA content takes
place. Then during further incubation at 40°C, the capacity for initiation of further DNA synthesis increases and a second
round of DNA synthesis starts after 3–4h of incubation. The initiation of DNA synthesis is prevented by chloramphenicol and
the preceding lag is temperature-dependent. It is concluded that an accumulation of an initiation factor is required for the
onset of a new cycle of DNA synthesis and that in thets 9 mutant this accumulation is inhibited at non-permissive temperature. 相似文献
8.
Autolytic degradation of yeast RNA occurs in many foods and beverages and can impact on the sensory quality of the product,
but the resulting complex mixture of nucleotides, nucleosides and nucleobases has not been properly characterised. In this
study, yeast autolysis was induced by incubating cell suspensions of Saccharomyces cerevisiae at 30–60 °C (pH 7.0), and at pH 4.0–7.0 (40 °C) for 10–14 days, and the RNA degradation products formed during the process
were determined by reversed-phase HPLC. Up to 95% of cell RNA was degraded, with consequent leakage into the extracellular
environment of mainly 3′-, 5′- and 2′-ribonucleotides, and lesser amounts of polynucleotides, ribonucleosides and nucleobases.
The rate of RNA degradation and the composition of the breakdown products varied with temperature and pH. RNA degradation
was fastest at 50 °C (pH 7.0). Autolysis at lower temperatures (30 °C and 40 °C) and at pH 5.0 and 6.0 favoured the formation
of 3′-nucleotides, whereas autolysis at 40 °C and 50 °C (pH 7.0) favoured 5′- and 2′-nucleotides. The best conditions for
the formation of the two flavour-enhancing nucleotides, 5′-AMP and 5′-GMP, were 50 °C (pH 7.0) and pH 4.0 (40 °C), respectively. 相似文献
9.
A new xylanase from thermoacidophilic Alicyclobacillus sp. A4 with broad-range pH activity and pH stability 总被引:1,自引:0,他引:1
Yingguo Bai Jianshe Wang Zhifang Zhang Peilong Yang Pengjun Shi Huiying Luo Kun Meng Huoqing Huang Bin Yao 《Journal of industrial microbiology & biotechnology》2010,37(2):187-194
We have identified a highly pH-adaptable and stable xylanase (XynA4) from the thermoacidophilic Alicyclobacillus sp. A4, a strain that was isolated from a hot spring in Yunnan Province, China. The gene (xynA4) that encodes this xylanase was cloned, sequenced, and expressed in Escherichia coli. It encodes a 338-residue polypeptide with a calculated molecular mass of 42.5 kDa. The deduced amino acid sequence is most
similar to (53% identity) an endo-1,4-β-xylanase from Geobacillus stearothermophilus that belongs to family 10 of the glycoside hydrolases. Purified recombinant XynA4 exhibited maximum activity at 55°C and
pH 7.0, had broad pH adaptability (>40% activity at pH 3.8–9.4) and stability (retaining >80% activity after incubation at
pH 2.6–12.0 for 1 h at 37°C), and was highly thermostable (retaining >90% activity after incubation at 60°C for 1 h at pH
7.0). These properties make XynA4 promising for application in the paper industry. This is the first report that describes
cloning and expression of a xylanase gene from the genus Alicyclobacillus. 相似文献
10.
A number of substrates were tested for the cultivation of microorganisms to produce a host of enzymes. The effect of different
substrates (wheat and rice straw, sugar cane waste, wood waste), incubation temperatures (20–40°C), initial pH levels (3.5–9.0),
incubation periods (0–72 hours) and nitrogen sources (ammonium sulfate, urea, peptone, yeast extract, sodium nitrate) on growth
and α-amylase activity was studied for the native and mutant strains. Maximum enzyme activity was observed at 1.5% wheat straw
for Aspergillus niger FCBP-198 and An-Ch-4.7 and at 2% wheat straw for An-UV-5.6, with sodium nitrate as a principle nitrogen source. The optimum
temperature for maximum enzyme activity was 30°C for the parental strain, while An-UV-5.6 and An-Ch-4.7 thrived well at 32.5°C.
The best conditions of pH and incubation duration were 4.5 and 48 hours, respectively, for all the strains. Mass production
under preoptimized growth conditions demonstrated the suitability of wheat straw for swift mycelial colonization and viability. 相似文献
11.
The expression of the Arabidopsis heat shock protein (HSP) 18.2 promoter-β-d-glucuronidase (GUS) chimera gene was investigated in transgenic Nicotiana plumbaginifolia plants during the recovery phase at normal temperatures (20–22 °C) after a heat shock (HS) treatment. GUS activity increased
during the recovery phase after HS at 42 °C for 2 h, and maximal GUS activity was observed after 12 h at normal temperatures,
at levels 50–100 times higher than the activity immediately after HS. After HS at 44 °C, little GUS activity was observed
during the first 20–24 h at normal temperatures, but the activity increased gradually thereafter, to reach a maximum at 40–50 h.
After HS at 45 °C, no GUS activity was observed throughout the experimental period. RT-PCR analysis showed that GUS mRNA
remained for 10 h after a 2-h HS at 42 °C and for 40 h after a 2-h HS at 44 °C. These findings demonstrate that brief HS
treatment, especially at a sublethal temperature, induces a long-term accumulation of HSP-GUS mRNA during the recovery phase.
Received: 31 July 1998 / Revision received: 4 November 1998 / Accepted: 19 February 1999 相似文献
12.
A thermophilic soil isolate—Bacillus sp. RS-12, grew optimally at 50°C and not below 40°C. Production of an extracellular lipase by this organism was substantially
enhanced when the type and concentration of carbon and nitrogen sources and initial pH of the culture medium were consecutively
optimized. The lipase production was found to be growth-associated with maximum secretion in the late exponential growth phase,i.e. 15h of incubation. The enzyme activity as high as 0.98 nkat/mL was obtained under optimum conditions. Tween 80 (0.5%) and
yeast extract (0.5%) were found to be the best carbon and nitrogen sources inducing maximum enzyme yield with initial pH 8.0
at 50°C. The kinetic characteristics of the crude lipase indicated the highest activity at 50–55°C and pH 8.0. It had a half
life of 60, 18 and 15 min at 65, 70 and 75°C, respectively. 相似文献
13.
M. S. T. Abbas 《BioControl》1989,34(4):447-451
Trichogramma buesi was reared in the laboratory on eggs of the Mediterranean flour moth,Anagasta kuehniella. The incubation period of the parasite's egg was 27 h at 23 °C and 22 h at 27 °C. The larval stage lasted 3.6 and 3.2 days,
the pre-pupa lasted 16 and 23 h, and the pupa lasted 5.4 and 4.6 days at 23° and 27°C, respectively. The total developmental
time (from egg to adult) averaged 9.2, 9.4, and 9.1 days when the parasite was reared on eggs ofPieris rapae, Spodoptera littoralis, andA. kuehniella, respectively, at 27 °C. Sex ratio inT. buesi was 1 ♂: 1 ♀ in nature and 1 ♂: 1.3 ♀ in the laboratory. The daily and total numbers or progeny produced/female were 5.1
and 98.2 adults, respectively. The parasite female, fed on honey, lived 10.7 days at 27 °C and 12.1 days at 23 °C.
Percentages of parasitism byT. buesi on eggs ofP. rapae collected from cabbage fields ranged between 0 and 31.5 % in 1985 and betwcen 0 and 36.4% in 1986 during July through December.
The respective figures on eggs collected from turnip fields were 16–42.2% and 12.5–32.1% during November and December.
相似文献
14.
An Arrhenius plot of the respiration rate of cucumber leavesshows a break at 12°C; below this temperature Q10 is 5.7.Leaves can survive exposure to 10°C for a week, but if chilledat 8°C for 3 d they show some loss of fresh weight and leakelectrolytes when immersed in water. At 5°C there is a markedloss of water leakage of electrolytes within a few hours. 相似文献
15.
P. V. Suresh P. K. Anil Kumar N. M. Sachindra 《World journal of microbiology & biotechnology》2011,27(6):1435-1447
Two fungal strains were evaluated for β-N-acetylhexosaminidase production by solid state fermentation using different agro-industrial residues such as commercial wheat
bran (CWB) and shrimp shell chitin waste (SSCW), of which Penicillium monoverticillium CFR 2 a local soil isolate showed significantly (P ≤ 0.001) higher β-N-acetylhexosaminidase activity on CWB medium as compared with the activity of Fusarium oxysporum CFR 8. Fermentation parameters such as incubation temperature, incubation time, initial moisture content and inoculum concentration
were optimized by statistically designed experiments, using 3**(4–1) fractional factorial design of Response Surface Methodology.
The high R2 (0.9512) observed during validation experiment showed the usefulness of the model. Highest level of enzyme activity (311.84 U/g
IDS) was predicted at 75% (w/w) initial moisture content, 26 °C incubation temperature, 168 h incubation time and initial
inoculum, at the highest concentration tested (2.95 ml spore suspension/5 g substrate). Statistical optimization yielded a
4.5 fold increase in β-N-acetylhexosaminidase activity. The crude β-N-acetylhexosaminidase showed optimum temperature of 57 ± 1 °C and pH of 3.6 and retained 50% activity after 1 h of incubation
at 57 ± 1 °C. SDS–PAGE zymogram revealed crude enzyme was a monomer with an apparent molecular weight ~110 kDa. The crude
enzyme formed 6.81 ± 0.03 mM/l of N-acetyl chitooligosaccharides from colloidal chitin in 24 h of incubation. HPLC analysis revealed hydrolysate contained 37.57%
N-acetyl chitotriose and 62.43% N-acetyl chitohexose, indicating its potential for specific N-acetyl chitooligosaccharides production. 相似文献
16.
Thermal sensitivity of mitochondrial function in the Antarctic Notothenioid Lepidonotothen nudifrons 总被引:4,自引:0,他引:4
I. Hardewig H. O. Pörtner L. S. Peck 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(8):597-604
The thermal sensitivity of mitochondrial function was investigated in the stenothermal Antarctic fish Lepidonotothen nudifrons. State 3 respiration increases with increasing temperature between 0 °C and 18 °C with a Q
10 of 2.43–2.63. State 4 respiration in the presence of oligomycin, an inhibitor of mitochondrial ATP synthase, quantifies the
leakage of protons through the inner mitochondrial membrane, which causes oxygen consumption without concomitant ATP production.
This parameter shows an unusually high Q
10 of 4.21 ± 0.42 (0–18 °C), which indicates that proton leakage does not depend merely on ion diffusion but is an enzyme-catalysed
process. The differential thermal sensitivity of oxidative phosphorylation (=state 3) and proton leakage (=state 4 in the
presence of oligomycin) leads to progressive uncoupling of the mitochondria and decreased efficiency of oxidative phosphorylation
under in vivo conditions if the body temperature of L. nudifrons increases.
Accepted: 2 September 1999 相似文献
17.
Solute Leakage in Soybean Seedlings under Various Heat Shock Regimes 总被引:11,自引:0,他引:11
The leakage of solute from intact seedlings during incubationunder various heat shock (HS) regimes was studied. ContinuousHS at 40?C did not induce leakage of amino acids, soluble sugarsand electrolytes into the incubation medium, when compared withcontrol incubation at 28?C. Continuous HS at 45?C (lethal treatment)caused leakage to increase continuously and linearly duringa 5-h treatment period. However, brief HS at 47.5?C, (lethaltreatment), unlike continuous HS at 45?C, induced leakage ata slower rate which reached a plateau within 2 to 3 h at 28?C.Preincubation for 2 h at 40?C completely prevented the leakagecaused by the brief HS at 47.5?C, but not that caused by continuous45?C HS. The amount of leakage during 2 h of incubation at 45?Cwas reduced to half by 30 min preincubation at 40?C and wasreduced to a minimal level by 1-h preincubation. Greater reductionof leakage at 45?C HS was observed when an additional 4 h ofincubation at 28?C immediately followed the 40?C preincubation.These results and previous findings (Lin et al. 1984) indicatethat the synthesis and accumulation of HS proteins (HSPs) areimportant for preventing HS-induced leakage from the cells.One of the HSPs, 15 kD in size appeared to be associated withthe plasma membrane. (Received February 12, 1985; Accepted August 30, 1985) 相似文献
18.
Sand and nest temperatures were monitored during the 2002–2003 nesting season of the green turtle, Chelonia mydas, at Heron Island, Great Barrier Reef, Australia. Sand temperatures increased from ∼ 24°C early in the season to 27–29°C in
the middle, before decreasing again. Beach orientation affected sand temperature at nest depth throughout the season; the
north facing beach remained 0.7°C warmer than the east, which was 0.9°C warmer than the south, but monitored nest temperatures
were similar across all beaches. Sand temperature at 100 cm depth was cooler than at 40 cm early in the season, but this reversed
at the end. Nest temperatures increased 2–4°C above sand temperatures during the later half of incubation due to metabolic
heating. Hatchling sex ratio inferred from nest temperature profiles indicated a strong female bias. 相似文献
19.
Bacillus subtilis 115 grew in a medium with amino acids and glucose with the maximum specific growth rates μ of 1.20-1.10/h in the temperature
range of 45–48°C. Activity of the extracellular neutral proteinase excreted by 1.3 mg/mL dry mass during 8 h of the postexponential
and stationary growth phases decreased from its maximum value of 0.23 TU/mL at 40°C to 0.13 and 0.06 TU/mL at 45 and 48°C,
respectively. Formation of the extracellular serine proteinase decreased even more—from 0.18 TU/mL at 40°C to 0.06 and 0.03
TU/mL at 45 at 48°C, respectively. Sporulation, expressed as the portion of sporangia rith refractile spores at the 6th h
of the stationary phase decreased from 46% at 40°C to 17 and 3% at 45 and 48°C, respectively. 相似文献
20.
Thachamvally Riyesh Vinayagamurthy Balamurugan Arnab Sen Veerakyathappa Bhanuprakash Gnanavel Venkatesan Vinita Yadav Raj Kumar Singh 《中国病毒学》2011,26(5):324-337
In this study, thermo-adapted (Ta) PPR vaccines were assessed for their stability at 25, 37, 40, 42 and 45°C in lyophilized
form using two extrinsic stabilizers {lactalbumin hydrolysate-sucrose (LS) and stabilizer E} and in reconstituted form with
the diluents (1 mol/L MgSO4 or 0.85% NaCl). The lyophilized vaccines showed an expiry period of 24–26 days at 25°C, 7–8 days at 37°C and 3–4 days at
40°C. LS stabilizer was superior at 42°C with a shelf-life of 44 h, whereas in stabilizer E, a 40 h shelf-life with a comparable
half-life was observed. At 45°C, the half-life in stabilizer E was better than LS and lasted for 1 day. Furthermore, the reconstituted
vaccine maintained the titre for 48 h both at 4°C and 25°C and for 24–30 h at 37°C. As both the stabilizers performed equally
well with regard to shelf-life and half-life, the present study suggests LS as stabilizer as a choice for lyophilization with
0.85% NaCl diluent, because it has better performance at higher temperature. These Ta vaccines can be used as alternatives
to existing vaccines for the control of the disease in tropical countries as they are effective in avoiding vaccination failure
due to the breakdown in cold-chain maintenance, as this vaccine is considerably more stable at ambient temperatures. 相似文献