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1.
Cryoprotective and osmotic responses to cold acclimation and freezing in freeze-tolerant and freeze-intolerant earthworms 总被引:3,自引:3,他引:0
M. Holmstrup J. P. Costanzo R. E. Lee Jr 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(3):207-214
In this paper we present the results of physiological responses to winter acclimation and tissue freezing in a freeze-tolerant
Siberian earthworm, Eisenia nordenskioeldi, and two freeze-intolerant, temperate earthworm species, Lumbricus rubellus and Aporrectodea caliginosa. By analysing the physiological responses to freezing of both types we sought to identify some key factors promoting freeze
tolerance in earthworms. Winter acclimation was followed by a significant increase in osmolality of body fluids in E. nordenskioeldi, from 197 mosmol kg−1 in 10 °C-acclimated animals to 365 mosmol kg−1 in animals acclimated to 0 °C. Cold acclimation did not cause any change in body fluid osmolality in the two freeze-intolerant
species. As a response to ice formation in the body, the freeze-intolerant species produced copious amounts of slime and expulsion
of coelomic fluids, and thereby lost 10–30% of their total water content. Contrary to this, the freeze-tolerant species did
not lose water upon freezing. At temperatures down to −6.5 °C, the ice content in the freeze-tolerant E. nordenskioeldi was significantly lower than in L. rubellus. At lower temperatures there were no differences in ice content between the two species. Cold acclimated, but unfrozen, specimens
of all three species had low levels of ammonia, urea, lactate, glycerol and glucose. As a response to ice formation, glucose
levels significantly increased within the first 24 h of freezing. This was most pronounced in E. nordenskioeldi where a 153-fold increase of glucose was seen (94 mmol · l−1). In L. rubellus and A. caliginosa a 19-fold and 17-fold increase in glucose was seen. This is the first study on physiological mechanisms promoting freeze
tolerance in E. nordenskioeldi, or any other oligochaete. Our results suggest that the cryoprotective system of this species more closely resembles that
of freeze-tolerant anurans, which synthesize cryoprotectants only after tissues begin to freeze, than that of cold-hardy invertebrates
which exhibit a preparatory accumulation of cryoprotectants during seasonal exposure to low temperature.
Accepted: 10 February 1999 相似文献
2.
The fluidity of chloroplast thylakoid membranes of frost-tolerant and frost-sensitive needles of␣three- to four-year-old
Scots pine (Pinus sylvestris L.) trees, of liposomes produced from the lipids of the thylakoids of these needles, and of liposomes containing varying
amounts of light-harvesting complex (LHC) II protein was investigated by means of electron paramagnetic resonance (EPR) measurements
using spin-labelled fatty acids as probes. Broadening of the EPR-resonance signals of 16-doxyl stearic acid in chloroplast
membranes of frost-sensitive needles and changes in the amplitudes of the peaks were observed upon a decrease in temperature
from +30 °C to −10 °C, indicating a drastic loss in rotational mobility. The lipid molecules of the thylakoid membranes of
frost-tolerant needles exhibited greater mobility. Moderate frost resistance could be induced in Scots pine needles by short-day
treatment (Vogg et al., 1997, Planta, this issue), and growth of the trees under short-day illumination (9 h) resulted in
a higher mobility of the chloroplast membrane lipids than did growth under long-day conditions (16 h). The EPR spectrum of
thylakoids from frost-tolerant needles at −10 °C was typical of a spin label in highly fluid surroundings. However, an additional
peak in the low-field range appeared in the subzero temperature range for the chloroplast membranes of frost-sensitive needles,
which represents spin-label molecules in a motionally restricted surrounding. The EPR spectra of thylakoids and of liposomes
of thylakoid lipids from frost-hardy needles were identical at +30 °C and −10 °C. The corresponding spectra from frost-sensitive
plants revealed an additional peak for the thylakoids, but not for the pure liposomes. Hence, the domains with restricted
mobility could be attributed to protein-lipid interactions in the membranes. Broadening of the spectrum and the appearance
of an additional peak was observed with liposomes of pure distearoyl phosphatidyl glycerol modified to contain increasing
amounts of LHC II. These results are discussed with respect to a loss of chlorophyll and chlorophyll-binding proteins in thylakoids
of Scots pine needles under winter conditions.
Received: 3 March 1997 / Accepted: 16 July 1997 相似文献
3.
Eriksson C Frängsmyr L Danielsson Niemi L Loimaranta V Holmskov U Bergman T Leffler H Jenkinson HF Strömberg N 《Glycoconjugate journal》2007,24(2-3):131-142
Glycoprotein gp-340 aggregates bacteria in saliva as part of innate defence at mucosal surfaces. We have detected size- and
glycoforms of gp-340 between human saliva samples (n = 7) and lung gp-340 from a proteinosis patient using antibodies and lectins in Western blots and ELISA measurements. Western
blots of saliva samples, and of gp-340 purified, from the seven donors using a gp-340 specific antibody distinguished four
gp-340 size variants, designated I to IV (n = 2,2,2 and 1). While saliva gp-340 variants I to III had single bands of increasing sizes, variant IV and lung gp-340 had
double bands. Purified I to IV proteins all revealed a N-terminal sequence TGGWIP upon Edman degradation. Moreover, purified
gp-340 from the seven donors and lung gp-340 shared N-glycans, sialylated Galβ1-3GalNAc and (poly)lactosamine structures.
However, the larger size gp-340 grouping II/III (n = 4) and smaller size grouping I/IV correlated with a secretor, Se(+), and a non secretor, Se(−), dependent glycoform of
gp-340, respectively (p = 0.03). The Se(+) glycoforms contained ABH, Leb, Ley and polylactosamine structures, while the Se(−) glycoforms lacked ABH antigens but expressed Lea, Lex and lactosamine structures. By contrast, lung gp-340 completely lacked ABH, Lea/b, Lex/y or sLex structures. Gp-340 and secretor typing of saliva from additional donors (n = 29) showed gp-340 glycoforms I to IV for 6, 16, 4 and 0 donors, respectively, and 3 non-typeable donors, and verified that
gp-340 glycoforms I and II/III correlate with Se(−) and Se(+) phenotypes, respectively (p < 0.0001). The glycoforms of saliva and lung gp-340 mediated differential aggregation of Leb- (Helicobacter pylori), sialylpolylactosamine- (Streptococcus suis) or sialic acid- (Streptococcus mutans) binding bacteria. In conclusion, variant size- and glycoforms of gp-340 are expressed by different individuals and may modulate
the biological properties of gp-340 pertinent to health and disease. 相似文献
4.
H. Ramløv 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(3):224-235
The microclimate in the habitat of the New Zealand alpine weta Hemideina maori is very variable with winter temperatures down to −6 °C under the rocks where the insects are found. Subfreezing temperatures
may in winter prevail for up to 17 days but diurnal cycles of freezing and thawing are common, as is also the case in summer.
Rates of temperature change can be very high and up to −7.20 °C/h. During winter, humidity was high for extended periods ranging
from 70% to 100% relative humidity (RH). In the summer, humidity ranged from 30% RH during the day to 100% RH at night. The
supercooling point of the haemolymph was approximately −8 °C year round, caused by a heat labile substance. The supercooling
point of the haemolymph of an insect of the same genus, Hemideina femorata not regularly exposed to subfreezing temperatures, was ca. −16.5 °C. Thermal hysteresis was not detected in the haemolymph
of H. maori. Haemolymph osmolality varied from 380 mOsm (summer) to 700 mOsm (winter). Body water content was ca. 75% all year round.
Total concentrations of sodium, potassium and chloride in haemolymph varied from 170 mM (winter) to 250 mM (summer). The total
concentration of free amino acids varied from 58 mM (summer) to 263 mM (winter). This variation was mostly due to proline
which varied from ca. 15 mM (summer) to ca. 100 mM (winter). The freeze-tolerant weta H. maori is exposed to a highly variable and cold environment all year round and several properties of its haemolymph composition
can be attributed to these climatic conditions, e.g. the presence of ice-nucleating agents and an increase in the concentration
of proline during cold hardening in the autumn.
Accepted: 22 February 1999 相似文献
5.
J. P. Costanzo A. L. Allenspach R. E. Lee Jr. 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(4-5):351-359
We investigated function and ultrastructure of sciatic nerves isolated from wood frogs (Rana sylvatica) endemic to the Northwest Territories, Canada, following freezing at −2.5 °C, −5.0 °C, or −7.5 °C. All frogs frozen at −2.5 °C,
and most frogs (71%) frozen at −5.0 °C, recovered within 14 h after thawing began; however, frogs did not survive exposure
to −7.5 °C. Sciatic nerves isolated from frogs frozen at −7.5 °C were refractory to electrical stimulation, whereas those
obtained from frogs surviving exposure to −2.5 °C or −5.0 °C generally exhibited normal characteristics of compound action
potentials. Frogs responded to freezing by mobilizing hepatic glycogen reserves to synthesize the cryoprotectant glucose,
which increased 20-fold in the liver and 40-fold in the blood. Ultrastructural analyses of nerves harvested from frogs in
each treatment group revealed that freezing at −2.5 °C or −5.0 °C had little or no effect on tissue and cellular organization,
but that (lethal) exposure to −7.5 °C resulted in marked shrinkage of the axon, degeneration of mitochondria within the axoplasm,
and extensive delamination of myelin sheaths of the surrounding Schwann cells.
Accepted: 28 April 1999 相似文献
6.
P. Meier J. Zettel 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(4):297-304
In the Swiss Prealps Entomobrya nivalis hibernates in an inactive state, hidden under bark flakes on spruce. For freeze avoidance it relies on thermal hysteresis
proteins (THPs) and polyols (mainly ribitol, with small amounts arabitol and threitol). Polyols are present only during the
inactive state, THPs additionally protect during the transition phase in spring and autumn, when animals are still active
but frosts may occur. Peak values were recorded in February/March for THPs (3.5 °C hysteresis between melting and freezing
point) and for polyols (26 μg mg−1 FW; hemolymph osmolality 680 mosmol l−1). E. nivalis is able to control its hemolymph osmolality independently of body water content. Mean osmolality in summer was 350– 440 mosmol l−1, in winter it was elevated to 650 mosmol l−1, due to a synthesis mainly of ribitol. Body water content varied between 1.8 and 3.3 mg H2O mg−1 DW, depending on humidity conditions. Experiments on triggering of antifreeze synthesis showed the action of temperature
and photoperiod as cues, but there was also evidence for an endogenous rhythm. No clear correlation between antifreeze concentration
and supercooling ability could be established, suggesting that gut content or other parameters also play an inportant role.
Accepted: 18 November 1995 相似文献
7.
Cold tolerance and dehydration in Enchytraeidae from Svalbard 总被引:4,自引:1,他引:3
L. Sømme T. Birkemoe 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(4):264-269
When cooled in contact with moisture, eight species of arctic Enchytraeidae from Svalbard were killed by freezing within
minutes or hours at −3 and −5 °C; an exception was Enchytraeus kincaidi which survived for up to 2 days. When the temperature approached 0 °C the enchytraeids apparently tried to escape from the
moist soil. The supercooling capacity of the enchytraeids was relatively low, with mean supercooling points of −5 to −8 °C.
In contrast, specimens of several species were extracted from soil cores that had been frozen in their intact state at −15 °C
for up to 71 days. Compared to freezing in a moist environment, higher survival rates were obtained during cooling at freezing
temperatures in dry soil. Survival was recorded in species kept at −3 °C for up to 35 days, and in some species kept at −6 °C
for up to 17 days. Slow warming greatly increased survival rates at −6 °C . The results strongly suggest that arctic enchytraeids
avoid freezing by dehydration at subzero temperatures. In agreement with this, weight losses of up to ca. 42% of fresh weight
were recorded in Mesenchytraeus spp. and of up to 55% in Enchytraeus kincaidi at water vapour pressures above ice at −3 to −6 °C. All specimens survived dehydration under these conditions.
Accepted: 12 December 1997 相似文献
8.
Light-stress-related changes in the properties of photosystem I 总被引:1,自引:0,他引:1
Light-stress-related changes in photosystem I (PS I) were analyzed in photoautotrophic cultured cells of Marchantia polymorpha L. High light treatment (30␣h; 1300 μmol photons · m−2 · s−1) reduced the PS I-mediated electron-transport rate by more than 50% and the photochemical efficiency of photosystem II (PS
II) by about 35%. In photoinhibited cells, 76% of the PS II centers remained closed in low light, which is in agreement with
a preferential impairment of PS I. Our data indicate that excessive linear electron transport is a cause of the loss in PS
I activity. Two PS I forms could be isolated by sucrose-gradient ultracentrifugation of mildly solubilized thylakoid membranes.
After high-light treatment one of these forms, which showed a larger light-harvesting complex (LHC) I antenna and a specific
association of LHC IIb, was enriched. The effect could be suppressed by blockage of linear electron transport. It is suggested
that PS I inactivation and state transitions caused the change in PS I organisation.
Received: 19 August 1996 / Accepted: 24 October 1996 相似文献
9.
Dumlupinar R Genisel M Erdal S Korkut T Taspinar MS Taskin M 《Biological trace element research》2011,143(3):1740-1745
The present study was performed to determine the changes in inorganic element content in barley leaves of mammalian sex hormones
(MSH). Barley leaves were sprayed with 10−4, 10−6, 10−9, 10−12, 10−15 M concentrations of progesterone, β-estradiol, and androsterone at 7th day after sowing. The plants were harvested at the
end of 18 days after treatment with MSH solutions. The inorganic element concentrations were determined using wavelength dispersive
X-ray fluorescence spectroscopy technique. Although the all MSH concentrations significantly (p < 0.05) increased the concentrations of calcium, magnesium, phosphorus, sulfur, copper, manganese, aluminum, zinc, iron,
potassium, and chlorine, it decreased those of sodium concentration in barley leaves. The maximum changes in the element concentrations
were obtained at 10−9 M for plant leaves treated with progesterone, 10−6 M for plant leaves treated with β-estradiol and androsterone. The present study elucidated that MSH significantly (p < 0.05) affected the inorganic element concentrations in barley leaves. 相似文献
10.
Infiltrating detached maize (Zeamays L.) leaves with L-galactono-1,4-lactone (L-GAL) resulted in a 4-fold increase in the content of leaf ascorbate. Upon exposure to high irradiance (1000 μmol photons m−2 s−1) at 5 °C, L-GAL leaves de-epoxidized the xanthophyll-cycle pigments faster than the control leaves; the maximal ratio of de-epoxidized
xanthophyll-cycle pigments to the whole xanthophyll-cycle pool was the same in both leaf types. The elevated ascorbate content,
together with the faster violaxanthin de-epoxidation, did not affect the degree of photoinhibition and the kinetics of the
recovery from photoinhibition, assayed by monitoring the maximum quantum efficiency of photosystem II primary photochemistry
(Fv/Fm). Under the experimental conditions, the thermal energy dissipation seems to be zeaxanthin-independent since, in contrast
to the de-epoxidation, the decrease in the efficiency of excitation-energy capture by open photosystem II reaction centers (Fv′/Fm′) during the high-irradiance treatment at low temperature showed the same kinetic in both leaf types. This was also observed
for the recovery of the maximal fluorescence after stress. Furthermore, the elevated ascorbate content did not diminish the
degradation of pigments or α-tocopherol when leaves were exposed for up to 24 h to high irradiance at low temperature. Moreover,
a higher content of ascorbate appeared to increase the requirement for reduced glutathione.
Received: 20 May 1999 / Accepted: 29 October 1999 相似文献
11.
12.
Since some amino acids, polyols and sugars in cells are thought to be osmoprotectants, we expected that several amino acids
might also contribute to enhancing freeze tolerance in yeast cells. In fact, proline and charged amino acids such as glutamate,
arginine and lysine showed a marked cryoprotective activity nearly equivalent to that of glycerol or trehalose, both known
as major cryoprotectants for Saccharomyces cerevisiae. To investigate the cryoprotective effect of proline on the freezing stress of yeast, we isolated proline-analogue-resistant
mutants derived from a proline-non-utilizing strain of S. cerevisiae. When cultured in liquid minimal medium, many mutants showed a prominent increase, two- to approximately tenfold, in cell
viability compared to the parent after freezing in the medium at −20 °C for 1 week. Some of the freeze-tolerant mutants were
found to accumulate a higher amount of proline, as well as of glutamate and arginine which are involved in proline metabolism.
It was also observed that proline-non-utilizer and the freeze-tolerant mutants were able to grow against osmotic stress. These
results suggest that the increased flux in the meta-bolic pathway of specific amino acids such as proline is effective for
breeding novel freeze-tolerant yeasts.
Received: 6 November 1996 / Accepted: 7 December 1996 相似文献
13.
Supercooling points, lower lethal temperatures, and the effect of short-term exposures to low temperatures were examined
during both winter and summer in the adults of six weevil species from three different habitats on Marion Island. Upper lethal
limits and the effects of short-term exposure to high temperatures were also examined in summer-acclimatized adult individuals
of these species. Bothrometopus elongatus, B. parvulus, B. randi, Ectemnorhinus marioni, and E. similis were freeze tolerant, but had high lower lethal temperatures (−7 to −10°C). Seasonal variation in these parameters was not
pronounced. Physical conditions of the habitat appeared to have little effect on cold hardiness parameters because the Ectemnorhinus species occur in very wet habitats, whereas the Bothrometopus species inhabit drier areas. The adults of these weevil species are similar to other high southern latitude insects in that
they are freeze tolerant, but with high lower lethal temperatures. In contrast, Palirhoeus eatoni, a supra-littoral species, avoided freezing and had a mean supercooling point of −15.5 ± 0.94°C (SE) in winter and −11.8 ± 0.98°C
in summer. Survival of a constant low temperature of −8°C also increased in this species from 6 h in summer to 27 h in winter.
It is suggested that this strategy may be a consequence of the osmoregulatory requirements imposed on this species by its
supra-littoral habitat. Upper lethal temperatures (31–34°C) corresponded closely with maximum microclimate temperatures in
all of the species. This indicates that the pronounced warming, accompanied by the increased insolation that has been recorded
at Marion Island, may reduce survival of these species. These effects may be compounded as a consequence of predation by feral
house mice on the weevils.
Received: 4 February 1997 / Accepted: 3 May 1997 相似文献
14.
Castor bean (Ricinus communis L.) plants were grown for 5–7 weeks in a controlled environment at 350 μl l−1 or 700 μl l−1 CO2. Carbon assimilation, assimilate deposition, dark respiration and assimilate mobilization were measured in leaves 2, 3 and
4 (counted from the base of the plant), and a balance sheet of carbon input and export was elaborated for both CO2 concentrations. Carbon dioxide assimilation was nearly constant over the illumination period, with only a slight depression
occurring at the end of the day in mature source leaves, not in young source leaves. Assimilation was ca. 40% higher at 700 μl l−1 than at 350 μl l−1 CO2. The source leaves increased steadily in weight per unit area during the first 3 weeks, more at 700 μl l−1 than at 350 μl l−1 CO2. On top of an irreversible weight increase, there was a large gain in dry weight during the day, which was reversed during
the night. This reversible weight gain was constant over the life time of the leaf and ca. 80% higher at 700 μl l−1 than at 350 μl l−1. Most of it was due to carbohydrates. The carbon content (as a percentage) was not altered by the CO2 treatment. Respiration was 25% higher in high-CO2 plants when based on leaf area, but the same when based on dry weight. The rate of carbon export via the phloem was the same
during the daytime in plants grown at 350 μl l−1 and 700 μl l−1 CO2. During the night the low-CO2 plants had only 50% of the daytime export rate, in contrast to the high-CO2 plants which maintained the high export rate. It was concluded that the phloem loading system is saturated during the daytime
in both CO2 regimes, whereas during the night the assimilate supply is reduced in plants in the normal CO2 concentration. Two-thirds of the carbon exported from the leaves was permanently incorporated as plant dry matter in the
residual plant parts. This “assimilation efficiency” was the same for both CO2 regimes. It is speculated that under 350 μl l−1 CO2 the growing Ricinus plant operates at sink limitation during the day and at source limitation during the night.
Received: 2 February 1999 / Accepted: 19 April 1999 相似文献
15.
Two responses to elicitins are described in cultivars of radish (Raphanus sativus L.). Type I, exhibited by the cultivar Daikon, is characterised by wilting and desiccation within 24 h of elicitin application
and was previously reported as the sensitive response (S. Kamoun et al. 1993, Mol Plant-Microbe Interact 6: 15–25). At 1 μg
elicitin · g−1 FW radish tissue, symptoms appeared after 8 h, a sensitivity comparable to that shown by tobacco to β elicitins (J.-C. Pernollet
et al., 1993, Physiol Mol Plant Pathol 42: 53–67; S. Kamoun et al., 1993, Mol Plant-Microbe Interact 6: 15–25). Elicitin failed
to induce these symptoms in the cultivar White Icicle, even at 100 μg · g−1 FW of tissue. However, a different response (Type II) with symptoms resembling senescence appeared in White Icicle after
48 h and were fully developed by 72 h. The Type II response was induced at levels of elicitin above 0.3 μg · g−1 FW. Elicitin-treated Daikon leaves held at 100% relative humidity, rather than ambient (50–60%) did not wilt and by 72 h
displayed Type II symptoms. When treated Daikon leaves were removed to ambient humidity at any time during the latent period,
they developed Type I symptoms within 2 h. Although Type I symptoms were suppressed in Daikon at high humidity, there was
no indication that leaf diffusion resistance or plant water conductance were affected. Protoplasts from the cultivar Daikon
responded to elicitin by H+ uptake and K+ release, with maximal response at 300 pM. The response was eliminated by K252a or staurosporine. Daikon protoplasts also
showed transient uptake/secretion of Ca2+ on elicitin addition. Protoplasts from White Icicle gave neither of these responses. Both Daikon and White Icicle phenotypes
could be transferred to progeny of Daikon-White Icicle crosses and in the F2 generation three phenotypes, including a null,
segregated. Only those F2 plants which exhibited the Daikon phenotype produced protoplasts which responded to elicitin.
Received: 13 May 1997 / Accepted: 27 August 1997 相似文献
16.
D. G. Butler R. Zandevakili G. Y. Oudit 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(3):213-224
The vertebrate renin-angiotensin system controls cardiovascular, renal and osmoregulatory functions. Angiotensin II (ANG
II) is the most potent hormone of the RAS but in some vertebrate animals angiotensin III (Val4-ANG III) may be a hormone. We studied the effects of some angiotensins and mammalian ANG II receptor antagonists on nasal
salt gland function and arterial blood pressure in conscious white Pekin ducks. Nasal salt gland fluid secretion (NFS) was
induced by a 10 ml · kg−1 bw i.v. injection of a NaCl solution (1000 mosmol · kg−1 H2O) and maintained by a continuous i.v. infusion of the same solution at a rate of 0.97 ml · min−1. There was a positive linear correlation between nasal fluid [Na+] and osmolality, between [Na+] and [K+], and also between the rate of NFS and [Na+] and [K+]. [Asp1,Val5]-ANG II (1 nmol · kg−1 i.v.) inhibited NFS but did not change ionic concentrations. Val4-ANG III (1 or 5 nmol · kg−1) and ANG I (1-7) (20 nmol · kg−1) had no effect on NFS. [Sar1, Ile8]-ANG II (SARILE) acted as an ANG II receptor agonist and resulted in a prolonged and complete inhibition of NFS. The AT1 receptor antagonist, losartan (DuP 753) and the AT2 receptor antagonist, PD 123319 both failed to block the inhibitory effect of [Asp1, Val5]-ANG II on the nasal salt glands.
[Asp1,Val5]-ANG II (2 nmol · kg−1 i.v.) increased mean arterial blood pressure (MABP), whereas the same dose of [Asn1,Val5]-ANG II (teleost) had only 30% of the pressor potency of the avian ANG II. Neither 1 nor 5 nmol · kg−1 of Val4-ANG III i.v. nor 20 nmol · kg−1 of ANG I (1-7) had any measurable effect on MABP. SARILE blocked completely the pressor response to [Asp1,Val5]-ANG II but the AT1 antagonists losartan and CGP 48933 and the AT2 antagonist PD 123319 all failed to block the pressor response to [Asp1,Val5]-ANG II. These results have substantiated an important role of the nasal salt gland in potassium regulation and highlighted
a pharmacological dimorphism of saralasin, namely agonist and antagonist to angiotensin II-mediated inhibition of nasal salt
gland function and pressor response, respectively. Using specific nonpeptidergic angiotensin II receptor antagonists, we have
confirmed the distinct pharmacology of the avian angiotensin II receptors in a nongallinaceous species and the absence of
significant angiotensin I (1-7) and angiotensin II effects on the cardiovascular system and nasal salt gland.
Accepted: 6 November 1997 相似文献
17.
Induction of apoptosis by the mistletoe lectins: A review on the mechanisms of cytotoxicity mediated by Viscum album L. 总被引:1,自引:0,他引:1
This review focuses on the cytotoxic properties of Viscum album L. (VAL). Apart from well-established results of protein synthesis inhibition by the mistletoe lectins (MLs), namely their catalytic A chain, there is now convincing evidence that the VAL-mediated cytotoxicity is mainly due to an induction of apoptosis. Among the more than 1,000 proteins detected in VAL, the MLs and the viscotoxins (VTs) are the predominant toxic proteins. Using purified components, such as the D-galactose-specific ML I, the N-acetyl-D-galactosamine-specific ML II and ML III, crude VTs and oligosaccharides, only the MLs induced apoptosis. The in vitro studies suggest that interaction of lectin B chains with appropriate receptors on the cell surface activates distinct signalling pathways that ultimately leads to apoptosis in a large fraction of cells, while others survive, however, with a conservation of their DNA. Inhibition of protein synthesis by the A chain of the hololectin probably accelerates the B chain-induced course of events. 相似文献
18.
The effects of different growth conditions (ventilated and closed vessels, medium with 0, 15 and 30 g dm−3 sucrose) during proliferation of donor quince (Cydonia oblonga Mill.) shoots (stage I) on net photosynthetic rate and soluble sugars content were evaluated. In order to assess the influence
of these physiological parameters on morphogenesis, leaf explants harvested from donor shoots were induced to form somatic
embryos and adventitious roots under ventilated and closed Petri dishes (stage II). Natural ventilation and low sucrose contents
(0–15 g dm−3) promoted the photosynthetic rate of quince shoots whereas biomass accumulation was the highest in those shoots cultured
with 30 g dm−3 sucrose in both vessel types and 15 g dm−3 sucrose under natural ventilation. Increasing sucrose content in the medium induced greater accumulation of sucrose in leaf
tissues of donor shoots. The content of reducing sugars was higher than that of sucrose, and it appeared to be higher in shoots
cultured under natural ventilation compared to those in closed vessels. Somatic embryogenesis and root regeneration were influenced
by stage I and II treatments. A significant correlation between sucrose content in the leaves of donor shoots and the number
of somatic embryos regenerated was found, suggesting that identification of biochemical and physiological characteristics
of donor shoots associated with increased regeneration ability might be helpful for improving morphogenesis in plant tissue
culture. 相似文献
19.
Exposure of barley (Hordeum vulgare L.) leaves to strong white light (1500 μmol photons · m−2 · s−1) decreased the quantum yield of photosynthetic oxygen evolution in green light preferentially absorbed by carotenoids (Φ-510)
but not in red light exclusively absorbed by chlorophylls (Φ-650). This phenomenon was observed to be (i) rapidly induced
(within a few minutes), (ii) slowly reversible in darkness (within about 1 h), (iii) insensitive to dithiothreitol and (iv)
maximally induced by photon flux densities higher than about 1000 μmol · m−2 · s−1. Determination of the carotenoid composition of the major light-harvesting complex of PSII (LHCII) and analysis of the thylakoid
membrane lipid fluidity before and after strong illumination of barley leaves in the presence or the absence of dithiothreitol
showed that the light-induced decrease in the Φ-510/Φ-650 ratio did not require the physical detachment of carotenoids from
the pigment antennae. Compared to barley plants grown under moderate light and temperature conditions, plants grown in sustained
high irradiance at elevated temperature exhibited (i) a lower Φ-510/Φ-650 ratio, (ii) a reduced size of the functional PSII
pigment antenna in green light (but not in red light) and (iii) a marked increase in the amount of free carotenoids found
in non-denaturing Deriphat-containing electrophoretic gels of thylakoid membranes. Similarly, the Φ-510/Φ-650 ratio of the
LHCII-deficient chlorina-f2 barley mutant was very low compared to the wild type. Separation and quantification of the cis/trans carotenoid isomers of barley leaves revealed that strong illumination did not induce pronounced cis-trans isomerization of xanthophylls. Taken together, the data suggest that the efficiency of energy transfer from carotenoids to
chlorophylls varies with the light environment both in the short term and in the long term, with excess light energy noticeably
inhibiting the photosynthetic light-harvesting function of carotenoids. The photoprotective significance of this carotenoid
decoupling from the chlorophyll antennae is discussed.
Received: 28 July 1997 / Accepted: 25 October 1997 相似文献
20.
Udo Schumacher Anna Stamouli Elizabeth Adam Margaret Peddie Uwe Pfüller 《Glycoconjugate journal》1995,12(3):250-257
Cytotoxicity of the mistletoe lectins I, II and III towards six human breast cancer cell lines was assessed using the Mossman assay. In addition, binding of the three mistletoe lectins to the separated membrane glycoproteins of these cell lines, the binding and uptake of these lectins into the cells in tissue culture and the binding of the lectins to histological preparations of these cell lines were analysed. The results indicate that there are quantitative differences concerning the toxicity of these three lectins towards the different cell lines. Furthermore, the lectin binding pattern in the cell lines differed. In Western blots, several membrane glycoproteins were labelled by the lectins. Our results indicate subtle differences between the three lectins with regard to the parameters mentioned above; however, the toxicity of all three lectins from mistletoe is so similar that they all seem suitable for the construction of immunotoxins.Dedication: This work is dedicated to one of the discoverers (amongst many other important contributions) ofHelix pomatia agglutinin, which plays an important role in metastasis research, Professor Dr G. Uhlenbruck on the occasion of his 65th birthday. 相似文献