共查询到20条相似文献,搜索用时 15 毫秒
1.
Red blood cell (rbc) carbon dioxide transport was examined in vitro in three teleosts ( Oncorhynchus mykiss, Anguilla anguilla, Scophthalmus maximus) and an elasmobranch ( Scyliorhinus canicula) using a radioisotopic assay that measures the net conversion of plasma HCO 3− to CO 2. The experiments were designed to compare the intrinsic rates of rbc CO 2 excretion and the impact of haemoglobin oxygenation/deoxygenation among the species.Under conditions simulating in vivo levels of plasma HCO 3− and natural haematocrits, the rate of whole blood CO 2 excretion varied between 14.0 μmol ml −1 h −1 ( S. canicula) and 17.6 μmol ml −1 h −1 ( O. mykiss). The rate of CO 2 excretion in separated plasma was significantly greater in the dogfish, S. canicula. The contribution of the rbc to overall whole blood CO 2 excretion was low in the dogfish (46 ± 6%) compared to the teleosts (trout, 71 ± 4%; turbot, 64 ± 5%; eel, 55 ± 3%).To eliminate the naturally occurring differences in haematocrit and plasma [HCO 3−] as inter-specific variables, the rates of whole blood CO 2 excretion were determined in blood that had been resuspended to constant [HCO 3−] (5 mmol −1) and haematocrit (20%) in appropriate teleost and elasmobranch Ringer solutions. Under such normalized conditions, the rate of whole blood CO 2 excretion was significantly higher in the turbot (22.4 ± 1.3 μmol ml −1 h −1) in comparison to the other species (16.4–18.4 μmol ml −1 h −1) and thus revealed a greater intrinsic rate of rbc CO 2 excretion in the turbot.To study the contribution of Bohr protons, the rates of whole blood CO 2 excretion were assessed in blood subjected to rapid oxygenation during the initial phase of the 3 min assay period. Rapid oxygenation significantly enhanced the rate of CO 2 excretion in the teleosts but not in the elasmobranch. The extent of the increase provided by the rapid oxygenation of haemoglobin was a linear function of the extent of the Haldane effect, as quantified in each species from in vitro CO 2 dissociation (combining) curves. Under steady-state conditions, deoxygenated blood exhibited greater rates of CO 2 excretion than oxygenated blood in the teleosts but not in the elasmobranch. As a consequence of the Haldane effect, rbc intracellular pH was increased in the teleosts by deoxygenation but was unaltered in the elasmobranch.The results, by extrapolation, suggest that the rates of CO 2 excretion in vivo are influenced by the magnitude of the Haldane effect and the extent of haemoglobin oxygenation during gill transit in addition to the intrinsic rate at which the rbc converts plasma HCO 3− to CO 2. 相似文献
2.
Anthropogenic ocean acidification (OA) is a threat to coral reef fishes, but few studies have investigated responses of high-trophic-level predators, including sharks. We tested the effects of 72-hr exposure to OA-relevant elevated partial pressures of carbon dioxide (pCO2) on oxygen uptake rates, acid–base status, and haematology of newborn tropical blacktip reef sharks (Carcharhinus melanopterus). Acute exposure to end-of-century pCO2 levels resulted in elevated haematocrit (i.e. stress or compensation of oxygen uptake rates) and blood lactate concentrations (i.e. prolonged recovery) in the newborns. Conversely, whole blood and mean corpuscular haemoglobin concentrations, blood pH, estimates of standard and maximum metabolic rates, and aerobic scope remained unaffected. Taken together, newborn blacktip reef sharks appear physiologically robust to end-of-century pCO2 levels, but less so than other, previously investigated, tropical carpet sharks. Our results suggest peak fluctuating pCO2 levels in coral reef lagoons could still physiologically affect newborn reef sharks, but studies assessing the effects of long-term exposure and in combination with other anthropogenic stressors are needed. 相似文献
4.
The ability of the freshwater alga, Chlorella kessleri, to maintain a carbon concentrating mechanism when grown at acid pH was investigated. The alga grows over the pH range 4.0–9.0 and was found to take up bicarbonate and CO 2 actively when grown at pH 6.0. However, when grown at acid pH (below 5.5), it does not have active CO 2 uptake. The acidotolerant species maintained an internal pH of 6.1–7.5 over the external pH range 4.5–7.5, thus the pH difference between the cell interior and the external medium was large enough to allow for the diffusive uptake of CO 2 at acid external pH. Mass spectrometric monitoring of O 2 and CO 2 fluxes by suspensions of C. kessleri, grown at acid pH, and maintained at pH 7.5 showed that the rates of O 2 evolution did not exceed those of CO 2 uptake. The final CO 2 compensation concentrations of 14.0–17.7 µ M reached by photosynthetic cells were above the CO 2 equilibrium concentration in the external medium, indicating a lack of active CO 2 uptake at acid pH. Chlorella kessleri accumulated CO 2 with internal concentrations that were 9.9, 18.7 and 22.7‐fold that of the external medium for cells grown, respectively, at pH 4.5, 5.0 and 5.5. The ability of C. kessleri cells to accumulate high intracellular concentrations of inorganic carbon at acid pH would provide a sufficiently high concentration of CO 2 at the active site of Rubisco thus allowing the alga to maintain growth rates similar to those at alkaline pH. 相似文献
5.
In order to establish whether the blood gas respiratory disturbances noted with exposure to chloramine-T are due to differences in the rates of uptake of O 2 and excretion of CO 2 or gill blood flow, adult rainbow trout ( Oncorhynchus mykiss) were fitted with dorsal aorta and bulbus arteriosus catheters to facilitate blood pressure recordings, an ultrasonic blood flow probe and opercular impedance electrodes. Fish received either a 45-min static exposure to 9 mg l −1 chloramine-T or tap water (control) and continuous recordings of blood pressure, and ventilation frequency and amplitude were made. Pre- and post-exposure arterial and venous blood samples were taken and analyzed for O 2 and CO 2 content, hemoglobin concentration and hematocrit. Chloramine-T exposure had no effect on any of the continuously recorded parameters. However, individual measurements (made immediately prior to and following exposure) of cardiac output and O 2 uptake rates increased significantly following exposure to chloramine-T compared to before exposure. CO 2 excretion rates were unaffected by chloramine-T exposure. Calculation of the perfusion convection requirement showed a significant increase for CO 2 but not for O 2. It was concluded that increases in O 2 uptake resulted from increased cardiac output but that CO 2 excretion, a diffusion-limited process, was not increased due to additional diffusive limitations caused by the irritant effect of chloramine-T. 相似文献
6.
Abstract Addition of Na 2CO 3 to almost salt-free DNA solution (5·10 ?5M EDTA, pH=5.7, Tm=26.5 °C) elevates both pH and the DNA melting temperature (Tm) if Na 2CO 3 concentration is less than 0.004M. For 0.004M Na 2CO 3, Tm=58 °C is maximal and pH=10.56. Further increase in concentration gives rise to a monotonous decrease in Tm to 37 °C for 1M N 2CO 3 (pH=10.57). Increase in pH is also not monotonous. The highest pH=10.87 is reached at 0.04M Na 2CO 3 (Tm=48.3 °C). To reveal the cause of this DNA destabilization, which happens in a narrow pH interval (10.56÷10.87) and a wide Na 2CO 3 concentration interval (0.004÷1M), a procedure has been developed for determining the separate influences on Tm of Na +, pH, and anions formed by Na 2CO 3 (HCO 3 ? and CO 3 2-). Comparison of influence of anions formed by Na 2CO 3 on DNA stability with Cl ? (anion inert to DNA stability), ClO 4 ? (strong DNA destabilizing “chaotropic” anion) and OH ? has been carried out. It has been shown that only Na + and pH influence Tm in Na 2CO 3 solution at concentrations lower than 0.001M. However, the Tm decrease with concentration for [Na 2CO 3]≥0.004M is only partly caused by high pH≈10.7. Na 2CO 3 anions also exert a strong destabilizing influence at these concentrations. For 0.1M Na 2CO 3 (pH=10.84, [Na +]=0.2M, Tm=42.7 °C), the anion destabilizing effect is higher 20 °C. For NaClO 4 (ClO 4 ? is a strong “chaotropic” anion), an equal anion effect occurs at much higher concentrations ~3M. This means that Na 2CO 3 gives rise to a much stronger anion effect than other salts. The effect is pH dependent. It decreases fivefold at neutral pH after addition of HCl to 0.1M Na 2CO 3 as well as after addition of NaOH for pH>11.2. 相似文献
7.
Ocean acidity has increased by 30% since preindustrial times due to the uptake of anthropogenic CO 2 and is projected to rise by another 120% before 2100 if CO 2 emissions continue at current rates. Ocean acidification is expected to have wide‐ranging impacts on marine life, including reduced growth and net erosion of coral reefs. Our present understanding of the impacts of ocean acidification on marine life, however, relies heavily on results from short‐term CO 2 perturbation studies. Here, we present results from the first long‐term CO 2 perturbation study on the dominant reef‐building cold‐water coral Lophelia pertusa and relate them to results from a short‐term study to compare the effect of exposure time on the coral's responses. Short‐term (1 week) high CO 2 exposure resulted in a decline of calcification by 26–29% for a pH decrease of 0.1 units and net dissolution of calcium carbonate. In contrast, L. pertusa was capable to acclimate to acidified conditions in long‐term (6 months) incubations, leading to even slightly enhanced rates of calcification. Net growth is sustained even in waters sub‐saturated with respect to aragonite. Acclimation to seawater acidification did not cause a measurable increase in metabolic rates. This is the first evidence of successful acclimation in a coral species to ocean acidification, emphasizing the general need for long‐term incubations in ocean acidification research. To conclude on the sensitivity of cold‐water coral reefs to future ocean acidification further ecophysiological studies are necessary which should also encompass the role of food availability and rising temperatures. 相似文献
8.
Photosynthetic (oxygen evolution) and growth (biomass increase) responses to ambient pH and inorganic carbon (Ci) supply were
determined for Porphyralinearis grown in 0.5 L glass cylinders in the laboratory, or in 40 L fibreglass outdoor tanks with running seawater. While net photosynthetic
rates were uniform at pH 6.0–8.0, dropping only at pH 8.7, growth rates were significantly affected by pH levels other than
that of seawater (c. pH 8.3). In glass cylinders, weekly growth rates averaged 76% at external pH 8.0, 13% at pH 8.7 and 26%
at pH 7.0. Photosynthetic O 2 evolution on a daily basis(i.e. total O 2 evolved during day time less total O 2 consumed during night time) was similar to the growth responses at all experimental pH levels, apparently due to high dark
respiration rates measured at acidic pH. Weekly growth rates averaged 53% in algae grown in fibreglass tanks aerated with
regular air (360 mg L -1 CO 2) and 28% in algae grown in tanks aerated with CO 2-enriched air (750 mg L -1 CO 2). The pH of the seawater medium in which P. linear is was grown increased slightly during the day and only rarely reached 9.0. The pH at the boundary layer of algae submerged
in seawater increased in response to light reaching, about pH 8.9 within minutes, or remained unchanged for algae submerged
in a CO 2-free artificial sea water medium. Photosynthesis of P. linearissaturated at Ci concentrations of seawater (K 0.5560 μM at pH 8.2) and showed low photosynthetic affinity for CO 2(K 0.5 61 μM) at pH 6.0. It is therefore concluded that P. linearisuses primarily CO 2 with HCO 3
- being an alternative source of Ci for photosynthesis. Its fast growth could be related to the enzyme carbonic anhydrase whose
activity was detected intra- and extracellularly.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
10.
Acidification of ocean surface waters by anthropogenic carbon dioxide (CO 2) emissions is a currently developing scenario that warrants a broadening of research foci in the study of acid–base physiology.
Recent studies working with environmentally relevant CO 2 levels, indicate that some echinoderms and molluscs reduce metabolic rates, soft tissue growth and calcification during hypercapnic
exposure. In contrast to all prior invertebrate species studied so far, growth trials with the cuttlefish Sepia officinalis found no indication of reduced growth or calcification performance during long-term exposure to 0.6 kPa CO 2. It is hypothesized that the differing sensitivities to elevated seawater pCO 2 could be explained by taxa specific differences in acid–base regulatory capacity. In this study, we examined the acid–base
regulatory ability of S. officinalis in vivo, using a specially modified cannulation technique as well as 31P NMR spectroscopy. During acute exposure to 0.6 kPa CO 2, S. officinalis rapidly increased its blood [HCO 3
−] to 10.4 mM through active ion-transport processes, and partially compensated the hypercapnia induced respiratory acidosis.
A minor decrease in intracellular pH (pH i) and stable intracellular phosphagen levels indicated efficient pH i regulation. We conclude that S. officinalis is not only an efficient acid–base regulator, but is also able to do so without disturbing metabolic equilibria in characteristic
tissues or compromising aerobic capacities. The cuttlefish did not exhibit acute intolerance to hypercapnia that has been
hypothesized for more active cephalopod species (squid). Even though blood pH (pHe) remained 0.18 pH units below control values,
arterial O 2 saturation was not compromised in S. officinalis because of the comparatively lower pH sensitivity of oxygen binding to its blood pigment. This raises questions concerning
the potentially broad range of sensitivity to changes in acid–base status amongst invertebrates, as well as to the underlying
mechanistic origins. Further studies are needed to better characterize the connection between acid–base status and animal
fitness in various marine species. 相似文献
11.
In marine elasmobranch fish the consequences for CO 2 and acid–base state of moving into low salinity water are not well described. Sub-adult Port Jackson sharks, Heterodontus portusjacksoni, occasionally enter brackish water and survive in 50% seawater (SW). The unidirectional Na efflux and content, plasma volume, glomerular filtration rate (GFR), body mass, as well as CO 2 and acid-base state in H. portusjacksoni were investigated following transfer from 100% SW to 75% SW and then to 50% SW. A rapid water influx resulted in a doubling of the plasma volume within 24 h in sharks in 75% SW and an 11% increase in body weight. Osmotic water influx was only partially offset by a doubling of the GFR. There was a ~40% decrease in plasma [Na] through a transiently elevated Na clearance and haemodilution. The result was a decrease in the inward gradient for Na + together with reductions of nearly 50% in CO 2 and buffer capacity. The sharks remained hypo-natric to 50% SW by partially conforming to the decrease in external osmotic pressure and avoided the need for active Na + uptake. The gradient for Na + efflux would by extrapolation approach zero at ~27% SW which may of itself prove a lethal internal dilution. In sharks transferred to 75% SW, a small transient hypercapnia and a later temporary metabolic alkalosis were all largely explained through anaemia promoting loss of CO 2 and buffer capacity. In sharks transferred to 50% SW the metabolic alkalosis persisted until the end of the 1-week trial. Within the erythrocytes, increased pH was consequent on the large decrease in haemoglobin content exhibited by the sharks, which caused a large reduction in intracellular buffer. In water as dilute as 50% SW there was no evidence of specific effects on the mechanisms of management of CO 2 or H + excretion but rather significant and indirect effects of the severe haemodilution.Abbreviations
a–v
arterial–venous
-
CA
carbonic anhydrase
-
C
a
CO
2
content of CO 2 in arterial blood
-
CCO
2
CO 2 content
-
51
Cr-EDTA
51chromium-ethylenediaminetetraactic acid
-
C
v
CO
2
content of CO 2 in venous blood
-
FW
freshwater
-
GFR
glomerular filtration rate
-
Hct
haematocrit
-
J
out
Na flux rate
-
MCHC
mean cell haemoglobin concentration
-
OP
osmotic pressure
-
P
a
CO
2
partial pressure of CO 2in arterial blood
-
PCO
2
partial pressure of CO 2
-
pH
a
arterial blood pH
-
pH
er
intra-erythrocyte fluid
-
pH
pl
whole blood pH
-
pH
v
venous blood pH
-
P
v
CO
2
partial pressure of CO 2in venous blood
-
SID
strong ion difference
-
SW
seawater
-
TMAO
trimethylamine-N-oxide
-
UFR
urinary flow rate
Communicated by G. Heldmaier 相似文献
12.
Acutely lethal (24 h) exposure of adult rainbow trout ( Oncorhynchus mykiss) to 4.9 mol copper·l -1 in fresh water (pH 7.9, [Ca 2+]0.8 mEq·l -1) caused a rapid decline of plasma Na + and Cl - and arterial O 2 tension, and initially a pronounced tachycardia. The internal hypoxia probably resulted from histopathologies observed in the gills of fish exposed to copper, such as cell swelling, thickening and curling of the lamellae, and haematomas. Copper cannot therefore be considered purely as an ionoregulatory toxicant during acutely lethal conditions. Mortality during exposure to copper could not simply be explained by the plasma ionic dilution, nor by the internal hypoxia, since arterial O 2 content remained relatively unchanged. Secondary to the ionoregulatory and respiratory disturbances were a number of deleterious physiological responses which included a massive haemoconcentration (haematocrit values as high as 60%) and a doubling of the mean arterial blood pressure. The time-course of these changes suggest that cardiac failure was the final cause of death. In this respect copper exposure resembles low pH exposure in freshwater trout (Milligan and Wood 1982). Copper and H + appear to be similar in both the primary site of their toxic action (the gills) and the secondary physiological consequences which result from acutely lethal exposures. Furthermore, the acute toxicity syndrome observed may be common to many metals which cause ionoregulatory and/or respiratory problems in freshwater fish.Abbreviations
C
aO 2
arterial oxygen content
- FR
water flow rate
- Hb
haemoglobin
- Hct
haematocrit
- H
m
+
net metabolic acid load
- IU
international unit
- MABP
mean arterial blood pressure
- MCHC
mean corpuscular haemoglobin content
-
MO 2
rate of oxygen consumption
-
P
aCO 2
arterial carbon dioxide tension
-
P
aO 2
arterial oxygen partial pressure
-
T
amm
total ammonia (=NH 3+NH
4
+
)
-
TCO 2
total carbon dioxide
-
TOC
total organic carbon
- %Hb–O 2
percentage of haemoglobin saturated with oxygen 相似文献
13.
Contrasting effects of soil CO 2 concentration on root respiration rates during short-term CO 2 exposure, and on plant growth during long-term CO 2 exposure, have been reported. Here we examine the effects of both short- and long-term exposure to soil CO 2 on the root respiration of intact plants and on plant growth for bean ( Phaseolus vulgaris L.) and citrus ( Citrus volkameriana Tan. & Pasq.). For rapidly growing bean plants, the growth and maintenance components of root respiration were separated to determine whether they differ in sensitivity to soil CO 2. Respiration rates of citrus roots were unaffected by the CO 2 concentration used during the respiration measurements (200 and 2000 μmol mol −1), regardless of the soil CO 2, concentration during the previous month (600 and 20 000 μmol mol −1). Bean plants were grown with their roots exposed to either a natural CO 2 diffusion gradient, or to an artificially maintained CO 2 concentration of 600 or 20 000 μmol mol −1. These treatments had no effect on shoot and root growth. Growth respiration and maintenance respiration of bean roots were also unaffected by CO 2 pretreatment and the CO 2 concentration used during the respiration measurements (200–2000 μmol mol −1). We conclude that soil CO 2 concentrations in the range likely to be encountered in natural soils do not affect root respiration in citrus or bean. 相似文献
14.
Summary Cells of Chara corallina grown under high CO 2 culture conditions were able to utilize exogenous HCO 3
– to give appreciable rates of net photosynthesis. Since these rates of photosynthesis could be detected within 10 min of being transferred from high-CO 2 to normal HCO 3
– (pH 8.2) culture conditions, it would appear that the HCO 3
–-accumulating system of Chara is not fully repressed under these high CO 2 culture conditions. The membrane potential of these cells also responded to light/dark treatments in a manner consistent with the operation of a HCO 3
– acquisition system. With prolonged exposure (2–6 days) to CPW/B, net photosynthesis continued to increase towards the expected control rate and, in parallel, the electrical responses elicited by light/dark treatments converged towards those obtained on control (CPW/B-grown) Chara cells. Charasomes were absent in CPW/CO 2-grown Chara, but redeveloped in mature cells once the culture was returned to CPW/B conditions; a minimum period of 7 days in CPW/B was required before charasomes were detected in tissue examined in the transmission electron microscope. As the above-detailed physiological and electrophysiological features were observed with both axial and whorl cells of Chara in which charasomes were completely absent, we conclude that this specialized organelle is not an essential component for photosynthetic utilization of exogenous HCO 3
– in this species.Abbreviations CPW/B
Chara pond water containing 1.0 mM NaHCO 3, pH8.2
- CPW/CO 2
Chara pond water containing dissolved CO 2, pH 5.5
- DIC
dissolved in organic carbon
- D.H.
dark-induced membrane hyperpolarization
- L.H.
light-induced membrane hyperpolarization
- TEM
transmission electron microscopy 相似文献
15.
Fish, exposed to elevated water CO 2, experience a rapid elevation in blood CO 2 (hypercapnia), resulting in acidification of both intra- and extra-cellular compartments. White sturgeon, Acipenser transmontanus, are exceptionally CO 2 tolerant and can regulate tissue intracellular pH (pH i) in the presence of a pronounced hypercapnic acidosis (preferential pH i regulation). In this study, pH i regulatory capacity of sturgeon liver cells in primary culture was examined to assess the suitability of employing this in
vitro system to understand in vivo CO 2 tolerance in sturgeon. Using the pH-sensitive fluoroprobe BCECF, real-time changes in resting pH i and rates of pH i recovery were investigated during exposure to hypercapnia (3 and 6% CO 2) in the absence and presence of additional acid loads induced by (20 mM) ammonium prepulse. During short-term (10 min) exposure
to hypercapnia (3 and 6% CO 2), sturgeon cells were acidified and no pH i compensation was observed. However, when exposure to 6% CO 2 was extended to over 19 h, the CO 2-induced intracellular acidosis was partially compensated by a pH i increase of over 0.2 pH unit despite the sustained extracellular acidosis, indicative of a capacity for preferential pH i regulation in vitro. Since this capacity in sturgeon liver is present both in vivo and in vitro, the transmembrane transporters
involved may be the same. Therefore, cell culture may be a suitable tool to identify the transporters (i.e., the cellular
mechanisms underlying in vivo CO 2 tolerance) in white sturgeon and possibly in other hypercapnia-tolerant species. 相似文献
16.
Lifelong exposure to elevated concentrations of atmospheric CO 2 may enhance carbon assimilation of trees with unlimited rooting volume and consequently may reduce requirements for photoprotective pigments. In early summer the effects of elevated [CO 2] on carboxylation and light utilization of mature Quercus pubescens trees growing under chronic [CO 2] enrichment at two CO 2 springs and control sites in Italy were examined. Net photosynthesis was enhanced by 36 to 77%. There was no evidence of photosynthetic downregulation early in the growing season when sink demand presumably was greatest. Specifically, maximum assimilation at saturating [CO 2], electron transport capacity, and Rubisco content, activity and carboxylation capacity were not significantly different in trees growing at the CO 2 springs and their respective control sites. Foliar biochemical content, leaf reflectance index of chlorophyll pigments (NDVI), and photochemical efficiency of PSII (Δ F/ Fm′) also were not significantly affected by [CO 2] enrichment except that starch content and Δ F/ Fm′ tended to be higher at one spring (42 and 15%, respectively). Contrary to expectation, prolonged elevation of [CO 2] did not reduce xanthophyll cycle pigment pools or alter mid‐day values of leaf reflectance index of xanthophyll cycle pigments (PRI), despite the enhancement of carbon assimilation. However, both these pigments and PRI were well correlated with electron transport capacity. 相似文献
17.
The proliferation of fibroblasts and myofibroblast differentiation are crucial in wound healing and wound closure. Impaired wound healing is often correlated with chronic bacterial contamination of the wound area. A new promising approach to overcome wound contamination, particularly infection with antibiotic-resistant pathogens, is the topical treatment with non-thermal “cold” atmospheric plasma (CAP). Dielectric barrier discharge (DBD) devices generate CAP containing active and reactive species, which have antibacterial effects but also may affect treated tissue/cells. Moreover, DBD treatment acidifies wound fluids and leads to an accumulation of hydrogen peroxide (H 2O 2) and nitric oxide products, such as nitrite and nitrate, in the wound. Thus, in this paper, we addressed the question of whether DBD-induced chemical changes may interfere with wound healing-relevant cell parameters such as viability, proliferation and myofibroblast differentiation of primary human fibroblasts. DBD treatment of 250 μl buffered saline (PBS) led to a treatment time-dependent acidification (pH 6.7; 300 s) and coincidently accumulation of nitrite (~300 μM), nitrate (~1 mM) and H 2O 2 (~200 μM). Fibroblast viability was reduced by single DBD treatments (60–300 s; ~77–66%) or exposure to freshly DBD-treated PBS (60–300 s; ~75–55%), accompanied by prolonged proliferation inhibition of the remaining cells. In addition, the total number of myofibroblasts was reduced, whereas in contrast, the myofibroblast frequency was significantly increased 12 days after DBD treatment or exposure to DBD-treated PBS. Control experiments mimicking DBD treatment indicate that plasma-generated H 2O 2 was mainly responsible for the decreased proliferation and differentiation, but not for DBD-induced toxicity. In conclusion, apart from antibacterial effects, DBD/CAP may mediate biological processes, for example, wound healing by accumulation of H 2O 2. Therefore, a clinical DBD treatment must be well-balanced in order to avoid possible unwanted side effects such as a delayed healing process. 相似文献
18.
Abstract A comparison of some of the methods used to determine whether aquatic plants have the ability to utilize bicarbonate ions as a source of inorganic carbon for photosynthesis has been applied to the intertidal macroalga Ascophyllum nodosum. These include: observing photosynthesis at a high pH (below the alga's CO 2 compensation point), pH compensation point determinations, comparing the photosynthetic characteristics at low pH (5.20) and at high pH (7.95), estimating the maximal rates at which CO 2 can diffuse through the unstirred layer and the rate at which CO 2 can be produced from bicarbonate dehydration in the unstirred layer. All indicated that Ascophyllum nodosum can use bicarbonate ions for photosynthesis, though some were not always consistent. Calculating the total inorganic carbon concentration from pH measurements and acidification CO 2 determinations revealed that the assumption that the alkalinity remains constant during pH drift experiments is not always valid. 相似文献
19.
The interactive effects of elevated atmospheric CO 2 and temperature on seasonal patterns of photosynthesis in Douglas fir ( Psuedotsuga menziesii (Mirb.) Franco) seedlings were examined. Seedlings were grown in sunlit chambers controlled to track either ambient (~400 p.p.m.) CO 2 or ambient +200 p.p.m. CO 2, and either ambient temperature or ambient +4 °C. Light‐saturated net photosynthetic rates were measured approximately monthly over a 21 month period. Elevated CO 2 increased net photosynthetic rates by an average of 21% across temperature treatments during both the 1996 hydrologic year, the third year of exposure, and the 1997 hydrologic year. Elevated mean annual temperature increased net photosynthetic rates by an average of 33% across CO 2 treatments during both years. Seasonal temperature changes also affected net photosynthetic rates. Across treatments, net photosynthetic rates were highest in the spring and autumn, and lowest in July, August and December–January. Seasonal increases in temperature were not correlated with increases in the relative photosynthetic response to elevated CO 2. Seasonal shifts in the photosynthetic temperature optimum reduced temperature effects on the relative response to elevated CO 2. These results suggest that the effects of elevated CO 2 on net photosynthetic rates in Douglas fir are largely independent of temperature. 相似文献
20.
In ocean ecosystems, fluctuations in seawater pH affect CO 2 fluxes, fundamentally influencing the metabolism of marine algae, especially during the early stages of macroalgal development. In this study, short-term exposure tests (minutes) and prolonged culture experiments (eight days) were performed at different pH levels to investigate the growth and photosynthetic responses of Ulva lactuca (Ulvales, Chlorophyta) germlings. Both acidified and alkalized seawater significantly depressed algal photosynthesis during short-term exposure tests. Prolonged culture in acidified or alkalized seawater also notably decreased photosynthesis rates and growth rates of U. lactuca germlings, but increased energy consumption and lipid peroxidation, indicating damage to the germlings. Our results suggested that both lowered and increased pH levels of seawater exert significant physiological stress on U. lactuca germlings. 相似文献
|