pH Compensation Research Articles

순환식 양액재배에서 상추의 성장에 따른 양액성분의 변화

This study was conducted to investigated the changes in the nutrient components (, , , , , and ) and environmental parameters (electrical conductivity, total dissolved solids and pH) on the leaf lettuce (Lactuca sativa L.) grown with hydroponics. Recirculating hydroponic cultivation system was consisted of planting port, LED lamp, water tank, and circulating pump for hydroponic. Nutrient solution was used in the standard solution for Japan vegetables experimental station and commercial hydroponic. The result showed that electrical conductivity (EC), total dissolved solids (TDS) and pH, depending on the growth of lettuce decreased continuously. With the growth of the lettuce, nitrate nitrogen, ammonia nitrogen, phosphate phosphorus were required for periodic replacement. The number of pH compensation due to the growth of lettuce are the most high. The concentration of and during the lettuce growth showed no significant change. However, concentration increased due to the replacement with nitrogen and phosphorus. Electric conductivity and total dissolved solids with total nutrient concentration showed the linear relationship and the correlation coefficient were 0.8601 and the 0.827, respectively.

Interactive effects of elevated CO2 and nitrogen–phosphorus supply on the physiological properties of Pyropia haitanensis (Bangiales, Rhodophyta)

The ongoing increases in atmospheric CO2 concentrations and coastal eutrophication have affected the coastal environment and marine macroalgae. In this study, the interactive effects of CO2 (390 and 1000 μL L−1) and nutrient levels (nitrogen and phosphorus supplied simultaneously) on the physiological properties of the maricultured macroalga Pyropia haitanensis (Bangiales, Rhodophyta) were investigated. The results showed that elevated CO2 significantly enhanced P. haitanensis growth and NO3 − uptake, but lowered the pH compensation points, regardless of nutrient levels, and enhanced photosynthesis and apparent photosynthetic efficiency (α) when the nutrient levels were high. However, CO2 had little effect on photosynthetic rates at low nutrient levels. At each nutrient level, CO2 elevation lowered both the phycobiliproteins (PB) and soluble protein contents, but enhanced biomass accumulation. Chlorophyll a (Chl a) and carotenoid (Car) contents were markedly increased by high CO2 concentrations at low nutrient levels. Increasing nutrient supply significantly enhanced growth, pH compensation points, and photosynthesis in P. haitanensis at each CO2 level, but the differences of the effects between intermediate and high nutrient levels on this alga were not significant for photosynthesis, pigment content, and nutrient uptake, regardless of CO2 levels. Our results suggest that the growth and physiological responses of P. haitanensis to CO2 levels are largely dependent on the supplement of nutrients. However, the interactive effects of elevated CO2 and nitrogen–phosphorus supplies on the physiological properties of P. haitanensis were limited through respective regulation by the CO2 levels in the atmosphere and the nutrient concentrations in the seawater.

Comparative research on inorganic carbon acquisition by the macroalgae Ulva prolifera (Chlorophyta) and Pyropia yezoensis (Rhodophyta)

The red macroalga Pyropia/Porphyra is one of the most important marine crops in the world; Pyropia cultivation is severely affected by the green macroalga Ulva spp., a fouling organism. In this study, growth competition and acquisition of dissolved inorganic carbon (Ci) by Ulva prolifera and Pyropia yezoensis were investigated to understand the physiological characteristics of the two species. Competition experimental results showed that the relative growth rate of U. prolifera was not affected, whereas the growth rate of P. yezoensis was significantly inhibited. U. prolifera exhibited a competitive advantage when these two species were cultured together. The two algal species displayed high pH compensation points, suggesting that U. prolifera and P. yezoensis can photosynthesize by using HCO3 −; the utilization ability of U. prolifera is stronger than that of P. yezoensis. The net photosynthetic rates of P. yezoensis and U. prolifera were significantly inhibited by the carbonic anhydrase (CA) inhibitors acetazolamide and 6-ethoxyzolamide indicating that CA is implicated in carbon-concentrating mechanisms (CCM). 4,4′-diisothiocyano-stilbene-2,2′-disulfonate (DIDS), another inhibitor that prevents direct HCO3 − uptake, did not significantly affect U. prolifera. Conversely, DIDS can sharply decrease the photosynthetic rate of P. yezoensis, particularly at high pH. U. prolifera and P. yezoensis also showed CO2-limited photosynthesis by which the half-saturating concentration of Ci exceeds that of seawater. U. prolifera did not show active HCO3 − uptake; instead, U. prolifera used HCO3 − via extracellular CA for photosynthetic carbon fixation. U. prolifera also utilizes extracellular CA-mediated HCO3 − absorption to a higher extent than P. yezoensis. By contrast, P. yezoensis shows active HCO3 − uptake and extracellular CCMs for photosynthetic carbon fixation. Therefore, these two algal species can survive in changing environments with high pH and low Ci concentration because of the action of CCMs.

High capacity for extracellular acid-base regulation in the air-breathing fish Pangasianodon hypophthalmus.

The evolution of accessory air-breathing structures is typically associated with reduction of the gills, although branchial ion transport remains pivotal for acid-base and ion regulation. Therefore, air-breathing fishes are believed to have a low capacity for extracellular pH regulation during a respiratory acidosis. In the present study, we investigated acid-base regulation during hypercapnia in the air-breathing fish Pangasianodon hypophthalmus in normoxic and hypoxic water at 28-30°C. Contrary to previous studies, we show that this air-breathing fish has a pronounced ability to regulate extracellular pH (pHe) during hypercapnia, with complete metabolic compensation of pHe within 72 h of exposure to hypoxic hypercapnia with CO2 levels above 34 mmHg. The high capacity for pHe regulation relies on a pronounced ability to increase levels of HCO3(-) in the plasma. Our study illustrates the diversity in the physiology of air-breathing fishes, such that generalizations across phylogenies may be difficult.

Physiological impacts of elevated carbon dioxide and ocean acidification on fish.

Most fish studied to date efficiently compensate for a hypercapnic acid-base disturbance; however, many recent studies examining the effects of ocean acidification on fish have documented impacts at CO2 levels predicted to occur before the end of this century. Notable impacts on neurosensory and behavioral endpoints, otolith growth, mitochondrial function, and metabolic rate demonstrate an unexpected sensitivity to current-day and near-future CO2 levels. Most explanations for these effects seem to center on increases in Pco2 and HCO3- that occur in the body during pH compensation for acid-base balance; however, few studies have measured these parameters at environmentally relevant CO2 levels or directly related them to reported negative endpoints. This compensatory response is well documented, but noted variation in dynamic regulation of acid-base transport pathways across species, exposure levels, and exposure duration suggests that multiple strategies may be utilized to cope with hypercapnia. Understanding this regulation and changes in ion gradients in extracellular and intracellular compartments during CO2 exposure could provide a basis for predicting sensitivity and explaining interspecies variation. Based on analysis of the existing literature, the present review presents a clear message that ocean acidification may cause significant effects on fish across multiple physiological systems, suggesting that pH compensation does not necessarily confer tolerance as downstream consequences and tradeoffs occur. It remains difficult to assess if acclimation responses during abrupt CO2 exposures will translate to fitness impacts over longer timescales. Nonetheless, identifying mechanisms and processes that may be subject to selective pressure could be one of many important components of assessing adaptive capacity.

Euechinoidea and Cidaroidea respond differently to ocean acidification

The impact of the chemical changes in the ocean waters due to the increasing atmospheric CO2 depends on the ability of an organism to control extracellular pH. Among sea urchins, this seems specific to the Euechinoidea, sea urchins except Cidaroidea. However, Cidaroidea survived two ocean acidification periods: the Permian–Trias and the Cretaceous–Tertiary crises. We investigated the response of these two sea urchin groups to reduced seawater pH with the tropical cidaroid Eucidaris tribuloides, the sympatric euechinoid Tripneustes ventricosus and the temperate euechinoid Paracentrotus lividus. Both euechinoid showed a compensation of the coelomic fluid pH due to increased buffer capacity. This was linked to an increased concentration of DIC in the coelomic fluid and thus of bicarbonate ions (most probably originating from the surrounding seawater as isotopic signature of the carbon – δ13C – was similar). On the other hand, the cidaroid showed no changes within the coelomic fluid. Moreover, the δ13C of the coelomic fluid did not match that of the seawater and was not significantly different between the urchins from the different treatments. Feeding rate was not affected in any species. While euechinoids are able to regulate their extracellular acid–base balance, many questions are still unanswered on the costs of this capacity. On the contrary, cidaroids do not seem affected by a reduced seawater pH. Further investigations need to be undertaken to cover more species and physiological and metabolic parameters in order to determine if energy trade-offs occur and how this mechanism of compensation is distributed among sea urchins.

Voltage-Gated Proton Channels as Novel Drug Targets: From NADPH Oxidase Regulation to Sperm Biology

Voltage-gated proton channels are increasingly implicated in cellular proton homeostasis. Proton currents were originally identified in snail neurons less than 40 years ago, and subsequently shown to play an important auxiliary role in the functioning of reactive oxygen species (ROS)-generating nicotinamide adenine dinucleotide phosphate (NADPH) oxidases. Molecular identification of voltage-gated proton channels was achieved less than 10 years ago. Interestingly, so far, only one gene coding for voltage-gated proton channels has been identified, namely hydrogen voltage-gated channel 1 (HVCN1), which codes for the HV1 proton channel protein. Over the last years, the first picture of putative physiological functions of HV1 has been emerging. The best-studied role remains charge and pH compensation during the respiratory burst of the phagocyte NADPH oxidase (NOX). Strong evidence for a role of HV1 is also emerging in sperm biology, but the relationship with the sperm NOX5 remains unclear. Probably in many instances, HV1 functions independently of NOX: for example in snail neurons, basophils, osteoclasts, and cancer cells. Generally, ion channels are good drug targets; however, this feature has so far not been exploited for HV1, and hitherto no inhibitors compatible with clinical use exist. However, there are emerging indications for HV1 inhibitors, ranging from diseases with a strong activation of the phagocyte NOX (e.g., stroke) to infertility, osteoporosis, and cancer. Clinically useful HV1-active drugs should be developed and might become interesting drugs of the future.

The effects of severe carbon limitation on the green seaweed, Ulva conglobata (Chlorophyta)

Low inorganic carbon (Ci) concentrations in seawater are usually an important factor controlling photosynthesis and growth of seaweeds. The green seaweed, Ulva conglobata Kjellm, collected from a rock pool in a middle intertidal zone located at Nanao Island, Shantou, China, were cultured under low Ci level for several days, to examine the effect of severe carbon limitation on photosynthesis. The rather high pH compensation points obtained from the pH-drift experiments indicated that U. conglobata was capable of acquiring HCO3− from surrounding seawater as its Ci source for photosynthesis. However, thalli of U. conglobata cultured in Ci-starved seawater exhibited a decline of biomass, showing that the realistic photosynthetic carbon gain could not compensate for the respiratory carbon consumption in the thalli under severe Ci limitation during laboratory culture. Compared with ambient Ci conditions, the culture under severe Ci limitation significantly had an increased pigment content, but a lower maximum quantum yield and photosynthetic electron transport rate. Additionally, the maximum carbon-saturating photosynthesis rate and the apparent photosynthetic conductance of U. conglobata thalli increased in cultures with severe Ci limitation compared with ambient Ci in low N-grown thalli. The results suggest that under severe Ci limitation, U. conglobata thalli increased capacities of both light absorption processes and carbon fixation pathways.

Enhanced production of green tide algal biomass through additional carbon supply.

Intensive algal cultivation usually requires a high flux of dissolved inorganic carbon (Ci) to support productivity, particularly for high density algal cultures. Carbon dioxide (CO2) enrichment can be used to overcome Ci limitation and enhance productivity of algae in intensive culture, however, it is unclear whether algal species with the ability to utilise bicarbonate (HCO3 −) as a carbon source for photosynthesis will benefit from CO2 enrichment. This study quantified the HCO3 − affinity of three green tide algal species, Cladophora coelothrix, Cladophora patentiramea and Chaetomorpha linum, targeted for biomass and bioenergy production. Subsequently, we quantified productivity and carbon, nitrogen and ash content in response to CO2 enrichment. All three species had similar high pH compensation points (9.7–9.9), and grew at similar rates up to pH 9, demonstrating HCO3 − utilization. Algal cultures enriched with CO2 as a carbon source had 30% more total Ci available, supplying twenty five times more CO2 than the control. This higher Ci significantly enhanced the productivity of Cladophora coelothrix (26%), Chaetomorpha linum (24%) and to a lesser extent for Cladophora patentiramea (11%), compared to controls. We demonstrated that supplying carbon as CO2 can enhance the productivity of targeted green tide algal species under intensive culture, despite their clear ability to utilise HCO3 −.

Buffer capacity of the coelomic fluid in echinoderms

The increase in atmospheric CO2 due to anthropogenic activity results in an acidification of the surface waters of the oceans. The impact of these chemical changes depends on the considered organisms. In particular, it depends on the ability of the organism to control the pH of its inner fluids. Among echinoderms, this ability seems to differ significantly according to species or taxa. In the present paper, we investigated the buffer capacity of the coelomic fluid in different echinoderm taxa as well as factors modifying this capacity. Euechinoidea (sea urchins except Cidaroidea) present a very high buffer capacity of the coelomic fluid (from 0.8 to 1.8mmolkg−1 SW above that of seawater), while Cidaroidea (other sea urchins), starfish and holothurians have a significantly lower one (from −0.1 to 0.4mmolkg−1 SW compared to seawater). We hypothesize that this is linked to the more efficient gas exchange structures present in the three last taxa, whereas Euechinoidea evolved specific buffer systems to compensate lower gas exchange abilities. The constituents of the buffer capacity and the factors influencing it were investigated in the sea urchin Paracentrotus lividus and the starfish Asterias rubens. Buffer capacity is primarily due to the bicarbonate buffer system of seawater (representing about 63% for sea urchins and 92% for starfish). It is also partly due to coelomocytes present in the coelomic fluid (around 8% for both) and, in P. lividus only, a compound of an apparent size larger than 3kDa is involved (about 15%). Feeding increased the buffer capacity in P. lividus (to a difference with seawater of about 2.3mmolkg−1 SW compared to unfed ones who showed a difference of about 0.5mmolkg−1 SW) but not in A. rubens (difference with seawater of about 0.2 for both conditions). In P. lividus, decreased seawater pH induced an increase of the buffer capacity of individuals maintained at pH7.7 to about twice that of the control individuals and, for those at pH7.4, about three times. This allowed a partial compensation of the coelomic fluid pH for individuals maintained at pH7.7 but not for those at pH7.4.

Maintenance of coelomic fluid pH in sea urchins exposed to elevated CO2: the role of body cavity epithelia and stereom dissolution

Experimental ocean acidification leads to a shift in resource allocation and to an increased [HCO3 −] within the perivisceral coelomic fluid (PCF) in the Baltic green sea urchin Strongylocentrotus droebachiensis. We investigated putative mechanisms of this pH compensation reaction by evaluating epithelial barrier function and the magnitude of skeleton (stereom) dissolution. In addition, we measured ossicle growth and skeletal stability. Ussing chamber measurements revealed that the intestine formed a barrier for HCO3 − and was selective for cation diffusion. In contrast, the peritoneal epithelium was leaky and only formed a barrier for macromolecules. The ossicles of 6 week high CO2-acclimatised sea urchins revealed minor carbonate dissolution, reduced growth but unchanged stability. On the other hand, spines dissolved more severely and were more fragile following acclimatisation to high CO2. Our results indicate that epithelia lining the PCF space contribute to its acid–base regulation. The intestine prevents HCO3 − diffusion and thus buffer leakage. In contrast, the leaky peritoneal epithelium allows buffer generation via carbonate dissolution from the surrounding skeletal ossicles. Long-term extracellular acid–base balance must be mediated by active processes, as sea urchins can maintain relatively high extracellular [HCO3 −]. The intestinal epithelia are good candidate tissues for this active net import of HCO3 − into the PCF. Spines appear to be more vulnerable to ocean acidification which might significantly impact resistance to predation pressure and thus influence fitness of this keystone species.

两种浒苔无机碳利用对温度响应的机制

PDF HTML阅读 XML下载 导出引用 引用提醒 两种浒苔无机碳利用对温度响应的机制 DOI: 10.5846/stxb201304200756 作者: 作者单位: 淮海工学院海洋学院,淮海工学院海洋学院,淮海工学院海洋学院,淮海工学院海洋学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金资助项目（41106093）；江苏省自然科学基金资助项目（BK2011400）；国家海洋局海洋公益性行业科研专项资助项目（201205010）；江苏高校优势学科建设工程资助项目 The mechnism of the characters of inorganic carbon acquisition to temperature in two Ulva species Author: Affiliation: School of Marine Science ＆ Technology,Huaihai Institute of Technology,Lianyungang,Jiangsu,China,School of Marine Science ＆ Technology,Huaihai Institute of Technology,Lianyungang,Jiangsu,China,School of Marine Science ＆ Technology,Huaihai Institute of Technology,Lianyungang,Jiangsu,China,School of Marine Science ＆ Technology,Huaihai Institute of Technology,Lianyungang,Jiangsu,China Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为了探讨温度对大型海藻无机碳利用机制的影响，选择了潮间带常见的绿藻缘管浒苔 （Ulva linza）和浒苔（Ulva prolifera）为实验材料，研究了碳酸酐酶抑制剂乙酰唑磺胺（AZ）和己氧苯并噻唑磺胺（EZ）在不同的温度下对藻体光合作用的影响。实验设置6个温度梯度（5、10、15、20、25和30℃）。结果表明，缘管浒苔和浒苔都有很强的无机碳利用能力，而温度对此有显著的影响。但他们之间存在明显的种间差异。缘管浒苔对温度的依赖性要强于浒苔，其对温度的适应范围要窄于浒苔，尤其是在高温下（30℃），缘管浒苔的最大光合作用能力与最适温度相比下降了56%，而浒苔仅为20%，这表明在高温的情况下，浒苔比缘管浒苔具有更强的生存适应能力，这是浒苔能够在绿潮藻占有绝对优势的原因之一。对缘管浒苔来说，在低温（5℃）和高温（30℃）时，无机碳的转运主要是通过胞外碳酸酐酶的催化作用，而在15℃时，加入胞外碳酸酐酶的抑制剂对无机碳的转运没有明显的影响，这表明在此温度下其他无机碳转运形式可以有效补偿胞外碳酸酐酶的作用。在其他的温度下，胞外碳酸酐酶和其他无机碳转运方式各占一定的比例。而对于浒苔来说，在低温5℃时，其他无机碳转运形式占主要作用，而从10℃开始，胞外碳酸酐酶作用比例显著增加，并且保持在相同的水平上。 Abstract:The intertidal green macroalgae Ulva linza and Ulva prolifera were selected to study the effects of carbonic anhydrase inhibitors AZ and EZ on the photosynthesis of the thalli under different temperatures. Six temperature levels were set (5, 10, 15, 20, 25 and 30℃) in the experiment. Our results showed that the values of pH compensation point of both Ulva linza and Ulva prolifera was as high as 10. This suggested that the both the two Ulva species possessed rather high ability of photosynthetic acquisition of inorganic carbon. The ability of inorganic carbon acquisition in both the two species were significantly affected by temperature, and this temperature responses were species-specific. Compared with Ulva prolifera, Ulva linza was more sensitive to temperature, suggesting that the optimum range of temperature for photosynthesis was narrower in Ulva linza than Ulva prolifera. At high temperature (30℃), the net photosynthetic rate of Ulva linza was decreased by 56%, while only by 20% in Ulva prolifera, compared with the rate at optimum temperature. These results suggested that Ulva prolifera possessed stronger ability to endure high temperature than Ulva linza did. This might be one of the most possilble physiological reasons that the dominant species in green tide bloom is Ulva prolifera. For Ulva linza, the transport of inorganic carbon was predominantly carried out by catalysis of extracellular carbonic anhydrase at temperatures of 5℃ and 30℃. However, no significant effect was found in the transport of inorganic carbon at temperature of 15℃ when the extracellular carbonic anhydrase inhibitor AZ was added. This implied that, at 15℃, another way of transport of inorganic carbon might eliminate the effect of the inhibition of extracellular carbonic anhydrase. Over the temperature rang of 20-25℃, extracellular carbonic anhydrase-mediated inorganic carbon transport and the other patterns of inorganic carbon transport operated as a fixed proportion, respectively. For Ulva prolifera, the primary pattern of the transport of inorganic carbon was not due to the catalysis of extracellular carbonic anhydrase at temperature of 5℃, and another pattern of inorganic carbon transport might operate at this temperature. However, as temperature rose to 10℃, the action of catalysis of extracellular carbonic anhydrase increased significantly, and this action maintained the same levels with further rising of temperature. 参考文献 相似文献 引证文献

Simulated climate change causes immune suppression and protein damage in the crustacean Nephrops norvegicus

Rising atmospheric carbon dioxide concentration is causing global warming, which affects oceans by elevating water temperature and reducing pH. Crustaceans have been considered tolerant to ocean acidification because of their retained capacity to calcify during subnormal pH. However, we report here that significant immune suppression of the Norway lobster, Nephrops norvegicus, occurs after a 4-month exposure to ocean acidification (OA) at a level predicted for the year 2100 (hypercapnic seawater with a pH lowered by 0.4 units). Experiments carried out at different temperatures (5, 10, 12, 14, 16, and 18°C) demonstrated that the temperature within this range alone did not affect lobster immune responses. In the OA-treatment, hemocyte numbers were reduced by almost 50% and the phagocytic capacity of the remaining hemocytes was inhibited by 60%. The reduction in hemocyte numbers was not due to increased apoptosis in hematopoetic tissue. Cellular responses to stress were investigated through evaluating advanced glycation end products (AGE) and lipid oxidation in lobster hepatopancreata, and OA-treatment was shown to significantly increase AGEs', indicating stress-induced protein alterations. Furthermore, the extracellular pH of lobster hemolymph was reduced by approximately 0.2 units in the OA-treatment group, indicating either limited pH compensation or buffering capacity. The negative effects of OA-treatment on the nephropidae immune response and tissue homeostasis were more pronounced at higher temperatures (12–18°C versus 5°C), which may potentially affect disease severity and spread. Our results signify that ocean acidification may have adverse effects on the physiology of lobsters, which previously had been overlooked in studies of basic parameters such as lobster growth or calcification.

Sour times: seawater acidification effects on growth, feeding behaviour and acid–base status of Asterias rubens and Carcinus maenas

The impact of seawater acidification on calcifying organisms varies at the species level. If the impact differs between predator and prey in strength and/or sign, trophic interactions may be altered. In the present study, we investigated the impact of 3 different seawater pCO2 levels (650, 1250 and 3500 µatm) on the acid–base status or the growth of 2 predatory species, the common sea star Asterias rubens and the shore crab Carcinus maenas, and tested whether the quantity or size of prey consumed is affected. We exposed both the predators and their prey, the blue mussel Mytilus edulis, over a time span of 10 wk and subsequently performed feeding experiments. Intermediate acidification levels had no significant effect on growth or consumption in either predator species. The highest acidification level reduced feeding and growth rates in sea stars by 56%, while in crabs a 41% decrease in consumption rates of mussels could be demonstrated over the 10 wk experimental period but not in the subsequent shorter feeding assays. Because only a few crabs moulted in the experiment, acidification effects on crab growth could not be investigated. Active extracellular pH compensation by means of bicarbonate accumulation was observed in C. maenas, whereas the coelomic fluid pH in A. rubens remained uncompensated. Acidification did not provoke a measurable shift in prey size preferred by either predator. Mussels exposed to elevated pCO2 were preferred by previously untreated A. rubens but not by C. maenas. The observed effects on species interactions were weak even at the high acidification levels expected in the future in marginal marine habitats such as the Baltic Sea. Our results indicate that when stress effects are similar (and weak) on interacting species, biotic interactions may remain unaffected.

Capacity for intracellular pH compensation during hypercapnia in white sturgeon primary liver cells

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 (20mM) ammonium prepulse. During short-term (10min) 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 19h, 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.

Acquisition of inorganic carbon by Endarachne binghamiae (Scytosiphonales, Phaeophyceae)

Photosynthetic acquisition of inorganic carbon was studied in the brown seaweed Endarachne binghamiae J. Agardh. Photosynthesis was saturated at 245 µmol photons m−2 s−1 and photoinhibition did not occur at an irradiance as high as 750 µmol photons m−2 s−1. The dependence of O2 evolution on inorganic carbon (Ci) concentration demonstrated that the normal Ci composition in natural seawater was not saturating for irradiance-saturated photosynthesis. Three lines of evidence demonstrated that E. binghamiae was able to acquire as a source of Ci for photosynthesis: (i) the high value of photosynthetic conductance for CO2 (220.6 µm s−1); (ii) the high pH compensation point of 9.7; and (iii) the measured photosynthetic rates being in excess of the theoretical maximum rates supported solely by the CO2 supply from the spontaneous dehydration of in the bulk seawater. In order to establish the mechanism of Ci acquisition, specific inhibitors and a proton buffer were applied to examine their inhibitory effects on photosynthesis. No inhibitory effects were found for the proton buffer tris(hydroxymethyl)aminomethane and the anion exchanger inhibitor, 4,4′-diisothiocyano-stilbene-2,2′-disulphonate. By contrast, photosynthetic O2 evolution in natural seawater was significantly depressed by the extracellular carbonic anhydrase (CA) activity inhibitor, acetazolamide, and the plasma membrane P-type H+-ATPase inhibitor, vanadate. These results suggested that carbon acquisition from the natural seawater was mostly through the external CA-mediated dehydration mechanism, and that P-type H+-ATPase (proton pump) in the plasma membrane simultaneously functioned in photosynthesis of E. binghamiae. Additional experiments on the O2 exchange versus pH value relationship indicated that, in contrast to photosynthesis, dark respiration of E. binghamiae was insensitive to the change of pH in the seawater, which resulted in a decreasing instantaneous balance between net carbon gain and respiratory carbon loss at high pH values in seawater.

Effects of elevated CO2 on the red seaweed Gracilaria lemaneiformis (Gigartinales, Rhodophyta) grown at different irradiance levels

Zou D. and Gao K. 2009. Effects of elevated CO2 on the red seaweed Gracilaria lemaneiformis (Gigartinales, Rhodophyta) grown at different irradiance levels. Phycologia 48: 510–517. DOI: 10.2216/08-99.1.The red seaweed Gracilaria lemaneiformis (Bory) Weber-van Bosse (Gigartinales, Rhodophyta) from Nanao Island, Shantou, China, was cultured at 370 and 700 µl l−1 CO2 in aeration and at intermediate (160 µmol photons m−2 s−1) and low (30 µmol photons m−2 s−1) irradiance levels in order to examine the influences of the elevated atmospheric CO2 concentrations on growth, photosynthetic performance and some biochemical components in this commercially important species. Relative growth rate (RGR) was significantly higher in G. lemaneiformis thalli grown using CO2-enriched air with respect to nonenriched air when the algae were subjected to intermediate irradiance. However, RGR was similar between these two CO2 treatments when the algae were grown under the low-irradiance condition. Extra CO2 in the culture decreased phycobiliprotein (PB, including phycoerythrin, PE, and phycocyanin, PC) contents of G. lemaneiformis thalli at the higher growth irradiance. However, chlorophyll a (Chl a) and soluble protein contents were unchanged by the CO2 levels in culture. Both PB and Chl a contents were higher in G. lemaneiformis thalli grown at the lower irradiance than at the higher irradiance, regardless of the CO2 levels in culture. The parameters for photosynthetic responses to irradiance and inorganic carbon were mostly not altered with the increase of CO2 concentrations in culture. However, light-saturated photosynthetic rates (Pmax) and apparent carboxylating efficiencies (ACE), expressed per unit Chl a, were significantly higher in algae grown at the intermediate irradiance compared to the low irradiance. Photosynthetic rate was reduced by an increase in pH of seawater from 8.2 to 9.1, and it was also strongly inhibited by the external carbonic anhydrase inhibitor acetazolamide (AZ) in G. lemaneiformis thalli grown at each CO2 and irradiance condition. Moreover, pH compensation points were not affected by the growth conditions. These results suggested that G. lemaneiformis under both growth conditions had a similar capacity of the photosynthetic utilization of external pool in seawater. However, ACE decreased in G. lemaneiformis thalli grown at the low irradiance with respect to the higher irradiance implied that the transport of Ci towards Rubisco within the cell was weakened. Taken together, the data showed that an increase of CO2 was less effective on G. lemaneiformis than the irradiance levels. We concluded that CO2 affected photosynthesis and growth performance when light was not the limiting factor.

Intrinsic mechanical properties of the perfused armoured catfish heart with special reference to the effects of hypercapnic acidosis on maximum cardiac performance

The armoured catfish, Pterygoplichthys pardalis, is known to be extremely tolerant of environmental hypercarbia (elevated water CO(2) tensions), which occurs in their natural environment. In addition, previous studies have demonstrated that during exposure to hypercarbia, P. pardalis does not exhibit extracellular pH compensation and thus the heart and other organs must continue to function despite a severe extracellular acidosis. We used an in situ perfused heart preparation to determine the effects of an extracellular hypercapnic (elevated CO(2) in the animal) acidosis (1-7.5% CO(2)) on heart function, specifically cardiac output, power output, heart rate and stroke volume. The present study is the first to comprehensively examine cardiac function in an acidosis-tolerant teleost. When compared with control conditions, maximum cardiac performance was unaffected at levels of CO(2) as high as 5%, far exceeding the hypercapnic tolerance of other teleosts. Moreover, P. pardalis exhibited only a moderate decrease (approximately 35%) in cardiac performance when exposed to 7.5% CO(2), and full cardiac performance was restored in six out of seven hearts upon return to control conditions. Myocardial intracellular pH (pH(i)) was protected in situ, as has been found in vivo, and this protection extended to the highest level of CO(2) (7.5%) investigated. Thus, maintained heart function during a hypercapnic acidosis in P. pardalis is probably associated with preferential pH(i) regulation of the heart, but ultimately is not sufficient to prevent loss of cardiac function. Our findings suggest the need for further study to elucidate the mechanisms behind this remarkable cardiac hypercapnic tolerance.

Complete intracellular pH protection during extracellular pH depression is associated with hypercarbia tolerance in white sturgeon,Acipenser transmontanus

Sturgeons are among the most CO2 tolerant of fishes investigated to date. However, the basis of this exceptional CO2 tolerance is unknown. Here, white sturgeon, Acipenser transmontanus, were exposed to elevated CO2 to investigate the mechanisms associated with short-term hypercarbia tolerance. During exposure to 1.5 kPa Pco2, transient blood pH [extracellular pH (pHe)] depression was compensated within 24 h and associated with net plasma HCO3- accumulation and equimolar Cl- loss, and changes in gill morphology, such as a decrease in apical surface area of mitochondrial-rich cells. These findings indicate that pHe recovery at this level of hypercarbia is accomplished in a manner similar to most freshwater teleost species studied to date, although branchial mechanisms involved may differ. White sturgeon exposed to more severe hypercarbia (3 and 6 kPa Pco2) for 48 h exhibited incomplete pH compensation in blood and red blood cells. Despite pHe depression, intracellular pH (pHi) of white muscle, heart, brain, and liver did not decrease during a transient (6 h of 1.5 kPa Pco2) or prolonged (48 h at 3 and 6 kPa Pco2 blood acidosis. This pHi protection was not due to high intrinsic buffering in tissues. Such tight active cellular regulation of pHi in the absence of pHe compensation represents a unique pattern for non-air-breathing fishes, and we hypothesize that it is the basis for the exceptional CO2 tolerance of white sturgeon and, likely, other CO2 tolerant fishes. Further research to elucidate the specific mechanisms responsible for this tremendous pH regulatory capacity in tissues of white sturgeon is warranted.

Venous Blood Gas in Holstein steers fed diets with different concentrate to lucerne hay ratios

An arterial or venous blood gas is a clinical tool for determining pulmonary and metabolic status. Arterial Blood Gas (ABG) or Venous Blood Gas (VBG) methods provide a direct measurement of partial blood pressures of carbon dioxide (PaCO2) and oxygen (PaO2), hydrogen ion activity (pH), total hemoglobin (Hbtotal), oxyhemoglobin saturation (HbO2) and bicarbonate ion concentration (HCO3-). Most blood tests are done on a sample of blood taken from a vein due to: 1-Collecting blood from an artery is more painful than collecting it from a vein because the arteries are deeper and have more nerves, 2-Artery may be inaccessible due to periarterial tissues (overlying muscle, connective tissue, or fat). In ruminants, feeding diets high in grain and other highly fermentable carbohydrates increases the risk of ruminal and blood acidosis. Although ruminal pH varies considerably within a day, cows possess a highly developed system to maintain ruminal pH within a physiological range. However, if the acid production from fermentation is more than the system can buffer, ruminal pH compensation fails and it may drop drastically (Marie Krause & Oetzel, 2005). The importance of arterial or venous blood gas measurements in the diagnosis of ruminal acidosis is prevented some health problems such as ruminal parakeratosis, erosion and ulceration of the ruminal epithelium (Garry, 2002), laminitis, sole abscesses and sole ulcer (Nocek, 1997). The objective of the present experiment was to investigate the effect of diets providing different concentrate: lucerne hay ratios on venous blood gas in Holstein steers.