Effect of air breathing on acid-base and ion regulation after exhaustive exercise and during low pH exposure in the bowfin, Amia calva.

To explore a potential conflict between air breathing and acid-base regulation in the bowfin (Amia calva), we examined how individuals with access to air differed from fish without air access in their response to acidosis. After exhaustive exercise, bowfin with access to air recovered significantly more slowly from the acidosis than fish without air access. While arterial blood pH (pH(a)) of fish without air access recovered to resting levels by 8 h, pH(a) was still significantly depressed in fish having access to air. In addition, Pco(2) was slightly more elevated in fish having air access than those without it. Fish with access to air still had a significant metabolic acid load after 8-h recovery, while those without air access completely cleared the load within 4 h. These results suggest that bowfin with access to air were breathing air and, consequently, were less able to excrete CO(2) and H(+) and experienced a delayed recovery. In contrast, during exposure to low pH, air breathing seemed to have a protective effect on acid-base status in bowfin. During exposure to low pH water, bowfin with access to air developed a much milder acidosis than bowfin without air access. The more severe acidosis in fish without air access was caused by an increased rate of lactic acid production. It appears that enhanced O(2) delivery allowed air-breathing bowfin to avoid acidosis-induced anaerobic metabolism and lactic acid production. In addition, during low pH exposure, plasma Na(+) and Cl(-) concentrations of fish without air access fell slightly more rapidly than those in fish with air access, indicating that the branchial ventilatory changes associated with air breathing limited, to some degree, ion losses associated with low pH exposure.     

Naphthalene-induced changes in carbohydrate metabolism in Sarotherodon mossambicus Peters (Pisces: Cichlidae)

Sarotherodon mossambicus Peters was exposed to naphthalene concentrations ranging from 7.9 to 0.92 mg/l for periods ranging from 4 days to 10 weeks and changes in glycogen, glucose, pyruvic acid and lactic acid contents of liver and muscle were studied. While glucose levels remained unaffected, major effects could be seen in the other constituents following both lethal and sublethal naphthalene treatment. Whereas glycogen and pyruvic acid levels showed considerable reduction, lactic acid levels increased markedly. These changes are indicative of a metabolic stress leading to a shift to anaerobic metabolism. The effects do not appear to be related to the feeding and growth rates of the naphthalene-intoxicated fish.     

Beta-endorphin and ACTH levels in peripheral blood during and after aerobic and anaerobic exercise

Beta-endorphin (beta-End) and adrenocorticotrophic hormone (ACTH) were determined in the peripheral blood of 14 human volunteers exercising on a bicycle ergometer. After 1 h of submaximal work below anaerobic threshold (AT), defined as the 4 mmol X l-1 lactic acid level in arteriolar blood (Kindermann 1979; Mader 1980), beta-End and ACTH levels did not change from control conditions. Eleven of the same 14 subjects performed an uninterrupted graded exercise test on the same bicycle ergometer until exhaustion. This time beta-End and ACTH levels increased concomitantly with exercise of high intensity: at each moment, during and after this maximal test, a highly significant correlation (P less than 0.0001) was noted between the levels of beta-End and ACTH. The peak values of these hormones were reached within 10 min after stopping maximal exercise, and coincided with lactic acid peak levels. A rise in lactic acid levels above the anaerobic threshold always preceded the exercise-induced rise in beta-End and ACTH. Within the population tested, two subgroups could be distinguished: one comprising individuals whose hormonal response nearly coincided with the rise in lactic acid (rapid responders) and a second group composed of subjects whose normal response appeared delayed with respect to the lactic acid rise (slow responders). These results support the view that beta-End and ACTH are secreted in equimolar quantities into the blood circulation in response to exercise, and suggest that metabolic changes of anaerobiosis play a key role in the regulation of stress-hormone release.(ABSTRACT TRUNCATED AT 250 WORDS)     

转运蛋白提高凝结芽孢杆菌酸耐受性

光学纯乳酸作为可降解生物材料——聚乳酸(polylactic acid,PLA)的前体物质,正在受到广泛关注。乳酸发酵过程中酸性产物的积累会影响菌株的生长,提高菌株酸耐受性具有重要意义。本研究以乳酸生产菌株凝结芽孢杆菌(Bacillus coagulans) DSM1为出发菌株,通过对凝结芽孢杆菌DSM1及其乳酸脱氢酶双敲除菌株(DldhL1DldhL2)进行比较转录分析,筛选酸耐受相关的转运蛋白基因。对关键基因RS16330、RS06895、RS16325、RS10595、RS00500、RS07275、RS10635及RS01930进行实时定量PCR分析,发现基因RS06895、RS10595、RS00500和RS10635在发酵12 h和24 h转录水平显著增强。过表达RS10595基因的菌株,在中性(pH 6.0)条件下生长状况和发酵性能均受到抑制,但在酸性条件下(pH 4.6),其乳酸生成相比对照组显著提高。上述结果表明,RS10595基因与菌株DSM1的酸耐受性密切相关。本研究有助于进一步探究凝结芽孢杆菌酸耐受的机制,也为构建耐酸菌株提供了基础。     

Effects of dichloroacetate on hemodynamic responses to dynamic exercise in dogs.

To determine whether lactic acid production contributes significantly to the cardiac responses to muscular dynamic exercise, we administered intravenous sodium dichloroacetate (32 mumol.kg-1.min-1), a pyruvate dehydrogenase activator that facilitates lactate metabolism via the tricarboxylic cycle, in 12 dogs during two graded levels of treadmill exercise. Similar exercise was carried out in nine normal dogs receiving equimolar doses of NaCl. In the latter group, arterial lactate increased progressively from 0.80 +/- 0.11 (SE) mmol/l at rest to 2.13 +/- 0.28 mmol/l by the end of exercise. In contrast, arterial lactate did not change significantly (0.98 +/- 0.12 to 0.95 +/- 0.11 mmol/l) during exercise in dogs receiving dichloroacetate infusion. Dichloroacetate infusion also reduced the increases in plasma norepinephrine, heart rate, and left ventricular contractile indexes that occurred during exercise, suggesting that the sympathetic cardiac stimulation occurring during exercise may be related to the production of lactic acid. However, dichloroacetate affected neither the net increase in cardiac output nor the relationship between total body oxygen consumption and cardiac output that occurred during exercise. Thus we conclude that lactic acid production is not essential to the increase in cardiac output that occurs during mild-to-moderate exercise.     

Effect of fermentation ensilaging on recovery of oil from fresh water fish viscera

Fish viscera are an important source for biomolecules such as protein and lipids. Studies were carried out to assess fermentation ensilaging as a method for recovery of oil from fresh water fish viscera. The total lipid content in the viscera ranged from 19% to 21% and upto 85% of this could be recovered by fermentation. Fermentation using added lactic cultures (Enterococcus faecium HAB01 and Pediococcus acidilactici K7) did not show any advantage over natural fermentation with respect to recovery of oil and no differences were observed in fatty acid composition of oil recovered by fermentation using different cultures. Activity of acidic, neutral and alkaline proteases decreased during fermentation. Eventhough degree of protein hydrolysis increased during fermentation with highest (62.3%) being in fermentation using Pediococcus acidilactici K7 no differences were found in oil recovery. With decrease in protease activity the rate of change in degree of hydrolysis also decreased.     

Comparative Toxicity of Three Organic Acids to Freshwater Organisms and Their Impact on Aquatic Ecosystems

The comparative toxicity of lactic acid, acetic acid, and benzoic acid to tilapia (Oreochromis mossambicus), cladoceran crustacea (Moina micrura), and oligochaete worm (Branchiura sowerbyi) were determined using static bioassay tests. Worms were found most sensitive to all the acids whereas the cladoceran was found most resistant to lactic acid and the fish most resistant to acetic acid and benzoic acid. The 96h LC₅₀ values of lactic acid, acetic acid, and benzoic acid, were, respectively, 257.73, 272.87, and 276.74 mg L^?1 for O. mossambicus; 329.12, 163.72, and 71.65 mg L^?1 for M. micrura and 50.82, 14.90, and 39.47 mg L^?1 for B. sowerbyi. Tilapia lost appetite at sub-lethal concentrations as low as 2.18 mg L^?1 lactic acid, 1.26 mg L^?1 acetic acid, and 13.84 mg L^{? 1} of benzoic acid. Growth and reproduction of the fish were affected following 90-day chronic exposure to sub-lethal concentrations of the acids. Minimum effective concentration of the acids that significantly reduced food conversion efficiency (FCE), percent increase of weight, specific growth rate, yield and fecundity of the fish were 2.18, 1.47, and 3.95 mg · L^?1 of lactic acid, acetic acid, and benzoic acid, respectively. Effects of acetic acid and benzoic acid on FCE, weight increase, and yield were not significantly different from each other whereas lactic acid produced different effects from acetic acid as well as benzoic acid. Mean values of dissolved oxygen, primary productivity, and plankton populations of the test medium significantly reduced from control at 16.94 mg L^?1 lactic acid, 16.79 mg L^?1 acetic acid, and 13.84 mg L^?1 benzoic acid.     

丁香油在鳊模拟保活运输中的效果

文章研究了丁香油对鳊(Parabramis pekinensis)保活运输的影响。在单因素试验的基础上通过正交试验确定了最佳保活运输条件。并检测和分析了在模拟运输试验中水质指标和鱼体生化指标的影响。结果显示, 最佳保活运输条件为麻醉液浓度15 mg/L、水温9℃和鱼水质量比1﹕3时, 保活时间最长达50h, 且鱼体成活率为100%。在水体指标中, pH和溶氧量无显著变化, 麻醉组氨氮在48h内由0.049增加至4.034 mg/L, 水中微生物在24h内显著增加, 氨氮的增加和微生物的生长会影响鱼体的保活。在鱼体生化指标中, 麻醉组肌肉中糖元含量24h内显著下降, 乳酸含量先升后降, pH先降再升, 说明在保活运输中糖元消耗产生乳酸; 在鱼体血液指标中, 麻醉组谷草转氨酶(AST)活性, 乳酸脱氢酶(LDH)活性, 尿素和肌酐(CREA)在12h后有所上升, 血糖(GLU)在36h内显著增加(P<0.05), 然后降低; 说明随着保活时间的延长鱼体肝脏和肾脏组织代谢水平受到一定的影响。研究表明, 在鳊麻醉保活过程中, 适当使用丁香油麻醉剂, 有助于延长其保活时间和提高存活率。     

Synergism among lactic acid, sulfite, pH and ethanol in alcoholic fermentation of Saccharomyces cerevisiae (PE-2 and M-26)

Summary The industrial production of ethanol is affected mainly by contamination by lactic acid bacteria besides others factors that act synergistically like increased sulfite content, extremely low pH, high acidity, high alcoholic content, high temperature and osmotic pressure. In this research two strains of Saccharomyces cerevisiae PE-2 and M-26 were tested regarding the alcoholic fermentation potential in highly stressed conditions. These strains were subjected to values up to 200 mg NaHSO₃ l⁻¹, 6 g lactic acid l⁻¹, 9.5% (w/v) ethanol and pH 3.6 during fermentative processes. The low pH (3.6) was the major stressing factor on yeasts during the fermentation. The M-26 strain produced higher acidity than the other, with higher production of succinic acid, an important inhibitor of lactic bacteria. Both strains of yeasts showed similar performance during the fermentation, with no significant difference in cell viability.     

秋葵籽油对高强度运动所致肝损伤的保护作用

本研究考察了秋葵籽油对高强度运动所致肝损伤的保护作用及机制。研究显示,对昆明小鼠灌胃不同剂量(10 mg/kg,20 mg/kg和50 mg/kg)的秋葵籽油4周后,秋葵籽油以剂量依赖性方式提高了小鼠的力竭游泳时间(p<0.05)。秋葵籽油降低了小鼠血清乳酸和尿素氮水平,并升高了血清游离脂肪酸和肝糖原水平(p<0.05)。秋葵籽油以剂量依赖性方式提高了小鼠肝脏组织中SOD、CAT和GSH-Px活性,并抑制了MDA的合成(p<0.05)。秋葵籽油抑制了力竭游泳诱导的小鼠血清CK、AST和ALT水平及肝脏组织NO水平的升高(p<0.05)。此外,苏木精和伊红(HE)染色证实了秋葵籽油减轻了力竭游泳诱导的肝脏病理改变。因此,本研究初步结论表明,在高强度运动过程中,秋葵籽油可通过抑制乳酸和尿素氮的积累、增加脂肪动员、降低糖原消耗、减弱氧化应激损伤等多种途径来对肝脏发挥保护作用。     

Assessment of plasma opioid peptides, beta-endorphin and met-enkephalin, at the end of an international nordic ski race

Plasma met-enkephalin, beta-endorphin, cortisol and lactic acid concentrations were measured in seventeen volunteer male subjects at rest and after a long-distance nordic ski race. Immediately after the race, mean plasma met-enkephalin did not show any significant change, but significant rises in beta-endorphin, cortisol and lactic acid were noted in all skiers. The change in beta-endorphin with exercise was significantly related to the change in cortisol (r = 0.68; p less than 0.001) and to the change in plasma lactic acid (r = 0.60; p less than 0.001). Furthermore, the experienced skiers training over 150 km X week-1 of nordic ski had significantly faster skiing times in this event and showed greater beta-endorphin, cortisol and lactic acid levels than the recreational skiers who trained for 20 km X week-1. Our results imply that the changes in plasma beta-endorphin depend on the intensity of exercise. However the significance of higher levels of skiing training or previous nordic ski experience in the release of beta-endorphin is expected and cannot be excluded.     

Comparison of methods to quantify metabolic rate and its relationship with activity in larval lake sturgeon Acipenser fulvescens

Until recently most studies have focussed on method development for metabolic rate assessment in adult and/or juvenile fish with less focus on measurement of oxygen consumption (ṀO₂) during early life history stages, including fast-growing larval fish and even less focus on nonteleostean species. In the present study we evaluated measurement techniques for standard metabolic rate (SMR), maximum metabolic rate (MMR) and aerobic scope in an Acipenseriform, the lake sturgeon Acipenser fulvescens, throughout the first year of life. Standardized forced exercise protocols to assess MMR were conducted for 5 or 15 min before or after measurement of SMR. We used different levels of oxygen decline during the measurement period of MMR post forced exercise to understand the influence these may have on the calculation of MMR. Opercular rate and tail beat frequencies were recorded by video as measures of behaviours and compared to metabolic rate recorded over a 24 h period. Results indicate that calculated values for aerobic scope were lower in younger fish. Neither exercise sequence nor exercise duration influenced metabolic rate measurements in the younger fish, but exercise duration did affect measurement of MMR in older fish. Finally, there was no strong correlation between metabolic rate and the measured behaviours in the lake sturgeon at either age. Based on the results, we recommend that a minimum of 6 h of acclimation to the respirometry chamber should be given prior to measuring SMR, a chasing protocol to elicit MMR should ideally be performed at the end of experiment, a short chasing time should be avoided to minimize variation and assessment of MMR should balance measurement limitations of the probes along with when and for how long oxygen consumption is measured.     

Acid-hydrolysis of fish wastes for lactic acid fermentation

In this study, two acid-hydrolysis processes, process A and process B, were proposed to produce low-cost nutrients for the production of lactic acid. Process A was a direct way to hydrolyze protein with diluted acid while process B was process A plus fish wastes pretreatment (an extraction by water). The two methods could both treat fish wastes to be suitable nutrient sources for promoting lactic acid production. As the pretreatment indicated some favorable effect on fish waste hydrolyzate (FWH), process B increased lactic acid productivity by 22%. Compared with 20 g/L yeast extract (YE), 6.8% FWH hydrolyzed by process B had more efficiency in lactic acid production, indicating that process B was suitable to produce high performance nutrients for lactic acid production and FWH hydrolyzed by process B would be an substitute for YE.     

Changes in metabolite levels and morphology of teleost ventricular myocytes due to hypoxia, ischaemia, and metabolic inhibitors

Since fish hearts are resistant to the effects of hypoxia, comparison of the effects of hypoxia and ischaemia on fish and mammalian hearts may lead to better understanding of ischaemic injury in mammalian hearts. The ultrastructure and levels of ATP, creatine phosphate, and lactic acid were examined in hearts obtained from largemouth bass. Bass hearts were subjected to conditions of normoxia, ischaemia, hypoxia, and hypoxia in the presence of fluoride and cyanide. ATP levels remained stable during hypoxia and ischaemia, but fell during hypoxia in the presence of fluoride or fluoride plus cyanide. Changes in creatine phosphate and lactic acid indicated ATP was produced during hypoxia and ischaemia by glycolysis, by rephosphorylation from creatine phosphate, and by oxidative phosphorylation with oxygen obtained from myoglobin or the atmosphere. Ultrastructural changes were found similar to those reported in ischaemic mammalian heart, consisting of inter- and intracellular swelling, glycogen depletion, and mitochondrial alterations. Comparison of metabolic rates between fish and mammalian hearts suggests the lower rate in fish hearts may be the chief factor which permits stable ATP levels during hypoxia and ischaemia, and thus provides resistance to these conditions.     

Enhanced production of lactic acid by an adapted strain of <Emphasis Type="Italic">Lactobacillus</Emphasis><Emphasis Type="Italic">delbrueckii</Emphasis> subsp. <Emphasis Type="Italic">lactis</Emphasis>

Lactobacillus delbrueckii subsp. lactis strains were developed having increased activity, by gradually acclimatizing the bacteria to acidic conditions over repeated batch culture. Cells from one batch culture were used as the inoculum for the subsequent batch culture and thereby an adapted strain of Lactobacillus was obtained showing improved lactic acid productivity, cell growth and total glucose utilization. Furthermore, the acclimatized cells used significantly less nitrogen for a given level of lactic acid production, which is significant from an industrial point of view. The developed procedure decreases fermentation time and nutrient use, leading to reduced operation costs, while providing a lactic acid yield superior to previously reported methods.     

Relationship between lactic acid concentration and bacterial spoilage in ground beef.

Lactic acid concentration correlated with organoleptic spoilage of refrigerated, coarsely ground beef stored in casings with low oxygen permeability. The samples were assayed over time for lactic acid concentration, total aerobic plate count, percentage of gram-positive organisms, and pH. Lactic acid increased in all samples, as did the bacterial counts and percentage of gram-positive organisms in the total microflora, the latter representing an increase in the lactic acid-producing bacteria. pH was found to decrease in all samples, with the smallest decrease in pH being observed in the meat sample which maintained the lowest proportion of gram-positive organisms. With samples evaluated by a sensory panel, lactic acid levels were found to correlate inversely with odor acceptability.     

Exercise hyperventilation in patients with McArdle's disease

This study was undertaken to determine if patients who lack muscle phosphorylase (i.e., McArdle's disease), and therefore the ability to produce lactic acid during exercise, demonstrate a normal hyperventilatory response during progressive incremental exercise. As expected these patients did not increase their blood lactate above resting levels, whereas the blood lactate levels of normal subjects increased 8- to 10-fold during maximal exercise. The venous pH of the normal subjects decreased markedly during exercise that resulted in hyperventilation. The patients demonstrated a distinct increase in ventilation with respect to O2 consumption similar to that seen in normal individuals during submaximal exercise. However their hyperventilation resulted in an increase in pH because there was no underlying metabolic acidosis. End-tidal partial pressures of O2 and CO2 also reflected a distinct hyperventilation in both groups at approximately 70-85% maximal O2 consumption. These data show that hyperventilation occurs during intense exercise, even when there is no increase in plasma [H+]. Since arterial CO2 levels were decreasing and O2 levels were increasing during the hyperventilation, it is possible that nonhumoral stimuli originating in the active muscles or in the brain elicit the hyperventilation observed during intense exercise.     

Enhanced production ofd(−)-lactic acid by mutants ofLactobacillus delbrueckii ATCC 9649

Summary Chemical mutagenesis with ethyl methanesulfonate (EMS) was used to develop strains ofLactobacillus delbrueckii (ATCC 9649) that tolerated increased lactic acid concentrations while continuously producing the acid. Three mutants (DP2, DP3 and DP4) were compared with wild-typeL. delbrueckii by standing fermentations with different glucose concentrations. All three mutants produced higher levels of lactic acid than the wild-type. In pH-controlled (pH 6.0) stirred-tank-batch fermentations, mutant DP3 in 12% glucose, 1% yeast extract/mineral salt/oleic acid medium produced lactic acid at a rate that was more than 2-times faster than the wild-type. Mutant DP3 also produced 77 g/l lactic acid compared with 58 g/l for the wild-type. Overall, compated with wild-type, the mutants DP2 and DP3 exhibited faster specific growth rates, shorter lag phases, greater lactic acid yields, tolerated higher lactic acid concentrations, and produced as much as 12% lactic acid in 12% glucose, 3% yeast extract/mineral salt/oleic acid medium which required an additional 9% glucose when the residual glucose concentration decreased to 3%. Mutant DP3 was stable for over 1.5 years (stored freeze dried). The strain development procedure was very successful; mutants with enhanced lactic acid-producing capacity were obtained each time the procedure was employed.Journal Paper No. J-14087 of the Iowa Agriculture and Home Economics Experiment Station, Ames, IA. Projects No. 2889 and 0178.     

Morphological and morphometrical changes in chloride cells of the gills of Pimephales promelas after chronic exposure to acid water

Summary Fathead minnows, Pimephales promelas, were exposed for 129 days to Lake Superior water acidified with sulfuric acid by means of a flow-through toxicant injection system. The effects of chronic acid stress (pH 6.5, 6.0, 5.5, 5.0) on gill histology were examined. Most of the histological effects were seen at pH 5.5 and 5.0 and were confined primarily to changes in numbers, distribution, and morphology of chloride cells. At low pH levels there tend to be more chloride cells in the gill epithelium and an increased percentage of these cells in the secondary lamellae. In contrast to normal chloride cells, chloride cells from fish exposed to low pH frequently had apical pits while some had bulbous apical evaginations. The occurrence of structural changes in chloride cells during exposure to acid water suggests that chloride cells may be involved in acclimation to acid stress.     

Autohydrolysed <Emphasis Type="Italic">Tilapia nilotica</Emphasis> Fish Viscera as a Peptone Source in Bacteriocin Production

Fish processing generates large amounts of solid and liquid wastes. Many different by-products have been produced from fish processing wastes. Studies on solubilization of Bolti fish (Tilapia nilotica) viscera by endogenous enzymes at different pHs are described. Hydrolysis reactions were conducted with freshly thawed viscera utilizing an initial temperature gradient and terminated at various time points by heat inactivation of the enzymes. Various peptones obtained from hydrolysed visceral homogenates of Bolti fish residues showed their suitability for promoting the growth of lactic acid bacteria (mainly Lactobacillus sake Lb 706), microorganisms with particularly complex nutritional requirements especially peptidic sources. The assay of several treatments with L. sakei Lb 706, producer of the bacteriocin sakacin A, demonstrated that optimum conditions for biomass and bacteriocin production only imply a brief autohydrolysis at room temperature. The results showed that the Bolti fish hydrolysates gave remarkable results to those found in costly commercial media, specifically recommended for culturing and large-scale production of lactic acid bacteria.