Antioxidant activity and anti-exercise-fatigue effect of highly denatured soybean meal hydrolysate prepared using neutrase

The process of solid-state fermentation of soybean meal: antimicrobial activity, fermentation heat generation and nitrogen solubility index

BACKGROUND

Bacillus amyloliquefaciens has excellent protease production ability and holds great prospects for application in the solid-state fermentation of soybean meal (SBM).

RESULTS

Among eight strains of bacteria, Bacillus amyloliquefaciens subsp. plantarum CICC 10265, which exhibited higher protease production, was selected as the fermentation strain. The protease activity secreted by this strain reached 106.41 U mL-1 . The microbial community structure differed significantly between natural fermentation and inoculation-enhanced fermented soybean meal (FSBM), with the latter showing greater stability and inhibition of miscellaneous bacterial growth. During fermentation, the temperature inside the soybean meal increased, and the optimal environmental temperature for FSBM was found to be between 35 and 40 °C. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis and nitrogen solubility index (NSI) results demonstrated that solid-state fermentation had a degrading effect on highly denatured proteins in SBM, resulting in an NSI of 67.1%.

CONCLUSION

Bacillus amyloliquefaciens subsp. plantarum CICC 10265 can enhance the NSI of SBM in solid-state fermentation and inhibit the growth of miscellaneous bacteria. © 2023 Society of Chemical Industry.

Effects of soyhulls with different particle size on the growth performance, blood indices and gut microbiota of yellow feather broilers

1. The objective of this study was to determine the effects of soyhulls with different particle sizes on the growth performance, blood indices and gut microbiota of yellow feather broilers.2. Total of 240 healthy, one-day-old, yellow feather broilers were randomly divided into four groups, with six pen replicates within each group and ten birds per pen. The control group birds were fed the basal diet (Control). For the treatment groups, 5% soyhulls with different particle sizes were included in the basal diet. The particle size geometric mean diameters (dgw) of the soyhulls in the three treatment groups were 299.69 μm (LowPS), 489.85 μm (MediumPS) and 734.83 μm (HighPS) with geometric standard deviation (Sgw) 1.75 μm, 1.62 μm and 1.67 μm, respectively.3. Results showed that the growth performance variables and organ indices were not different among the four groups. The MediumPS group had increased TG, T-CHO, ALT, HDL-C, and GSH-PX levels and decreased T-AOC levels, whereas LowPS and HighPS groups had increased HDL-C and GSH-PX levels (p < 0.05). Microbial diversity analysis showed that the intestinal microbiota of yellow feather broilers mainly included Firmicutes and Bacteroidetes. Inclusion of 5% soyhulls with different particle size had no effect on alpha diversity indices of caecal microbiota. The HighPS group had significantly higher relative abundance of Firmicutes spp. and lower Bacteroidetes spp. compared with the LowPS and MediumPS group but this was not different from the Control group. The relative abundance of Cyanobacteria spp. was significantly higher in the HighPS group than the other three groups. LEfSe analysis showed that there were more enriched biomarker taxa in the groups with soyhulls than the control group.4. Overall, the inclusion of soyhulls with different particle sizes had limited effects on growth performance, blood indices and caecal microbiota composition of yellow feather broilers.

Quality improvement of soybean meal by yeast fermentation based on the degradation of anti-nutritional factors and accumulation of beneficial metabolites

BACKGROUND

Soybean meal (SBM) is the main protein source for animal diets but its anti-nutritional constituents affect animal growth and immunity. The yeast culture of soybean meal (SBM-YC) that fermented with yeast and hydrolyzed by protease simultaneously could reduce anti-nutritional factors effectively and accumulate beneficial metabolites.

RESULTS

The crude protein and acid-soluble protein content of SBM-YC reached 542.5 g kg-1 and 117.2 g kg-1 , respectively, and the essential amino acid content increased by 17.9%. Raffinose and stachyose decreased over 95.0%, and the organic acid content such as acetic acid, butyric acid, citric acid, lactic acid, succinic acid, and propionic acid produced by fermentation reached 6.1, 3.8, 3.6, 2.5, 1.2, and 0.4 g kg-1 , respectively. As biomarkers of yeast culture, nucleosides and their precursors reached 1.7 g kg-1 ; in particular, the inosine content increased from 0 to 0.3 g kg-1 . The total antioxidant capacity, 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) free radical activity, metal chelating ability, and 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging ability were increased by 50.3%, 46.1%, 43.9%, and 20.6%, respectively.

CONCLUSION

This study established a diversified evaluation index, which could lay the foundations for the production and quality control of SBM-YC in the future. © 2023 Society of Chemical Industry.

Effects of processing technologies on the antioxidant properties of common bean (Phaseolus vulgaris L.) and lentil (Lens culinaris) proteins and their hydrolysates

The effects of ultrasound (280 W, 5 min), heat treatment (75 °C and 90 °C for 10 min) and microfluidization (125 MPa, 4 cycles) as pre or post treatments and their combination with enzymatic hydrolysis on the antioxidant properties of common bean and lentil protein hydrolysates were investigated. In general, hydrolysis resulted in increases of antioxidant activity, both in the presence and absence of processing technologies. The increases reached maximum values of 158% (ABTS), 105% (DPPH), 279% (FRAP) and 107% (TAC) for the bean protein hydrolysates submitted to post-treatment with ultrasound (ABTS, FRAP and TAC) and pre-treatment with microfluidization (DPPH), compared to their respective controls (untreated samples). For lentil proteins, the increases reached 197% (ABTS), 170% (DPPH), 690% (FRAP) and 213% (TAC) for samples submitted to ultrasound post-treatment (ABTS), microfluidization pre-treatment (DPPH) and post-treatment (FRAP), and 75 °C pre-treatment (TAC) compared to their respective controls. Surface hydrophobicity and molecular weight profile by SEC-HPLC analysis indicated modifications in the structures of proteins in function of the different processing technologies. For both proteins, electrophoresis indicated a similar profile for all hydrolysates, regardless of the process applied as pre or post treatment. Solubility of bean and lentil protein concentrates was also improved. These results indicated that different processing technologies can be successfully used in association with enzymatic hydrolysis to improve the antioxidant properties of lentil and bean proteins.

Development, characterization and in vivo zinc absorption capacity of a novel soy meal hydrolysate-zinc complexes

Background

Zinc is an essential trace element for the human body. Recently, a novel Zn-binding peptide, Lys-Tyr-Lys-Arg-Gln-Arg-Trp (PP), was purified and identified from soy protein hydrolysates with high Zn-binding capacity (83.21 ± 2.65%) by our previous study. The preparation of soy meal hydrolysates (SMHs)-Zn complexes is convenient and low-cost, while PP (Lys-Tyr-Lys-Arg-Gln-Arg-Trp)-Zn complexes have a higher coordination rate but a relatively high cost. The aim of this study was to investigate the effect of soy meal hydrolysates (SMHs)-Zn complexes on zinc absorption in mice model, and synthetic soy peptide (PP)-Zn complexes with high Zn-binding capacity were used as control. Firstly, SMHs were prepared by enzymolysis, and the PP (Lys-Tyr-Lys-Arg-Gln-Arg-Trp) were synthesized based on previous studies. The binding mechanism of soy hydrolysates and zinc was analyzed by spectral analysis. Furthermore, the cytotoxicity of the SMHs-Zn complexes was also studied using the CCK-8 method. The effect of zinc absorption was evaluated based on Zn content, total protein and albumin content, relevant enzyme system, and the PeT1 and ZnT1 mRNA expression levels.

Result

The result showed that zinc was bound with carboxyl oxygen and amino nitrogen atoms on SMHs, with hydrophobic and electrostatic interactions as auxiliary stabilizing forces. SMHs-Zn were proved to have great solubility and a small particle size at different pH values, and it showed a beneficial effect on Caco-2 cells growth. Moreover, it was proved that SMHs-Zn and PP-Zn could increase the levels of zinc and the activity of Zn-related enzymes in mice. SMHs-Zn possessed higher PepT1 and ZnT1 mRNA expression levels than PP-Zn in the small intestine.

Conclusion

SMHs-Zn with a lower Zn-binding capacity had similar effects on zinc absorption in mice as PP-Zn, suggesting that the bioavailability of peptide-zinc complexes in mice was not completely dependent on their Zn-binding capacity, but may also be related to the amino acid composition.

The Anti-Fatigue Effect of Glycoprotein from Hairtail Fish (Trichiurus lepturus) on BALB/c Mice

Fatigue is related to a variety of chronic diseases and has become a hot research topic in recent years. Various bioactive components have been extracted from hairtail fish (Trichiurus lepturus); however, none of these studies involved the anti-fatigue activity of hairtail fish glycoprotein (HGP). Thus, antioxidant experiments were conducted in vitro, and the anti-fatigue activity of HGP was further evaluated in BALB/c mice. The effects of HGP on the behavior of BALB/c mice were verified by classical behavioral experiments, and the indicators related to anti-fatigue activity were detected. The results showed that the antioxidant capacity in vitro of HGP increased gradually in the concentration range of 10 to 100 mg/mL. HGP improved the exercise ability of the mice. HGP was also found to significantly (p < 0.05) reduce the serum levels of lactate dehydrogenase (LDH), blood lactic acid (BLA), blood urea nitrogen (BUN), and creatine kinase (CK). The contents of liver glycogen (LG) and muscle glycogen (MG) were also significantly (p < 0.05) increased by HGP. Malondialdehyde (MDA) content in the serum and brains of the mice was significantly (p < 0.05) reduced and catalase (CAT), glutathione peroxidase (GPX), and superoxide dismutase (SOD) were significantly (p < 0.05) increased by HGP, especially in the middle- and high-dose groups. These results enhance our understanding of the anti-fatigue function of HGP and lay an important foundation for the further development and utilization of hairtail fish resources.

A Novel Formula Comprising Wolfberry, Figs, White Lentils, Raspberries, and Maca (WFWRM) Induced Antifatigue Effects in a Forced Exercise Mouse Model

Long-term body fatigue poses a threat to human health. To explore novel sources of antifatigue medicine and food, we developed a novel formula composed of wolfberry, figs, white lentils, raspberries, and maca (WFWRM) according to the theory of traditional Chinese medicine. In this study, we explored whether the administration of the WFWRM relieves fatigue. Thirty male Kunming mice were divided into three groups, which received either intragastric administration of saline, vitamin C (100 mg/kg), or WFWRM (1.00 g/kg) every day. After 30 days of treatment, all mice exhaustively performed weight-bearing swimming. Another ten mice that did not perform swimming were treated with saline for 30 days and used as sedentary control. The antifatigue effect and biochemical oxidation phenomena were assessed in the exercise-exhausted model and sedentary controls. The histopathological changes in the liver and kidney tissues of mice were observed by performing hematoxylin-eosin (HE) staining. After 30 days of oral administration, the liver and kidney tissues of mice were healthy and show no pathological changes. Compared to the fatigue model group, WFWRM significantly increased the rota-rod time of the mice. Also, the concentrations of lactic acid (LA), blood urea nitrogen (BUN), creatine kinase (CK), and lactate dehydrogenase (LDH) in the WFWRM group significantly reduced. On the contrary, the levels of hepatic glycogen (LG), muscle glycogen (MG), and serum glucose (GLU) increased in the WFWRM group. Besides, WFWRM markedly reduced the levels of malondialdehyde (MDA) but increased the levels of glutathione peroxidase (GSH-PX) and superoxide dismutase (SOD). Pearson correlation analysis indicated that the concentrations of the sources of energy (LG, MG, and GLU) significantly correlated with those of metabolites (BLA, BUN, CK, and LDH) and antioxidant levels (SOD, GSH-PX, and MDA). Overall, our results suggested that the supplementation of WFWRM could improve exercise capacity and relieve fatigue probably by normalizing energy metabolism and attenuating oxidation.

Hybrid high-intensity ultrasound and microwave treatment: A review on its effect on quality and bioactivity of foods

With the growing of consumer's demand for products ready to eat that can be elaborated with greener technologies without affecting to their organoleptic characteristics, the application of ultrasound combined with microwaves has been widely studied on food preservation treatments (drying, frying), extraction of high-value added compounds and enzymatic hydrolysis of proteins. This review presents a complete picture of current knowledge on the ultrasound combined with microwaves including the mechanisms, influencing factors, advantages and drawbacks, emphasising in several synergistic effects observed in different processes of strong importance in the food industry. Recent research has shown that this hybrid technology could not only minimise the disadvantages of power US for drying and frying but also improve the product quality and the efficiency of both cooking processes by lowering the energy consumption. Regarding extraction, current studies have corroborated that the combined method presents higher yields in less time, in comparison with those in the respective ultrasound and microwave separately. Additionally, recent results have indicated that the bioactive compounds extracted by this combined technology exhibit promising antitumor activities as well as antioxidant and hepatoprotective effects. Remarkably, this hybrid technology has been shown as a good pre-treatment since the structural changes that are produced in the molecules facilitate the subsequent action of enzymes. However, the combination of these techniques still requires a proper design to develop and optimized conditions are required to make a scale process, and it may lead to a major step concerning a sustainable development and utilization of bioactive compounds from natural products in real life.

Structural characterization, erythrocyte protection, and antifatigue effect of antioxidant collagen peptides from tilapia (Oreochromis nilotica L.) skin

Tilapia (Oreochromis nilotica L.) skin collagen is a meritorious commercial resource to be exploited. The purpose of this study was to obtain, evaluate, and characterize tilapia skin collagen-derived antioxidant hydrolysates (TSCP). AAPH-induced erythrocyte hemolysis assay and antifatigue test in mice were implemented. It was indicated that TSCP treatment at 1 mg mL-1 could effectively attenuate AAPH-induced erythrocyte hemolysis rate from 56.35 ± 2.46% to 18.78 ± 2.48% (p < 0.01). A 2.5 mg/(10 g d) dose of TSCP intragastric administration could observably prolong the exhaustive swimming time of the loaded mice and its mechanism was multiple, including the decrease in the levels of serum lactic acid, serum urea nitrogen, and creatine kinase activity, thus improving the contents of liver and muscle glycogen and endogenous SOD activity. Five oligopeptides from the antioxidant fraction were identified as Gly-Hyp, Glu-Asp, Asp-Hyp-Gly, Glu-Pro-Pro-Phe, and Lys-Pro-Phe-Gly-Ser-Gly-Ala-Thr and then synthesized. Among them, the octapeptide exhibited the strongest antioxidant capacity. Therefore, tilapia skin-derived collagen is a meritorious edible resource for producing commercial functional foods, thus helping to scavenge radicals, protecting erythrocytes, and further resisting fatigue.

Enzyme-Assisted Aqueous Extraction of Cobia Liver Oil and Protein Hydrolysates with Antioxidant Activity

Cobia, Rachycentron canadum, is a medium-size marine fish with emerging global potential for offshore aquaculture. The processing waste, cobia liver, is a raw material rich in polyunsaturated fatty acid oils. In this study, an environmentally friendly green process, aqueous extraction (AE), was used to extract the cobia liver oil. The effect of cooking time and substrate water ratio on the oil extractability was investigated herein. The cooking time of 15 min, and substrate water ratio of 1:2 obtained the highest extraction efficiency. However, the oil extractability was only 18.8%. Thus, enzyme-assisted aqueous extraction (EAAE) was used to increase oil extractability and recovery of protein hydrolysates. The commercial proteases—including alcalase, papain, trypsin, and pepsin—were employed in pretreated cobia liver in order to increase oil release during AE. The EAAE results showed that maximum oil extractability was 38% by papain pretreatment. EAAE greatly improved the extraction efficiency; the oil extractability was double than that of AE (18.8%). The fatty acid profiles revealed that ω-3 polyunsaturated fatty acid contents of extracted oil obtained from AE and EAAE were 21.3% and 19.5%, respectively. Besides, the cobia liver hydrolysates obtained from EAAE by alcalase, papain, pepsin, and trypsin pretreatment showed scavenge DPPH radical activity with EC50 values of 0.92, 1.03, 0.83, and 0.53 mg, respectively. After in vitro simulated gastrointestinal digestion, the protein hydrolysates exhibited scavenge DPPH radical activity with EC50 values of 1.15, 1.55, 0.98, and 0.76 mg for alcalase, papain, pepsin, and trypsin, respectively. The study showed that the EAAE process can be used for extracting fish oil from fish waste while simultaneously obtaining the protein hydrolysates with antioxidant activity.

The Impact of Wheat Bran on the Morphology and Physiology of the Gastrointestinal Tract in Broiler Chickens

Simple Summary

Recently, dietary fiber has gained special attention due to its various beneficial effects on poultry. In poultry, moderate amounts of insoluble dietary fiber have been shown to be beneficial to nutrient utilization by improving the physiology of the gastrointestinal tract. Therefore, this study used wheat bran as a source of insoluble fiber to investigate wheat bran on digestive function in broiler chickens. The results indicate that supplementation of 30 g/kg wheat bran enhanced nutrient digestibility by improving antioxidant status, gizzard development, intestinal digestive enzyme activities and morphology in broilers. In conclusion, wheat bran could be used for improving feed efficiency in broilers.

Abstract

There is increasing evidence showing that moderate amounts of insoluble dietary fiber can improve nutrient utilization by positively influencing the physiology of the gastrointestinal tract. The present study was conducted to investigate the effects of wheat bran as a source of insoluble fiber on nutrient digestibility, serum antioxidant status, gastrointestinal development, digestive enzyme activities and intestinal morphology in broiler chickens. A total of 96 one-day-old male Arbor Acre broiler chickens were assigned to two treatments with six replicate cages per treatment and eight birds per replicate for 42 d. Dietary treatments consisted of the control group (CON, control diet) and wheat bran group (WB, 30 g/kg wheat bran). Inclusion of WB increased (p < 0.05) the digestibility of dry matter, organic matter, gross energy and crude protein on Day 42. Birds fed WB had lower (p < 0.05) serum total cholesterol concentration on Day 21, and lower (p < 0.05) serum concentrations of low-density lipoprotein, total cholesterol and total triglyceride on Day 42. Inclusion of WB increased (p < 0.05) serum glutathione peroxidase activity on Day 21 and superoxide dismutase activity on Day 42, but tended (p = 0.07) to decrease serum malondialdehyde concentration on Day 21, and significantly decreased (p < 0.05) serum malondialdehyde concentration on Day 42. Birds fed WB had a greater (p < 0.05) relative weight of gizzard on both Day 21 and 42. Inclusion of WB increased (p < 0.05) activities of amylase and trypsin in pancreas and jejunal mucosa on Day 21, and increased (p < 0.05) amylase activity in pancreas and jejunal mucosa. Birds fed WB had greater (p < 0.05) villus height and villus height to crypt depth ratio in jejunum and ileum on Day 42. In conclusion, supplementation of 30 g/kg WB enhanced nutrient digestibility by improving antioxidant status, gizzard development, intestinal digestive enzyme activities and morphology of broilers.

Antioxidant and Antibacterial Peptides from Soybean Milk through Enzymatic- and Membrane-Based Technologies

Enzymatic hydrolysis of soybean milk proteins with cysteine protease papain was performed in an advanced bioreactor, operated with batch mode. In soybean milk protein hydrolysis reaction, enzyme and substrate ratio and reaction temperature were varied, ranging from 0.029:100–0.457:100 and 30–60 °C, respectively. The degree of hydrolysis of soybean milk proteins was increased with increase of enzyme and substrate (soybean milk protein) ratio. However, the degree of hydrolysis was increased due to change of reaction temperature from 30 °C to 60 °C with enzyme and substrate ratio 0.229:100 and was reduced when hydrolysis reaction was performed with enzyme and substrate ratio 0.11:100 at hydrolysis temperature 60 °C. Antioxidant capacity of enzyme-treated milk had a similar trend with degree of hydrolysis. In a later exercise, a membrane bioreactor was adopted for continuous production of antioxidant and antibacterial peptides from soybean milk. The membrane bioreactor was operated for 12 h with constant feeding. Ceramic-made tubular membrane with a pore size 20 nm was used. Application of static turbulence promoter in a membrane separation process was investigated and its positive effects, with respect to higher permeate flux and lower energy consumption in filtration process, were proven. Antioxidant capacity and antibacterial activity against Bacillus cereus of enzyme-hydrolyzed milk and permeate from membrane were confirmed.

A value-added approach to improve the nutritional quality of soybean meal byproduct: Enhancing its antioxidant activity through fermentation by Bacillus amyloliquefaciens SWJS22

The action of β-glucosidase and protease of Bacillus amyloliquefaciens SWJS22 in the fermentation of soybean meal caused a significant increase 1): in total phenolic and flavonoid contents with two-fold or higher, largely associated with daidzein, glycitein, genistein, protocatechuic, and p-hydroxybenzoic, gallic acids; 2): the amount of peptides <3 kDa, maillard reaction intermediate and maillard reaction product with five-, three- and twenty-one-fold, respectively. The significant increase in the amount of antioxidant components in the lyophilised fermented soybean meal supernatant (LFSMS) was associated with the improved antioxidant activity. Namely, the DPPH radical scavenging activity, reducing power, and oxygen radical absorbance capacity of the LFSMS generally increased, and LFSMS (at doses >250 mg/kg body weight) improved the activities of superoxide dismutase, glutathione peroxidase, catalase and total antioxidant capacity, and inhibited the formation of malondialdehyde in mouse serum and liver (p < 0.05). Therefore, LFSMS could be used as functional food ingredients.

Anti-fatigue activity of sea cucumber peptides prepared from Stichopus japonicus in an endurance swimming rat model

BACKGROUND

Sea cucumber (Stichopus japonicus) is a well-known nutritious and luxurious seafood in Asia which has attracted increasing attention because of its nutrition and bioactivities in recent years. In this study, the anti-fatigue activity of sea cucumber peptides (SCP) prepared from S. japonicus was evaluated in a load-induced endurance swimming model.

RESULTS

The SCP prepared in this study was mainly made up of low-molecular-weight peptides (<2 kDa). The analysis result of amino acid composition revealed that SCP was rich in glycine, glutamic acid and proline. The endurance capability of rats to fatigue was significantly improved by SCP treatment. Meanwhile, the remarkable alterations of energy metabolic markers, antioxidant enzymes, antioxidant capacity and oxidative stress biomarkers were normalized. Moreover, administration of SCP could modulate alterations of inflammatory cytokines and downregulate the overexpression of TRL4 and NF-κB.

CONCLUSION

SCP has anti-fatigue activity and it exerted its anti-fatigue effect probably through normalizing energy metabolism as well as alleviating oxidative damage and inflammatory responses. © 2017 Society of Chemical Industry.

Effects of ultrasound pre-treatment on the structure of β-conglycinin and glycinin and the antioxidant activity of their hydrolysates

The effect of power, time and temperature of ultrasound on the structure of β-conglycinin (7S) and glycinin (11S), and on the antioxidant activity of their hydrolysates were investigated. All ultrasound treated 7S and 11S fractions showed an increase in the α-helix and β-turn proportions, and a decrease in β-sheet and random coil proportions. The polarity of 7S and 11S microenvironment increased after ultrasound treatment. Ultrasound treatment significantly increased the reduction capacity and iron chelating capacity of 7S and 11S hydrolysates. The degree of hydrolysis and free SH groups of 7S and 11S hydrolysates increased after ultrasound pre-treatment. The relative content of high molecular weight peptides reduced, and the relative content of low molecular weight peptides increased in ultrasound treated 7S and 11S hydrolysates. The ultrasonication exposed certain groups of 7S and 11S fractions, improved contact with enzymes, and increased the content of highly active soybean antioxidant peptides.

Short-term effects of troxerutin (vitamin P4) on muscle fatigue and gene expression of Bcl-2 and Bax in the hepatic tissue of rats

In the current study, the effects of troxerutin (TRX) on muscle fatigue and gene expression of Bcl-2 and Bax in the hepatic tissue of rats was investigated. Forty male Wistar rats were randomly divided into 4 groups and designated as control and TRX treatment at 75 (TRX75), 150 (TRX150), and 300 mg/kg per day (TRX300). The treated groups and control group received TRX and water orally for 7 days. After an exhaustive swimming test on the 7th day, all animals were euthanized immediately and several biochemical parameters related to fatigue and gene expression of Bcl-2 and Bax in the hepatic tissue were measured. Our results showed that the exhaustion swimming time in the TRX300 groups significantly increased 1.2-fold compared with the control group (P < 0.001). TRX300 significantly reduced ALT (P < 0.05) activity and increased liver SOD activity compared with the control group (P < 0.01). Additionally, TRX significantly reduced the liver mRNA expressions of Bax (P < 0.001) and increased the Bcl-2/Bax ratio (P < 0.001) compared with the control group. Based on our data, TRX possesses anti-apoptotic and hepatoprotective action following exhaustive swimming exercise.