Effects of β-OH Butyrate on Bovine Granulosa and Theca Cell Function in Vitro

In this study, the effects of beta-OH butyrate (BHB) levels, associated with a negative energy balance, on bovine granulosa and theca cell function were investigated in vitro. Granulosa and theca cells of healthy large follicles (>8 mm), obtained from slaughterhouse ovaries, were cultured in serum free medium containing 0, 0.5, 1 or 1.5 mm BHB and 3 mm glucose, to mimic the situation in the early postpartum dairy cow. Hormone concentrations (progesterone, oestradiol-17beta and/or androstenedione) in spent medium and cell numbers were measured after 48 h of culture. No effects of BHB on theca cell numbers or on steroid production were observed. In granulosa cells, all BHB treatments evenly increased cell numbers (p < 0.05), while they reduced progesterone and oestradiol-17beta production per cell (p < 0.05). These effects may be attributed to the use of BHB as energy source which is however differently metabolized than glucose. Conclusively, in the presence of physiological glucose concentrations BHB can modulate granulosa but not theca cell function in vitro.     

Relationship of Progesterone,Bovine Pregnancy-Associated Glycoprotein-1 and Nitric Oxide with Late Embryonic and Early Fetal Mortalities in Dairy Cows

The aim of the present study was to determine the relationship of progesterone (P4), bovine pregnancy-associated glycoprotein-1 (bPAG-1) and nitric oxide (NO) levels with late embryonic (LEM; day 28 to day 42) and early fetal mortalities (EFM; > day 42 to day 56) in dairy cows. Transrectal ultrasonography (6–8 MHz) was performed in 100 Holstein-Friesian cows at days 28, 42 and 56 after artificial insemination (AI; day 0) to diagnose pregnancy and to monitor the fate of the embryo. After ultrasound scanning of each cow, a milk sample was collected for assessment of P4 by an ELISA test and a blood sample was collected for assessment of bPAG-1, by using a double-antibody radioimmunoassay, and serum NO metabolites (nitrate + nitrite). Based on ultrasonographic examinations and bPAG-1-RIA, 41 of 100 inseminated cows were confirmed pregnant at day 28 after AI. Nine cows suffered of LEM, and 6 cows suffered of EFM and the overall pregnancy loss rate was 36.6% (15/41) between days 28 and 56 of pregnancy. By logistic regression analysis, there were no significant relationships between the level of P4 and bPAG-1 at day 28 after AI and the occurrence of LEM and EFM. Also, there were no significant relationships between the levels of P4 and bPAG-1 at day 42 and the occurrence of EFM. On the other hand, a significant relationship (P<0.05) was found between NO level at day 28 and the occurrence of LEM. In conclusion, measurement of the serum NO concentration at day 28 of pregnancy might help to predict the outcome of pregnancy by day 42 in dairy cows but further studies are needed to confirm this.     

抑制PERK对LPS诱导的奶牛乳腺上皮细胞自噬的影响

旨在研究PERK在脂多糖(LPS)诱导的奶牛乳腺上皮细胞自噬中的作用。首先,试验设对照组(CON)和LPS组(LPS,4μg·mL^-1),研究LPS对奶牛乳腺上皮细胞内质网应激和自噬的影响;随后用不同浓度的PERK抑制剂GSK2606414(GSK)预处理细胞,通过测定PERK、ATF4、eIF-2α和CHOP的mRNA表达,筛选出GSK的最佳抑制浓度;最后将奶牛乳腺上皮细胞分为对照组(CON)、LPS组(LPS)、GSK+LPS组(GLPS)和GSK组4组,研究抑制PERK对LPS诱导的奶牛乳腺上皮细胞自噬的影响。采用RT-qPCR和Western blot分析内质网应激、自噬相关基因和蛋白的表达,通过免疫荧光检测GRP78和p62的荧光强度。结果表明：1)与对照组相比,LPS组的PERK、IRE1α、ATF6、GRP78和CHOP的mRNA和蛋白表达均显著(P<0.05)或极显著(P<0.01)升高。LPS还可以显著升高LC3、ATG5、ATG14和Beclin1的mRNA和蛋白表达(P<0.01),并且显著降低p62的mRNA和蛋白表达(P...     

阴外动脉注射脂多糖对奶牛临床症状及白细胞的影响

为观察泌乳奶牛阴外动脉注射脂多糖(lipopolysaccharides ,LPS)后对临床症状及白细胞(WBC)的影响,选用6头泌乳后期的中国荷斯坦奶牛,用注射LPS处理和空白对照交叉试验设计,每期试验持续一周,期间3头牛进行阴外动脉LPS注射(Escherichia coli 0111:B4,0.01 μg LPS/kg体重),另外3头牛在阴外动脉注射生理盐水。结果表明,与对照组相比,注射LPS极显著影响奶牛的呼吸频率(P＜0.01),在注射后3 h达到最高;注射LPS后对奶牛直肠温度没有影响;注射LPS极显著影响奶牛脉搏(P＜0.01),在注射后6 h达到最高;注射LPS极显著影响奶牛血液中WBC数(P＜0.01),且对其分类计数没有影响。因此,当给奶牛阴外动脉注射LPS后,会影响奶牛的临床症状和WBC数。     

Effects of FSH and LH on Steroid Production by Buffalo (Bubalus bubalis) Granulosa Cells Cultured In Vitro Under Serum‐Free Conditions

The objective of this study was to examine the effects of FSH and LH on oestradiol‐17β and progesterone production by buffalo granulosa cells cultured under serum‐free conditions. Granulosa cells (3 × 10⁵) from small (≤5 mm diameter) follicles were cultured for up to 4 days in 48‐well plates coated with 3.3 μg/cm² fibronectin in Dulbecco's modified Eagle's medium (DMEM) : nutrient mixture F‐12 Ham (1 : 1 ratio) supplemented with 10^?7 m androstenedione, 5 μg/ml human apo‐transferrin and 0.1% bovine serum albumin, in the presence or absence of FSH or LH (0, 1, 2, 4, 8, 16, 32 or 64 ng/ml each). Basal oestradiol‐17β production by granulosa cells from small follicles reduced (p < 0.01) from days 1 to 2 of culture and became undetectable by day 3 and basal progesterone production increased (p < 0.05) from day 1 through day 4 of the culture. Although there was no effect of FSH on day 1 of the culture, FSH at 2, 4, 8 and 16 ng/ml increased (p < 0.05) oestradiol‐17β production by granulosa cells from small follicles on day 2. Progesterone secretion was increased (p < 0.05) by all doses of FSH on all days of culture. All doses of LH had no effect on oestradiol‐17β or progesterone production by granulosa cells from small follicles on any day of the culture. The results of this study demonstrate a serum‐free culture system for buffalo granulosa cells and stimulatory effect of FSH but not LH on steroid hormone production by buffalo granulosa cells under these conditions.     

脂多糖对体外培养奶牛子宫内膜上皮细胞子宫容受性因子表达的影响

试验旨在通过脂多糖（lipopolysaccharide,LPS）诱导奶牛子宫内膜上皮细胞构建子宫内膜炎体外感染模型,研究子宫内膜炎对奶牛子宫容受性因子大分子转膜黏蛋白-糖蛋白1（MUC-1）、高度保守的分泌型WNT家族亚型糖蛋白（Wnt-7a）、β受体1（IFNAR1）、IFNAR2、Integrin αvβ3 mRNA及蛋白相对表达量的影响,进而阐明子宫内膜炎引起奶牛屡配不孕和繁殖率低下的机制。采用组织块法分离培养奶牛子宫内膜上皮细胞,免疫荧光方法鉴定细胞纯度,不同浓度LPS刺激子宫内膜上皮细胞,在不同时间点用CCK8测定细胞存活率,ELISA检测炎性因子白细胞介素-1β（IL-1β）、肿瘤坏死因子-α（TNF-α）、IL-6、IL-8的分泌变化,实时荧光定量PCR和Western blotting分别检测子宫内膜感染模型中子宫容受性因子MUC-1、Wnt-7a、IFNAR1、IFNAR2、Integrin αvβ3 mRNA及蛋白的表达变化。结果显示,通过组织块法纯化获得的奶牛子宫上皮细胞数量较多,经免疫荧光角蛋白染色证实纯度较高。采用CCK8测定细胞存活率发现,与对照组相比,浓度为0、5、10、50μg/mL的LPS作用6、12、24、48 h后,细胞活力无显著变化（P>0.05）;浓度为100μg/mL的LPS作用24 h时,细胞存活率显著低于对照组（P<0.05）,细胞培养上清中的IL-1β、TNF-α、IL-6、IL-8含量均显著高于对照组及低浓度组（P<0.05）,引起细胞的炎症反应。与对照组相比,模型组MUC-1 mRNA及蛋白的相对表达量均极显著增加（P<0.01）;Wnt-7a mRNA及蛋白的相对表达量均极显著下降（P<0.01）;Integrin αvβ3、IFNAR1和IFNAR2 mRNA相对表达量均极显著下降（P<0.01）,蛋白相对表达量均显著下降（P<0.05）。结果表明,浓度为100μg/mL的LPS作用24 h可成功构建子宫内膜炎体外感染模型,子宫内膜炎对奶牛子宫容受性因子MUC-1、Wnt-7a、IFNAR1、IFNAR2、Integrin αvβ3 mRNA及蛋白表达的影响可能是引起奶牛屡配不孕和繁殖率低下的重要原因。     

Regulation of Innate Immune Function in Bovine Oviduct Epithelial Cells in Culture: The Homeostatic Role of Epithelial Cells in Balancing Th1/Th2 Response

This study aimed to investigate the role of epithelial cells in regulating innate immunity in bovine oviduct epithelial cell (BOEC) culture. We studied the effect of Escherichia coli lipopolysaccharide (LPS) and its interaction with ovarian steroids, estradiol (E2) and progesterone (P4), and luteinizing hormone (LH) at concentrations observed during the preovulatory period on immune responses in BOEC culture. Immunohistochemistry of oviduct tissue showed intensive expression of Toll-like receptor-4 (TLR-4) and TLR-2 in epithelial cells. A dose of 10 ng/ml LPS stimulated TLR-4, cyclooxygenase-2 (COX-2), nuclear factor kappa B inhibitor A (NFKBIA), interleukin 1β (IL-1β) and tumor necrosis factor α (TNF-α) expression, indicating an early pro-inflammatory response. A dose of 100 ng/ml LPS did not induce expression of these genes but stimulated TLR-2, IL-10,IL-4 and microsomal prostaglandin E synthase-1 (mPGES-1) expression and PGE2 secretion, indicating an anti-inflammatory response. Ovarian steroids and LH completely block LPS (10 ng/ml)-induced TLR-4, IL-1β and TNF-α expression as well as LPS (100 ng/ml)-induced TLR-2 expression. Taken together, this study suggests the existence of an early signaling system to respond to infection in the BOEC. In addition, ovarian steroids and LH may play a critical role in inducing homeostasis and in controlling hyperactive pro-inflammatory responses detrimental to epithelial cells, sperm and the embryo.     

类固醇激素对牛输卵管上皮细胞分泌的调节及其分泌物对小鼠胚胎发育的影响

模拟发情期（０～６ｄ）母牛外周血浆雌激素和孕酮变化水平，在添加相应水平１７β－雌二醇和孕酮的ＴＣＭ－１９９液中，培养间情期牛输卵管上皮细胞（ＢＯＥＣ）。５％ＳＤＳ－ＰＡＧＥ分析ＢＯＥＣ分泌物，发现上皮细胞受类固醇激素作用分泌的２类蛋白质分子量与自然发情期（０～６ｄ）分泌的特异蛋白相似。证明类固醇激素可以调节和启动间情期ＢＯＥＣ的分泌活动。当雌二醇浓度高达１ｍｇ／Ｌ时，即使不加孕酮，ＢＯＥＣ仍能分泌这２类蛋白质。在培养小鼠原核胚的ＣＺＢ培养液内添加牛输卵管上皮细胞分泌蛋白（ＢＯＥＰ），与添加间情期牛输卵管冲洗蛋白（ＢＯＰ）和小牛输卵管冲洗蛋白（ＣＯＰ）相比，能显著提高通过２－细胞阶段胚胎的百分率和桑囊形成率，表明ＢＯＥＰ能较好地促进胚胎的分裂和发育。但ＢＯＥＰ组的桑囊形成率显著低于对照组，表明ＢＯＥＰ中可能缺少某些低于Ｍｒ１．０×１０４的蛋白因子的协调作用，以及含有Ｍｒ３．０×１０４～５．６×１０４的分泌蛋白的抑制作用而阻碍胚胎分裂与发育。     

Clinical Study Report on Milk Production in the Offspring of a Somatic Cell Cloned Holstein Cow

This study examined two female offspring of a somatic cell cloned Holstein cow that had reproduction problems and milk production performance issues. The two offspring heifers, which showed healthy appearances and normal reproductive characteristics, calved on two separate occasions. The mean milk yields of the heifers in the first lactation period were 9,037 kg and 7,228 kg. The relative mean milk yields of these cows were 111.2% and 88.9%, respectively, when compared with that of the control group. No particular clinical abnormalities were revealed in milk yields and milk composition rate [e.g., fat, protein and solids-not-fat (SNF)], and reproductive characteristics of the offspring of the somatic cell cloned Holstein cow suggested that the cloned offspring had normal milk production.     

硫酸化20(S)-人参皂苷Rh2体外对鸡免疫活性细胞功能的影响

为了评价硫酸化人参皂苷Rh2化学修饰前后免疫活性变化,采用MTT法及流式细胞术研究体外对ConA促鸡外周血淋巴细胞增殖的影响,采用乳酸脱氢酶释放法研究体外对鸡外周血NK细胞杀伤活性的影响。结果表明：Rh2、Rh2溶剂及硫酸化Rh2低浓度时都能促进淋巴细胞增殖,高浓度时能抑制淋巴细胞增殖,Rh2溶剂及硫酸化Rh2都显著（P〈0．05）或极显著（P〈0．01）高于同浓度的Rh2。Rh2及Rh2溶剂都能显著促进鸡外周血NK细胞杀伤活性,但Rh2极显著（P〈0．01）低于同浓度Rh2溶剂,而硫酸化Rh2表现一定促进作用。结果提示：Rb2体外能抑制免疫活性,化学修饰后的硫酸化Rh,体外能促进免疫活性。     

Nuclear Morphometric Analysis of Leydig Cells of Male Pubertal Rats Exposed In Utero to Di(n-butyl) Phthalate

We recently reported that prenatal rat exposure to di(n-butyl) phthalate (DBP) induced Leydig cell (LC) hyperplasia after nine weeks (wks) of age, yet the number of LCs was similar to that of the vehicle group until seven weeks. Nuclear pleomorphism of hyperplastic LCs is common and is considered to be continuous progressive degeneration. Thus, computer-assisted image cell nuclear analysis of LCs was performed on 5- and 7-wk-old Sprague-Dawley (SD) rats whose dams had been administered DBP (i.g.) at 100 mg/kg/day or vehicle (corn oil) on gestation day 12 to 21. The results of the 5-wk-old DBP group were similar to those of the vehicle group; LC nuclei of the 7-wk-old DBP group showed normal ploidy and similar amounts of DNA. However, the size, elongation and peripheral chromatin aggregation parameters were significantly higher, and the reticular chromatin distribution and isolated chromatin aggregation parameters were significantly lower compared with the vehicle group. The present study quantitatively demonstrated nuclear morphological alterations in rat LCs at 7 wks old (puberty) due to the prenatal DBP administration before apparent LC hyperplasia developed.     

Dopamine Release Suppression Dependent on an Increase of Intracellular Ca2+ Contributed to Rotenone-induced Neurotoxicity in PC12 Cells

Rotenone is an inhibitor of mitochondrial complex I that produces a model of Parkinson’s disease (PD), in which neurons undergo dopamine release dysfunction and other features. In neurons, exocytosis is one of the processes associated with dopamine release and is dependent on Ca²⁺ dynamic changes of the cell. In the present study, we have investigated the exocytosis of dopamine and the involvement of Ca²⁺ in dopamine release in PC12 cells administrated with rotenone. Results demonstrated that rotenone led to an elevation of intracellular Ca²⁺ through Ca²⁺ influx by opening of the voltage-gated Ca²⁺ channel and influenced the soluble N-ethylmaleimide attachment protein receptor (SNARE) proteins expression (including syntaxin, vesicle-associated membrane protein 2 (VAMP₂) and synaptosome-associated protein 25 (SNAP-25)); pretreatment with a blocker of L-type voltage-activated Ca²⁺ channels (nifedipine) decreased the intracellular dopamine levels and ROS formation, increased the cell viability and enhanced the neurite outgrowth and exocytosis of synaptic vesicles. These results indicated that the involvement of intracellular Ca²⁺ was one of the factors resulting in suppression of dopamine release suppression in PC12 cells intoxicated with rotenone, which was associated with the rotenone-induced dopamine neurotoxicity.     

酵母培养物水溶物对丙二醛损伤的离体草鱼肠道黏膜细胞的保护作用

在培养液中加入不同浓度(4.94、9.89 μmol/L)的丙二醛(MDA)及酵母培养物水溶物,观察酵母培养物水溶物不同浓度(50、100、200 mg/L)、不同作用时间(3、6、9、12 h)下MDA损伤的离体草鱼肠道黏膜细胞生长、形态及相关酶活力的变化,以研究酵母培养物水溶物对MDA损伤的离体草鱼肠道黏膜细胞的保护作用.结果表明:培养液中添加4.94或9.89μmol/LMDA均显著抑制了离体草鱼肠道黏膜细胞生长(P＜0.05),致使贴壁细胞减少、细胞膜通透性增加,导致胞内酶漏出及细胞抗氧化酶活力降低.培养液中添加50、100、200 mg/L酵母培养物水溶物9h后可显著地促进细胞生长及提高细胞总蛋白含量(P＜0.05),改善细胞生长状态,其中以添加100 mg/L酵母培养物水溶物对4.94 μmol/L MDA损伤细胞的保护效果较好,其细胞生长状态能达到正常组水平.培养液中添加50、100、200酵母培养物水溶物能一定程度地降低培养液中MDA浓度,同时能降低MDA导致的细胞内酶漏出,提高MDA损伤的细胞抗氧化能力.由结果可知,对于4.94、9.89 μmol/L MDA对草鱼肠道黏膜细胞产生的损伤,培养液中添加50、100、200 mg/L酵母培养物水溶物12 h内对细胞均有保护作用,其中以添加100 mg/L酵母培养物水溶物对4.94 μmol/L MDA损伤细胞的保护作用最佳,使细胞生长状态接近正常组水平.酵母培养物水溶物可能通过增强细胞抗氧化能力途径起到对草鱼离体肠道黏膜细胞的保护作用.     

Low Incidence of an Altered Endometrial Epidermal Growth Factor (EGF) Profile in Repeat Breeder Holstein Heifers and Differential Effect of Parity on the EGF Profile Between Fertile Holstein (Dairy) and Japanese Black (Beef) Cattle

A high incidence (about 70%) of alteration in endometrial epidermal growth factor (EGF) profile, i.e., loss of 2 peaks on days 2–4 and 13–14, has been linked to a reduced fertility in multiparous repeat breeder Holstein cows. However, the EGF profile in Holstein heifers and other breeds (types) of cattle has not been investigated. In study 1, EGF concentrations were determined using endometrial tissues obtained by biopsy on days 3, 7 and 14 from 84 fertile Holstein heifers to obtain a normal range and 53 repeat breeder Holstein heifers to estimate incidence of alterations in the EGF profile. In repeat breeder heifers, EGF concentrations were similar to fertile controls on 3 days and five animals (9.4%) had an altered EGF profile with EGF concentrations below the normal range on days 3 and 14. In study 2, EGF concentrations on day 3 were repeatedly examined from the nulliparous period to the third postpartum period in 28 Holstein (dairy) and 47 Japanese Black (beef) cattle. The effect of parity on EGF concentrations on day 3 was different between Holstein and Japanese Black cattle. In Japanese Black cows, the EGF concentrations were consistently high throughout the study period, while in Holstein cows, the EGF concentrations decreased after the second calving. In conclusion, unlike multiparous repeat breeder Holstein cows, an altered EGF profile may not be a major cause of repeat breeding in Holstein heifers, and the peak EGF concentrations around day 3 may decrease even in fertile populations of multiparous dairy cows, but not in beef cows.     

An Acute-phase Protein as a Regulator of Sperm Survival in the Bovine Oviduct: Alpha 1-acid-glycoprotein Impairs Neutrophil Phagocytosis of Sperm In Vitro

We have previously shown that polymorphonuclear neutrophils (PMNs) are present in bovine oviduct fluid under physiological conditions, and that the oviduct provides a microenvironment that protects sperm from phagocytosis by PMNs. Alpha 1-acid glycoprotein (AGP) is a major acute-phase protein produced mainly in the liver that has immunomodulatory functions. AGP mRNA is expressed in extrahepatic organs, such as the lung, kidney, spleen, lymph node, uterus, and ovary. Therefore, in this study, we investigated, 1) the local production of AGP in the bovine oviduct, 2) the effect of AGP on the phagocytic activity of PMNs for sperm and superoxide production and 3) the impact of AGP desialylation on the PMN phagocytosis of sperm. The AGP gene was expressed in cultured bovine oviduct epithelial cells (BOECs) and AGP protein was detected in oviduct fluid. Preexposure of PMNs to AGP at physiological levels impaired PMN phagocytosis for sperm and superoxide generation. The desialylation of AGP eliminated these suppressive effects of AGP on PMN. Scanning electron microscopy revealed that AGP drastically reduced the formation of DNA-based neutrophil extracellular traps (NETs) for sperm entanglement. Additionally, AGP dose-dependently stimulated BOECs to produce prostaglandin E₂ (PGE₂) which has been shown to partially contribute to the regulation of sperm phagocytosis in the bovine oviduct. AGP and PGE₂ at concentrations detected in the oviducts additively suppressed sperm phagocytosis by PMNs. These results provide evidence that locally produced AGP may be involved in protecting sperm from phagocytosis by PMNs in the bovine oviduct.     

前列腺素E2受体激动剂和雌激素对奶牛输卵管上皮细胞中转化生长因子β3表达的影响

本试验旨在观察前列腺素E₂受体激动剂(布他前列腺素(butaprost))与雌激素对奶牛输卵管上皮细胞中转化生长因子β₃(TGFβ₃)表达的影响,阐明butaprost和雌激素对奶牛输卵管上皮细胞TGFβ₃有无协同调控作用.采用胰酶消化法及机械法分离培养奶牛输卵管上皮细胞,分别将butaprost和雌激素作用于体外培养的奶牛输卵管上皮细胞,采用实时荧光定量PCR技术检测butaprost和雌激素对奶牛输卵管上皮细胞中TGFβ₃ mRNA表达的影响.结果显示,与0 h作用组相比,雌激素作用16、24和48 h时对奶牛输卵管上皮细胞TGFβ₃的表达量均极显著升高(P< 0.01),4 h的表达量极显著降低(P< 0.01);且受体激动剂butaprost和雌激素有协同调控TGFβ₃的效应;加入吲哚美辛后能有效抑制内源性前列腺素对TGFβ₃表达的作用.结果表明,butaprost和雌激素可调控奶牛输卵管上皮细胞TGFβ₃ mRNA 的表达.     

酵母培养物水溶物对离体草鱼肠道黏膜细胞生长及细胞膜完整性的影响

本试验以酵母培养物水溶物为试验材料,添加于离体草鱼肠道黏膜细胞培养液中,研究酵母培养物水溶物在不同浓度、不同作用时间下对细胞生长及细胞膜完整性的影响。采用单因子试验设计,设1个对照组及5个酵母培养物水溶物组(YC-1~5组),各组均设96个重复,每个重复为1个培养孔。对照组的培养液中不添加酵母培养物水溶物,YC-1~5组的培养液中酵母培养物水溶物的浓度分别为10、25、50、100、200 mg/L。结果表明:培养液中添加50~200 mg/L酵母培养物水溶物对细胞形态无损伤,100~200 mg/L酵母培养物水溶物在添加后3 h时显著增强细胞活性(P<0.05),50 mg/L酵母培养物水溶物在添加后6 h时显著增强细胞活性(P<0.05)。与对照组相比,3 h时各酵母培养物水溶物组培养液中乳酶脱氢酶(LDH)活力均没有显著变化(P>0.05),6 h时YC-4、YC-5组显著降低(P<0.05),9 h时YC-3、YC-4、YC-5组显著降低(P<0.05),12 h时YC-2、YC-3、YC-4、YC-5组显著降低(P<0.05)。各时间点(3、6、9、12 h)各酵母培养物水溶物组培养液中谷丙转氨酶(GPT)、谷草转氨酶(GOT)活力与对照组相比均没有显著变化(P>0.05),但在6~9 h时GPT活力均低于对照组。由此得出,培养液中添加10~200 mg/L酵母培养物水溶物能促进离体草鱼肠道黏膜细胞的生长,保护细胞膜的完整性,其发挥保护作用的适宜浓度为50~200 mg/L。