The effect of potassium deficiency on growth and N2-fixation in Trifolium repens

The effects of potassium (K) deficiency on growth, N₂-fixation and photosynthesis in white clover ( Trifolium repens L.) were investigated using natural occurring gas fluxes on the nodules in real time of plants under three contrasting relative addition rates of K causing mild K deficiency, or following abrupt withdrawal of the K supply causing strong K deficiency of less than 0.65% in dry matter. A steady-state below-optimum K supply rate led to an increase in CO₂-fixation per unit leaf surface area as well as per plant leaf surface. However, nitrogenase activity per unit root weight and per unit nodule weight was maintained, as was the efficiency with which electrons were allocated to the reduction of N₂ in the nodules. Abrupt K removals stimulated nodule growth strongly without delay, but as K concentrations decreased in the plant tissue a significant decline in nitrogenase activity per unit root weight as well as per unit nodule mass occurred. Further, the rate of photosynthesis per unit leaf area was unaffected, while the CO₂ acquisition for the plant as a whole increased due to an expansion of total leaf area whereas the leaf area per unit leaf weight was unaffected. The ratio between CO₂-fixation and N₂-fixation increased, although not statistically significant, under short-term K deprivation as well as under long-term low K supply indicating a downregulation of nodule activity following morphological and growth adjustments. This downregulation took place despite a partly substitution of the K by Na. It is concluded that N₂-fixation does not limit the growth of K-deprived clover plants. K deprivation induces changes in the relative growth of roots, nodules, and shoots rather than changes in N and/or carbon uptake rates per unit mass or area of these organs.     

Antihyperglycemic activity of Eclipta alba leaf on alloxan-induced diabetic rats

Eclipta alba, an indigenous medicinal plant, has a folk (Siddha and Ayurvedha) reputation in rural southern India as a hypoglycemic agent. In order to confirm this claim, the present study was carried out to evaluate the antihyperglycemic effect of E. alba and to study the activities of liver hexokinase and gluconeogenic enzymes such as glucose-6-phosphatase and fructose 1,6-bisphosphatase in the liver of control and alloxan-diabetic rats. Oral administration of leaf suspension of E. alba (2 and 4 g/kg body weight) for 60 days resulted in significant reduction in blood glucose (from 372.0 +/- 33.2 to 117.0 +/- 22.8), glycosylated hemoglobin HbA(1)c, a decrease in the activities of glucose-6 phosphatase and fructose 1,6-bisphosphatase, and an increase in the activity of liver hexokinase. E. alba at dose of 2 g/kg body weight exhibited better sugar reduction than 4 g/kg body weight. Thus, the present study clearly shows that the oral administration of E. alba possess potent antihyperglycemic activity.     

Studies on the measurement of phospholipase A2 (PLA2) and PLA2 inhibitor activities in ram semen.

Extraction with Tris-citrate or Tris-NaCl-EGTA improved the yield of phospholipase A2 (PLA2) from ram semen by 40-50 fold over the previously recommended method of extraction by dilute (0.18 N) sulphuric acid. The enzyme activity in the citrate extract deteriorated more rapidly than in Tris-NaCl-EGTA. The semen PLA2 activity was optimum at pH 8.0, heat sensitive at 70 degrees C for 30 min, activated by Ca2+ (although approximately 60% activity was also found in the absence of calcium) and did not exist as a pro-enzyme. The semen PLA2 activity was equally distributed among the sperm and seminal plasma (SP) components of ram semen. However, the low levels of PLA2 activity in the SP of vasectomised rams tend to suggest that PLA2 in the SP fraction may have originated from testicular or epididymal secretions or leakage, from sperm. PLA, in sperm exists as a large molecular weight aggregate, whereas in SP it is present as a smaller aggregate. In addition to PLA2, semen also contained PLA2 inhibitor activities. Inhibition was observed against PLA2s from bee venom, pig pancreas and oviductal extracts. The inhibitory activity is presumed to be due to a large molecular weight protein as the inhibitor activity was not extracted in a chloroform:methanol (2:1; v/v) mixture, it was non-dialysable, precipitated by 10% trichloroacetic acid and destroyed by proteases. The inhibitor activity was distributed in various molecular weight fractions of sperm, SP and SP from vasectomised rams.     

乙酰唑胺对氧惊厥潜伏期的影响

为探讨脑血流调节与氧惊厥的关系,在复制大鼠氧惊厥模型的基础上,采用行为学方法测定氧惊厥潜伏期,并测定不司部位脑组织氧化与抗氧化指标,采用腹腔注射不同剂量脑血管扩张药物乙酰唑胺,观察脑血管扩张对氧化状态以及氧惊厥潜伏期的影响。观察结果为:(1)与生理盐水组相比,乙酰唑胺200、20 mg/kg体重组腹腔给药后氧惊厥潜伏期(纯氧6 ATA暴露)明显缩短(P<0.01),乙酰唑胺2 mg/kg体重组无明显改变(P>0.05);(2)腹腔给乙酰唑胺(20 mg/kg体重)或生理盐水后,各组各部位脑组织GSH-PX无显著差异(P>0.05),但随暴露时间的延长,其活力呈现先升高后降低的趋势;与对照组相比,乙酰唑胺6min组和生理盐水16min组皮层丙二醛(maleic dialdehyde,MDA)含量均明显增多(P<0.01),乙酰唑胺16 min组海马MDA含量明显增多(P<0.01)。结果表明,乙酰唑胺可缩短氧惊厥潜伏期,加重脑组织氧化损伤。     

The influence of naringin on the oxidative state of rats with streptozotocin-induced acute hyperglycaemia

The effect of various doses (0, 10, 20, 40, or 80 mg/kg body weight) of naringin (a citrus flavonone) was studied on streptozotocin (STZ)-induced hyperglycaemic rats to evaluate the possible hypoglycaemic and antioxidant activity of naringin in diabetes. In comparison to the normoglycaemic group the treatment of rats with a single dose of STZ (65 mg/kg body weight) only revealed a significant increase (P < 0.05) in plasma hydrogen peroxide (H2O2) by 230%, increased the thiobarbituric acid reactive substances (TBARS) as index of the lipid peroxidation level by 69%, while total antioxidant activity was decreased by 36%, with a consistent significant decrease (P < 0.05) in the activity of erythrocytes antioxidative enzymes catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), and paraoxonase (PON). Exogenous administration of individual gradual doses of naringin to hyperglycaemic rats causes a dose-dependent decrease of the glucose level, an increase of the insulin concentration, a decrease of the H2O2 and TBARS levels, as well as the increase of the total antioxidant status with an increase of antioxidant enzyme activities (CAT, SOD, GPx, and PON). From this study, it may be concluded that all doses of naringin provided a significant amelioration of hypoglycaemic and antioxidant activity in STZ-induced diabetic rats, however, the greatest effect of naringin was observed at 80 mg/kg body weight.     

Acetylene reduction assay on white clover genotypes and on grass/clover swards

Acetylene reduction assay was used to measure the nitrogenase activity of white clover genotypes in pots and of grass/clover swards in situ. Much of the variation in nitrogenase activity of single genotypes and hybrid populations was associated with plant dry weight. After adjustment for plant dry weight it was concluded that there was limited scope for selection for increased nitrogenase activity. In plant breeding this technique would seem to have greatest application in the selection for continued nitrogen fixation activity in the presence of inhibitory factors such as high levels of mineral nitrogen. The in situ studies revealed differences in nitrogenase activity of grass/clover swards based on contrasting cultivars of white clover. These differences were due to variation in clover density and also to variation in activity per unit clover dry weight. It was concluded that the variation in nitrogenase activity per unit dry weight reflected differences in growth pattern of the cultivars in the autumn when these assays were made. The in situ studies offer a means whereby the nitrogenase activity of cultivars and selected families can be monitored under varying levels of mineral nitrogen and other husbandry treatments without disruption of the sward.     

The influence of testosterone on the alkaline proteolytic activity in rat skeletal muscle

The effects of testectomy and subsequent administration of testosterone propionate on the activity of the alkaline proteinases in rat skeletal muscle were investigated. Castration of the mature rat was followed by a short-term delay in protein accretion in skeletal muscle tissue as measured by the protein/DNA ratio and was paralleled by a 2–3 fold increase in specific activity of the alkaline proteinase(s). This increase of proteolytic activity was equally significant when expressed relative to μg DNA. Although the gain in body weight was significantly lower in the castrated rats, nevertheless the protein/DNA ratio in muscle after 6 weeks approximated the values of sham-operated control rats without normalization of the proteolytic activity.Treatment of the castrated rats with testosterone propoinate resulted in restoring normal levels of previously elevated levels of alkaline proteolytic activity in muscle tissue. The normalization of enzyme activity as well as protein accretion in muscle was dose-dependent. Treatment of the rats with a low dose (0.1 mg/day) of testosterone propionate failed to restore the proteolytic activity, but led to a small increase of the protein/DNA ratio as well as to a progressive increase in body weight. These data indicate a regulatory role of testosterone in the adaptive behaviour of the alkaline proteolytic system in rat skeletal muscle.     

莪术油注射液对慢性低氧大鼠学习与记忆的影响

本文旨在探讨莪术油注射液对慢性低氧大鼠学习与记忆的影响及其可能机制.将Sprague.Dawley大鼠随机分为对照组、慢性低氧组、5 mg/kg体重莪术油组、10 mg/kg体重莪术油组、20 mg/kg体重莪术油组,每组14只.慢性低氧处理采用低氧舱内吸入大约10%O2、5%CO2,饲养10 h/d,持续饲养28 d.莪术油组大鼠低氧处理前腹腔注射相应浓度的莪术油注射液.实验结束次日,通过Morris水迷宫测试各组动物学习和记忆成绩的变化;测定各组大鼠血清和海马组织丙二醛(malonaldehyde,MDA)含量和超氧化物歧化酶(superoxide dismutase,SOD)活性以及海马组织Ca2 浓度([Ca2 i]);通过免疫组织化学和Western blot检测磷酸化Ca2 /钙调蛋白依赖性蛋白激酶Ⅱ(phosphorylated Ca2 /calmodulin-dependent pro-tein kinase Ⅱ,p-CaMKII)在海马组织和胞膜上的表达.结果显示,与对照组相比,慢性低氧组大鼠隐蔽平台的逃避潜伏期明显延长(P<0.05),血清和海马组织MDA含量明显增高,SOD活性显著降低(P<0.05,P<0.01),海马组织[Ca2 ]i明显增高(P<0.01),海马P-CaMKII表达量显著降低(P<0.01).与慢性低氧组比较,莪术油各组发生以下变化:10、20 mg/kg体重莪术油组大鼠隐蔽平台的逃避潜伏期显著缩短(P<0.05):5、10、20 mg/kg体重莪术油组大鼠血清和海马组织MDA含量均显著降低(P相似文献   

Effect of oral nitroethane and 2-nitropropanol administration on methane-producing activity and volatile fatty acid production in the ovine rumen

Strategies are sought to reduce economic and environmental costs associated with ruminant methane emissions. The effect of oral nitroethane or 2-nitropropanol administration on ruminal methane-producing activity and volatile fatty acid production was evaluated in mature ewes. Daily administration of 24 and 72 mg nitroethane/kg body weight reduced (P<0.05) methane-producing activity by as much as 45% and 69% respectively, when compared to control animals given no nitroethane. A daily dose of 120 mg 2-nitropropanol/kg body weight was needed to reduce (P<0.05) methane-producing activity by 37% from that of untreated control animals. Reductions in methane-producing activity may have been diminished by the last day (day 5) of treatment, presumably due to ruminal adaptation. Oral administration of nitroethane or 2-nitropropanol had little or no effect on accumulations or molar proportions of volatile fatty acids in ruminal contents collected from the sheep. These results demonstrate that nitroethane was superior to 2-nitropropanol as a methane inhibitor and that both nitrocompounds reduced ruminal methanogenesis in vivo without redirecting the flow of reductant generated during fermentation to propionate and butyrate.     

NADP-dependent dehydrogenases in rat liver parenchyma. II. Comparison of qualitative and quantitative G6PDH distribution patterns with particular reference to sex differences.

Qualitative histochemical G6PDH distribution patterns obtained in the liver acinus of adult male and female rats with an improved method (Rieder et al., 1978) served as a basis for the isolation by microdissection of tissue samples of defined zonal affiliation. G6PDH activity was assayed quantitatively in tissue samples of zones 1 and 3 by a microfluorometric method, using the oil well technique and enzymatic cycling (Burch et al., 1963; Lowry and Passonneau, 1972). With the use of a correlation system further evidence could be presented for the validity of the recently described qualitative distribution patterns. From a total of 50 analyzed tissue samples the following G6PDH activities were calculated: 4.25 +/- 1.56 U/g dry weight in zone 1 and 2.08 +/- 0.46 U/g dry weight in zone 3 of male and 7.21 +/- 1.03 U/g dry weight in zone 1 and 11.10 +/- 2.56 U/g dry weight in zone 3 of female rats. These data were corrected for interference from the G6PDH activity of the Kupffer cells within zone 1 samples (approximately 80 U/g dry weight), so that the actual relative values for the parenchymal activity could be estimated for the first time: 2 U/g dry weight in zones 1 and 3 of male animals, 5 U/g dry weight in zone 1 and 11 U/g dry weight in zone 3 of female animals. In female livers G6PDH activity in zone 1 is therefore 2.5 times higher, and in zone 3 5 times higher than in the male. These zonal as well as sex-differences are clearly indicative of a heterogeneous functional organization of the liver acinus in terms of capacity for NADPH production, mainly in connection with reductive reactions in fatty acid synthesis.     

Glucocorticoid effects on gastric peroxidase activity

The peroxidase activity in rat gastric mucosa is inhibited after administration of glucocorticoids. The synthetic steroid dexamethasone is more potent than the naturally occurring steroids, such as cortisone or corticosterone. Almost complete inhibition of the enzyme occurs after 24 h with a single dose of 100 micrograms dexamethasone/120 g body weight. Other mitochondrial enzyme activities, like monoamine oxidase, succinic dehydrogenase and Mg2+-ATPase, remain unaltered under the same experimental condition. Submaxillary peroxidase and thyroid peroxidase activity are not inhibited by dexamethasone. Gastric peroxidase activity is increased 200-250% on the 6th day after adrenalectomy. This effect is blocked by the administration of dexamethasone. In fact, the enzyme becomes more sensitive to dexamethasone after adrenalectomy, since it is inhibited by more than 90% at the dose of 25 micrograms/120 g body weight. The inhibition by dexamethasone in normal animals is reversible. The enzyme is also inhibited after the administration of a single dose of ACTH. The apparent Km of the enzyme for H2O2 is not altered after dexamethasone treatment or after adrenalectomy. The increase in enzyme activity following adrenalectomy is not blocked by actinomycin D or by alpha-amanitin, but is prevented by puromycin or cycloheximide. After administration of dexamethasone, the iodide concentration process in the gastric mucosa is not affected, but the organification of iodide is significantly diminished.     

Aromatase activity, serum oestradiol and their correlation with demographic indices

Peripheral aromatase activity was measured in 24 postmenopausal women suffering from advanced breast cancer. The % conversion of androstenedione to oestrone was then assessed for a significant correlation with age, weight, height, Quetelets index (weight/height², Q.I.) and length of menopause. Serum oestradiol (E₂) levels were measured in 22 of the subjects and compared with the same indices. There was no correlation between E₂ or aromatase activity with the length of menopause (P = 0.3 and P = 0.5, respectively). In our data aromatase activity did not correlate with age (P > 0.5, N = 22). Serum E₂ levels (P = 0.07, N = 20) expressed a negative correlation (i.e. decreased) with age. There was also a poor correlation between aromatase activity and weight of Quetelets index (P = 0.3, N = 20 for both). Serum E₂ levels showed a statistically significant correlation with weight (P = 0.01, N = 21), but the relationship with Quetelets index just failed to attain statistical significance (P = 0.07, N = 20). In both cases the regression line was positive. When aromatase activity was correlated with serum E₂ levels the regression line was positive but not statistically significant (P = 0.4, N = 22). The data indicate that aromatase activity is only one factor determining the differences in serum E₂ levels between postmenopausal women.     

Effect of Molecular Weight and Degree of Acetylation on Adjuvantive Properties of Chitosan Derivatives

The hemostatic and immunostimulating activity and cytotoxicity were determined for a number of chitosans differing in molecular weight (from 3 to 510 kDa) and degree of acetylation (from 1 to 25 mol%) that were used as adjuvants in inactivated poliomyelitic, influenza, and live influenza vaccines. It has been shown that the hemostatic activity of chitosan increased sharply with an increase in its molecular weight. In oligochitosan with a molecular weight of <16 kDa, it was smaller by a factor of 15–100 than in chitosan with a molecular weight of 20–510 kDa. The level of increase in the immunogenicity of vaccines containing oligochitosan as adjuvants was not lower than that for the vaccine including high-molecular chitosan. However, the immunostimulatory activity of oligochitosan depended on the degree of acetylation, reaching a maximum value at 6 mol%. It was shown that all oligochitosans and chitosans with a molecular mass below ~50 kDa showed almost no cytotoxicity at a concentration of ≤2.5 mg/mL, which enable their use as adjuvants for inactivated and live vaccines at the optimal ratio of molecular weight to the degree of acetylation.     

Na2CO3处理对黄瓜嫁接苗与自根苗耐盐性的影响

通过Na2CO3,胁迫对黄瓜嫁接苗和自根苗耐盐性差异的研究,揭示黄瓜幼苗的耐盐机制,为设施黄瓜生产提供理论依据。实验以孝感早瓠瓜为砧木,津春四号黄瓜为接穗,采用不同浓度Na2CO3,溶液对黄瓜嫁接苗和自根苗进行处理,研究其对黄瓜幼苗的生理胁迫效应。结果表明：在0—7000mg／L范围内,随着Na2CO3,处理浓度的增加,黄瓜嫁接苗和自根苗的株高、茎粗、叶面积、地上部鲜重、根鲜重、叶绿素和根系活力均下降,但嫁接苗受抑制的程度显著低于自根苗;脯氨酸、丙二醛和根冠比均呈上升趋势,且这三项指标均表现为嫁接苗显著高于自根苗;叶片SOD酶活性均呈先上升后下降趋势,均在Na2CO3,处理浓度为1000mg／L时达到最大值,且嫁接苗的活性显著高于自根苗。嫁接苗的耐盐性优于自根苗,Na2CO3胁迫条件下,嫁接苗和自根苗的生长条件盐浓度以不超过3000mg／L为宜。     

NADP-dependent dehydrogenases in rat liver parenchyma

Summary Qualitative histochemical G6PDH distribution patterns obtained in the liver acinus of adult male and female rats with an improved method (Rieder et al., 1978) served as a basis for the isolation by microdissection of tissue samples of defined zonal affiliation. G6PDH activity was assayed quantitatively in tissue samples of zones 1 and 3 by a microfluorometric method, using the oil well technique and enzymatic cycling (Burch et al., 1963; Lowry and Passonneau, 1972). With the use of a correlation system further evidence could be presented for the validity of the recently described qualitative distribution patterns. From a total of 50 analyzed tissue samples the following G6PDH activities were calculated: 4.25±1.56 U/g dry weight in zone 1 and 2.08±0.46 U/g dry weight in zone 3 of male and 7.21±1.03 U/g dry weight in zone 1 and 11.10±2.56 U/g dry weight in zone 3 of female rats. These data were corrected for interference from the G6PDH activity of the Kupffer cells within zone 1 samples (approximately 80 U/g dry weight), so that the actual relative values for the parenchymal activity could be estimated for the first time: 2 U/g dry weight in zones 1 and 3 of male animals, 5 U/g dry weight in zone 1 and 11 U/g dry weight in zone 3 of female animals. In female livers G6PDH activity in zone 1 is therefore 2.5 times higher, and in zone 3 5 times higher than in the male. These zonal as well as sex-differences are clearly indicative of a heterogeneous functional organization of the liver acinus in terms of capacity for NADPH production, mainly in connection with reductive reactions in fatty acid synthesis.Supported by a grant from the SFB 46 (Molgrudent)     

Impact of polychlorinated biphenyls on the activity of intestinal proteinases and carbohydrases in juvenile roach Rutilus rutilus (L.)

The chronic effects that polychlorinated biphenyls (PCBs) have on the activities of proteinases and carbohydrates in intestinal mucosa and chyme in juvenile roach Rutilus rutilus (L.) have been studied for the first time. Upon consuming food with PCB 50.8 ng/g wet weight for 218 days, the exposition of fingerlings in aquariums with dirt bottoms (contents PCB 425.6 ng/g dry weight) reduces the proteolytic activity of mucosa to a greater degree than amylolytic activity; the activity of sucrase changes in different directions. In 2-year-old fish receiving PCB only with food (50.8 ng/g wet weight bottom), proteolytic and amylolytic activities of the mucosa are reduced 18 and 35% in comparison with the control (52 days); the sucrose activity is reduced 13% (52 days) and 22% (169 days). In most cases the relation of amylolytic activity to proteolytic activity in fish of the experimental groups is less than in the control. The enzyme activities in chyme change in different directions, depending on the terms and conditions of the experiment.     

Effect of exogenous carnitine on carnitine homeostasis in the rat

The interaction of exogenous carnitine with whole body carnitine homeostasis was characterized in the rat. Carnitine was administered in pharmacologic doses (0-33.3 mumols/100 g body weight) by bolus, intravenous injection, and plasma, urine, liver, skeletal muscle and heart content of carnitine and acylcarnitines quantitated over a 48 h period. Pre-injection urinary carnitine excretion was circadian as excretion rates were increased 2-fold during the lights-off cycle as compared with the lights-on cycle. Following carnitine administration, there was an increase in urinary total carnitine excretion which accounted for approx. 60% of the administered carnitine at doses above 8.3 mumols/100 g body weight. Urinary acylcarnitine excretion was increased following carnitine administration in a dose-dependent fashion. During the 24 h following administration of 16.7 mumols [14C]carnitine/100 g body weight, urinary carnitine specific activity averaged only 72 +/- 4% of the injection solution specific activity. This dilution of the [14C]carnitine specific activity suggests that endogenous carnitine contributed to the increased net urinary carnitine excretion following carnitine administration. 5 min after administration of 16.7 mumol carnitine/100 g body weight approx. 80% of the injected carnitine was in the extracellular fluid compartment and 5% in the liver. Plasma, liver and soleus total carnitine contents were increased 6 h after administration of 16.7 mumols carnitine/100 g body weight. 6 h post-administration, 37% of the dose was recovered in the urine, 12% remained in the extracellular compartment, 9% was in the liver and 22% was distributed in the skeletal muscle. In liver and plasma, short chain acylcarnitine content was increased 5 min and 6 h post injection as compared with controls. Plasma, liver, skeletal muscle and heart carnitine contents were not different from control levels 48 h after carnitine administration. The results demonstrate that single, bolus administration of carnitine is effective in increasing urinary acylcarnitine elimination. While liver carnitine content is doubled for at least 6 h following carnitine administration, skeletal muscle and heart carnitine pools are only modestly perturbed following a single intravenous carnitine dose. The dilution of [14C]carnitine specific activity in the urine of treated animals suggests that tissue-blood carnitine or acylcarnitine exchange systems contribute to overall carnitine homeostasis following carnitine administration.     

Influence of weekend lifestyle patterns on body weight

Objective: To determine whether alterations in diet and/or activity patterns during weekends contribute to weight gain or hinder weight loss. Methods and Procedures: Randomized, controlled trial comparing 1 year of caloric restriction (CR) with 1 year of daily exercise (EX). Subjects included 48 healthy adults (30F, 18M) aged 50–60 years with BMI 23.5–29.9 kg/m². Body weight was measured on 7 consecutive mornings for a total of 165 weeks at baseline and 437 weeks during the 1‐year interventions. Daily weight changes were calculated for weekends (Friday to Monday) and weekdays (Monday to Friday). Daily energy intake was estimated using food diaries; daily physical activity was measured using accelerometers. Both measures were validated against doubly labeled water (DLW). Results: At baseline, participants consistently gained weight on weekend days (+0.06 ± 0.03 kg/day, (mean ± s.e.), P = 0.02), but not on weekdays (?0.02 ± 0.02 kg/day, P = 0.18). This was attributable to higher dietary intake on Saturdays and lower physical activity on Sundays relative to weekdays (both P < 0.05). During the interventions, both CR and EX participants were in negative energy balance on weekdays (P < 0.005). On weekends, however, CR participants stopped losing weight, and EX participants gained weight (+0.08 ± 0.03 kg/day, P < 0.0001) due to higher dietary intakes on weekends. This helps to explain the slower‐than‐expected rate of weight loss during the interventions. Discussion: Alterations in lifestyle behaviors on weekends contribute to weight gain or cessation of weight loss on weekends. These results provide one explanation for the relatively slow rates of weight loss observed in many studies, and the difficulty with maintaining significant weight loss.     

新型抗高血压活性肽GAP-A的一级结构及生理活性研究

研究了新型乳酪蛋白源抗高血压活性肽GAP-A的分子量与一级结构,并检测了其对体外血管紧张素转化酶(ACE)的抑制活性及体内降血压效果。结果显示:抗高血压活性肽GAP-A分子量为M2,氨基酸序列为B1-B2-B3;GAP-A在体外对ACE有很强的抑制活性,抑制率为79.6%;GAP-A对自发性高血压大鼠(spontaneously hypertensive rats,SHR)有显著的降血压作用,而对血压正常的SD大鼠的血压没有影响。     

茄子幼苗耐低温性生理机制研究

选择耐低温性不同的6份茄子高代自交系幼苗为材料,进行白天10℃/夜间7℃低温处理10d,调查其耐低温性、生长指标(株高、茎粗、鲜重、干重)、生理指标(POD、SOD、APX活性及脯氨酸含量),以探讨低温对茄子幼苗生长过程中的生长和生理指标的影响.结果显示:(1)各材料的上述性状在常温下均差异不显著,而在低温处理下差异极显著;与对照相比较,幼苗株高、茎粗、鲜重和干重下降,而POD、SOD、APX活性及脯氨酸含量上升.(2)各材料指标的升降幅度与其低温耐受性密切相关,耐低温性强的材料生长指标下降幅度较小,而生理指标提高幅度较大,耐低温性弱的材料则表现相反.(3)各指标间相比较,茄子耐低温性与株高、茎粗、干重、POD活性、SOD活性呈显著正相关,与其余性状的相关未达显著水平.研究表明,低温使茄子幼苗的生长受到一定程度的抑制,但耐低温材料能够通过调节自身的保护酶系统活性来减轻低温的伤害,维持植物体的正常生长及生理代谢功能.