Phospholipase of rat intestine: mode of action]

Phospholipase activities of rat intestinal mucosa homogenate have been determined from lysophosphatidylcholines [14C] and phosphatidylcholines [-3H-14C]. In the presence of phosphatidylcholines, at pH 6.5, the homogenate has a phospholipase B activity. At pH 8.5, a phospholipase A2 activity was shown. In the presence of lysophospatidylcholines, at pH 6.5, we notice a lysophospholipase A1 activity. A kinetic study of the reactions allows us to separate the activity B into a phospholipase A2 activity and a lysophospholipase A1 activity. Thus, it appears that the total phospholipase activity of rat intestinal mucosa would results from a phospholipase A2 activity and a lysophospholipase A1 activity.     

高温胁迫下两种藓类植物过氧化物酶活性的变化

在不同的高温胁迫条件下 ,对湿地匍灯藓 (Plagiomnium acutum)和大羽藓 (Thuidium cymbifolium)过氧化物酶 (POD)活性及其与处理时间和处理温度的关系进行了初步研究。结果表明 ,在一定的温度范围内 ,随着温度的升高 ,POD活性增加 ,二者成线形关系。在一定温度条件下 ,一般随着处理时间的延长 ,POD活性增加。但是当超过一定的温度 (4 5～ 5 0°C)以及一定的处理时间 (4～ 6h) ,POD活性有所下降。结果还表明 ,湿地匍灯藓的POD活性显著高于大羽藓。而且在高温胁迫下 ,湿地匍灯藓 POD活性变化比大羽藓活跃 ,其变化幅度也比大羽藓大。     

秸秆纤维素分解菌的酶活力测定

目的:测定秸秆纤维素分解菌的酶活力。方法:从土壤中分离出具有分解纤维素能力的菌株,采用刚果红染色法进行粗选,得到7株透明圈较大的菌株。将这7株菌株液体发酵培养6d,再分别用滤纸分解度观察、羧甲基纤维素酶活法(CMC)、滤纸酶活法(FPA)和天然纤维素酶活法测定其酶活力。结果:在7株菌株中,F-1、F-2、F-3、F-5的酶活力测定结果与其溶解圈的测定结果、滤纸分解结果基本相同。且天然纤维素酶活力高的菌株,其CMC酶活、FPA酶活也高,滤纸分解效果也比较明显。结论:CMC法、FPA法和天然纤维素酶活法适于测定秸秆纤维素分解菌的酶活力。     

Changes in activity levels of glutamate dehydrogenase and two transaminases of maternal liver during reproduction and after administration of oestradiol and progesterone in Zoarces viviparus (L.)

The enzyme activity per unit liver wet weight, the specific activity and the total liver activity level of glutamate dehydrogenase (GDH) and two transaminases (GOT and GPT) were studied during vitellogenesis and pregnancy. A steady level of activity was observed during the short summer vitellogenesis and during early pregnancy. During mid-term pregnancy in October the activity level significantly increased.
Administration of 5 and 100 μg oestradiol increased serum vitellogenin, total liver protein and the liver somatic index during late pregnancy. Oestradiol decreased activity and specific activity of the enzymes. However, expressing activity as total hepatic enzyme activity units in fish of standard body weight oestradiol had no effect.     

Effect of Environmental Conditions on Extracellular Protease Activity in Lignolytic Cultures of Phanerochaete chrysosporium

Two different types of extracellular protease activity were identified in the culture fluid of Phanerochaete chrysosporium wild-type BKM-F grown in submerged batch culture on N-limited media. The first activity, which appears to be inherent to the active growth phase, displayed a maximum on day 2 and decreased to a very low level on day 4. The second activity, which appeared at day 8 following the peak of ligninase activity, seems to be characteristic of late secondary metabolism and is stimulated by carbon starvation. Cultures started with half the amount of glucose of other cultures showed a remarkably earlier development of secondary activity. In contrast, the fed-batch addition of glucose started when ligninase activity was at a maximum (day 6) completely repressed secondary protease activity and enhanced ligninase production. The addition of exogenous veratryl alcohol increased the level of secondary protease activity, whereas the oxygen supply pattern significantly affected both the time course and the level of overall proteolytic activity. The addition of phenylmethylsulfonyl fluoride to growing cultures (0, 1, or 6 days) diminished overall protease activity, while it significantly enhanced ligninase activity. In all cases, the time courses of protease and ligninase activities were negatively correlated, indicating that protease activity promotes the decline of ligninase activity in batch culture.     

Characteristics of sperm acrosin-like activity of paddlefish (Polyodon spathula Walbaum)

Spermatozoa of paddlefish and sturgeon fishes (Acipenseriformes), unlike teleost fish, have an acrosome. The objectives of this study were to characterize acrosin-like activity of cryopreserved sperm of paddlefish (Polyodon spathula) and to test and compare stability of paddlefish acrosin-like activity with that of lake sturgeon and bull spermatozoa. Mean acrosin-like activity of cryopreserved paddlefish sperm was 0.372 +/- 0.067 microU/10(6) spermatozoa. This activity was 79% higher in the whole semen than in spermatozoa. Highest activity was recorded at pH 8.0 and 8.5. Triton X-100, zinc ions and 4'-acetamidophenyl 4-guanidinobenzoate (AGB) inhibited the activity. Amidase activity was also inhibited by N-alpha-p-tosyl-L-lysine chloromethyl ketone (TLCK) and N-tosyl-L-phenylalanine chloromethyl ketone (TPCK). TLCK at concentrations of 0.1 and 1.0 mM gave a significant decrease in activity of 19 and 61%, respectively. However, TPCK significantly inhibited amidase activity (by 19%) only at concentration 1.0 mM. After acidification and 60 min incubation at 4 degrees C of sperm suspensions only 4% of the activity was retained. A similar phenomenon was observed in the case of lake sturgeon but not bull sperm. These results suggest that trypsin-like activity of Acipenserid fish resembles rather fish trypsin that mammalian one. In frozen-thawed paddlefish sperm a minute chymotrypsin-like activity was also indicated, when GPNA was used as substrate. This activity amounted to 0.0415 +/- 0.0138 microU/10(6) spermatozoa and was 18% of total amidase activity. This suggests that chymotrypsin-like activity may also be present in paddlefish spermatozoa.     

Ontogeny of cyclic AMP-dependent protein phosphokinase during hepatic development of the rat.

The ontogeny of protein kinase (ATP: protein phosphotransferase, EC 2.7.1.37) and cyclic AMP-binding activity in subcellular fractions of liver was examined during prenatal and postnatal development of the male rat. 1. Protein kinase activity and cyclic AMP-binding activity were found in the nuclear, microsomal, lysosomal-mitochondrial, and soluble liver fractions. 2. The protein kinase activity of the soluble (105 000 X g supernatant) fraction measured with histone F1 as substrate was stimulated by cyclic AMP. Cyclic AMP did not stimulate the protein kinase activity of the particulate fractions. 3. The protein kinase activity of all subcellular fractions increased rapidly from the activity observed in prenatal liver (3-4 days before birth) to reach maximal activity in 2-day-old rats. Thereafter, the protein kinase activity declined more slowly and regained the prenatal levels at 10 days after birth. 4. Considerable latent protein kinase activity was associated with liver microsomal fractions which could be activated by treatment of microsomes with Triton X-100. The latent microsomal protein kinase activity was highest in prenatal liver, at the time of birth, and 2 days after birth. During the subsequent postnatal development the latent microsomal protein kinase activity gradually declined to insignificantly low levels. 5. During the developmental period examined (4 days before birth to age 60-90 days) marked alterations of the cyclic AMP-binding activity were determined in all subcellular fractions of rat liver. In general, cytosol, microsomal, and lysosomal-mitochondrial cyclic AMP-binding activity was highest in 10-11 day-old rats. Nuclear cyclic AMP-binding activity was highest 3-4 days before birth and declined at birth and during the postnatal period. There was no correlation between the developmental alteration of cyclic AMP-binding activity and cyclic AMP dependency of the protein kinase activity in any of the subcellular fractions. This suggests that the measured cyclic AMP-binding activity does not reflect developmental alterations of the cyclic AMP-binding regulatory subunit of cyclic AMP-dependent protein kinase.     

Correlation of immunomodulatory and therapeutic activities of interferon and interferon inducers in metastatic disease

The mechanism of therapeutic activity of recombinant murine interferon-gamma (rMu IFN-gamma) and the IFN inducer polyinosinic-polycytidylic acid solubilized with poly-L-lysine in carboxy methyl cellulose (pICLC) in treating metastatic disease was investigated by comparing effector cell augmentation with therapeutic activity in mice bearing experimental lung metastases (B16-BL6 melanoma). Effector cell functions in spleen, peripheral blood, and lung (the organ with tumor) were tested after 1 and 3 weeks of rMu IFN-gamma or pICLC administration (intravenous, three times a week). In these studies, natural killer (NK), lymphokine-activated killer (LAK), cytolytic T lymphocytes (CTL) (against specific and nonspecific targets), and macrophage tumoricidal and tumoristatic activities were measured. rM IFN-gamma and pICLC had therapeutic activity and immunomodulatory activity in most assays of immune function examined. Specific CTL activity of pulmonary parenchymal mononuclear cells (PPMC), but not in splenocytes or peripheral blood lymphocytes (PBL), during week 3 and not during week 1, correlated with the therapeutic activity of rMu IFN-gamma and of pICLC. Macrophage tumoricidal activity in PPMC, but not in alveolar macrophages, also correlated with the therapeutic activity of rMu IFN-gamma, but the opposite was true for the therapeutic activity of pICLC. NK activity of PPMC, but not of splenocytes or PBL, during week 1 correlated with the therapeutic activity of pICLC; in contrast, NK activity at any site did not correlate with the therapeutic activity of rMu IFN-gamma. LAK activity at any site did not correlate with the therapeutic activity of either agent.     

Electroencephalographic study of the effect of neurotoxin DSP-4 in iron model of chronic focal epilepsy.

The effect of the noradrenergic neurotoxin N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4) on electroencephalographic activity (EEG) was studied in the model of chronic focal epilepsy induced by intracortical injection of FeCl3 in the rat. EEG activity was recorded from the epileptogenic focus (ipsilateral and contralateral) in chronic experiments before and after DSP-4 treatment. In some experiments EEG activity was also simultaneously recorded from the cortical epileptogenic focus and locus coeruleus before and after DSP-4 treatment to study the effect of iron-induced seizure activity and of DSP-4 on the locus coeruleus electrical activity. The results showed that DSP-4 aggravated the iron-induced epileptiform activity as well as the locus-coeruleus electrical activity. The data also showed that, induction of epilepsy by FeCl3 is accompanied by enhancement of the locus coeruleus electrical activity. Our study demonstrates that DSP-4 intensifies and modifies the epileptic activity in the iron-induced chronic epilepsy model and that the effects of toxin persist for a longer duration.     

Neuroregulation of nonexercise activity thermogenesis and obesity resistance

High levels of spontaneous physical activity in lean people and the nonexercise activity thermogenesis (NEAT) derived from that activity appear to protect lean people from obesity during caloric challenge, while obesity in humans is characterized by dramatically reduced spontaneous physical activity. We have similarly demonstrated that obesity-resistant rats have significantly greater spontaneous physical activity than obesity-prone rats, and that spontaneous physical activity predicts body weight gain. Although the energetic cost of activity varies between types of activity and may be regulated, individual level of spontaneous physical activity is important in determining propensity for obesity. We review the current status of knowledge about the brain mechanisms involved in controlling the level of spontaneous physical activity and the NEAT so generated. Focus is on potential neural mediators of spontaneous physical activity and NEAT, including orexin A (also known as hypocretin 1), agouti-related protein, ghrelin, and neuromedin U, in addition to brief mention of neuropeptide Y, corticotrophin releasing hormone, cholecystokinin, estrogen, leptin, and dopamine effects on spontaneous physical activity. We further review evidence that strain differences in orexin stimulation pathways for spontaneous physical activity and NEAT appear to track with the body weight phenotype, thus providing a potential mechanistic explanation for reduced activity and weight gain.     

Correlates of life course physical activity in participants of the Baltimore longitudinal study of aging

Physical activity is consistently associated with better health and longer life spans. However, the extent to which length and intensity of exercise across the life course impact health outcomes relative to current activity is undefined. Participants of the Baltimore Longitudinal Study of Aging were asked to categorize their level of physical activity in each decade of life from adolescence to the current decade. In linear mixed effects models, self-reported past levels of physical activity were significantly associated with activity assessed at study visits in the corresponding decade of life either by questionnaire or accelerometry. A pattern of life course physical activity (LCPA) derived by ranking participants on reported activity intensity across multiple decades was consistent with the trajectories of activity estimated from standard physical activity questionnaires assessed at prior study visits. In multivariable linear regression models LCPA was associated with clinical characteristics, measures of body composition and indicators of physical performance independent of current physical activity. After adjustment for minutes of high intensity exercise, LCPA remained significantly associated with peak VO₂, fasting glucose, thigh muscle area and density, abdominal subcutaneous fat, usual gait speed, lower extremity performance, and multimorbidity (all p < 0.01) at the index visit. The observed associations suggest that an estimate of physical activity across decades provides complementary information to information on current activity and reemphasizes the importance of consistently engaging in physical activity over the life course.     

Clearing-factor lipase in adipose tissue. Distinction of different states of the enzyme and the possible role of the fat cell in the maintenance of tissue activity

1. Incubation of intact epididymal adipose tissue from fed rats at 37 degrees in an albumin solution at pH7.4 in vitro results in rapid loss of clearing-factor lipase activity until a low activity, stable to prolonged incubation, is attained. The clearing-factor lipase activity of intact tissue from starved rats, which is initially much less than that of tissue from fed rats, is mainly stable to incubation at 37 degrees . 2. Much of the clearing-factor lipase activity of intact epididymal adipose tissue from fed rats is inactivated by collagenase. The enzyme activity of intact tissue from starved rats is not inactivated by collagenase. 3. The clearing-factor lipase activity of fat cells isolated from the epididymal adipose tissue of fed rats is stable to prolonged incubation at 37 degrees . It represents only a small proportion of the total activity of the intact tissue. In starved rats, the isolated fat cells contain a much higher proportion of the activity of the intact tissue. Their activity is also stable at 37 degrees . 4. Incubation of isolated fat cells in a serum-based medium leads to a progressive rise in clearing-factor lipase activity. Actinomycin increases the extent of this rise in activity. No rise in clearing-factor lipase activity occurs when stromal-vascular cells isolated from epididymal adipose tissue are incubated in the medium. 5. The findings indicate that less than 20% of the activity of intact adipose tissue from fed rats is retained when fat cells are isolated from the tissue by collagenase treatment. The activity that is lost could be that which normally functions in the uptake of triglyceride fatty acids by the tissue.     

Identification of a deoxyribonuclease activity in the nuclei of the cervical carcinoma HeLa

A deoxyribonuclease activity has been identified in the nuclei of the human cervical carcinoma HeLa. This activity has the novel property of existing as a single strand specific endo- and exodeoxyribonuclease activity. These activities are ionic strength sensitive, with retardation of activity occurring at 50 mM NaCl and above, with the Mn++ ion preferred over the Mg++ ion as activating cation. This activity extensively damages DNA via its single strand nicking and gaping activity. The method used to solubilize this activity as well as the enzyme's characteristics are discussed.     

Separation of soluble amoebicidal and tumoricidal activity of activated macrophages.

Macrophage-conditioned medium (M phi CM) prepared from mouse peritoneal macrophages activated in vivo with bacillus Calmette-Guérin (BCG) or Propionibacterium acnes and triggered with lipopolysaccharide in vitro contained tumoricidal and amoebicidal activity. The murine fibroblast cell line L929 was used as the indicator of tumoricidal activity and Naegleria fowleri amoeba was used to detect amoebicidal activity in M phi CM. The protease inhibitor, soybean trypsin inhibitor, decreased tumoricidal activity but had little effect on amoebicidal activity in M phi CM. Anti-TNF alpha antiserum inhibited tumoricidal activity in M phi CM. The antiserum reduced amoebicidal activity in BCG-activated M phi CM but had no effect on amoebicidal activity in P. acnes-activated M phi CM. Recombinant TNF alpha, rIL-1 alpha, or rIL-1 beta independently did not affect cytolysis of amoebae. Also, rTNF alpha had no effect on the growth of amoebae. Preparative flat-bed electrofocusing of BCG-activated M phi CM yielded fractions that exhibited different amoebicidal and tumoricidal activity profiles. Three domains of activity were analyzed (acidic, neutral, and basic). Anti-TNF alpha antiserum eliminated tumoricidal activity, but not amoebicidal activity, in fractions from the acidic domain. A combination of anti-TNF alpha and anti-IL-1 alpha antisera failed to eliminate amoebicidal activity in fractions from the basic domain. These results indicate that different factors are responsible for macrophage amoebicidal and tumoricidal activity. The amoebicidal factors in M phi CM affected cytolysis of several species of amoebae.     

Characterization of calmodulin-activated protein kinase activity of rat adipocyte endoplasmic reticulum fraction

Calmodulin-activated protein kinase activity in the endoplasmic reticulum fraction of rat adipocytes was identified and characterized. The major endogenous protein substrate of the calmodulin-activated kinase activity has an apparent molecular weight of 54,000 as determined by sodium dodecyl sulfate gel electrophoresis. The calmodulin-activated component of the activity was saturated at 10 microM ATP. Calcium or calmodulin alone did not increase the activity, but the simultaneous presence of calcium and calmodulin increased activity three to four-fold. Half-maximal activation of this activity occurred at 8 microM Ca2+. The addition of increasing amounts of calmodulin caused a concentration-dependent activation in the presence of calcium, which was saturable at high calmodulin concentrations. Magnesium was required for activity, with half-maximal activity occurring at 230 microM. The antipsychotic drug trifluoperazine inhibited the activation of the protein kinase activity by calmodulin, but had a negligible effect on the basal activity. Half-maximal inhibition occurred at 63 microM. Phosphorylation of the 54,000 mol. wt band was independent of cAMP, cGMP and the combination of cAMP and cAMP-dependent protein kinase. Calmodulin-activated protein kinase phosphorylated both phosphoserine and phosphothreonine residues in the 54,000 mol. wt substrate. These experiments have partially characterized a calmodulin-activated protein kinase activity from adipocytes, which appears to be a unique activity of unknown function.     

Daily activity profiles over the lifespan of female medflies as biomarkers of aging and longevity

The relationship between the early-age activity of Mediterranean fruit flies (medflies) or other fruit flies and their lifespan has not been much studied, in contrast to the connections between lifespan and diet, sexual signaling, and reproduction. The objective of this study is to assess intra-day and day-to-day activity profiles of female Mediterranean fruit flies and their role as biomarker of longevity as well as to explore the relationships between these activity profiles, diet, and age-at-death throughout the lifespan. We use advanced statistical methods from functional data analysis (FDA). Three distinct patterns of activity variations in early-age activity profiles can be distinguished. A low-caloric diet is associated with a delayed activity peak, while a high-caloric diet is linked with an earlier activity peak. We find that age-at-death of individual medflies is connected to their activity profiles in early life. An increased risk of mortality is associated with increased activity in early age, as well as with a higher contrast between daytime and nighttime activity. Conversely, medflies are more likely to have a longer lifespan when they are fed a medium-caloric diet and when their daily activity is more evenly distributed across the early-age span and between daytime and nighttime. The before-death activity profile of medflies displays two characteristic before-death patterns, where one pattern is characterized by slowly declining daily activity and the other by a sudden decline in activity that is followed by death.     

A kinetic description of antifreeze glycoprotein activity

The antifreeze glycoproteins (AFGP) of polar fish have the ability to depress the freezing temperature of water approximately 500 times the amount expected based on the number of AFGP molecules in solution; yet AFGP solutions have a purely colligative melting point depression. The difference of solution melting and freezing temperatures is the antifreeze activity of AFGP. One characteristic of AFGP activity that requires further examination is the effect of concentration on antifreeze activity, especially whether the activity saturates at high concentrations or the measured activity increases ad infinitum. This study first surveys the activity of the various antifreeze components from both Pagothenia borchgrevinki and the Arg-containing antifreeze glycoprotein from Eleginus gracilis (EgAF). It was found that all AFGP components examined have a plateau in activity at high concentration, but the actual value of the plateau activity differs between the different length AFGP components and between AFGP and EgAF. While the low molecular weight components of both AFGP and EgAF lose activity at deep supercooling, at high concentration activity is restored. The activity data is then shown to fit a reversible kinetic model of AFGP activity, and the coefficients obtained are used to compare the activity differences between AFGP components and between AFGP and EgAF. The model is also shown to describe the activity of the antifreeze protein of the fish Pseudopleuronectes americanus and the thermal hysteresis protein of the insect, Tenebrio molitor.     

The effect of progesterone on the activity-wheel running of ovariectomized rats

Progesterone treatment failed to significantly depress activity-wheel activity elicited by food deprivation in either ovariectomized or ovariectomized estrogen-treated rats. These results indicate: (1) that the lack of effect of progesterone on the activity of ovariectomized rats is not due only to their already low level of activity; and (2) that the depressant effect of progesterone on activity in the estrogen-treated ovariectomized rat is, to a large extent, a specific inhibition of estrogen facilitation of activity, rather than a nonspecific activity depressant effect.     

生物絮凝剂絮凝活性评价方法的探讨

对生物絮凝剂絮凝活性的评价方法进行了探讨。研究发现,在固定絮凝剂添加量的情况下仅仅比较絮凝率大小,从而对絮凝活性进行评价的方法是不科学的。絮凝剂絮凝活性应以絮凝率和絮凝剂最适添加量两个指标为其活性评价参数,在有较高絮凝率的情况下,絮凝剂添加量越少则絮凝活性越高。     

Phospholipid-enzyme interactions of chitin synthase of Coprinus cinereus

Abstract The effect of phospholipids on chitin synthase activity has been studied with digitonin-solubilized and partially purified preparations from Coprinus cinereus . When cholate was used as detergent, it inhibited enzyme activity, but this inhibition was reversed by increasing concentrations of phospholipids. Preincubation with cholate and phospholipid caused irreversible loss of activity. When sonicated with solubilized enzyme preparation, dimyristoyl phosphatidyl choline strongly stimulated activity, while dioleoyl phosphatidyl choline was inhibitory. The Arrhenius plot of the effect of temperature on enzyme activity contained breaks, characteristic of a membrane-bound enzyme. It is suggested that chitin synthase requires an annulus of phospholipids for activity.