Insulin and fructose regulate malic enzyme activity by different processes

A comparison of the regulatory processes controlling hepatic malic enzyme activity following treatment of diabetic rats with insulin or with a high fructose diet demonstrated several important differences. Insulin treatment caused a 50-fold increase in activity, due to a 12-fold increase in enzyme quantity and a 4-fold increase in specific activity(units/nmol). Dietary fructose caused a 3-fold increase in enzyme activity, due to a 3-fold increase in enzyme quantity, with no change in the specific activity of the enzyme. Thus, while fructose initiated a minor increase in malic enzyme activity, insulin was more effective, causing a substantially greater increase in enzyme activity and activating a hormone specific alteration in the catalytic activity of each enzyme molecule.     

Purine nucleoside phosphorylase (NP) of bovine erythrocytes: genetic control of electrophoretic variants

A genetic polymorphism of the purine nucleoside phosphorylase is described in red cells of cattle. Electrophoresis distinguishes two types, one associated with a high activity (H), the other with a low activity (L). Breeding tests suggest the segregation of two alleles: a dominant allele for high activity ( H ) and a recessive allele for low activity (L). On the basis of quantitative estimation of enzyme activity, the individuals of the H phenotype can be separated in two classes, the enzyme activity in one class being twice as high as the activity in the other class. It is suggested that the class with the highest enzymatic activity corresponds to the homozygote for the H allele, the other class to the heterozygote. In fact, an A.I. bull (H phenotype and with the highest enzymatic activity) mated with cows of the L phenotype, gave offspring of the H phenotype, only. The decline of activity, with age, is stressed. Four breeds have been typed. The Charolais breed is characterized by a high frequency of the H allele.     

钩虾胆碱酯酶（ChE）和谷胱甘肽转硫酶（GST）的敏感性和特异性比较研究

研究了有机磷农药甲地基嘧啶流磷,有机氯农药林丹,菊酯类农药氯菊酯,表面活性剂直链苯磺酸钠和重金属Zn对钩虾（Gammarus pulex L.)胆碱酯酶（ChE）和谷胱甘肽转硫酶（GST）活性变化以及毒性影响,结果表明,在暴露24h和48h后,仅有机磷农药甲基嘧硫磷显著抑制胆碱酯的酶的活性,在暴露48h后,有机氯农药林丹和菊酯类农药氯菊酯能显著提高谷胱甘肽转硫酶活性,在暴露24h后,仅梵在导致谷胱甘肽转硫酶明显升高,作为生物标志物,胆碱酯酶比谷胱甘肽转硫酶具有更高的特异性,这两种生物标志物较毒性试验方法具有更高的敏感性。     

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.     

21科41种(变种)植物叶片几丁质酶系的研究

对广州地区常见的21科41种（变种）植物叶片几丁质酶系研究的结果表明,所有受试植物都具有几丁质酶活性。几丁质酶不仅存在于被子植物的双子叶植物和单子叶植物中,而且也存在于裸子植物及蕨类植物中。几丁质酶活性及比活性均较高的有蕹菜、葱、蕨类植物、蒜、茄科植物、玉米、菜豆、番木瓜等。植物一般都具有两种几丁质酶:外切酶和内切酶。几丁质外切酶活性及比活性均较高的有蕨类植物、葱、茄科植物等。几丁质内切酶活性及比活性均较高的有蕹菜、裸子植物等。不同植物几丁质外切酶与内切酶的比例相差较大。有些植物的几丁质酶系以外切酶为主,如茄科植物、大部分豆科植物、番木瓜等;有些植物以内切酶为主,如裸子植物、伞形科植物、蕹菜等;有些植物的外切酶与内切酶含量相差不大。     

Inheritance of low erythrocyte catechol-o-methyltransferase activity in man.

Catechol-O-methyltransferase activity was measured in blood obtained from 373 randomly selected subjects aged 16-18, 262 consecutive adult blood donors, and 201 first-degree relatives of subjects with RBC COMT activity of less than 8 U. The distribution of RBC COMT activity in a randoly selected populations was apparently bimodal with a nadir at approximately 8 U. Of a randomly selected population, 23% had low RBC COMT activity (less than 8 U), Because of previous reports of a significant sibling-sibling correlation of RBC COMT activity and because of the presence of a subgroup of subjects with low enzyme activity, RBC COMT activity was measured in blood from first-degree relatives of probands with low erythrocyte enzyme activity in 48 families. The results of segregation analyses of the data were compatible with autosomal recessive inheritence of an allele for low RBC COMT activity. RBC COMT in blood samples from siblings of probands inthese families also showed an apparent biomodal distribution.     

Deletion of antigen-specific activity from leukocyte dialysates containing transfer factor by antigen-coated polystyrene

We have reported finding antigen-specific activity in human leukocyte dialysates (DLE) containing TF in the leukocyte migration inhibition (LMI) assay. To analyze this activity further, we have used polystyrene bound to antibody or to antigen as immunoadsorbent for DLE before pulsing nonimmune cells in the LMI assay. Candida-(CAN) immune or diphtheria toxoid-(TOX) immune DLE were depleted of all antigen-specific activity after absorption with specific antigen but not affected by absorption with specific antibody, respectively, and depletion of activity with antigen was abrogated by coating bound antigen with specific antibody before absorption of DLE. CAN-immune, TOX-immune DLE was selectively depleted for either CAN activity or TOX activity after absorption with CAN- or TOX-coated polystryrene, respectively, retaining its CAN-activity when absorbed with TOX and conversely retaining its TOX activity when absorbed with CAN; thus the antigen-specific activity binds to related but not unrelated antigen. The polystyrene-bound antigen-specific activity could be recovered by treatment with 8 M urea. We interpret these findings to suggest that such antigen-specific activity may be either a dialysable fragment of a T cell antigen receptor site, or a portion of the V-region, or a unique Ir gene product that assists in antigen presentation to other T cells.     

Locomotor activity of atlantic salmon parr (Salmo salar L.) in various light conditions and in weak magnetic fields

Locomotor activity studies in the laboratory under artificial light cycles co-ordinated with times of sunrise and sunset demonstrated that ten of sixteen Atlantic salmon parr were nocturnal, with an approximately twenty-four hour periodicity. The remaining six fish exhibited diurnal activity patterns or activity mainly after times of light change. Two fish immediately shifted their activity patterns to co-ordinate with a 6-hr shifted light cycle. Six fish retained no activity patterns in constant light, and only two of eleven fish had weak activity patterns in constant darkness. Results suggest that Atlantic salmon parr are dependent on a light-dark cycle for timing their activity rhythms. Three of twelve salmon in an imposed magnetic field four times the strength of the horizontal vector of the ambient field, increased their activity level and changed activity patterns in the increased field. The remaining fish showed no distinct change in locomotor activity.     

Urinary excretion of LATS in a patient with Graves' disease complicated by nephrotic syndrome

A case report of a female patient with Graves' disease complicated by nephrotic syndrome with high LATS activity in urinary gamma-globulin is presented. When in the hyperthyroid state with high LATS activity in the serum, she was treated with antithyroid drugs, excess iodine, and finally radioisotopes. Mild hypothyroidism occurred transiently without any significant change in serum LATS activity. Nephrotic syndrome suddenly appeared. Urinary IgG was purified by salting out with ammonium sulfate, DEAE and protein A-Sepharose, and LATS activity in the purified urinary IgG fraction was demonstrated. The specific activity of LATS activity in urinary IgG protein was slightly lower than that of the serum. This case is the first demonstration of LATS activity in urine from a patient with hyperthyroidism and nephrotic syndrome.     

The effect of sex hormones on the acinar distribution pattern of phosphoenolpyruvate carboxykinase activity in rat liver

The intra-acinar distribution pattern of phosphoenolpyruvate carboxykinase activity (PEPCK) was investigated in microdissected samples of livers from normal, castrated, castrated and estradiol- or testosterone-treated, and uncastrated and testosterone- or estradiol-treated male and female rats. The total PEPCK activity showed a marked sex dependency, with 1.8 times higher activity in males. The intra-acinar distribution profiles were also sex-dependent. The periportal-to-perivenous gradient was steeper in males. Castration resulted in an approximation of PEPCK activity and its acinar distribution pattern between the sexes due to a reduction in males and an increase in females. Estrogen treatment of castrated males had no further effect on PEPCK activity and its acinar gradient, whereas in ovariectomized animals the activity was reduced to levels near normal. Testosterone treatment of castrated male or female animals led to a marked increase in enzyme activity with a concomitant steepening of the acinar gradient. Administration of estradiol to normal male rats also led to a reduction in activity, together with a change in the acinar activity gradient. Testosterone treatment of normal females resulted in an induction of PEPCK activity which was most prominent in the periportal zone. The most drastic changes were observed in the perivenous zones. In all experiments a periportal-to-perivenous activity gradient persisted thus marking the periportal zone as the area with highest gluconeogenic capacity.     

Biochemistry and physiology of monoamine oxidase (MAO) activity in the ring dove (Streptopelia risoria). I. Characteristics of MAO activity in vitro

Monoamine oxidase (MAO) activity was measured in ring dove (Streptopelia risoria) tissues using a fluorometric assay with kynuramine as substrate. Harmaline inhibited MAO activity in a time-dependent manner, and preincubation of enzyme with the drug did not affect its activity. Pargyline produced a slow-onsetting inhibition of activity which was enhanced by preincubation of enzyme and inhibitor. Harmaline displayed reversible non-competitive inhibition of MAO activity. Oxygen is also a substrate for dove MAO, and the reaction apparently involves "ping-pong", double-displacement kinetics. Dove MAO activity is temperature-dependent, with an activation energy of 13.1 kcal/mole.     

Fluoride-dependent calcium-induced platelet procoagulant activity shows that calpain is involved in increased phospholipid transbilayer movement

Treatment of platelets with fluoride (10 mM) was found to result in a transient increase in Ca2+-permeability of the platelet plasma membrane. This phenomenon was used to provide supplementary evidence for the suggestions made earlier (Comfurius et al. (1985) Biochim. Biophys. Acta 815, 143; Verhallen et al. (1987) Biochim. Biophys. Acta 903, 206), that cytoskeletal disrupture by calpain is involved in the process leading to transbilayer movement of phosphatidylserine during expression of platelet procoagulant activity. This was achieved by relating both calpain activity and exposure of phosphatidylserine with platelet procoagulant activity. It was found that only upon addition of extracellular Ca2+ to fluoride-treated platelets, procoagulant activity, expressed as prothrombinase activity, and calpain activity, estimated from protein patterns after gel electrophoresis, were generated. Both Ca2+-inducible prothrombinase activity and calpain activity followed an identical time-course during incubation with fluoride: after a time-lag of about 10 min they sharply increased towards a peak level. Upon further incubation with fluoride, both activities decreased towards a final plateau, still above basal level. The presence of leupeptin during incubation with fluoride was found to inhibit Ca2+-inducible calpain activity and prothrombinase activity in an identical way. Ca2+-inducible exposure of phosphatidylserine, as determined with extracellular phospholipase A2, showed a similar pattern as Ca2+-inducible calpain activity and prothrombinase activity. From the strict parallelism between prothrombinase activity, calpain activity and exposure of phosphatidylserine, it is concluded that calpain plays an important role in the activation-dependent transbilayer movement of phosphatidylserine during expression of platelet procoagulant activity. It is suggested that degradation of the platelet membrane-skeleton by calpain disturbs the structural organization of the lipid bilayer of the platelet plasma membrane leading to enhanced transbilayer movement of phospholipids and appearance of phosphatidylserine at the platelet outer surface.     

The inhibition of peroxidase and indole-3-acetic acid oxidase activity by British Anti-Lewisite

British Anti-Lewisite (BAL) binds to horseradish peroxidase in a manner which results in inhibition of both peroxidatic and oxidative functions of the enzyme. BAL competes with hydrogen peroxide for binding on peroxidase, and the inhibition of peroxidatic activity is irreversible. Solutions of purified horseradish peroxidase and individually resolved peroxidase isozymes show a gradual loss of peroxidatic activity with time when incubated with BAL. In these same treatments, however, the inhibition of indole-3-acetic acid (IAA) oxidase activity is immediate. With increasing amounts of enzyme in the incubation mixture, IAA oxidase activity is not completely inhibited and is observed following a lag period in the assay which shortens with longer incubation times. Peroxidase activity during this same time interval shows a lag period which increases with longer incubation times. Lowering the pH removed the lag period for oxidase activity, but did not change the pattern of peroxidase activity. These results suggest that the sites for the oxidation of indole-3-acetic acid and for peroxidatic activity may not be identical in horseradish peroxidase isozymes.     

Angiotensin carboxypeptidase activity in urine from normal subjects and patients with kidney damage

Angiotensin carboxypeptidase (ACP) activity has been detected in urine samples from normal subjects and patients with hypertension and diabetes by determining the enzyme's ability to convert angiotensin I to des-Leu angiotensin I. Gel filtration chromatography of a concentrated urine sample indicated that about equal amounts of the enzyme exist as 100 kDa and 500 kDa molecular weight forms, respectively. This ACP activity co-eluted with activity that cleaved histidine from des-Leu angiotensin I to form angiotensin II and activity that cleaved tyrosine from benzyloxycarbonyl-glutamyl-tyrosine (ZGT). These results suggest that the urinary ACP activity is due to cathepsin A as we have reported previously for the porcine kidney enzyme. Analysis of sequential urine samples from a single individual over a 6-day period revealed as much as a 6-fold fluctuation in creatinine-normalized ACP activity. Of five male healthy adult subjects, the creatinine-normalized urinary ACP activity ranged from 1.7 to 3.7 mU/mL with a mean of 2.8 mU/mL. However, five male patients with renovascular hypertension had elevated levels of ACP activity with a mean of 11.6 mU/mL. Of five male patients with diabetic nephropathy, all had elevated ACP activity levels with a mean of 21.0 mU/mL. It is concluded that ACP activity in the urine is due to cathepsin A probably derived from kidney tissue, and that the release is increased in patients with kidney damage. We suggest that urinary ACP activity should be evaluated further for a possible relationship to renal hypertension and as a potentially early marker for diabetic nephropathy.     

Inheritance of very low serum dopamine-beta-hydroxylase activity.

Serum dopamine-beta-hydroxylas (DBH) activity was measured in blood samples obtained from 841 children ages 6-12, 277 adults subjects, and 114 relatives of children with serum DBH activity of less than 50 units. Approximately 4% of the children and 3% of the adult subjects tested had very low sweum DBH activity (50 units or less). Because these subjects appeared to make up a separate subgroup within the population and because of a striking familial aggregation of subjects with very low enzyme activity, serum DBH activity was measured in blood obtained from members of 22 families of probands with very low serum enzyme activity. The results of sibship and pedigree analyses of the data were compatible with autosomal recessive inheritance of very low serum DBH activity. Unaffected parents of probands had serum DBH activity intermediate between that found in affected individuals and in control population. No significant correlation of serum DBH activity with either systolic or diastolic blood pressure was found in this randomly selected population of children.     

Heparin treatment of vascular smooth muscle cells results in the synthesis of the dual‐specificity phosphatase MKP‐1

The ability of heparin to block proliferation of vascular smooth muscle cells has been well documented. It is clear that heparin treatment can decrease the level of ERK activity in vascular smooth muscle cells that are sensitive to heparin. In this study, the mechanism by which heparin induces decreases in ERK activity was investigated by evaluating the dual specificity phosphatase, MKP‐1, in heparin treated cells. Heparin induced MKP‐1 synthesis in a time and concentration dependent manner. The time‐course of MKP‐1 expression correlated with the decrease in ERK activity. Over the same time frame, heparin treatment did not result in decreases in MEK‐1 activity which could have, along with constitutive phosphatase activity, accounted for the decrease in ERK activity. Antibodies against a heparin receptor also induced the synthesis of MKP‐1 along with decreasing ERK activity. Blocking either phosphatase activity or synthesis also blocked heparin‐induced decreases in ERK activity. Consistent with a role for MKP‐1, a nuclear phosphatase, heparin treated cells exhibited decreases in nuclear ERK activity more rapidly than cells not treated with heparin. The data support MKP‐1 as a heparin‐induced phosphatase that dephosphorylates ERK, decreasing ERK activity, in vascular smooth muscle cells. J. Cell. Biochem. 110: 382–391, 2010. © 2010 Wiley‐Liss, Inc.     

Size scaling of whole‐body metabolic activity in the noble crayfish (Astacus astacus) estimated from measurements on a single leg

1. Use of electron transport system (ETS) activity in a single leg for estimating whole‐body ETS activity was explored in the noble crayfish Astacus astacus. Oxygen consumption and ETS activity of the whole body and of a walking leg were measured in different‐sized animals at 10 °C to compare the size scaling of oxygen consumption, whole‐body ETS activity and the ratio of whole‐body ETS activity to oxygen consumption (ETS/R). 2. Electron transport system activity of a leg and the ratio of ETS activity of a whole crayfish to that of a leg were correlated with wet mass of animals. Therefore, metabolic potential in whole noble crayfish can be estimated on the basis of the measured ETS activity in a single leg and crayfish mass. This approach provides a valuable tool for determining metabolic characteristics of crayfish without killing them. 3. Mass‐specific oxygen consumption decreased with increasing wet mass, while ETS activity of whole crayfish showed no significant correlation with wet mass. Both oxygen consumption and ETS activity correlated significantly with protein mass. 4. The increase in ETS/R with increasing wet mass of the noble crayfish indicates that small organisms exploit a greater proportion of their metabolic potential for standard metabolism than larger ones. This is the first report on ETS/R in crayfish.     

New evidence for ATP binding induced catalytic subunit interactions in pig kidney Na/K-ATPase

Pig kidney Na/K-ATPase preparations showed a positive cooperative effect for pNPP in Na-pNPPase activity. Measurements of the Na-pNPPase activity, Na-ATPase activity and the accumulation of phosphoenzyme (EP) under conditions of pNPP saturation showed several different ATP affinities. The presence of pNPP reduced both the maximum amount of EP and Na-ATPase activity to half showing a value of 4 and a 3,700-fold reduced ATP affinity for EP formation, and a 7 and 1,300-fold reduced affinity for Na-ATPase activity. The presence of low concentrations of ATP in the phosphorylation induced a 2-fold enhancement in Na-pNPPase activity despite a reduction in available pNPP sites. However, higher concentrations of ATP inhibited the Na-pNPPase activity and a much higher concentration of ATP increased both the phosphorylation and Na-ATPase activity to the maximum levels. The maximum Na-pNPPase activity was 1.7 and 3.4-fold higher without and with ATP, respectively, than the maximum Na-ATPase activity. These data and the pNPP dependent reduction in both Na-ATPase activity and the amount of enzyme bound ATP provide new evidence to show that ATP, pNPP and ATP with pNPP, respectively, induce different subunit interactions resulting a difference in the maximum Na(+)-dependent catalytic activity in tetraprotomeric Na/K-ATPase.     

Enzymic hydrolysis of myelin basic protein and other proteins in central nervous system and lymphoid tissues from normal and demyelinating rats.

Proteolytic activity of central-nervous-system tissue of the normal rat was examined over the pH range 2-9 with casein, haemoglobin and myelin basic protein as substrates. With casein as a substrate, brain and spinal cord homogenates showed very similar activity profiles with increasing pH, with the main peaks of proteolytic activity at pH 3-4 and 5-6. When haemoglobin was used, one broad main peak of activity from pH 3 to 5 was demonstrated. There was no optimum pH, however, for proteolytic activity with myelin basic protein as a substrate, and considerable hydrolysis were observed from pH 3.5 up to pH8. Proteolytic activity at the various pH values was compared by using homogenates of spinal cords from rats with acute experimental allergic encephalomyelitis and those from rats injected with Freund's adjuvant alone. The profiles of activity were similar with peaks at pH 3.5 and 5.5 with casein as a substrate, but the specific activity was significantly higher at most pH values in the spinal-cord homogenates from rats with experimental allergic encephalomyelitis. Similarly the spinal-cord homogenates from these latter rats contained much more proteolytic activity toward myelin basic protein throughout the pH range than was present in the control spinal cords. Homogenates from lymph nodes of rats with experimental allergic encephalomyelitis and from those of the controls contained two to three times as much proteolytic activity as that of the central-nervous-system tissue and had a different proteolytic activity profile form that of the central-nervous system, with higher activity at the neutral than at acid pH. The results are discussed with regard to the probability that inflammatory cells such as lymphocytes may be the cause of the increased proteolytic activity in the central nervous system of animals with experimental allergic encephalomyelitis, and that enzymes from these cells possess the capability of digesting myelin basic protein.