光还原的硫氧还蛋白对6—磷酸葡萄糖脱氢酶的钝化作用

测定了豌豆(Pisum sativum)幼苗的重组叶绿体中光还原的硫氧还蛋白(Td)对6-磷酸葡萄糖脱氢酶(G6PDH)的钝化作用.结果表明,Td在叶绿体G6PDH的光抑制和暗激活中均起重要的调节作用.在其绿色叶片和黄化组织中,G6PDH都存在着两种同工酶,但二硫苏糖醇(DTT)和Td对黄化幼苗中G6PDH活性的影响与叶绿体的明显不同,DTT对黄化幼苗G6PDH的钝化作用和氧化Td的活化作用均低于对叶绿体中的这两种作用.     

PROPERTIES AND CHANGES OF GLUCOSE-6-PHOSPHATE DEHYDROGENASE IN GERMINATING LETTUCE SEEDS

Glucose-6-phosphate dehydrogenase is present in lettuce seedsand seedlings in a particulate, 20,000 g fraction and in a solublefraction of the cells. In both fractions the enzyme activityoccurs in the presence of either NAD or NADP. It seems probablethat an enzyme with two active sites is involved. Total activity does not change during 48 hours germination inwater. It is depressed by coumarin or thiourea treatment. Specificactivity rises in the soluble fraction when germination occurs,but not in the mitochondrial one. Coumarin treatment largelydepresses the increase in specific activity. In vitro 100 ppmcoumarin totally inhibit enzyme activity. 1,250 ppm thioureado not affect enzyme activity. The results are analysed and it is concluded that glucose-6-phosphatedehydrogenase is important, if at all, only in the very earlystages of germination. (Received August 13, 1965; )     

THE DISTRIBUTION OF SOLUBLE AND MEMBRANE-BOUND FORMS OF GLUTAMINASE IN PIG BRAIN

Abstract— About 10% of the glutaminase activity associated with pig brain mitochondria was readily extractable by a variety of techniques but the remainder was very resistant to extraction. These two forms, which have been termed the soluble and membrane-bound forms respectively, have been shown to differ in their responses to activation by phosphate and phosphate-borate containing buffers. Submitochondrial fractionation studies indicated that the soluble form was located in the mitochondrial inner matrix whereas the membrane-bound form was associated with the inner membrane. The mitochondria associated with the synaptosomes were found to contain only the membrane-bound form of the enzyme whereas both forms were present in the free brain mitochondria.     

COMPARISON OF THE BEHAVIOUR OF A SOLUBLE AND A MEMBRANE-BOUND ENZYME IN TRANSECTED PERIPHERAL NERVES

Phosphoglucoisomerase (PGI), a soluble enzyme, and AChE, a membrane-bound enzyme were studied in transected peroneal nerves of dog and in isolated segments of these nerves. Although activities of both enzymes increased at the ends of transected nerves, marked differences in their behaviour were observed. The increment in AChE activity was much sharper than that of PGI and continued to grow with time whereas the increase in PGI developed fully within the initial hours after transection and did not change thereafter. In an isolated nerve segment AChE accumulated at both ends with a concomitant decrease in the middle part, whereas changes in PGI activity appeared only in the terminal parts, the rest of the nerve remaining at the normal level. The terminal increase of PGI did not, contrary to that of AChE, depend on the length of the isolated segment. The changes in PGI activity may be features of a local peritraumatic reaction whereas those of AChE indicate involvement of the whole segment along which the enzyme containing organelles are transported.     

INFLUENCE OF COLD EXPOSURE ON THE ACTIVITIES OF SOLUBLE AND MEMBRANE-BOUND DOPAMINE β-HYDROXYLASE IN RAT HEART VESICLES

Abstract— A fraction containing noradrenaline storage vesicles of the sympathetic nerve terminals in the rat heart was obtained by differential centrifugation. In this preparation, 17% of the dopamine β-hydroxylase was present in a soluble form. Cold exposure (3°C) for periods from 5 to 30 min led to an increase in the activity of soluble dopamine β-hydroxylase by about 50%, while the activity of membrane-bound dopamine β-hydroxylase was simultaneously decreased by approx 30%. The nor-adrenaline content of the vesicles rose concomitantly with the increase in the activity of soluble dopamine β-hydroxylase. This rise in noradrenaline content was caused by an enhanced synthesis and not by an alteration in the subcellular distribution. The results are discussed with respect to the fate of dopamine β-hydroxylase during enhanced sympathetic nerve activity.     

CHANGES IN ACTIVITY OF DGLUCOSE-6-PHOSPHATE: NADP AND 6-PHOSPHO-D-GLUCONATE: NADP OXIDOREDUCTASES IN RELATION TO LIGNIFICATION OF BAMBOO

D-Glucose-6-phosphate: NADP oxidoreductase (glucose-6-phosphatedehydrogenase; EC 1.1.1.49 [EC] ) and 6-phospho-D-gluconate: NADPoxidoreductase (6-phosphogluconate dehydrogenase; EC 1.1.1.44 [EC] )were found to be present in immature bamboo. Optimal pHs ofthe glucose-6-phosphate- and 6-phosphogluconate dehydrogenaseswere found to be 8.0 and 8.5, respectively. Both enzymes were demonstrated to be NADP-specific and NADPcould not be replaced by NAD. Fructose-6-phosphate was indirectlyutilized after convrsion to glucose-6-phosphate by glucose-6-phosphateisomerase coexisting in the enzyme preparation. Pattern of enzyme activity and of respiratory breakdown of glucose-1-¹⁴Cand glucose-6-¹⁴C were investigated in connection with lignificationof bamboo and discussed in comparison with sugar metabolismof fungi-infected plant tissues. As for the changes in the enzymeactivity with growth of bamboo, it was recognized that therewas a tendency that the activity of both enzymes increased andwas maintained at a certain level even in the aged tissues.In addition there was a drop of the C₆/C₁ ratio toward the tissuesof lower parts containing considerable amount of lignin andthis phenomenon was the same as that observed in pentose phosphatemetabolism of fungi-infected plant tissues. (Received September 5, 1966; )     

Nutritional Regulation of Organelle Biogenesis in Euglena: REPRESSION OF CHLOROPHYLL AND NADP-GLYCERALDEHYDE-3-PHOSPHATE DEHYDROGENASE SYNTHESIS

Nitrogen deficiency and the presence of specific organic carbon sources prevent chloroplast development in Euglena. In exponentially growing cultures, chlorophyll levels were low and independent of the nitrogen content of the growth medium. Chlorophyll levels increased in stationary phase and the amount of chlorophyll formed was proportional to the initial nitrogen content of the growth medium; the greater the concentration of nitrogen, the greater the amount of chlorophyll synthesized during stationary phase. Washing experiments demonstrated that the major nutritional factor inhibiting chlorophyll synthesis in stationary phase cultures grown on medium containing a high carbon to nitrogen ratio was the absence of nitrogen rather than the presence of utilizable organic carbon.     

THE REGIONAL DISTRIBUTION OF d-GLYCERATE DEHYDROGENASE AND 3-PHOSPHOGLYCERATE DEHYDROGENASE IN THE CAT CENTRAL NERVOUS SYSTEM: CORRELATION WITH GLYCINE LEVELS

The activities of d -glycerate dehydrogenase, 3-phosphoglycerate dehydrogenase and lactate dehydrogenase have been measured in high-speed supernatant fractions from different regions of the cat CNS. Only d -glycerate dehydrogenase showed any significant regional variation in levels of activity, and this regional distribution correlated well with the regional distribution of glycine. In view of the previous finding that glycine inhibits d -glycerate dehydrogenase of rat cortex in a non-competitive manner suggesting endproduct inhibition (Uhr and Sneddon , 1971) this correlation is considered additional evidence to suggest that d -glycerate may be an important source of glycine in the CNS.     

Polyphenol Oxidation by Vicia faba Chloroplast Membranes: STUDIES ON THE LATENT MEMBRANE-BOUND POLYPHENOL OXIDASE AND ON THE MECHANISM OF PHOTOCHEMICAL POLYPHENOL OXIDATION

The mechanism whereby light effects polyphenol oxidation was examined with Vicia faba chloroplast membranes known to contain a bound latent polyphenol oxidase. Results obtained with the inhibitors 3-(3′,4′-dichlorophenyl)-1,1-dimethylurea (DCMU) and 2,5-dibromo-3-methyl-6-idopropyl-p-benzoquinone (DBMIB) indicated an involvement of the non-cyclic electron transport pathway in the light-dependent oxidation of polyphenols, such as dihydroxyphenylalanine (DOPA). Further evidence was provided by experiments in which (a) DOPA replaced H₂O as electron donor for the photoreduction of NADP, (b) NADP replaced O₂ as electron acceptor in the photochemical oxidation of DOPA, and (c) the variable fluorescence associated with photosystem II was increased by DOPA. The photochemical oxidation of DOPA by V. faba chloroplast membranes was insensitive to KCN and to antibodies against purified latent polyphenol oxidase. The results are consistent with the conclusion that the light-dependent oxidation of polyphenols by V. faba chloroplast membranes is achieved independently of the latent membrane-bound polyphenol oxidase. Electrons derived from polyphenols seem to enter the noncyclic electron transport chain on the oxidizing side of photosystem II and to react with O₂ at an unidentified site on the photosystem I side of the DCMU/DBMIB blocks.     

THE RELATION BETWEEN BIOCHEMICAL AND MORPHOLOGICAL DIFFERENTIATION IN BLASTOCLADIELLA EMERSONII. I. ENZYMATIC SYNTHESIS OF GLUCOSAMINE-6-PHOSPHATE

Lovett , James S., and Edward C. Cantino . (Michigan State U., East Lansing.) The relation between biochemical and morphological differentiation in Blastocladiella emersonii. I. Enzymatic synthesis of glucosamine-6-phosphate. Amer. Jour. Bot. 47(6): 499–505. Illus. 1960.—The enzyme glucosamine synthetase (glutamine-fructose-6-phosphate transamidase) was purified ca. 19-fold from extracts of the aquatic phycomycete, Blastocladiella emersonii, by centrifugation, protamine sulfate fractionation, and adsorption on Ca₃(PO₄)₂ gel The pH optimum, time course, and relation between enzyme concentration and reaction rate were established for the partially purified synthetase. The reaction was the same as that of the enzyme of Neurospora crassa: D-fructose-6- phosphate + L-glutamine —> D-glucosamine-6-phosphate + L-glutamic acid. The 20-fold purification attained resulted in an enzyme preparation with a specific activity 40 times greater than that reported for other organisms to date.     

MEMBRANE-BOUND NEURAMINIDASE IN THE BRAIN OF DIFFERENT ANIMALS: BEHAVIOUR OF THE ENZYME ON ENDOGENOUS SIALO DERIVATIVES AND RATIONALE FOR ITS ASSAY

—The activity of brain membrane-bound neuraminidase on endogenous and exogenous substrates was comparatively studied in various animals (rat, chicken, rabbit, pig, calf and human). The maximum rate of hydrolysis of endogenous substrates by membrane-bound neuraminidase (using a crude preparation of the enzyme) was different in the various animals (from 0·05 to 0·73 units, referred to 1 mg protein) and was obtained under similar but not identical optimum conditions (pH from 4·1 to 5·1; requirement or not of Triton X-100). The maximum degree of hydrolysis of endogenous substates was also different (from 15 to 27 nmol released NeuNAc/mg protein) and was obtained within different incubation periods (from 2 to 18 h). It corresponded (in rabbit, calf, human brain only), or not, to the actual exhaustion of the endogenous substrates. The endogenous substrates were recognized as both gangliosides and sialoglycoproteins. The extent of hydrolysis of sialoglycoproteins varied from 1·5% in rabbit to 15·6% in chicken brain; the hydrolysis of gangliosides (ranging from 14·1% in pig to 53·7% in rabbit brain) reached only in some animals (rabbit, calf, human) the complete transformation of major oligosialogangliosides into the neuraminidase resistant monosialoganglioside GMI. Upon addition of exogenous substrates (sialyl-lactose, ganglioside GD1a, brain sialopeptides, ovine submaxillary mucin) the actual rate of liberation of total NeuNAc (from both endogenous and exogenous substrates) considerably exceeded, although at a different extent (depending on the animal and on the added substrate used) the rate of hydrolysis of sole endogenous substrates. The possibility of an accurate assay of brain membrane-bound neuraminidase in a crude enzyme preparation is evaluated and guidelines for the assay procedure suggested.     

THE EVOLUTION OF FORM AND FUNCTION: MORPHOLOGY AND LOCOMOTOR PERFORMANCE IN WEST INDIAN ANOLIS LIZARDS

I tested biomechanical predictions that morphological proportions (snout–vent length, forelimb length, hindlimb length, tail length, and mass) and maximal sprinting and jumping ability have evolved concordantly among 15 species of Anolis lizards from Jamaica and Puerto Rico. Based on a phylogenetic hypothesis for these species, the ancestor reconstruction and contrast approaches were used to test hypotheses that variables coevolved. Evolutionary change in all morphological and performance variables scales positively with evolution of body size (represented by snout–vent length); size evolution accounts for greater than 50% of the variance in sprinting and jumping evolution. With the effect of the evolution of body size removed, increases in hindlimb length are associated with increases in sprinting and jumping capability. When further variables are removed, evolution in forelimb and tail length exhibits a negative relationship with evolution of both performance measures. The success of the biomechanical predictions indicates that the assumption that evolution in other variables (e.g., muscle mass and composition) did not affect performance evolution is probably correct; evolution of the morphological variables accounts for approximately 80% of the evolutionary change in performance ability. In this case, however, such assumptions are clade-specific; extrapolation to taxa outside the clade is thus unwarranted. The results have implications concerning ecomorphological evolution. The observed relationship between forelimb and tail length and ecology probably is a spurious result of the correlation between these variables and hindlimb length. Further, because the evolution of jumping and sprinting ability are closely linked, the ability to adapt to certain microhabitats may be limited.     

TLR4全长及其截断体重组腺病毒对Rf-6A细胞骨架的影响

为了研究LPS受体TLR4全长及其胞内段缺失的TLR4截断体(ΔTLR4)的绿色荧光蛋白重组腺病毒对内皮细胞系Rf-6A骨架蛋白的影响,采用PCR方法扩增目的基因片段,亚克隆至腺病毒穿梭质粒pAdTrack中,用BJ5183细菌同源重组法将目的基因重组于腺病毒骨架载体,重组腺病毒质粒经Pac Ⅰ酶切线性化后,用脂质体法转染293细胞进行腺病毒的包装扩增,用重组腺病毒感染Rf-6A细胞,采用免疫荧光标记方法观察结果。免疫荧光标记结果表明Ad-ΔTLR4明显抑制了LPS引起的细胞骨架F-actin的解聚与重排,Ad-TLR4则使LPS引起的F-actin应力纤维产生增强。以上结果说明TLR4全长及其截断体的重组腺病毒感染内皮细胞对LPS诱导的细胞骨架变化具有不同的影响,Ad-ΔTLR4对LPS引起的内皮细胞骨架变化具有抑制作用。     

GABA IN THE OLFACTORY BULB AND OLFACTORY NUCLEUS OF THE RAT: THE DISTRIBUTION OF GAMMA-AMINOBUTYRIC ACID, GLUTAMIC ACID DECARBOXYLASE, GABA TRANSAMINASE AND SUCCINATE SEMIALDEHYDE DEHYDROGENASE

Abstract— The distribution of GABA and enzymes involved in its metabolism was investigated in the different regions of the olfactory bulb and olfactory nucleus. The highest levels of GABA in the olfactory bulb were found in the layers rich in nerve terminals (31 μmol/g dry wt.). A similar distribution was found in the olfactory nucleus although the overall level of GABA was only a quarter of that measured in the bulb. Glutamic acid decarboxylase (GAD) levels in the various layers of the olfactory nucleus were similar in distribution to those of GABA. However, the correlation between GAD and GABA did not hold for the olfactory bulb, particularly in the granule cell layer and the medulla. The activities of GAD and the levels of GABA are significantly higher in the bulb than in the nucleus but succinic acid scmialdehyde dehydrogenase and GABA aminotransaminase activities are almost identical in both regions.     

INTRACELLULAR LOCALIZATION OF ENZYMES IN SPLEEN : I. REDUCED DIPHOSPHOPYRIDINE NUCLEOTIDE CYTOCHROMEc REDUCTASE, CYTOCHROMEc OXIDASE, AND SUCCINIC DEHYDROGENASE IN THE RAT AND GUINEA PIG

1. The intracellular distribution of nitrogen, DPNH cytochrome c reductase, succinic dehydrogenase, and cytochrome c oxidase has been studied in fractions derived by differential centrifugation from rat and guinea pig spleen homogenates. 2. In the spleens of each species, the nuclear fraction accounted for 40 to 50 per cent of the total nitrogen content of the homogenate, and the mitochondrial, microsome, and supernatant fractions contained about 8, 12, and 30 per cent of the total nitrogen, respectively. 3. Per mg. of nitrogen, DPNH cytochrome c reductase was concentrated in the mitochondria and microsomes of both rat and guinea pig spleens. Seventy per cent of the total DPNH cytochrome c reductase activity was recovered in these two fractions. The reductase activity associated with the nuclear fraction was lowered markedly by isolating nuclei from rat spleens with the sucrose-CaCl₂ layering technique. The lowered activity was accompanied by the recovery of about 90 per cent of the homogenate DNA in the isolated nuclei, indicating that little, if any, of the reductase is present in spleen cell nuclei. 4. Per mg. of nitrogen, succinic dehydrogenase was concentrated about 10-fold in the mitochondria of rat spleen, and 65 per cent of the total activity was recovered in this fraction. 5. Cytochrome c oxidase was concentrated, per mg. of nitrogen, in the mitochondria of both rat and guinea pig spleens. The activity associated with the nuclear fraction was greatly diminished when this fraction was isolated from rat spleens by the sucrose-CaCl₂ layering technique. Only 50 to 70 per cent of the total cytochrome c oxidase activity of the original homogenates was recovered among the four fractions from both rat and guinea pig spleens, while the specific activities of reconstructed homogenates were only 55 to 75 per cent of those of the original whole homogenates. This was in contrast to the results with DPNH cytochrome c reductase and succinic dehydrogenase where the recovery of total enzyme activity approached 100 per cent, and the specific activities of reconstructed homogenates equalled those of the original homogenates. The recovery of cytochrome c oxidase was greatly improved when only the nuclei were separated from rat spleen homogenates. 6. Data were presented comparing the concentrations (ratio of activity per mg. of nitrogen of the fraction to activity per mg. of nitrogen of the homogenate) of DPNH cytochrome c reductase in mitochondria and microsomes derived from different organs of different animals. 7. Data were presented comparing the activities per mg. of nitrogen of DPNH cytochrome c reductase in homogenates from several organs of various animals.     

Studies on the Growth in Culture of Plant Cells: XIX. CHANGES IN THE LEVELS OF FREE AND MEMBRANE-BOUND POLYSOMES DURING THE GROWTH OF ACER PSEUDO PLA TAN US CELLS IN BATCH SUSPENSION CULTURE

Techniques have been established which give reproducible yieldsof total and of free and bound polysoines from cultured sycamorecells liarvested at intervals throughout the cycle of growthfollowed in batch culture. High levels of polysoines build upin the cells during lag phase and persist into early exponentialgrowth. Later in the growth cycle, although the ribosomal materialper unit volume of culture continues to rise, the content percell of ribosomes and polysomes progressively declines untilthe cells enter the stationary phase. There is also a characteristicpattern of change in the relative proportions of free and boundpolysomes throughout the growth cycle of the cultures. Bothfractions contain different but significant levels of ribosomalsubunits and monomers. The RNAs released from the free polysoineshad a greater amount of poly(A) sequences than that from thebound polysomes. These findings are discussed in relation tothe changing metabolic activities of the cells which occur duringtheir progress through batch culture.     

AN EMPIRICAL TEST OF PREDICTIONS OF TWO COMPETING MODELS FOR THE MAINTENANCE AND FATE OF HYBRID ZONES: BOTH MODELS ARE SUPPORTED IN A HARD-CLAM HYBRID ZONE

Two models developed to discern the mode of selection in hybrid zones differ in some predictions. The tension-zone model predicts that selection acts against hybrids and independently of the environment (endogenous selection) and that selection is invariant throughout the hybrid zone. The ecological selection-gradient, or ecotone, model maintains that fitness of different genotypes varies in response to environmental variation (exogenous selection) and thus, that in a region of the zone, fitness of hybrids is at least equal to that of the parental species. Therefore, to assess the predominant mode of selection operating in a hybrid zone, it is fundamental to evaluate whether selection is acting specifically against hybrid individuals, that is, whether hybridity alone is the basis for deficiencies of hybrids, and to evaluate whether the relative fitness of hybrids versus that of pure species varies across the zone. In a hardclam (genus Mercenaria) hybrid zone located in a polyhaline lagoon in east-central Florida, we used age-specific and location-specific analyses to determine that a hybrid deficit occurrs, that the deficit seems to be due to selection against hybrids, and that selection varies across the zone. Various measures of deviation from Hardy-Weinberg equilibrium, linkage disequilibrium analyses, and shifts in allele frequencies at semidiagnostic loci support the idea that selection is strongest in the northern region of the lagoon, the zone of sympatry and hybridization. Southward, into the range of M. mercenaria (the numerically predominant species), the percentage of hybrids remains relatively high and selection against hybrids decreases. For some genetic linkage groups, selection for M. mercenaria alleles seems to be occurring, but selection seems to be acting principally against alleles characteristic of M. mercenaria and, to a lesser degree, for alleles characteristic of M. campechiensis (the rarer species). These findings and others from previous analyses we have done on this hybrid zone demonstrate that selection in the zone is complex, and that characteristics of both the tension-zone and ecotone models are present. Supporting the tension-zone model, selection against hybrids per se clearly occurs, but specific genotypes seem to be at a selective disadvantage, whereas others have a selective advantage, and selection operates differentially on the two parental species within the zone. Supporting the ecotone model, the strength of overall selection varies throughout the zone, and environmentally mediated selection in which each species and hybrids have an advantage in specific habitats occurs, but some selection against hybrids is invariant throughout the zone. Thus, the structure and genetic architecture of this hybrid zone appear to be products of a complicated interaction between both types of selective forces cited in the two competing models.     

Devlopmental Physiology of Sugar-Beet: II. EFFECTS OF TEMPERATURE AND NITROGEN SUPPLY ON THE GROWTH, SOLUBLE CARBOHYDRATE CONTENT AND NITROGEN CONTENT OF LEAVES AND ROOTS

Plants were grown at temperatures of 15 and 25 ?C with two ratesof nitrogen supply. The changes in dry weight, leaf area, cellnumber, mean cell volume, soluble carbohydrate, and total nitrogenconcentration of the cotyledons, the first and second pair oftrue leaves, and the storage root were measured. Changes incell number and cell volume of the first pair of true leavesand storage root of plants were also measured at 11, 18, 25,and 32 ?C. Leaf growth before unfolding was chiefly by increase in cellnumber and after unfolding by increase in mean cell volume,while the growth of the storage root was almost entirely byincrease in cell number. The rates of cell division and cellexpansion were fastest at 25 ?C, but the initially high ratesof cell division in the terminal bud and in individual leavesdecreased rapidly and greater rates were maintained at the sub-optimaltemperatures, i.e. 15 and 18 ?C. After an initial period ofslow growth, the first-formed leaves grew faster and becamelarger at 15 than at 25 ?C. Leaves were produced, unfolded,grew faster, and became larger with increase in the externalconcentration of nitrogen, because cells divided and expandedfaster, so that nitrogen increased the number and size of cells. Sugar concentration was greater at 15 than at 25 ?C in leavesbut not in the storage root. Sugar concentration in the petiolesof the first and second pair of true leaves increased to 1.2and 2.0 per cent fresh weight respectively. Decreased nitrogensupply temporarily increased the sugar concentration of cotyledonpetioles and the seedling hypocotyl, but later decreased itin the leaves and storage root. Nitrogen concentration was greaterin the leaves and storage root at 15 than at 25 ?C with thelarger nitrogen supply. Nitrogen concentrations were similarin young leaves of all treatments but as the size of leavesincreased nitrogen concentrations decreased most rapidly at25 ?C with the smaller nitrogen supply. It is suggested that when increased leaf production and storage-rootgrowth occurs at temperatures below the growth optimum (25 ?C),they may be due to an effect of increased carbohydrate supplyon cell division and sugar storage.