Inhibition of esterase and amidase activities of alpha- and beta-thrombin in the presence of antithrombin III and heparin

Inhibition of the esterase and amidase activities of bovine alpha- and beta-thrombin in the presence of antithrombin III and heparin has been studied. It was found that both the esterase and amidase activities of alpha-thrombin were inhibited by antithrombin III and the reactions were accelerated by heparin. The inhibition of amidase and esterase activities of beta-thrombin by antithrombin III has also been demonstrated. Heparin however did not increase the rate of inactivation of the enzyme.     

Enzymes of the human intestinal brush border membrane. Identification after gel electrophoretic separation

The position of a number of human intestine brush border membrane enzyme activities in polyacrylamide gels after electrophoresis has been determined. These activities are, in order from the origin, maltase/glucoamylase, lactase/phlorizin hydrolase, maltase/sucrase/isomaltase, enteropeptidase, trehalase and γ-glutamyltransferase. Leucylnaphthylamide hydrolyzing activity was inactivated by sodium dodecylsulfate and its position was not determined. The positions of the activities have been correlated with the positions of protein bands previously determined. One such band situated between enteropeptidase and alkaline phosphatase has not been identified.     

Enzymes of the human intestinal brush border membrane. Identification after gel electrophoretic separation.

The postition of a number of human intestine brush border membrane enzyme activities in polyacrylamide gels after electrophoresis has been determined. These activities are, in order from the origin, maltase/glucoamylase, lactase/phlorizin hydrolase, maltase/sucrase/isomaltase, enteropeptidase, trehalase and gamma-glutamyl-transferase. Leucylnaphthylamide hydrolyzing activity was inactivated by sodium dodecylsulfate and its position was not determined. The positions of the activities have been correlated with the positions of protein bands previously determined. One such band situated between enteropeptidase and alkaline phosphatase has not been identified.     

The Development of the Enzyme Complement in Growing Root Cells

Fifteen serial sections, each 1.0 mm. in length, have been takenfrom the tip towards the base of the bean root. On correspondinggroups of sections determinations have been made of water content,protein content, and of dipeptidase, glycine oxidase, phosphatase,and invertase activities. The number of cells in each sectionof the series has also been determined. From these data unitcell values have been calculated which show how each of thequantities involved changes as the cell grows. It has been shown that four phases are involved in the earlydevelopment of the cell. In the first, which is traversed inthe meristematic zone of the root, the volume increases slightly,the protein content decreases, and the activities of three ofthe enzymes studied also decrease. In the second, volume, proteincontent, and all enzyme activities increase considerably. Inthe third, while the volume enlarges by increase in breadthonly, protein content and enzyme activities decrease. In thefourth, growth has ceased and protein content, and enzyme activitiescontinue to decrease. The significance of these changes in discussed.     

Deoxyribonucleases of the organs of Drosophila hydei at the onset of metamorphosis

The tissue distribution of deoxyribonucleases has been studied in the organs of Drosophila hydei at the onset of metamorphosis. The enzymes were separated by disc electrophoresis and detected directly in the gel. An extensive shift in the wide spectrum of activities that has been observed at metamorphosis indicates that deoxyribonucleases play an important role at this time in development. On the basis of the tissue distribution of these enzymes, it has been possible to assign probable functions to several of the activities. An intense activity appears in the prepupal salivary gland which is not detected in this organ in the larval stage. This observation is of particular interest in view of the changes that have been observed in the chromosomal puffing patterns of the salivary glands just prior to metamorphosis. A class of activities, which is probably of lysosomal origin, is more prevalent in the prepupal tissues. The data suggest that an increased synthesis of lysosomes is a general reaction of most larval tissues at the onset of metamorphosis irrespective of whether a tissue undergoes total histolysis. The larval intestine contains a factor which strongly inhibits Drosophila nucleases that are active at low pH. The major nuclease activities of each tissue have been tentatively characterized. A knowledge of the enzyme properties is expected to facilitate the isolation of DNA from the individual tissues.This work was performed in the Max-Planck-Institut für Biologie, Abteilung Beermann, Tübingen, Germany. The senior author was supported by the Helen Hay Whitney Foundation.     

Comparative effects of antiepileptics on the alkaline phosphatase and gamma glutamyltransferase activities in plasma and leukocytes]

Alkaline phosphatase and gamma glutamyltransferase activities have been compared in plasma and leukocytes from presumably healthy subjects and from epileptic patients under treatment with different antiepileptic drugs. Plasma enzyme activities are always increased by antiepileptic treatment, leukocytic enzyme activities are increased only for some patients. No relation has been observed between the variations in any of the two enzyme activities and plasma level of anticonvulsant drugs.     

Kinetic studies of aminoglycoside acetyltransferase and phosphotransferase from Staphylococcus aureus RPAL. Relationship between the two activities

In the Staphylococcus aureus strain harbouring the plasmid RPAL, the resistance to aminoglycoside antibiotics results from two inactivating reactions catalyzed by a 6'-N-aminoglycoside acetyltransferase and a 2"-O-amino-glycoside phosphotransferase. These enzymes are copurified with a constant ratio between the two activities, the purification process consisting in affinity chromatography, native electrophoresis and gel exclusion chromatography. The kinetic mechanisms of each activity have been determined from studies of initial velocities, as well as product and dead-end inhibitions. Both activities follow a random rapid equilibrium mechanism. The substrates and cofactors of one reaction have been tested as effectors of the other reaction. No interaction between the two activities has been observed. However, the GTP cofactor of phosphotransferase protects, at weak concentrations, the acetyltransferase against thermal inactivation, which suggests that the two activities may be associated.     

The ciliate, Troglodytella abrassarti, contributes to polysaccharide hydrolytic activities in the chimpanzee colon

Entodiniomorphid ciliates are intestinal protists inhabiting the colons of African great apes. The participation of intestinal entodiniomorphid ciliates in ape hindgut digestion has been proposed, but little data have been available to support the hypothesis. We measured the specific activities of carboxymethyl cellulase, xylanase, inulinase, and α-amylase against different polysaccharides in the feces of captive chimpanzees and evaluated the participation of the entodiniomorphid ciliate, Troglodytella abrassarti, in these activities. T. abrassarti contributed to the total fecal hydrolytic activities of CM-cellulase by 16.2%, α-amylase by 5.95%, and xylanase by 0.66%. Inulinase activity in T. abrassarti samples was not measurable at reaction conditions used. The ciliates, T. abrassarti, actively participate in the chimpanzee hindgut fermentation of fiber and starch.     

Studies on the regulation of the branched chain amino acyl-tRNA synthetases of the fungusNeurospora crassa

Summary The specific activities of the branched chain amino acyl-tRNA synthetases from the cytosolic and mitochondrial fractions ofN. crassa were low in dormant conidia and increased during germination, reaching a maximum 8 h after inoculation. This stage of development is characterised by high rates of many other cellular activities.The increases in activity of synthetases of both cytosol and mitochondria are inhibited by cycloheximide indicating that they are synthesized on cytoplasmic ribosomes. The mitochondrial synthetases show a stimulation of their specific activity when mitochondrial RNA and protein synthesis are inhibited by either ethidium bromide or chloramphenicol suggesting that a mitochondrial translation product regulates the synthesis of the mitochondrial synthetases.The activities of amino acyl-tRNA synthetases are dependent on energy production. When respiration is uncoupled from oxidative phosphorylation, synthetase specific activities decrease although the activities of other mitochondrial enzymes like NADH-dehydrogenase increase. This phenomenon suggests that more than one mechanism regulates the synthesis of mitochondrial proteins which are formed on cytoplasmic ribosomes.The synthesis of branched chain amino acyl-tRNA synthetases ofNeurospora is neither repressed by their cognate amino acids, nor is there inhibition by the precursors of these amino acids, as has been observed in other amino acyl-tRNA synthetases of various organism includingNeurospora.     

An immunochemical analysis of the induction of cytochrome P-450 isoforms in the liver of fresh-water fishes by 3-methylcholanthrene, beta-naphthoflavone and aroclor 1254

The cytochrome P-450 isoforms have been studied in liver microsomes of some fish species from Lake Baikal. Using the inhibitory analysis of microsomal monooxygenase activities carried out by the specific polyclonal antibodies it has been shown that 3-methylcholanthrene, beta-naphthoflavone and arochlor 1254 induce isoforms immunologically related to cytochrome P-488c but not to the rat cytochrome P-450b in fish liver microsomes. The immunologic identity in isoforms of fish and rat cytochromes induced by methylcholanthrene has not been revealed. A possibility to use the method of the inhibitory analysis of fish microsomal activities by specific antibodies to the rat cytochrome P-450 isoforms for biomonitoring and biotesting of polycyclic hydrocarbons and polychlorinated biphenyls in aquatic systems is discussed.     

Computational experiments support a competitive function in the the CA3 region of the hippocampus

The comprehension of activities and functions of complex brain structures requires, among other things, information on simultaneous activities in several regions. Results reported in the literature using multi(micro/macro)electrode recordings or imaging techniques provide incomplete information due either to the small size and/or small number of investigated regions or to the poor spatiotemporal resolution, respectively. This is particularly true for the hippocampus and its subfields, and mathematical modeling and computer simulation have been used with the aim of obtaining information when this is lacking. Global activities in the CA3 field of the hippocampus, and in particular the genesis of theta rhythm and sharp waves, have been investigated here by a mathematical model formulated within the frame of a kinetic theory of neural systems. The model has taken into account data of experimental results both on different PSPs recorded in hippocampal neurons and on recurrent pyramidal collateral geometries. The computational ‘experiments’ to which the model was subjected suggest that the sharp waves arise through a selective and short block of the fast inhibitory neurons of CA3, produced by a medial septum inhibitory input, whereas the theta activity is produced by a durable, continuous inhibition of the slow inhibitory neurons. Information obtained also suggests that the recurrent pyramidal collaterals subserve a competitive, rather than a cooperative, organization. Based on these results a hypothesis on the possible functional organization of the CA3 field and of the entire hippocampus has been formulated. According to this hypothesis, the CA3 imposes a serial order on the flow of activity arriving at the hippocampus from the entorhinal cortex and from its connected polymodal cortical regions. This ordering permits cortical activities, arriving at CA3 on appropriate time intervals, to produce effects in regions of brain to which the CA3 projects. The competing cortical activities are lost.     

Training the next generation of protein scientists

Carl Brändén made significant contributions in areas of protein X‐ray crystallography and science education. As the 2011 recipient of the Protein Society award honoring Carl's contributions, I had the opportunity to reflect on the undergraduate educational activities that have been practiced in my own laboratory over the past 24 years at the University of Maryland Baltimore County, an institution that emphasizes both research and undergraduate education. A system has been developed that attempts to minimize the tension that can exist between conflicting graduate research and undergraduate mentoring goals. The outcomes, as measured not only by subsequent activities of the participating undergraduates, but also by the activities of the graduate students and postdocs that worked with the undergraduates, indicate a general overall benefit for all participants, particularly for women and underrepresented minorities who are traditionally poorly retained in the sciences. Greater participation of undergraduates in research activities of active scientists who often focus primarily on graduate and postdoctoral training could have a positive impact on the leaky undergraduate science pipeline.     

Lipid-metabolizing enzymes of myelin and their relation to the axon

The old concept of myelin as a metabolically inert membrane has been considerably revised as a result of the discovery of numerous enzyme activities in the isolated membrane. The high degree of purification and low levels of contamination markers leave little doubt that the measured activities are intrinsic to myelin itself. Slightly more than half of the discovered activities involve lipid metabolism. One such enzyme, neutral cholesterol esterase, is myelin-specific, while the rest occur in other subcellular fractions as well as myelin. These include activities involved in synthesis of cerebrosides, phospholipids, and cholesteryl esters; only a few degradative enzymes are presently known. In vivo studies have shown that various substrates utilized by lipid-synthesizing enzymes of myelin can originate in the axon. Six such substrates have been characterized. The possibility exists that these enzymes may be wholly or partially dependent on the axon as the primary source of substrate, thereby suggesting a possible form of metabolic dependency of myelin on the axon.     

Protein modification enzymes associated with the protein-synthesizing complex from rabbit reticulocytes. Protein kinase, phosphoprotein phosphatase, and acetyltransferase.

A number of protein modification activities are present in the protein-synthesizing complex isolated from rabbit reticulocytes. These enzymes are solubilized by sedimentation of the ribosomes through buffered sucrose containing 0.5 M KCl, and have been partially purified from the high salt wash fraction by chromatography on DEAE-cellulose and phosphocellulose. The ribosomal-associated enzymatic activities include cyclic AMP-regulated and cyclic nucloetide-independent protein kinase, phosphoprotein phosphatase, and acetyltransferase activities. These enzymatic activities have been shown to modify specific ribosomal and ribosomal-associated proteins. The cycli c AMP-regulated protein kinase phosphorylate the 40 S ribosomal subunit from rabbit reticulocytes. One of the cyclic nucleotide-independent protein kinase catalyzes the phosphorylation of two different factors involved in the initiation of hemoglobin synthesis. A single phosphoprotein phosphatase activity is shown to remove phosphate from 40 S ribosomal subunits. The major acetyltransferase activity associated with ribosomes acetylates a 60 S ribosomal protein.     

Kinetic theory of neural systems: Analysis of the activity of the two-dimensional model

The behaviour of some two-dimensional neural systems has been studied by a numerical solution of the associated kinetic equations. The ability of the model to sustain the propagation of informational waves and rhythmic activities as well as memory effects has been demonstrated.     

The effect of hexadecylphosphocholine on the degradation of mitochondrial phospholipids

Hexadecylphosphocholine (HePC) is known as antitumor agent but the mechanism has not yet been understood. In rat liver mitochondria its effect on phospholipid transformation has been studied by quantitative HPTLC and phosphorus determination. From the results it can be concluded that HePC influences the activities of phospholipase A₂, phospholipase C, phospholipase D, and lysophospholipase A. The phospholipid transformation as well as the influence of HePC are affected by exogenous calcium ions. In the presence of calcium HePC has been found to inhibit enzyme activities, whereas in the absence of exogenous calcium ions enzymatic phospholipid transformations are activated or inhibited depending on HePC concentrations.     

Longer conserved alpine forests ecosystem exhibits higher stability to climate change on the Tibetan Plateau

Aims Vegetation dynamics are simultaneously regulated by climate change and anthropogenic activities. Since the 1980s, climate has been warming on the Tibetan Plateau (TP) at a rate higher than North Hemisphere average. Anthropogenic activities, including grazing, farming, and urbanization, are also influencing the alpine ecosystem on the TP. Especially, an ensemble of large engineering projects, such as power transported from west to east by State Grid, has been in operation on the TP. While studies disentangling effects of climate and anthropogenic activities interference are still lacking for the forest ecosystems on the TP. The overarching objectives of this study were to separate effects of natural climates and human interferences on forest ecosystem dynamics on the TP.     

Light microscopical visualization of phosphatase activities demonstrated with the cerium method in resin sections of the kidney with the microwave oven

The light microscopically invisible reaction product cerium phosphate in resin sections of rat kidney, that had been incubated for the demonstration of phosphatase activities before embedding, was converted into a visible reaction product by incubation for 10 min at 80 degrees C in alkaline lead citrate in a microwave oven. This method offers the possibility to study phosphatase activities with the cerium method in semithin Epon sections. Furthermore it is a suitable method to select areas with phosphatase activity to be studied with the electron microscope.     

Characterization of the biochemical properties of the human Upf1 gene product that is involved in nonsense-mediated mRNA decay

The Upf1 protein in yeast has been implicated in the modulation of efficient translation termination as well as in the accelerated turnover of mRNAs containing premature stop codons, a phenomenon called nonsense-mediated mRNA decay (NMD). A human homolog of the yeast UPF1, termed HUpf1/RENT1, has also been identified. The HUpf1 has also been shown to play a role in NMD in mammalian cells. Comparison of the yeast and human UPF1 proteins demonstrated that the amino terminal cysteine/histidine-rich region and the region comprising the domains that define this protein as a superfamily group I helicase have been conserved. The yeast Upf1p demonstrates RNA-dependent ATPase and 5' --> 3' helicase activities. In this paper, we report the expression, purification, and characterization of the activities of the human Upf1 protein. We demonstrate that human Upf1 protein displays a nucleic-acid-dependent ATPase activity and a 5'--> 3' helicase activity. Furthermore, human Upf1 is an RNA-binding protein whose RNA-binding activity is modulated by ATP. Taken together, these results indicate that the activities of the Upf1 protein are conserved across species, reflecting the conservation of function of this protein throughout evolution.     

Light microscopical visualization of phosphatase activities demonstrated with the cerium method in resin sections of the kidney with the microwave oven

Summary The light microscopically invisible reaction product cerium phosphate in resin sections of rat kidney, that had been incubated for the demonstration of phosphatase activities before embedding, was converted into a visible reaction product by incubation for 10 min at 80° C in alka-line lead citrate in a microwave oven. This method offers the possibility to study phosphatase activities with the cerium method in semithin Epon sections. Furthermore it is a suitable method to select areas with phosphatase activity to be studied with the electron microscope.