Search results for "terase"
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Vārtājas ledājkušanas ūdeņu drenāžas ieleja
2018
Bakalaura darba mērķis ir izpētīt Vārtājas ledajkušanas ūdeņu drenāžas ielejas ģeomorfoloģisko un ģeoloģisko uzbūvi un attīstību, noskaidrot, kādā deglaciācijas posmā ieleja ir izveidota, un klasificēt, kāda tipa ielejai pieder Vārtājas ieleja. Darba autors, izstrādājot bakalaura darbu, lauku pētījumu ietvaros izveidoja 4 atsegumus, kuros tika veikta fāciju aprakstīšana un trijos atsegumos tika veikti slāņu mērījumi. Iegūtie slāņu mērījumu dati ļāva interpretēt ledājkušanas ūdeņu straumju virzienus. Darba teorētiskajā sadaļā tiek apskatīta teritorijas ģeoloģiskā uzbūve, glacigēnā reljefa uzbūve, fluviālā un glaciofluviālā reljefa uzbūve, deglaciācijas vēsture un Baltijas ledus ezera attīstī…
Evolution of ecdysteroids and of their apolar conjugates during the post-embryonic development of the tickOrnithodoros moubata
1997
The ecdysteroid (ES) content of the soft tick Ornithodoros moubata was investigated during the five successive nymphal molting cycles by means of an enzyme immunoassay (EIA). Samples were submitted to esterase hydrolysis in order to release free ecdysteroids from the acyl-ester conjugates (AP = apolar products). Crude and hydrolysed extracts were then analyzed by EIA using two different antibodies, a monoclonal raised against 20-hydroxyecdysone (20E) and a polychlonal raised against ecdysone (E). With the crude extracts, each molting cycle was associated with an ES peak, occurring in the middle of the instar. 20E was preponderant during the first 2 nymph cycles, but the proportion of E and …
Hydrolytic enzymes in the coelomic cells of the polychaeteNereis virens during sexual maturation
1991
Nereis virens were collected between April 1989 and April 1990 at Yerseke, Oosterscheldt Bay, The Netherlands. Activities of the hydrolytic enzymes arylsulfatase, acid phosphatase, N-acetylglucosaminidase, aminopeptidase, and carboxylesterase were investigated in coelomic cells (elaeocytes) of individuals at different stages of maturation as determined by the time course of oocyte growth. On a protein-content basis, up to ten-fold higher specific activities were present in the elaeocytes compared to the body-wall tissue. Acid phosphatase, N-acetylglucosaminidase, leucine aminopeptidase, and long- and medium-chain esterase increased continuously from the beginning to the later stage of sexua…
Phosphodiesterase inhibitor pentoxifylline, a selective suppressor of T helper type 1- but not type 2-associated lymphokine production, prevents indu…
1993
The phosphodiesterase inhibitor pentoxifylline (POX), which is known to have pharmacological effects in animal models of multiorgan failure and endotoxin-mediated shock, was tested for its immunosuppressive potential on T lymphocyte activation in vitro and in vivo. POX was found to have a profound inhibitory effect on both mitogen- and antigen-induced proliferation of CD4+ T cells in vitro. This inhibitory activity of the drug could be reproduced by treating T lymphocytes with cAMP analogues during stimulation. Responses of repeatedly in vitro stimulated cells were much more strongly inhibited by the drug and by cAMP analogues than responses of fresh resting lymphocytes. Furthermore, POX co…
Neuromuscular junction disassembly and muscle fatigue in mice lacking neurotrophin-4
2001
Neurotrophin-4 (NT-4) is produced by slow muscle fibers in an activity-dependent manner and promotes growth and remodeling of adult motorneuron innervation. However, both muscle fibers and motor neurons express NT-4 receptors, suggesting bidirectional NT-4 signaling at the neuromuscular junction. Mice lacking NT-4 displayed enlarged and fragmented neuromuscular junctions with disassembled postsynaptic acetylcholine receptor (AChR) clusters, reduced AChR binding, and acetylcholinesterase activity. Electromyographic responses, posttetanic potentiation, and action potential amplitude were also significantly reduced in muscle fibers from NT-4 knock-out mice. Slow-twitch soleus muscles from thes…
Time-dependent effects of polystyrene nanoparticles in brine shrimp Artemia franciscana at physiological, biochemical and molecular levels
2019
Micro- (<5 mm) and nanoplastics (<1 μm) are emerging threats for marine ecosystems worldwide. Brine shrimp Artemia is recognized as a suitable model among planktonic species for studying the impact of polystyrene nanoparticles (PS NPs) through short and long-term bioassays. Our study aims to evaluate the time-dependent effects of cationic amino-modified PS-NH (50 nm) in A. franciscana after short- (48 h) and long-term exposure (14 days). For this purpose, nauplii were exposed to a concentration range of PS-NH (0.1, 1, 3 and 10 μg/mL) in natural sea water (NSW), and physiological, biochemical and molecular responses were investigated. Short-term exposure to PS-NH caused a decrease in nauplii…
Short-term exposure of the European sea bass Dicentrarchus labrax to copper-based antifouling treated nets: copper bioavailability and biomarkers res…
2012
Abstract We studied if the levels of copper released from antifouling treated nets used in finfish mariculture could affect the immune defense mechanism and/or induce oxidative stress in Dicentrarchus labrax , after short term exposure in laboratory experiments. Dissolved copper concentration released from the treated nets, copper bioavailability and a set of biomarkers responses were measured. Biomarkers included hemoglobin concentration, activities of lysozyme, total complement, respiratory burst, glutathione S-transferase and acetycholinesterase and concentration of thiobarbituric acid reactive substances. Results indicated elevated copper concentration in seawater (184 μg L −1 ) but low…
Sequence similarity of mammalian epoxide hydrolases to the bacterial haloalkane dehalogenase and other related proteins Implication for the potential…
1994
Direct comparison of the amino acid sequences of microsomal and soluble epoxide hydrolase superficially indicates that these enzymes are unrelated. Both proteins, however, share significant sequence similarity to a bacterial haloalkane dehalogenase that has earlier been shown to belong to the alpha/beta hydrolase fold family of enzymes. The catalytic mechanism for the dehalogenase has been elucidated in detail [Verschueren et al. (1993) Nature 363, 693-698] and proceeds via an ester intermediate where the substrate is covalently bound to the enzyme. From these observations we conclude (i) that microsomal and soluble epoxide hydrolase are distantly related enzymes that have evolved from a co…
Inhibitory activity of sphingomyelin on hemolytic activity of coelomic fluid of Holothuria polii (echinodermata)
1987
Abstract The hemolytic activity of coelomic fluid from Holothuria polii is specifically inhibited by sphingomyelin. This phospholipid is the constituent of the membrane which probably interacts with the hemolysin thereby leading to the lysis.
Evidence that clustered phosphocholine head groups serve as sites for binding and assembly of an oligomeric protein pore.
2006
High susceptibility of rabbit erythrocytes toward the pore-forming action of staphylococcal alpha-toxin correlates with the presence of saturable, high affinity binding sites. All efforts to identify a protein or glycolipid receptor have failed, and the fact that liposomes composed solely of phosphatidylcholine are efficiently permeabilized adds to the enigma. A novel concept is advanced here to explain the puzzle. We propose that low affinity binding moieties can assume the role of high affinity binding sites due to their spatial arrangement in the membrane. Evidence is presented that phosphocholine head groups of sphingomyelin, clustered in sphingomyelin-cholesterol microdomains, serve th…