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1.
Mastoparan induces Ca2+-dependent deflagellation of the unicellular green alga Chlamydomonas moewusii Gerloff, as well as the activation of phospholipase C and the production of inositol 1,4,5-trisphosphate (InsP3; T. Munnik et al., 1998, Planta 207: 133–145). Even in the absence of extracellular Ca2+, mastoparan still induces deflagellation (L.M. Quarmby and H.C. Hartzell, 1994, J Cell Biol 124: 807–815; J.A.J. van Himbergen
et al., 1999, J Exp Bot, in press) suggesting that InsP3 mediates Ca2+ release from intracellular stores. To test this hypothesis, cells were pre-loaded with 45Ca2+ and their plasma membranes permeabilized by digitonin. Subsequent treatment of the cells with mastoparan (3.5 μM) induced
release of intracellular 45Ca2+. Mastoparan also activated phospholipase C in permeabilized cells, as demonstrated by the breakdown of 32P-phosphatidylinositol 4,5-bisphosphate and the production of diacylglycerol. The mastoparan analogues mas7 and mas17 were
also effective and their efficacy was correlated with their biological activity. X-ray microanalysis showed that electron-dense
bodies (EDBs) are a major Ca2+ store in C. moewusii. Analysis of digitonin-permeabilized cells showed that EDBs lost calcium at digitonin concentrations that released radioactivity
from 45Ca2+-labelled cells, suggesting that 45Ca2+ monitored the content of EDBs. X-ray microanaysis of living cells treated with mastoparan also revealed that calcium was
released from EDBs.
Received: 30 December 1998 / Accepted: 25 June 1999 相似文献
2.
3.
Doxorubicin and other anthracyclines rank among the most effective anticancer drugs ever developed. Unfortunately, the clinical
use of anthracyclines is limited by a dose-related life-threatening cardiotoxicity. Understanding how anthracyclines induce
cardiotoxicity is essential to improve their therapeutic index or to identify analogues that retain activity while also inducing
less severe cardiac damage. Here, we briefly review the prevailing hypotheses on anthracycline-induced cardiotoxicity. We
also attempt to establish cause-and-effect relations between the structure of a given anthracycline and its cardiotoxicity
when administered as a single agent or during the course of multiagent chemotherapies. Finally, we discuss how the hypotheses
generated by preclinical models eventually translate into phase I–II clinical trials. 相似文献
4.
Expansion of transgenic tobacco protoplasts expressing pumpkin ascorbate oxidase is more rapid than that of wild-type protoplasts 总被引:10,自引:0,他引:10
When pumpkin (Cucurbita spp., cv. Ebisu Nankin) ascorbate oxidase cDNA was introduced into cultured cells of tobacco BY-2 (Nicotiana tabacum L. cv. Bright Yellow No. 2) by Agrobacterium-mediated transformation, the transgenic cells expressed and secreted the recombinant pumpkin ascorbate oxidase into the culture
medium. These transgenic cells showed no morphological difference from wild-type cells. However, in the presence of applied
hormones protoplasts prepared from the transgenic cells elongated more rapidly than those of wild-type cells. We propose that
ascorbate oxidase may play a key role in the regulation of cell expansion perhaps by controlling transport processes through
the plasma membrane, but not by affecting the cell wall.
Received: 28 October 1999 / Accepted: 18 January 2000 相似文献
5.
Sahún I Gallego X Gratacòs M Murtra P Trullás R Maldonado R Estivill X Dierssen M 《Amino acids》2007,33(4):677-688
Summary. Sensitivity to pharmacological challenges has been reported in patients with panic disorder. We have previously validated
transgenic mice overexpressing the neurotrophin-3 (NT-3) receptor, TrkC (TgNTRK3), as an engineered murine model of panic
disorder. We could determine that TgNTRK3 mice presented increased cellularity in brain regions, such as the locus ceruleus,
that are important neural substrates for the expression of anxiety in severe anxiety states. Here, we investigated the sensitivity
to induce anxiety and panic-related symptoms by sodium lactate and the effects of various drugs (the α2-adrenoceptor antagonist,
yohimbine and the adenosine antagonist, caffeine), in TgNTRK3 mice. We found enhanced panicogenic sensitivity to sodium lactate
and an increased intensity and a differential pattern of Fos expression after the administration of yohimbine or caffeine
in TgNTRK3. Our findings validate the relevance of the NT-3/TrkC system to pathological anxiety and raise the possibility
that a specific set of fear-related pathways involved in the processing of anxiety-related information may be differentially
activated in panic disorder. 相似文献
6.
Mühling J Nickolaus KA Halabi M Fuchs M Krüll M Engel J Wolff M Matejec R Langefeld TW Welters ID Menges T Dehne MG Sablotzki A Hempelmann G 《Amino acids》2005,29(3):289-300
Summary. The objective of this study was to determine the dose as well as duration of exposure-dependent effects of L-alanyl-L-glutamine,
arginine or taurine on polymorphonuclear neutrophil (PMN) free α-keto acid profiles and, in a parallel study, on PMN immune
functions. Exogenous L-alanyl-L-glutamine significantly increased PMN α-ketoglutarate, pyruvate PMN superoxide anion (O2−) generation, hydrogen peroxide (H2O2) formation and released myeloperoxidase (MPO) activity. Arginine also led to significant increases in α-ketoglutarate, pyruvate,
MPO release and H2O2 generation. Formation of O2− on the other hand was decreased by arginine. Incubation with taurine resulted in lower intracellular pyruvate and α-ketobutyrate
levels, decreased O2− and H2O2 formation and a concomitant significantly increased MPO activity. We therefore believe that considerable changes in PMN free-α-keto-acid
profiles, induced for example by L-alanyl-L-glutamine, arginine or taurine, may be one of the determinants in cell nutrition
that considerably modulates the immunological competence of PMN. 相似文献
7.
Summary. The subnuclear localization of nuclear protein is very important for in-depth understanding of the construction and function
of the nucleus. Based on the amino acid and pseudo amino acid composition (PseAA) as originally introduced by K. C. Chou can
incorporate much more information of a protein sequence than the classical amino acid composition so as to significantly enhance
the power of using a discrete model to predict various attributes of a protein, an algorithm of increment of diversity combined
with the improved quadratic discriminant analysis is proposed to predict the protein subnuclear location. The overall predictive
success rates and correlation coefficient are 75.4% and 0.629 for 504 single localization proteins in jackknife test, and
80.4% for an independent set of 92 multi-localization proteins, respectively. For 406 single localization nuclear proteins
with ≤25% sequence identity, the results of jackknife test show that the overall accuracy of prediction is 77.1%.
Authors’ address: Qian-Zhong Li, Laboratory of Theoretical Biophysics, Department of Physics, College of Sciences and Technology,
Inner Mongolia University, Hohhot 010021, China 相似文献
8.
Bongcam V MacDonald-Comber Petétot J Mittendorf V Robertson EJ Leech RM Qin YM Hiltunen JK Poirier Y 《Planta》2000,211(1):150-157
The peroxisome targeting signal (PTS) required for import of the rat acyl-CoA oxidase (AOX; EC 1.3.3.6) and the Candida tropicalis multifunctional protein (MFP) in plant peroxisomes was assessed in transgenic Arabidopsis thaliana (L.) Heynh. The native rat AOX accumulated in peroxisomes in A. thaliana cotyledons and targeting was dependent on the presence of the C-terminal tripeptide S-K-L. In contrast, the native C. tropicalis MFP, containing the consensus PTS sequence A-K-I was not targeted to plant peroxisomes. Modification of the carboxy terminus
to the S-K-L tripeptide also failed to deliver the MFP to peroxisomes while addition of the last 34 amino acids of the Brassica napus isocitrate lyase, containing the terminal tripeptide S-R-M, enabled import of the fusion protein into peroxisomes. These
results underline the influence of the amino acids adjacent to the terminal tripeptide of the C. tropicalis MFP on peroxisomal targeting, even in the context of a protein having a consensus PTS sequence S-K-L.
Received: 19 July 1999 / Accepted: 19 February 2000 相似文献
9.
Summary. The objective of this study was to assess the effect of taurine-depletion on cardiovascular responses of rat to vasoactive
agents. Male Wistar-Kyoto (WKY) rats were given either tap water (control) or 3% β-alanine (taurine-depleted) for three weeks.
Thereafter, mean arterial pressure (MAP) and heart rate of the freely moving animal were measured in response to vasoactive
agents. Administration of phenylephine (5–40 μg/kg/min; i.v.) resulted in a similar and significant increase in MAP but a
reduction in heart rate in both control and taurine-depleted groups. On the other hand, administration of sodium nitroprusside
(15–300 μg/kg/min; i.v.) elicited a similar and significant reduction in MAP but increased heart rate in both groups. Lack
of a differential response to phenylephrine and sodium nitroprusside between the two groups suggests that baroreflex regulation
of cardiovascular function is not adversely affected by taurine-depletion. Administration of angiotensin II (0.1–3.0 μg/kg/min;
i.v.) resulted in a dose-related increase in the pressor response and a decrease in heart rate in both groups. However, angiotensin
II-induced pressor response was reduced in the taurine-depleted compared to the control rats (p < 0.05); heart rate was similarly
reduced in both groups. Acute exposure to β-alanine (3 g/kg; i.v., 30-minutes) did not alter angiotensin II-induced hemodynamic
responses. Similarly, incubation of aortic rings with β-alanine (40 mM, 30 minutes) did not affect the contractile responses
to angiotensin II. The results suggest that β-alanine, per se, does not affect angiotensin II-induced responses in rat. However, β-alanine-induced taurine depletion is associated with
a reduction in the pressor response to angiotensin II without impairing baroreflex function.
Received December 17, 1999/Accepted January 12, 2000 相似文献
10.
Fast track to the trichome: induction of N-acyl nornicotines precedes nicotine induction in Nicotiana repanda 总被引:3,自引:0,他引:3
Nicotiana repanda Wildenow ex Lehmann acylates nornicotine in its trichomes to produce N-acyl-nornicotine (NacNN) alkaloids which are dramatically
more toxic than nicotine is to the nicotine-adapted herbivore, Manduca sexta. These NacNNs, like nicotine, were induced by methyl jasmonate (MeJA) and wounding, but the 2-fold increase in NacNN pools
was much faster (within 6 h) than the MeJA-induced increase in nornicotine pools (24 h to 4 d), its parent substrate. When
15NO3
− pulse-chase experiments with intact and induced plants were used to follow the incorporation of 15N into alkaloids in different plant parts over the plant's lifetime, it was found that the root nicotine pool was most rapidly
labeled, followed by the shoot nornicotine and NacNN pools. After 3 d, 3.12% of 15N acquired was in nicotine (0.93%), nornicotine (0.32%) and NacNNs (1.73%) while only 0.14% was in anabasine. Once NacNNs
are externalized to the leaf surface, they are not readily re-distributed within the plant and are lost with senescing leaves.
The wound- and MeJA-induced N-acylation of nornicotine is independent of induced changes in nornicotine pools and the rapidity
of the response suggests its importance in defense against herbivores.
Received: 3 July 1999 / Accepted: 17 September 1999 相似文献
11.
Summary. The premise that free amino acid or dipeptide based diets will resolve the nutritional inadequacy of formulated feeds for
larval and juvenile fish and improve utilization of nitrogen in comparison to protein-based diets was tested in stomachless
fish, common carp (Cyprinus carpio L.) larvae. We examined the postprandial whole body free amino acid (FAA) pool in fish that were offered a FAA mixture based
diet for the duration of 2 or 4 weeks. We found that the total amount and all indispensable amino acids concentrations in
the whole body decreased after a meal. We then fed juvenile carp with dietary amino acids provided in the FAA, dipeptide (PP),
or protein (live feed organisms; brine shrimp Artemia salina nauplii, AS) forms. Histidine concentrations in the whole fish body increased in all dietary groups after feeding whereas
all other indispensable amino acids decreased in FAA and PP groups in comparison to the AS group. Taurine appears to be the
major osmotic pressure balancing free amino acid in larval freshwater fish which may indicate a conditional requirement. We
present the first evidence in larval fish that in response to synthetic FAA and PP diets, the whole body indispensable free
AA concentrations decreased after feeding. This study shows that amino acids given entirely as FAA or PP cannot sustain stomachless
larval fish growth, and may result in depletion of body indispensable AA and most of dispensable AA. The understanding of
these responses will determine necessary changes in diet formulations that prevent accelerated excretion of amino acids without
protein synthesis. 相似文献
12.
Summary. Caffeine- and taurine-containing drinks have been on the European market for about a decade, and research on the individual
constituents of these drinks indicates an improvement in cognitive performance resulting from consumption of such drinks.
In this double-blind, placebo-controlled study using 10 graduate students, we obtained the P300 components of event-related
potential (ERP) waveforms following an auditory oddball paradigm, measured motor reaction time, and applied the d2 test for
the assessment of attention. Status of mood was assessed by the “Basler-Befindlichkeitsbogen” questionnaire, a standard test
for evaluation of feelings of well-being. Measurements were made at night, prior to and starting one hour after consumption
of energy drink ingredients or placebo.
At the end of the experiment (midnight), P300 latency and motor reaction time were significantly longer compared with baseline
measurements in the placebo group, but were unchanged in the energy drink group. In the test system for evaluating feelings
of well-being, total scores, vitality scores and social extrovertedness scores were significantly decreased in the placebo
group but not in the energy drink group.
The findings clearly indicate that the mixture of three key ingredients of Red BullR Energy Drink used in the study (caffeine, taurine, glucuronolactone) have positive effects upon human mental performance
and mood. These effects may be mediated by the action of caffeine on purinergic (adenosinergic) receptors and taurine modulation
of receptors. As half of the study cohort were non-caffeine users, the described effects cannot be explained in terms of the
restoration of plasma caffeine levels to normal following caffeine withdrawal.
Received January 5, 2000/Accepted June 5, 2000 相似文献
13.
Summary. Polyamines and the metabolic and physiopathological processes in which they are involved represent an active field of research
that has been continuously growing since the seventies. In the last years, the trends in the focused areas of interest within
this field since the 1970s have been confirmed. The impact of “-omics” in polyamine research remains too low in comparison
with its deep impact on other biological research areas. These high-throughput approaches, along with systems biology and,
in general, more systemic and holistic approaches should contribute to a renewal of this research area in the near future. 相似文献
14.
Increased transglutaminase activity was associated with IL-6 release in cultured human gingival fibroblasts exposed to dental cast alloys 总被引:1,自引:0,他引:1
Summary. Molecular mechanisms underlying gingival and periodontal inflammation caused by dental alloys are still poorly understood.
Recently, it has been demonstrated that tissue transglutaminase can be involved in inflammatory cell response. The aim of
this study was to evaluate effects of exposure to orthodontic materials on transglutaminase in cultured human gingival fibroblasts.
The incubation with Ni–Ti heat-activated (T3) or Ni–Ti super-elastic (T4), and with Ni–Cr–Co (T2) alloys produced respectively
2.5-fold and 8-fold increases in IL-6 release compared with control cultures. Transglutaminase activity was significantly
increased in cells exposed to T3 and T4 alloys (about 170% of control; p < 0.05), where it was mainly localized close to inner part of cell membrane. The exposure to T3 and T4 specimens significantly
up-regulated also tTG expression compared with control cultures. These data first show an association between IL-6 release
and tissue transglutaminase increases, suggesting that TGase-mediated reactions may play a major role in periodontal inflammation. 相似文献
15.
Marcocci L Casadei M Faso C Antoccia A Stano P Leone S Mondovì B Federico R Tavladoraki P 《Amino acids》2008,34(3):403-412
Summary. In this study, polyamine oxidase from maize (MPAO), which is involved in the terminal catabolism of spermidine and spermine
to produce an aminoaldehyde, 1,3-diaminopropane and H2O2, has been conditionally expressed at high levels in the nucleus of MCF-7 human breast cancer cells, with the aim to interfere
with polyamine homeostasis and cell proliferation. Recombinant MPAO expression induced accumulation of a high amount of 1,3-diaminopropane,
an increase of putrescine levels and no alteration in the cellular content of spermine and spermidine. Furthermore, recombinant
MPAO expression did not interfere with cell growth of MCF-7 cells under normal conditions but it did confer higher growth
sensitivity to etoposide, a DNA topoisomerase II inhibitor widely used as antineoplastic drug. These data suggest polyamine
oxidases as a potential tool to improve the efficiency of antiproliferative agents despite the difficulty to interfere with
cellular homeostasis of spermine and spermidine.
Authors’ address: Dr. Paraskevi Tavladoraki, Department of Biology, University ‘Roma Tre’, Viale G. Marconi 446, 00146 Rome,
Italy 相似文献
16.
Structural properties of proteins specific to the myelin sheath 总被引:1,自引:0,他引:1
Kursula P 《Amino acids》2008,34(2):175-185
Summary. The myelin sheath is an insulating membrane layer surrounding myelinated axons in vertebrates, which is formed when the plasma
membrane of an oligodendrocyte or a Schwann cell wraps itself around the axon. A large fraction of the total protein in this
membrane layer is comprised of only a small number of individual proteins, which have certain intriguing structural properties.
The myelin proteins are implicated in a number of neurological diseases, including, for example, autoimmune diseases and peripheral
neuropathies. In this review, the structural properties of a number of myelin-specific proteins are described.
Author’s address: Dr. Petri Kursula, Department of Biochemistry, University of Oulu, FIN-90014 Oulu, Finland 相似文献
17.
We develop a probabilistic model for the binding of a small linear polymer to a larger chain. We assume that we can approximate the energy of interaction of the two chains by summing the pairwise interactions between subunits. Because the energy of interaction between a pair of subunits can depend on neighboring subunits, which we assume vary along the chain, we assign the pairwise energies of interactions according to a specified probability distribution. Thus we develop a statistical model for the binding of two molecules. While such models may not be appropriate for studying the interaction of a particular pair of molecules, they can provide insight into questions that deal with populations of molecules, such as why do MHC molecules bind peptides of a certain size? Here we analyze in detail the special case of a heterodimer binding to a polymer. 相似文献
18.
Amino acid analysis by hydrophilic interaction chromatography coupled on-line to electrospray ionization mass spectrometry 总被引:1,自引:0,他引:1
Summary. Collagens form a common family of triple-helical proteins classified in 21 types. This unique structure is further stabilized
by specific hydroxylation of distinct lysyl and prolyl residues forming 5-hydroxylysine and hydroxyproline (Hyp) isomers,
mostly 4-trans and 3-trans-Hyp. The molecular distribution of the Hyp-isomers among the different collagen types is still
not well investigated, even though disturbances in the hydroxylation of collagens are likely to be involved in several diseases
such as osteoporosis and autoimmune diseases. Here, a new approach to analyze underivatized amino acids by hydrophilic interaction
chromatography (HILIC) coupled on-line to electrospray ionization mass spectrometry (ESI-MS) is reported. This method can
separate all three studied Hyp-isomers, Ile, and Leu, which are all isobaric, allowing a direct qualitative and quantitative
analysis of collagen hydrolysates. The sensitivity and specificity was increased by a neutral loss scan based on the loss
of formic acid (46 u). 相似文献
19.
Summary. This study evaluated whether cycloheximide, an inhibitor of protein synthesis, would affect the binding of L-tryptophan to
rat hepatic nuclei or nuclear envelopes. Previous reports have indicated that the binding of L-tryptophan to hepatic nuclear
envelope protein was saturable, stereospecific, and of high affinity. Also, the administration of L-tryptophan rapidly stimulated
hepatic protein synthesis. In this study, we determined that the addition of cycloheximide in vitro inhibited 3H-tryptophan binding to hepatic nuclei or nuclear envelopes. Heat-treated cycloheximide failed to have this inhibitory binding
effect. In vivo treatment of rats with cycloheximide diminished in vitro 3H-tryptophan binding to hepatic nuclei of treated rats compared to controls. Puromycin, another inhibitor of hepatic protein
synthesis, when added in vitro did not affect 3H-tryptophan binding to hepatic nuclei but did diminish in vitro binding after in vivo treatment. Thus, cycloheximide added
in vitro diminished 3H-tryptophan binding to hepatic nuclei probably by its structural effect on the receptor while cycloheximide administered
in vivo may also act in part by inhibiting protein synthesis.
Received March 22, 1999, Accepted May 31, 1999 相似文献