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21.
Trees represent a unique life form of upmost importance for mankind, as these organisms have developed a perennial lifestyle that produces the majority of terrestrial biomass. The difference between trees and annual plants is one of the main arguments behind the effort to sequence the entire genome of the poplar tree. This initiative is being backed up with a full-scale functional genomics effort on trees that will set a completely new agenda for forest research. 相似文献
22.
Gupta SK Singh PK Sawant SV Chaturvedi R Tuli R 《Indian journal of experimental biology》2000,38(4):399-401
Cotyledonary nodes taken alongwith shoot apex from seedlings of cotton (G. hirsutum) proliferated into shoots on nutrient agar medium supplemented with cytokinins. In the presence of optimal plant growth regulators, low light intensity enhanced the number of shoots initiated per explant in cotton. An average of 33.5 +/- 2.9 shoots were obtained from a single explant cultured for 8 weeks which is about four fold higher than the values reported in earlier protocols. The isolated shoots were rooted on nutrient agar medium supplemented with alpha-naphthalene acetic acid and transferred to soil after acclimatization. Regenerated plants were morphologically identical to the seed-germinated plants and were fertile. 相似文献
23.
Expression of tissue kallikrein and kinin receptors in angiogenic microvascular endothelial cells 总被引:5,自引:0,他引:5
Plendl J Snyman C Naidoo S Sawant S Mahabeer R Bhoola KD 《Biological chemistry》2000,381(11):1103-1115
Angiogenesis is the sprouting of new capillary blood vessels from pre-existing ones. The kinin family of vasoactive peptides, formed by the serine protease tissue kallikrein from its endogenous multifunctional protein substrate kininogen, is believed to regulate the angiogenic process. The aim of this study was to determine the expression of tissue kallikrein and kinin receptors in an in vitro model of angiogenesis. Microvascular endothelial cells from the bovine mature and regressing corpus luteum were used only if they reacted with known endothelial cell markers. At first the cultured endothelial cells began sprouting, and within four weeks formed three-dimensional, capillary-like structures. Immunolabelling for tissue prokallikrein and the mature enzyme was intense in the angiogenic endothelial cells derived from mature corpora lutea. Immunoreactivity was lower in non-angiogenic endothelial cells and least in angiogenic endothelial cultures of the regressing corpus luteum. Additionally, using specific antisense DIG-labelled probes, tissue kallikrein mRNA was demonstrated in cells of the angiogenic phenotype. Immunolabelled kinin B2 receptors, but not kinin B1 receptors, were visualised on angiogenic endothelial cells. Our results suggest an important regulatory role for kinins in the multiple steps of the angiogenic cascade that may occur in wound healing and cancer cell growth. 相似文献
24.
25.
Anders ?stin Mariusz Kowalyczk Rishikesh P. Bhalerao G?ran Sandberg 《Plant physiology》1998,118(1):285-296
The metabolism of indole-3-acetic
acid (IAA) was investigated in 14-d-old Arabidopsis plants grown in
liquid culture. After ruling out metabolites formed as an effect of
nonsterile conditions, high-level feeding, and spontaneous
interconversions, a simple metabolic pattern emerged. Oxindole-3-acetic
acid (OxIAA), OxIAA conjugated to a hexose moiety via the carboxyl
group, and the conjugates indole-3-acetyl aspartic acid (IAAsp) and
indole-3-acetyl glutamate (IAGlu) were identified by mass spectrometry
as primary products of IAA fed to the plants. Refeeding experiments
demonstrated that none of these conjugates could be hydrolyzed back to
IAA to any measurable extent at this developmental stage. IAAsp was
further oxidized, especially when high levels of IAA were fed into the
system, yielding OxIAAsp and OH-IAAsp. This contrasted with the
metabolic fate of IAGlu, since that conjugate was not further
metabolized. At IAA concentrations below 0.5 μm, most of
the supplied IAA was metabolized via the OxIAA pathway, whereas only a
minor portion was conjugated. However, increasing the IAA
concentrations to 5 μm drastically altered the metabolic
pattern, with marked induction of conjugation to IAAsp and IAGlu. This
investigation used concentrations for feeding experiments that were
near endogenous levels, showing that the metabolic pathways controlling
the IAA pool size in Arabidopsis are limited and, therefore, make good
targets for mutant screens provided that precautions are taken to avoid
inducing artificial metabolism.The plant hormone IAA is an important signal molecule in the
regulation of plant development. Its central role as a growth regulator
makes it necessary for the plant to have mechanisms that strictly
control its concentration. The hormone is believed to be active
primarily as the free acid, and endogenous levels are controlled in
vivo by processes such as synthesis, oxidation, and conjugation. IAA
has been shown to form conjugates with sugars, amino acids, and small
peptides. Conjugates are believed to be involved in IAA transport, in
the storage of IAA for subsequent use, in the homeostatic control of
the pool of the free hormone, and as a first step in the catabolic
pathways (Cohen and Bandurski, 1978; Nowacki and Bandurski, 1980;
Tuominen et al., 1994; Östin et al., 1995; Normanly, 1997). It is
generally accepted that in some species conjugated IAA is the major
source of free IAA during the initial stages of seed germination (Ueda
and Bandurski, 1969; Sandberg et al., 1987; Bialek and Cohen, 1989),
and there is also evidence that in some plants (but not all; see Bialek
et al., 1992), the young seedling is entirely dependent on the release
of free IAA from conjugated pools until the plant itself is capable of
de novo synthesis (Epstein et al., 1980; Sandberg et al., 1987).The function of conjugated IAA during vegetative growth is somewhat
less clear. It has been shown that conjugated IAA constitutes as much
as 90% of the total IAA in the plant during vegetative growth
(Normanly, 1997). However, the role of the IAA conjugates at this stage
of the plant''s life cycle remains unknown. Analysis of endogenous IAA
conjugates in vegetative tissues has revealed the presence of a variety
of different compounds, including indole-3-acetyl-inositol,
indole-3-acetyl-Ala, IAAsp, and IAGlu (Anderson and Sandberg, 1982;
Cohen and Baldi, 1983; Chisnell, 1984; Cohen and Ernstsen, 1991;
Östin et al., 1992). Studies of vegetative tissues have indicated
that IAAsp, one of the major conjugates in many plants, is the first
intermediate in an irreversible deactivation pathway (Tsurumi and Wada,
1986; Tuominen et al., 1994; Östin, 1995). Another mechanism that
is believed to be involved in the homeostatic control of the IAA pool
is catabolism by direct oxidation of IAA to OxIAA, which has been shown
to occur in several plant species (Reinecke and Bandurski, 1983;
Ernstsen et al., 1987).One area in the study of IAA metabolism in which our knowledge is
increasing is the analysis of the homeostatic controls of IAA levels in
plants. It has been possible, for instance, to increase the levels of
IAA in transgenic plants expressing iaaM and iaaH
genes from Agrobacterium tumefaciens. Analysis of these
transgenic plants has indicated that plants have several pathways that
can compensate for the increased production of IAA (Klee et al., 1987;
Sitbon, 1992). It is expected that future studies using now-available
genes will provide further insight into IAA metabolism. For example, a
gene in maize encoding IAA-Glc synthetase has been identified, and
several genes (including ILR1, which may be involved
in hydrolysis of the indole-3-acetyl-Leu conjugate) have been cloned
from Arabidopsis (Szerszen et al., 1994; Bartel and Fink,
1995). Furthermore, Chou et al. (1996) identified a gene that
hydrolyzes the conjugate IAAsp to free IAA in the bacterium
Enterobacter aggloremans.Because of its small genome size, rapid life cycle, and the ease of
obtaining mutants, Arabidopsis is increasingly used as a
genetic model system to investigate various aspects of plant growth and
development. IAA signal transduction is also being investigated
intensively in Arabidopsis in many laboratories (Leyser, 1997). Mutants
with altered responses to externally added auxins or IAA conjugates
have been identified in Arabidopsis. The identified mutants are either
signal transduction mutants such as axr1-4 (Lincoln et al.,
1990), or have mutations in genes involved in auxin uptake or
transport, such as aux1 and pin1 (Okada et al.,
1991; Bennett et al., 1996). A few mutants that are unable to regulate
IAA levels or are unable to hydrolyze IAA conjugates, sur1-2
and ilr1, respectively, have also been identified (Bartel
and Fink, 1995; Boerjan et al., 1995). To our knowledge, no mutant that
is auxotrophic for IAA has been identified to date, which may
reflect the redundancy in IAA biosynthetic pathways or the lethality of
such mutants.In spite of the work reported thus far, many aspects of the metabolism
of IAA in Arabidopsis require further investigation, because few
details of the processes involved in IAA regulation are known. This
lack of knowledge puts severe constraints on genetic analysis of IAA
metabolism in Arabidopsis. For example, it is essential to have prior
knowledge of IAA metabolism to devise novel and relevant screens with
which to identify mutants of IAA metabolism. We have sought to address
this issue by identifying the metabolic pathways involved in catabolism
and conjugation under conditions that minimally perturb physiological
processes. In this investigation we studied the conjugation and
catabolic pattern of IAA by supplying relatively low levels of labeled
IAA and identifying the catabolites and conjugates by MS. Different
feeding systems were tested to optimize the application of IAA and to
avoid irregularities in metabolism attributable to culturing, feeding
conditions, or microbial activity. It is well documented that IAA
metabolism is altered according to the amount of exogenous auxin
applied; therefore, we placed special emphasis on distinguishing
between catabolic routes that occur at near-physiological
concentrations and those that occur at the high auxin concentrations
commonly used in mutant screens. 相似文献
26.
27.
Thomas McNerney Anne Thomas Anna Senczuk Krista Petty Xiaoyang Zhao Rob Piper Juliane Carvalho Matthew Hammond Satin Sawant Jeanine Bussiere 《MABS-AUSTIN》2015,7(2):413-427
High titer (>10 g/L) monoclonal antibody (mAb) cell culture processes are typically achieved by maintaining high viable cell densities over longer culture durations. A corresponding increase in the solids and sub-micron cellular debris particle levels are also observed. This higher burden of solids (≥15%) and sub-micron particles typically exceeds the capabilities of a continuous centrifuge to effectively remove the solids without a substantial loss of product and/or the capacity of the harvest filtration train (depth filter followed by membrane filter) used to clarify the centrate. We discuss here the use of a novel and simple two-polymer flocculation method used to harvest mAb from high cell mass cell culture processes. The addition of the polycationic polymer, poly diallyldimethylammonium chloride (PDADMAC) to the cell culture broth flocculates negatively-charged cells and cellular debris via an ionic interaction mechanism. Incorporation of a non-ionic polymer such as polyethylene glycol (PEG) into the PDADMAC flocculation results in larger flocculated particles with faster settling rate compared to PDADMAC-only flocculation. PDADMAC also flocculates the negatively-charged sub-micron particles to produce a feed stream with a significantly higher harvest filter train throughput compared to a typical centrifuged harvest feed stream. Cell culture process variability such as lactate production, cellular debris and cellular densities were investigated to determine the effect on flocculation. Since PDADMAC is cytotoxic, purification process clearance and toxicity assessment were performed. 相似文献
28.
29.
Mehar H. Asif Shrikant S. Mantri Ayush Sharma Anukool Srivastava Ila Trivedi Priya Gupta Chandra S. Mohanty Samir V. Sawant Rakesh Tuli 《Tree Genetics & Genomes》2010,6(6):941-952
Jatropha curcas is an important non-edible oil seed tree species and is considered a promising source of biodiesel. The complete nucleotide
sequence of J. curcas chloroplast genome (cpDNA) was determined by pyrosequencing and gaps filled by Sanger sequencing. The cpDNA is a circular
molecule of 163,856 bp in length and codes for 110 distinct genes (78 protein coding, four rRNA and 28 distinct tRNA). Genome
organisation and arrangement are similar to the reported angiosperm chloroplast genome. However, in Jatropha, the infA and the rps16 genes are non-functional. The inverted repeat (IR) boundary is within the rpl2 gene, and the 13 nucleotides at the ends of the two duplicate genes are different. Repeat analysis suggests the presence
of 72 repeat regions (>30 bp) apart from the IR; of these, 48 were direct and 24 were palindromic repeats. Phylogenetic analysis
of 81 protein coding chloroplast genes from 65 taxa by maximum parsimony, maximum likelihood and minimum evolution analyses
at 100 bootstraps provide strong support for the placement of inaperturate crotonoids of which Jatropha is a member as sister to articulated crotonoids of which Manihot is a member. 相似文献
30.
The present investigation was aimed at developing cytarabine-loaded poly(lactide-coglycolide) (PLGA)-based biodegradable nanoparticles
by a modified nanoprecipitation which would have sustained release of the drug. Nine batches were prepared as per 32 factorial design to optimize volume of the co-solvent (0.22–0.37 ml) and volume of non-solvent (1.7–3.0 ml). A second 32 factorial design was used for optimization of drug: polymer ratio (1:5) and stirring time (30 min) based on the two responses,
mean particle size (125 ± 2.5 nm), and percentage entrapment efficiency (21.8 ± 2.0%) of the Cyt-PLGA nanoparticles. Optimized
formulation showed a zeta potential of −29.7 mV indicating good stability; 50% w/w of sucrose in Cyt-PLGA NP was added successfully as cryoprotectant during lyophilization for freeze-dried NPs and showed
good dispersibility with minimum increase in their mean particle sizes. The DSC thermograms concluded that in the prepared
PLGA NP, the drug was present in the amorphous phase and may have been homogeneously dispersed in the PLGA matrix. In vitro drug release from the pure drug was complete within 2 h, but was sustained up to 24 h from PLGA nanoparticles with Fickian
diffusion. Stability studies showed that the developed PLGA NPs should be stored in the freeze-dried state at 2–8°C where
they would remain stable in terms of both mean particle size and drug content for 2 months. 相似文献