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Received: 1 July 1996 / Revised: 10 July 1996 相似文献
3.
Class I major histocompatibility complex (Mhc) cDNA clones were isolated from axolotl mRNA by polymerase chain reaction (PCR) and by screening a cDNA phage library. The
nucleotide and predicted amino acid sequences show definite similarities to the Mhc class Iα molecules of higher vertebrates.
Most of the amino acids in the peptide binding region that dock peptides at their N and C termini in mammals are conserved.
Several amino acids considered to be important for the interaction of β2-microglobulin with the Mhc α chain are also conserved in the axolotl sequence. The fact that axolotl class I A cDNAs are
ubiquitously expressed and highly polymorphic in the α1 and α2 domains suggests the classical nature of axolotl class I A
genes.
Received: 3 June 1996 / Revised: 14 October 1996 相似文献
4.
J. Sánchez-Torres P. Pérez R. I. Santamaría 《Applied microbiology and biotechnology》1996,46(2):149-155
Several alkalophilic Bacillus spp. strains were selected for their capacity to produce alkaline cellulases. Culture supernatants of these strains showed
optimal cellulase activities between pH 8 and 9 and they were stable from pH 6 to pH 12. A cellulase gene (celB1) from the alkalophilic Bacillus sp. strain N186-1 was cloned in Escherichia coli using polymerase chain reaction techniques. The cloned gene was present in a 2.539-bp HindIII fragment and its nucleotide sequence was determined. The coding sequence showed an open-reading frame encoding 389 amino
acids. The amino acid sequence, deduced from the nucleotide sequence, permitted us to include it in family 5 (or A) of the
glycosyl hydrolases. The complete open-reading frame of celB1 was cloned in the plasmid pET-11d and expressed in E. coli BL21 (DE3), in which a protein of 39 kDa was obtained in the cytoplasm; however, no endoglucanase activity was detected.
A second construction in pET-12a allowed the production of a 39-kDa protein located in the periplasmic space of E. coli that had endoglucanase activity. The protein produced has optimal activity at pH 7 and 50°C and it retains more than 70%
of its activity after incubation for 1 h at pH 12.
Received: 27 December 1995/Received revision: 14 March 1996/Accepted: 25 March 1996 相似文献
5.
Eight compounds exuded from young roots of black locust (Robinia pseudoacacia) were separated by two-dimensional HPTLC, by HPLC and GC, and were identified by spectroscopic methods (ultraviolet/visible
spectroscopy and mass spectrometry) as 4′,7-dihydroxyflavone, apigenin, naringenin, chrysoeriol and isoliquiritigenin. Structural
assignments were confirmed by comparison with authentic standards. The capacity to induce β-galactosidase activity in Rhizobium sp. NGR234 containing a nod box::lacZ fusion on plasmid pA27 identified these flavonoids and the chalcone as nod gene inducers. This indicates the important role of these compounds in nodulation of this legume tree.
Received: 26 July 1996 / Accepted: 9 September 1996 相似文献
6.
J. M. Crous I. S. Pretorius W. H. van Zyl 《Applied microbiology and biotechnology》1996,46(3):256-260
First-strand cDNA was prepared from mRNA of Aspergillus niger MRC11624 induced on oat spelts xylan. Using the cDNA as a template, the α-L-arabinofuranosidase gene (abf B) was amplified with the polymerase chain reaction technique. The abf B DNA fragment was inserted between the yeast phosphoglycerate kinase I gene promoter (PGK1
P
) and terminator (PGK1
T
) sequences on a multicopy episomal plasmid. The resulting construct PGK1
P
-abf B-PGK1
T
was designated ABF2. The ABF2 gene was expressed successfully in Saccharomyces cerevisiae and functional α-L-arabinofuranosidase was secreted from the yeast cells. The ABF2 nucleotide sequence was determined and verified to encode a 449-amino-acid protein (Abf 2) that is 94% identical to the α-L-arabinofuranosidase B of A. niger N400. Maximum α-L-arabinofuranosidase activities of 0.020 U/ml and 1.40 U/ml were obtained with autoselective recombinant S. cerevisiae strains when grown for 48 h in synthetic and complex medium respectively.
Received: 29 January 1996/Received revision: 3 May 1996/Accepted: 9 May 1996 相似文献
7.
Use of an industrial effluent as a carbon source for denitrification of a high-strength wastewater 总被引:6,自引:0,他引:6
Denitrification of a high-strength synthetic wastewater (150 g NO-
3 l-1) was carried out using a wine distillery effluent as an example of an industrial carbon source (22.7 g chemical oxygen demand
l-1). Two configurations were tested: one consisted of an acidogenesis reactor followed by a denitrifying reactor and the other
was a single reactor directly fed with the raw effluents. In both cases, denitrification was achieved at a nitrate load of
9.54 g NO-
3 l-1 day-1 (2.19 g N as NO-
3 l-1 day-1) with good specific reduction rates: 32.6 mg and 35.2 mg N as NO
x
g volatile suspended solids h-1, calculated on a single day, for the two-step and the one-step process respectively. Dissimilatory nitrate reduction to ammonium
did not occur, even in the one-step process.
Received: 26 October 1995/Received revision: 15 February 1996/Accepted: 20 February 1996 相似文献
8.
Segments of standing beech stems (Fagus sylvatica) were put under mechanical pressure from the end of May, in order to investigate the influence of constant external pressure
on the development of secondary vascular tissue. After 4 weeks, the new xylem increment was investigated anatomically in cross-sections.
The first axial xylem derivatives of the new year’s increment had differentiated into normal vessel elements and fiber-tracheids.
Application of the pressure girdle had no effect on fiber-tracheid development, but it inhibited vessel formation. Under pressure,
changes in the two dimensional PAGE protein pattern were characterized by the appearance of two new protein species as well
as by the absence of one species that occurs under regular growth.
Received: 7 June 1996 / Accepted: 14 November 1996 相似文献
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Vertical resin duct density in spruce tree-rings was used as a dendroclimatological variable and compared with radial growth.
Resin duct density data were statistically stable and distributed with higher mean sensitivity and standard deviation but
lower signal-to-noise rate than the corresponding growth rate. Radial growth and resin duct density relationships with climate
were investigated using correlation and response function analysis. It was found that resin duct density has a significant
positive response to above-normal temperature especially from June to August and a less significant negative response for
above-normal precipitation from May – July during the current growing season. Ring width showed a significant negative response
to above-normal precipitation from June to August but no response with temperature. Ring width and resin duct density were
not related to each other. Sufficient data indicate that vertical resin duct density is a useful variable for dendroclimatology.
Received: 14 March 1996 / Accepted: 24 June 1996 相似文献
11.
Cecilie Boysen Christopher Carlson Eran Hood Leroy Hood Deborah A. Nickerson 《Immunogenetics》1996,44(2):121-127
The T-cell receptor (TCR) is a highly variable molecule composed of two polypeptide chains that recognize antigenic peptides
in the context of major histocompatibility complex (MHC) molecules. In this study, we describe a sequence-based search for
germline polymorphisms in the variable (V) gene segments of the human TCRA/D locus. Thirty different V gene segments were amplified from six to eight unrelated individuals and sequenced from low melting point agarose. Twenty-seven
polymorphisms were identified in 15 V gene segments. These polymorphisms are mainly single nucleotide substitutions, but an insertion/deletion polymorphism and
a single dinucleotide repeat with variable length were also seen. Of the 15 sequence variations found in the coding regions,
six are silent and nine encode amino acid changes. All of the amino acid changes are found at non-conserved residues, frequently
in the hypervariable regions, where they may influence MHC and/or peptide recognition. Therefore, it is possible that germline
variations in TCR genes could influence an individual’s immune response, and may also contribute to susceptibility to diseases such as autoimmunity.
Received: 9 January 1996 / Revised: 22 February 1996 相似文献
12.
Morphology and ecological significance of intra-annual radial cracks in living conifers 总被引:3,自引:0,他引:3
P. Cherubini Fritz Hans Schweingruber Theodor Forster 《Trees - Structure and Function》1997,11(4):216-222
Intra-annual radial cracks were studied on 294 cross-sections of Norway spruce sampled at two forest sites in the eastern
Alps (Italy) and from seven isolated trees in the Jura region (Switzerland). Cracks were occasionally accompanied by traumatic
resin canals in the wood that was formed after the cracking. Most of the cracks, however, were without such canals. Traumatic
resin canals are not significantly more abundant in tree rings formed after cracking, and their occurrence is not related
to the cracking. Cracks developed when the cambium was inactive. Water imbalances during the early spring, due to transpiration
losses and inadequate moisture supply from very cold roots, are the likely cause of these cracks.
Received: 21 February 1996 / Accepted: 14 June 1996 相似文献
13.
Tsukasa Sato Yasuhiko Midorikawa Takao Yamashita Akemi Araki F. Sendo 《Cancer immunology, immunotherapy : CII》1996,43(2):77-86
Effective treatment of a rat transplanted ascites tumor by i. p. injection of a streptococcal biological response modifier,
OK-432, was abrogated by selective in vivo depletion of neutrophils by a monoclonal antibody, RP-3. The mechanisms by which
neutrophils participate in the therapeutic action of OK-432 were studied with Winn’s assay using peritoneal exudate cells
periodically obtained from rats i. p. injected with this biological response modifier. Intraperitoneal resident macrophages
were first activated with OK-432, and within 3 h, tumor-inhibitory activity had moved to the early exuded neutrophils. However,
6 h after injection, exuded macrophages were the only cells involved in tumor inhibition. Considered together with other findings,
it is likely that, in this system, neutrophils may transmit information from resident macrophages to exuded inflammatory macrophages
in a series of responses induced by i. p. injection of OK-432.
Received: 29 April 1996 / Accepted: 27 July 1996 相似文献
14.
Larry M. Rose A. H. Gunasekera Sally J. DeNardo Gerald L. DeNardo C. F. Meares 《Cancer immunology, immunotherapy : CII》1996,43(1):26-30
The selectivity of Lym-1 for malignant B lymphocytes makes this monoclonal antibody a promising candidate for the delivery
of toxic agents to malignant B cells. The original immunogen used for the development of Lym-1 was Raji Burkitt’s lymphoma
cell nuclei [Epstein A. L., Marder R. J., Winter J. N., Stathopoulos E., Chen F. M., Parker J. W., Taylor C. R. (1987) Cancer
Res 47: 830]. The Lym-1 antigen was characterized at that time as a polymorphic HLA-DR variant. We prepared an affinity column
using immobilized Lym-1 to isolate the Lym-1 antigen from Raji cell lysate. Immunological characterization of the immunoaffinity-purified
Lym-1 antigen on Western blots led to the conclusion that the antigen is the β chain of HLA-DR10. This was confirmed by Edman
sequencing of the isolated polypeptide chain. Western blots further show that the Lym-1 epitope is only recognized if the
β chain disulfide bonds are intact. These results imply that Lym-1 binds a discontinuous epitope on the β chain of HLA-DR10.
Received: 22 February 1996 / Accepted: 28 June 1996 相似文献
15.
The plant cytoskeleton has been implicated in a variety of morphogenetic events in higher plants. Most of this work, however,
has concentrated on epidermal cells or primary tissues. We have investigated the cortical microtubular (CMT) and microfilament
(MF) components of the cytoskeleton in a secondary tissue – active vascular cambium of Aesculus hippocastanum L. (horse-chestnut) – and followed the changes in these components during the early stages of differentiation of fusiform
cambial derivatives to axial elements of the secondary vascular system. A correlative approach was used employing indirect
immunofluorescence microscopy of α-tubulin on 6 μm sections, and transmission electron microscopy of 60 nm sections. The study
has demonstrated a rearrangement of the CMT cytoskeleton, from random to helical, as fusiform vascular cambial cells begin
to differentiate as secondary phloem vascular tissue. A similar CMT rearrangement is seen as fusiform cambial cells begin
to differentiate as secondary xylem fibres. This rearrangement is interpreted as evidence of determination of cambial derivatives
towards vascular development. Axially-oriented MF bundles are present in fusiform cambial cells and their axial orientation
is retained in the vascular derivatives at early stages of their development even though the CMTs have become rearranged.
Received: 5 August 1996 / Accepted: 23 September 1996 相似文献
16.
H. Sztajer W. Wang H. Lünsdorf A. Stocker R. D. Schmid 《Applied microbiology and biotechnology》1996,45(5):600-606
Geotrichum candidum was found to produce a lactate oxidase. The enzyme was purified by gel filtration and ion-exchange chromatography. The purified
lactate oxidase showed a molecular mass of 50 kDa under denaturing and about 400 kDa under non-denaturing conditions. Transmission
electron micro-scopy analysis confirmed an octameric structure. FMN was found to be a cofactor for this enzyme. Polarographic
studies confirmed an oxygen uptake by the lactate oxidase. The enzyme showed specificity towards the L isomer of lactate and
did not oxidise pyruvate, fumarate, succinate, maleate and ascorbate. It was stable at alkaline pH and also for 15 min at
45°C. The addition of glycerol and dextran 500 000 to the enzyme sample enhanced storage stability.
Received: 28 September 1995/Received revision: 10 January 1996/Accepted: 15 January 1996 相似文献
17.
β-Fructofuranosidase was purified from commercial alkaline protease (Aspergillus oryzae origin). The optimal pH of its transfructosylating activity was more alkaline (pH 8) than that of its hydrolyzing activity
(pH 5). In the case of a 24-h reaction with sucrose, the hydrolysis and transfructosylation reaction were optimal at pH 4–5
and pH 8, respectively. In the reaction at pH 8 1-kestose and nystose were the main fructooligosaccharides produced. The transfer
ratio was hardly different between pH 5 and pH 8 early in the reaction, but the transfer products (1-kestose and nystose)
were decreased at pH 5 as the reaction proceeded because of their hydrolysis.
Received: 18 January 1995/Received last revision: 23 August 1995/Accepted: 13 September 1995 相似文献
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S. E. Harrington H. F. J. Bligh W. D. Park C. A. Jones S. R. McCouch 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,94(5):564-568
The chromosomal position of Starch Branching Enzyme III (SBEIII) was determined via linkage to RFLP markers on an existing
molecular map of rice (Oryza sativa L.). A cDNA of 890 bp was generated using specific PCR primers designed from available SBEIII sequence data and used as a
probe in Southern analysis. The SBEIII cDNA hybridized to multiple restriction fragments, but these fragments mapped to a
single locus on rice chromosome 2, flanked by CDO718 and RG157. The detection of a multiple-copy hybridization pattern suggested the possibility of a tandemly duplicated gene at this
locus. The map location of orthologous SBE genes in maize, wheat, and oat were predicted based on previously published genetic
studies and comparative maps of the grass family.
Received : 5 August 1996 / Accepted : 13 September 1996 相似文献
20.
Southern analysis of Eco RI-digested BALB/c liver DNA reveals four T-cell receptor Tcra-V3-hybridizing DNA fragments, which are of sizes 18.0, 12.0, 8.0, and 2.1 kilobases, respectively. These four Tcra-V3-hybridizing genomic DNA were isolated from a BALB/c genomic library. Restriction and Southern analysis of the genomic DNA
clones showed that each of the Tcra-V3-hybridizing Eco RI DNA fragments harbors only a single Tcra-V3 gene. The DNA sequences of coding regions of the four Tcra-V3 family members were determined. These sequences show very limited divergence from one another. Comparisons of BALB/c Tcra-V3 sequences with published Tcra-V3 sequences expressed in different strains of mice reveal substantial allelic polymorphism. Sequence similarity searches retrieved
homologous rat, cattle, and human genes. The scarcity of coding sequence divergence among members of the Tcra-V3 family and the more substantial allelic polymorphism may be general features of the T-cell receptor V-alpha chain-encoding
gene families.
Received: 11 April 1996 / Revised: 26 May 1996 相似文献