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21.
Regulation of type VI collagen synthesis in transformed mesenchymal cells. 总被引:3,自引:0,他引:3
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We have analysed the effects of oncogenic transformation on the expression of type VI collagen in mesenchymal cells. Synthesis of type VI collagen was almost completely inhibited in fibroblasts transformed by DNA or RNA tumour viruses or in cells derived from spontaneous mesenchymal tumours. Inhibition of type VI collagen synthesis appears, therefore, to be a common phenomenon of transformed mesenchymal cells. When introduced into normal cells by viral vectors, the 'nuclear' oncogene v-myc had an inhibitory effect similar to that of the 'cytoplasmic' oncogene v-src. Fibroblasts infected with a temperature-sensitive strain of Rous sarcoma virus (NY68) produced type VI collagen at the restrictive, but not at the permissive temperature. If such cells were shifted from the permissive to the restrictive temperature, synthesis of the individual subunits of type VI collagen was co-ordinately induced. These results demonstrate that the activity of a single oncogene product is sufficient to inhibit type VI collagen expression. 相似文献
22.
Hans Georg B?umert Akitsugu Kenmoku Gert Middelhoff Franz Ortanderl Alexander Thrun Heinz Faulstich Wolfgang Schiebler Hugo Fasold 《Journal of Protein Chemistry》1988,7(5):571-580
With the aid of tartryl-bis--aminocaprylazide artificial dimers were produced from F actin from rabbit striated muscle. These derivatives will not polymerize by themselves but are able to copolymerize fully with native G actin. By modification of a single side chain per dimer, this copolymerization was completely inhibited. The dimers are able to activate subfragment I ATPase of myosin and bind to DNase I with inactivation of the enzyme in the same manner as native G actin. Within the dimer, one ADP is immobilized and will exchange against ATP extremely slowly. The dimers do not bind to the mushroom toxin phalloidin. 相似文献
23.
Hasenstein, K. H. and Evans, M. L. 1988. The influence of calcium and pH on growth in primary roots of Zea mays. - Physiol. Plant. 72: 466–470.
We investigated the interaction of Ca2+ and pH on root elongation in Zea mays L. cv. B73 × Missouri 17 and cv. Merit. Seedlings were raised to contain high levels of Ca2+ (HC, imbibed and raised in 10 m M CaCl2 ) or low levels of Ca2+ (LC, imbibed and raised in distilled water). In HC roots, lowering the pH (5 m M MES/Tris) from 6.5 to 4.5 resulted in strong, long-lasting growth promotion. Surprisingly, increasing the pH from 6.5 to 8.5 also resulted in strong growth promotion. In LC roots acidification of the medium (pH 6.5 to 4.5) resulted in transient growth stimulation followed by a gradual decline in the growth rate toward zero. Exposure of LC roots to high pH (pH shift from 6.5 to 8.5) also promoted growth. Addition of EGTA resulted in strong growth promotion in both LC and HC roots. The ability of EGTA to stimulate growth appeared not to be related to H+ release from EGTA upon Ca2+ chelation since, 1) LC roots showed a strong and prolonged response to EGTA, but only a transient response to acid pH, and 2) promotion of growth by EGTA was observed in strongly buffered solutions. We also examined the pH dependence of the release of 45 Ca2+ from roots of 3-day-old seedlings grown from grains imbibed in 45 Ca2+ . Release of 45 Ca2+ from the root into agar blocks placed on the root surface was greater the more acidic the pH of the blocks. The results indicate that Ca2+ may be necessary for the acid growth response in roots. 相似文献
We investigated the interaction of Ca
24.
25.
A long-range repeat family of more than 50 kb repeat size is clustered in Chromosomes (Chr) 1 of Mus musculus and M. spretus. In M. musculus this long-range repeat family shows considerable variation of copy-number frequency and contains coding regions for at least two genes. In an intron of a gene, which is part of the repeat, a B2 small interspersed repetitive element (SINE) is inserted at identical positions. The B2 element is present in all copies of the long-range repeat family; it was presumably a component of the ancestral single-copy precursor sequence that gave rise by amplification to the repeat family. Copies of the long-range repeat family vary with respect to the number of TAAA tandem repeats in the A-rich 3 end region of the B2 element. As inferred from polymerase chain reaction (PCR) data, presence and frequency of repeat number variants in the (TAAA)n block are strain and species specific. The B2 element and its flanking regions were sequenced from two copies of the long-range repeat family. Sequence divergence between the two copies (only non-CG base substitutions and deletions/insertions) was determined to be 2.6%. Based on the drift rate in human Alu elements and a correction for the higher drift rates in rodents, and estimate for the divergence time of 1.7 million years was calculated. Since the long-range repeat family is present in M. musculus and M. spretus, it must have evolved by amplification before the separation of the two species about 1–4 million years ago. 相似文献
26.
M. Heinz R. Krattenmacher B. Hoffmann W. Clauss 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1991,161(4):363-370
Summary Transepithelial electrogenic Na+ transport (INa) was investigated in the coprodeum of 20-days-old chicken embryos in Ussing chambers. Short circuit current (Isc) and transepithelial resistance (Rt) were 14.7±4.8 A · cm-2 (n=12) and 0.53±0.09 k · cm-2 (n=12), respectively. INa was calculated from changes in Isc by substitution of mucosal Na+ by (N-methyl-d-glucamine) (NMDG). Isc inversed during Na+ removal, and INa was found to be 27.8±4.7 A · cm-2 (n=12). Amiloride (100 mol · l-1) inhibited only about 60% of INa. Analysis of Isc fluctuations revealed a Lorentzian component in the power density spectrum with a corner frequency of about 57 Hz. This component was not correlated to INa, and its origin is still unclear. Removal of mucosal Ca2+ increased INa about 2.5-fold due to an increase of the amiloride-insensitive component of INa in additionally investigated adult tissues. The results clearly show that this is due to a non-selective cation channel with an apparent order of selectivity Cs+>Na+=K+>Rb+>Li+. The Ca2+ concentration required to block 50% of the Isc was about 18 mol · l-1. The I
sc
Ca
could also be supressed by other divalent cations such as Mg2+ and Ba2+. Additionally, an INa-linked Lorentzian component occurred which dominated the control spectrum with a significantly higher corner frequency (about 88 Hz). The results indicate that Na+ absorption in the coprodeum of the chicken embryo is more complex than in adult hens. However, the Ca2+ sensitivity of INa is similar to comparable effects described for other epithelia. This possibly reflects the existence of two types of amiloride-insensitive apical cation channels as pathways for Na+ absorption, which may be involved to differing degrees in ontogenetic developments of nonselective channels to Na+-specific ion channels.Abbreviations
DPL
direct-linear-plot method
-
slope of the back-ground noise component
-
EGTA
ethylene glycol-bi(2-amino-ethylether)-N,N,N,N-tetraacetic acid
-
f
frequency
-
f
c
corner frequency of the Lorentzian noise component
-
G
t
transepithelial conductance
-
HEPES
N-hydroxyethylpiperazine-N-ethanesulfonic acid
-
I
sc
short-circuit current
-
I
Na
transepithelial sodium current
-
I
sc
Ca
Ca2+-sensitive short-circuit current
-
K
m
Ca
Michaelis-Menten constant for Ca2+
-
K
B
power density of the background noise component at f=1Hz
-
m
mucosal
-
NMDG
N-methyl-D-glucamine
-
R
t
transepithelial resistance
-
s
serosal
-
SEM
standard error of mean
-
S(f)
power density of the Lorentzian noise component
-
S
o
plateau value of the Lorentzian noise component 相似文献
27.
Klaus Hartfelder Heinz Rembold 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1991,160(6):617-620
Summary Juvenile hormone III content and ecdysteroid titer were analyzed for larval and pupal development of the stingless bee,Scaptotrigona postica depilis. Castespecific differences in juvenile hormone III content were detected at three developmental phases: at the transition from the fourth to the fifth larval stadium, in the spinning phase of the fifth larval stadium, and shortly after the imaginal moult. During the fifth larval stadium, juvenile hormone content closely reflects corpora allata activity. Juvenile hormone synthesis may thus be responsible for the elevated hormone titer in spinning-phase queen larvae, a phase of known sensitivity for induction of queen characters by exogenous juvenile hormone. For ecdysteroids, two phases of caste-specific differences were found: in the pre-pupal phase, and shortly after the imaginal moult. In both periods the titer in queens is distinctly higher compared to workers.Abbreviations
Im
imago 1 day after eclosion
-
L3, L4, L5
larval instars 3, 4, and 5
-
L5F1, L5F2
substages of feeding phase in fifth larval instar
-
L5S1, L5S2, L5S3
substages of spinning phase in fifth larval instar
-
PP1, PP2
substages of prepupal phase
-
Pw
white eyed pupa
-
Pp
pink eyed pupa
-
Pr
red eyed pupa
-
Pd
dark eyed pupa
-
Pdl, Pdm, Pdd
dark eyed pupa with progressive tanning of cuticle
-
RIA
radioimmunoassay 相似文献
28.
Udo Wienand Ulrike Weydemann Ursula Niesbach-Klösgen Peter A. Peterson Heinz Saedler 《Molecular & general genetics : MGG》1986,203(2):202-207
Summary The c2 locus of Zea mays, identified as one of the genes affecting anthocyanin biosynthesis, was cloned using the transposable element En (Spm) as a gene tag. The Spm element present at the c2 locus in the autonomously mutating c2-m1 line was isolated using En1 element specific probes. Sequences flanking the element were identified as c2 locus specific and were used to clone the nonautonomous c2-m2 and wild-type alleles. The cloning and analysis of a cDNA complementary to the c2 locus provided evidence that this gene encodes the enzyme chalcone synthase. 相似文献
29.
30.
Summary In mammals, a number of liver-derived plasma proteins, termed acute phase reactants, are induced during an inflammation response. We have studied genetic variation in the structure and expression of several of these proteins in a variety of inbred and wild-derived mice. In a genetic cross, electrophoretic polymorphisms for the two 1-acid glycoproteins, AGP-1 and AGP-2, co-segregated in 58 backcross progeny, indicating that either a single gene or two tightly-linked genes on chromosome 4 encode the AGPs. In the same backcross, segregation of variation in haptoglobin structure showed that the gene encoding this acute phase reactant is on chromosome 8. Structural variation in serum amyloid A correlated with restriction fragment length polymorphisms in the Saa gene determined by Taylor and Rowe (1984). Analysis of a number of highly diverged species of mice indicated that AGP expression has undergone considerable modification during evolution of the Mus genus; this is associated with alterations in Agp gene organization, which may include species-specific amplification and/or deletion events. 相似文献