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排序方式: 共有422条查询结果,搜索用时 15 毫秒
1.
William J. Hendry III Wendell W. Leavitt 《Differentiation; research in biological diversity》1993,52(3):221-227
Abstract. In previous studies, we found that a single neonatal exposure to diethylstilbestrol (DES) resulted in severe hyperplasia and a high incidence of endometrial adenocarcinoma in the uterus of adult hamsters. These observations prompted us to investigate the consequences of DES exposure on earlier stages of uterine morphogenesis. After neonates were treated within 6 h of birth (day 1) with 100 μg of DES or oil vehicle, uterine tissue morphometry plus cell labelling indices following in vivo pulse labeling with [3 H]thymidine were determined on days 3–21 of life. The sequential findings were: (1) a precocious (day 3) burst of cellular proliferation throughout the uterus, (2) an early period (days 3–9) of hypertrophy and increased cell density in the luminal epithelium, (3) an extreme acceleration of uterine growth resulting in a persistent increase in total uterine mass (threefold enhancement on days 5–21), (4) precocious development of endometrial glands (day 9) that were sites of intense but transient proliferative activity, (5) a middle period (days 9–15) when the percentage of stromal cells engaged in proliferative activity was reduced, (6) a second wave (days 15–21) of enhanced proliferative activity in the luminal epithelium, and (7) later development (day 21) of reduced cell density in the uterine stroma, apparently due to increased intercellular collagen accumulation. These results support our working hypothesis that the acute uterotropic response to neonatal DES treatment initiates a change in the developing hamster uterus, and later estrogenic stimulation promotes neoplastic progression in the DES-altered adult organ, perhaps due to disruption of stromal-epithelial interactions. 相似文献
2.
Purification and partial characterization of a corticosteroid-binding globulin from hamster serum 总被引:1,自引:0,他引:1
Our objective was to characterize and purify the corticosteroid-binding proteins in hamster pregnancy serum. When [3H]cortisol-labeled pregnancy and proestrous serum were subjected to native polyacrylamide gel electrophoresis, a single peak of specific steroid-binding activity was detected in each, with identical electrophoretic mobility. The steroid-binding affinity (Ka = 1.07.10(8) M-1 for cortisol) is typical of corticosteroid-binding globulin from other species, but the steroid-binding specificity (cortisol greater than testosterone greater than progesterone) is not. An ultraviolet photoaffinity-labeling protocol was developed using 17 beta-hydroxy-4,6-[1,2-3H]androstadiene-3-one ([3H]androstadienolone), permitting analysis of ultraviolet photoaffinity-labeled proestrous and pregnancy serum by two-dimensional polyacrylamide gel electrophoresis and fluorography. Both sera contained the same labeled protein species. Corticosteroid-binding globulin was purified from pregnancy serum by DEAE-cellulose chromatography followed by steroid affinity chromatography on androstadienolone-17 beta-hemisuccinate-ethylenediamine-AffiGel 10. The purified protein (Mr = 62,250; pI = 3.95; n = 1; Stokes radius = 3.5; S = 4-5) was determined to be a glycoprotein. When analyzed by gel filtration and two-dimensional polyacrylamide gel electrophoresis, purified corticosteroid-binding globulin behaved the same as in unfractionated serum, and when ultraviolet photoaffinity-labeled with [3H]androstadienolone, purified corticosteroid-binding globulin produced the same fluorogram spot pattern seen in unfractionated serum. A specific corticosteroid-binding globulin antiserum was raised in rabbits, and this antiserum reacted with a single spot in Western blots of unfractionated serum. Thus, hamster pregnancy serum was determined to have one corticosteroid-binding protein. This protein is identical to the corticosteroid-binding globulin found in proestrous serum, with a higher titer in pregnancy serum. No other steroid-binding component is observed in hamster serum. 相似文献
3.
Correction of the N-terminal sequences of the human plastin isoforms by using anchored polymerase chain reaction: identification of a potential calcium-binding domain. 总被引:9,自引:3,他引:6
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Plastins are a family of at least three cytoplasmic protein isoforms that are expressed differentially between cells of the hematopoietic lineages and cells of solid tissues. Expression of the L-plastin isoform appears to be restricted to replicating blood cells, and the two T-plastin isoforms appear to be restricted to replicating cells of solid tissues. However, L-plastin is induced in many human solid tumor-derived cells. We used the anchored polymerase chain reaction technique to amplify and clone the missing 5' ends of plastin mRNAs. We found that both plastin isoforms contain a potential calcium binding site near the N terminus. 相似文献
4.
Modulation of microfilament protein composition by transfected cytoskeletal actin genes. 总被引:3,自引:0,他引:3
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HuT-14T is a highly tumorigenic fibroblast cell line which exhibits a reduced steady-state level of beta-actin due to coding mutations in one of two beta-actin alleles. The normal rate of total actin synthesis could be restored in some clones of cells following transfection of the functional beta-actin gene but not following transfection of the functional gamma-actin gene. In gamma-actin gene-transfected substrains that have increased rates of gamma-actin synthesis, beta-actin synthesis is further reduced in a manner consistent with an autoregulatory mechanism, resulting in abnormal ratios of actin isoforms. Thus, both beta- and gamma-actin proteins can apparently regulate the synthesis of their coexpressed isoforms. In addition, decreased synthesis of normal beta-actin seems to correlate with a concomitant down-regulation of tropomyosin isoforms. 相似文献
5.
In naive rats previously given saccharin (0.1%) as the only drinking fluid for 14 days, naloxone produced a conditioned taste aversion at a dose (0.09 mg/kg, SC) that had little or no effect in normal controls. The magnitude of this effect of the saccharin increased between 2 and 7 days after cessation of the treatment. Under these experimental conditions, evidence of an interaction between the saccharin exposure and a naloxone response was also seen with rectal temperature measurements. Therefore, in rats having no history of morphine, previous consumption of saccharin may potentiate various actions of naloxone including its aversive property. 相似文献
6.
7.
The ATP-binding-cassette transmembrane transporters (ABC transporters)
known from vertebrates belong to four major subfamilies: (1) the P-
glycoproteins (Pgp); (2) the cystic fibrosis transmembrane conductance
regulators (CFTR); (3) the Tap proteins encoded with the major
histocompatibility complex of mammals; and (4) the peroxisomal membrane
proteins. Both Pgp and CFTR have a structure suggesting a past internal
gene duplication; a phylogenetic analysis indicated that these duplications
occurred independently, while an independent tandem gene duplication
occurred in the case of the Tap family. Both the Pgp and Tap proteins show
evidence of relationship to bacterial ABC transporters lacking internal
duplication, and both are significantly more closely related to the HlyB
and MsbA families of transporters from purple bacteria than they are to ABC
transporters from nonpurple bacteria. The simplest hypothesis to explain
this observation is that eukaryotic Pgp and Tap genes are descended from a
mitochondrial gene or genes that were subsequently translocated to the
nuclear genome. The Pgp genes of eukaryotes are characterized by a
remarkable degree of convergent evolution between the ATP-binding cassettes
of their N- terminal and C-terminal halves, whereas no such convergence is
seen between the two halves of CFTR genes or between the duplicated Tap
genes. Exon 13 of the CFTR gene, which encodes a putative regulatory domain
not found in other ABC transporters apart from CFTR, showed high levels of
both synonymous and nonsynonymous difference in comparisons among different
mammalian species, suggesting that this region is a mutational hot spot.
相似文献
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10.
X Xiao G Hintermann AL Demanin J Piret 《Journal of industrial microbiology & biotechnology》1996,16(4):261-262
Streptomyces glaucescens is shown to possess -lactamase activity which is inhibitable by clavulanate. This is important in regard to its use as a cloning host for enzymes of \-lactam biosynthesis. 相似文献