ISSN:0730-2312    

DOI:10.1002/jcb.240490202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThe feasibility of introducing foreign genes into the genomes of cattle, goats, pigs, and sheep has only recently been demonstrated. Studies have thus far focused on improving growth efficiency or directing expression of pharmaceutical proteins to the mammary glands of these species. The general strategy for producing transgenic livestock and mice is similar. In addition to the obvious difference in scale between mice and livestock experiments, there are noteworthy obstacles that significantly reduce the efficiency of producing transgenic livestock. Low embryo viability, low transgene integration rates, and high animal costs contribute to project costs that can easily exceed hundreds of thousands of dollars. A better understanding of the mechanisms that govern transgene integration should lead to improved efficiencies. But, the full potential of the transgenic livestock system will not be fully realized until: (1) gene constructs can be designed that function in a reproducible, predictable manner; and (2) the genetic control of physiological processes are more clearly elucidated. Newly emerging approaches may resolve at least some of these issues within the next decade.

ISSN:0730-2312    

DOI:10.1002/jcb.240490203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractMilk and milk products comprise a substantial fraction of the protein intake of the industrialised West. The establishment of germline manipulation techniques in cows offers opportunities for directly manipulating milk composition to produce products with enhanced nutritional and processing properties. The major milk proteins are encoded by a small number of abundantly expressed single‐copy genes and a number of possible manipulations are described. Milk proteins exhibit complex interactions with each other and with other constituents of milk. It will, therefore, be necessary to utilise model systems to evaluate the consequences of these proposed changes before embarking upon the costly and time‐consuming process of manipulating the bovine gen

ISSN:0730-2312    

DOI:10.1002/jcb.240490204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractMouse strains which develop tumors at a high incidence with characteristics very similar to human cancers have been derived over the last 8 years. The tumors are caused by defined genetic alterations in the mouse genome. Three areas of research have contributed to the derivation of these mouse strains: (1) Molecular analysis of human tumors has shown that distinct oncogenes and tumor suppressor genes are consistently involved in a high percentage of primary tumors. (2) Regulatory enhancer‐promoter sequences have been identified which direct gene expression to specific target cells, preferentially mammary epithelial cells. (3) The introduction of recombinant DNA molecules into fertilized mouse eggs by microinjection and integration of the injected DNA into the genome of injected cells has given rise to mutant mouse strains with unique and defined genetic alterations. Studies with different promoter‐oncogene combinations introduced into transgenic mouse strains have led to the following general conclusions: (1) Oncogenes expressed in mammary gland cells predispose transgenic mice to mammary tumors. (2) The oncogenic potential of indivdiual oncogenes in mammary epithelial cells differs. (3) Oncogene expression initially often causes a preneoplastic state affecting growth and differentiation parameters of cells. (4) The expression of different oncogenes synergizes to reduce tumor latency. Synergism can also be observed with physiological growth signals like estrogen or growth hormone. The oncogenes with a role in mammary carcinomas which have been investigated in transgenic mice will be described here. The phenotypic consequences of oncogene expression and the implications for the multistep carcinogenesis model will be discus

ISSN:0730-2312    

DOI:10.1002/jcb.240490205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractIn vivo regulation of cell cycle dependent human histone gene expression was examined in transgenic mice using a fusion construct containing 6.5 kB of a human H4 promoter linked to the chloramphenicol acetyltransferase (CAT) reporter gene. Transcriptional control of histone gene expression, as a function of proliferative activity, was determined. We established the relationship between DNA replication dependent H4 mRNA levels (Northern blot analysis) and H4 promoter activity (CAT assay) during postnatal development in a broad spectrum of tissues. In most tissues sampled in adult animals, the cellular representation of H4 gene transcripts declined in parallel with promoter activity. This result is consistent with transcriptional control of H4 gene expression at the cessation of proliferation. Interestingly, while H4 mRNA was detectable at very low levels post‐proliferatively in brain, promoter activity persisted in adult brain, where most of the cells are terminally differentiated. This dissociation between histone gene promoter activity and histone mRNA accumulation points to the possibility of post‐transcriptional regulation of histone gene expression in brain. Cultures of osteoblasts were prepared from calvaria of transgenic mice carrying the H4 promoter/CAT reporter construct. In contrast to the brain, in these bone‐derived cells, we established by immunohistochemistry that the transition to the quiescent, differentiated state is associated with a transcriptionally mediated downregulation of histone gene expression at the single cell

ISSN:0730-2312    

DOI:10.1002/jcb.240490206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractChanges in chromatin structure as determined from DNAse I hypersensitive site analysis are associated with c‐myc amplification and increased transcript/protein levels in malignant fibrous histiocytoma (MFH) cell lines. A DNAse I hypersensitive site near the PO promoter region was observed in one MFH cell line (UR HCL 1), and in normal fibroblasts (HFF), but not in an MFH cell line with an amplified c‐myc gene (P3C). A DNAse I hypersensitive site exclusive to P3C amplified c‐myc was identified slightly 3′ of exon one. No alterations in c‐myc DNAse I hypersensitive site patterns were observed in HFF fibroblasts following serum release, when peak levels of c‐myc transcript were induced. DNAse I hypersensitive site patterns associated with gene amplification may reflect a compensatory response by P3C cells to an abundance of c‐myc transcript. Furthermore, elevated levels of protein in P3C cells provide additional evidence that amplified c‐myc is an o

ISSN:0730-2312    

DOI:10.1002/jcb.240490207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThe prognostic significance of the epidermal growth factor receptor status (EGF‐R‐status) for certain human tumors requires the development of antibodies useful for clinical application. We used purified receptor preparations to generate monoclonal antibodies immunoreactive with the EGF‐R purified from placenta membranes and A431 tumors. Four of the hybridomas contained antibodies (R2, R3, R5, and R9) which recognized both antigens. Antibody R3 was shown to display the following properties: it binds with a KDvalue of about 10−9–10−10M to the receptor, a half maximal inhibition of EGF‐binding is achieved at 5 × 10−8M, and in Western blots of cell membranes R3 specifically detects the EGF‐R at 0.1 μ/ml. R3 inhibits EGF‐dependent clonogenic growth of NRK cells and completely blocks EGF stimulated autophosphorylation of the receptor. Moreover, R3 also detects EGF‐R in paraffin‐embedded tissue sections taken from human salivary gland, term placenta, and adult skin and mammary carcinomas. Thus, R3 can be used in retrospective diagnostic clinical studies and might help to develop new immun

ISSN:0730-2312    

DOI:10.1002/jcb.240490208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractEffects of monensin were examined on the intracellular processing of the GABAA/benzodiazepine receptor (GABAA/BZDR) in neuron cultures derived from embryonic chicken brain, using3H‐flunitrazepam as the probe for the benzodiazepine modulator site on the receptor. Incubation of cultures with 0.1 or 1 μM monensin for 3 h blocked the binding of3H‐flunitrazepam by about 18%. Loss of ligand binding was due to a reduction in the number of binding sites, with no significant changes in receptor affinity. The general cellular protein synthesis and glycosylation in the cells were inhibited by 26% and 56%, respectively, in the presence of 1 μM monensin, as detected by assaying the incorporation of3H‐leucine and3H‐galactose. In contrast, an increase was observed for mannose incorporation by the cultures in the presence of the drug. Moreover, the results from in situ trypsinization of the cultures following monensin treatment showed that monensin did not alter the distribution of intracellular and surface receptors. The data suggest that monensin induces the down‐regulation of GABAA/BZDR by generating abnormal glycosylation of the receptor and interrupting its transport within the Golgi apparatus, as well as from the Golgi apparatus to the intracellular pool and cell membrane. The galactosylation of receptor proteins may be important for the maturation of t

ISSN:0730-2312    

DOI:10.1002/jcb.240490209

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractA pool of nuclear proteins from adult worms ofSchistosoma mansoniwas analyzed for amino acid composition and found to be compatible with high mobility group (HMG) proteins. One of the schistosome HMG proteins was identified as HMG 2 by one‐dimensional and two‐dimensional PAGE. Stage‐specific differences in the HM‐like protein composition were encountered when adult worms were compared to schistosomula, the larval form. Immobilization of the adult male and female nuclear proteins onto nitrocellulose, followed by hybridization against32P‐F‐10, a schistosome sex specific gene encoding a major egg shell protein, revealed distinct banding patterns. On the other hand, a synthetic oligonucleotide, derived from the 3′untranslated end of the F‐10 gene and possibly containing one regulatory element of the gene, bound mainly to male

ISSN:0730-2312    

DOI:10.1002/jcb.240490210

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractExpression of several cellular and matrix proteins which increase significantly during the maturation of growth plate cartilage has been shown to be affected by various endocrine and autocrine factors. In the studies reported here, transforming growth factor‐β (TGF‐β1) and basic fibroblast growth factor (bFGF) were administered to primary cultures of avian growth plate chondrocytes at pre‐ or post‐confluent stages to study the interplay that occurs between these factors in modulating chondrocytic phenotype. Added continuously topre‐confluentchondrocytes, TGF‐β1stimulated the cells to produce abundant extracellular matrix and multilayered cell growth; cell morphology was altered to a more spherical configuration. These effects were generally mimicked by bFGF, but cell shape was not affected. Administered together with TGF‐β1, bFGF caused additive stimulation of protein synthesis, and alkaline phosphatase (AP) activity was markedly, but transiently enhanced. During this pre‐confluent stage, TGF‐β1also increased fibronectin secretion into the culture medium. Added topost‐confluentcells, TGF‐β1alone caused a dosage‐dependent suppression of AP activity, but bFGF alone did not. Under these conditions, TGF‐β1and bFGF had little effect on general protein synthesis, but TGF‐β1alone caused large, dosage‐dependent increases in synthesis of fibronectin, and to some extent type II and X collagens. Given together with bFGF, TGF‐β1synergistically increased secretion of fibronectin. These findings reveal that regulation of phenotypic expression in maturing growth plate chondrocytes involves complex interactions between growth factors that are determined by timing, l

ISSN:0730-2312    

DOI:10.1002/jcb.240490211

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY