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31.
Plasma samples from 106 pregnant Karan Swiss (Brown Swiss x Sahiwal) cows and 108 Murrah buffalo were tested for thyroxine (T(4)) levels to determine the relationship between the hormonal changes and advancing pregnancy in the two species. All samples were collected within 2 months (January and February) to avoid seasonal interference on T(4) levels. In pregnant cows, the concentration of T(4) increased sharply during the first trimester, reaching a peak at the third month of gestation followed by a gradual decline until the last month of pregnancy. In pregnant buffalo, peripheral plasma T(4) levels fluctuated slightly throughout pregnancy without exhibiting a specific trend. Statistical analysis revealed that the magnitude of T(4) levels was significantly lower in buffalo (P < 0.01) than in the cows throughout pregnancy and that the hormonal patterns of the two species were significantly different (P < 0.05) during gestation. It was hypothesized from this study that T(4) requirements for the fetal buffalo calf may be lower than that for the fetal cattle calf since the buffalo gestation period is a month longer and the metabolic rate lower vis-a-vis the cow. 相似文献
32.
High frequency, direct regeneration of shoots was induced in leaf cultures ofPaulownia tomentosa, P. fortunei x P. tomentosa andP. kawakamii. The optimum culture medium for the leaf explants derived from shoot cultures was Murashige-Skoog (MS) medium supplemented with 10 M indole-3-acetic acid and 50 M benzyladenine. Up to 40 shoots were obtained over a 4 month culture period from each leaf explant. Rooting occurred spontaneously in the shoots that were about 1 cm tall when subcultured on phytohormone-free MS medium. The plantlets could be transplanted successfully. Some of the transplantedP. tomentosa plantlets flowered in the greenhouse one year after transplanting. The protocol is suitable not only for rapid multiplication of the various species ofPaulownia, but also for analytical studies associated with adventitious shoot regeneration. 相似文献
33.
34.
Ramana M. Gosukonda Ananta Porobodessai Essie Blay Channapatna S. Prakash Curt M. Peterson 《In vitro cellular & developmental biology. Plant》1995,31(2):65-71
Adventitious shoots of sweetpotato (Ipomoea batatas L. Lam.) were produced in vitro using a two-stage culture method. Petiole explants were incubated on Murashige and Skoog
(MS) medium supplemented with 2,4-dichlorophenoxy acetic acid (0.2 mg·liter−1) for 3 d, and transferred to MS medium with thidiazuron (0 to 0.4 mg·liter−1). Shoot regeneration was observed in most explants (78.2%) of genotype PI 318846-3 within 28 days when cultured on thidiazuron
at 0.2 mg·liter−1. Histological studies of cultured petiole explants showed meristematic activity within cells of vascular bundles and throughout
the ground tissue. Explants isolated from apical leaves exhibited higher shoot regeneration frequency than those isolated
from the basal portion of the shoot. Leaf lamina explants exhibited lower frequency of regeneration than petiole explants.
In contrast to thidiazuron, the use of zeatin riboside, and kinetin resulted in a lower frequency of shoot regeneration although
more sweetpotato genotypes could be regenerated using either of these two cytokinins. The sweetpotato plants regenerated using
thidiazuron grew vigorously and rooted easily when transferred to the greenhouse. 相似文献
35.
Prakash Sista Sharon Edmiston James W. Darges Simon Robinson David J. Burns 《Molecular and cellular biochemistry》1994,141(2):129-134
Transmission of extra cellular signals across biological membranes results in the generation of lipid metabolites which in turn influence specific cellular events such as cell growth or differentiation. Many of these lipid messengers can activate protein kinase C (PKC) isozymes of which one function is to perpetuate the extracellular signals to the nucleus by phosphorylating other targets proteins. We have engineered mammalian cell lines to identify and evaluate activators and inhibitors of PKC-dependent and independent signal transduction pathways. The A31 mouse fibroblast cell line, has been stably transfected with a construct containing a triplet repeat of the TPA response element (TRE) upstream of a thymidine kinase promoter fused to the human growth hormone (hGH) gene. A31 cells containing this reporter construct exhibit significant increases in hGH secretion following stimulation by phorbol esters or other mitogens. The levels of hGH secretion are modulated in this system using different pharmacological agents. We demonstrate that this assay can be used to identify specific and general inhibitors as well as activators of the signal transduction pathway mediated by PKC isozymes. (Mol Cell Biochem141: 129–134, 1994) 相似文献
36.
Because of defective nucleotide excision repair of ultraviolet damaged DNA, xeroderma pigmentosum (XP) patients suffer from a high incidence of skin cancers. Cell fusion studies have identified seven XP complementation groups, A to G. Previous studies have implicated the products of these seven XP genes in the recognition of ultraviolet-induced DNA damage and in incision of the damage-containing DNA strand. Here, we express the XPG-encoded protein in Sf9 insect cells and purify it to homogeneity. We demonstrate that XPG is a single-strand specific DNA endonuclease, thus identifying the catalytic role of the protein in nucleotide excision repair. We suggest that XPG nuclease acts on the single-stranded region created as a result of the combined action of the XPB helicase and XPD helicase at the DNA damage site. 相似文献
37.
S. B. Narasimhulu P. B. Kirti S. R. Bhatt Shyam Prakash V. L. Chopra 《Plant cell reports》1994,13(11):657-660
Camelina sativa is a wild crucifer that is reported to be resistant to Alternaria blight. Polyethylene glycol mediated fusion was attempted between protoplasts from etiolated hypocotyls of Brassica carinata and mesophyll protoplasts of Camelina sativa. The mean frequency of heterokaryons was 6.8%. Three hybrid shoots were regenerated, each from a single fusionderived callus. These shoots failed to produce roots capable of withstanding transplantation. Confirmation of hybridity was obtained from the morphology of in vitro produced leaves, somatic chromosome number in leaf tips, and restriction fragment length polymorphism for a nuclear rDNA probe. Analysis for organelle constitution using RFLPs indicated that the hybrid contained chrloroplasts derived from the wild species and mitochondria from the cultivated Brassica species.Abbreviations 2,4-D
2,4-dichlorophenoxy-acetic acid
- IAA
Indole-3-acetic acid
- NAA
-Naphthaleneacetic acid
- IBA
Indole-3-butyric acid
- GA3
gibberellic acid
- BAP
6-Benzylaminopurine
- MS
Murashige and Skoog (1962) basal medium 相似文献
38.
Lectin-induced apoptosis of tumour cells 总被引:3,自引:0,他引:3
The mechanisms of cytotoxic activity of Griffonia simplicifolia1-B4 (GS1B4) and wheat germ agglutinin (WGA) lectins againstvarious murine tumour cell lines were studied. Tumour cellsthat lack lectin-binding carbohydrates were resistant to lysisby these lectins. However, YAC-1 cells that expressed GS1B4lectin-binding sites showed low sensitivity to lysis. To furtheranalyse the relative importance of cell surface carbohydratesin lectin cytotoxicity, BL68 melanoma cells, which donot express the 相似文献
39.
Chandra Prakash Prasad Satyendra Chandra Tripathi Manish Kumar Purusottam Mohapatra 《Biotechnology and bioengineering》2023,120(8):2049-2055
Cancer cell lines play a crucial role as invaluable models in cancer research, facilitating the examination of cancer progression as well as the advancement of diagnostics and treatments. While they may not perfectly replicate the original tumor, they generally exhibit similar characteristics. Low-passage cancer cell lines are generally preferred due to their closer resemblance to the original tumor, as long-term culturing can alter the genetic and molecular profiles of a cell line thereby highlighting the importance of monitoring the passage number (PN). Variations in proliferation, migration, gene expression, and drug sensitivity can be linked to PN differences. PN can also influence DNA methylation levels, metabolic profiles, and the expression of genes/or proteins in cancer cell lines. When conducting research on cancer cell lines, it is crucial for researchers to carefully select the appropriate PN to maintain consistency and reliability of results. Moreover, to ensure dependability and replicability, scientists ought to actively track the growth, migration, and gene/or protein profiles of cancer cell lines at specific PNs. This approach enables the identification of the most suitable range of PNs for experiments, guaranteeing consistent and precise results. Additionally, such efforts serve to minimize disparities and uphold the integrity of research. In this review, we have laid out recommendations for laboratories to overcome these PN discrepancies when working with cancer cell lines. 相似文献
40.