In vitro effects of 2,4-dichlorophenoxy acetic acid (2,4-D) on bovine cells.
(1/798)
Bovine fetal muscle cells were exposed to culture media containing 2 mg and 20 mg per liter of 2,4-dichlorophenoxy acetic acid (2,4-D) for varying intervals to determine the in vitro response of mammalian cells to this compound. The concentrations of 2,4-D used were comparable to those used in spray programmes although the residues normally found in pasture are much lower since 2,4-D is rapidly degraded under field conditions. Untreated and treated cultures were analyzed for total cell count, mitotic index and the percentages of differentiating and degenerating cells. The response of cultures to treatment was similar irrespective of the concentrations of 2,4-D used although in higher concentrations there was an initial drop in mitotic index. Other changes noted in treated cultures included an increase in differentiating and degenerating cells compared to those in control. The mitotic cells in treated cultures exhibited unipolar and tripolar spindles and a variety of other abnormalities including malorientation of the mitotic apparatus in relation to the axis of the cell. Myoblasts in initial stages of myogenesis were noted to be in mitosis in treated cultures suggesting that 2,4-D may have a stimulatory effect on myoblasts which in normal myogenesis are in post mitotic stage. (+info)
Attenuation by all-trans-retinoic acid of sodium chloride-enhanced gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine in Wistar rats.
(2/798)
The effect of prolonged administration of all-trans-retinoic acid (RA) on sodium chloride-enhanced gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine, and the labelling and apoptotic indices and immunoreactivity of transforming growth factor (TGF) alpha in the gastric cancers was investigated in Wistar rats. After 25 weeks of carcinogen treatment, the rats were given chow pellets containing 10% sodium chloride and subcutaneous injections of RA at doses of 0.75 or 1.5 mg kg(-1) body weight every other day. In week 52, oral supplementation with sodium chloride significantly increased the incidence of gastric cancers compared with the untreated controls. Long-term administration of RA at both doses significantly reduced the incidence of gastric cancers, which was enhanced by oral administration of sodium chloride. RA at both doses significantly decreased the labelling index and TGF-alpha immunoreactivity of gastric cancers, which were enhanced by administration of sodium chloride, and significantly increased the apoptotic index of cancers, which was lowered by administration of sodium chloride. These findings suggest that RA attenuates gastric carcinogenesis, enhanced by sodium chloride, by increasing apoptosis, decreasing DNA synthesis, and reducing TGF-alpha expression in gastric cancers. (+info)
Insulin-like growth factor 1 is required for G2 progression in the estradiol-induced mitotic cycle.
(3/798)
Insulin-like growth factor 1 (IGF1) has been proposed as a "G1-progression factor" and as a mediator of estradiol's (E2) mitogenic effects on the uterus. To test these hypotheses, we compared E2's mitogenic effects on the uteri of Igf1-targeted gene deletion (null) and wild-type littermate mice. The proportion of uterine cells involved in the cell cycle and G1- and S-phase kinetics were not significantly different in wild-type and Igf1-null mice. However, the appearance of E2-induced mitotic figures and cell number increases were profoundly retarded in Igf1-null uterine tissue. There was a significant increase in nuclear DNA concentration in Igf1-null cells, consistent with a G2 arrest. Interestingly, apoptotic cells were also significantly reduced in abundance, and the normal massive apoptotic response to E2 withdrawal was absent in the Igf1-null uterus. These data show that Igf1 is an essential mediator of E2's mitogenic effects, with a critical role not in G1 progression but in G2 progression. (+info)
Comparison of mitotic index, in vitro bromodeoxyuridine labeling, and MIB-1 assays to quantitate proliferation in breast cancer.
(4/798)
PURPOSE: To investigate the hypothesis that in vitro bromodeoxyuridine (BrDu) labeling might be superior to MIB-1 immunostaining for prognostic value, because it more selectively labels cells during the S phase. METHODS: Four hundred eighty-six patients with breast cancers (59% lymph node-negative, 41% lymph node-positive) surgically excised between 1988 and 1993 (median follow-up, 62 months) were evaluated for cellular proliferation using prospective in vitro BrDu uptake assays, retrospective mitotic indices, and MIB-1 labeling. RESULTS: MIB-1, BrDu labeling, and mitotic index-derived proliferation data were highly correlated. Each was similarly associated with most other markers of prognosis, although these relationships were not identical. By univariate analysis, nodal status was the most significant prognostic variable for all patients. Higher BrDu labeling index, MIB-1 immunolabeling, and mitotic index were also associated with shortened disease-free survival (DFS) and disease-specific survival for the entire patient group, as well as for node-negative patients. The association between cellular proliferation and survival was much weaker for node-positive patients. Multivariate models confirmed that nodal status, tumor size, and proliferation data predicted survival in all patients as well as those with node-negative disease, although MIB-1 was somewhat more closely associated with outcome than mitotic index or in vitro BrDu data. For patients with T1NOMO disease (n = 172), the only significant predictors of DFS were proliferation rate (mitotic index or MIB-1) and tumor grade. CONCLUSIONS: Proliferation rate predicts recurrence and survival in breast cancer. This effect is more pronounced in node-negative patients. In vitro BrDu data are not superior to MIB-1 and mitotic counting. (+info)
Oncogene alterations in carcinomas of the uterine cervix: overexpression of the epidermal growth factor receptor is associated with poor prognosis.
(5/798)
The involvement of human papillomavirus (HPV) in the development of carcinomas of the uterine cervix has been firmly established. However, other genetic alterations also play an important role in the pathogenesis of cervical cancer. Therefore, we have investigated the role of several (onco)genes in cervical carcinoma. In tumors from 136 patients with stage I and II cancer of the uterine cervix, the expression of epidermal growth factor receptor (EGFR), c-erbB-2/neu, p53, and murine double minute 2 (MDM-2) was studied using immunohistochemistry. In 32 cases, amplification of EGFR, c-erbB-2/neu, MDM-2, and c-myc was studied by Southern blot hybridization. The expression levels of these proteins were correlated with HPV positivity, International Federation of Gynecologists and Obstetricians stage, lymph node metastases, tumor diameter, vessel invasion, and disease-free and overall survival. Moderate/strong expression of EGFR was observed in 54% of tumors. c-erbB-2/neu was focally positive in 12 cases. p53 showed moderate/strong expression in 32% of the tumors. Thirteen % of tumors showed a moderate/strong expression of MDM-2, and this expression was correlated to p53 expression (P<0.001). Only moderate/strong expression of EGFR was associated with reduced disease-free (P = 0.002) and overall survival (P = 0.003). In multivariate analysis, the association of EGFR overexpression with poor prognosis was independent from lymph node status. Gene amplification was found for EGFR (four cases), c-erbB-2/ neu (two cases), and c-myc (six cases). In two tumors, rearrangement of c-myc was found, probably due to the integration of HPV. In conclusion, overexpression of the EGFR is an independent predictor for prognosis in earlier stages (stage I and II) of cervical cancer. p53 and MDM-2 expression are correlated to each other and may play a role in the interaction with HPV. The importance of c-erbB-2/neu and c-myc amplification is relatively small in stage I and II cervical cancer. (+info)
Taxol suppresses dynamics of individual microtubules in living human tumor cells.
(6/798)
Microtubules are intrinsically dynamic polymers, and their dynamics play a crucial role in mitotic spindle assembly, the mitotic checkpoint, and chromosome movement. We hypothesized that, in living cells, suppression of microtubule dynamics is responsible for the ability of taxol to inhibit mitotic progression and cell proliferation. Using quantitative fluorescence video microscopy, we examined the effects of taxol (30-100 nM) on the dynamics of individual microtubules in two living human tumor cell lines: Caov-3 ovarian adenocarcinoma cells and A-498 kidney carcinoma cells. Taxol accumulated more in Caov-3 cells than in A-498 cells. At equivalent intracellular taxol concentrations, dynamic instability was inhibited similarly in the two cell lines. Microtubule shortening rates were inhibited in Caov-3 cells and in A-498 cells by 32 and 26%, growing rates were inhibited by 24 and 18%, and dynamicity was inhibited by 31 and 63%, respectively. All mitotic spindles were abnormal, and many interphase cells became multinucleate (Caov-3, 30%; A-498, 58%). Taxol blocked cell cycle progress at the metaphase/anaphase transition and inhibited cell proliferation. The results indicate that suppression of microtubule dynamics by taxol deleteriously affects the ability of cancer cells to properly assemble a mitotic spindle, pass the metaphase/anaphase checkpoint, and produce progeny. (+info)
Genetic deletion of p21WAF1 enhances papilloma formation but not malignant conversion in experimental mouse skin carcinogenesis.
(7/798)
Tumor suppression by p53 is believed to reside in its ability to regulate gene transcription, including up-regulation of p21WAF1. In p53(-/-) mice, chemical- or oncogene-induced skin tumors undergo accelerated malignant conversion. To determine the contribution of the p21WAF1 gene product to epidermal carcinogenesis, animals +/+, +/-, and -/- for a null mutation in the p21WAF1 gene were treated once with 25 nmol 7,12-dimethylbenz[a]anthracene, followed by 5 microg of TPA two times/week for 20 weeks. Papilloma frequency was higher in the p21WAF1-deficient mice. However, the frequency of malignant conversion was similar among all three genotypes. After TPA treatment, all genotypes developed epidermal hyperplasia, although the labeling index was lower in p21WAF1 (-/-) epidermis compared with p21WAF1 (+/+). Furthermore, the expression of differentiation markers was the same across genotypes in untreated or TPA-treated epidermis. Similar frequencies of malignant conversion were also observed in an in vitro assay. Thus, p21WAF1 suppresses early stages of papilloma formation but not malignant progression in mouse skin carcinogenesis, and decreased levels of p21WAF1 do not account for the enhanced malignant conversion of p53 null epidermal tumors. (+info)
The tammar wallaby, Macropus eugenii, has a ruminant-like digestive system which may make a significant concentration of amino acids and fatty acids available to the blastocyst via uterine fluids. Fluorescent and radioisotope analyses were performed to determine the rate of glutamine and palmitate use by blastocysts recovered on day 0, 3, 4, 5 and 10 after reactivation induced by removal of pouch young (RPY). Between day 0 and 4 glutamine uptake increased from 15.6 +/- 6.6 to 36.1 +/- 2.7 pmol per embryo h-1 (P < 0.01) and ammonium production increased from 8.2 +/- 4.3 to 26.6 +/- 3.0 pmol per embryo h-1 (P < 0.01). Glutamine oxidation did not increase until day 10 after RPY (P < 0.01), but the percentage of glutamine oxidized increased from 4.5 +/- 3.1% during diapause to 31.2 +/- 12.6% (P < 0.01) by day 5 after RPY and increased further to 51.0 +/- 15.8% (P < 0.01) by day 10 after RPY. Palmitate oxidation also increased from 0.3 +/- 0.1 by day 0 blastocysts to 3.8 +/- 1.7 pmol per embryo h-1 (P < 0.01) by day 4 blastocysts. This increase provides a greater potential for ATP production, possibly to supply increased demand due to the coincident resumption of mitoses. The ATP:ADP ratio within blastocysts had reduced by the time of the first measurement at day 3 (0.5 +/- 0.2 pmol per embryo h-1; P < 0.01) compared with day 0 blastocysts (1.4 +/- 0.3 pmol per embryo h-1). It is likely that metabolism of amino acids and fatty acids contributes to the energy supply during reactivation of tammar wallaby blastocysts after embryonic diapause. (+info)