PubMed · 13657097
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S T WRIGHT. 1959-05-02. A quantitative serum-agar technique.. https://doi.org/10.1038/1831282b0
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Gracilaria cervicornis, Gracilaria blodgettii and Gracilaria crassissima growing along the coasts of Yucatán were investigated for their agar content. The effect of different concentrations of NaOH in the alkali treatment was evaluated. The three species of Gracilaria produced agars, both native and alkali treated, with different properties confirming the heterogeneity of the agar polymers in this genera. G. cervicornis produces agar polymers with an occurrence of methoxylation and sulphation at the C-6 of the beta-D-galactose residues, and with an extra methylation due to the presence of the 4-O-methyl-alpha-L-galactose residue. The presences of these residues is responsible for the extremely poor gelling ability of its agarocolloids, whose commercial value seems to be quite low. Agar extracts from G. blodgettii showed the typical pattern of unsubstituted agar with a very low degree of methylation on both galactose residues. The discrepancy found between sulphate content and NMR data of agar from this species requires a more detailed structural investigation. G. crassissima produces a good quality agar after sulphate precursor sequences have been removed by alkaline treatment, and it may be considered for exploitation as a source of commercial grade agar. Alkali treatment was effective both in removing alkali-labile sulphate and increasing the gel strength in G. crassissima but not in G. cervicornis and G. blodgettii.
The yield and physical and chemical properties of agars from Gracilaria dura (C. Agardh) J. Agardh, harvested in Thau lagoon (Mediterranean sea, France), were investigated. The agar yield ranged from 32% to 35%. Gel strength of agar ranged from 263 to 600 g cm(-2), with the maximum observed in October. A positive correlation was found between agar yield and gel strength (r = 0.82; P < 0.01). The gelling temperature followed the same pattern of gel strength and also showed higher value in October (43 degrees C). The nitrogen content varied from 1.04+/-0.60% (June) to 4.70+/-0.01% (October). A positive correlation was noted between nitrogen content and gel strength (r = 0.77; P < 0.05). The 3,6-anhydrogalactose content ranged from 0.70 to 0.84 and showed monthly significant differences (P < 0.05). There was a positive correlation between 3,6-anhydrogalactose content and gel strength. The values of sulfate content were relatively constant during the studied period and no significant differences were observed. The relative high gel strength indicates that this species may be considered as source of agar for commercial use.
Carcinoma-associated fibroblasts (CAF) promote tumor progression of pre-neoplastic epithelial cells. To investigate the basis of this phenomenon, we compared the properties of fibroblasts cultured from normal human prostate (NHPF) to prostate CAF. NHPF and CAF were assayed for growth potential, cell death and proliferative capacity by measuring population doubling time, cell cycle distribution and capability to form colonies in soft agar. Resistance to genotoxic (UV radiation: 0-50 J/cm2) and chemotoxic (0-200 nM Taxol) agents were compared between CAF and NHPF by measuring cell viability and cell cycle analysis. Transforming growth factor beta1 (TGF-beta1) immunoreactivity was assessed in non-malignant and malignant prostatic tissue. No detectable differences were found when comparing CAF and NHPF with respect to population doubling time, cell cycle distribution and response to genotoxic and chemotoxic agents. The mean number of colonies in soft agar was 120.5 for CAF vs. 18.2 for NHPF (p < 0.05). Because TGF-beta1 and matrix metalloproteinase (MMP)-9 have been associated with growth of fibroblasts in soft agar and tumor promotion, we measured the expression of these factors in NHPF and CAF by ELISA. There was no difference in expression of MMP-9; however, TGF-beta1 was expressed in higher concentrations in CAF than in NHPF (p < 0.0014). Furthermore, TGF-beta1 expression was higher in the carcinoma-associated stroma of prostate cancer tissue than stroma of non-malignant prostatic tissue. Increased capability of CAF as compared to NHPF to form colonies in soft agar may be due to a higher expression of TGF-beta1 and correlates with the ability of CAF to promote malignant progression of prostate epithelial cells.