Significant Difference In Absorbance Research Articles

Acceleration of Polybutylene Succinate Biodegradation by Terribacillus sp. JY49 Isolated from a Marine Environment.

Polybutylene succinate (PBS) is a bioplastic substitute for synthetic plastics that are made from petroleum-based products such as polyethylene and polypropylene. However, the biodegradation rate of PBS is still low and similar to that of polylactic acid (PLA). Moreover, our knowledge about degrader species is limited to a few fungi and mixed consortia. Here, to identify a bacterial degrader to accelerate PBS degradation, we screened and isolated Terribacillus sp. JY49, which showed significant degradability. In order to optimize solid and liquid culture conditions, the effect of factors such as temperature, additional carbon sources, and salt concentrations on degradation was confirmed. We observed a degradation yield of 22.3% after 7 days when adding 1% of glucose. Additionally, NaCl was added to liquid media, and degradation yield was decreased but PBS films were broken into pieces. Comparing the degree of PBS degradation during 10 days, the degradation yield was 31.4% after 10 days at 30 °C. Alteration of physical properties of films was analyzed by using scanning electron microscopy (SEM), gel permeation chromatography (GPC), and Fourier transform infrared (FT-IR). In addition, Terribacillus sp. JY49 showed clear zones on poly(butylene adipate-co-terephthalate) (PBAT), polycaprolactone (PCL), and copolymers such as P(3HB-co-3HV) and P(3HV-co-4HB), exhibiting a broad spectrum of degradation activities on bioplastics. However, there was no significant difference in absorbance when esterase activity was examined for different types of bioplastics. Overall, Terribacillus sp. JY49 is a potential bacterial strain that can degrade PBS and other bioplastics, and this is the first report of Terribacillus sp. as a bioplastic degrader.

Alterations in structure of biomolecules using ATR-FTIR and histopathological variations in brain tissue of Channa punctatus exposed to 2Naphthalene sufonate.

2Naphthalene sulfonate (2NS) is an intermediate compound used in textile industries. Being nonbiodegradable, the concerns regarding its biotoxicity have risen. In the present investigation the toxic effects of 2NS were analyzed with the help of Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR), which was used to monitor changes in the vibrational modes of functional groups within the biomolecules. After calculating LD 50, one half of LD 50 i.e. 0.33mg/15g b.w. was intraperitoneally administrated and the brain tissue was collected for investigation after 96h of exposure. The spectra observed revealed the significant differences in absorbance and areas between control and treated groups reflecting the change in proteins, lipids and nucleic acid due to toxicity induced by 2NS. In addition, protein secondary structure analysis was focused in this study, which reveals alterations in α helix and β sheet structure after 2NS intoxication. Histopathology of brain was also studied, which reveals changes in the histology of brain in group treated with 2NS. In conclusion, the study highlighted the application of ATR-FTIR and histopathology for toxicity assessment.

Screening for antioxidant activity of vegetable and fruit by-products and evaluating the ability of coffee sediment to preserve fish meal

In this study, we collected and prepared ethanol extracts from 30 vegetable and fruit by-products and screened for antioxidant activities using three methods, including determination of total phenolic content (TPC), 2,2-diphenyl-1-picrylhydrazyl free radical scavenging assay (DPPH assay), and ferric reducing/antioxidant power assay (FRAP assay). The coffee sediment (TN-16) and ginger peel extract (TN-17) showed vigorous activities and higher than those of other samples (p < 0.05). The TPC in TN-16 and TN-17 were 66.14 mgGAE/g and 146.52 mgGAE/g, respectively. For the DPPH assay, the IC50 inhibited the values of 16.73 µg/mL with TN-17 and 33.57 µg/mL with TN-16. For the FRAP, a significant difference in absorbance was observed between all samples (p < 0.05), and TN-16 and TN-17 have strong activities with higher absorbances. Besides, fifteen compounds may present in TN-16 namely, metiamide, manitol, 3-amino phenol, malicyamide, phenyl ethanolamine, 3-methoxyamphetamine, caffeine, nisoldipine, doxenitoin, dicyclohexyl phthalate, febuprol, 2.4 xylidine, glycerol 2-palmitate, 4-(benzylamino) phenol, o-toluidine were identified by HPLC-EIS-MS. In addition, the coffee sediment extract was investigated the ability to preserve fish meal in 30 days at the room temperature. The result showed that the coffee sediment was the potent extract for the protection of fish meal against lipid peroxidation as compared to synthetic antioxidants.

Mechanical properties and cell compatibility of a chitosan-graphene oxide guided bone regeneration composite membrane

Objective: To explore the feasibility of graphene oxide (GO)-chitosan (CS) guided bone regeneration composite membrane being used as a new guided bone regeneration (GBR) membrane by testing its tensile strength and its effect on the proliferation of human gingival fibroblasts (HGF). Methods: The CS solution and GO solution were mixed in following ratios, ultrasonically crushed and dispersed, and formed into membranes by self-evaporation. Composite membrane with 0.5%, 1.0%, 2.0%, 4.0%, 6.0%, 8.0% GO in CS was prepared. The tensile strength of the composite membranes was tested by mechanical universal testing machine (n=6). The microstructure of the composite membrane with the best tensile strength was observed by scanning electron microscopy and transmission electron microscopy. X-ray diffraction was used to characterize the ingredients of the material. A group of samples was prepared again with the proportion of the highest tensile strength composite membrane, and were immersed in a sodium hydroxide solution for acid removal. The tensile strength of the new group of samples was tested. The newly extracted impacted teeth were collected from the Department of Oral and Maxillofacial Surgery, Stomatologic Hospital and College, Anhui Medical University, and the gingival tissues remained on the teeth were taken for primary HGF and were cultured to P2 generation, which were identified by immunocytochemical staining methods. Cell counting kit-8 (CCK-8) was applied to detect cell counts in the blank control group, the pure CS membrane group, and the composite membrane group with the highest tensile strength (n=5) and all groups co-cultured with the HGF for 24 h and 48 h. Results: After adding GO, the cross-section of the composite membrane was in an ordered layer structure. X-ray diffraction analysis showed that GO could be found in the composite membrane. The tensile strength increased with the increase of GO ratio. When the mass fraction of GO in CS was 4.0%, the tensile strength reached (134.8±7.3) MPa and the tensile strength reached (144.6±8.1) MPa after deacidification of the composite membrane. The CCK-8 test of HGF showed that there was no significant difference in absorbance between the pure CS membrane group and the GO/CS composite membrane group when they were compared with the blank control group (P>0.05). Conclusions: When the mass fraction of GO in CS is 4.0%, the composite membrane has the best tensile strength. The composite membrane showes good cytocompatibility, which lays a foundation for further in vivo experiments and the development of a new generation of GBR membrane.

Examination of particle dispersion when saline concentrate is released in septic tank wastewater

Soil dispersion due to salinization is an important concern associated with the land application of saline wastes. When residual brine is transferred to septic systems, dispersion of sludge can lead to complications, as well. This study investigated sludge and microbial population response of septic wastewater during residual saline application. Salinity concentration up to 10 ppt (‰) was included, within the range of residual saline waters in the region. The dominant salt cations by order of decreasing concentration were Na, Ca, and Mg. The initial heterotrophic microbial population was lowest for all control and treatments in the log 4.5–4.8 cfu mL−1 range. A regrowth period followed towards the end of the experiment commonly reaching log 6 cfu mL−1. UV absorbance was used to quantify dispersion of solids and treatments produced statistically significant differences in absorbance. This work shows the importance of considering the consequences of saline application to waste.

Effects of cryopreservation on biological characteristics of tendon-derived stem cells in rat patellar tendon

To explore the effects of cryopreservation on the cell survival rate, cell viability, early apoptosis, migration ability, and tendon-related marker expression of tendon-derived stem cells (TDSCs) in rat patellar tendons. The patellar tendon tissues were harvested from 12 4-month-old male Sprague Dawley rats; 12 patellar tendon tissues from 6 rats were cryopreserved (the experimental group), and the other 12 patellar tendon tissues were not treated (the control group). The patellar tendons were digested with 0.3% type I collagenase to obtain nucleated cells. The survival rate of nucleated cells was detected by trypan blue exclusion assay, and colony-forming ability by crystal violet staining. TDSCs were isolated and cultured to passage 3 (P3). The cell viability of TDSCs was detected by Alamar Blue method, the early apoptosis by Annexin V-FITC/PI assay, the cell migration ability by Transwell method, and the mRNA expressions of tendon-related markers [collagen type I (Col1α1), scleraxis (Scx), and tenomodulin (Tnmd)] by real-time quantitative PCR. The survival rate of nucleated cells was 91.00%±3.63% in the control group, and was 61.65%±4.76% in the experimental group, showing significant difference ( t=12.010, P=0.000). The formation of the primary nucleated cell clones was observed in 2 groups. At 12 days, the number of colonies forming of the experimental group [(8.41±0.33)/1 000 nucleated cells] was significantly lower than that of the control group [(15.19±0.47)/1 000 nucleated cells] ( t=28.910, P=0.000). The percentage of TDSCs in the active nucleated cells in the experimental group (1.37%±0.09%) was significantly lower than that in the control group (1.67%±0.10%) ( t=5.508, P=0.003). The growth trend of TDSCs (P3) in the 2 groups was consistent within 14 days. There was no significant difference in absorbance ( A) value between 2 groups at each time point ( P>0.05). The early apoptotic rate of TDSCs was 1.67%±0.06% in the experimental group and was 1.63%±0.06% in the control group, showing no significant difference ( t=0.707, P=0.519). Under microscope, TDSCs adhered to the lower chamber of the Transwell chamber; the number of cells was 445.00±9.70 in the experimental group and was 451.50±12.66 in the control group, showing no significant difference ( t=0.998, P=0.342). The relative mRNA expressions of Col1α1, Scx, and Tnmd were 3.498±0.065, 0.062±0.002, and (4.211±0.211)×10 -5 in the experimental group and were 3.499±0.113, 0.062±0.001, and (4.341±0.274)×10 -5 in the con-trol group, showing no significant difference ( t=0.013, P=0.991; t=0.042, P=0.969; t=0.653, P=0.549). The survival rate of nucleated cells in cryopreserved rat tendon tissues is lower, but a large number of active TDSCs, and its cell viability, early apoptosis rate, migration ability in vitro, and cell tenogenic differentiation ability are remained.

The bisphenol A-enhanced activity of thyroid carcinoma cell line B-CPAP is inhibited by Icarrin

Objective: To investigate the effect of icariin (ICA) on the bisphenol A (BPA)-enhanced proliferation function of thyroid carcinoma cell B-CPAP and underlying mechanism. Methods: The proliferation of Gastric B-CPAP cell line was evaluated by cell counting kit-8 (CCK-8). Apoptosis and ROS expression in B-CPAP cells were detected by flow cytometry. The expression of superoxide dismutase (SOD) and malondialdehyde (MDA) in B-CPAP cells were measured by individual assay kits. The expressions of Bcl-2 and γ-HA2X were detected by Western blot. SPSS 18.0 software was used to analyze the data. Results: B-CPAP cell activity was promoted by treatment with 3×10(-7)mol/L BPA for 48 h, with significant difference in absorbance between BPA and control groups (1.089±0.053 vs 0.935±0.010, P<0.05). The cell activities of BPA+ ICA(25), BPA+ ICA(50), BPA+ ICA(100) and BPA+ ICA(200) groups was 0.780±0.036, 1.007±0.050, 0.958±0.033 and 0.625±0.064, respectively (all P<0.01). The proliferation of B-CPAP cells treated with BPA for 72 hours showed a similar trend to 48 hours. There was no significant difference between all treatment groups in 24 hours. The apoptosis rate was (19.272±0.186)% in BPA-treated cells, and was (22.412±0.238)% in control cells (P<0.05). The apoptosis rates of BPA+ ICA(50) and BPA+ ICA(200) groups were (23.688±0.412)% and (30.270±0.696)%, respectively (P<0.01). The intracellular accumulation of ROS in BPA, BPA+ ICA(50), and BPA+ ICA(200) groups were 806±21, 1 772±37, 2 041±16, respectively (P<0.01). The expressions of anti-apoptotic protein Bcl-2 in control, BPA, BPA+ ICA(50), BPA+ ICA(200) groups were 7 120±151, 9 801±286, 5 902±171 and 4 203±216, respectively (P<0.01). Conclusion: BPA can promote the proliferation of thyroid carcinoma B-CPAP cells and decrease the apoptosis of cells, and this effect can be inhibited by ICA. The possible mechanism is to induce high expression of intracellular ROS and inhibit the expression of antioxidase system, leading to cell oxidative damage, thereby inducing apoptosis.

Biofilm Formation on Different Materials Used in Oral Rehabilitation.

The aim of this study was to evaluate the density and the morphological aspects of biofilms adhered to different materials applied in oral rehabilitation supported by dental implants. Sixty samples were divided into four groups: feldspar-based porcelain, CoCr alloy, commercially pure titanium grade IV and yttria-stabilized zirconia. Human saliva was diluted into BHI supplemented with sucrose to grow biofilms for 24 or 48 h. After this period, biofilm was removed by 1% protease treatment and then analyzed by spectrophotometry (absorbance), colony forming unit method (CFU.cm-2) and field-emission guns scanning electron microscopy (FEG-SEM). The highest values of absorbance and CFU.cm-2 were recorded on biofilms grown on CoCr alloys when compared to the other test materials for 24 or 48 h. Also, FEG-SEM images showed a high biofilm density on CoCr. There were no significant differences in absorbance and CFU.cm-2 between biofilms grown on zirconia, porcelain and titanium (p<0.05). Microbiological assays associated with microscopic analyses detected a higher accumulation of oral biofilms on CoCr-based materials than that on titanium or zirconia that are used for prosthetic structures.

Factors influencing circulating MicroRNA level in the studies of hepatocellular carcinoma biomarker.

Factors influencing circulating miRNA as adiagnostic marker of hepatocellular carcinoma (HCC) are still unknown. We used two kits to extract total RNA of 90 paired serum and plasma samples of volunteers in different statuses including healthy, hepatitis, cirrhosis and HCC. U6, miR-183 and cel-miR-39 expression levels were detected by qRT-PCR. Calculate was the relative expression level of miR-183 and recovery of cel-miR-39 with 2-∆∆CT method and standard curve method, respectively.MiRNeasy Serum/Plasma Kit was superior to miRcute miRNA Isolation Kit in the quality of the total RNA and the expression levels of U6 and miR-183, with recovery of external reference cel-miR-39 of the former in serum and plasma was the latter's 3.95-fold and 3.15-fold, respectively. The recovery of cel-miR-39 was significantly higher in serum than that in plasma in all groups except the HCC. But the trend of U6 expression of four groups in serum was different from that in plasma. There were significant differences in absorbance in 260nm, the ratio of absorbance in 260nm and 280nm (260/280), the ratio of absorbance 260nm and 230nm (260/230), the ct value of ​​U6 and the recovery of cel-miR-39 among groups in serum or plasma. Sensitivity and specificity of miR-183 as adiagnostic marker of HCC were 57.9% and 76.2% in serum, and 78.9% and 81.0% in plasma, respectively.Caution should be taken when comparing miRNA data generated from different extraction kits, sample types or disease statuses in the study of miRNA as adiagnostic marker of HCC.

Watercress‐based gold nanoparticles: biosynthesis, mechanism of formation and study of their biocompatibility in vitro

To avoid the potential adverse effects of chemically-synthesised gold nanoparticles (AuNPs), a new method is developed for their biosynthesis using watercress total extract (WTE) and it is compared it with the citrate-based method. Synthesised AuNPs were characterised using transmission electron microscopy (TEM), particle size analysis and infrared spectroscopy (FTIR), and the mechanism and biocompatibility of WTE-based AuNPs were evaluated by MTT assay. The colour of the WTE-based AuNPs was directly changed from yellow to deep red without any intermediate colour change and spectrophotometric analysis showed significant differences in absorbance as well as peak surface plasmon resonance of synthesised AuNPs as compared with the use of sodium citrate. Formation of AuNPs in the WTE-based method was faster than the method using citrate. TEM pictures showed similar sizes of the AuNPs obtained by both methods, but WTE-based AuNPs were more spherical and the range of sizes provided minor differences with TEM results. FTIR confirmed the involvement of WTE compounds in the structure of AuNPs during biosynthesis and the MTT assay did not show any considerable anti-growth effect of WTE-based AuNPs on target cells. Hence, it seems clear that WTE-AuNPs could be used for various biological-related purposes including drug delivery, diagnosis and treatment of various diseases.

Study temperature influence in the application of near- infrared reflectance spectroscopy (NIRS) to estimate amylose content of rice

In the application of near-infrared reflectance spectroscopy (NIRS) to estimate amylose content of rice, analysis was performed based on the relationship between absorbance and amylose content. But absorbance is sensitive to environmental temperature. In this study, characteristics of rice spectra collected at different temperatures were studied by comparing the average spectra and standard deviation spectra of rice with same amylose content at the temperature of 5, 10, 15 and 20°C. The results showed that spectra collected at different temperatures had significant difference in absorbance, and spectra acquired at different temperatures had different stabilities. When the environment temperature was 15°C, stability of spectra was better than when the temperature was 5, 10 and 20°C within the range consisting of abundant information. Accuracies of four linear models on calibration set acquired at four temperatures built by partial least square (PLS) were investigated by using validation sets got at four different temperatures to perform cross validation. The results showed that the relation between spectra and amylose content was not linear in the result of temperature’s influence, and non-linear model methodology least square support vector machine (LS-SVM) method was used to establish calibration model on the calibration set acquired at 15°C. The validation results indicated that the non-linear model could predict the amylose content of samples collected at 15°C with high accuracy, and the root mean square error of prediction was 0.62. Meanwhile, non-linear model showed good prediction ability for samples whose spectra were collected at other temperatures. Key words: Amylose content, near-infrared spectroscopy, temperature influence.

A novel bilayered scaffold constructed with cartilage extracellular matrix/acellular bone matrix for osteochondral tissue engineering

Objective To fabricate a novel bilayered scaffold constructed with cartilage extracellular matrix (CECM) and acellular bone matrix (ACBM) for osteochondral tissue engineering.Methods The bone layer of the osteochondral scaffold was prepared using canine bone cancellous bone columns, and the cartilage layer was fabricated using CECM.After CECM microfilaments were decellularized, the biphasic scaffolds were fabricated by soaking the ACBM columns into cylindrical silicon moulds with a 30 g/L CECM suspension using simple freeze-drying method.After the scaffolds were cross-linked, the porosity was measureed.MTT test was also done to assess cytotoxicity of the scaffolds.Canine bone marrow-derived mesenchymal stem cells (BMSCs) were induced by chondrogenic medium and seeded into novel scaffold.Cell proliferation and differentiation were analyzed using inverted microscopy, scanning electron microscopy (SEM)and Dead/Live staining method.Results SEM and Micro-CT revealed a 3-D interconnected porous structure, with the CECM pore diameter of 155 ± 34 μm and the porosity of 91.3% ± 2.0%.Cytotoxicity testing with MTT revealed no significant difference in absorbance among different extracts, showing no cytotoxic effect of the scaffold on BMSCs.Inverted microscopy and SEM showed that the novel scaffold could provide a suitable 3-D environment to support the adhesion, proliferation and differentiation of BMSCs to chondroeytes in culture with chondrogenic medium.Confocal microscopy of cell-scaffold constructs revealed cells with green fluorescence.Conclusion Since the novel CECM/ACBM bilayered integrated osteochondral scaffold has good mircostructure, non-toxicity and good biocompatibility, it may be a suitable candidate as an alternative cell-carrier for osteochondral tissue engineering. Key words: Tissue engineering; Extracellular matrix; Bone marrow cells; Scaffold

The effect of strontium incoporated with hydroxyapatite on osteoblastic differentiation of bone masenchymal stromal cells

Objective To determine if strontium-containing hydroxyapatite (Sr-HA) will favor osteoblastic differentiation of bone masenchymal stromal cells (BMSCs). Methods Rat BMSCs were cultured with culture media containing ions released from the strontium-substituted HA ceramics as they dissolved. We had 3 experimental groups and one blank control group. In group A, leaching liquor containing 10 mol% of Sr-HA was used;in group B, leaching liquor containing 5 mol% of Sr-HA was used;in group C,leaching liquor containing 1 mol% of Sr-HA was used;in group D, leaching liquor containing no Sr-HA was used. MTT test, alkaline phosphatase (ALP) activity and osteoblast transcription factor gene (Cbfα1) expression examinations were conducted at different time-points. Results MTT test showed that there were no significant differences in absorbance between the 4 groups after cell culture for 1, 3, 5, 7, 10 days( P ＞ 0. 05),but there were significant differences in absorbance between different time-points within the same group ( P ＜0.05). The ALP activity in groups A and B was significantly greater than in groups C and D ( P ＜ 0. 05) at 6, 9,12, 15 days. At 9 and 12 days, there were significant differences in Cbfα1 mRNA expression between the 4 groups ( P ＜ 0. 05). Compared with the blank control group, Sr-HA groups presented a significant enhancement with regard to ALP activity and Cbfα1 mRNA expression in a concentration-dependent manner. Conclusion Incorportion of strontium in HA ceramics may not promote proliferation of BMSCs, but may stimulate osteoblastic differentiation of BMSCs. Key words: Strontium; Hydroxyapatites; Bone marrow cells; Cell differentiation

The Pertussis Serological Potency Test Collaborative Study to Evaluate Replacement of the Mouse Protection Test

The Pertussis Serological Potency Test (PSPT)—based on in vitro assessment of the humoral immune response against Bordetella pertussis—was developed as an alternative for the Mouse Protection Test (MPT). A small-scale collaborative study was carried out in five laboratories to evaluate the relevance and reliability of the PSPT. The study has been divided into three separate phases, each with its own objective. A pilot-phase study of the antibody detection assay, the 18323-whole cell ELISA (WCE), was included for training purposes. Significant differences in absorbance and antibody concentrations between the laboratories were found. In the Phase I study, the intra-assay, inter-assay and inter-laboratory precisions of the 18323-WCE were assessed. Although a precision of less than 20% was not always established and significant differences in antibody concentrations were found at random throughout the Phase I study, the ranking of the antibody concentrations corresponded well between the laboratories and should warrant a reliable potency estimation of whole cell vaccines (WCV's) in the PSPT. Phase II was a comparative study of the PSPT and the MPT to evaluate the implementation of the PSPT, to demonstrate correlation and to compare the reproducibility and reliability of both tests. The mean antibody concentrations per vaccine dose in the PSPT and the survival of mice in the MPT differed significantly within and between the laboratories. Nevertheless, the potencies of the vaccines under test estimated in both test models did not differ significantly (P>0·05). The PSPT and MPT correlated well in χ2-test of homogeneity within and between the laboratories. The potencies were similar (overall ratio=0·877), but the PSPT is more reproducible and reduces the chance of re-testing due to the smaller 95% confidence intervals. We have demonstrated that the PSPT is a valid model to estimate the potencies of pertussis WCV's from different manufacturers. Moreover, the 18323-WCE is easy to carry out and the intra-assay precision and antibody ranking warrants a reliable potency testing of pertussis WCV's in the PSPT.

Preliminary observations on the recovery of tropical phytoplankton after entrainment

Chlorination is practised for preventing biofouling in the cooling water systems of Madras Atomic Power Station. Results of laboratory experiments on phytoplankton recovery (as measured by absorbance and cell count) showed that the recovery time in process sea water effluents and condenser sea water effluents occurred after 3 and 5 days, relative to the natural intake water. Results also showed increasing dominance of a single phytoplankton species ( Thalassiosira sp.) in the condenser as well as process water during the post recovery period. Significant differences in absorbance, gross primary productivity and total respiration rate were observed between intake water versus condenser water and intake water versus process water.

917-96 In Vitro Inhibition of Smooth Muscle Cell Proliferation by Sterol 27-Hydroxylase Metabolites

Sterol 27-hydroxylase controls side chain oxidation of bile acids and is found in vascular endothelial cells. Two metabolites of this oxidation are 27-hydroxycholesterol (27-OH), which inhibits smooth muscle cell (SMC) proliferation in vivo, and 3β-hydroxy-5-cholestenoic acid (C27). We quantified the inhibitory capacity of both these compounds in vitro using a rabbit aortic SMC preparation. Early passage SMC were grown to confluence, plated at a density of 5,000 cells/well, and synchronized for 24 hrs. The cells were then grown in the presence of Dulbecco's modified Eagle's medium with 5% delipidated fetal calf serum alone (control), in increasing concentrations (10, 20,30 μM) of 27-OH and C27 dissolved in 2-hydroxypropyl-p-cyclodextrin (HPBCD), in an equivalent amount of HPBCD alone (control), and in colchicine (1 mg/dl). Cell proliferation at 24 hrs was measured via formazans formation from the tetrazolium salt MTS by absorbance at OD 490 nm There was no significant difference in absorbance between the control and the HPBCD (absorbance 0.402 ± 0,037 vs 0.400 ± 0.057) or 10 μM concentration 27-OH (0.383 ± 0.0561 or C27 (0.374 ± 0.022) groups. However, concentrations of 20 and 30 μM of 27-0H produced a significant growth inhibition (0.362 ± 0.030 and 0.350 ± 0.021, P &lt; 0.01) compared to controls, as did C27 at 20 and 30 μM (0.357 ± 0.22 and 0.344 ± 0.28, P &lt; 0.01), while the colchicine group exhibit the greatest inhibition (0.125 ± 0021). Thus 27-OH and C27 demonstrated a dose response growth inhibition of SMC, and endothelial sterol 27-hydroxylase may play an important role in modulation of myointimal hyperplasia during the atherosclerotic process.

Dosage du platine par spectrométrie d'absorption atomique: Partie II. Résultats analytiques sur les complexes or-ganométalliques d'intérêt biologique: effet cis-trans

An atomic-absorption spectrometric method is reported for the determination of platinum in a series of platinum complexes, with and without the use of spectrochemical buffers. The use of potassium phosphate and lanthanum chloride as buffer eliminated interference effects. The results were reproducible and accurate Platinum phosphine complexes were easily analysed. The cis and trans PtL 2L ' 2 (L,L ' are ligands) complexes soluble in water gave significant differences in absorbance in the absence of spectrochemical buffers, so that absorbance measurements differentiated cis- and trans-compounds in a given series. The cis-trans effect was also detected in organic solvents.

Effet cis-trans et influence de la structure des complexes de platine en absorption atomique

The influence of some interference inhibitors on the platinum determination by atomic absorption using the standard salt (NH 4) 2[PtCl 4] is discussed. K 3PO 4 or LaCl 3 is used to determine platinum without previous decomposition of the complexes. In the absence of interference inhibitors, a significant difference in absorbance between cis- and trans- complexes is found. The trans- compounds gave higher absorbances than the cis- compounds. The above result was used successfully in determining the geometry of platinum complexes.

Effects of temperature on cobalt glass dosimeters.

The effects of temperature upon the radiation-induced absorbance spectra of cobalt borosilicate glass dosimeters were investigated by subjecting dosimeters to different combinations of preexposure, exposure, and post exposure temperature environments. The dosimeters were exposed to 2 × 104, 105, 5 × 105 and 106R in a 60Co irradiator, and absorbance measurements were taken at 3000 A, 3750 A and 5000 A over a four month study period. No significant difference in absorbance was produced by exposure temperatures within a 0°C to 100°C range, but exposure temperatures beyond 150°C resulted in decreases in absorbance levels. The radiation-induced coloration faded linearly with the logarithm of time following exposure with the fading rates being dependent upon exposure, exposure temperature, storage temperature, and the wavelength at which the absorbance spectra were measured. The coloration was completely removed by a 1 hr heat treatment at 500°C. This clarification treatment did not affect the radiation response of the dosimeters given subsequent exposures.