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1.
S H Tsang  L S Kan 《Cell biophysics》1990,16(3):127-138
The nuclear magnetic resonance spin-lattice (T1) and spin-spin (T2) relaxation times are closely related to the molecular motions of the molecules in a liquid sample. T1 and T2 of human epidermal cells were measured at 300 MHz as functions of harvesting methods (i.e., scraping vs trypsinization) and age in culture. It was found that T1 and T2 values have smaller variances when the cell is harvested by trypsinization rather than scraping. The correlation coefficients for both T1 and T2, obtained from cells harvested by scraping. More importantly, this is the first report to monitor in vitro aging through relaxation times measurement. There is a significant increase in the values of T1 and T2 from the third to seventh passages. Human keratinocytes slowed down and even ceased to grow the seventh passage. Therefore, the cellular water molecules of human keratinocytes have higher mobility in a more differentiated state. The factors contributing to the change in relaxation times as cells progress toward senescence are discussed.  相似文献   

2.
Frequency-dependent values of the spin-lattice relaxation time (T1) and the spin-spin relaxation time (T2) have been obtained for intracellular water in normal and transformed Syrian hamster fetal fibroblasts. Values of T1 and T2 were obtained for normal and transformed cells at 24.3 (0.57 T), 100 (2.4 T), 300 (7.0 T), and 400 MHz (9.4 T). At each frequency, values of T1 were the same for both normal and transformed cells, whereas values of T2 were lower for one passage of transformed cells. As expected, T1 increased with frequency. However, T2 decreased with frequency for both normal and transformed cells. The frequency dependence of T2, was similar for all cells; thus, the ability of T2 to make a distinction between normal and transformed cells did not change with field.  相似文献   

3.
The nuclear magnetic resonance (NMR) parameters, spin-lattice (T1), and spin-spin (T2) relaxation time, are usually longer for neoplastic cells than for normal cells of the same cell type. This has generally been true at low NMR frequencies (≤100 MHz) when comparisons have been made between normal and neoplastic cells that have both spent a short time in culture. We have previously demonstrated that although the T1 values of paired normal and neoplastic Syrian hamster (SH) fibroblastic cells in culture are not significantly different when measured at 300 MHz, the 300 MHz T2 values for the neoplastic cells are smaller than those of the normal cells. (Xin et al. (1986),Cell Biophysics 8, 213.) Since treatment of normal diploid cells with polypeptide growth factors or tumor promoters frequently results in reversible expression of neoplasia-associated phenotypes, T1 and T2 were obtained at 300 MHz for treated and untreated SH cells to see if these compounds could also produce smaller 300 MHz T2 values. Secondary culture SH fetal fibroblast cells were treated with epidermal growth factor (EGF), fibroblast growth factor (FGF), phorbol-12,13-didecanoate (PDD) and 4-α-phorbol-12,13-didecanoate (4αPDD). Treatment with either growth factor resulted in smaller T2 values, but a statistically significant decrease was not observed for PDD or 4αPDD. The observed reductions in T2 values were correlated with the morphological and growth-stimulatory effects of these compounds on the cells.  相似文献   

4.
The relaxation rates (1 / T 1 and 1 / T 2) in cysts have already been analyzed in terms of materials such as albumin, cholesterol, manganese, iron, and copper. However, the relaxivities of these materials have not been determined yet. In this work, five sets containing the ions, albumin, and cholesterol were prepared by addition of increasing concentration of one material to each set. The relaxation times in these sets were measured by MRI, and the relaxation rates were fitted versus concentrations. The slopes of the fits were used as relaxivities. The (r 1, r 2) values of manganese, iron, and copper in mM−1 s−1, and those of albumin and cholesterol in (g/dl)−1 s−1 were found to be (32.64, 89.77), (0.31, 1.19), (0.5, 1.479), (0.01, 0.066) and (0.03, 0.458), respectively. The r 2/r 1 ratio ranged from 2.75 to 15.27. Manganese is an efficient relaxer, but iron and copper are poor ones. Albumin and cholesterol are efficient relaxers for only T 2. The contribution of water associated with native manganese of the cystic fluid to T 1 was 0.268 s−1, whereas those of water associated with native manganese, albumin, cholesterol, and iron to T 2 were 0.736, 0.185, 0.092, and 0.076 s−1, respectively. The other contributions were much smaller than 0.076 s−1. Manganese is most likely the compound altering T 1-weighted images between different jaw cysts, whereas manganese and albumin are most likely the compounds altering the T 2-weighted images. Present data suggest that such alterations may be used to separate jaw cysts from other jaw masses. The high r 2/r 1 suggests that T 2 is a more convenient parameter than T 1 for diagnostic use. This work is a part of the PhD thesis of U. Nezih Yilmaz supervised by R. Guner.  相似文献   

5.
TheT 1 andT 2 relaxation times of water protons in two cell types in culture derived from Syrian hamster fetuses (normal primary or secondary fetal cells vs BP6T tumor cells derived from the normal cells transformed by carcinogens) were measured at 7.05 Tesla magnetic field (proton frequency =300 MHz). TheT 1/T 2 ratios and the correlation time, τ c , calculated from theT 1/T 2 ratio of cellular water protons, are significantly different in these two fibroblastic cell types of the same biological origin and with similar morphologies and growth rates in culture.  相似文献   

6.
BackgroundCancer cells often have altered iron metabolism relative to non-malignant cells with increased transferrin receptor and ferritin expression. Targeting iron regulatory proteins as part of a cancer therapy regimen is currently being investigated in various malignancies. Anti-cancer therapies that exploit the differences in iron metabolism between malignant and non-malignant cells (e.g. pharmacological ascorbate and iron chelation therapy) have shown promise in various cancers, including glioblastoma, lung, and pancreas cancers. Non-invasive techniques that probe tissue iron metabolism may provide valuable information for the personalization of iron-based cancer therapies. T2* mapping is a clinically available MRI technique that assesses tissue iron content in the heart and liver. We aimed to investigate the capacity of T2* mapping to detect iron stores in soft tissue sarcomas (STS).MethodsIn this study, we evaluated T2* relaxation times ex vivo in five STS samples from subjects enrolled on a phase Ib/IIa clinical trial combining pharmacological ascorbate with neoadjuvant radiation therapy. Iron protein expression levels (ferritin, transferrin receptor, iron response protein 2) were evaluated by Western blot analysis. Bioinformatic data relating clinical outcomes in STS patients and iron protein expression levels were evaluated using the KMplotter database.ResultsThere was a high level of inter-subject variability in the expression of iron protein and T2* relaxation times. We identified that T2* relaxation time is capable of accurately detecting ferritin-heavy chain expression (r = -0.96) in these samples. Bioinformatic data acquired from the KMplot database revealed that transferrin receptor and iron-responsive protein 2 may be negative prognostic markers while ferritin expression may be a positive prognostic marker in the management of STS.ConclusionThese data suggest that targeting iron regulatory proteins may provide a therapeutic approach to enhance STS management. Additionally, T2* mapping has the potential to be used a clinically accessible, non-invasive marker of STS iron regulatory protein expression and influence cancer therapy decisions that warrants further investigation. Level of Evidence: IV  相似文献   

7.
Circulatory levels of triiodothyronine (T3) and thyroxine (T4) and their kinetics were studied in rabbits exposed to intermittent hypobaric hypoxia (5200 m, 395 mm Hg,PO2 83 mm Hg) 6 h daily for 5 weeks in a decompression chamber maintained at room temperature of 22°–24° C. Kinetics of T3 and T4 were studied on days 21 and 28 of hypoxic exposure. The T3 and T4 values were found to be significantly lower on day 8 of exposure to hypoxia compared to the pre-exposure values. The decreased levels were maintained throughout the entire period of hypoxic stress. The metabolic clearance rate, production rate, distribution space and extrathyroidal T3 and T4 pools were significantly decreased in animals under hypoxic stress compared to the control animals. The decline in thyroid hormone levels and their production in rabbits under hypoxic stress indicate an adaptive phenomenon under conditions of low oxygen availability.  相似文献   

8.
Relaxation measurements of side-chain 13CH2-groups of uniformly 13C labeled human ubiquitin were performed at 600 MHz and 800 MHz magnetic field strength at 30°C. Dipole-dipole cross-correlated relaxation effects in T1 experiments were suppressed by the combination of radio-frequency pulses and pulsed field gradients during the relaxation delay leading to monoexponential relaxation decays that allow a more accurate extraction of the 13C T1 relaxation times. Heteronuclear 1H-13C NOEs obtained by using different proton saturation schemes indicate that the influence of cross-correlation is small. The experimental T1 and NOE data were interpreted in a model-free way in terms of a generalized order parameter and an internal correlation time.  相似文献   

9.
Current MR methods use T2? relaxation time as a surrogate measure of ligament strength. Currently, a multi-echo voxel-wise least squares fit is the gold standard to create T2? maps; however, the post-processing is time-intensive and serves as a stopgap for clinical use. The study objective was to determine if an alternative method could improve post-processing time without sacrificing fidelity of T2? values for eventual translational use in the clinic. Using a 6 echo FLASH sequence, three different methods were used to determine intact posterior cruciate ligament (PCL) median T2? Two of these methods utilized a voxel-wise method to establish T2? maps: (1) a current “gold standard” method using a voxel-wise 6 echo least-squares fit (6LS) and (2) a voxel-wise 2 echo point T2? determination (2MM). The third method used median ligament signal intensity and a single nonlinear least-squares fit (6LSROI) instead of a voxel-wise basis. The resulting median T2? values of the PCL and computational time were compared. The median T2? values were 42% higher using the 2MM compared to the 6LS method (p<0.0001). However, a strong correlation was found for the median T2? values between the 2MM and 6LS methods (R2=0.80). The median T2? values were not significantly different between the 6LS and 6LSROI methods (p=0.519). Using the 2MM (which provides a regional map) and the 6LSROI (which efficiently provides the median T2? value) methods in tandem would take only minutes of post-processing computational time compared to the 6LS method (~540 min), and hence would facilitate clinical application of T2? maps to predict ligament structural properties as a patient outcome measure.  相似文献   

10.
The aim of present study was to investigate the effects of 3,3′,5-triiodothyronine (T3) on rat testis both morphometrically and immunohistochemically with determining of insulin-like growth factor I (IGF-I) expression. Adult male Wistar-albino rats used in the study were divided into two groups; control and T3-treated groups. After T3 treatment there was observed to be a decrease in testicular weights, diameters of seminiferous tubules and the number of sertoli cells, and an increase in the number of leydig cells (P<0.05). Some of the seminiferous tubule lumens of T3 administrated rats had cellular debris. IGF-I was localized in sertoli cells, late spermatids and leydig cells of all groups. IGF-I immunoreactivity in T3 treated rats was higher than in controls in all stages of the cycle of rat seminiferous epithelium, but the staining intensity of leydig cells were similar in both groups. In conclusion, the present results suggest that T3 may modulate the testicular function by affecting IGF-I activity at the gonadal level.  相似文献   

11.
Summary The solvent-exposed regions of [U-13C]ascomycin when bound to its putative target protein; FKBP, have been identified based on the different proton longitudinal relaxation rates (R1 = 1/T1) measured in the absence and presence of the paramagnetic relaxation reagent, 4-hydroxy-2,2,6,6-tetramethyl-piperidinyl-I-oxy (HyTEMPO). The proton T1s of bound ascomycin were determined using a pulse sequence (T1-HMQC) which consists of a 180° proton pulse and a variable delay () followed by a heteronuclear multiple quantum correlation (HMQC) experiment. The solvent-exposed regions of ascomycin determined by these experiments are compared to NOE data in which ascomycin/FKBP contacts were identified and to the X-ray structure of the FK-506/FKBP complex.  相似文献   

12.
The effects of equilibration under different air relative humidities (RH, 1 – 90 %) and temperatures (35 and 45 °C) on soybean (Glycine max) and wheat (Triticum aestivum) seeds were studied using different techniques. Seed moisture content, electrical conductivity (EC) of seed leachate and per cent seed germination were measured following standard procedures, and compared with nuclear magnetic resonance spin-spin relaxation time (T2) measurements. Moisture contents of soybean and wheat seeds, following the reverse sigmoidal trend, were greater at 35 than at 45 °C at any particular RH. Changes in T2 were related to the changes in germination percentage and leachate EC of both soybean and wheat seeds. Equilibrating soybean seeds at RH 11 % decreased germination percentage with corresponding decrease in T2. On the contrary, EC of seed leachate increased. In wheat seeds equilibrated at 45 °C, T2 was maximal at RH 5.5 %. T2 declined in seeds equilibrated at high RH (> 80 %) together with low germination percentage.  相似文献   

13.
An in vitro system to screen for diarrheagenic chemicals   总被引:2,自引:0,他引:2  
We examined an in vitro system to screen for diarrheagenic chemicals using an established intestinal cell line (T84 human colonic carcinoma). The cells were grown on Millicell-PCF (polycarbonate membrane) wells. The cells were seeded at approximately 5 × 106 cells/30mm well and incubated for 9–11 days in a 5% C02 incubator saturated with water at 37°C. The culture medium was a 1:1 mixture of Ham's F12 and Dulbecco's MEM with 5% fetal bovine serum and 25 pglml gentamicin sulfate. The well containing cells was removed from the incubator and mounted in a modified Ussing chamber for measurement of shortcircuit current (Isc). Chemical-induced increases in Psc are usually indicative of electrogenic epithelial Cl secretion, which is associated with diarrheagenic effects in animals and humans. T84 cells grown on Millicell-PCF membrane responded with an increase in Isc after basolateral addition of the cholinergic (muscarznic) agonist carbachol, prostaglandin E2, 16,16-dimethylprostaglandin E2, and forskolin, while non-diarrheagenic prostaglandin D2 did not affect Isc. Based on our results, this in vitro system has the potential to be adapted as a rapid screen for detecting diarrheagenic chemicals.Abbreviations dmPGE2 16,16-dimethylPGE2 - EC50 50% of maximum effective concentration - EDTA ethylenediaminetetraacetate - ISC short-circuit current - PGD2 prostaglandin D2 - PGE2 prostaglandin E2 - PD potential difference - RT transepithelial resistance  相似文献   

14.
Remote measurements of body temperature (Tb) in animals require implantation of relatively large temperature-sensitive radio-transmitters or data loggers, whereas rectal temperature (Trec) measurements require handling and therefore may bias the results. We investigated whether ∼0.1 g temperature-sensitive subcutaneously implanted transponders can be reliably used to quantify thermal biology and torpor use in small mammals. We examined (i) the precision of transponder readings as a function of temperature and (ii) whether subcutaneous transponders can be used to remotely record subcutaneous temperature (Tsub). Five adult male dunnarts (Sminthopsis macroura, body mass 24 g) were implanted with subcutaneous transponders to determine Tsub as a function of time and ambient temperature (Ta), and in comparison to thermocouple readings of Trec. Transponder temperature was highly correlated with water bath temperature (r2=0.96–0.99) over a range of approximately 10.0–40.0 °C. Transponders provided reliable data (±0.6 °C) over the Tsub of 21.4–36.9 °C and could be read from a distance of up to 5 cm. Below 21.4 °C, accuracy was reduced to ±2.8 °C, but individual transponder accuracy varied. Consequently, small subcutaneous transponders are useful to remotely quantify thermal physiology and torpor patterns without having to disturb the animal and disrupt torpor. Even at Tsub<21.4 °C where the accuracy of the temperature readings was reduced, transponders do provide reliable data on whether and when torpor is used.  相似文献   

15.
Agonist activation of the hP2Y1 receptor expressed in Xenopus oocytes stimulated an endogenous voltage-gated ion channel, previously identified as the transient inward (Tin) channel. When human P2Y1 (hP2Y1) and skate P2Y (sP2Y) receptors were expressed in Xenopus oocytes, time-to-peak values (a measure of the response to membrane hyperpolarization) of the Tin channel were significantly reduced compared to oocytes expressing the hB1-bradykinin receptor or the rat M1-muscarinic (rM1) receptor. Differences in activation were also observed in the Tin currents elicited by various P2Y receptor subtypes. The time-to-peak values of the Tin channel in oocytes expressing the hP2Y4, hP2Y11, or hB1-bradykinin receptors were similar, whereas the channel had significantly shorter time-to-peak values in oocytes expressing either the hP2Y1 or sP2Y receptor. Amino acid substitutions at His-132, located in the third transmembrane domain (TM3) of the hP2Y1 receptor, delayed the onset of channel opening, but not the kinetics of the activation process. In addition, Zn2+ sensitivity was also dependent on the subtype of P2Y receptor expressed. Replacement of His-132 in the hP2Y1 receptor with either Ala or Phe increased Zn2+ sensitivity of the Tin current. In contrast, truncation of the C-terminal region of the hP2Y1 receptor had no affect on activation or Zn2+ sensitivity of the Tin channel. These results suggested that TM3 in the hP2Y1 receptor was involved in modulating ion channel function and blocker pharmacology of the Tin channel.  相似文献   

16.
The influence of silicon-treatment on the levels of TSH and thyroid hormones was studied in rats. Concentrations of thyrotropin (TSH), triiodothyronine (T3), and thyroxine (T4) were estimated in sera of rats receiving per os a soluble silicon compound—sodium metasilicate nonahydrate (Na2SiO3·9H2O), dissolved in the animals' drinking water. An increase in the TSH level in the tested group was observed, without statistically significant differences in T3 and T4 concentrations between the two groups of animals. The results provide evidence for the influence of silicon on the endocrine balance. They could also prove that this chemical element is capable of modifying the rate of some hormones' synthesis.  相似文献   

17.
The 15N steady-state magnetization in the presence of off-resonance rf irradiation is an analytical function of the T1/T2 ratio and of the angle between the 15N effective field axis and the static magnetic field direction. This relation holds whatever the relaxation mechanisms due to motions on the nanosecond time scale, and the size of the spin system. If motions on the micro- to millisecond time scale are present (fast exchange), the same observable depends also on their spectral density at the frequency of the effective field. The cross-peak intensity in each 2D 15N-1H correlation map is directly related to the dynamic parameters, so that the characterization of fast exchange phenomena by this method is in principle less time-consuming than the separate measurement of self-relaxation rates. The theory of this approach is described. Its practical validity is experimentally evaluated on a 15N-labeled 61 amino acid neurotoxin. It turns out that existing equipments lead to non-negligible biases. Their consequences for the accuracy attainable, at present, by this method are investigated in detail.  相似文献   

18.
Regional cerebral metabolite concentrations, principally of choline-containing compounds (Cho), total creatine (Cr), N-acetylaspartate (Naa), and lactate (Lac), can be quantified by in vivo proton magnetic resonance spectroscopy. In order to estimate a metabolite concentration, it is often necessary to measure the transverse relaxation time (T2). Metabolite T2s depend on cytosolic viscosity: as [adenosine triphosphate] falls leading to Na+/K+ pump failure, cytosolic water increases and T2s lengthen. In central grey-matter in human infants, Naa may be almost exclusively neuronal: Naa T2 may index neuronal edema and energy generation. In this preliminary report, metabolite concentrations and T2s have been measured in central grey matter in human infants suspected of perinatal hypoxic-ischemic cerebral injury. In infants who developed serious cerebral injury or died, [Cho] and [Naa] were low (the latter suggesting neuronal loss), [Lac] and all metabolite T2s were increased: the Naa T2 increase possibly reflected neuronal edema following failure of energy generation in a fraction of remaining neurons. Special issue dedicated to Dr. Herman Bachelard.  相似文献   

19.
Nuclear receptors for the thyroid hormone triiodothyronine (T3) have been identified in vivo in brain tissues and in vitro in mouse and rat neuroblastoma and glioma cells. The present study characterizes nuclear T3 receptors in human neuroblastoma SH-SY5Y cells and compares their levels before and after differentiation. Undifferentiated cells, grown in DME/HAM F-12 medium supplemented with 10% fetal calf serum, show an abundant single type of nuclear receptor, indicated by a straight Scatchard plot, with aK d of 0.11 nmol/l. After treatment with sodium butyrate (0.5 mM for 4 days) or NGF (2 nM for 6 days), the cells showed neuronal-like patterns (extension of neurites, slowing of growth, increased tyrosine hydroxylase activity), with a decrease in the number of nuclear T3 receptors. As sodium butyrate and NGF treatments differentiate neuroblastoma SH-SY5Y cells, these data suggest a down-regulation of T3 receptors with cell maturation.  相似文献   

20.
T4, T3 and TSH serum levels were measured in 25 patients with paracoccidioidomycosis. Thyroid T3 reserves were measured on the basis of the increase in T3 (T3) 2 h after intravenous injection of 200 g TRH, and pituitary TSH reserves were measured on the basis of TSH increase (TSH) 20 min after the same injection. Twenty healthy volunteers with no history of thyroid disease were used as controls. When the two groups were compared, the following results were obtained: (a) there was no significant difference in mean T4, T3, TSH between groups; (b) reduced T3 levels were detected more frequently in patients with paracoccidioidomycosis, especially among those with the acute form of the disease or with the severely disseminated chronic form. The results suggest the occurrence of a reduction in peripheral conversion of T4 to T3, but do not indicate the occurrence of hypothyroidism in any of its forms (thyroid, pituitary or hypothalamic).  相似文献   

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