[Effects of insulin glargine at different times on organ oxidative stress in burned rats with delayed resuscitation]

Objective: To examine the antioxidant effect of low dosage insulin glargine intervention at different time in rats with delayed resuscitation after burn, in order to acquire a better time of antioxidant intervention during delayed resuscitation following burn injury. Methods: With 10 rats in each group, 50 male SD rats were assigned to sham injury group, delayed resuscitation group, immediate post-burn insulin glargine treatment group (immediate treatment group), 2 hours post-burn insulin glargine treatment group(2 h treatment group), and 6 hours post-burn insulin treatment group(6 h treatment group) with random number table. Each treatment group received subcutaneous injections of insulin glargine (1.0 U·kg^-1·d^-1) immediately, two hours and six hours after the burn, while the delayed resuscitation group received the same amount of normal saline six hours after the burn. To imitate delayed fluid resuscitation, the delayed resuscitation group and each therapy group were intraperitoneally injected with normal saline (40 ml/kg) 6 hours after injury. No medicine and fluid resuscitation was administered to the sham injury group. Rats in the sham injury group had their abdominal aortic blood, hearts, and kidney tissues collected immediately after injury, while rats in the other groups had their blood and tissues collected 24 hours later. To analyze the timing of antioxidant intervention, the activities of CuZn-superoxide dismutase (CuZn-SOD), catalase (CAT), glutathione peroxidase (GSH-Px), total antioxidant capacity (T-AOC), xanthine oxidase (XOD) and myeloperoxidase (MPO) in blood glucose and myocardial and renal tissues were measured by spectrophotometry. Results: Compared with the sham group, blood glucose levels in the delayed resuscitation group increased [(10.72±0.80) vs (6.57±0.82)mmol/L,P<0.001], while in the myocardium and kidney, the activities of CuZn-SOD, CAT, GSH-Px and T-AOC decreased (all P<0.05) and the activities of XOD and MPO increased (all P<0.05). Compared with the delayed resuscitation group, blood glucose decreased in the immediate, 2 h, and 6 h treatment groups (all P<0.05). In the immediate and 2 h treatment group, the activities of CuZn-SOD, CAT, GSH-Px and T-AOC in the myocardium and kidney increased(all P<0.05). In the 6 h treatment group, only the activities of GSH-Px in myocardium, CAT and GSH-Px in kidney increased (all P<0.05). Compared with the delayed resuscitation group, in the immediate treatment group, the activities of MPO and XOD in myocardial tissue and XOD in renal tissue decreased (all P<0.05). The activities of MPO and XOD in myocardial and renal tissues of the 2 h treatment group both decreased (all P<0.05). In the 6 h treatment group, the activities of MPO in myocardial tissue and XOD in renal tissue both decreased (all P<0.05). Compared with the immediate treatment group, the activity of GSH-Px in myocardial tissue increased (P<0.05), and the activities of CuZn-SOD, CAT, GSH-Px and T-AOC in renal tissue increased in the 2 h treatment group (all P<0.05). The activities of CuZn-SOD, CAT, GSH-Px and T-AOC in myocardium of 6 h treatment group decreased (all P<0.05). Compared with the immediate treatment group, the activities of XOD and MPO in myocardial tissue and XOD in renal tissue of the 2 h treatment group had no significant difference (all P>0.05), but the activity of MPO in renal tissue decreased (P<0.05). The activities of XOD and MPO in myocardial tissue of the 6 h treatment group increased (all P<0.05). Compared with the 2 h treatment group, the activities of CuZn-SOD, CAT and GSH-Px and T-AOC in myocardium and kidney tissues in the 6 h treatment group decreased (all P<0.05), while the activities of XOD and MPO in myocardium and kidney tissues increased [myocardium: (374±8) vs (290±19) U/g, (0.021 8±0.003 9) vs (0.010 7±0.002 4) U/g, kidney: (157±6) vs (128±9) U/g, (0.026 8±0.004 3) vs (0.013 4±0.003 1) U/g, all P<0.05]. Conclusions: The timing of the intervention is related to the antioxidant effect of insulin glargine during delayed burn resuscitation. The intervention immediately and 2 hours after burn could have a better antioxidant effect compared to the intervention at 6 hours after burn.

[Assessment of heart's changes of elite Chinese male weightlifter by speckle tracking echocardiography]

OBJECTIVE

To evaluate the changes of heart structure and function in elite Chinese weightlifters by spot tracking technique.

METHODS

Chinese elite male weightlifters (weightlifter group, n=16) and age-matched healthy men (control group, n=16) were included as subjects. Transthoracic echocardiography and speckle-tracking automatic functional imaging were used for two-dimensional myocardial strain measurements.

RESULTS

The thickness of septum and left ventricular (LV) posterior wall and the myocardial mass index of LV were all higher than those of the control group [(9.3±1.3) mm vs. (8.0±0.4) mm, (9.2±0.8) mm vs. (8.0±0.8) mm, (77.8±12.8) g/m² vs. (67.8±11.2) g/m², all P < 0.05]. Although the LV ejection fraction (LVEF) and global long axis strain value (LVGLS) were not significantly different from those in the control group, the LV mean Sm and Em reflecting the systolic and diastolic functions of the LV were lower than those in the control group (P < 0.05). Further myocardial strain analysis showed that the absolute value of the long axial strain of the basal anteroseptal and mid-inferoseptal segments of the weightlifters were significantly lower than those of the control group [|(-15.1±4.2)%|vs.|(-18.7±3.0)%|, |(-18.8±2.6)%|vs.|(-21.3±2.8)%|, all P < 0.05]. There was no significant difference in other segments. The athletes were divided into two groups according to their best performance in the National Youth Games. The athletes were divided into two sub-groups according to their performance in the National Youth Games. The thickness of the septum in the sub-group with better performance (who ranked the 1^st to 8^th) was larger [(10.2±1.1) mm vs. (8.5±1.0) mm, P < 0.05], and the absolute value of the long-axis strain in the mid-inferoseptal segment was lower [|(-17.1±2.1)%|vs.|(-20.4±2.1)%|, P < 0.05].

CONCLUSION

The thickening of septum is more obvious in the excellent weightlifters, accompanied by the decrease of myocardial systolic function. The speckle-tracking technique of echocardiography can identify the changes of the heart structure and function of elite athletes at an early stage, which may provide a basis for sports medicine supervision and the selection of excellent talents.

[LncRNA HULC promots HCC growth by downregulating miR-29]

Objective: To explore the effects of lncRNA HULC on hepatocellular carcinoma (HCC) growth by down-regulating miR-29. Methods: The expression levels of HULC and miR-29 in HCC tissues and cells were detected by real-time quantitative PCR (RT-qPCR), and the correlation analysis was performed. After HCC cells were transfected with HULC overexpressed plasmid or siRNA, the expressions of miR-29 and its target gene SETDB1 were determinate by RT-qPCR. According to the bioinformatic prediction of the miR-29 binding site in the HULC sequence, the report gene plasmids were constructed. The HCC cells were co-transfected with miR-29 mimics or miR-29 inhibitor, and the HULC targeted regulation of miR-29 was verified by dual luciferase reporter assay. The effect of miR-29 on the HULC-mediated proliferation in HCC cells was detected by cell count kit 8 (CCK-8) experiment. Expression of tumor proliferation antigen Ki-67 was detected by RT-qPCR.The Hep3B cells were inoculated in mice and miR-29 mimics and miR-29 negative control (NC) further injected into the lesions. The tumor volume was observed, and the expressions of tumor proliferation antigen ki-67 in tumor tissues were detected by immunohistochemical staining. Results: The expression of HULC was significantly up-regulated while the expression of miR-29 was significantly down-regulated in HCC tissues and cells (P<0.01). The level of HULC was negatively correlated with miR-29 in tumor tissues (r=-0.754, P<0.01) and HCC cells (r=-0.865, P<0.05). The in vitro experiments showed that, compared with the blank control group, the expression of miR-29 in HULC overexpressed Huh7 cells was significantly reduced, while the mRNA level of miR-29 target gene SETDB1 was increased (P<0.01). The expression of miR-29 was significantly increased in HULC deleted Hep3B cells, while the mRNA expression of SETDB1 was decreased (P<0.01). Double luciferase reporter gene assay showed that miR-29 mimics significantly inhibited the luciferase activity of Hep3B cells transfected with HULC wide type (psi-HULC-WT) plasmid but had no effect on Hep3B cells transfected with mutant plasmid (psi-HULC-Mut). However, the miR-29 inhibitor antagonized the inhibitory effect of miR-29 mimics on luciferase activity of psi-HULC-WT (P<0.01). Cell proliferation experiments showed that, compared with the control group, the proliferation ability of miR-29 mimics overexpressed Huh7 cells was significantly reduced.After 24, 48 and 72 hours of treatment, the proliferation rates of Huh7 cells in the HULC overexpressed group were (43.87±3.82)%, (83.45±7.46)% and (123.34±8.67)%, respectively, significantly higher than (13.45±1.77)%, (23.54±1.37)% and (38.21±2.09)% of control group (P<0.05). After treatment for 48 and 72 hours, the proliferation rates of miR-29 mimics transfected Huh7 cells were (57.10±1.94)% and (73.76±3.46)%, respectively, significantly lower than (83.45±7.46)% and (123.34±8.67)% of control group (P<0.05). After treatment for 48 and 72 hours, the proliferation rates of Huh7 cells transfected with miR-29 mimics and miR-29 inhibitor group were (76.45±3.24)% and (89.37±4.37)%, respectively, significant higher than (57.10%±1.94)% and (73.76±3.46)% of the control group (P<0.05). After 48 h transfection, the expression of Ki-67 in Huh7 transfected with miR-29 mimics was significantly inhibited compared with the control group (P<0.01). However, the expression of Ki-67 mRNA was increased in Huh7 cells transfected with miR-29 inhibitor (P<0.01). The results of in vivo experiments showed that the tumor volumes of the control group, miR-29 mimics group and miR-29 mimics + miR-29 inhibitors group were (504.0±19.6) mm(3), (310.0±24.3) mm(3) and (483.7±21.2) mm(3), respectively. Injection of miR-29 mimics reduced while miR-29 inhibitor promoted tumorigenesis ability of Huh7 in nude mice (P<0.01). The immunohistochemical staining showed that the average optical density values of Ki-67 protein in tumor tissues of the control group, miR-29 mimics group and miR-29 analogue+ miR-29 inhibitor group were 0.65±0.08, 0.36±0.07 and 0.56±0.06, respectively. The expression level of Ki-67 protein in miR-29 mimics group was significantly reduced (P<0.01) while increased in the miR-29 mimics+ miR-29 inhibitor group (P<0.01). Conclusion: LncRNA HULC promotes HCC growth by down-regulating miR-29.

[Analysis of chyle leakage after central lymph node dissection for thyroid carcinoma]

Objective: To analyze the clinical characteristics, treatment and prognosis of chyle leakage after central lymph node dissection for thyroid cancer. Methods: A retrospective analysis was made of 985 patients who underwent surgical for thyroid carcinoma plus central lymph node dissection from January 2017 to June 2018 in Renji Hospital Affiliated to Medical College of Shanghai Jiaotong University. Patients were divided into those without (group A, n=973) and with (group B, n=12) chyle leakage. Patients with chyle leakage who underwent left central lymph node dissection were divided into group B1 (n=5) and right central lymph node dissection into group B2 (n=7). Patients with chyle leakage were treated with fat-free diet and negative pressure drainage. SPSS 20.0 software was used to analyze the general condition, surgical pathology, postoperative drainage, hospitalization days, treatment and prognosis of patients in B1 and B2 groups. Results: The incidence of chyle leakage after central lymph node dissection for thyroid cancer was 1.2% (12/985). There were no significant differences in age, sex, size of primary lesion, number of lymph node dissection in central area and number of lymph node metastasis in central area between group A and group B (all P>0.05). The drainage volume on the first day after operation [((51.7±26.7)) ml] and the average hospitalization days [(3.4±0.8) d] in group A were significantly lower than those in group B ([131.3±56.0)]ml, [10.4±2.6)]d). The differences were statistically significant (t value was -5.442, -11.238, respectively, both P<0.001). There were no significant differences in age, size of primary lesion, number of lymph node dissection, number of lymph node metastasis, drainage volume on the first day after operation and average hospitalization days between group B1 and group B2 (all P>0.05). All chyle leakages in group B stopped after conservative management without surgical intervention. Conclusion: The occurrence of chyle leakage after central lymph node dissection is a rare complication. It can be cured by conservative treatment such as diet control, pressure bandaging and negative pressure drainage, and generally does not require secondary surgery.

[Research for intraoperative localization of parathyroid gland usingnanocarbon imaging combined with 99m Tc-MIBI]

Objective:To explore the clinical application of nanocarbon(NC) suspension liquid combined with low dose of 99m Tc-MIBI for parathyroid localization in the hyperparathyroidism surgery.Method:Forty-four patients with secondary hyperparathyroidism(SHPT) in the department of head-neck surgery of Renji Hospital, affiliated to Shanghai Jiaotong University, School of Medicine, were enrolled and randomized into 3 groups including low-dose 99m Tc-MIBI+NC groupⅠ, high dose99m Tc-MIBI+NC group Ⅱ,and control group Ⅲ.We compared the level of PTH,serum calcium before and after operation,and the intraoperative amount of radioactive isotopes of parathyroid gland, etc.Use t-test and Anova for statistical processing. Result:After operation,the PTH levels in group Ⅰ,Ⅱ,Ⅲ were(23.8±32.4)ng/L,(15.8±18.2)ng/L,(90.1±139.4)ng/L,respectively(groupⅠvs Ⅲ,P<0.05;groupⅡvs Ⅲ,P<0.05,groupⅠvsⅡ,P>0.05).The intraoperative amount of radioactive isotopes of parathyroid gland had no significant difference among group Ⅰ,group Ⅱ and group Ⅲ. Conclusion:Nanocarbon combined with 99m Tc-MIBI for SHPT surgery has important localization value.And low dose of 99m Tc MIBI can reduce the cost and radiation, which can achieve the same outcome for patients..

[A case report of cerebral resuscitation by surface cooling in a patient with cardiac arrest]

Therapeutic hypothermia is an important treatment for cerebral resuscitation in patients after cardiac arrest. But it is rarely used for comatose survivor post-cardiac arrest in China. The patient was the first case who was in coma post cardiac arrest caused by acute myocardial infarction and given hypothermia therapy in our hospital. After coronary reperfusion and therapeutic hypothermia, the patient's sneurologic function was recovered to normal. The paper discussed the indications, contraindications, cooling methods and complications of therapeutic hypothermia.

[Long-term effect of different right ventricular apex pacing ratio on heart structure and function of patients with dual chamber pacemaker]

OBJECTIVE

To evaluate Long-term effect of different right ventricular apex pacing ratio for heart structure and function of patients with dual chamber pacemakers.

METHODS

Patients who were implanted with dual chamber pacemakers at Department of Cardiology, Peking University Third Hospital were collected. The electrodes were put in right ventricular apex. All the patients, last pacemaker programming control and echocardiography results were followed up and collected.Patients with 10%-40% pacing ratio were rejected.

RESULTS

The total of 83 patients were enrolled in this study. The mean duration of the follow-up was (38±23) months. The morbility rates of moderate-severe mitral regurgitation (MR) and tricuspid regurgitation (TR) all significantly increased after implantation compared with those before implantation (6.2% vs. 2.6%, 11.1% vs. 4.9%, all P<0.01). There were 9 patients with moderate-severe TR after pacemaker implantation. They had higher pulmonary artery systolic pressure (PASP) and mitral diastolic early flow peak velocity/lateral mitral annulus diastolic early velocity (E/Em) [(49.6±10.5) mmHg vs. (33.8±12.0) mmHg, P<0.01, 1 mmHg=0.133 kPa; and 11±5 vs.9±3, P<0.05]. And 52 patients had less than 10% pacing ratio (group A) and 31 patients had more than 40% pacing ratio (group B). The right atrium area and right ventricular diastolic diameter were bigger after implantation than those before implantation in group B [(17.7±4.0) cm(2) vs. (15.6±3.2) cm(2), (21.5±4.4) mm vs. (19.9±3.4) mm, all P<0.05]. The morbility of pulmonary artery systolic pressure (PASP) ≥50 mmHg was higher after implantation than that before implantation in group B (9.7% vs. 3.2%, P<0.05). The left atrium area and right atrium area were bigger in group B than those in group A [(21.8±5.5) cm(2) vs. (20.2±4.6) cm(2), (17.7±4.0) cm(2) vs. (16.1±3.8) cm(2), all the P<0.05] after implantation, and lower left ventricular ejection fraction (LVEF) in group B than that in group A (68%±6% vs. 70%±6%, P<0.05).

CONCLUSION

Patients with higher right ventricular apex pacing ratio have bigger left atrium, right atrium and right ventricular, higher PASP and lower LVEF in the long term.

Studies on the Odd-Even Effect of Methylene Spacers in Bismaleimides

The synthesis of a series of bismaleimides based on diamines containing flexible units of variable length is presented. These structures were characterized by FTIR and NMR. The changes in spectra are dominated by the CH2 stretching and deformation vibrational bands. The wavenumber of methylene provides a sensitive measure for the chain packing geometry. An attempt has been made to explain the odd-even effects at the molecular level on the basis of the article results. DSC was used to monitor the thermal properties of the samples. The melting points of the bismaleamic acids and bismaleimides are affected by odd-even effect. The reactivity of maleimide group was analyzed. Positions of signals in FTIR and NMR spectra show that BMI should be more stable as the chain length increase.

Synthesis and Characterization of the Bismaleimides Containing Aliphatic-ether Chain for Microelectronics Application

This project aims to develop and characterize a series of bismaleimide (BMI) polymers based on maleic anhydride and aliphatic-ether diamines. The effects of varying the chain length of aliphatic-ether diamines on the resultant bismaleimide systems were evaluated so that their suitability for microelectronics applications could be evaluated. The synthetic reaction and properties of the bismaleimide materials were investigated using Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Thermo- Gravimetric Analysis (TGA), Dielectric Thermal Analysis (DEA) and rheometry. Results showed that thermal, dielectric and rheological properties were all affected by the main chain length of BMI. The magnitude of the dielectric constant at 100 kHz increases with the increasing chain length. The curing peak temperature, curing heat and degradation temperature of BMI, all decrease with the increasing chain length.

Supersymmetry and the anomalous anomalous magnetic moment of the muon

The recently reported measurement of the muon's anomalous magnetic moment differs from the standard model prediction by 2.6 sigma. We examine the implications of this discrepancy for supersymmetry. Deviations of the reported magnitude are generic in supersymmetric theories. Based on the new result, we derive model-independent upper bounds on the masses of observable supersymmetric particles. We also examine several model frameworks. The sign of the reported deviation is as predicted in many simple models, but disfavors anomaly-mediated supersymmetry breaking.

Effects of ambasilide, quinidine, flecainide and verapamil on ultra-rapid delayed rectifier potassium currents in canine atrial myocytes

OBJECTIVE

A dog atrial ultra-rapid delayed rectifier current (I(Kur. d)) is involved in canine atrial repolarization and shares similarities with the human atrial ultra-rapid delayed rectifier (I(Kur)). Almost no information is available about the actions of antiarrhythmic drugs on I(Kur.d). This study evaluated effects of ambasilide, quinidine, flecainide and verapamil on I(Kur.d) in isolated canine atrial myocytes.

METHODS

Standard whole-cell patch clamp techniques were used to study the effects of multiple concentrations of each drug.

RESULTS

All drugs produced reversible concentration-, voltage- and time-dependent I(Kur.d) inhibition. Significant effects of quinidine, flecainide and ambasilide were noted at atrial-effective antiarrhythmic concentrations in the dog. Upon the onset of a depolarizing pulse, block developed exponentially in relation to time, with the blocking rate-constant increasing with drug concentration, consistent with open-channel blockade and permitting the calculation of forward and reverse rate-constants. For all drugs, the 50% blocking concentration (EC(50)) showed significant voltage-dependence, decreasing at more positive potentials. The magnitude of voltage-dependent block was directly related to the degree of drug-induced shift in the voltage dependence of activation (r=0.97), pointing to open-channel block as a mechanism for voltage-dependent action. An additional component of voltage-dependence suggested that blocking sites were subjected to 17-21% of the transmembrane voltage field.

CONCLUSIONS

Ambasilide, quinidine, flecainide and verapamil inhibit I(Kur.d), with preferential action on the open state. I(Kur.d) inhibition may play a role in antiarrhythmic effects in canine atrial arrhythmia models. Comparisons between the effects of these drugs on I(Kur.d) and previously studied effects on I(Kur) suggest potential opportunities for investigating the molecular structural determinants of drug-blocking action on atrial-specific ultrarapid delayed rectifiers.

Multi-TeV scalars are natural in minimal supergravity

For a top quark mass fixed to its measured value, we find natural regions of minimal supergravity parameter space where all squarks, sleptons, and heavy Higgs scalars have masses far above 1 TeV and are possibly beyond the reach of the Large Hadron Collider at CERN. This result is simply understood in terms of "focus point" renormalization group behavior and holds in any supergravity theory with a universal scalar mass that is large relative to other supersymmetry breaking parameters. We highlight the importance of the choice of fundamental parameters for this conclusion and for naturalness discussions in general.

Parallel electron energy-loss spectroscopy free from gain variation

A new method is presented for removing the effect of the gain variation of parallel detectors used for the quantitation of trace elements with electron energy loss spectroscopy (EELS). Use of the ratio of two first-difference spectra eliminates the effect of gain variation of the detector, therefore eliminating the need for gain normalization and dark current subtraction. This method is particularly suitable for revealing small signals superimposed on a large background, a typical scenario for trace element quantitation of both biological and inorganic materials. This method has been tested on a system with a cooled CCD camera as the parallel detector and illustrated by the analysis of low concentration Ca in an organic matrix. The method is expected to be generally applicable to spectral analysis affected by gain variations of parallel detectors.

Pharmacokinetic-pharmacodynamic analysis of changrolin in dogs with arrhythmia

The pharmacokinetics and pharmacodynamics of changrolin (CRL) were studied in 7 dogs with arrhythmia induced by coronary artery ligature. The ECG and the percentage of reduction ratio of ventricular premature were used to evaluate the effect of CRL, and an HPLC method was used to determine the serum drug concentration. A pharmacokinetic program was used to fit concentration-time (C-T) data and a combined pharmacokinetic-pharmacodynamic model was used to analyze effect-time (E-T) data in individual dogs. After infusion with CRL 83.33 micrograms.kg-1.min-1 for 60 min, it was found that K10, T1/2, Vd, Cl and Ce were 0.0087 min-1, 78.03 min, 40.55 ml.kg-1, 0.42 ml.kg-1.min-1, and 2.01 micrograms.ml-1, respectively.

Identification of dihydroetorphine in biological fluids by gas chromatography-mass spectrometry

A method for the monitoring of dihydroetorphine hydrochloride, a powerful anaesthetic and analgesic drug, in biological fluids was developed, involving GC-MS with multiple selected-ion monitoring. Dihydroetorphine was extracted from human blood and urine with dichloromethane and then derivatized with N-heptafluorobutyrylimidazole after having been concentrated to dryness. A dihydroetorphine monoheptafluorobutyl derivative was formed, which showed good behaviour in GC-MS with electron impact ionization. Its molecular ion, m/z 609, and its main fragments, m/z 576, 534, 522 and 508, were selected as the ions for identification owing to their relative peak intensities and characteristics. The target drug was identified based on its retention time, its selected multiple ions and their relative intensities. This method was successfully used for the detection of dihydroetorphine in blood and urine from a dihydroetorphine addict and a poisoned patient, respectively.

A phosphatase inhibitor enhances the DNase I sensitivity of active chromatin

Although it is well-known that active domains of chromatin have elevated DNase I sensitivity, it can be difficult to observe preferential sensitivity in many cell types. We show that the DNase I sensitivity of active chromatin is enhanced some 10-fold by treating nuclei with the phosphatase inhibitor p-(chloromercuri)benzenesulfonic acid (CMBS) whereas DNase I sensitivity in inactive domains is only 3-fold higher. We further show that CMBS-enhanced DNase I sensitivity is associated with at least two histone modifications. First, the negatively charged CMBS molecule becomes covalently attached to the thiol groups on histone H3. Second, histone H2A phosphorylation is significantly elevated in treated nuclei. The phosphorylation data along with other results point to the possibility that H2A phosphorylation plays a role in enhancing preferential DNase I sensitivity. Whatever the mechanism, CMBS treatment of nuclei followed by DNase I digestion provides a novel and reproducible assay for probing the chromatin structure of active domains.

Serum stimulation of the c-fos enhancer induces reversible changes in c-fos chromatin structure

Transcription of the proto-oncogene c-fos is known to be activated by growth factors in serum and subsequently repressed by the Fos protein. We show that generalized DNase I sensitivity of c-fos chromatin correlates closely with enhancer activity during induction, repression, and superinduction of the c-fos gene. Within 90 s of serum stimulation, proximal DNA sequences on both sides of the enhancer exhibit increased DNase I sensitivity. Within 5 min, elevated DNase I sensitivity spreads to chromatin at the distal 3' end of the c-fos gene. These results suggest that an open state of chromatin is propagated in both directions from the enhancer. The induced alterations in chromatin structure precede the increased transcriptional activity of the c-fos gene, suggesting that these changes in chromatin structure potentiate transcription.

Proliferative capacity of human fibroblasts when cultured in serum from young or old cows

Diploid human fibroblasts have a limited proliferative capacity when grown in vitro, leading to senescence and eventual death of the culture. Results of earlier work suggested that serum from older animals might contain higher concentrations of growth inhibitors that could accelerate the onset of cellular senescence. To reexamine this question, we cultured human MRC-5 cells in bovine fetal calf serum and in serum from cows of various ages. Surprisingly, we found that human MRC-5 cells, which are normally cultured in bovine fetal calf serum, exhibit nearly identical proliferative capacity when grown in serum from young or old cows. Our failure to detect significant differences in the proliferative capacity of MRC-5 cells cultured in serum from cows of widely different ages suggests that the balance of growth-stimulating and growth-inhibiting factors in serum does not vary significantly as a function of animal age.