Effect of capsular tension ring on the refractive outcomes of patients with extreme high axial myopia after phacoemulsification

PURPOSE

The aim of the study is to evaluate the effect of capsular tension ring (CTR) implantation following cataract surgery on the refractive outcomes of patients with extreme high axial myopia.

METHODS

Sixty eyes (with an axial length of ≥26 mm) were retrospectively reviewed and classified into two groups: CTR group (n = 30), which underwent CTR implantation following phacoemulsification, and control group (n = 30), which did not undergo CTR implantation. Intraocular lens (IOL) calculation was performed using Barrett Universal II (UII), Haigis, and SRK/T formulas. The refractive prediction error (PE) was calculated by subtracting the postoperative refraction from predicted refraction. The mean PE (MPE), mean absolute error (MAE), and percentages of eyes that had a PE of ±0.25, ±0.50, ±1.00, or ±2.00 diopters (D) were calculated and compared.

RESULTS

No significant differences were observed in PE between the two groups. The Barrett UII formula revealed a lower AE in the CTR group than in the control group (p = 0.015) and a lower AE than the other two formulas (p = 0.0000) in both groups. The Barrett UII formula achieved the highest percentage of eyes with a PE of ±0.25 D (66.67%).

CONCLUSIONS

The refractive outcomes were more accurate in eyes with CTR implantation than in those with routine phacoemulsification based on the Barrett UII formula. The Barrett UII formula was recommended as the appropriate formula when planning CTR implantation in high myopia.

[Clinical analysis of 86 cases of acute fatty liver of pregnancy]

Objective: To investigate the clinical characteristics and maternal and fetal prognosis of pregnant women with acute fatty liver of pregnancy (AFLP). Methods: The clinical data of 86 AFLP pregnant women admitted to the Third Affiliated Hospital of Guangzhou Medical University from September 2017 to August 2022 were collected, and their general data, clinical characteristics, laboratory tests and maternal and fetal outcomes were retrospectively analyzed. Results: (1) General information: the age of the 86 pregnant women with AFLP was (30.8±5.4) years, and the body mass index was (21.0±2.5) kg/m2. There were 50 primiparas (58.1%, 50/86) and 36 multiparas (41.9%, 36/86). There were 64 singleton pregnancies (74.4%, 64/86) and 22 twin pregnancies (25.6%, 22/86). (2) Clinical characteristics: the main complaints of AFLP pregnant women were gastrointestinal symptoms, including epigastric pain (68.6%, 59/86), nausea (47.7%, 41/86), anorexia (46.5%, 40/86), vomiting (39.5%, 34/86). The main non-gastrointestinal symptoms were jaundice of skin and/or scleral (54.7%, 47/86), edema (38.4%, 33/86), fatigue (19.8%, 17/86), bleeding tendency (16.3%, 14/86), polydipsia or polyuria (14.0%, 12/86), skin itching (8.1%, 7/86), and 17.4% (15/86) AFLP pregnant women had no obvious symptoms. (3) Laboratory tests: the incidence of liver and kidney dysfunction and abnormal coagulation function in AFLP pregnant women was high, and the levels of blood ammonia, lactate dehydrogenase and lactic acid were increased, and the levels of hemoglobin, platelet and albumin decreased. However, only 24 cases (27.9%, 24/86) of AFLP pregnant women showed fatty liver by imageology examination. (4) Pregnancy outcomes: ① AFLP pregnant women had a high incidence of pregnancy complications, mainly including renal insufficiency (95.3%, 82/86), preterm birth (46.5%, 40/86), hypertensive disorders in pregnancy (30.2%, 26/86), gestational diabetes mellitus (36.0%, 31/86), fetal distress (24.4%, 21/86), pulmonary infection (23.3%, 20/86), disseminated intravascular coagulation (16.3%, 14/86), multiple organ dysfunction syndrome (16.3%, 14/86), hepatic encephalopathy (9.3%, 8/86), and intrauterine fetal death (2.3%, 2/86). ② Treatment and outcome of AFLP pregnant women: the intensive care unit transfer rate of AFLP pregnant women was 66.3% (57/86). 82 cases were improved and discharged after treatment, 2 cases were transferred to other hospitals for follow-up treatment, and 2 cases (2.3%, 2/86) died. ③ Neonatal outcomes: except for 2 cases of intrauterine death, a total of 106 neonates were delivered, including 39 cases (36.8%, 39/106) of neonatal asphyxia, 63 cases (59.4%, 63/106) of neonatal intensive care unit admission, and 3 cases (2.8%, 3/106) of neonatal death. Conclusions: AFLP is a severe obstetric complication, which is harmful to mother and fetus. In the process of clinical diagnosis and treatment, attention should be paid to the clinical manifestations and laboratory tests of pregnant women, early diagnosis and active treatment, so as to improve maternal and fetal outcomes.

[Outcomes of the second pregnancy after Triple-P procedure in women complicated with placenta accreta spectrum disorders]

Objective: To investigate the safety of the Triple-P procedure in women complicated with severe placenta accreta spectrum disorders (PAS) and its influence on second pregnancy. Methods: From January 2015 to December 2017, the outcomes of the second pregnancy after the Triple-P procedure in 11 pregnant women complicated with PAS in the Third Affiliated Hospital of Guangzhou Medical University and the First Affiliated Hospital of Zhengzhou University were retrospectively analyzed. Results: By December 2021, a total of 11 pregnant women who underwent the Triple-P procedure for PAS had a second pregnancy, with a median interval of 3 years (2-3 years). Of the 11 pregnant women, 7 delivered after 36 weeks of gestation. The median gestational age was 38 weeks, and 4 terminated within the first trimester. PAS recurred in 1 of 7 pregnant women (1/7) and was associated with placenta previa. All of the 7 pregnant women were delivered by cesarean section, with a median postpartum blood loss of 300 ml (200-450 ml), and only one pregnant woman required blood transfusion. None of the pregnant women were transferred to the intensive care unit, and there were no uterine rupture, bladder injury, puerperal infection, and neonatal adverse outcomes. Conclusion: Pregnant women who underwent the Triple-P procedure for severe PAS could be considered for second pregnancy with strictly management by an experienced multidisciplinary team, which may result in a good outcome.

[Analysis of the efficacy and related influencing factors of pelvic packing in the treatment of intractable postpartum hemorrhage after emergency perinatal hysterectomy]

Objective: To investigate the effect of pelvic packing on the control of intractable postpartum hemorrhage after emergency perinatal hysterectomy (EPH). Methods: Eleven cases with complete clinical data of pelvic packing due to failure of hemostasis after EPH were collected to evaluate the outcome, complications, hospital stay of pregnant women, and to analyze the factors affecting the effect of pelvic packing. The cases included patients who were admitted to the Third Affiliated Hospital of Guangzhou Medical University after pelvic packing treatment in the other hospital due to continuous bleeding after EPH or who were referred to our hospital for pelvic packing treatment due to continuous bleeding after EPH from January 2014 to August 2021. Results: The median gestational week of 11 pregnant women was 38.3 weeks(38.0-39.9 weeks) , and the methods of termination of pregnancy were cesarean section in 7 cases (7/11) and vaginal delivery in 4 cases (4/11). The median time between postpartum hemorrhage and pelvic tamponade was 10 hours (5-57 hours), the median amount of bleeding was 8 500 ml(4 800-15 600 ml) , the median number of pelvic tamponade was 3 pieces (2-7 pieces), and the median retention time of gauze pad was 6.0 days (3.0-6.0 days). The median frequency of laparotomy in this pregnancy was 3 times (2-3 times), with a maximum of 4 among the 11 cases, the first pelvic packing was successful in hemostasis in 9 cases, and the final successful treatment in all of the 11 cases. All parturients had hemorrhagic shock (11/11) and disseminated intravascular coagulation (11/11) before pelvic packing. Other common complications were multiple organ dysfunction syndrome (9/11), cardiac arrest (4/11), deep vein thrombosis (3/11), septic shock (3/11), and intestinal obstruction (1/11). All parturients took out the gauze after the coagulation function returned to normal and there was no active bleeding. The recovery time of coagulation function in 11 cases was 3 days (3-5 days), the retention time of gauze pad was 6 days (3-6 days), the median length of stay in intensive care unit was 14 days (11-26 days), and the median total length of stay was 22 days (16-49 days). Conclusions: Pelvic packing could be used as a temporary strategy for intractable postpartum hemorrhage after EPH, which provides a key time for injury control resuscitation for patients with unstable vital signs. This technology provides an opportunity for referral to superior medical institutions and further treatment.

Maternal cardiac arrest: a retrospective analysis

OBJECTIVES

To describe the characteristics and factors which may influence the maternal outcomes of maternal cardiac arrest (MCA).

DESIGN

Retrospective analysis of cases.

SETTING

China.

POPULATION OR SAMPLE

A total of 61 MCA patients admitted or transferred to The Third Affiliated Hospital of Guangzhou Medical University from January 2000 to December 2019.

METHODS

Clinical data for MCA were analysed retrospectively. The indicators included maternal age; BMI; gestational age; antenatal examination; income; MCA cause and place; cardiopulmonary resuscitation (CPR); mode of delivery; maternal prognosis; and neonatal outcome.

MAIN OUTCOME MEASURES

The impact of case characteristics on maternal prognosis of MCA.

RESULTS

The hospital received 61 patients with MCA, 36 of whom died (mortality 59.0%, 95% CI 46.3-71.7%). MCA was predominantly caused by treatable complications. Those who died were more likely to have collapsed in the ICU.

CONCLUSIONS

Regular antenatal examination and early intervention can reduce the incidence of adverse pregnancy outcomes. The location of MCA occurred may be related to maternal prognosis. The leading causes of MCA were postpartum haemorrhage and amniotic fluid embolism.

TWEETABLE ABSTRACT

A retrospective analysis describes the correlation between case characteristics of MCA and maternal outcomes.

[Clinical investigation in the methods for complete placenta previa labor induction in the second trimester]

Objective: To investigate the appropriate method of labor induction in the second trimester for complete placenta previa patients. Methods: The labor induction outcomes of 85 cases with complete placenta previa in the second trimester were retrospectively analyzed. Twenty patients in group A were treated with cesarean section, 30 patients in group B were treated with ethacridine and mifepristone combined with uterine artery embolization (UAE), and 35 patients in group C were induced by using ethacridine and mifepristone. The clinical features and induction outcomes of three groups were compared. Results: The total duration of labor in group B [(28.7±30.1) hours] was significantly longer than that of group C [(24.3±21.9) hours; P<0.05]. The total amount of blood loss during induction and labor in group B [(302±271) ml] was significantly lower than those of group C [(393±523) ml] and group A [(626±487) ml; P<0.05]. The incidence of fever in group B (13%, 4/30) was significantly higher than those of group C (11%, 4/35) and group A (10%, 2/20; P<0.05). In group C, 13 patients (37%, 13/35) underwent emergency UAE, and 2 patients (6%, 2/35) underwent emergency cesarean section. As to average hemoglobin level and blood transfusion rate, there were no difference among the three groups (all P>0.05). Conclusion: Prophylactic UAE combined with drug induction in patients with complete placenta previa in the second trimester could significantly reduce the amount of bleeding during induction and reduce the risk of emergency procedures.

[Ratio of transfer cesarean section after trial of labor and maternal-fetal adverse outcomes based on Robson classifications]

Objective: To investigate the ratio of transfer cesarean section after trial of labor and maternal-fetal outcomes based on Robson classifications. Methods: The delivery data by cesarean section in Third Affiliated Hospital of Guangzhou Medical University from January 1st, 2009 to December 31st, 2015 (gestational age ≥28 weeks and newborn birth weight >1 000 g) were retrospectively collected. The ratio of transfer cesarean section after trial of labor and maternal-fetal adverse outcomes were analyzed by weighted adverse outcome score in different Robson classifications. Results: (1) The highest ratio of transfer cesarean section after trial of labor was classification 9 (all abnormal lies, including previous cesarean section and breech were excluded) reached 47.31% (431/911) , followed by classification 2 (nulliparous women with a single cephalic pregnancy, ≥37 weeks gestation who had labour induced) accounted for 44.90%(409/911). (2)The tops of weighted adverse outcome score of transfer cesarean section after trial of labor were classification 10 (single cephalic pregnancy at <37 weeks gestation, including women with previous cesarean delivery) 24.55, classification 5 (single cephalic pregnancy multiparous women, with at least one previous cesarean delivery, ≥37weeks gestation) 3.64. Conclusion: Carefully evaluating the delivery mode and emphasizing the intrapartum management in nulliparous women with a single cephalic pregnancy, at ≥37 weeks gestation who had labour induced and trial of labor after cesarean section is essential to reduce the risk of adverse outcomes in transfer cesarean section after trial of labor.

[Risk factors and sonographic findings associated with the type of placenta accreta spectrum disorders]

Objective: To evaluate the risk factors and sonographic findings of pregnancies complicated by placenta increta or placenta percreta. Methods: Totally, 2 219 cases were retrospectively analyzed from 20 tertiary hospitals in China from January 2011 to December 2015. The data were collected based on the original case records. All cases were divided into two groups, the placenta increta (PI) group (79.1%, 1 755/2 219) and the placenta percreta (PP) group (20.9%, 464/2 219) , according to the degree of placental implantation. The risk factors and sonographic findings of placenta increta or percreta were analyzed by uni-factor and logistic regression statistic methods. Results: The risk factors associated with the degree of placental implantation were age, gravida, previous abortion or miscarriage, previous cesarean sections, and placenta previa (all P<0.05), especially, previous cesarean sections (χ(2)=157.961) and placenta previa (χ(2)=91.759). Sonographic findings could be used to predict the degree of placental invasion especially the boundaries between placenta and uterine serosa, the boundary between placenta and myometrium, the disruption of the placental-uterine wall interface and loss of the normal retroplacental hypoechoic zone(all P<0.01). Conclusions: Previous cesarean sections and placenta previa are the main independent risk factors associated with the degree of placenta implantation. Ultrasound could be used to make a prenatal suggestive diagnosis of placenta accreta spectrum disorders.

[Analysis of 2 204 stillbirths in 11 hospitals of Guangdong province]

Objective: To analyze the incidence and causes of stillbirth in 11 hospitals of Guangdong province, and to explore the appropriate interventions. Methods: Clinical data of stillbirth in 11 hospitals of Guangdong province were collected from January 2014 to December 2016. The gestational weeks, causes, maternal conditions and other factors were analyzed. Results: (1) From 2014 to 2016, 103 472 newborns were delivered in the 11 hospitals, and the number of stillbirth was 2 204, with the incidence of 2.13%. Among them, 0.71%(738/103 472) was therapeutic induction, 1.42%(1 066/103 472) was natural stillbirth. At different gestational age (<28 weeks, 28-<37 weeks and ≥37 weeks), the incidence of stillbirth was 55.63% (1 226/2 204), 28.45% (627/2 204) and 15.92% (351/2 204), respectively, with statistically significant difference (P<0.01). (2) For stillbirth<28 weeks, the first reason was therapeutic induction, accounting for 53.34% (654/1 226). For stillbirth during 28-37 weeks, pre-eclampsia was the major cause, accounting for 40.67% (255/627). And for full-term stillbirth, the causes were umbilical cord factors (19.37%, 68/351), abnormal labor (17.09%, 60/351). (3) In all the stillbirth cases, the incidence of fetal growth restriction (FGR) <28 weeks was significantly higher than that during 28-37 weeks [23.49% (288/1 226) vs 18.02% (113/627) , P<0.01]. (4) The stillbirth rate during labor was significantly higher in women ≥35 years old than in younger women [63.88% (191/299) vs 36.12% (108/299) ; χ(2)=9.346, P=0.000]. For the causes of stillbirth during labor, the incidence of severe maternal obstetrical complications [61.11% (33/54) vs 38.89% (21/54) ; χ(2)=3.323, P=0.002], abnormal labor [65.82% (52/79) vs 34.18% (27/79) ; χ(2)=4.067, P=0.001] and abnormal fetal position [66.63% (26/39) vs 33.37% (13/39) ; χ(2)=3.002, P=0.013] were higher in women ≥35 years old than in younger women. (5) Cesarean section during labor accounted for 33.77% (101/299) of stillbirth, including 76 cases of emergency cesarean section or converted to cesarean section during labor. Conclusions: (1) The incidence of stillbirth in the 11 hospitals is high, and the causes are different at different gestational ages, therefore, different interventions are needed to reduce the incidence in different gestational weeks. Supervision of therapeutic induction should be strengthened <28 gestational weeks; standard management of pregnancy might decrease the occurrence of natural death ≥28 weeks. (2) Attention should be paid to fetal body weight during pregnancy, especially FGR. (3) The stillbirth rate is high in elderly pregnant women, so it is important to strengthen the management of the elderly pregnant women.

Neutrophil CD16b crosslinking induces lipid raft-mediated activation of SHP-2 and affects cytokine expression and retarded neutrophil apoptosis

Two different types of FcRs for IgG are constitutively expressed on the surface of human neutrophils, namely, FcγRIIA (CD32a) and FcγRIIIB (CD16b). Unlike FcγRIIA, FcγRIIIb is GPI anchored to the cell membrane and its signal transduction is still ambiguous. To further understand the signal transduction of CD16b, we compared neutrophil cytokine expression and apoptosis by the cross-linking of CD32a and CD16b respectively. We found that both CD32a and CD16b crosslinking can activate neutrophils, but did not exactly share cytokine expression profiles. On the other hand, CD16b cross-linking retarded neutrophil apoptosis while CD32a promoted it. By interrupting the lipid raft with methyl-β-cyclodextrin (MβCD) and inhibiting the ITAM-SYK pathway with an SYK inhibitor (piceatannol), we found reduced apoptosis was at least partially mediated by lipid raft structure, but not the ITAM-SYK pathway. Additionally, CD16b but not CD32a cross-linking triggered SHP-2 phosphorylation and led to its translocation into lipid rafts. SHP-2 phosphorylation and translocation were inhibited by MβCD. Moreover, pre-inhibition of SHP-2 by a specific inhibitor (SHP099) converted IL-10 and SOCS3 expression level and promoted neutrophil apoptosis after CD16b crosslinking. In conclusion, these results, for the first time, collectively indicate that SHP-2 is activated by CD16b crosslinking in neutrophils and functions as a component of the raft-mediated signaling pathway.

Targeted sequencing of maternal plasma for haplotype-based non-invasive prenatal testing of spinal muscular atrophy

Five pregnant women with a child affected by spinal muscular atrophy (SMA) were recruited between November 2014 and March 2015. Deletion of exons 7 and/or 8 in the SMN1 gene were identified by multiplex ligation-dependent probe amplification (MLPA), the current standard diagnostic test for SMA. Parental and fetal haplotypes of the SMN1 gene were determined in each family from haplotype-based non-invasive testing of blood samples and maternal plasma, respectively. Fetal haplotype was compared with the results of MLPA of fetal DNA obtained from amniotic fluid or chorionic villi. Parental haplotypes were constructed successfully in the five families. Assisted by the information on parental haplotype, non-invasive testing of maternal plasma identified one fetus with homozygous deletion of exons 7 and 8, two fetuses with heterozygous deletion of exons 7 and 8 and two normal fetuses. These results were consistent with the diagnosis by MLPA. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

[Risk factors analysis of reversible posterior leukoencephalopathy syndrome in pre-eclampsia or eclampsia gravida]

Objective: To investigate the risk factors of reversible posterior leukoencephalopathy syndrome (RPLS) in pre-eclampsia or eclampsia gravida. Methods: This study was conducted in the Third Affiliated Hospital of Guangzhou Medical University between January 2013 and March 2016. A total of 100 patients who had no severe neurological diseases and were diagnosed pre-eclampsia or eclampsia, and underwent brain MRI were collected retrospectively. They were divided into 2 groups according to the MRI results, the RPLS group (n=49) and the non-RPLS group (n=51). The medical history, clinical symptoms and the results of laboratory examination were analyzed by the logistic regression, in order to explore the risk factors. Results: In single factor analysis, HELLP syndrome, pregnancy associated with other diseases, poor prenatal care, grade 3 hypertension, elevated systolic blood pressure or diastolic blood pressure, elevated WBC, aspartate transaminase (AST), alanine aminotransferase (ALT), uric acid (UA) and lactate dehydrogenase (LDH), decreased platelet (PLT), headache, visual changes, seizures and conscious disturbance were more frequent in the RPLS group than those in the non-RPLS group (all P<0.05). According to the multivariate logistic regression analysis, the elevated WBC (OR=1.291, 95% CI: 1.058-1.575, P=0.012), UA (OR=1.008, 95% CI: 1.001-1.016, P=0.032) and headache (OR=18.260, 95% CI: 3.562-93.607, P=0.000) were the independent risk factors. Conclusions: Maternal history, clinical symptoms and some laboratory examinations might help in the early diagnosis of RPLS in pre-eclampsia or eclampsia gravida. Headache, the elevation of WBC and UA were the most significant factors.

[Noninvasive diagnostic and predictive value in renal transplant recipients with acute rejection by measurement of urine Fractalkine]

Objective: To investigate the relationship between early-stage renal acute rejection(AR) and the level of Fractalkine in urine, explore the diagnostic and noninvasive monitoring value in early stage after transplantation by measurement of urine Fractalkine. Methods: Urine samples were examined from renal transplant patients between January 2006 and October 2009. A total of 155 patients were enrolled, including 49 with biopsy-proved AR, 58 patients with stable renal function and no abnormal histological findings, 10 patients with subclinical rejection in protocol biopsy, 9 patients with biopsy-proven acute tubular necrosis and 29 patients with biopsy-proven chronic allograft nephropathy. Additionally, urine samples were also collected from 40 healthy controls. Fractalkine was measured in urine samples using a commercial human Fractalkine enzyme-linked immunosorbent assay (ELISA) kit. Immunohistochemistry for Fractalkine expression was performed on biopsies from renal transplant patients with AR and non-AR. Results: Forty-nine patients with AR excreted urinary Fractalkine at a significantly higher level than levels in patients with stable renal function and healthy controls[(429.1±56.1)vs (94.6±8.4), (84.5±8.9)ng/mmol creatine, both P<0.001]. Patients with AR excreted urinary Fractalkine at a significantly higher level than levels in patients with acute tubular necrosis and chronic allograft nephropathy[(429.1±56.1)vs(133.0±9.8), (183.0±18.9)ng/mmol creatine, both P<0.001]. Receiver operating characteristic(ROC)curve was constructed to determine the discriminatory power of Fractalkine levels for diagnosis of AR. The area under ROC curve was 0.920(95% CI: 0.875-0.969, P<0.001), which showed that Fractalkine was a suitable marker for the diagnosis of AR. At a cut-off point of 157.5 ng/mmol creatinine, the sensitivity was 83.7% and the specificity was 84.5% (P<0.001). The dynamic level of urinary Fractalkine in AR patients within 3 weeks after transplantation fluctuated above 300 ng/mmol creatine, which is remarkably higher than patients with stable renal function (below 200 ng/mmol creatinine). Conclusions: As a noninvasive monitoring method, Fractalkine in urine may be a new approach for detection of AR as well as useful to predict response to antirejection therapy. It has good sensitivity and specificity. Besides, measurement of Fractalkine in urine is a simple, inexpensive method for the routine clinical monitoring after kidney transplantation.

[Multi-centric clinical study of trial of labor after cesarean section]

OBJECTIVE

To study the feasibility and safety of trial of labor after cesarean section (TOLAC).

METHODS

Retrospective analysis of five medical center of Guangdong province from January 2011 to December 2015 hospitalized delivery information, compare the same scar TOLAC (research group) with the scar pregnancy (control group) pregnancy outcomes, to study the feasibility and safety of TOLAC.

RESULTS

(1) During 2011-2015, total delivery 95 600 cases in five medical center, 13 824 cases of thme with uterine scar pregnancy, including 12 027 cases elective repeat cesarean section and 1 797 cases (13.00%, 1 797/13 824) with scar uterus vaginal trial of labor. Among 1 308 cases of vaginal delivery, the success for trial of labor rate was 72.79% (1 308/1 797). From 2011 to 2015, there were increased rate of pregnancy after cesarean section, which were respectively 10.71%, 13.28%, 14.45%, 15.54% and 16.98%. The will of vaginal birth were rising and the rate were respectively 11.85%, 12.25%, 13.49%, 13.82% and 12.93%. (2) There were 489 (27.21%, 489/1 797) cases of scar uterus maternal emergency cesarean section in the trial of labor, reason for "social factors" require for cesarean delivery have 68 cases, the percentage was 13.91% (68/489), compared with control group (7.18%, 206/2 869), the difference was statistically significant difference (χ(2)=27.356, P=0.000). Doctors diagnosed as "aura uterine rupture" in the labor was 11.86% (58/489), compared with that in control group (1.43%, 41/2 869), the differences were statistically significant difference (χ(2)=1 578.223, P=0.000). (3) The incidence of uterine rupture of the research group (0.74%, 9/1 211) was significantly higher than that of control group (0.01%,2/31 200; χ(2)> 2 000, P=0.000). The incidence of postpartum hemorrhage in research group was 6.94% (84/1 211), compared with that in the control group (3.05%, 951/31 200), there was statistically significant difference (χ(2)=16.328, P=0.000). While, there were no statistical significancefor the labor time limit, birth rate of severe asphyxia and neonatal birth weight average differences between two groups (P>0.05).

CONCLUSIONS

The rate of pregnancy after cesarean section is increasing year by year, and the will of vaginal birth is increasing, while it still are generally low. TOLAC is safe and feasible, but also significantly higher risk, strictly labor monitoring and can proceed fast cesarean delivery in delivery room is an important guarantee of safe delivery.

[Effects of extracellular regulated protein kinases protein and impairment of blood testis barriar stucturein of mice with exposure to decabromodiphenyl ether]

Objective: To study changes in expression of claudin-11 and proteins related to mitogen-activated protein kinase (MAPK) signaling pathways, as well as the ultrastructure of the blood testis barrier (BTB), in male ICR mice exposed to decabromodiphenyl ether (BDE-209). Methods: Fifty-two mice, 4 weeks of age, weighing 15-21 g, were provided with adaptive feeding for 1 week. Mice were randomly divided into 4 groups, named control, low-dose, medium-dose and high-dose groups. The treated groups received BDE-209, by intragastric gavage, at doses, respectively, of 100, 300 and 500 mg/kg. Mice were sacrificed after 6 weeks and organs harvested on ice, weighed and stored at -80 °C. The ultrastructure of testicular tissues was examined by electron microscopy. Western blotting was used to detect proteins related to the MAPK pathway, including p38 mitogen activated protein kinase (p38), phosphorylated p38 (p-p38), extracellular regulated protein kinase 1/2 (ERK1/2) , phosphorylated ERK1/2 (p-ERK1/2) , c-jun N-terminal kinase (JNK), phosphorylated JNK (p-JNK) and the BTB tight junction protein claudin-11. Analyze the difference between each groups. Results: At sacrifice, the body weights in each treated group were compared with those in the control group weighing (41.14 ± 0.60) g. Compared with controls, body weights were significantly different (P<0.05) in the middle dose, at (39.97 ± 0.66) g and high dose, at (39.98± 0.55) g in control group. The coefficients of the testis were significantly lower (P<0.05) in each treated group than in controls, with values of (0.37±0.0)%, (0.31±0.05)% and (0.31±0.04)% for low-dose, medium-dose and high-dose groups, respectively. The epidymus coefficient values were also significantly lower than controls (P<0.05), with values of (0.16±0.06)%, (0.11±0.05)% and (0.07±0.03)%, respectively in the same three dose groups. Electron microscopy ultrastructure showed that, compared with the control group, the testes in the middle and high dose groups had closely connected fractures, cell edema and more vacuoles. Compared with in the control group, levels of p-p38 and p-JNK in testicular tissue were significantly increased (P<0.05). In the control group and in low-, medium- and high-dose groups, the p-p38/p38 ratios were 1.35±0.13, 3.46±0.10, 5.71±0.26 and 4.79±0.21, respectively. The corresponding p-JNK/JNK ratios were 2.07±0.0, 4.77±0.18, 3.63±0.06 and 4.85±0.15. Claudin-11 levels were significantly lower (P<0.05) than control values in each dosed group. The corresponding values in control, low-dose, medium-dose and high-dose groups were 8.33±0.36, 2.06±0.27, 3.37±0.27 and 1.55±0.19, respectively. Conclusion: BDE-209 increased expression of proteins in the MAPK pathway and decreased expression of the BTB tight junction protein claudin-11 in testicular tissue. It also caused ultrastructural damage to the Sertoli cell BTB tight junctions. This suggested that BDE-209 might damage Sertoli cells BTB through effects on the MAPK pathway.

Lack of association between Human Oxoguanine Glycosylase 1 (hOGG1) S326C polymorphism and the risk of gastric cancer: a meta-analysis

Results from published studies on the association of Human Oxoguanine Glycosylase 1 (hOGG1) S326C genetic polymorphism with the risk of gastric cancer are inconsistent. We performed a meta-analysis to summarize the possible association. Eleven case-control studies including 2168 cases and 4058 controls were identified from electronic databases (Pubmed, Elsevier Science Direct, Chinese National Knowledge Infrastructure (CNKI), Chinese Biomedical Literature Database (CBM), and the Chinese database, Wanfang). No significant association between hOGG1 S326C genetic polymorphism and risk of gastric cancer was observed in the overall analysis. In the stratified analysis based on ethnicity, still no significant association was observed in Europeans, Asians, or Brazilians. This meta-analysis provided evidence that hOGG1 S326C genetic polymorphism was not associated with increased risk of gastric cancer. However, additional studies with large sample size and better study designs are warranted to verify our finding.

Indium-rich InGaN epitaxial layers grown pseudomorphically on a nano-sculpted InGaN template

Indium-rich InGaN epitaxial layers with a p-i-n structure were grown pseudomorphically on a strain-relaxed InGaN template to reduce structural strain induced by lattice mismatch. We applied a nano-sculpting process to improve the crystal quality of the strain-relaxed InGaN template. The results show that the nano-sculpting process can suppress effectively the threading dislocation generation and improves significantly the I-V characteristic of the InGaN p-i-n structure. This InGaN template technique with nano-sculpting process shows great potential for future applications in indium-rich InGaN optic-electron devices.

Role of SUMO:SIM-mediated protein-protein interaction in non-homologous end joining

Although post-translational modifications by the small ubiquitin-like modifiers (SUMO) are known to be important in DNA damage response, it is unclear whether they have a role in double-strand break (DSB) repair by non-homologous end joining (NHEJ). Here, we analyzed various DSB repair pathways upon inhibition of SUMO-mediated protein-protein interactions using peptides that contain the SUMO-interaction motif (SIM) and discriminate between mono- and SUMO-chain modifications. The SIM peptides specifically inhibit NHEJ as shown by in vivo repair assays and radio-sensitivity of cell lines deficient in different DSB repair pathways. Furthermore, mono-SUMO, instead of SUMO-chain, modifications appear to be involved in NHEJ. Immunoprecipitation experiments also showed that the SIM peptide interacted with SUMOylated Ku70 after radiation. This study is the first to show an important role for SUMO:SIM-mediated protein-protein interactions in NHEJ, and provides a mechanistic basis for the role of SIM peptide in sensitizing genotoxic stress of cancer cells.

Biological dose estimation of UVA laser microirradiation utilizing charged particle-induced protein foci

The induction of localized DNA damage within a discrete nuclear volume is an important tool in DNA repair studies. Both charged particle irradiation and laser microirradiation (LMI) systems allow for such a localized damage induction, but the results obtained are difficult to compare, as the delivered laser dose cannot be measured directly. Therefore, we revisited the idea of a biological dosimetry based on the microscopic evaluation of irradiation-induced Replication Protein A (RPA) foci numbers. Considering that local dose deposition is characteristic for both LMI and charged particles, we took advantage of the defined dosimetry of particle irradiation to estimate the locally applied laser dose equivalent. Within the irradiated nuclear sub-volumes, the doses were in the range of several hundreds of Gray. However, local dose estimation is limited by the saturation of the RPA foci numbers with increasing particle doses. Even high-resolution 4Pi microscopy did not abrogate saturation as it was not able to resolve single lesions within individual RPA foci. Nevertheless, 4Pi microscopy revealed multiple and distinct 53BP1- and gamma H2AX-stained substructures within the lesion flanking chromatin domains. Monitoring the local recruitment of the telomere repeat-binding factors TRF1 and TRF2 showed that both proteins accumulated at damage sites after UVA-LMI but not after densely ionizing charged particle irradiation. Hence, our results indicate that the local dose delivered by UVA-LMI is extremely high and cannot be accurately translated into an equivalent ionizing radiation dose, despite the sophisticated techniques used in this study.

Two new triterpenoid saponins from the root of Ilex pubescens

Two new triterpenoid saponins, named ilexsaponins B(4) (1) and C (2), have been isolated from the roots of Ilex pubescens. Their structures have been established as ilexgenin B 3-O-alpha-L-arabinopyranosyl-(2-->1)-beta-D-glucopyranosyl-(2-->1)-beta-D-xylopyranoside (1) and 3-O-beta-D-xylopyranosyl spathodic acid 28-beta-D-glucopyranosyl ester (2) by means of spectral and chemical methods.

Role of homologous recombination in the alpha-particle-induced bystander effect for sister chromatid exchanges and chromosomal aberrations

The bystander effect for sister chromatid exchanges (SCEs) and chromosomal aberrations was examined in hamster cell lines deficient in either DNA-PKcs (V3 cells, deficient in nonhomologous end joining, NHEJ) or RAD51C (irs3 cells, deficient in homologous recombination, HR). Cells synchronized in G0/G1 phase were irradiated with very low fluences of alpha particles such that < 1% of the nuclei were traversed by an alpha particle. Wild-type cells showed a prominent bystander response for SCE induction; an even greater effect was observed in V3 cells. On the other hand, no significant induction of SCE was observed in the irs3 RAD51C-deficient bystander cells irradiated at various stages in the cell cycle. Whereas a marked bystander effect for chromosomal aberrations occurred in V3 cells, the induction of chromosomal aberrations in irs3 bystander cells was minimal and similar to that of wild-type cells. Based on these findings, we hypothesize that HR is essential for the induction of SCE in bystander cells; however, HR is unable to repair the DNA damage induced in NHEJ-deficient bystander cells that leads to either SCE or chromosomal aberrations.

DNA-PKcs is critical for telomere capping

The DNA-dependent protein kinase catalytic subunit (DNA-PKcs) is critical for DNA repair via the nonhomologous end joining pathway. Previously, it was reported that bone marrow cells and spontaneously transformed fibroblasts from SCID (severe combined immunodeficiency) mice have defects in telomere maintenance. The genetically defective SCID mouse arose spontaneously from its parental strain CB17. One known genomic alteration in SCID mice is a truncation of the extreme carboxyl terminus of DNA-PKcs, but other as yet unidentified alterations may also exist. We have used a defined system, the DNA-PKcs knockout mouse, to investigate specifically the role DNA-PKcs specifically plays in telomere maintenance. We report that primary mouse embryonic fibroblasts (MEFs) and primary cultured kidney cells from 6-8 month-old DNA-PKcs-deficient mice accumulate a large number of telomere fusions, yet still retain wild-type telomere length. Thus, the phenotype of this defect separates the two-telomere related phenotypes, capping, and length maintenance. DNA-PKcs-deficient MEFs also exhibit elevated levels of chromosome fragments and breaks, which correlate with increased telomere fusions. Based on the high levels of telomere fusions observed in DNA-PKcs deficient cells, we conclude that DNA-PKcs plays an important capping role at the mammalian telomere.

Differential gene expression in a DNA double-strand-break repair mutant XRS-5 defective in Ku80: analysis by cDNA microarray

The ability of cells to rejoin DNA double-strand breaks (DSBs) usually correlates with their radiosensitivity. This correlation has been demonstrated in radiosensitive cells, including the Chinese hamster ovary mutant XRS-5. XRS-5 is defective in a DNA end-binding protein, Ku80, which is a component of a DNA-dependent protein kinase complex used for joining strand breaks. However, Ku80-deficient cells are known to be retarded in cell proliferation and growth as well as other yet to be identified defects. Using custom-made 600-gene cDNA microarray filters, we found differential gene expressions between the wild-type and XRS-5 cells. Defective Ku80 apparently affects the expression of several repair genes, including topoisomerase-I and -IIA, ERCC5, MLH1, and ATM. In contrast, other DNA repair-associated genes, such as GADD45A, EGR1 MDM2 and p53, were not affected. In addition, for large numbers of growth-associated genes, such as cyclins and clks, the growth factors and cytokines were also affected. Down-regulated expression was also found in several categories of seemingly unrelated genes, including apoptosis, angiogenesis, kinase and signaling, phosphatase, stress protein, proto-oncogenes and tumor suppressors, transcription and translation factors. A RT-PCR analysis confirmed that the XRS-5 cells used were defective in Ku80 expression. The diversified groups of genes being affected could mean that Ku80, a multi-functional DNA-binding protein, not only affects DNA repair, but is also involved in transcription regulation. Our data, taken together, indicate that there are specific genes being modulated in Ku80- deficient cells, and that some of the DNA repair pathways and other biological functions are apparently linked, suggesting that a defect in one gene could have global effects on many other processes.

ATM phosphorylates histone H2AX in response to DNA double-strand breaks

A very early step in the response of mammalian cells to DNA double-strand breaks is the phosphorylation of histone H2AX at serine 139 at the sites of DNA damage. Although the phosphatidylinositol 3-kinases, DNA-PK (DNA-dependent protein kinase), ATM (ataxia telangiectasia mutated), and ATR (ATM and Rad3-related), have all been implicated in H2AX phosphorylation, the specific kinase involved has not yet been identified. To definitively identify the specific kinase(s) that phosphorylates H2AX in vivo, we have utilized DNA-PKcs-/- and Atm-/- cell lines and mouse embryonic fibroblasts. We find that H2AX phosphorylation and nuclear focus formation are normal in DNA-PKcs-/- cells and severely compromised in Atm-/- cells. We also find that ATM can phosphorylate H2AX in vitro and that ectopic expression of ATM in Atm-/- fibroblasts restores H2AX phosphorylation in vivo. The minimal H2AX phosphorylation in Atm-/- fibroblasts can be abolished by low concentrations of wortmannin suggesting that DNA-PK, rather than ATR, is responsible for low levels of H2AX phosphorylation in the absence of ATM. Our results clearly establish ATM as the major kinase involved in the phosphorylation of H2AX and suggest that ATM is one of the earliest kinases to be activated in the cellular response to double-strand breaks.

The three-dimensional structure of the C-terminal DNA-binding domain of human Ku70

The proteins Ku70 (69.8 kDa) and Ku80 (82.7 kDa) form a heterodimeric complex that is an essential component of the nonhomologous end joining DNA double-strand break repair pathway in mammalian cells. Interaction of Ku with DNA is central for the functions of Ku. Ku70, which is mainly responsible for the DNA binding activity of the Ku heterodimer, contains two DNA-binding domains. We have solved the solution structure of the Ku80-independent DNA-binding domain of Ku70 encompassing residues 536-609 using nuclear magnetic resonance spectroscopy. Residues 536-560 are highly flexible and have a random structure but form specific interactions with DNA. Residues 561-609 of Ku70 form a well defined structure with 3 alpha-helices and also interact with DNA. The three-dimensional structure indicates that all conserved hydrophobic residues are in the hydrophobic core and therefore may be important for structural integrity. Most of the conserved positively charged residues are likely to be critical for DNA recognition. The C-terminal DNA-binding domain of Ku70 contains a helix-extended strand-helix motif, which occurs in other nucleic acid-binding proteins and may represent a common nucleic acid binding motif.

Werner syndrome protein is regulated and phosphorylated by DNA-dependent protein kinase

DNA double-strand breaks (DSBs) are a highly mutagenic and potentially lethal damage that occurs in all organisms. Mammalian cells repair DSBs by homologous recombination and non-homologous end joining, the latter requiring DNA-dependent protein kinase (DNA-PK). Werner syndrome is a disorder characterized by genomic instability, aging pathologies and defective WRN, a RecQ-like helicase with exonuclease activity. We show that WRN interacts directly with the catalytic subunit of DNA-PK (DNA-PK(CS)), which inhibits both the helicase and exonuclease activities of WRN. In addition we show that WRN forms a stable complex on DNA with DNA-PK(CS) and the DNA binding subunit Ku. This assembly reverses WRN enzymatic inhibition. Finally, we show that WRN is phosphorylated in vitro by DNA-PK and requires DNA-PK for phosphorylation in vivo, and that cells deficient in WRN are mildly sensitive to ionizing radiation. These data suggest that DNA-PK and WRN may function together in DNA metabolism and implicate WRN function in non-homologous end joining.

Strand-specific postreplicative processing of mammalian telomeres

Telomeres are specialized nucleoprotein structures that stabilize the ends of linear eukaryotic chromosomes. In mammalian cells, abrogation of telomeric repeat binding factor TRF2 or DNA-dependent protein kinase (DNA-PK) activity causes end-to-end chromosomal fusion, thus establishing an essential role for these proteins in telomere function. Here we show that TRF2-mediated end-capping occurs after telomere replication. The postreplicative requirement for TRF2 and DNA-PKcs, the catalytic subunit of DNA-PK, is confined to only half of the telomeres, namely, those that were produced by leading-strand DNA synthesis. These results demonstrate a crucial difference in postreplicative processing of telomeres that is linked to their mode of replication.

[Purification of vancomycin by using magnetic affinity technique]

A new kind of magnetic affinity microspheres (MAMS), whose ligand is D-Ala-D-Ala, was prepared using agarose as matrix. By using this new MAMS vancomycin was purified directly from crude fermentation liquor with only one step. The purity and the mass recovery of vancomycin measured by reverse-phase HPLC were 97% and 87%, respectively. The characteristic of this method was simpler, faster, cheaper and more effective than that of currently used ones.

A translational couch technique for total body irradiation

We have constructed a computer controlled translational couch to administer total body irradiation reproducibly and safely. The system has replaced the previous stationary anterior-posterior technique in our institution and 30 plus patients have been treated with it so far. In this technique, patients comfortably lie on a couch in supine and prone positions and are transported slowly through a narrow beam with the gantry in an upright position. Dose to the patient is determined by the couch velocity that is calculated based on physical parameters such as patient's dimensions, beam geometry, and machine dose rate. In our design, the couch velocity is continuously updated to compensate for machine dose rate fluctuations. The translational couch technique provides better dose uniformity within the patient compared to fixed beam techniques, and allows a more precise shielding block placement for organs at risk. At the same time, it presents a special challenge for dosimetry calculations. A dosimetry parameter is introduced that converts the moving beam output to the fixed beam output factor. Based on this factor, a simple dosimetry calculation method has been developed that takes advantage of conventional dosimetry parameters, eliminating extensive dosimetry measurements. Multiple point dose measurements within a phantom confirmed the validity of the calculation method.

A possible role of Ku in mediating sequential repair of closely opposed lesions

One of the hallmarks of ionizing radiation exposure is the formation of clustered damage that includes closely opposed lesions. We show that the Ku70/80 complex (Ku) has a role in the repair of closely opposed lesions in DNA. DNA containing a dihydrouracil (DHU) close to an opposing single strand break was used as a model substrate. It was found that Ku has no effect on the enzymatic activity of human endonuclease III when the substrate DNA contains only DHU. However, with DNA containing a DHU that is closely opposed to a single strand break, Ku inhibited the nicking activity of human endonuclease III as well as the amount of free double strand breaks induced by the enzyme. The inhibition on the formation of a free double strand break by Ku was found to be much greater than the inhibition of human endonuclease III-nicking activity by Ku. Furthermore, there was a concomitant increase in the formation of Ku-DNA complexes when endonuclease III was present. Similar results were also observed with Escherichia coli endonuclease III. These results suggest that Ku reduces the formation of endonuclease III-induced free double strand breaks by sequestering the double strand breaks formed as a Ku-DNA complex. In doing so, Ku helps to avoid the formation of the intermediary free double strand breaks, possibly helping to reduce the mutagenic event that might result from the misjoining of frank double strand breaks.

DNA-PKcs is required for activation of innate immunity by immunostimulatory DNA

Bacterial DNA and related synthetic immunostimulatory oligodeoxyribonucleotides (ISS-ODN) stimulate innate immunity. However, the molecular recognition mechanism that initiates signaling in response to bacterial DNA and ISS-ODN has not been identified. Herein, we demonstrate that administration of bacterial DNA and ISS-ODN to mice lacking the catalytic subunit of DNA-PK (DNA-PKcs) and in vitro stimulation of BMDM from these mice result in defective induction of IL-6 and IL-12. Further analysis using BMDM of IKKbeta(-/-) revealed that both DNA-PKcs and IKKbeta are essential for normal cytokine production in response to ISS-ODN or bacterial DNA. ISS-ODN and bacterial DNA activate DNA-PK, which in turn contributes to activation of IKK and NF-kappaB. These results reveal a novel role of DNA-PKcs in innate immune responses and a link between DNA repair and innate immunity.

Ku acts in a unique way at the mammalian telomere to prevent end joining

Telomeres are specialized DNA/protein structures that act as protective caps to prevent end fusion events and to distinguish the chromosome ends from double-strand breaks. We report that TRF1 and Ku form a complex at the telomere. The Ku and TRF1 complex is a specific high-affinity interaction, as demonstrated by several in vitro methods, and exists in human cells as determined by coimmunoprecipitation experiments. Ku does not bind telomeric DNA directly but localizes to telomeric repeats via its interaction with TRF1. Primary mouse embryonic fibroblasts that are deficient for Ku80 accumulated a large percentage of telomere fusions, establishing that Ku plays a critical role in telomere capping in mammalian cells. We propose that Ku localizes to internal regions of the telomere via a high-affinity interaction with TRF1. Therefore, Ku acts in a unique way at the telomere to prevent end joining.

Signal joint formation is also impaired in DNA-dependent protein kinase catalytic subunit knockout cells

The effort to elucidate the mechanism of V(D)J recombination has given rise to a dispute as to whether DNA-dependent protein kinase catalytic subunit (DNA-PKcs) contributes to signal joint formation (sjf). Observations reported to date are confusing. Analyses using DNA-PKcs-deficient cells could not conclude the requirement of DNA-PKcs for sjf, because sjf can be formed by end-joining activities which are diverse among cells other than those participating in V(D)J recombination. Here, we observed V(D)J recombination in DNA-PKcs knockout cells and showed that both signal and coding joint formation were clearly impaired in the cells. Subsequently, to directly demonstrate the requirement of DNA-PKcs for sjf, we introduced full-length cDNA of DNA-PKcs into the knockout cells. Furthermore, several mutant DNA-PKcs cDNA constructs designed from mutant cell lines (irs-20, V3, murine scid, and SX9) were also introduced into the cells to obtain further evidence indicating the involvement of DNA-PKcs in sjf. We found as a result that the full-length cDNA complemented the aberrant sjf and that the mutant cDNAs constructs also partially complemented it. Lastly, we looked at whether the kinase activity of DNA-PKcs is necessary for sjf and, as a result, demonstrated a close relationship between them. Our observations clearly indicate that the DNA-PKcs controls not only coding joint formation but also the sjf in V(D)J recombination through its kinase activity.

Evidence for simultaneous protein interactions between human Rad51 paralogs

In yeast, the Rad51-related proteins include Rad55 and Rad57, which form a heterodimer that interacts with Rad51. Five human Rad51 paralogs have been identified (XRCC2, XRCC3, Rad51B/Rad51L1, Rad51C/Rad51L2, and Rad51D/Rad51L3), and each interacts with one or more of the others. Previously we reported that HsRad51 interacts with XRCC3, and Rad51C interacts with XRCC3, Rad51B, and HsRad51. Here we report that in the yeast two-hybrid system, Rad51D interacts with XRCC2 and Rad51C. No other interactions, including self-interactions, were found, indicating that the observed interactions are specific. The yeast Rad51 interacts with human Rad51 and XRCC3, suggesting Rad51 conservation since the human yeast divergence. Data from yeast three-hybrid experiments indicate that a number of the pairs of interactions between human Rad51 paralogs can occur simultaneously. For example, Rad51B expression enhances the binding of Rad51C to XRCC3 and to HsRad51D, and Rad51C expression allows the indirect interaction of Rad51B with Rad51D. Experiments using 6xHis-tagged proteins in the baculovirus system confirm several of our yeast results, including Rad51B interaction with Rad51D only when Rad51C is simultaneously expressed and Rad51C interaction with XRCC2 only when Rad51D is present. These results suggest that these proteins may participate in one complex or multiple smaller ones.

DNA interstrand cross-links induce futile repair synthesis in mammalian cell extracts

DNA interstrand cross-links are induced by many carcinogens and anticancer drugs. It was previously shown that mammalian DNA excision repair nuclease makes dual incisions 5' to the cross-linked base of a psoralen cross-link, generating a gap of 22 to 28 nucleotides adjacent to the cross-link. We wished to find the fates of the gap and the cross-link in this complex structure under conditions conducive to repair synthesis, using cell extracts from wild-type and cross-linker-sensitive mutant cell lines. We found that the extracts from both types of strains filled in the gap but were severely defective in ligating the resulting nick and incapable of removing the cross-link. The net result was a futile damage-induced DNA synthesis which converted a gap into a nick without removing the damage. In addition, in this study, we showed that the structure-specific endonuclease, the XPF-ERCC1 heterodimer, acted as a 3'-to-5' exonuclease on cross-linked DNA in the presence of RPA. Collectively, these observations shed some light on the cellular processing of DNA cross-links and reveal that cross-links induce a futile DNA synthesis cycle that may constitute a signal for specific cellular responses to cross-linked DNA.

XRCC3 is required for efficient repair of chromosome breaks by homologous recombination

XRCC3 was originally identified as a human gene able to complement the DNA damage sensitivity, chromosomal instability and impaired growth of the mutant hamster cell line irs1SF. More recently, it has been cloned, sequenced and found to bear sequence homology to the highly conserved eukaryotic repair and recombination gene RAD51. The phenotype of irs1SF and the identification of XRCC3 as a member of the RAD51 gene family have suggested a role for XRCC3 in repair of DNA damage by homologous recombination. Homologous recombinational repair (HRR) of a specifically induced chromosomal double-strand break (DSB) was assayed in irs1SF cells with and without transient complementation by human XRCC3. Complementation with XRCC3 increased the frequencies of repair by 34- to 260-fold. The results confirm a role for XRCC3 in HRR of DNA DSB, and the importance of this repair pathway for the maintenance of chromosomal integrity in mammalian cells.

Regulation of double-strand break-induced mammalian homologous recombination by UBL1, a RAD51-interacting protein

Mammalian RAD51 protein plays essential roles in DNA homologous recombination, DNA repair and cell proliferation. RAD51 activities are regulated by its associated proteins. It was previously reported that a ubiquitin-like protein, UBL1, associates with RAD51 in the yeast two-hybrid system. One function of UBL1 is to covalently conjugate with target proteins and thus modify their function. In the present study we found that non-conjugated UBL1 forms a complex with RAD51 and RAD52 proteins in human cells. Overexpression of UBL1 down-regulates DNA double-strand break-induced homologous recombination in CHO cells and reduces cellular resistance to ionizing radiation in HT1080 cells. With or without overexpressed UBL1, most homologous recombination products arise by gene conversion. However, overexpression of UBL1 reduces the fraction of bidirectional gene conversion tracts. Overexpression of a mutant UBL1 that is incapable of being conjugated retains the ability to inhibit homologous recombination. These results suggest a regulatory role for UBL1 in homologous recombination.

The catalytic subunit of DNA-dependent protein kinase selectively regulates p53-dependent apoptosis but not cell-cycle arrest

DNA damage induced by ionizing radiation (IR) activates p53, leading to the regulation of downstream pathways that control cell-cycle progression and apoptosis. However, the mechanisms for the IR-induced p53 activation and the differential activation of pathways downstream of p53 are unclear. Here we provide evidence that the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs) serves as an upstream effector for p53 activation in response to IR, linking DNA damage to apoptosis. DNA-PKcs knockout (DNA-PKcs-/-) mice were exposed to whole-body IR, and the cell-cycle and apoptotic responses were examined in their thymuses. Our data show that IR induction of apoptosis and Bax expression, both mediated via p53, was significantly suppressed in the thymocytes of DNA-PKcs-/- mice. In contrast, IR-induced cell-cycle arrest and p21 expression were normal. Thus, DNA-PKcs deficiency selectively disrupts p53-dependent apoptosis but not cell-cycle arrest. We also confirmed previous findings that p21 induction was attenuated and cell-cycle arrest was defective in the thymoctyes of whole body-irradiated Atm-/- mice, but the apoptotic response was unperturbed. Taken together, our results support a model in which the upstream effectors DNA-PKcs and Atm selectively activate p53 to differentially regulate cell-cycle and apoptotic responses. Whereas Atm selects for cell-cycle arrest but not apoptosis, DNA-PKcs selects for apoptosis but not cell-cycle arrest.

DNA double-strand break repair proteins are required to cap the ends of mammalian chromosomes

Recent findings intriguingly place DNA double-strand break repair proteins at chromosome ends in yeast, where they help maintain normal telomere length and structure. In the present study, an essential telomere function, the ability to cap and thereby protect chromosomes from end-to-end fusions, was assessed in repair-deficient mouse cell lines. By using fluorescence in situ hybridization with a probe to telomeric DNA, spontaneously occurring chromosome aberrations were examined for telomere signal at the points of fusion, a clear indication of impaired end-capping. Telomeric fusions were not observed in any of the repair-proficient controls and occurred only rarely in a p53 null mutant. In striking contrast, chromosomal end fusions that retained telomeric sequence were observed in nontransformed DNA-PK(cs)-deficient cells, where they were a major source of chromosomal instability. Metacentric chromosomes created by telomeric fusion became even more abundant in these cells after spontaneous immortalization. Restoration of repair proficiency through transfection with a functional cDNA copy of the human DNA-PK(cs) gene reduced the number of fusions compared with a negative transfection control. Virally transformed cells derived from Ku70 and Ku80 knockout mice also displayed end-to-end fusions. These studies demonstrate that DNA double-strand break repair genes play a dual role in maintaining chromosomal stability in mammalian cells, the known role in repairing incidental DNA damage, as well as a new protective role in telomeric end-capping.

Ku is associated with the telomere in mammals

Telomeres are specialized DNA/protein complexes that comprise the ends of eukaryotic chromosomes. The highly expressed Ku heterodimer, composed of 70 and 80 K(d) subunits (Ku70 and Ku80), is the high-affinity DNA binding component of the DNA-dependent protein kinase. Ku is critical for nonhomologous DNA double-stranded break repair and site-specific recombination of V(D)J gene segments. Ku also plays an important role in telomere maintenance in yeast. Herein, we report, using an in vivo crosslinking method, that human and hamster telomeric DNAs specifically coimmunoprecipitate with human Ku80 after crosslinking. Localization of Ku to the telomere does not depend on the DNA-dependent protein kinase catalytic component. These findings suggest a direct link between Ku and the telomere in mammalian cells.

Purification and DNA binding properties of the ataxia-telangiectasia gene product ATM

The human neurodegenerative and cancer predisposition condition ataxia-telangiectasia is characterized at the cellular level by radiosensitivity, chromosomal instability, and impaired induction of ionizing radiation-induced cell cycle checkpoint controls. Recent work has revealed that the gene defective in ataxia-telangiectasia, termed ATM, encodes an approximately 350-kDa polypeptide, ATM, that is a member of the phosphatidylinositol 3-kinase family. We show that ATM binds DNA and exploit this to purify ATM to near homogeneity. Atomic force microscopy reveals that ATM exists in two populations, with sizes consistent with monomeric and tetrameric states. Atomic force microscopy analyses also show that ATM binds preferentially to DNA ends. This property is similar to that displayed by the DNA-dependent protein kinase catalytic subunit, a phosphatidylinositol 3-kinase family member that functions in DNA damage detection in conjunction with the DNA end-binding protein Ku. Furthermore, purified ATM contains a kinase activity that phosphorylates serine-15 of p53 in a DNA-stimulated manner. These results provide a biochemical assay system for ATM, support genetic data indicating distinct roles for DNA-dependent protein kinase and ATM, and suggest how ATM may signal the presence of DNA damage to p53 and other downstream effectors.

Enhanced phosphorylation of p53 serine 18 following DNA damage in DNA-dependent protein kinase catalytic subunit-deficient cells

DNA-dependent protein kinase (DNA-PK) controls signal transduction following DNA damage. However, the molecular mechanism of the signal transduction has been elusive. A number of candidates for substrates of DNA-PK have been reported on the basis of the in vitro assay system. In particular, the Ser-15 amino acid residue in p53 was one of the first such in vitro substrates to be described, and it has drawn considerable attention due to its biological significance. Moreover, p53 Ser-15 is a site that has been shown to be phosphorylated in response to DNA damage. In addition, crucial evidence indicating that DNA-PK controls the transactivation of p53 following DNA damage was reported quite recently. To clarify these important issues, we conducted the experiments with dna-pkcs null mutant cells, including gene knockout cells. As a result, we detected enhanced phosphorylation of p53 Ser-18, which corresponds to Ser-15 of human p53, and significant expression of p21 and mdm2 following ionizing radiation. Furthermore, we identified a missense point mutation in the p53 DNA-binding motif region in SCGR11 cells, which were established from severe combined immunodeficient (SCID) mice and used for previous study on the role of DNA-PK in p53 transactivation. Our observation clearly indicates that DNA-PK catalytic subunit does not phosphorylate p53 Ser-18 in vivo or control the transactivation of p53 in response to DNA damage, and these results further emphasize the different pathways in which ataxia telangiectasia-mutated (ATM) and DNA-PK operate following radiation damage.

The XRCC2 and XRCC3 repair genes are required for chromosome stability in mammalian cells

The irs1 and irs1SF hamster cell lines are mutated for the XRCC2 and XRCC3 genes, respectively. Both show heightened sensitivity to ionizing radiation and particularly to the DNA cross-linking chemical mitomycin C (MMC). Frequencies of spontaneous chromosomal aberration have previously been reported to be higher in these two cell lines than in parental, wild-type cell lines. Microcell-mediated chromosome transfer was used to introduce complementing or non-complementing human chromosomes into each cell line. irs1 cells received human chromosome 7 (which contains the human XRCC2 gene) or, as a control, human chromosome 4. irs1SF cells received human chromosome 14 (which contains the XRCC3 gene) or human chromosome 7. For each set of hybrid cell lines, clones carrying the complementing human chromosome recovered MMC resistance to near-wild-type levels, while control clones carrying noncomplementing chromosomes remained sensitive to MMC. Fluorescence in situ hybridization with a human-specific probe revealed that the human chromosome in complemented clones remained intact in almost all cells even after extended passage. However, the human chromosome in noncomplemented clones frequently underwent chromosome rearrangements including breaks, deletions, and translocations. Chromosome aberrations accumulated slowly in the noncomplemented clones over subsequent passages, with some particular deletions and unbalanced translocations persistently transmitted throughout individual subclones. Our results indicate that the XRCC2 and XRCC3 genes, which are now considered members of the RAD51 gene family, play essential roles in maintaining chromosome stability during cell division. This may reflect roles in DNA repair, possibly via homologous recombination.

DNA-dependent protein kinase-independent activation of p53 in response to DNA damage

Phosphorylation at serine 15 of the human p53 tumor suppressor protein is induced by DNA damage and correlates with accumulation of p53 and its activation as a transcription factor. The DNA-dependent protein kinase (DNA-PK) can phosphorylate serine 15 of human p53 and the homologous serine 18 of murine p53 in vitro. Contradictory reports exist about the requirement for DNA-PK in vivo for p53 activation and cell cycle arrest in response to ionizing radiation. While primary SCID (severe combined immunodeficiency) cells, that have defective DNA-PK, show normal p53 activation and cell cycle arrest, a transcriptionally inert form of p53 is induced in the SCID cell line SCGR11. In order to unambiguously define the role of the DNA-PK catalytic subunit (DNA-PKcs) in p53 activation, we examined p53 phosphorylation in mouse embryonic fibroblasts (MEFs) from DNA-PKcs-null mice. We found a similar pattern of serine 18 phosphorylation and accumulation of p53 in response to irradiation in both control and DNA-PKcs-null MEFs. The induced p53 was capable of sequence-specific DNA binding even in the absence of DNA-PKcs. Transactivation of the cyclin-dependent-kinase inhibitor p21, a downstream target of p53, and the G1 cell cycle checkpoint were also found to be normal in the DNA-PKcs -/- MEFs. Our results demonstrate that DNA-PKcs, unlike the related ATM protein, is not essential for the activation of p53 and G1 cell cycle arrest in response to ionizing radiation.

The binding interface between an E2 (UBC9) and a ubiquitin homologue (UBL1)

Human UBC9 is a member of the E2 (ubiquitin conjugation enzyme) family of proteins. Instead of conjugating to ubiquitin, it conjugates with a ubiquitin homologue UBL1 (also known as SUMO-1, GMP1, SMTP3, PIC1, and sentrin). UBC9 has been shown to be involved in cell cycle regulation, DNA repair, and p53-dependent processes. The binding interfaces of the UBC9 and UBL1 complex have been determined by chemical shift perturbation using nuclear magnetic resonance spectroscopy. The binding site of UBL1 resides on the ubiquitin domain, and the binding site of UBC9 is located on a structurally conserved region of E2. Because the UBC9-UBL1 system shares many similarities with the ubiquitin system in structures and in conjugation with each other and with target proteins, the observed binding interfaces may be conserved in E2-ubiquitin interactions in general.

Isolation of Ku70-binding proteins (KUBs)

DNA-dependent protein kinase (DNA-PK) plays a critical role in resealing DNA double-stand breaks by non-homologous end joining. Aside from DNA-PK, XRCC4 and DNA ligase IV, other proteins which play a role(s) in this repair pathway remain unknown; DNA-PK contains a catalytic subunit (DNA-PKcs) and a DNA binding subunit (Ku70 and Ku80). We isolated Ku70-binding proteins (KUB1-KUB4) using yeast two-hybrid analyses. Sequence analyses revealed KUB1 to be apolipoprotein J (apoJ), also known as X-ray-inducible transcript 8 (XIP8), testosterone-repressed prostate message-2 (TRPM-2) and clusterin. KUB2 is Ku80. KUB3 and KUB4 are unknown, >10 kb trans-cripts. Interactions of apoJ/XIP8 or KUB3 with Ku70 were confirmed by co-immunoprecipitation analyses in MCF-7:WS8 breast cancer or IMR-90 normal lung fibroblast cells, respectively. The interaction of apoJ/XIP8 with Ku70 was confirmed by far-western analyses. Stable over-expression of full-length apoJ/XIP8 in MCF-7:WS8 caused decreased Ku70/Ku80 DNA end binding that was restored by apoJ/XIP8 monoclonal antibodies. The role of apoJ/XIP8 in ionizing radiation resistance/sensitivity is under investigation.