Effects of Modes and Timings of Delivery on Feto-Maternal Outcomes in Women with Severe Preeclampsia: A Multi-Center Survey in Mainland China

BACKGROUND

Pregnancy termination is the only effective treatment for preeclampsia. However, there are controversies on the selection of modes of delivery. The objective was to evaluate whether mode of delivery in labor differentially affected the rate of adverse maternal outcomes related to severe preeclampsia.

OBJECTIVE

This study aimed to evaluate whether the modes and timings of delivery affects adverse maternal outcomes in pre-eclampsia.

METHODS

Clinical data from 2516 singleton pregnant women with severe preeclampsia were collected in a multicenter, large-sample, cross-sectional study in mainland China. The patients were divided into cesarean-delivery (CD) and vaginal-delivery (VD) categories and then into Group 1 (≤27+ 6 weeks), Group 2 (28-33+ 6 weeks), Group 3 (34-36+ 6 weeks), and Group 4 (≥37 weeks) according to the mode of delivery and gestational weeks. All data were exported into the SPSS software and analyzed by the Student's t-tests or Mann-Whitney U-tests and the chi-squared test.

RESULTS

A total of 2516 singleton pregnant women with severe preeclampsia were collected and the overall cesarean section rate was 84.9%. The vaginal delivery rates among the four groups were significantly different with 70%, 19.7%, 6.6%, 15.1% in groups 1, 2, 3, 4, respectively (P<0.05), while perinatal mortality was lower in the CD groups than VD groups (3.3% vs 50.4%, P<0.05). The neonatal asphyxia rate was significantly higher with CD than with VD in Group 2 (36.4% vs 12.9%, P<0.05). The perinatal mortality with CD, 3, and 4 was significantly lower than with VD (10.0% vs 68.5% in Groups 2, 2.3% vs 28.3% in Groups 3, 0.8% vs 5.6% in Groups 4, all P<0.05).

CONCLUSION

Most pregnant women with severe preeclampsia opted for a cesarean section in China. The lower perinatal mortality was associated with cesarean section, but the rate of maternal PPH or mortality was not related with the mode of delivery. So cesarean section is the safer delivery mode for the pregnant women complicated with severe preeclampsia.

[Study on the related factors of intestinal obstruction after cesarean section]

Objective: To analyze the related factors of intestinal obstruction after cesarean section. Methods: From April 2009 to April 2019, 500 patients with cesarean section and postoperative intestinal obstruction in Beijing Maternity Hospital Affiliated to Capital Medical University were taken as the case group, and 500 patients without postoperative intestinal obstruction who underwent cesarean section on the same day as the case group were taken as the control group. The data of patients' general characteristics, pregnancy complications, blood routine and biochemical indexes, and operation related factors were collected to compare the differences between patients with intestinal obstruction and patients without intestinal obstruction. Multivariate logistic regression model was used to analyze the related factors of intestinal obstruction after cesarean section. Results: The age of 500 patients with intestinal obstruction after cesarean section was (33.3±4.2) years, and the age of 500 patients without intestinal obstruction after cesarean section was (31.6±3.9) years. The incidence of pregnancy complications in patients with intestinal obstruction was higher than that in patients without intestinal obstruction (all P<0.05). Multivariate analysis showed that preoperative anemia [OR(95%CI) of 5.318(1.522-18.580), P=0.009], postoperative low protein [OR(95%CI) of 0.376(0.143-0.993), P=0.048], intraoperative bleeding ≥500 ml [OR(95%CI) of 3.085(1.551-6.136), P=0.001],intraoperative adhesion [OR(95%CI) of 2.856(1.285-6.347), P=0.010] were the risk factor of intestinal obstruction after cesarean section. The intraoperative application of antiadhesion drugs [OR(95%CI) of 0.322(0.158-0.654), P=0.002] was the protective factor of intestinal obstruction after cesarean section. Conclusions: Patients with anemia and low protein have an increased risk of intestinal obstruction after cesarean section.

Whole-exome sequencing reveals POLR3B variants associated with progeria-related Wiedemann-Rautenstrauch syndrome

Background

Wiedemann-Rautenstrauch syndrome (WRS) is a rare autosomal recessive neonatal progeroid disorder characterized by prenatal and postnatal growth retardation, short stature, a progeroid appearance, hypotonia, and mental impairment.

Case presentation

A 6-year-old patient, who initially presented with multiple postnatal abnormalities, facial dysplasia, micrognathia, skull appearance, hallux valgus, and congenital dislocation of the hip, was recruited in this study. The patient was initially diagnosed with progeria. The mother of the patient had abnormal fetal development during her second pregnancy check-up, and the clinical phenotype of the fetus was similar to that of the patient. Whole-exome sequencing (WES) of the patient was performed, and POLR3B compound heterozygous variants—c.2191G > C:p.E731Q and c.3046G > A:p.V1016M—were identified in the patient. Using Sanger sequencing, we found that the phenotypes and genotypes were segregated within the pedigree. These two variants are novel and not found in the gnomAD and 1000 Genomes databases. The two mutation sites are highly conserved between humans and zebrafish.

Conclusions

Our study not only identified a novel WRS-associated gene, POLR3B, but also broadened the mutational and phenotypic spectra of POLR3B. Furthermore, WES may be useful for identifying rare disease-related genetic variants.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13052-021-01112-6.

Quantitative proteomic analysis of down syndrome biomarkers in maternal serum using isobaric tags for relative and absolute quantification (iTRAQ)

Prenatal diagnosis of Down syndrome (DS) is based on calculated risk involving maternal age, biochemical and ultrasonographic markers, and, more recently, cell-free DNA (cfDNA). The present study was designed to identify Down Syndrome biomarkers in maternal serum. We quantified the changes in maternal serum protein levels between 10 non-pregnant women, 10 pregnant women with healthy fetuses, and 10 pregnant women with DS fetuses using isobaric tags for relative and absolute quantification (iTRAQ). We subsequently conducted a Gene Ontology (GO) analysis. A total of 470 proteins were identified, 11 of which had significantly different serum levels between the DS fetus group and Healthy fetuses group. Our data shows the identified proteins may be relevant to DS and constitute potential DS biomarkers.

Intrapartum interventions that affect maternal and neonatal outcomes for vaginal birth after cesarean section

Objective

To investigate maternal and neonatal outcomes after different intrapartum interventions for vaginal birth after cesarean section (VBAC) in mainland China.

Methods

A retrospective study was performed on 143 VBAC cases from Beijing Obstetrics and Gynecology Hospital between January 2015 and November 2016. These cases were divided into two groups on the basis of different intrapartum interventions. Maternal and neonatal outcomes were compared.

Results

The durations of the first stage and total labor after oxytocin were significantly longer than those before oxytocin use. The proportion of operative vaginal delivery with oxytocin was significantly higher than that without oxytocin (43.9% vs. 11.8%). The times of the first stage, second stage, and total labor with analgesia were significantly longer than those without analgesia (548.4±198.1 vs. 341.8±233.0 minutes, 52.0±38.9 vs. 36.0± 29.1 minutes, and 606.3±212.1 vs. 387.3±233.0 minutes, respectively). Postpartum hemorrhage and operative vaginal delivery occurred significantly more frequently in women with epidural analgesia than in those without epidural analgesia (29.7% vs. 12.3 and 35.1% vs. 16.0%, respectively).

Conclusions

Induction can increase the rate of operative vaginal delivery in VBAC. Oxytocin and epidural analgesia may increase the risk of operative vaginal delivery, and may be associated with a prolonged duration of labor.

Labor Onset, Oxytocin Use, and Epidural Anesthesia for Vaginal Birth after Cesarean Section and Associated Effects on Maternal and Neonatal Outcomes in a Tertiary Hospital in China: A Retrospective Study

Background

In the mainland of China, the trial of labor after cesarean section is still a relatively new technique. In this study, we aimed to investigate the effects of labor onset, oxytocin use, and epidural anesthesia on maternal and neonatal outcomes for vaginal birth after cesarean section (VBAC) in a tertiary hospital in China.

Methods

This was a retrospective study carried out on 212 VBAC cases between January 2015 and June 2017 in Beijing Obstetrics and Gynecology Hospital, Capital Medical University. Relevant data were acquired on a form, including maternal age, gravidity and parity, body mass index before pregnancy, weight gain during pregnancy, type of labor onset, gestational age, the use of oxytocin and epidural anesthesia, birth mode, the duration of labor, and neonatal weight. The factors affecting maternal and neonatal outcomes for cases involving VBAC, especially with regards to postpartum hemorrhage (PPH) and fetal distress, were evaluated by univariate analysis and multivariable logistic regression.

Results

Data showed that 36 women (17.0%) had postpartum hemorrhage (PPH) and 51 cases (24.1%) featured fetal distress. Normal delivery took place for 163 infants (76.9%) while 49 infants (23.1%) underwent operative vaginal deliveries with forceps. There were 178 cases (84.0%) of spontaneous labor and 34 cases (16.0%) required induction. Oxytocin was used in 54 cases (25.5%) to strengthen uterine contraction, and 65 cases (30.7%) received epidural anesthesia. The rate of normal delivery in cases involving PPH was significantly lower than those without PPH (61.1% vs. 80.1%; χ² = 6.07, P = 0.01). Multivariate logistic analysis showed that the intrapartum administration of oxytocin (odds ratio [OR] = 2.47; 95% confidence interval [CI] = 1.07-5.74; P = 0.04) and birth mode (OR = 0.40; 95% CI = 0.18-0.87; P = 0.02) was significantly associated with PPH in VBAC cases. Operative vaginal delivery occurred more frequently in the group with fetal distress than the group without (49.0% vs. 14.9%, χ² = 25.36, P = 0.00). Multivariate logistic analysis also revealed that the duration of total labor (OR = 1.01; 95% CI = 1.00-1.03; P = 0.04) and the gestational week of delivery (OR = 1.08; 95% CI = 1.05-1.11; P = 0.00) were significantly associated with fetal distress in VBAC.

Conclusions

The administration of oxytocin during labor and birth was identified as a protective factor for PPH in VBAC while birth mode was identified as a risk factor. Finally, the duration of total labor and the gestational week of delivery were identified as risk factors for fetal distress in cases of VBAC. This information might help obstetricians provide appropriate interventions during labor and birth for VBAC.

[The effect of short-term exposure to ambient NO(2) on lung function and fractional exhaled nitric oxide in 33 chronic obstructive pulmonary disease patients]

Objectives: To investigate the effect of short-term exposure to ambient NO(2) has influence on lung function and fractional exhaled nitric oxide (FeNO) in chronic obstructive pulmonary disease (COPD) patients. Methods: A panel of doctor-diagnosed stable COPD patients (n=33) were recruited and repeatedly measured for lung function and FeNO from December 2013 to October 2014. The patients who lived in Beijing for more than one year and aged between 60 and 85 years old were included in the study. We excluded patients with asthma, bronchial tensor, lung cancer and other respiratory disorders other than chronic obstructive pulmonary disease and occupational exposure and chest trauma surgery patients. Because the frequency of each subject visiting to the hospital was different, a total of 170 times of lung function measurements and 215 times of FeNO measurements were conducted. At the same time, the atmospheric NO(2) data of Beijing environmental monitoring station near the residence of each patient during the study period were collected from 1 day to 7 days lag before the measurement. Effects of short-term NO(2) exposure on lung function and FeNO in COPD patients were estimated by linear mixed-effects models. Results: The subjects' forced vital capacity (FVC), forced expiratory volume in one second (FEV(1)), peak expiratory flow (PEF), and exhaled NO of subjects were (3.26±0.83) L, (1.66±0.61) L, (4.13±1.77) L/s, and (48.99±14.30) μg/m(3), respectively. The concentration of NO(2) was (70.3±34.2) μg/m(3) and the interquartile range (IQR) was 39.0 μg/m(3). Short-term exposure to NO(2) resulted in a significant decrease in FVC among COPD patients' which was most obvious in 2 days lag. Every quartile range increased in NO(2) (39 μg/m(3), 2 day) would cause a 1.84% (95%CI: -3.20%- -0.48%) reduction in FVC. The effects of exposure to higher concentration of NO(2) (≥58.0 μg/m(3)) on FVC estimate was -2.32% (95%CI: -4.15%- -0.48%)(P=0.02). No significant relevance of FeNO and NO(2) was observed in this study. Conclusions: Short term exposure to ambient NO(2) may bring down pulmonary function in COPD patients.

[Analysis of factors affecting vaginal birth after cesarean]

OBJECTIVE

To investigate the factors affecting the vaginal birth after cesarean (VBAC).

METHODS

Totaly 298 women who underwent trial of labor after cesarean section (TOLAC) from Jan 2015 to Dec 2015 were recruited from Beijing Obstetrics and Gynecology Hospital, FuXing Hospital, Tongzhou Maternal and Child Health Hospital of Beijing, the Second Affiliated Hospital of Chongqing Medical University and the People's Hospital of Chengyang District of Qingdao. The maternal age, the interval from the last cesarean section, the body mass index (BMI) before pregnancy, the weight gain during pregnancy, the way into labor, the Bishop score before labor, the gestational age and the birth weight of the neonate were recorded in a self-made form. The factors affecting VBAC were analyzed by univariate analysis and multivariable logistic regression.

RESULTS

(1)The incidence of VBAC, uterine rupture, postpartum hemorrhage and neonatal asphyxia were 70.5% (210/298), 2.7% (8/298), 9.4% (28/298) and 1.3% (4/298), respectively. No maternal death and perinatal death occurred. (2)The univariate analysis suggested that the maternal age, the BMI before pregnancy, the Bishop score before labor, the labor induction, the gestational age at delivery and the neonatal weight were factors affecting VBAC. The maternal age and the Bishop score before labor were significantly higher in the VBAC group than in the unsuccessful TOLAC group(P<0.05). While the BMI before pregnancy, the induction rate, the gestational weeks at delivery and the birth weight of the neonate were significantly lower in the VBAC group than in the unsuccessful TOLAC group (P<0.05). Multivariable logistic regression analysis showed that successful VBAC was affected by the maternal age, the BMI before pregnancy, the Bishop score before labor and the birth weight of the neonates(P<0.05).

CONCLUSION

The maternal age, the BMI before pregnancy, the Bishop score before labor and the birth weight of neonate are the main factors affecting VBAC.

Rate dependent of strength in metallic glasses at different temperatures

The correlation between the strength at the macroscale and the elastic deformation as well as shear cracking behavior at the microscale of bulk metallic glasses (BMGs) is investigated. The temperatures of 298 K and 77 K as well as the strain rate ranging from 10⁻⁶ s⁻¹ to 10⁻² s⁻¹ are applied to the BMGs, in which the mechanical responses of the BMGs are profiled through the compression tests. The yield strength is associated with the activation of the elementary deformation unit, which is insensitive to the strain rate. The maximum compressive strength is linked to the crack propagation during shear fracture process, which is influenced by the strain rate. The cryogenic temperature of 77 K significantly improves the yield strength and the maximum compressive strength of the BMGs.

p53 and Sp1 cooperate to regulate the expression of Epstein-Barr viral Zta protein

Epstein-Barr virus (EBV) belongs to the gammaherpesvirus family. To produce infectious progeny, EBV reactivates from latency into the lytic cycle by expressing the determinative lytic transactivator, Zta. In the presence of histone deacetylase inhibitor (HDACi), p53 is a prerequisite for the initiation of the EBV lytic cycle by facilitating the expression of Zta. In this study, a serial mutational analysis of Zta promoter (Zp) indicated an important role for the ZID element in responding to HDACi induction and p53 binds to this ZID element together with Sp1, a universal transcription factor. Abolition of the DNA-binding ability of Sp1 reduces the inducibility of ZID by HDACi and also reduces the amount of p53 binding to ZID. Finally, it was shown that EBV in p53-positive-lymphoblastoid cell lines (LCLs) can enter into the lytic cycle spontaneously; however, knockdown of p53 in LCLs leads to retardation of EBV reactivation.

Manipulating nanoscale light fields with the asymmetric bowtie nano-colorsorter

We present a class of devices called Asymmetric Bowtie nano-Colorsorters. These devices are specifically engineered to not only capture and confine optical fields, but also to spectrally filter and steer them while maintaining nanoscale field distributions. We show that spectral properties and localized spatial mode distributions can be readily tuned by controlled asymmetry. Nano-Colorsorters can control light's spatial and spectral distributions at the nanoscale and thus significantly impact applications ranging from broadband light harvesting to ultrafast wavelength-selective photodetection.

Early diagnosis of polyomavirus type BK infection in tailoring immunosuppression for kidney transplant patients: screening with urine qualitative polymerase chain reaction assay

Polyomavirus type BK (BKV) nephropathy is increasingly a significant cause of graft dysfunction and even failure. Early diagnosis followed by reduction of immunosuppression has been associated with an improved prognosis. We screened 250 patients with the urine qualitative polymerase chain reaction (PCR) for BKV DNA. We followed with blood BKV PCR if the urine screen was positive and then reduced immunosuppression in viremic patients. One hundred ninety-nine patients (80%) had no viuria; 43 (17%) viuria; and 8 (3%) both viuria and viremia. Graft biopsy performed in three patients (1%) with viremia and impaired graft function all revealed BKV nephropathy. After 6 months of follow-up, seven out of eight viremic patients (88%) had negative repeat blood PCR and stabilized graft function. An early diagnosis of BKV infection with reduction of immunosuppression may reverse viremia and retard progression of BKV nephropathy. BKV screening by PCR assays should be considered in kidney transplant recipients, especially those with impaired graft function.

Role of VraSR in antibiotic resistance and antibiotic-induced stress response in Staphylococcus aureus

Exposure of Staphylococcus aureus to cell wall inhibitors induces massive overexpression of a number of genes, provided that the VraSR two-component sensory regulatory system is intact. Inactivation of vraS blocks this transcriptional response and also causes a drastic reduction in the levels of resistance to beta-lactam antibiotics and vancomycin. We used an experimental system in which the essential cell wall synthesis gene of S. aureus, pbpB, was put under the control of an isopropyl-beta-d-thiogalactopyranoside-inducible promoter in order to induce reversible perturbations in cell wall synthesis without the use of any cell wall-active inhibitor. Changes in the level of transcription of pbpB were rapidly followed by parallel changes in the vraSR signal, and the abundance of the pbpB transcript was precisely mirrored by the abundance of the transcripts of vraSR and some additional genes that belong to the VraSR regulon. Beta-lactam resistance in S. aureus appears to involve a complex stress response in which VraSR performs the critical role of a sentinel system capable of sensing the perturbation of cell wall synthesis and allowing mobilization of genes that are essential for the generation of a highly resistant phenotype. One of the sites in cell wall synthesis "sensed" by the VraSR system appears to be a step catalyzed by PBP 2.

Atomic-Scale Coupling of Photons to Single-Molecule Junctions

Spatial resolution at the atomic scale has been achieved in the coupling of light to single molecules adsorbed on a surface. Electron transfer to a single molecule induced by green to near-infrared light in the junction of a scanning tunneling microscope (STM) exhibited spatially varying probability that is confined within the molecule. The mechanism involves photo-induced resonant tunneling in which a photoexcited electron in the STM tip is transferred to the molecule. The coupling of photons to the tunneling process provides a pathway to explore molecular dynamics with the combined capabilities of lasers and the STM.

Tunneling rates in electron transport through double-barrier molecular junctions in a scanning tunneling microscope

The scanning tunneling microscope enables atomic-scale measurements of electron transport through individual molecules. Copper phthalocyanine and magnesium porphine molecules adsorbed on a thin oxide film grown on the NiAl(110) surface were probed. The single-molecule junctions contained two tunneling barriers, vacuum gap, and oxide film. Differential conductance spectroscopy shows that electron transport occurs via vibronic states of the molecules. The intensity of spectral peaks corresponding to the individual vibronic states depends on the relative electron tunneling rates through the two barriers of the junction, as found by varying the vacuum gap tunneling rate by changing the height of the scanning tunneling microscope tip above the molecule. A simple, sequential tunneling model explains the observed trends.

Control of relative tunneling rates in single molecule bipolar electron transport

The influence of relative electron tunneling rates on electron transport in a double-barrier single-molecule junction is studied. The junction is defined by positioning a scanning tunneling microscope tip above a copper phthalocyanine molecule adsorbed on a thin oxide film grown on the NiAl(110) surface. By tuning the tip-molecule separation, the ratio of tunneling rates through the two barriers, vacuum and oxide, is controlled. This results in dramatic changes in the relative intensities of individual conduction channels, associated with different vibronic states of the molecule.

Metabolism of territrem a in liver microsomes from wistar rats: 2. Sex differences and regulation with gonadal hormones and phenobarbital

The aim of the present study was to assess the effects of sex difference on metabolism of territrem A (TRA) by liver microsomes from 7-wk-old Wistar rats. Metabolism of TRA to 2-dihydro-4beta-demethylterritrem A (MA2) through 4beta-hydroxymethyl-4beta-demethylterritrem A (MA1) and 4beta-oxo-4beta-demethylterritrem A (MAX) was observed in intact male rats. However, in intact female rats only MA1 was formed, although the amount of MA, formed in females was much less than in males. Phenobarbital pretreatment enhanced this step and was not affected by gonadectomy. In the gonadectomized rats of both sexes, MA2 was formed from TRA when the animals were further treated by testosterone and was significantly enhanced by treatment with phenobarbital. However, estradiol treatment or estradiol in combination with phenobarbital treatment did not affect MA2 formation from TRA in gonadectomized rats.

Metabolism of territrem a by liver microsomes of Wistar rats: identification of the metabolites and their metabolic sequence

The metabolism of territrem A (TRA) was investigated in liver microsomes of male Wistar rats. The results indicated that three metabolites were produced from TRA and these metabolic reactions were inhibited by metyrapone, an inhibitor of cytochrome P-450. Based on analysis by high-performance liquid chromatography (HPLC), mass, and nuclear magnetic resonance (NMR) spectroscopic techniques, the structure of these metabolites were identified as 4beta-hydroxymethyl-4beta-demethylterritrem A (MA1), 4beta-oxo-4beta-demethylterritrem A (MAX), and 2-dihydro-4beta-demethylterritrem A (MA2). It was proposed that reactions proceeded by three sequential oxidative reactions in the pyran moiety of TRA: first, hydroxylation at the 4beta-C methyl group of TRA to form MA1; second, oxidation at the 4beta hydroxyl group of MA, to form MAX; and third, decarbonylation at the 4beta-C oxo group of MAX to form MA2.

Recruitment of the mecA gene homologue of Staphylococcus sciuri into a resistance determinant and expression of the resistant phenotype in Staphylococcus aureus

Strains of methicillin-resistant Staphylococcus aureus (MRSA) have become the most important causative agents of hospital-acquired diseases worldwide. The genetic determinant of resistance, mecA, is not a gene native to S. aureus but was acquired from an extraspecies source by an unknown mechanism. We recently identified a close homologue of this gene in isolates of Staphylococcus sciuri, a taxonomically primitive staphylococcal species recovered most frequently from rodents and primitive mammals. In spite of the close sequence similarity between the mecA homologue of S. sciuri and the antibiotic resistance determinant mecA of S. aureus, S. sciuri strains were found to be uniformly susceptible to beta-lactam antibiotics. In an attempt to activate the apparently "silent" mecA gene of S. sciuri, a methicillin-resistant derivative, K1M200 (for which the MIC of methicillin is 200 microg/ml), was obtained through stepwise exposure of the parental strain S. sciuri K1 (methicillin MIC of 4 microg/ml) to increasing concentrations of methicillin. DNA sequencing of the mecA homologue from K1M200 revealed the introduction of a point mutation into the -10 consensus of the promoter: the replacement of a thymine residue at nucleotide 1577 in the susceptible strain K1 by adenine in the resistant strain K1M200, which was accompanied by a drastic increase in transcription rate and the appearance of a new protein that reacted with monoclonal antibody prepared against the penicillin-binding protein 2A (PBP2A), i.e., the gene product of S. aureus mecA. Transduction of mecA from K1M200 (cloned into a plasmid vector) into a methicillin-susceptible S. aureus mutant resulted in a significant increase of methicillin resistance (from a methicillin MIC of 4 micro/ml to 12 and up to 50 microg/ml), the appearance of a low-affinity PBP detectable by the fluorographic assay, and the production of a protein that reacted in a Western blot with monoclonal antibody to PBP2A. Antibiotic resistance and the protein products disappeared upon removal of the plasmid-borne mecA homologue. The observations support the proposition that the mecA homologue ubiquitous in the antibiotic-susceptible animal species S. sciuri may be an evolutionary precursor of the methicillin resistance gene mecA of the pathogenic strains of MRSA.

Genetic organization of the downstream region of the mecA element in methicillin-resistant Staphylococcus aureus isolates carrying different polymorphisms of this region

We describe here the genetic organization of the mec element downstream of the mecA gene in 34 different methicillin-resistant Staphylococcus aureus (MRSA) clinical isolates carrying 13 of the most frequent polymorphisms of mecA and representing the major epidemic clones of MRSA. All polymorphisms carried three common genetic elements: the hypervariable region, a copy of IS431, and a unique 2-kb sequence (downstream constant segment, or dcs) for which no homologous sequences are found in data banks. Polymorphisms of the downstream region were shown to be caused by the presence of linearized plasmids flanked by insertion sequences (pUB110, pT181, and pI258) and the autonomous insertion sequence IS256.

Molecular cloning and DNA sequencing of the Staphylococcus aureus UDP-N-acetylmuramyl tripeptide synthetase (murE) gene, essential for the optimal expression of methicillin resistance

The Tn551 insertion in mutant RUSA235 of a highly methicillin resistant Staphylococcus aureus strain results in drastic reduction in the level of methicillin resistance and abnormalities, both in the composition of the peptidoglycan and of the cell wall precursor pool. Cloning and sequencing of the inactivated gene indicates that it is the murE gene of Staphylococcus aureus.

The Staphylococcus aureus transposon Tn551: complete nucleotide sequence and transcriptional analysis of the expression of the erythromycin resistance gene

The complete nucleotide sequence of Staphylococcus aureus transposon Tn551 was determined. The 5,266-bp sequence encoded five putative proteins. Comparison of the nucleotide sequence of Tn551 with that of the enterococcal transposon Tn917 showed that the two transposons were 99.8% identical and differed only at 11 positions along the entire sequence. The genetic organization of Tn551 was also identical to that of Tn917. Northern analysis of RNA prepared from a staphylococcal strain bearing Tn551 displayed three erm-associated transcripts that were constitutively produced. Mapping of the 5' ends of the transcripts by primer extension suggested that the constitutive transcription of erm was initiated from a nucleotide located 5 bp downstream of ORF1. A second set of three erythromycin-inducible transcripts was also detected and these showed a pattern similar to that described for Tn917. A simple and rapid method is described for the use of the Tn551 sequence information in sequencing transposon-inactivated staphylococcal genes.

Inactivation of the methicillin resistance gene mecA in vancomycin-resistant Staphylococcus aureus

Acquisition of high-level resistance to vancomycin in the laboratory mutant VM50 (vancomycin MIC increased from 1.5 to 100 microg/ml) was accompanied by the appearance of a heterogeneous phenotype and a virtual loss in methicillin resistance: in most cells of cultures of VM50 the methicillin MIC of the parental strain was reduced from 800 to 1.5 microg/ml with only a subpopulation (10(-5)) retaining methicillin resistance at near the parental level (MIC of 400 microg/ml). Interestingly, the vancomycin MIC of this subpopulation was less (25 microg/ml) than that of VM50 (100 microg/ml). A similar antagonism between methicillin and vancomycin resistance levels was observed upon introduction of an intact mecA into VM50 on a plasmid vector: methicillin resistance of the majority of cells increased from 1.5 to 100 microg/ml while the vancomycin MIC declined from 100 to 12/25 microg/ml. Membrane preparations from mutant VM50 showed no detectable penicillin-binding protein (PBP) 2A by the fluorographic assay. Sequencing of the mecA gene resident in mutant VM50 indicated the presence of a 19-bp duplication between nucleotide residues 280-298, leading to the generation of a stop codon TAA starting at nucleotide position 286.

Antibiotic resistance as a stress response: complete sequencing of a large number of chromosomal loci in Staphylococcus aureus strain COL that impact on the expression of resistance to methicillin

Tn551 inactivation has identified several determinants--fem or auxiliary genes--that, in addition to the mecA gene, are also critical for the expression of high-level and homogeneous resistance to methicillin. Genetic and/or biochemical analysis has shown that of the nearly dozen aux mutations described so far most are in genes involved in cell wall synthesis (murE, pbp2, glmM, glnR, femA/B, llm, etc.) or in complex regulatory functions (sigmaB), suggesting that optimal expression of resistance may involve the cooperative functioning of a number of genes in cell wall metabolism as well as stress response. The exact mechanism of these functions is not known. In an attempt to explore this unusual aspect of methicillin resistance more fully, a Tn551 transposon library, constructed in the background of the highly and homogeneously methicillin-resistant Staphylococcus aureus strain COL, was screened for all independent insertional mutants in which the level of methicillin resistance of the parental strain (MIC, 1,600 microg/ml) was reduced by at least 15-fold and up to 500-fold. We now describe the sequencing of 21 Tn551-inactivated genes and their vicinities in 23 new auxiliary mutants that have been studied before. Using the inverted polymerase chain reaction (IPCR), we amplified fragments corresponding to the right and left junction of the Tn551 insertions, which were then sequenced by primer walking. The two largest groups of these new auxiliary genes encoded either proteins of unknown functions (6 genes) or showed homology with genes encoding proteins involved with putative sensory/regulatory activities (7 genes: protein kinases, ABC transporters, and a catabolite control protein). Sequencing upstream and downstream allowed the identification of a number of additional open reading frames, some of which may also include functions relevant for the expression of antibiotic resistance.

Mrp--a new auxiliary gene essential for optimal expression of methicillin resistance in Staphylococcus aureus

Screening of a library of Tn551 insertional mutants selected for reduction in the methicillin resistance level of the parental Staphylococcus aureus strain COL resulted in the isolation of mutant RUSA266 in which the minimal inhibitory concentration (MIC) of the parent was reduced from 1,600 to 1.5 micrograms/mL. Cloning and sequencing of the vicinity of the insertion site omega 726 identified an open reading frame (orf1365) encoding a very large polypeptide of more than 1,365 amino acids. A unique feature of the deduced amino acid sequence was the presence of multiple tandem repeats of 75 amino acids in the polypeptide, reminiscent of the structure of high-molecular-weight cell-surface proteins EF* and Emb identified in some streptococcal strains. Mutant RUSA266 with the inactivated gene, which we shall provisionally refer to as mrp (for multiple repeat polypeptide), produced a peptidoglycan with altered muropeptide composition, and both the reduced antibiotic resistance and the altered cell wall composition were co-transduced in back-crosses into the parental strain COL. Additional sequencing upstream of mrp has revealed that this gene was part of a five-gene cluster occupying a 9.2-kb region of the staphylococcal chromosome and was composed of glmM (directly upstream of mrp), two open reading frames orf310 and orf269 coding for two hypothetical proteins, and the gene encoding the staphylococcal arginase (arg). Transcriptional analysis demonstrated that the five genes in the cluster were transcribed together.

Characterization and nucleotide sequence of a Klebsiella oxytoca cryptic plasmid encoding a CMY-type beta-lactamase: confirmation that the plasmid-mediated cephamycinase originated from the Citrobacter freundii AmpC beta-lactamase

Plasmid pTKH11, originally obtained by electroporation of a Klebsiella oxytoca plasmid preparation into Escherichia coli XAC, expressed a high level of an AmpC-like beta-lactamase. The enzyme, designated CMY-5, conferred resistance to extended-spectrum beta-lactams in E. coli; nevertheless, the phenotype was cryptic in the K. oxytoca donor. Determination of the complete nucleotide sequence of pTKH11 revealed that the 8,193-bp plasmid encoded seven open reading frames, including that for the CMY-5 beta-lactamase (blaCMY-5). The blaCMY-5 product was similar to the plasmidic CMY-2 beta-lactamase of K. pneumoniae and the chromosomal AmpC of Citrobacter freundii, with 99.7 and 97.0% identities, respectively; there was a substitution of phenylalanine in CMY-5 for isoleucine 105 in CMY-2. blaCMY-5 was followed by the Blc and SugE genes of C. freundii, and this cluster exhibited a genetic organization identical to that of the ampC region on the chromosome of C. freundii; these results confirmed that C. freundii AmpC was the evolutionary origin of the plasmidic cephamycinases. In the K. oxytoca host, the copy number of pTKH11 was very low and the plasmid coexisted with plasmid pNBL63. Analysis of the replication regions of the two plasmids revealed 97% sequence similarity in the RNA I transcripts; this result implied that the two plasmids might be incompatible. Incompatibility of the two plasmids might explain the cryptic phenotype of blaCMY-5 in K. oxytoca through an exclusion effect on pTKH11 by resident plasmid pNBL63.

Genetic characterization of resistance to extended-spectrum beta-lactams in Klebsiella oxytoca isolates recovered from patients with septicemia at hospitals in the Stockholm area

Two beta-lactamase gene regions were characterized by DNA sequencing in eight clinical isolates of Klebsiella oxytoca. The blaOXY-2a region encoded a beta-lactamase nearly identical to OXY-2 (one amino acid residue substituted) and conferred aztreonam and cefuroxime resistance on the K. oxytoca isolates. Overproduction of OXY-2a was caused by a G-to-A substitution of the fifth nucleotide in the -10 consensus sequence of blaOXY-2a. The blaOXY-1a was identified in a susceptible strain, and the OXY-1a enzyme differed from OXY-1 by two amino acid residues.

Secondary lymphoid-tissue chemokine (SLC) stimulates integrin alpha 4 beta 7-mediated adhesion of lymphocytes to mucosal addressin cell adhesion molecule-1 (MAdCAM-1) under flow

The attachment of leukocytes to the endothelium is a multistep process that depends upon a very rapid increase in the adhesive activity of leukocyte integrins. A pertussis toxin-sensitive pathway stimulates integrin-dependent lymphocyte adhesion to Peyer's patch high endothelial venules in vivo, but the factors responsible for activating this pathway have not been identified previously. We now report that secondary lymphoid-tissue chemokine (SLC) (also known as 6Ckine, Exodus-2, and thymus-derived chemotactic agent 4), a recently described CC chemokine that is expressed in Peyer's patches and lymph nodes, rapidly activates integrin-mediated lymphocyte adhesion. Immobilized SLC increased the adhesion of HUT-78 T cells and human PBLs to mucosal addressin cell adhesion molecule-1, a protein that is expressed on Peyer's patch and mesenteric lymph node high endothelial venules. This effect of SLC was seen in both static and flow chamber adhesion assays, was mediated by integrin alpha 4 beta 7, and was inhibited by pertussis toxin. The other CC chemokines tested did not increase adhesion to mucosal addressin cell adhesion molecule-1. SLC had a greater effect on naive CD4+ T cells than on memory CD4+ T cells; CD8+ T cells, B cells, and NK cells were also responsive to SLC. SLC is likely to play an important role in regulating the recruitment of lymphocytes to Peyer's patches and lymph nodes.

Additive vector decoding of transform coded images

In a standard transform coding scheme of images or video, the decoder can be implemented by a table-lookup technique without the explicit use of an inverse transformation, In this new decoding method, each received code index of a transform coefficient addresses a particular codebook to fetch a component code vector that resembles the basis vector of the linear transformation. The output image is then reconstructed by summing a small number of nonzero component code vectors. With a set of well-designed codebooks, this new decoder can exploit the correlation among the quantized transform coefficients to achieve better rate-distortion performance than the conventional decoding method. An iterative algorithm for designing a set of locally optimal codebooks from a training set of images is presented. We demonstrate that this new idea can be applied to decode improved quality pictures from the bitstream generated from a standard encoding scheme of still images or video, while the complexity is low enough to justify practical implementation.

Structure-function analysis of the integrin beta 7 subunit: identification of domains involved in adhesion to MAdCAM-1

Beta 7 integrins serve special roles in mucosal immunity. Alpha 4 beta 7-mediated adhesion to mucosal addressin cell adhesion molecule-1 (MAdCAM-1) directs lymphocyte homing to the gut, and alpha E beta 7 mediates binding of lymphocytes to E-cadherin on epithelial cells. Since alpha 4 beta 7 mediates adhesion to MAdCAM-1 but alpha 4 beta 1 does not, we used beta 7/beta 1 chimeras to directly assess the importance of specific regions of beta 7 in MAdCAM-1 binding. We found a region of beta 7 (residues 46-386) that accounts for specificity of alpha 4 beta 7 binding to MAdCAM-1. We also used human/mouse and human/rat chimeric beta 7 subunits to map epitopes recognized by fifteen anti-beta 7 mAbs. Six of seven Abs that block adhesion to MAdCAM-1 and E-cadherin (Fib 21, 22, 27, 30, 504; Act-1) mapped to amino acid residues 176-250. Residues 176-250 lie within the region of beta 7 that specifies MAdCAM-1 binding and also within a region that has a predicted structure homologous to the metal ion-dependent adhesion site (MIDAS) domains of the integrin subunits alpha L and alpha M. Three new Abs that recognize beta 7 in the presence of Mn2+, but not Ca2+, and promote adhesion to MAdCAM-1, mapped to amino acids 46-149. One blocking and five other Abs mapped to other regions (amino acids 387-725). We conclude that a MIDAS-like domain serves a critical role in beta 7 integrin-mediated adhesion.

Structure-function analysis of the integrin beta 7 subunit: identification of domains involved in adhesion to MAdCAM-1

Beta 7 integrins serve special roles in mucosal immunity. Alpha 4 beta 7-mediated adhesion to mucosal addressin cell adhesion molecule-1 (MAdCAM-1) directs lymphocyte homing to the gut, and alpha E beta 7 mediates binding of lymphocytes to E-cadherin on epithelial cells. Since alpha 4 beta 7 mediates adhesion to MAdCAM-1 but alpha 4 beta 1 does not, we used beta 7/beta 1 chimeras to directly assess the importance of specific regions of beta 7 in MAdCAM-1 binding. We found a region of beta 7 (residues 46-386) that accounts for specificity of alpha 4 beta 7 binding to MAdCAM-1. We also used human/mouse and human/rat chimeric beta 7 subunits to map epitopes recognized by fifteen anti-beta 7 mAbs. Six of seven Abs that block adhesion to MAdCAM-1 and E-cadherin (Fib 21, 22, 27, 30, 504; Act-1) mapped to amino acid residues 176-250. Residues 176-250 lie within the region of beta 7 that specifies MAdCAM-1 binding and also within a region that has a predicted structure homologous to the metal ion-dependent adhesion site (MIDAS) domains of the integrin subunits alpha L and alpha M. Three new Abs that recognize beta 7 in the presence of Mn2+, but not Ca2+, and promote adhesion to MAdCAM-1, mapped to amino acids 46-149. One blocking and five other Abs mapped to other regions (amino acids 387-725). We conclude that a MIDAS-like domain serves a critical role in beta 7 integrin-mediated adhesion.

Site-specific RNase E cleavage of oligonucleotides and inhibition by stem-loops

The enzyme RNase E (ref. 1) cuts RNA at specific sites within single-stranded segments. The role of adjacent regions of secondary structure in such cleavages is controversial. Here we report that 10-13-nucleotide oligomers lacking any stem-loop but containing the RNase E-cleaved sequence of RNA I, the antisense repressor of replication of ColE1-type plasmids, are cut at the same phosphodiester bond as, and 20 times more efficiently than, RNA I. These findings indicate that, contrary to previous proposals, stem-loops do not serve as entry sites for RNase E, but instead limit cleavage at potentially susceptible sites. Cleavage was reduced further by mutations in a non-adjacent stem-loop, suggesting that distant conformational changes can also affect enzyme access. Modulation of RNase E cleavages by stem-loop regions and to a lesser extent by higher-order structure may explain why this enzyme, which does not have stringent sequence specificity, cleaves complex RNAs at a limited number of sites.

Joint estimation of forward and backward motion vectors for interpolative prediction of video

A low-complexity iterative algorithm is introduced for joint estimation of forward and backward motion vectors in interpolative prediction of video. Starting from the initial values obtained by a commonly-used block matching independent search method, the motion vectors are iteratively refined until a locally optimal solution to the motion estimation problem for interpolative prediction is achieved. Each iteration consists of a series of two similar procedures. First, the backward motion vector is fixed and a new forward motion vector is searched to minimize the interpolation error. Then the forward motion vector is fixed and the backward motion vector is similarly refined by minimizing the interpolation error. This process is repeated until the interpolation error stops decreasing. Computer simulation results demonstrate that with this technique the prediction error in some scenes is significantly reduced.

Extended spectrum beta-lactamase from Klebsiella oxytoca, not belonging to the TEM or SHV family

In clinical isolates of Klebsiella oxytoca resistance to cefuroxime and aztreonam was mediated by a beta-lactamase, designated KH, (pI 5.25) which could be transferred into Escherichia coli by electroporation, but not by conjugation. The transformants produced two enzymes with pIs 5.25 and 8.4 respectively, and showed resistance to cefuroxime, aztreonam, cefotaxime and ceftazidime. Substrate and inhibition profiles indicated that KH beta-lactamase was different from TEM- or SHV-like enzymes, but similar to chromosomal K1 beta-lactamase. The enzyme profile with pI 8.4 was similar to the enzyme from the recipient and showed elevated activity in transformants. The plasmid profiles of the transformants were different from those of their donors. However, a plasmid fragment of the K. oxytoca isolate KH11 hybridized with a plasmid ranging in size from 4.8 to 7.8 kilobases in all the transformants and most of the donors. Gene probes encoding TEM-1 or SHV-1 did not hybridize with plasmid DNA from the K. oxytoca isolates. Furthermore, a probe of the ampC gene did not hybridize with the plasmid but to DNA fragments of the same size in whole cell DNA preparations from the E. coli XAC recipient and the TKH11 transformants. This indicates that no gross rearrangements in the chromosomal beta-lactamase gene region had occurred in the transformants which could explain the increased expression of the pI 8.4 beta-lactamase.

Characterization of Klebsiella oxytoca septicaemia isolates resistant to aztreonam and cefuroxime

Eleven clinical isolates of Klebsiella oxytoca from Stockholm hospitals were found to be resistant to aztreonam and cefuroxime, but susceptible to cefotaxime, ceftazidime and imipenem. Resistance could be overcome by combining the beta-lactams with the inhibitor clavulanic acid. Crude beta-lactamase preparations from the isolates inactivated aztreonam and cefuroxime rapidly. By isoelectric focusing, a single common beta-lactamase of pI 5.25 was detected. The K. oxytoca isolates belonged to three subgroups, based on their plasmid profiles and Bg/II restriction endonuclease digestion of plasmid DNA. It was concluded that resistance to aztreonam and cefuroxime in these isolates was conferred by a beta-lactamase distinct from TEM-1, TEM-2 and SHV-1, but possibly derived from TEM-like enzymes.

Regulation of pyruvate kinase in Reuber H35 hepatoma cells by insulin and fructose

1. Kinetic and immunological studies as well as electrophoretic behaviour indicated that pyruvate kinase in Reuber H35 hepatoma cells is of the M2-type. 2. Addition of 0.1 microM insulin or 2 mM fructose to the incubation medium for 72 hr increased the activity of the M2-type pyruvate kinase in Reuber H35 hepatoma cells by 103 and 25% respectively. 3. Incorporation studies with [3H]leucine followed by immunoprecipitation showed that the apparent rate of synthesis of the M2-type pyruvate kinase was increased by both insulin and fructose. 4. Degradation studies indicated that the addition of insulin and fructose to the incubation medium increased the half-life of the M2-type pyruvate kinase from 4.8 to 8.6 and 6.8 hr respectively.

Studies on the regulation of hepatic pyruvate kinase synthesis in neonatal rats

The L- and M2-type pyruvate kinase from the liver of 1-day old rats demonstrated no significant activation nor inhibition by treatment with cyclic AMP, glucagon or insulin. Neither was there any change in their isozymic composition. By means of incorporation with [3H]leucine followed by immunoprecipitation, the rates of synthesis of both the L- and M2-type pyruvate kinase were not considerably affected by all three modulators. Insulin and glucagon do not direct an immediate change in the synthesis of liver pyruvate kinase and a fluctuation in the insulin/glucagon ratio is not a probable signal for regulating the isozymic expression in the neonatal period.

Biosynthesis of pyruvate kinase isozymes in rat liver

1. The L and M1 isozymes of pyruvate kinase were purified to homogeneity from rat liver and muscle respectively and their specific antibodies were employed to quantify the isozyme concentration in rat liver during development. 2. Total enzyme activity decreases towards birth and reaches a minimum on the 3rd postnatal day, but the activity increases dramatically after weaning. 3. Immunoprecipitation revealed that the M2 type predominates in the prenatal period but decreases sharply just before birth. 4. The L isozyme contribution is augmented upon weaning and is sustained until the rat is adult and a L/M ratio of 9:1 is maintained. 5. By means of incorporation studies with [3H]leucine followed by immunoprecipitation, the increase in L-type activity when approaching term and after weaning is explained by a twofold increase in its rate of synthesis coupled with a concomitant reduction of the M2-type synthesis.