Non-invasive cell-free DNA prenatal screening for trisomy 21 as part of primary screening strategy in twin pregnancies.

OBJECTIVES: The performance of non-invasive prenatal screening using cell-free DNA testing in maternal blood in twin pregnancies is still under-evaluated, while serum marker-based strategies yield poor results. This study aims at assessing the performance of non-invasive prenatal screening for trisomy 21 in twin pregnancies as a first-tier test. The secondary objectives were to assess the failure rate and associated factors. METHODS: This retrospective cohort study included twin pregnancies for which non-invasive prenatal screening using cell-free DNA was performed as the primary screening strategy between May 2017 and October 2019. We used the NIPT VeriSeq® test for in vitro diagnosis and set a fetal fraction cut-off of 4% for monochorionic pregnancies and 8% for dichorionic ones. Clinical data and pregnancy outcome was collected from either physicians or midwives through a questionnaire or were retrieved directly on site. We calculated the performance of non-invasive cell free DNA screening for trisomy 21 and analyzed failure rate and factors. RESULTS: We included 2577 multiple pregnancies among which 1885 (84.8%) were retained after excluding vanishing twins and pregnancies without follow-up. Overall, there were six confirmed trisomy 21 cases (0.32%). For trisomy 21, sensitivity was 100% (95% CI, 61-100%) and the false-positive rate 0.2% (95% CI, 0.07-0.6%). The primary failure rate was 4.6% with 4% due to insufficient fetal fraction. After a new blood draw (59.8% of failed cases), failure rate was only 1.5%. Body mass index and chorionicity were significantly correlated with the risk of failure. CONCLUSION: This study adds further evidence on the high performance of NIPS in twins, as part of the primary screening strategy for trisomy 21, at an extremely low false-positive rate. This article is protected by copyright. All rights reserved.

Mechanical stretch triggers rapid epithelial cell division through Piezo1.

Despite acting as a barrier for the organs they encase, epithelial cells turn over at some of the fastest rates in the body. However, epithelial cell division must be tightly linked to cell death to preserve barrier function and prevent tumour formation. How does the number of dying cells match those dividing to maintain constant numbers? When epithelial cells become too crowded, they activate the stretch-activated channel Piezo1 to trigger extrusion of cells that later die. However, it is unclear how epithelial cell division is controlled to balance cell death at the steady state. Here we show that mammalian epithelial cell division occurs in regions of low cell density where cells are stretched. By experimentally stretching epithelia, we find that mechanical stretch itself rapidly stimulates cell division through activation of the Piezo1 channel. To stimulate cell division, stretch triggers cells that are paused in early G2 phase to activate calcium-dependent phosphorylation of ERK1/2, thereby activating the cyclin B transcription that is necessary to drive cells into mitosis. Although both epithelial cell division and cell extrusion require Piezo1 at the steady state, the type of mechanical force controls the outcome: stretch induces cell division, whereas crowding induces extrusion. How Piezo1-dependent calcium transients activate two opposing processes may depend on where and how Piezo1 is activated, as it accumulates in different subcellular sites with increasing cell density. In sparse epithelial regions in which cells divide, Piezo1 localizes to the plasma membrane and cytoplasm, whereas in dense regions in which cells extrude, it forms large cytoplasmic aggregates. Because Piezo1 senses both mechanical crowding and stretch, it may act as a homeostatic sensor to control epithelial cell numbers, triggering extrusion and apoptosis in crowded regions and cell division in sparse regions.

Prenatal stomach position predicts gastrointestinal morbidity at 2 years in fetuses with left-sided congenital diaphragmatic hernia.

OBJECTIVE: The long-term morbidity associated with isolated left-sided congenital diaphragmatic hernia (CDH) has been described previously. However, antenatal criteria impacting gastrointestinal morbidity (GIM) are not yet defined. The objective of this study was to evaluate the effect of fetal stomach position on the risk of GIM at 2 years of age in children with left-sided CDH. METHODS: This was a retrospective, observational multicenter cohort study of data obtained from January 2010 to January 2014, that included patients whose fetus had isolated left-sided CDH, with or without fetal endoscopic tracheal occlusion (FETO). Prenatal maternal, fetal and pediatric data were collected. Fetal stomach position was evaluated a posteriori by two observers, using ultrasound images at the level of the four-chamber view of the heart that had been obtained to calculate the observed-to-expected lung-area-to-head-circumference ratio (O/E-LHR). Fetal stomach position was graded as follows: Grade 1, stomach not visualized; Grade 2, stomach visualized anteriorly, next to the apex of the heart, with no structure in between the stomach and the sternum; Grade 3, stomach visualized alongside the left ventricle of the heart, and abdominal structures anteriorly; or Grade 4, as Grade 3 but with stomach posterior to the level of the atrioventricular heart valves. The primary outcome was GIM at 2 years of age, assessed in a composite manner, including the occurrence of gastroesophageal reflux disease, need for gastrostomy, duration of parenteral and enteral nutrition and persistence of oral aversion. Regression analysis was performed in order to investigate the effect of O/E-LHR, stomach position and FETO on various GIM outcome variables. RESULTS: Forty-seven patients with fetal left-sided CDH were included in the analysis. Thirteen (27.7%) infants did not meet the criterion of exclusive oral feeding at 2 years of age. Fetal stomach position grade was associated significantly and independently with the duration of parenteral nutrition (odds ratio (OR), 19.86; P = 0.031) and persistence of oral aversion at 2 years (OR, 3.40; P = 0.006). On multivariate analysis, O/E-LHR was predictive of the need for prosthetic patch repair, but not for GIM. FETO did not seem to affect the risk of GIM at 2 years. CONCLUSION: In isolated left-sided CDH, fetal stomach position is the only factor that is predictive of GIM at 2 years of age. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

Prognostic value of diffusion-weighted magnetic resonance imaging of brain in fetal growth restriction: results of prospective multicenter study.

OBJECTIVE: To measure prospectively apparent diffusion coefficient (ADC) values between 28 and 32 weeks of gestation in different cerebral territories of fetuses with estimated fetal weight (EFW) ≤ 5th centile, and analyze their association with adverse perinatal outcome. METHODS: This was a prospective study involving six tertiary-level perinatal centers. In the period 22 November 2016 to 11 September 2017, we included singleton, small-for-gestational-age (SGA) fetuses with EFW ≤ 5th percentile, between 28 and 32 weeks of gestation, regardless of the umbilical artery Doppler and maternal uterine artery Doppler findings. A fetal magnetic resonance imaging (MRI) examination with diffusion-weighted sequences (DWI) was performed within 14 days following inclusion and before 32 weeks. ADC values were calculated in the frontal and occipital white matter, basal ganglia and cerebellar hemispheres. An ultrasound examination was performed within 1 week prior to the MRI examination. The primary outcome was a composite measure of adverse perinatal outcome, defined as any of the following: perinatal death; admission to neonatal intensive care unit with mechanical ventilation > 48 h; necrotizing enterocolitis; Grade III-IV intraventricular hemorrhage; periventricular leukomalacia. A univariate comparison of median ADC values in all cerebral territories between fetuses with and those without adverse perinatal outcome was performed. The association between ADC values and adverse perinatal outcome was then analyzed using multilevel logistic regression models to adjust for other common prognostic factors for growth-restricted fetuses. RESULTS: MRI was performed in 64 patients, of whom five were excluded owing to fetal movement artifacts on DWI and two were excluded for termination of pregnancy with no link to fetal growth restriction (FGR). One intrauterine death occurred secondary to severe FGR. Among the 56 liveborn neonates, delivered at a mean ± SD gestational age of 33.6 ± 3.0 weeks, with a mean birth weight of 1441 ± 566 g, four neonatal deaths occurred. In addition, two neonates required prolonged mechanical ventilation, one of whom also developed necrotizing enterocolitis. Overall, therefore, seven out of 57 (12.3%) cases had an adverse perinatal outcome (95% CI, 3.8-20.8%). The ADC values in the frontal region were significantly lower in the group with adverse perinatal outcome vs those in the group with favorable outcome (mean values of both hemispheres, 1.68 vs 1.78 × 10-3 mm2 /s; P = 0.04). No significant difference in ADC values was observed between the two groups in any other cerebral territory. A cut-off value of 1.70 × 10-3 mm2 /s was associated with a sensitivity of 57% (95% CI, 18-90%), a specificity of 78% (95% CI, 63-88%), a positive predictive value of 27% (95% CI, 8-55%) and a negative predictive value of 93% (95% CI, 80-98%) for the prediction of adverse perinatal outcome. A mean frontal ADC value < 1.70 × 10-3 mm2 /s was not associated significantly with an increased risk of adverse perinatal outcome, either in the univariate analysis (P = 0.07), or when adjusting for gestational age at MRI and fetal sex (odds ratio (OR), 6.06 (95% CI, 0.9-37.1), P = 0.051) or for umbilical artery Doppler (OR, 6.08 (95% CI, 0.89-41.44)). CONCLUSION: This first prospective, multicenter, cohort study using DWI in the setting of SGA found lower ADC values in the frontal white-matter territory in fetuses with, compared with those without, adverse perinatal outcome. To determine the prognostic value of these changes, further standardized evaluation of the neurodevelopment of children born with growth restriction is required. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Prenatal natural history of congenital pulmonary malformations: MALFPULM population-based cohort study.

OBJECTIVES: To assess prenatal changes in the volume of congenital pulmonary malformations (CPM) and examine whether these changes differ in lesions that appear cystic on ultrasound compared with hyperechoic lesions, and to study the relationship between CPM volume and risk of fetal compression. METHODS: We conducted a nationally representative, multicenter, prospective cohort study, which included 579 ultrasound examinations in 176 pregnant women with a diagnosis of fetal CPM, between March 2015 and November 2016. Several ultrasound examinations were performed between diagnosis and delivery, including measurement of CPM volume. We modeled changes in CPM volume ratio (CVR) as a function of gestational age, overall and for cystic/mixed vs hyperechoic malformations, and examined the association between CVR and signs of compression during pregnancy. RESULTS: When modeling CVR changes over time, there was a statistically significant decrease in CVR with increasing gestational age (P < 0.001), but the pattern of change differed according to CPM phenotype at first ultrasound examination: cystic/mixed CPM were characterized by a monotonic decrease in CVR with increasing gestational age (P = 0.002), whereas hyperechoic CPM showed an initial increase in CVR up to 27 weeks of gestation, followed by a decrease thereafter (P < 0.001). Peak CVR values were predicted as early as 21-22 weeks for cystic/mixed CPMs compared with 25-26 weeks for hyperechoic malformations. Regardless of CPM phenotype, fetuses that showed no sign of compression at any point had substantially lower CVR at first CVR measurement, and the CVR remained relatively constant thereafter. Among the subpopulation of fetuses with no sign of compression at first CVR measurement, the odds of a subsequent compression was 7-fold higher (adjusted odds ratio, 7.0; 95% CI, 1.6-29.9) if initial CVR was > 0.4 vs CVR ≤ 0.4 cm2 . CONCLUSIONS: Predicted changes in CVR during pregnancy differ between cystic and hyperechoic malformations. This may be the result of different pathophysiological mechanisms or differences in the timing of occurrence of these different types of CPM. CVR measured at the initial diagnostic ultrasound examination was strongly associated with the odds of subsequent compression. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

Diffusion-weighted magnetic resonance imaging of the fetal brain in intrauterine growth restriction.

OBJECTIVE: Diffusion-weighted magnetic resonance imaging (DWI) is a sensitive method for assessing brain maturation and detecting brain lesions, providing apparent diffusion coefficient (ADC) values as a measure of water diffusion. Abnormal ADC values are seen in ischemic brain lesions, such as those associated with acute or chronic hypoxia. The aim of this study was to assess whether ADC values in the fetal brain were different in fetuses with severe intrauterine growth restriction (IUGR) compared with normal controls. METHODS: Brain magnetic resonance imaging (MRI) with single-shot axial DWI (b = 0 and b = 700 s/mm2 ) was performed in 30 fetuses with severe IUGR (estimated fetal weight < 3rd centile with absent or reversed umbilical artery Doppler flow) and in 24 normal controls of similar gestational age. Brain morphology and biometry were analyzed. ADC values were measured in frontal and occipital white matter, centrum semiovale, thalami, cerebellar hemisphere and pons. Frontal-occipital and frontal-cerebellar ADC ratios were calculated, and values were compared between IUGR fetuses and controls. RESULTS: There was no difference in gestational age at MRI between IUGR and control fetuses (IUGR, 30.2 ± 1.6 weeks vs controls, 30.7 ± 1.4 weeks). Fetal brain morphology and signals were normal in all fetuses. Brain dimensions (supratentorial ± infratentorial) were decreased (Z-score, < -2) in 20 (66.7%) IUGR fetuses. Compared with controls, IUGR fetuses had significantly lower ADC values in frontal white matter (1.97 ± 0.23 vs 2.17 ± 0.22 × 10-3 mm2 /s; P < 0.0001), thalami (1.04 ± 0.15 vs 1.13 ± 0.10 ×10-3 mm2 /s; P = 0.0002), centrum semiovale (1.86 ± 0.22 vs 1.97 ± 0.23 ×10-3 mm2 /s; P = 0.01) and pons (0.85 ± 0.19 vs 0.94 ± 0.12 ×10-3 mm2 /s; P = 0.043). IUGR fetuses had a lower frontal-occipital ADC ratio than did normal fetuses (1.00 ± 0.11 vs 1.08 ± 0.05; P = 0.003). CONCLUSIONS: ADC values in IUGR fetuses were significantly lower than in normal controls in the frontal white matter, thalami, centrum semiovale and pons, suggesting abnormal maturation in these regions. However, the prognostic value of these ADC changes is still unknown. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Glyceryl trinitrate and caprylic acid for the mitigation of the Desulfovibrio vulgaris biofilm on C1018 carbon steel.

Microbiologically influenced corrosion (MIC), also known as biocorrosion, is caused by corrosive biofilms. MIC is a growing problem, especially in the oil and gas industry. Among various corrosive microbes, sulfate reducing bacteria (SRB) are often the leading culprit. Biofilm mitigation is the key to MIC mitigation. Biocide applications against biofilms promote resistance over time. Thus, it is imperative to develop new biodegradable and cost-effective biocides for large-scale field applications. Using the corrosive Desulfovibrio vulgaris (an SRB) biofilm as a model biofilm, this work demonstrated that a cocktail of glyceryl trinitrate (GTN) and caprylic acid (CA) was very effective for biofilm prevention and mitigation of established biofilms on C1018 carbon steel coupons. The most probable number sessile cell count data and confocal laser scanning microscope biofilm images proved that the biocide cocktail of 25 ppm (w/w) GTN + 0.1% (w/w) CA successfully prevented the D. vulgaris biofilm establishment on C1018 carbon steel coupons while 100 ppm GTN + 0.1% CA effectively mitigated pre-established D. vulgaris biofilms on C1018 carbon steel coupons. In both cases, the cocktails were able to reduce the sessile cell count from 10(6) cells/cm(2) to an undetectable level.

Fetal urine biochemistry at 13-23 weeks of gestation in lower urinary tract obstruction: criteria for in-utero treatment.

OBJECTIVES: To assess the value of fetal urine biochemistry before 23 weeks of gestation in cases of lower urinary tract obstruction (LUTO) to refine prognosis and to select potential candidates for in-utero intervention. METHODS: This was a retrospective study including 72 cases of LUTO with fetal urine sampled before 23 weeks and assayed for total protein, ß-2-microglobulin, sodium, chloride, calcium, phosphorus, glucose and gamma-glutamyl transpeptidase (GGTP). Two groups were defined according to renal outcome: 1) bilateral renal dysplasia on histological examination or renal failure at birth; 2) normal postnatal renal function or histologically normal appearance of the kidneys. Correlations between fetal urinary biochemical markers and postnatal renal function were studied. RESULTS: LUTO was isolated in 56/72 (77.8%) cases and was associated with other malformations in 16/72 (22.2%) cases. High GGTP levels (236 IU/L vs 5 IU/L; P < 0.0001) were observed in fetal urine in the five cases of urodigestive fistula. A significant difference between outcome groups was observed for ß-2-microglobulin (P = 0.0017), sodium (P = 0.0008), chloride (P = 0.0028) and calcium (P = 0.0092) but not for protein, glucose or phosphorus. Sensitivity and specificity in defining a poor renal prognosis were 80.6% and 89% for ß-2-microglobulin, 61.3% and 100% for sodium and 64.5% and 100% for calcium, respectively. CONCLUSIONS: Fetal urinalysis before 23 weeks of gestation allowed distinction between three groups: 1) fetuses with normal urine biochemistry for which fetal therapy should be discussed; 2) fetuses with abnormal urine biochemistry for which prognosis for renal outcome is poor and for which the benefit of fetal therapy is likely to be compromised; 3) fetuses with urodigestive fistula.

Selective correlations; not voodoo.

The problem of "voodoo" correlations-exceptionally high observed correlations in selected regions of the brain-is well recognized in neuroimaging. It arises when quantities of interest are estimated from the same data that was used to select them as interesting. In statistical terminology, the problem of inference following selection from the same data is that of selective inference. Motivated by the unwelcome side-effects of splitting the data- the recommended remedy-we adapt the recent developments in selective inference in order to construct confidence intervals (CIs) with good reproducibility prospects, even if selection and estimation are done with the same data. These intervals control the expected proportion of non-covered correlations in the selected voxels-the False Coverage Rate (FCR). They extend further toward zero than standard intervals, thus attenuating the impression made by highly biased observed correlations. They do so adaptively, in that they coincide with the standard CIs when far away from the selection point. We complement existing analytic proofs with a simulation, showing that the proposed intervals control the FCR in realistic social neuroscience problems. We also suggest a "confidence calibration plot", to allow the intervals to be reported in a clear and interpretable way. Applying the proposed methodology on a loss-aversion study, we demonstrate that with the sample size and selection type employed, selection bias is considerable. Finally, selective intervals are compared to the currently recommended data-splitting approach. We discover that our approach has more power and typically more informative, as no data is discarded. Computation of the intervals is implemented in an accompanying software package.

Revisiting multi-subject random effects in fMRI: advocating prevalence estimation.

Random effect analysis has been introduced into fMRI research in order to generalize findings from the study group to the whole population. Generalizing findings is obviously harder than detecting activation within the study group since in order to be significant, an activation has to be larger than the inter-subject variability. Indeed, detected regions are smaller when using random effect analysis versus fixed effects. The statistical assumptions behind the classic random effect model are that the effect in each location is normally distributed over subjects, and "activation" refers to a non-null mean effect. We argue that this model is unrealistic compared to the true population variability, where due to function-anatomy inconsistencies and registration anomalies, some of the subjects are active and some are not at each brain location. We propose a Gaussian-mixture-random-effect that amortizes between-subject spatial disagreement and quantifies it using the prevalence of activation at each location. We present a formal definition and an estimation procedure of this prevalence. The end result of the proposed analysis is a map of the prevalence at locations with significant activation, highlighting activation regions that are common over many brains. Prevalence estimation has several desirable properties: (a) It is more informative than the typical active/inactive paradigm. (b) In contrast to the usual display of p-values in activated regions - which trivially converge to 0 for large sample sizes - prevalence estimates converge to the true prevalence.

Chelator-based catheter lock solutions in eradicating organisms in biofilm.

Two different chelator-based antimicrobial catheter lock solutions, methylene blue-citrate-parabens (MB-CIT) and minocycline-EDTA-25% ethanol (M-EDTA-25% ETOH), were compared in 2-h biofilm eradication experiments. Eradication of both mature and immature Gram-positive, Gram-negative, and fungal biofilms was assessed. M-EDTA-25% ETOH was able to fully eradicate all biofilms within 2 h. MB-CIT was only effective against immature biofilms but was unable to fully eradicate most of the mature biofilms tested.

Impact of prenatal estimation of the risk of respiratory distress in neonates with congenital pulmonary malformations on the choice of delivery site.

BACKGROUND: The vast majority of prenatally diagnosed congenital pulmonary malformations (CPM) remain asymptomatic at birth. The maximal value of the CPM volume ratio (CVRmax) predicts the risk of neonatal respiratory distress (NRD), and should allow for better assessment of the level of expertise needed at the delivery site. AIM: This study evaluated the level of maternity units currently chosen for the delivery of CPMs, and determined the impact of the choice of delivery site based on the CVRmax, with a threshold of 0.4 cm2. METHODS: Data were extracted from the French prospective MALFPULM cohort, with inclusion between March 2015 and June 2018. RESULTS: The final study population consisted of 383 women. Deliveries in level 1 or 2 maternity units (n = 98, 25%) involved CPMs with lower CVRmax (p<0.001), causing fewer signs of prenatal compression (p = 0.025). Among the 62 children (16%) who presented with NRD, only seven (11%) were born in level 1 or 2 units (p = 0.0078). Choosing the maternity level according to the CVRmax would have increased the number of births in level 1 or 2 maternity hospitals by 70%. In these maternity units, the percentage of children with NRD would have increased from 8% in the actual distribution to 10% in the new strategy. CONCLUSION: Our results showed an overuse of level 3 maternity hospitals for the delivery of newborns with a prenatal diagnosis of CPM. The use of CVRmax should enable a reduction in the use of expertise centers without an adverse impact on newborns.

Actin dynamics in vivo.

Actin dynamics in lamellipodia are driven by continuous cycles of actin polymerization, retrograde flow, and depolymerization. In the past year, advances have been made in identifying signaling pathways that regulate actin-filament uncapping and polymerization, in determining the role of myosin motor proteins in retrograde flow, and in evaluating the role of severing proteins in actin depolymerization. Both Listeria monocytogenes and Saccharomyces cerevisiae have emerged as powerful model organisms for studying actin dynamics in cells.

Visualization of intracranial translucency at the 11-13-week scan is improved after specific training.

OBJECTIVE: To evaluate the ability to confidently identify intracranial translucency (IT) in a clinical practice and following specific training of 10 operators. METHODS: Two experienced observers reviewed 11-13-week nuchal translucency (NT) images for IT visibility in (1) a series of 50 randomly selected images obtained by 10 skilled operators certified by the Collège Français d'Echographie Foetale (CFEF) (retrospective analysis) and (2) a series of 315 images obtained by 10 different operators following specific training for IT visualization (prospective analysis). We calculated proportions of images for which IT was deemed visible and the agreement between the two observers. Data were also stratified by Herman and CFEF quality-score intervals. RESULTS: In the retrospective analysis, IT was visualized by both reviewers in 52% of images, with a moderate level of agreement (κ = 0.63). The rate of IT visualization by both reviewers increased very slightly to 56-58% when only considering images with the best NT quality-control scores. Following specific training of the operators the proportion of images for which both reviewers could identify the fourth ventricle increased to 85%, but the level of agreement remained moderate (κ = 0.66). When considering images with the best NT quality-control scores, IT visualization by both reviewers increased to 91-92%. CONCLUSIONS: In a clinical practice that focuses on NT measurement IT cannot be visualized in a substantial proportion of the images obtained, which limits the utility of this approach for the early prenatal diagnosis of open spina bifida. However, the ability to identify the fourth ventricle significantly increases following specific training.

Update on resistance of Bacteroides fragilis group and related species with special attention to carbapenems 2006-2009.

The susceptibility trends for the species of the Bacteroides fragilis group against various antibiotics were determined using data from 4 years [2006-2009] on 1957 isolates referred by 8 medical centers participating in a National Survey for the Susceptibility of B. fragilis. The antibiotic test panel included doripenem, ertapenem, imipenem, meropenem, ampicillin:sulbactam, piperacillin:tazobactam, cefoxitin, clindamycin, moxifloxacin, tigecycline, chloramphenicol and metronidazole. MICs were determined using agar dilution methods following CLSI recommendations. Genetic analysis of isolates from 2008 with elevated MICs (>2 µg/mL) to one or more of the carbapenems to detect presence of the cfiA gene was performed using PCR methodology. The results showed an increase in the resistance rates to the ß-lactam antibiotics. High resistance rates were seen for clindamycin and moxifloxacin (as high as 60% for clindamycin and >80% for moxifloxacin), with relatively stable low resistance (5.4%) for tigecycline. For carbapenems, resistance in B. fragilis was 1.1%-2.5% in 2008-9. One isolate resistant to metronidazole (MIC 32 µg/mL) was observed as well as isolates with elevated MICs to chloramphenicol (16 µg/mL). Genetic analysis indicated that the cfiA gene was present in some but not all of the isolates with high MICs to the carbapenems. These data indicate that there continue to be changes in susceptibility over time, and that resistance can be seen among the carbapenems. High antibiotic resistance rates tend to be associated with specific species.

Xenopus actin depolymerizing factor/cofilin (XAC) is responsible for the turnover of actin filaments in Listeria monocytogenes tails.

In contrast to the slow rate of depolymerization of pure actin in vitro, populations of actin filaments in vivo turn over rapidly. Therefore, the rate of actin depolymerization must be accelerated by one or more factors in the cell. Since the actin dynamics in Listeria monocytogenes tails bear many similarities to those in the lamellipodia of moving cells, we have used Listeria as a model system to isolate factors required for regulating the rapid actin filament turnover involved in cell migration. Using a cell-free Xenopus egg extract system to reproduce the Listeria movement seen in a cell, we depleted candidate depolymerizing proteins and analyzed the effect that their removal had on the morphology of Listeria tails. Immunodepletion of Xenopus actin depolymerizing factor (ADF)/cofilin (XAC) from Xenopus egg extracts resulted in Listeria tails that were approximately five times longer than the tails from undepleted extracts. Depletion of XAC did not affect the tail assembly rate, suggesting that the increased tail length was caused by an inhibition of actin filament depolymerization. Immunodepletion of Xenopus gelsolin had no effect on either tail length or assembly rate. Addition of recombinant wild-type XAC or chick ADF protein to XAC-depleted extracts restored the tail length to that of control extracts, while addition of mutant ADF S3E that mimics the phosphorylated, inactive form of ADF did not reduce the tail length. Addition of excess wild-type XAC to Xenopus egg extracts reduced the length of Listeria tails to a limited extent. These observations show that XAC but not gelsolin is essential for depolymerizing actin filaments that rapidly turn over in Xenopus extracts. We also show that while the depolymerizing activities of XAC and Xenopus extract are effective at depolymerizing normal filaments containing ADP, they are unable to completely depolymerize actin filaments containing AMPPNP, a slowly hydrolyzible ATP analog. This observation suggests that the substrate for XAC is the ADP-bound subunit of actin and that the lifetime of a filament is controlled by its nucleotide content.

A purified Drosophila septin complex forms filaments and exhibits GTPase activity.

Septin proteins are necessary for cytokinesis in budding yeast and Drosophila and are thought to be the subunits of the yeast neck filaments. To test whether septins actually form filaments, an immunoaffinity approach was used to isolate a septin complex from Drosophila embryos. The purified complex is comprised of the three previously identified septin polypeptides Pnut, Sep2, and Sep1. Hydrodynamic and sequence data suggest that the complex is composed of a heterotrimer of homodimers. The complex copurifies with one molecule of bound guanine nucleotide per septin polypeptide. It binds and hydrolyzes exogenously added GTP. These observations together with conserved sequence motifs identify the septins as members of the GTPase superfamily. We discuss a model of filament structure and speculate as to how the filaments are organized within cells.

Nonhormonal basis of maternal behavior in the rat.

Rats were tested for induction of maternal behavior by exposing them to young pups continously for 10 to 15 days. Nonpregnant intact, ovariecto-mized. and hypophysectomized females were studied, as well as intact and castrated males. Nearly all the animals exhibited the four main items of maternal behavior and there were only minor differences in the latencies for the onset of maternal behavior among the various groups. It is concluded that all rats have a basic level of maternal responsiveness which is independent of hormonal stimulation.

Mammary glands of pregnant rats: development stimulated by licking.

At the end of gestation, the mamnmary glands of pregnant rats that have been prevented from licking their ventral surfaces by neck collars are about 50-percent less developed than those of control animals. Neither the burden nor the stress ejfect of the collar is an alternative explanation. A considerable proportion of mammary development during pregnancy is thus caused by the female's own licking.

Randomization and the draft lottery.

Fifty "random permutations" were prepared for use by the Selective Service System as a basis for a two-stage randomization that preceded the lottery drawing on 1 July 1970. This report identifies the permutations used. It also gives the orders in which calendar dates and numbers were put into and drawn from two drums and the correlations between them.