Fetal Thymus Size at 19-22 Weeks of Gestation: A Possible Marker for the Prediction of Low Birth Weight?

INTRODUCTION

The purpose was to compare thymus size measured during second trimester screening of fetuses who were subsequently small for gestational age at birth (weight below 10th percentile, SGA group) with fetuses with normal birth weight (control group). We hypothesized that measuring the fetal thymic-thoracic ratio (TT-ratio) might help predict low birth weight.

METHODS

Using three-vessel view echocardiograms from our archives, we measured the anteroposterior thymus size and the intrathoracic mediastinal diameter to derive TT-ratios in the SGA (n = 105) and control groups (n = 533) between 19+0 and 21+6 weeks of gestation. We analyzed the association between TT-ratio and SGA adjusted to the week of gestation using logistic regression. Finally, we determined the possible TT-ratio cut-off point for discrimination between SGA and control groups by means of receiver operating characteristics (ROC) curve analysis.

RESULTS

The TT-ratio was significantly higher in the SGA group than in the control group (p < 0.001). An increase of the TT-ratio by 0.1 was associated with a 3.1-fold increase in the odds of diagnosing SGA. We determined that a possible discrimination cut-off point between SGA and healthy controls was achieved using a TT-ratio of 0.390 (area under the ROC curve 0.695).

CONCLUSION

An increased TT-ratio may represent an additional prenatal screening parameter that improves the prediction of birth weight below the 10th percentile. Prospective studies are now needed to evaluate the use of fetal thymus size as predictive parameter for adverse fetal outcome.

Termination of pregnancy in the second trimester - the course of different therapy regimens

OBJECTIVES

To compare two prostaglandin analogs and two application intervals between mifepristone and the prostaglandin analog administration on the time to abortion in second trimester termination of pregnancy. Other endpoints were live birth rate and fetal lifetime after expulsion.

METHODS

Retrospective data of 373 abortions performed were evaluated. Four medical induction subgroups and two feticide subgroups were considered. The definition criteria of the subgroups were the choice of administered prostaglandin analog (misoprostol vs. sulprostone) and the time interval between mifepristone and prostaglandin analog administration (48 vs. 24 h). The outcome parameters were the time to complete uterine evacuation (TCUE), the live birth rate and duration of fetal life.

RESULTS

In the misoprostol subgroups, the median TCUE was 1.6 h longer in the 24-h group than in the 48-h group (p=0.950). In the sulprostone subgroups, the median TCUE was 1.9 h shorter in the 24-h group than in the 48-h group (p=0.950). The median TCUE was shorter for sulprostone than for misoprostol in all six subgroups (p<0.001). The rate of fetal live births ranged between 13.6 and 15.9% within the medical induction subgroups (p=0.969). The median fetal lifetime was slightly shorter in the sulprostone groups than in the misoprostol groups (p=0.563).

CONCLUSIONS

Both application intervals and prostaglandin analogs are similarly effective. The therapy regime should be adapted to the personal preferences of the woman, the situational and clinical conditions.

O-184 The impact of cryopreserved sperm on Intrauterine Insemination (IUI) outcomes: Is frozen as good as fresh?

Study question

Are the outcomes of IUI cycles [with or without ovarian stimulation (OS)] comparable when frozen instead of fresh-ejaculated sperm is utilized?

Summary answer

Overall, clinical outcomes did not differ significantly between frozen and fresh sperm IUI cycles, although specific subgroups might benefit from fresh sperm utilization.

What is known already

At present, data from animal studies point towards less favorable outcomes with frozen sperm utilization, implicating cryopreservation-induced damages to the cytoskeleton, DNA, and acrosome leading to adverse effects on spermatozoa’s motility, viability, and ability to fuse with the oocyte. Assisted Reproductive Technology (ART) data, mostly focusing on severe male factor infertility diagnoses, suggest no major differences between in-vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) cycles utilizing frozen over fresh sperm, often surgically extracted. Nevertheless, contemporary data from IUI(±OS) cycles are still scarce.

Study design, size, duration

Data from 5335 IUI(±OS) cycles (time-period: 01/2004-12/2021) from a large academic fertility center were retrospectively reviewed. Cycles were stratified in two groups based on utilization of frozen instead of fresh-ejaculated sperm for the IUI [FROZEN (n = 1871, all infertility diagnoses), and FRESH (n = 3464, idiopathic infertility diagnosis only), respectively]. Cycle outcomes were compared between groups.

Participants/materials, setting, methods

Participants: women seeking IUI (±OS) treatments.

Outcome Measures: HCG-positivity, clinical pregnancy (CP), spontaneous abortion (SAB) rates. Initial analysis included all cycles irrespective of OS regimen.  Cycles were then stratified by OS regimen into three subgroups [injectable gonadotropins, oral medications (OM): clomiphene-citrate and letrozole, and unstimulated/natural]. Odds ratios (OR) for all relevant outcomes were calculated utilizing logistic regression and adjusted for maternal age, day-3 FSH, and OS regimen. Time-to-pregnancy and first-cycle only analyses were also performed.

Main results and the role of chance

Unadjusted HCG-positivity, and CP were lower in the FROZEN compared to the FRESH group (12.2% vs. 15.6%, p &lt; 0.001; 9.4% vs. 13.0%, p&lt;.001, respectively), which persisted only among OM after stratification (9.9% vs. 14.2% HCG-positivity, p=.030; 8.1% vs. 11.8% CPR, p=.041, for FROZEN compared to FRESH, respectively).

Among all cycles, adjOR(95%CI) for HCG-positivity and CP were respectively: 0.75(0.56-1.02), and 0.77(0.57-1.03), ref: FRESH). Following stratification by OS regimen, adjOR(95%CI) for HCG-positivity and CP showed no difference between groups among gonadotropin and natural cycles but favored the FRESH group in OM cycles [HCG-positivity: 0.55(0.30-0.99); CP: 0.49(0.25-0.95), ref.: FRESH]. SAB odds did not differ between groups among OM and natural cycles but were lower in the FROZEN compared to FRESH group among gonadotropin cycles [adjOR(95%CI): 0.13(0.02-0.98), ref.: FRESH]. However, regarding the latter comparison, numbers were small and the 95%CI wide.  When analysis was limited to first-cycles only and further stratified by OS regimen, the previously noted differences in CP and SAB odds no longer existed within the OS subgroups.

Nevetheless, time-to-conception was slightly longer in the FROZEN compared to the FRESH group (3.84 vs. 2.58 cycles, p&lt;.001).

Limitations, reasons for caution

Study is limited by its retrospective nature. The two groups differed somewhat in age, infertility diagnosis, utilized OS regimen, and as expected in total motile sperm counts. Despite the less favorable characteristics of the FROZEN group, no detrimental effect of sperm cryopreservation on IUI outcomes was noted.

Wider implications of the findings

Our study, the largest to date, showed no significant difference in IUI outcomes between cycles utilizing frozen instead of fresh-ejaculated sperm. Although, specific subgroups might benefit from fresh sperm utilization and time-to-pregnancy might be shorter with fresh over frozen sperm, patients should be counselled about the non-inferiority of frozen sperm.

Trial registration number

Not applicable

P-434 Is there an association between pre-ovulatory estradiol levels and placental pathology of singleton livebirths conceived with gonadotropins/intrauterine insemination (Gn/IUI) treatments?

Study question

Is pre-ovulatory estradiol level associated with placental weight (PW) and abnormality rates (PAR) in singleton livebirths resulting from gonadotropins/intrauterine insemination (Gn/IUI) treatments?

Summary answer

In Gn/IUI-conceived, singleton-livebirths with available placental pathology, an association was noted between preovulatory estradiol levels and PW, but not between estradiol and PAR.

What is known already

Data suggest an association between ART and placental-mediated pregnancy complications, as well as increased rates of placental pathology. Supraphysiologic levels of preovulatory estradiol have been implicated in abnormal placentation. Whether such an effect is noted in Gn/IUI treatments, where levels of estradiol are lower, nevertheless supraphysiologic, remains unknown.

Study design, size, duration

We retrospectively reviewed data from 560 Gn/IUI-conceived, singleton-livebirths (1/2004-1/2021) recruited from a large academic fertility center. Placental pathology information was available from 218 cycles. These cycles were stratified by pre-ovulatory estradiol levels in quartiles [Q1(lower)-Q4 (higher)]. PW [grams & percentiles (%iles)], and rates of placental abnormalities (classified as anatomic, inflammatory, infectious, and vascular/thrombotic) were compared between groups.

Participants/materials, setting, methods

Participants: Women with Gn/IUI-conceived, singleton-livebirths with available placental pathology.

Outcome Measures: PW and PAR.

Statistics: Regression analysis was utilized to estimate the association of pre-ovulatory estradiol %iles with PW and PAR, adjusting for potential confounders (PW: maternal and gestational age, BMI, infertility diagnosis, medical complications, infant gender; PAR: maternal and gestational age, BMI, race). Adjusted Odds Ratios (OR) with 95%CI were calculated for the latter.

Main results and the role of chance

Mean PW(±SD) in grams were 477.3(±124.1), 445.9(±107.4), 451.2(±113.9), and 438.9(±107.0) in Q1 through Q4 (p=.368). Small placentas (≤10thPW %ile) accounted for more than a third of the total in all estradiol quartiles (37.5%, 49.2%, 37.5%, and 42.2%, p=.539, Q1-Q4, respectively). Similarly, increasingly higher percentages of placentas ≤25th PW %ile were noted with increasing estradiol quartiles (47.9%, 57.6%, 62.5% and 64.5%, in Q1-Q4 respectively, p=.347). After adjusting for potential confounders, we noted a mean 13.7 grams decrease in PW between each subsequent estradiol quartile [ adjβ-coeff (95%CI): -13.7(-27.7-0.3), p=.055]. When estradiol levels were analyzed as a continuous variable, an inverse association with PW [ adjβ-coeff (95%CI): -0.08 (-0.16-(-0.01)), p=.026] was noted. Adjusted ORs for small placenta did not differ between estradiol quartiles or when estradiol was analyzed as a continuous variable [adjORs(95%CI): 1.73(0.74-4.07), 1.10(0.47-2.55), 1.81(0.69-4.72), for Q2-Q4, Q1 as ref.; 1.001(1.000-1.003), p=.167; respectively].

There was no significant association between placental abnormality rates (PAR) and estradiol, either before or after adjustment [adjORs(95%CI): i) Anatomic : 1.16(0.49-2.74), 1.52(0.65-3.59), and 1.17(0.45-3.02); ii) Inflammatory : 0.40(0.13-1.25), 0.79(0.28-2.17), and 1.25(0.42-3.73); iii) Infectious : 0.89(0.35-2.25), 1.67(0.68-4.13), and 0.58(0.20-1.67); iv) Vascular/thrombotic : 0.88(0.37-2.08), 1.87(0.80-4.41), and 0.95(0.36-2.49); for Q2-Q4 vs. Q1].

Limitations, reasons for caution

There are several limitations, including the retrospective design, possible selection bias resulting from the decision to obtain placental pathology. Nonetheless, birth weights did not differ between those with and without placental pathology. Estradiol levels, albeit supraphysiologic, are much lower than those in ART and differences might be masked.

Wider implications of the findings

In Gn/IUI-conceived, singleton-livebirths with available placental pathology, an association was noted between preovulatory estradiol levels and placental weight, but not between estradiol and the rate of specific placental abnormalities (PAR). Since estradiol levels are lower than those observed in ART, an association might have been missed.

Trial registration number

not applicable

P-426 Placental pathology following Intrauterine Insemination (IUI) with or without Ovarian Stimulation (OS)

Study question

Do placental weight percentiles (PW %iles) and abnormality rates (PAR) differ in singleton-livebirths following IUI with or without OS [oral medications (OM), and injectable gonadotropins]?

Summary answer

Following singleton-livebirths, PW did not differ between groups, albeit over half of placentas were ≤25th%ile. Placental anatomic abnormalities were more often seen in OM cycles.

What is known already

ART data suggest a possible association between stimulation-induced supraphysiologic estradiol levels and increased risk of placental abnormalities, as well as subsequent placental-mediated pregnancy complications, such as preeclampsia. Whether there is an association between OS protocols for IUI and placental pathology remains unknown.

Study design, size, duration

Data from 975 IUI(±OS) cycles resulting in singleton livebirths at a large academic fertility center between 01/2004 and 01/2021, were retrospectively reviewed. In 386 cycles a full placental pathologic examination was available. Placentas were stratified by OS regimen into three groups: gonadotropins (n = 222), OM [Clomiphene Citrate (CC)/Letrozole (LTZ); n = 129], and unstimulated / natural (n = 35). PW and PAR were compared between groups.

Participants/materials, setting, methods

Participants: Women delivering a singleton liveborn following IUI(±OS) treatments with placental pathology available.

Outcome Measures: PW (grs & %iles), and PAR (classified as anatomic, inflammatory, infectious, and vascular/thrombotic).

Statistics: Regression analysis was utilized to compare PW and PAR between groups, adjusting for potential confounders (PW: maternal and gestational age, BMI, infertility diagnosis, medical complications, infant gender; PAR: maternal and gestational age, BMI, race). Adjusted Odds Ratios (adjOR, 95%CI) were calculated for the latter.

Main results and the role of chance

Mean(±STDEV) PW (grs) were 451.7(±113.3), 449.2(±102.4), and 481.8(±99.8), for the gonadotropins, OM, and natural groups, respectively. Interestingly, over half of the placentas in all three groups were ≤25th %ile (58.6%, 56.1%, and 52.9%, for gonadotropins, OM, and natural, respectively, p=.249), while 41.8%, 46.4%, and 38.2% were below the 10th %ile (for gonadotropins, OM, and natural, respectively, p=.598). Adjusted PW differences, and adjOR for small placenta (≤10th %ile) did not differ between groups [PW OR(95%CI): 5.6(-17.9-29.2), -28.1(-71.4-15.2), -11.7(-52.6-29.3); small placenta OR(95%CI): 1.04(0.62-1.76); 1.27(0.40-4.01), and 0.96(0.34-2.74) for OM vs. gonadotropins, OM vs. natural, and gonadotropins vs. natural, latter as ref. ].

Regarding PAR, anatomic(43.7%, 52.7%, and 40%, p=.192), inflammatory(20.7%, 27.1%, and 20%, p=.354), infectious(32.9%, 33.3%, and 31.4%, p=.978), and vascular/thrombotic(42.3%, 41.9%, and 42.9%, p=.993) abnormalities rates did not differ between gonadotropins, OM, and natural, respectively. AdjORs(95%CI) for inflammatory, infectious, and vascular/thrombotic abnormalities did not differ significantly between groups. However, anatomic abnormalities were more frequent among OM compared to gonadotropin and natural cycles [adjOR(95%CI): 1.76(1.06-2.91), p=.028, gonadotropins as ref.; 2.52(1.05-6.05), p=.038, natural as ref.].

Limitations, reasons for caution

This study is limited by its retrospective nature. Unfortunately, placental pathology was available only in conceptions clearly identified as resulting from IUI(±OS) treatments. However, birth weights did not differ between those with and without available placental pathology. Natural/IUI cycles were limited in numbers not allowing meaningful conclusions.

Wider implications of the findings

Between IUI-conceived, singleton-livebirths with available placental pathology, mean PW did not differ significantly. However, a higher-than-expected percent of placentas were below the expected %iles, suggesting that IUI(±OS) might be associated with altered placental growth. Placental anatomic abnormalities were more common among OM cycles, compared to gonadotropins, and n atural IUI cycles.

Trial registration number

Not applicable

Importance of frame rate for the measurement of strain and synchrony in fetuses using speckle tracking echocardiography

OBJECTIVES

To assess the influence of frame rate settings on longitudinal strain (LS) and mechanical synchrony (SYN) values in Speckle Tracking Echocardiography (STE) of healthy fetuses.

METHODS

In this prospective study, we collected transversal or apical four-chamber-views of 121 healthy fetuses between 20 and 38 weeks of gestation using three different frame rate (FR) settings (≥ 110, 100 ± 10, 60 ± 10 frames per second). We assessed the segmental and the global LS of both ventricles (2C) and of the left ventricle (LV) offline with QLab 10.8 (Philips Medical Systems, Andover, MA, USA). Inter- and intraventricular SYN were calculated as time difference in peak myocardial strain between the mid-segments of left and right ventricle (interventricular, 2C_Syn) and lateral wall and septum of the left ventricle (intraventricular, LV_Syn), respectively.

RESULTS

In 84.3% STE was feasible at all three FR settings. The LS increased in both views at higher FRs to a statistically noticeable extent. SYN measurements and the absolute differences at patient level between the FR settings showed no statistically noticeable alterations.

CONCLUSIONS

STE is feasible at low and high FR settings. SYN emerges to be a robust parameter for fetal STE as it is less affected by the FR. High FRs enable high temporal resolutions and thus an accurate examination of fetal hearts. Future research for the technical implementation of tailored fetal STE software is necessary for reliable clinical application.

Second trimester fetal thymus size in association to preterm birth

OBJECTIVES

The aim of this study was to compare the second trimester thymus-thorax-ratio (TTR) between fetuses born preterm (study group) and those born after 37 weeks of gestation were completed (control group).

METHODS

This study was conducted as a retrospective evaluation of the ultrasound images of 492 fetuses in the three vessel view. The TTR was defined as the quotient of a.p. thymus diameter and a.p. thoracic diameter.

RESULTS

Fetuses that were preterm showed larger TTR (p<0.001) the second trimester than those born after 37 weeks of gestation were completed. The sensitivity of a binary classifier based on TTR for predicting preterm birth (PTB) was 0.792 and the specificity 0.552.

CONCLUSIONS

In our study, fetuses affected by PTB showed enlarged thymus size. These findings led us to hypothesize, that inflammation and immunomodulatory processes are altered early in pregnancies affected by PTB. However, TTR alone is not able to predict PTB.

O-125 Development of an artificial intelligence embryo witnessing system to accurately track and identify patient specific embryos in a human IVF laboratory

Study question

Can convolutional neural networks (CNN) be used as a witnessing system to accurately track and identify patient specific embryos at the cleavage stage of development?

Summary answer

We developed the first artificial intelligence driven witnessing system to accurately track cleavage and blastocyst stage embryos in a human ART laboratory.

What is known already

There are reports of human errors in embryo tracking that have led to the births of children with different genetic makeup than their birth parents. Clinical practices rely on manual identification, barcodes or radio-frequency identification technology to track embryos. These systems are designed to track culture dishes but are unable to monitor developing embryos within the dish to help ensure an error-free patient match. Previously, we developed an AI witnessing system to track blastocysts with 100% accuracy. The goal of this study was to determine whether an AI witnessing system could be developed that accurately tracks cleavage stage embryos.

Study design, size, duration

A pre-developed deep neural network technology was first trained and tested on 4944 embryos images. The algorithm processed embryo images for each patient and produced a unique key that was associated with the patient ID at 60 hpi, which formed our library. When the algorithm evaluated embryos at 64 hpi it generated another key that was matched with the patient’s unique key available in the library.

Participants/materials, setting, methods

A total of 3068 embryos from 412 patients were examined by the CNN at both 60 hpi and 64 hpi. These timepoints were chosen as they reflect the time our laboratory evaluates Day 3 embryos (60 hpi) and the time we move them to another dish and prepare them for transfer (64 hpi). The patient cohorts ranged from 3-12 embryos per patient.

Main results and the role of chance

The accuracy of the CNN in correctly matching the patient identification with the patient embryo cohort was 100% (CI: 99.1% to 100.0%, n = 412).

Limitations, reasons for caution

Limitations of this study include that all embryos were imaged under identical conditions and within the same EmbryoScope. Additionally, this study only examined fresh Day 3 embryos cultured over a span of 4 hours. Future studies should include images of fresh and frozen/thawed embryos captured using different imaging systems.

Wider implications of the findings

This study describes the first artificial intelligence-based approach for cleavage stage embryo tracking and patient specimen identification in the IVF laboratory. This technology offers a robust witnessing step based on unique morphological features that are specific to each individual embryo.

Trial registration number

This work was partially supported by the Brigham Precision Medicine Developmental Award (Brigham Precision Medicine Program, Brigham and Women’s Hospital), Partners Innovation Discovery Grant (Partners Healthcare), and R01AI118502, and R01AI138800.

Water Sensitive Cities Index: A diagnostic tool to assess water sensitivity and guide management actions

Cities are wrestling with the practical challenges of transitioning urban water services to become water sensitive; capable of enhancing liveability, sustainability, resilience and productivity in the face of climate change, rapid urbanisation, degraded ecosystems and ageing infrastructure. Indicators can be valuable for guiding actions for improvement, but there is not yet an established index that measures the full suite of attributes that constitute water sensitive performance. This paper therefore presents the Water Sensitive Cities (WSC) Index, a new benchmarking and diagnostic tool to assess the water sensitivity of a municipal or metropolitan city, set aspirational targets and inform management responses to improve water sensitive practices. Its 34 indicators are organised into seven goals: ensure good water sensitive governance, increase community capital, achieve equity of essential services, improve productivity and resource efficiency, improve ecological health, ensure quality urban spaces, and promote adaptive infrastructure. The WSC Index design is a quantitative framework based on qualitative rating descriptions and a participatory assessment methodology, enabling local contextual interpretations of the indicators while maintaining a robust universal framework for city comparison and benchmarking. The paper demonstrates its application on three illustrative cases. Rapid uptake of the WSC Index in Australia highlights its value in helping stakeholders develop collective commitment and evidence-based priorities for action to accelerate their city's water sensitive transition. Early testing in cities in Asia, the Pacific and South Africa has also showed the potential of the WSC Index internationally.

Water Sensitive Cities Index: A diagnostic tool to assess water sensitivity and guide management actions

Cities are wrestling with the practical challenges of transitioning urban water services to become water sensitive; capable of enhancing liveability, sustainability, resilience and productivity in the face of climate change, rapid urbanisation, degraded ecosystems and ageing infrastructure. Indicators can be valuable for guiding actions for improvement, but there is not yet an established index that measures the full suite of attributes that constitute water sensitive performance. This paper therefore presents the Water Sensitive Cities (WSC) Index, a new benchmarking and diagnostic tool to assess the water sensitivity of a municipal or metropolitan city, set aspirational targets and inform management responses to improve water sensitive practices. Its 34 indicators are organised into seven goals: ensure good water sensitive governance, increase community capital, achieve equity of essential services, improve productivity and resource efficiency, improve ecological health, ensure quality urban spaces, and promote adaptive infrastructure. The WSC Index design as a quantitative framework based on qualitative rating descriptions and a participatory assessment methodology enables local contextual interpretations of the indicators, while maintaining a robust universal framework for city comparison and benchmarking. The paper demonstrates its application on three illustrative cases. Rapid uptake of the WSC Index in Australia highlights its value in helping stakeholders develop collective commitment and evidence-based priorities for action to accelerate their city's water sensitive transition. Early testing in cities in Asia and the Pacific has also showed the potential of the WSC Index internationally.

Evaluation of Cervical Elastography Strain Pattern to Predict Preterm Birth

PURPOSE

 To evaluate cervical elastography strain pattern as a predictive marker for spontaneous preterm delivery (SPTD).

MATERIALS AND METHODS

 In this case-control study cervical length (CL) and elastographic data (strain ratio, elastography index, strain pattern score) were acquired from 335 pregnant women (20th - 34th week of gestation) by transvaginal ultrasound. Data of 50 preterm deliveries were compared with 285 normal controls. Strain ratio and elastography index were calculated by placing two regions of interest (ROIs) in parallel on the anterior cervical lip. The strain ratio was determined by dividing the higher strain value by the lower one. The elastography index was defined as the maximum of the strain ratio curve. Elastographic images were assigned a new established strain pattern (SP) score between 0 and 2 according to the distribution of strain induced by compression.

RESULTS

 Elastography index, SP score and CL differed between preterm and normal pregnancies (1.61 vs. 1.27, p < 0.001; SP score value of "2": n = 31 (62 %) vs. n = 36 (12.6 %), p < 0.001; CL 30.7 vs. 41.0 mm, p < 0.001; respectively). The elastography index and SP score were associated with a higher predictive potential than CL measurement alone (AUC 0.8059 (area under the curve); AUC 0.7716; AUC 0.7631; respectively). A combination of all parameters proved more predictive than any single parameter (AUC 0.8987; respectively).

CONCLUSION

 Higher elastography index and SP scores were correlated with an elevated risk of SPTD and are superior to CL measurement as a predictive marker. A combination of these parameters could be used as a "Cervical Index" for the prediction of SPTD.

Comparison of strain and dyssynchrony measurements in fetal two-dimensional speckle tracking echocardiography using Philips and TomTec

Background The aim of this study was to compare Philips and TomTec two-dimensional speckle tracking echocardiography (2D-STE) software measurements of strain and dyssynchrony values in healthy fetuses. Methods This was an explorative observational study in which the echocardiographic data of 93 healthy fetuses between the 20th and 38th week of gestation were determined from a four-chamber view using 2D speckle tracking. The global and segmental longitudinal strain values of both ventricles, inter-ventricular and left intra-ventricular dyssynchrony were analyzed using QLab version 10.8 (Philips Medical Systems, Andover, MA, USA) and TomTec-Arena version 2.30 (TomTec, Unterschleißheim, Germany). Results TomTec showed persistently lower values for all of the assessed strain and dyssynchrony variables. For all variables, the bias between vendors tended to increase with gestational age, though not to a significant extent. Left ventricular dyssynchrony and longitudinal strain within the mid segment of the septum correlated best between vendors; however, the limits of agreement were wide in both cases. None of the variables assessed in the two-chamber view compared well between QLAB and TomTec. Conclusion Speckle tracking software cannot be used interchangeably between vendors. Further investigations are necessary to standardize fetal 2D-STE.

Fetal brain development in small-for-gestational age (SGA) fetuses and normal controls

Objective To assess whether fetal brain structures routinely measured during the second and third trimester ultrasound scans, particularly the width of the cavum septi pellucidi (CSP), differ between fetuses small for gestational age (SGA), fetuses very small for gestational age (VSGA) and normal controls. Methods In this retrospective study, we examined standard ultrasound measurements of 116 VSGA, 131 SGA fetuses and 136 normal controls including the head circumference (HC), transversal diameter of the cerebellum (TCD), the sizes of the lateral ventricle (LV) and the cisterna magna (CM) from the second and third trimester ultrasound scans extracted from a clinical database. We measured the CSP in these archived ultrasound scans. The HC/CSP, HC/LV, HC/CM and HC/TCD ratios were calculated as relative values independent of the fetal size. Results The HC/CSP ratio differed notably between the controls and each of the other groups (VSGA P = 0.018 and SGA P = 0.017). No notable difference in the HC/CSP ratio between the VSGA and SGA groups could be found (P = 0.960). The HC/LV, HC/CM and HC/TCD ratios were similar in all the three groups. Conclusion Relative to HC, the CSP is larger in VSGA and SGA fetuses than in normal controls. However, there is no notable difference between VSGA and SGA fetuses, which might be an indicator for abnormal brain development in this group.

Influence of maternal HIV infection on fetal thymus size

Objective To reveal the effect of a maternal human immunodeficiency virus (HIV) infection on the fetal thymus size. Methods The sonographic fetal thymus size was measured retrospectively in 105 pregnancies with maternal HIV infection and in 615 uncomplicated singleton pregnancies. The anteroposterior thymic and the intrathoracic mediastinal diameter were determined in the three-vessel view and their quotient, the thymic-thoracic ratio (TT ratio), was calculated. The study group was subdivided into three groups by the maternal viral load on the date of ultrasound (<50 cop./mL, 50-1000 cop./mL, >1000 cop./mL). Furthermore, an association between prognostic factors of the HIV infection such as the lymphocyte count, CD4/CD8 ratio, HIV medication and the thymus size, was investigated using correlation analyses. Results Fetal thymus size in pregnancies of HIV-positive mothers showed to be noticeably larger than in uncomplicated pregnancies. The mean TT ratio in the HIV-positive group was 0.389 and in the control group 0.345 (P < 0.001). There was no association between any maternal HIV parameter or medication and the size of the thymus gland. Conclusion Maternal HIV infection was associated with an increased fetal thymus size. Further consequences of intrauterine HIV exposure for fetal outcome and the development of the immune system of HIV-exposed uninfected (HEU) infants must be discussed.

Fetal adrenal gland size in gestational diabetes mellitus

Background The aim of this study was to compare the adrenal gland size of fetuses of women with gestational diabetes mellitus (GDM) with that of healthy control fetuses. Methods This prospective cross-sectional study included measurements of the adrenal gland size of 62 GDM fetuses (GDM group) and 370 normal controls (control group) between the 19th and 41st week of gestation. A standardized transversal plane was used to measure the total width and the medulla width. The cortex width and an adrenal gland ratio (total width/medulla width) were calculated from these data. Adrenal gland size measurements were adjusted to the week of gestation and compared between the two groups in a multivariable linear regression analysis. A variance decomposition metric was used to compare the relative importance of predictors of the different adrenal gland size measurements. Results For all the investigated parameters of the adrenal gland size, increased values were found in the case of GDM (P < 0.05), while adjusting for the week of gestation. GDM seems to have a greater impact on the size of the cortex than on the size of the medulla. Conclusion The fetal adrenal gland is enlarged in pregnancy complicated by GDM. The width of the cortex seems to be particularly affected.

Procedure related risk of premature delivery and fetal growth reduction following amniocentesis, transcervical and transabdominal chorionic villus sampling: a retrospective study

Background The aim of this study was to compare transabdominal and transcervical chorionic villus sampling (CVS) as well as amniocentesis (AC) with respect to their rates of premature delivery and fetal growth restriction. Methods We retrospectively evaluated the mentioned procedures of invasive prenatal testing performed in a single center between 2001 and 2016. Seven hundred and ninety-nine cases of AC and 719 cases of CVS were included, of which 400 were performed transvaginally. Only singleton pregnancies with a normal karyotype and delivery after 24 + 0 weeks of gestation were included. Fetal growth restriction was defined as birth weight below the 10th percentile. Premature delivery was defined as delivery before 37 + 0 weeks of gestation. Data were compared to a control group without an invasive procedure. Results The frequency of premature delivery was 8.5% after transabdominal CVS, 6.3% after transcervical CVS and 10.5% after AC as compared to 10.8% in the control group. The frequency of fetal growth restriction was 8.2% after transabdominal CVS 6.8% after transcervical CVS and 8.4% after AC as compared to 9.7% in the control group. Conclusion Our study supports that the three different methods of invasive prenatal testing do not lead to a higher risk of either premature delivery or fetal growth restriction when compared to controls. We found no difference in risk profile among the three techniques.

Strain and dyssynchrony in fetuses with congenital heart disease compared to normal controls using speckle tracking echocardiography (STE)

Objective To compare myocardial strain and mechanical dyssynchrony in fetuses with congenital heart disease (CHD) to normal controls using speckle tracking echocardiography (STE). Methods In this comparative cross-sectional study 23 fetuses with CHD and 105 normal controls between 19 and 41 weeks of gestation were assessed with STE. The STE sample box was placed over the myocardium of both ventricles. The parameters of interest included the segmental strain of the left (LV-S) and right lateral ventricle wall (RV-S) and the global ventricular strain of both chambers (2C-S). In order to separately assess the LV, we placed the STE sample box over the myocardium of the LV. We calculated the strain of the LV lateral wall (LW-S), the septum (SEPT-S) and the global ventricular strain of the single LV (1C-S). Furthermore, we analyzed the differences in timing of negative peak myocardial strain between the LV and RV (two-chamber dyssynchrony, 2C-DYS) and also within the LV between the lateral wall and the septum (one-chamber dyssynchrony, 1C-DYS). Results The evaluation of strain and mechanical dyssynchrony was feasible in all cases. Compared to normal controls, fetuses with CHD showed lower segmental and global strain values and the extent of 2C-DYS and 1C-DYS was higher than in the healthy control group. Conclusion The deterioration of myocardial function in CHD can be measured with STE. The assessment of strain and dyssynchrony with STE may be useful for distinguishing fetuses with CHD from healthy fetuses.

3D Ultrasound Evaluation of the Fetal Outer Ear: Novel Biometry Ratio and Comparison of Different Surface Display Modes

BACKGROUND

The examination of the fetal ear is a promising but still challenging approach in prenatal diagnosis.

OBJECTIVES

This study investigated a novel ear length/width ratio based on anatomical landmarks. Additionally, we compared different 3D ultrasound surface rendering modes regarding their potential to depict detailed structures of the outer ear.

METHOD

We measured both the ear length and width of 118 fetal ears from 20 to 40 weeks of gestation to establish a length/width ratio. Additionally, we rendered the volumes in three different surface display modes and one adapted light position. Each image was scored regarding the visibility of distinct structures of the ear relief and indicator scores were evaluated for each mode.

RESULTS

The median of the length/width ratio was 1.9 with a slight decline over the gestational period. The overall visibility of the ear structures differed noticeably between the four surface display modes (p < 0.001). The post hoc comparison showed that the display mode "TrueVue" resulted in the highest indicator scores.

CONCLUSION

The length/width ratio based on anatomical landmarks of the ear could prospectively be used as a marker in syndrome detection. The study showed a superiority of the surface display mode "TrueVue" for examination of the detailed ear structures.

Comparison of Longitudinal and Apical Foetal Speckle Tracking Echocardiography Using Tissue Motion Annular Displacement and Segmental Longitudinal Strain

The aim of our prospective pilot study with exploratory analysis was to compare longitudinal and apical foetal speckle tracking echocardiography (STE) using tissue motion annular displacement (TMAD) and segmental longitudinal strain (SLS). We compared two different STE quantification tools in a longitudinal and apical four-chamber view in 57 normal foetuses between 20 and 40 wk of gestation. Myocardial mechanical dyssynchrony and strain were assessed using offline quantification software (QLab Version 10.3, Philips Medical Systems, Andover, MA, USA). We compared the dyssynchrony measurements with TMAD and SLS in longitudinal and apical four-chamber views. Furthermore, we examined the segmental strain values of both ventricles with SLS and compared the differences between longitudinal and apical measurements. Dyssynchrony measurements with TMAD and SLS and strain measurements with SLS were feasible in all cases. In the apical view, the dyssynchrony measurements with TMAD were systematically greater than those achieved with SLS (p < 0.001). For the longitudinal view, no differences were observed between tools (p = 0.153). The application of SLS provided similar results for dyssynchrony in both views (intra-class correlation coefficient [ICC] = 0.281, p = 0.623), but the strain measurements in the left and right ventricles differed significantly between views (ICC = -0.082, p = 0.011, and ICC = -0.061, p = 0.024, respectively). For TMAD, we found large differences in the dyssynchrony values between longitudinal and apical assessment (ICC = -0.060, p = 0.03). Furthermore, TMAD exhibited reduced accuracy in the system's automatic tracking algorithm, limiting the data quality. The dyssynchrony assessment is affected less by the foetal position in SLS than in TMAD. The strain readings in SLS varied depending on the view in which they were assessed. The application of TMAD cannot be recommended for foetal STE.

Quantification of fetal myocardial function in pregnant women with diabetic diseases and in normal controls using speckle tracking echocardiography (STE)

Background The purpose of our study was to quantify the fetal myocardial function in pregnant women with diabetic diseases (FDM) and in normal controls (FC) using speckle tracking echocardiography (STE). Methods In this prospective study, the myocardial strain and dyssynchrony were analyzed using STE in a transversal four-chamber view in 180 fetuses (53 FDM, 127 FC) between 19 and 39 weeks of gestation. The measurements of the global and segmental longitudinal strain of both chambers (2C) and of the single left chamber (1C) were executed offline via QLab 10.5 (Philips Medical Systems, Andover, MA, USA). We assessed dyssynchrony as the time difference between peaks in strain in the mid segments of both chambers (interventricular dyssynchrony, 2C_DYS) and of the single left chamber (intraventricular dyssynchrony, 1C_DYS). Results Measurements were feasible with a high median frame rate of 199 frames/s (1st quartile: 174, 3rd quartile: 199). The global and segmental myocardial longitudinal strain of 2C and 1C were decreased and 2C_DYS and 1C_DYS were increased in pregnancies with diabetes compared to normal controls. Conclusion Our study demonstrates that fetal hearts affected by maternal diabetes mellitus (DM) show low myocardial strain values and high interventricular dyssynchrony. Two-chamber interventricular dyssynchrony has the potential to become a diagnostic marker for DM.

Assessment of strain and dyssynchrony in normal fetuses using speckle tracking echocardiography - comparison of three different ultrasound probes

OBJECTIVE

To evaluate segmental left (LV-S) and right (RV-S) ventricular strain as well as longitudinal mechanical myocardial dyssynchrony as a time difference between peaks in strain of both ventricles in fetuses (two-chamber-dyssynchrony, 2C-DYS) using speckle tracking echocardiography (STE). The aim of our study was to evaluate the influence of data acquisition on the results of STE measurement using different ultrasound probes.

METHODS

We prospectively recorded cardiac cycles of four-chamber views of 56 normal fetuses with three different ultrasound probes and analyzed them offline with speckle tracking imaging software. Furthermore, we looked at a possible influence of heartbeat variability (beat-to-beat variability).

RESULTS

The evaluation of the parameters was feasible with all three probes in 53 cases. There was no influence of heartbeat variability and no noticeable differences in 2C-DYS, LV-S and RV-S in all cases and for all three probes determined.

CONCLUSION

Assessment of strain and dyssynchrony using STE with three different probes is comparable. Further research is needed to validate dyssynchrony as a predictor for fetal outcome.

Adrenal gland size in growth restricted fetuses

Objective To compare the adrenal gland size of fetal growth restricted (FGR) and normal control fetuses. Study design In this prospective study the adrenal gland size of 63 FGR fetuses and 343 normal controls was measured between 20 and 41 weeks of gestation. The total width and the medulla width were measured in a new standardized transversal plane. The cortex width and a calculated ratio of the total and medulla width (adrenal gland ratio) were compared between both groups. Results The mean cortex width and the adrenal gland ratio in FGR fetuses were higher in comparison to the controls (P<0.001; P=0.036, respectively). The cortex width correlated positively with the gestational age (control group: P<0.001; FGR group: P=0.089) whilst the adrenal gland ratio showed no association with the gestational age (control group: P=0.153; FGR group: P=0.314). Conclusion The adrenal gland cortex width and the adrenal gland ratio were increased in FGR fetuses compared to normal fetuses.

Fetal brain development in diabetic pregnancies and normal controls

Objective:

To compare the fetal brain structures assessed in routine sonographic scans during the second and third trimesters in diabetic and normal pregnancies.

Methods:

In this retrospective study, we measured the head circumference (HC), the transversal diameter of the cerebellum (TCD) and the sizes of the cisterna magna (CM), the cavum septi pellucidi (CSP) and the lateral ventricles (LV) in stored sonographic scans between 20 and 41 weeks of gestation. We compared 231 fetuses of diabetic mothers (diabetic group) to 231 fetuses of normal pregnancies (control group) matched by gestational age. The diabetic group was divided into three subgroups: pre-existing maternal diabetes, diet-controlled gestational diabetes and insulin-dependent gestational diabetes.

Results:

The mean widths of the CSP and LV were larger in fetuses of diabetic mothers in comparison with the controls (P<0.001, P<0.001; respectively). The sizes of HC, CM and TCD were similar in both groups. These results were consistent across the three subgroups.

Conclusions:

Diabetes is associated with altered fetal brain development. We would like to introduce the increased widths of CSP and LV as potential markers for gestational diabetes.

Assessment of the Fetal Cerebral Artery: Importance of Doppler Preset Settings

OBJECTIVES

The Doppler assessment of the middle cerebral artery (MCA) has a central role in the monitoring of high-risk pregnancies. The objective of this study was to investigate the importance of Doppler preset settings for measurement of the peak systolic velocity (PSV) and pulsatility index (PI) of the MCA.

METHODS

The PI and PSV of the MCA were determined prospectively in 350 healthy fetuses between 19 and 42 weeks of pregnancy. The first measurement of the MCA (MCA.S) was performed with the conventional settings and the second (MCA.O) with an optimized setting of the maximum achievable frame rate. For the MCA.O measurement, the width of the B-mode image and the color Doppler window were adjusted as narrowly as possible. In addition, the MCA was shown in optimized high-definition zoom. Resulting values were compared with commonly used reference values.

RESULTS

The PSV and PI values and frame rates of the MCA.O setting were noticeably greater than those of the MCA.S setting (P < .001 for all). For both settings, the PSV and PI values were increased compared to common reference values.

CONCLUSIONS

The assessment of the MCA with the optimized Doppler default setting yielded increased PSV and PI values compared to the commonly used measurement technique. Moreover, the resulting median curves differed from the established median reference curves. Therefore, an updated standardization for measuring the MCA should be set out, and current reference values should be adjusted.

Assessment of cervical elastography strain pattern and its association with preterm birth

OBJECTIVE

The aim of the study was to assess the cervical strain pattern by an ultrasound elastography cervix examination and to determine its association with preterm delivery.

METHODS

In this study, 30 cases resulting in preterm birth and 30 gestational age-matched controls were included. A vaginal ultrasound examination with cervical length and elastography measurement was performed. We calculated four strain ratios (SR1-SR4) of the regions of interest (ROIs) arranged in pairs in four different positions on the anterior cervical lip. The strain ratios were correlated to the outcome of spontaneous preterm delivery. The inter-observer and intra-observer variability of the strain measurement was evaluated.

RESULTS

We observed an association between the value of the strain ratio that was calculated from the ROIs placed side by side in the middle of the anterior lip (SR4), and preterm delivery (P<0.001). The predictive values of cervical length and SR4 were comparable (AUC 0.7394; AUC 0.8322, respectively). The combination of cervical length and SR4 was superior in predicting preterm delivery compared to both parameters alone (AUC 0.8789). The inter-observer and intra-observer variability of data acquisition and measurement was excellent.

CONCLUSIONS

Our study assesses the cervical elastography strain pattern and shows a correlation to a spontaneous preterm birth.

Quantification of mechanical dyssynchrony in growth restricted fetuses and normal controls using speckle tracking echocardiography (STE)

PURPOSE

To evaluate longitudinal mechanical dyssynchrony in normally grown fetuses by speckle tracking echocardiography (STE) and to compare longitudinal mechanical dyssynchrony in fetal growth restriction (FGR) with normal controls.

MATERIALS AND METHODS

A prospective study was performed on 30 FGR and 62 normally grown fetuses, including 30 controls matched by gestational age, using STE and a transversal four-chamber view. Data analysis was carried out with a high frame rate of about 175 frames/s. Dyssynchrony was analyzed offline with QLab 9 (Philips Medical Systems, Andover, MA, USA) as time differences between peaks in strain of both ventricles and the septum. Inter- and intraventricular and intraseptal dyssynchrony were obtained and inter- and intraobserver reliability was analyzed.

RESULTS

Longitudinal mechanical dyssynchrony was feasible in all cases, with high inter- and intraobserver reliability. Levels of inter- and intraventricular dyssynchrony were higher in the FGR than in the control group.

CONCLUSION

Speckle tracking echocardiography (STE) is a reliable technique for cardiac function assessment in the fetal heart. Interventricular dyssynchrony could be a potential parameter for early detection of subclinical myocardial dysfunction before other parameters demand intervention. The future clinical role of longitudinal mechanical dyssynchrony needs to be verified in larger studies and with a technique customized for prenatal echocardiography.

Fetal loss following invasive prenatal testing: a comparison of transabdominal chorionic villus sampling, transcervical chorionic villus sampling and amniocentesis

OBJECTIVE

The aim of this study was to compare transabdominal chorionic villus sampling, transcervical chorionic villus sampling and amniocentesis with respect to their total fetal loss rates.

METHODS

We retrospectively evaluated procedures of invasive prenatal testing performed during a 14-year period (2001-2014) including 936 amniocentesis procedures and 1051 chorionic villus samplings, of which 405 cases were executed transabdominally and 646 transcervically. Only singleton pregnancies before 24 weeks and 0 days of gestation where the pregnancy outcome was known were included. Fetal loss was defined as an abortion occurring either before 24 weeks and 0 days of gestation or <2 weeks after the procedure.

RESULTS

The total fetal loss rates were determined to be 1.73% for transabdominal chorionic villus sampling, 2.01% for transcervical chorionic villus sampling and 1.18% for amniocentesis. No statistically noticeable differences between the total fetal loss rates of all three procedures were found (P=0.399).

CONCLUSION

Our study has shown that chorionic villus sampling (either transabdominal or transcervical) and amniocentesis are equal methods for invasive prenatal testing with respect to their abortion risk.

Thorax-to-head ratio and defect diameter-to-head ratio in giant omphaloceles as predictor for fetal outcome

PURPOSE

To investigate the relationship between the thorax diameter and defect diameter of giant omphaloceles as a predictor for fetal outcome.

METHODS

In a retrospective study, 17 fetuses with isolated giant omphaloceles were included for evaluation. The anterior-posterior thorax diameter and the defect diameter were measured from ultrasound images. For analysis, the thorax-to-head ratio (T/HC), the defect diameter-to-head ratio (DD/HC), and the quotient of the defect diameter and the thorax diameter (DD/T) were calculated. The days of ventilation (t _ventilation), the duration until hospital discharge (t _hospital), and the type of treatment were recorded as outcome parameters.

RESULTS

No relationship was found between the calculated ratios (T/HC, DD/HC, or DD/T) and neither t _hospital (r = -0.418, p = 0.095; r = -0.153, p = 0.556; and r = -0.023, p = 0.929; respectively) nor t _ventilation (r = -0.391, p = 0.121; r = 0.041, p = 0.875; and r = 0.121, p = 0.645, respectively). The type of postnatal treatment was not associated with the three calculated ratios or t _hospital (r = 0.155, p = 0.553; r = 0.019, p = 0.942; and r = 0.012, p = 0.965; r = -0.009, p = 0.973, respectively). In 53% of cases, t _hospital was delayed due to additional and independent postnatal complications.

CONCLUSION

Thorax diameter or defect diameter of giant omphaloceles is not predictive for fetal outcome. The perinatal care of these abdominal wall defects still remains a multidisciplinary challenge, but the outcome of giant omphaloceles is favorable at experienced centers.

Persistence and reactivation of human adenoviruses in the gastrointestinal tract

Reactivation of persistent human adenoviruses (HAdVs) is associated with high morbidity and mortality in paediatric haematopoietic stem cell transplant (HSCT) recipients. Although invasive HAdV infections mainly arise from the gastrointestinal (GI) tract, the specific sites of HAdV persistence are not well characterised. We prospectively screened biopsies from 143 non-HSCT paediatric patients undergoing GI endoscopy and monitored serial stool specimens from 148 paediatric HSCT recipients for the presence of HAdV by real-time PCR. Persistence of HAdV in the GI tract was identified in 31% of children, with the highest prevalence in the terminal ileum. In situ hybridisation and immunohistochemistry identified HAdV persistence in lymphoid cells of the lamina propria, whereas biopsies from five transplant recipients revealed high numbers of replicating HAdV in intestinal epithelial cells. The prevalence of HAdV species, the frequencies of persistence in the GI tract and reactivations post transplant indicated a correlation of intestinal HAdV shedding pre-transplant with high risk of invasive infection. HAdV persistence in the GI tract is a likely origin of infectious complications in immunocompromised children. Intestinal lymphocytes represent a reservoir for HAdV persistence and reactivation, whereas the intestinal epithelium is the main site of viral proliferation preceding dissemination. The findings have important implications for assessing the risk of life-threatening invasive HAdV infections.

Imaging of fetal thymus in pregnant women with rheumatic diseases

OBJECTIVE

To determine whether certain rheumatic diseases will affect the fetal thymus diameter when compared to uncomplicated singleton pregnancies. Additionally, we created a reference chart for fetal thymus size in healthy singleton pregnancies from 19 to 37 weeks of gestation.

METHODS

Sonographic fetal thymus size was retrospectively evaluated in 190 healthy pregnant women, and 84 pregnancies of mothers suffering from systemic lupus erythematosus, antiphospholipid syndrome (APS), or Sjögren's syndrome between 19 and 37 weeks of gestation. These fetuses were matched one-to-one for gestational age with control fetuses. The thymic-thoracic ratio (TT-ratio) was defined as the quotient of the anteroposterior thymic and the intrathoracic mediastinal diameter.

RESULTS

Rheumatic diseases often affect pregnancy outcome, especially in case of primary APS. The TT ratio of fetuses of mothers suffering from rheumatic disease was equal to controls (P=0.807).

CONCLUSIONS

Ours is the first study to assess the correlation of fetal thymus size in high-risk pregnancies with rheumatic diseases in comparison to controls. Women with rheumatic diseases deal with pregnancy complications more frequently than controls. Our data suggest that maternal rheumatic diseases do not affect the fetal thymus size.

Natural and anthropogenic substrates affect movement behavior of the Southern Graycheek Salamander (Plethodon metcalfi)

Movement behavior is a critical process that interacts with landscape structure to affect population connectivity and persistence in fragmented or altered landscapes. The purpose of our study was to test whether different substrates (forest litter, soil, grass, gravel, and asphalt) found in fragmented forested landscapes affected the movement behavior of the Southern Graycheek Salamander (Plethodon metcalfi Brimley, 1912). Latency period of the salamanders was highest on grass substrate and significantly lower only on soil substrate. Sinuosity of the movement path of salamanders was lowest and contained more turns in grass and was significantly higher than only gravel and asphalt substrates. Velocity of the salamanders was highest on asphalt substrate but was not different from gravel substrate. Velocity was higher on asphalt than on grass, forest, or soil, and velocity was higher on gravel than on grass substrate. The results indicated that P. metcalfi reacted differently to natural and anthropogenic substrates, and we suggest that these behavioral differences could have both positive and negative implications for movement success and habitat resistance in forested landscapes fragmented by roads and development.

Mutational analysis of the activator of late transcription, Alt, in the lactococcal bacteriophage TP901-1

An activator protein, Alt, synthesized during the early state of lytic infection is required for transcription of the late operon in the lactococcal phage TP901-1. In order to identify amino acid residues in the Alt protein required for activation of the TP901-1 late promoter, P(late), hydroxylamine mutagenesis was performed, resulting in almost saturating mutagenesis of alt. Twenty-three different non-functional alt alleles containing one, and in one case two amino acid exchanges were isolated and analyzed. Eight of the twenty-three mutant proteins were still able to activate the P(late) promoter to some extent. Our results show that alt encodes a protein of 16.7 kDa and that the last fourteen amino acids in the C-terminal part of the protein are required for activation of the P(late) promoter. By combining sequence analysis with experimental data we suggest that the C-terminal half of the Alt protein contains a helix-turn-helix-like motif involved in DNA binding. We also propose that the C-terminal half of the Alt protein may be involved in interactions with the bacterial RNA polymerase, whereas the N-terminal half of the protein is proposed to be important for the overall protein structure.

An activator of transcription regulates phage TP901-1 late gene expression

A promoter active in the late phase of the lytic cycle of lactococcal bacteriophage TP901-1 has been identified. The promoter is tightly regulated and requires the product of the phage TP901-1 orf29 for activity. A deletion analysis of the late promoter region showed that a fragment as small as 99 bp contains both the promoter and the region necessary for activation by ORF29. The transcriptional start site of the promoter was identified by primer extension to position 13073 on the TP901-1 genome, thus located 87 bp downstream of orf29 in a 580-bp intergenic region between orf29 and orf30. Furthermore, the region located -85 to -61 bp upstream of the start site was shown to be necessary for promoter activity. During infection, the transcript arising from the late promoter is fully induced at 40 min postinfection, and our results suggest that a certain level of ORF29 must be reached in order to activate transcription of the promoter. Several lactococcal bacteriophages encode ORF29 homologous proteins, indicating that late transcription may be controlled by a similar mechanism in these phages. With the identification of this novel regulator, our results suggest that within the P335 group of lactococcal phages at least two regulatory systems controlling transcription in the late stage of infection exist.

Lactate dehydrogenase has no control on lactate production but has a strong negative control on formate production in Lactococcus lactis

A series of mutant strains of Lactococcus lactis were constructed with lactate dehydrogenase (LDH) activities ranging from below 1% to 133% of the wild-type activity level. The mutants with 59% to 133% of lactate dehydrogenase activity had growth rates similar to the wild-type and showed a homolactic pattern of fermentation. Only after lactate dehydrogenase activity was reduced ninefold compared to the wild-type was the growth rate significantly affected, and the ldh mutants started to produce mixed-acid products (formate, acetate, and ethanol in addition to lactate). Flux control coefficients were determined and it was found that lactate dehydrogenase exerted virtually no control on the glycolytic flux at the wild-type enzyme level and also not on the flux catalyzed by the enzyme itself, i.e. on the lactate production. As expected, the flux towards the mixed-acid products was strongly enhanced in the strain deleted for lactate dehydrogenase. What is more surprising is that the enzyme had a strong negative control ( CLDHJF1 =-1.3) on the flux to formate at the wild-type level of lactate dehydrogenase. Furthermore, we showed that L. lactis has limited excess of capacity of lactate dehydrogenase, only 70% more than needed to catalyze the lactate flux in the wild-type cells.

Cloning and verification of the Lactococcus lactis pyrG gene and characterization of the gene product, CTP synthase

The pyrG gene of Lactococcus lactis subsp. cremoris, encoding CTP synthase, has been cloned and sequenced. It is flanked upstream by an open reading frame showing homology to several aminotransferases and downstream by an open reading frame of unknown function. L. lactis strains harboring disrupted pyrG alleles were constructed. These mutants required cytidine for growth, proving that in L. lactis, the pyrG product is the only enzyme responsible for the amination of UTP to CTP. In contrast to the situation in Escherichia coli, an L. lactis pyrG mutant could be constructed in the presence of a functional cdd gene encoding cytidine deaminase. A characterization of the enzyme revealed similar properties as found for CTP synthases from other organisms. However, unlike the majority of CTP synthases the lactococcal enzyme can convert dUTP to dCTP, although a half saturation concentration of 0.6 mm for dUTP makes it unlikely that this reaction plays a significant physiological role. As for other CTP synthases, the oligomeric structure of the lactococcal enzyme was found to be a tetramer, but unlike most of the other previously characterized enzymes, the tetramer was very stable even at dilute enzyme concentrations.

Changes in rRNA levels during stress invalidates results from mRNA blotting: fluorescence in situ rRNA hybridization permits renormalization for estimation of cellular mRNA levels

Regulation of gene expression can be analyzed by a number of different techniques. Some techniques monitor the level of specific mRNA directly, and others monitor indirectly by determining the level of enzymes encoded by the mRNA. Each method has its own inherent way of normalization. When results obtained by these techniques are compared between experiments in which differences in growth rates, strains, or stress treatments occur, the normalization procedure may have a significant impact on the results. In this report we present a solution to the normalization problem in RNA slot blotting experiments, in which mRNA levels routinely are normalized to a fixed amount of extracted total RNA. The cellular levels of specific mRNA species were estimated using a renormalization with the total RNA content per cell. By a combination of fluorescence in situ rRNA hybridization, which estimates the relative level of rRNA per cell, and slot blotting to rRNA probes, which estimates the level of rRNA per extracted total RNA, the amount of RNA per cell was calculated in a series of heat shock experiments with the gram-positive bacterium Lactococcus lactis. It was found that the level of rRNA per cell decreased to 30% in the course of the heat shock. This lowered ribosome level led to a decrease in the total RNA content, resulting in a gradually increasing overestimation of the mRNA levels throughout the experiment. Using renormalized cellular mRNA levels, the HrcA-mediated regulation of the genes in the hrcA-grpE-dnaK operon was analyzed. The hybridization data suggested a complex heat shock regulation indicating that the mRNA levels continued to rise after 30 min, but after renormalization the calculated average cellular levels exhibited a much simpler induction pattern, eventually attaining a moderately increased value.

Twofold reduction of phosphofructokinase activity in Lactococcus lactis results in strong decreases in growth rate and in glycolytic flux

Two mutant strains of Lactococcus lactis in which the promoter of the las operon, harboring pfk, pyk, and ldh, were replaced by synthetic promoters were constructed. These las mutants had an approximately twofold decrease in the activity of phosphofructokinase, whereas the activities of pyruvate kinase and lactate dehydrogenase remained closer to the wild-type level. In defined medium supplemented with glucose, the growth rate of the mutants was reduced to 57 to 70% of wild-type levels and the glycolytic flux was reduced to 62 to 76% of wild-type levels. In complex medium growth was even further reduced. Surprisingly, the mutants still showed homolactic fermentation, which indicated that the limitation was different from standard glucose-limited conditions. One explanation could be that the reduced activity of phosphofructokinase resulted in the accumulation of sugar-phosphates. Indeed, when one of the mutants was starved for glucose in glucose-limited chemostat, the growth rate could gradually be increased to 195% of the growth rate observed in glucose-saturated batch culture, suggesting that phosphofructokinase does affect the concentration of upstream metabolites. The pools of glucose-6-phosphate and fructose-6-phosphate were subsequently found to be increased two- to fourfold in the las mutants, which indicates that phosphofructokinase exerts strong control over the concentration of these metabolites.

The pyrimidine operon pyrRPB-carA from Lactococcus lactis

The four genes pyrR, pyrP, pyrB, and carA were found to constitute an operon in Lactococcus lactis subsp. lactis MG1363. The functions of the different genes were established by mutational analysis. The first gene in the operon is the pyrimidine regulatory gene, pyrR, which is responsible for the regulation of the expression of the pyrimidine biosynthetic genes leading to UMP formation. The second gene encodes a membrane-bound high-affinity uracil permease, required for utilization of exogenous uracil. The last two genes in the operon, pyrB and carA, encode pyrimidine biosynthetic enzymes; aspartate transcarbamoylase (pyrB) is the second enzyme in the pathway, whereas carbamoyl-phosphate synthetase subunit A (carA) is the small subunit of a heterodimeric enzyme, catalyzing the formation of carbamoyl phosphate. The carA gene product is shown to be required for both pyrimidine and arginine biosynthesis. The expression of the pyrimidine biosynthetic genes including the pyrRPB-carA operon is subject to control at the transcriptional level, most probably by an attenuator mechanism in which PyrR acts as the regulatory protein.

Analysis of the complete DNA sequence of the temperate bacteriophage TP901-1: evolution, structure, and genome organization of lactococcal bacteriophages

A complete analysis of the entire genome of the temperate lactococcal bacteriophage TP901-1 has been performed and the function of 21 of 56 TP901-1-encoded ORFs has been assigned. This knowledge has been used to propose 10 functional modules each responsible for specific functions during bacteriophage TP901-1 proliferation. Short regions of microhomology in intergenic regions present in several lactococcal bacteriophages and chromosomal fragments of Lactococcus lactis are suggested to be points of exchange of genetic material through homologous recombination. Our results indicate that TP901-1 may have evolved by homologous recombination between the host chromosome and a mother phage and support the observation that phage remnants as well as prophages located in the Lactococcus chromosome contribute significantly to bacteriophage evolution. Some proteins encoded in the early transcribed region of the TP901-1 genome were more homologous to proteins encoded by phages infecting gram-positive hosts other than L. lactis. This protein homology argues for the occurrence of horizontal genetic exchange among these bacteriophages and indicates that they have access to a common gene pool.