Targeted disruption of the murine VCAM1 gene: essential role of VCAM-1 in chorioallantoic fusion and placentation

Vascular cell adhesion molecule-1 (VCAM-1) is expressed on vascular endothelium in a variety of inflammatory conditions and mediates leukocyte recruitment from blood into tissues. In this study we report a novel role for VCAM-1 in the formation of the umbilical cord and placenta during development. The murine VCAM1 gene was disrupted by targeted homologous recombination, and a distinct phenotype was found in VCAM-1-deficient embryos. At 8.5 days of gestation, the allantois failed to fuse to the chorion, resulting in abnormal placental development and embryonic death within 1-3 days. In addition, a role for VCAM-1 in early placental formation after chorioallantoic fusion was observed. In a minority of VCAM-1-deficient embryos, the allantois was able to fuse with the chorion, but the allantoic mesoderm was abnormally distributed over the chorionic surface. A small number of VCAM-1-deficient embryos survived, presumably by circumventing the placentation defects. They became viable and fertile adult mice with lack of VCAM-1 expression, normal organs, and an elevated number of circulating blood mononuclear leukocytes.

Perinatal diagnostic evaluation of velamentous umbilical cord insertion: clinical, Doppler, and ultrasonic findings

OBJECTIVE

To evaluate the association between velamentous cord insertion and adverse pregnancy outcome in singleton pregnancies, and to assess the diagnostic usefulness of nonstress testing (NST) and Doppler ultrasound in this condition.

METHODS

We retrospectively reviewed 12,750 consecutive singleton, chromosomally normal pregnancies from July 1989 through December 1993 at the University Hospital of Kuopio, Finland. Of these, 216 were complicated by velamentous umbilical cord insertion, whereas the remaining 12,534 were normal controls. Using multiple regression analysis, we evaluated the risks by noting adverse infant outcomes: low birth weight (LBW), small for gestational age (SGA), preterm delivery, fetal death, admission to a specific infant care unit, low Apgar scores, neonatal acidemia, and abnormal intrapartum fetal heart rate (FHR) patterns. At prenatal visits, NST and Doppler ultrasound examinations were carried out as a routine part of obstetric care.

RESULTS

Even after we controlled for confounding factors, velamentous umbilical cord insertion was associated with higher risk of LBW (odds ratio [OR] 2.32), SGA (OR 1.54), preterm delivery (OR 2.12), low Apgar scores at 1 and 5 minutes (ORs 1.76 and 2.47, respectively), and abnormal intrapartum FHR pattern (OR 1.59). Only 5% of the patients with abnormal insertion showed pathologic NST results at prenatal visits. Ultrasonographic examination was carried out on 80 patients with velamentous umbilical cord insertion as a routine part of obstetric care, and in only one case was direct visualization of the abnormal insertion successful. After we excluded pregnancies with preeclampsia, abnormal umbilical artery Doppler velocimetry was found in none of the cases examined (n = 48).

CONCLUSION

There were substantial differences in pregnancy outcome measures between the subjects with velamentous umbilical cord insertion and controls. Current antepartum methods of tracing uteroplacental problems are not effective in the prenatal detection of abnormal insertion. Therefore, in future studies, the use of other diagnostic tools, such as color Doppler imaging of cord insertion, should be evaluated in high-risk pregnancies followed-up because of fetal growth restriction.

Silencing profilin-1 inhibits endothelial cell proliferation, migration and cord morphogenesis

Expression of several actin-binding proteins including profilin-1 is up-regulated during capillary morphogenesis of endothelial cells, the biological significance of which remains unknown. Specifically, we hypothesized that profilin-1 is important for endothelial migration and proliferation. In this study, we suppressed profilin-1 expression in human umbilical vein endothelial cells by RNA-interference. Gene silencing of profilin-1 led to significant reduction in the formation of actin filaments and focal adhesions. Loss of profilin-1 expression was also associated with reduced dynamics of cell-cell adhesion. Data from both wound-healing experiments and time-lapse imaging of individual cells showed inhibition of cell migration when profilin-1 expression was suppressed. Cells lacking profilin-1 exhibited defects in membrane protrusion, both in terms of its magnitude and directional persistence. Furthermore, loss of profilin-1 expression inhibited cell growth without compromising cell survival, at least in the short-term, thus suggesting that profilin-1 also plays an important role in endothelial proliferation as hypothesized. Finally, silencing profilin-1 expression suppressed matrigel-induced early cord morphogenesis of endothelial cells. Taken together, our data suggest that profilin-1 may play important role in biological events that involve endothelial proliferation, migration and morphogenesis.

Transplantation of porcine umbilical cord matrix cells into the rat brain

Immune rejection of transplanted material is a potential complication of organ donation. In response to tissue transplantation, immune rejection has two components: a host defense directed against the grafted tissue and an immune response from the grafted tissue against the host (graft vs host disease). To treat immune rejection, transplant recipients are typically put on immunosuppression therapy. Complications may arise from immune suppression or from secondary effects of immunosuppression drugs. Our preliminary work indicated that stem cells may be xenotransplanted without immunosuppression therapy. Here, we investigated the survival of pig stem cells derived from umbilical cord mucous connective tissue (UCM) after transplantation into rats. Our data demonstrate that UCM cells survive at least 6 weeks without immune suppression of the host animals after transplantation into either the brain or the periphery. In the first experiment, UCM cells were transplanted into the rat brain and recovered in that tissue 2-6 weeks posttransplantation. At 4 weeks posttransplantation, the UCM cells engrafted into the brain along the injection tract. The cells were small and roughly spherical. The transplanted cells were positively immunostained using a pig-specific antibody for neuronal filament 70 (NF70). In contrast, 6 weeks posttransplantation, about 10% of the UCM cells that were recovered had migrated away from the injection site into the region just ventral to the corpus callosum; these cells also stained positively for NF70. In our second experiment, UCM cells that were engineered to constitutively express enhanced green fluorescent protein (eGFP) were transplanted. These cells were recovered 2-4 weeks after brain transplantation. Engrafted cells expressing eGFP and positively staining for NF70 were recovered. This finding indicates a potential for gene therapy. In the third experiment, to determine whether depositing the graft into the brain protected UCM cells from immune detection/clearance, UCM cells were injected into the tail vein and/or the semitendinosis muscle in a group of animals. UCM cells were recovered from the muscle or within the kidney 3 weeks posttransplantation. In control experiments, rat brains were injected with PKH 26-labeled UCM cells that had been lysed by repeated sonic disruption. One and 2 weeks following injection, no PKH 26-labeled neurons or glia were observed. Taken together, these data indicate that UCM cells can survive xenotransplantation and that a subset of the UCM cells respond to local signals to differentiate along a neural lineage.

The umbilical coiling index in normal pregnancy

OBJECTIVE

To provide reference values for the umbilical coiling index in uncomplicated pregnancy.

METHODS

Umbilical cords were collected from livebom singleton infants born after uncomplicated pregnancies. The umbilical coiling index (UCI) was calculated as the number of coils divided by the cord length in centimeters. The mean value (SD) for the UCI was calculated, and possible correlations of the UCI with maternal age, parity, gestational age at delivery, mode of delivery, sex and birth weight of the infant were examined.

RESULTS

A total of 122 umbilical cords were included. The frequency distribution of the UCI was skewed to the right. The mean (SD) UCI was 0.17 (0.009) coils/cm. There were no significant correlations of the UCI with maternal age, parity, gestational age at delivery, mode of delivery, sex or birth weight of the infant.

CONCLUSIONS

This is the first study to determine the UCI in a group exclusively consisting of uncomplicated pregnancies. The mean value that we found for the UCI may serve as the standard reference, allowing proper interpretation of umbilical coiling in complicated pregnancy.

The murine allantois: emerging paradigms in development of the mammalian umbilical cord and its relation to the fetus

The fertilized egg of the mammal gives rise to the embryo and its extraembryonic structures, all of which develop in intimate relation with each other. Yet, whilst the past several decades have witnessed a vast number of studies on the embryonic component of the conceptus, study of the extraembryonic tissues and their relation to the fetus have been largely ignored. The allantois, precursor tissue of the mature umbilical cord, is a universal feature of all placental mammals that establishes the vital vascular bridge between the fetus and its mother. The allantois differentiates into the umbilical blood vessels, which become secured onto the chorionic component of the placenta at one end and onto the fetus at the other. In this way, fetal blood is channeled through the umbilical cord for exchange with the mother. Despite the importance of this vascular bridge, little is known about how it is made. The aim of this review is to address current understanding of the biology of the allantois in the mouse and genetic control of its features and functions, and to highlight new paradigms concerning the developmental relationship between the fetus and its umbilical cord.

A comprehensive study of the spatial and temporal expression of the col5a1 gene in mouse embryos: a clue for understanding collagen V function in developing connective tissues

Collagen V is a quantitatively minor component of collagen I fibrils and the defective product of classic Ehlers-Danlos syndrome (EDS). To provide new insights into its embryonic function, a continuous evaluation of the expression pattern of proalpha1(V), a chain common to all collagen V molecular forms, was performed by in situ hybridization of developing mouse from 7.5 days after conception (dpc) to birth. Proalpha1(V) transcripts were first detected at 8.5 dpc, signals being considerably augmented at 16.5 dpc and declining at birth. Hybridization signals were, at first, exclusively detected in the dorsal aorta wall, heart, and adnexa. At 10.5 dpc, col5a1 expression was found in the heart, dorsal aorta wall, branchial arches, mesonephrotic tubules, and intestinal mesenchyme and coincided with proalpha1(I) developmental expression. Later stages exhibited an intense signal in more restricted regions, notably the skin, the bones and vertebral column, the cornea, the tendons and ligaments, the peritoneal membranes, the umbilical cord, and the salivary gland. The data revealed the important contribution of collagen V to the development of functional connective tissues. Proalpha1(V) signals were exclusively detected in the flattened cells of the surface ectoderm at 10.5 dpc. By 12.5 dpc, when cells had become cuboidal, the signal switched to the dermal fibroblasts. Thus, type V collagen appears to contribute to epidermis differentiation. Our data also suggest that collagen V participates in bone formation and/or mineralization and in the renewal of stromal cells in the cornea. The results underscore the role of collagen V in developing embryos and provide important clues for analyzing the phenotype of mouse models for EDS.

Hyaluronan content of Wharton's jelly in healthy and Down syndrome fetuses

The mechanisms by which the excess genetic material of chromosome 21 results in the dysmorphologic features of Down syndrome (DS) are largely unknown. It has been found that the extracellular matrix of nuchal skin of DS fetuses exhibits an higher content of hyaluronan (HA) compared to that of euploid fetuses. Since HA plays a central role in many morphogenetic processes during embryogenesis, an alteration in its metabolism could be involved in the pathogenesis of several structural defects of DS. The extracellular matrix of umbilical cord (UC) is the mammalian tissue with one of the highest content of HA. Therefore we sought to explore the quantitative HA modifications during gestation, tissue distribution and HA metabolism in euploid and DS UCs. Euploid UCs (n=28) and UCs from DS fetuses (n=13) were obtained after termination of pregnancy, spontaneous abortion, or at delivery. Quantitative and molecular size analysis were performed using HPLC and FPLC. Tissue distribution was visualized by immunohistochemistry. Gene expression for HA synthases (HAS) and hyaluronidases (HYAL) were quantified by real-time PCR techniques and HYAL activity was detected by zymography. In euploid UC only HA of a molecular weight of 1700 kDA was present while in DS UC an additional lower weight HA molecule of 1100 kDA was found. Immunohistochemistry showed a larger amount of Wharton's jelly HA in DS UCs than in euploid UC. Real-time PCR analysis showed that HAS 2 and HYAL 2 were expressed at significant levels in all specimens. A higher expression of HAS 2 and a lower expression of HYAL 2 was found in the Wharton's jelly of DS fetuses compared to that of euploid fetuses at 14 weeks of gestation. On the contrary, at term HYAL 2 expression was higher in DS specimens than in those from euploid fetuses. Zymographic studies showed a similar behavior with a lower HYAL activity at early gestation and a higher HYAL activity at term gestation in DS UCs compared to euploid specimens. Therefore we can conclude that HA is more represented in DS UCs than in euploid UCs. A complex alteration of the HA metabolism characterized by an increased synthesis of lower weight HA molecules is a peculiarity of DS UCs.

Degree of fetal umbilical venous constriction at the abdominal wall in a low-risk population at 20-40 weeks of gestation

OBJECTIVES

To determine the degree of constriction of the umbilical vein at the abdominal wall in the second half of pregnancy.

METHODS

A total of 283 low-risk singleton pregnancies were recruited for a cross-sectional study, and examined once at 20-40 weeks of gestation. Two sets of ultrasound measurements of the umbilical vein were taken: one at the fetal end of the umbilical cord and another at the inlet through the abdominal wall, the umbilical ring. The diameter was determined as an average of >or=5 repeat measurements. The blood velocity was recorded at the same site.

RESULTS

The time-averaged maximum venous blood velocity in the cord was low (mean 13-19 cm/s during 20-40 weeks of gestation), and the corresponding mean diameter 3.6-8.2 mm. In contrast, the mean of the venous blood velocity at the umbilical ring was 34-41 cm/s and the diameter was 2.8-5.9 mm during the same period. Of 191 pairs of observations, 41 (21%) had a velocity increment of >or=300 %, which corresponds to a diameter reduction to half or more at the umbilical ring.

CONCLUSION

Constriction of the umbilical ring is a common phenomenon in the second half of pregnancy.

Developmental expression of Mab21l2 during mouse embryogenesis

mab-21 has been identified as a critical component required for sensory organ identity establishment in Caenorhabditis elegans. [Chow, K.L., Emmons, S.W., 1994. Development 120, 2579-2592; Chow, E. L., Hall, D.H., Emmons, S.W., 1995. Development 121, 3615-3625]. Human and mouse homologs of this gene have been isolated and their transcripts are predominantly detected in the eye and cerebellum [Margolis, R.L., Stine, O.C., McInnis, M.G., et al., 1996. Hum. Mol. Genet 5, 607-616; Mariani, M., Corradi, A., Baldessari, D., et al., 1998. Mech. Dev. 79, 131-135. We report here the expression profile of a second murine mab-21 homolog, Mab21l2 [Wong, R.L.Y., Wong, H.T., Chow, K.L., 1999. Cyto. Cell Genet., [in press]. Whole mount in situ hybridization data from embryonic day 8.5 to day 15 revealed that Mab21l2 expression patterns partially overlapped with that of Mab21l1. In addition, its strong expression in the mid- and hindbrain, otic vesicle, optic vesicle, maxillary and mandibular process, paraxial mesoderm, dorsal midline, limb bud and developing digits suggest that Mab21l2 has more diverse functions in vertebrate development.

End-results of experimental gastroschisis created by abdominal wall versus umbilical cord defect

An experimental study was conducted to determine the end-results of two different defects on the anterior abdominal wall: an abdominal wall defect (AWD) versus an umbilical cord defect (UCD) using chick embryos. The AWD was created by leaving an intact skin bridge between the defect and the umbilical cord in group 1; the UCD was created on the umbilical cord near the junction of the skin in group 2. At the end of incubation, the intestines appeared hemorrhagic in the AWD group, but not in the UCD group. During microscopic examination, hemorrhagic areas were observed in the bowel wall and mucosal villi in the AWD group but not in the UCD group. The end-result of the defect causing the physiological umbilical hernia resulted in bowel damage resembling the classic picture of gastroschisis (GS). We conclude that the site of the defect in GS is not the abdominal wall itself, but the physiological umbilical hernia.

Umbilical venous pulsation associated with hypercoiled cord in growth-retarded fetuses

Venous pulsatile flows were detected by pulsed Doppler flow velocimetry throughout the entire umbilical cord in 2 cases of intrauterine growth retardation. Although the hearts of these fetuses had no anomalies and their inferior vena cava flows had normal flow velocity patterns, their cords were severely coiled. In these cases, the pulsatile flow in the umbilical cord vein was caused not by an increase in the preload of the fetal heart, but only by hypercoiling of the umbilical cord. This phenomenon also suggests that the coiled umbilical cord exerts a pump-like effect known as a 'pulsometer'.

Paraumbilical intestinal remnant, closed abdominal wall, and midgut loss in a neonate

A newborn with a mummified right paraumbilical intestinal remnant, closed abdominal wall, and loss of most of the midgut raises important questions concerning embryonic abdominal wall closure and the intrauterine events leading to gastroschisis and "congenital" short gut syndrome.

In vitro methods for studying vascularization of the murine allantois and allantoic union with the chorion

Despite the importance of the definitive chorio-allantoic placenta in fetal survival, fetal development, and long-term health of the adult, little is known about how the placenta's individual components, the allantois and the chorion, proliferate and develop. In this chapter, two techniques will be described: (1) explanting murine allantoises for culture in isolation, and (2) grafting murine allantoises into living whole mouse embryos. Together, these will enable study of differentiation of allantoic mesoderm into the umbilical vasculature, and the mechanism(s) by which the allantois unites with the chorion to form the chorio-allantoic placenta.

Umbilical flow distribution to the liver and the ductus venosus in human fetuses during gestation: an anatomy-based mathematical modeling

The partitioning of umbilical vein blood flow between fetal liver and ductus venosus may be an indicator of the fetal well-being, because the goal of the ductus venosus is to supply oxygen and nutrients to heart and brain. Both distribution and blood flow rate of the umbilical vein are functions of the local vascular impedances that, in turn, depend on the anatomical features of the related vessels. In order to investigate the venous blood flows in human fetuses during a normal gestation, a simple lumped parameter mathematical model was developed on the basis of some information achievable by ultrasonographic techniques. Particularly, the diameter and length of umbilical vein and ductus venosus and the volume of the liver were used to derive the vascular impedances. Three different impedance models were adopted for the umbilical vein, the ductus venosus and the hepatic circulation. A linear model described viscous hydraulic dissipations through the umbilical vein, while a quadratic pressure-flow relationship was used for the ductus venosus due to the irregular local hemodynamics at its inlet. Finally, the equivalent impedance of the whole hepatic network was related to the hepatic volume assuming a tree-like, symmetric and self-similar fractal geometry. The hepatic vascular resistances predicted according to the fractal analysis were quite consistent with some experimental measurements in fetal lambs. In agreement with clinical observations, the model predicted blood flows through the ductus venosus and umbilical vein increasing (from about 25 to 75 ml/min and from about 45 to 370 ml/min, respectively) throughout the gestation (20-40 weeks), while the flow fraction shunted via the ductus venosus diminishes (from about 50 to 20%).

Birthweight in liveborn twins: the influence of the umbilical cord insertion and fusion of placentas

OBJECTIVE

To assess the relation of umbilical cord insertion and fusion of placentas with birthweight in monozygotic monochorionic, monozygotic dichorionic, and dizygotic twins.

DESIGN

A prospective population study.

POPULATION

4529 liveborn twin pairs whose birthweight was recorded, placentas were examined, and site of umbilical cord insertion was determined after delivery.

RESULTS

Infants with a peripheral cord insertion weighed 150g less (P < 0.001) than infants with a central cord insertion. Dizygotic infants had a significantly (P < 0.001) higher incidence of central cord insertion (82%) than monozygotic dichorionic (65%) and monozygotic monochorionic (53%) infants. Monozygotic dichorionic infants with fused placentas and a peripheral cord insertion weighed on average 300g less (P < 0.01) than infants with separate placentas and a central cord insertion. In dizygotic infants, fusion of the placentas did not affect birthweight.

CONCLUSIONS

Umbilical cord insertion is associated with birthweight in all types of twins. Fusion of the placentas only affects the birthweight of monozygotic dichorionic, not that of dizygotic infants. This might be due to the greater proximity of implantation of monozygotic dichorionic twins. Dizygotic twins weighed more than monozygotic twins only when placentas were fused and cord insertion was peripheral. Hence, the difference between the mean birthweights of dizygotic, monozygotic dichorionic, and monozygotic monochorionic infants may originate from the least favourable antenatal situation, namely fused placentas with a peripheral cord insertion, which occurs most frequently in monozygotic twins.

Umbilical cord insertion site in early gestation and development of placenta

AIM

To study the relation of umbilical cord insertion (CI) site in early gestation and placental development from the chorion villosum.

METHODS

We ultrasonically measured the distance between the internal cervical Os and the CI site (CID), the distance between the internal cervical Os and lower placenta edge (PLD), and placental thickness at early (10-12 weeks) and mid-gestation (18-20 weeks).

RESULTS

CID in early gestation (CID-Early) correlated with CID in mid-gestation (r(2)=0.171; P<0.01). CID-Early correlated with PLD in mid-gestation (r(2)=0.093; P<0.01). Thickness of chorion villosum or placenta in early gestation did not correlate with that at mid-gestation. Increasing thickness of placenta was significantly higher in long CID-Early (> or =20 mm) cases than short cases (<20 mm) (P<0.05).

CONCLUSIONS

The process of placental development and the placental location are affected by CI location at early gestation, and suggests that this process might be affected by poor blood supply from the low uterine segment when CI site is close to the internal cervical Os.

Early Diagnosis of Bladder Exstrophy: Quantitative Assessment of a Low-Inserted Umbilical Cord

OBJECTIVES

Bladder exstrophy is a rare severe congenital malformation. Early prenatal diagnosis is scarcely described in the literature. Low insertion of the umbilical cord is a constant anatomic feature of bladder exstrophy. The aim of our study was to assess whether early measurements of the umbilical cord insertion-to-genital tubercle length may serve as quantitative measurements for a low-inserted umbilical cord in cases of bladder exstrophy.

METHODS

The umbilical cord insertion-to-genital tubercle length was prospectively measured in all cases referred for a nonvisualized urinary bladder before 18 weeks' gestation. Final diagnoses were compared with prenatal measurements.

RESULTS

Fifteen fetuses were evaluated for a nonvisualized bladder at a mean gestational age of 15.7 weeks (range, 14-17 weeks). Of them, 6 cases were diagnosed with bladder exstrophy, and 9 cases had a normal urinary bladder. All cases with bladder exstrophy had an umbilical cord insertion-to-genital tubercle length below the fifth percentile for gestational age, whereas cases with a normal bladder had a normal measurement.

CONCLUSIONS

Fetuses with bladder exstrophy have an umbilical cord insertion-to-genital tubercle length below the fifth percentile of the general population. This measurement may serve as a complementary objective sonographic parameter in the prenatal assessment and counseling of cases suspected of having bladder exstrophy during early pregnancy.

Circumferential abdominal skin defect possibly due to umbilical cord encirclement

We report on a newborn black male twin with a distinctive circumferential abdominal skin defect who was identified through the Active Malformation Surveillance Program at the Brigham and Women's Hospital. There were no other malformations, and amniotic disruption was not present. Although it cannot be proven, we believe that this skin defect may have been caused by in utero encirclement of the abdomen by an umbilical cord.

Prenatally detected umbilical cord tumor as a sign of diffuse neonatal hemangiomatosis

We report a case of a prenatally detected hemangioma of the umbilical cord as an early sign of diffuse neonatal hemangiomatosis (DNH). The newborn was diagnosed with multiple hemangiomas in the liver, intestines, skin, and brain. Prenatal ultrasound findings, neonatal appearance of the hemangiomas, and the associated complications are illustrated. Interdisciplinary investigations as well as operative and systemic treatment approaches proved to be challenging. This case illustrates how prenatal ultrasound with color Doppler facilitates the early diagnosis of DNH and can help through the early referral to specialized centers for appropriate treatment.

Absence of 5 alpha-reductase activity in the gubernaculum during descent of the fetal pig testis

To evaluate the hypothesis that testicular descent is mediated by the action of high local concentrations of dihydrotestosterone in the gubernaculum, testis, or epididymis, we obtained tissues from 30 male pig fetuses between 63 and 101 days of gestation. We assayed the 5 alpha-reductase activity in homogenates of pooled tissue by following the conversion of (3H)testosterone to (3H)dihydrotestosterone. The 5 alpha-reductase activity in the urethra and prostate increased prior to and during, but decreased after, the period of testicular descent. The 5 alpha-reductase activity in the gubernaculum remained constant throughout gestation and was not significantly higher than the background activity found in umbilical cord, testis plus epididymis, striated thigh muscle and heat inactivated samples of prostate and urethra. Prior to testicular descent, the 5 alpha-reductase activity was approximately 60 to 300 times higher in the urethra than in the gubernaculum, and approximately 20 to 55 times higher in the prostate than in the gubernaculum. These findings indicate that local conversion of testosterone to dihydrotestosterone in the gubernaculum or epididymis does not play a role in the mediation of testicular descent in the pig fetus.

Developing allantois is a primary site of 2'-deoxycoformycin toxicity

In this study, an assessment of normal mouse allantoic development and its sensitivity to 2'-(R)-deoxycoformycin (dCF; Pentostatin) exposure were examined. Both dissecting microscopy and scanning electron microscopy were used to describe the normal growth and morphogenesis of the mouse allantois over gestational days 7-10 as a preliminary step in evaluating potential abnormal allantoic ontogeny and its effect on umbilical cord and placental development. Two abnormal allantoic/umbilical cord phenotypes were observed subsequent to injecting pregnant mice with 5 mg dCF/kg, i.p., on gestational day 7 (GD 7) and evaluating litters on GD 10, 11, and 12. Abnormal phenotypes included: (1) an allantois which extended approximately halfway across the exocoelom but failed to establish a functional contact with the chorion; and (2) a phenotype characterized by reduced expansion of the allantois across the chorionic surface, a very thin umbilical cord, and aberrant vascularization throughout the structure. Both abnormal phenotypes exhibited either an agenesis or hypogenesis of the umbilical cord and chorioallantoic plate, respectively. Neither abnormal phenotype, however, exhibited errors in the directionality of allantoic growth toward the chorion nor in the formation of aberrant contacts between allantois and adjacent yolk sac or amnionic mesenchyme. Statistical interpretation of the experimental data strongly suggested that abnormalities in allantoic/umbilical cord development were directly associated with embryolethality as evidenced by a decline in the frequency of abnormal allantoic/umbilical cord phenotypes over GD 10-12 (73, 36, and 4%; respectively) and a concomitant increase in the frequency of implantation site resorptions over the same time period (7, 47, and 78%). These results strongly suggest that the developing allantois is very sensitive to the effects of dCF exposure, and that interference with its development leads to embryolethality by GD 12.

Assessment of the umbilical cord outside of the delivery room. Part 2

The umbilical cord is crucial to the growth and development of the fetus. Careful inspection in the delivery room and throughout the newborn period is essential. Part 1 of this 2-part series, entitled "Look Before You Clamp: Delivery Room Examination of the Umbilical Cord" (Advances in Neonatal Care, Vol. 2, No. 1, pp 19-26), reviewed umbilical problems that present in the delivery room. A number of subtle but significant umbilical cord abnormalities present outside the delivery room. These abnormalities will be the focus of Part 2 of this series. A review of the embryologic development of the umbilical cord enhances the clinician's understanding of umbilical abnormalities that present in the newborn period. The process of umbilical cord separation is outlined. Conditions associated with delayed cord separation are discussed. A systematic approach to the physical examination of the umbilicus is offered, with an emphasis on early detection of abnormalities. Common and uncommon physical findings, such as omphalitis, periumbilical necrotizing fascitis, vitelline duct remnants, and urachal anomalies are presented along with select photographs. A brief discussion of the clinical implications for newborn care is provided for the practicing clinician.