Developmental Errors Research Articles

Congenital nasolacrimal duct cyst/dacryocystocele: An argument for a genetic basis.

Embryogenesis of a congenital nasolacrimal duct (NLD) cyst is attributed to the failure of the Hasner membrane of the NLD system to cannulate. Prenatal diagnosis of congenital NLD cysts supports the argument for a developmental error, with a postnatal prevalence of 6%. The role of a genetic basis for this malformation has never been ascribed. We present a set of monozygotic twins with bilateral congenital NLD cysts as an argument for a genetic basis of this entity. A case report and literature review were performed. We present two cases of bilateral congenital NLD cysts occurring in a set of monozygotic twins. Patients were delivered at 37 weeks via cesarean section. The pregnancy was complicated by preterm labor at 33 weeks requiring administration of terbutaline and betamethasone. At presentation, twin A had bilateral eye discharge, erythema, and swelling medial to the medial canthi as well as nasal obstruction. Computed tomography (CT) showed classic bilateral cystic masses in the inferior meatus. The diagnosis of bilateral infected congenital dacryocystoceles was made. Twin B initially presented with only bilateral eye discharge and CT showed a dilated NLD system. Twin B subsequently developed early signs of bilateral dacryocystoceles the following day. Both patients underwent lacrimal probing and endoscopic marsupialization of the dacryocystoceles. Biopsies were consistent with dacryocystocele. Dacryocystocele is a common presentation of unresolved neonatal NLD obstruction. This case report in a set of identical twins is an argument for a genetic basis for the formation of this lesion.

Genetics of congenital anomalies of the kidney and urinary tract

Congenital anomalies of the kidney and urinary tract (CAKUT) occur at a frequency of 1 in 500 live births and are a common cause of renal insufficiency in childhood. CAKUT encompass a wide spectrum of malformations including anomalies of the kidney, collecting system, bladder and urethra. Most cases of CAKUT are sporadic and limited to the urinary tract, but some of them are syndromic or associated with positive family history. To understand the basis of human renal anomalies, knowledge of kidney and urinary tract development is necessary. This process is very complicated, requires precise integration of a variety of progenitor cell populations of diverse embryonic origins and is controlled by many factors at every stage of development. This review focuses on the genetic factors leading to developmental errors of important morphogenetic processes, particularly in metanephric kidney induction and ureteric bud branching. The essential results of genetic studies in regard to CAKUT, performed on experimental models and in humans, are presented. However, further investigations are required to complete understanding of the complex molecular network, which will help us to determine novel preventive and therapeutic strategies for CAKUT.

The effect of genetic and environmental variation on genital size in male Drosophila: canalized but developmentally unstable.

The genitalia of most male arthropods scale hypoallometrically with body size, that is they are more or less the same size across large and small individuals in a population. Such scaling is expected to arise when genital traits show less variation than somatic traits in response to factors that generate size variation among individuals in a population. Nevertheless, there have been few studies directly examining the relative sensitivity of genital and somatic traits to factors that affect their size. Such studies are key to understanding genital evolution and the evolution of morphological scaling relationships more generally. Previous studies indicate that the size of genital traits in male Drosophila melanogaster show a relatively low response to variation in environmental factors that affect trait size. Here we show that the size of genital traits in male fruit flies also exhibit a relatively low response to variation in genetic factors that affect trait size. Importantly, however, this low response is only to genetic factors that affect body and organ size systemically, not those that affect organ size autonomously. Further, we show that the genital traits do not show low levels of developmental instability, which is the response to stochastic developmental errors that also influence organ size autonomously. We discuss these results in the context of current hypotheses on the proximate and ultimate mechanisms that generate genital hypoallometry.

Notch/Delta signalling is not required for segment generation in the basally branching insectGryllus bimaculatus

Arthropods and vertebrates display a segmental body organisation along all or part of the anterior-posterior axis. Whether this reflects a shared, ancestral developmental genetic mechanism for segmentation is uncertain. In vertebrates, segments are formed sequentially by a segmentation 'clock' of oscillating gene expression involving Notch pathway components. Recent studies in spiders and basal insects have suggested that segmentation in these arthropods also involves Notch-based signalling. These observations have been interpreted as evidence for a shared, ancestral gene network for insect, arthropod and bilaterian segmentation. However, because this pathway can play multiple roles in development, elucidating the specific requirements for Notch signalling is important for understanding the ancestry of segmentation. Here we show that Delta, a ligand of the Notch pathway, is not required for segment formation in the cricket Gryllus bimaculatus, which retains ancestral characteristics of arthropod embryogenesis. Segment patterning genes are expressed before Delta in abdominal segments, and Delta expression does not oscillate in the pre-segmental region or in formed segments. Instead, Delta is required for neuroectoderm and mesectoderm formation; embryos missing these tissues are developmentally delayed and show defects in segment morphology but normal segment number. Thus, what initially appear to be 'segmentation phenotypes' can in fact be due to developmental delays and cell specification errors. Our data do not support an essential or ancestral role of Notch signalling in segment generation across the arthropods, and show that the pleiotropy of the Notch pathway can confound speculation on possible segmentation mechanisms in the last common bilaterian ancestor.

Unilateral hydronephrosis and hydroureter secondary to ureteric atresia, and uterus unicornis in a young terrier

A nine-month-old entire female terrier cross was presented with intermittent anorexia, vomiting and recent onset of abdominal pain and distension. A diagnosis of unilateral hydronephrosis was made following ultrasound examination and intravenous urography, but no cause was identified. Subsequent ureteronephrectomy and histology of the affected kidney showed ureteric atresia as the cause of obstruction. Uterus unicornis was also identified and ovariohysterectomy was performed. The combination of structural abnormalities can be explained by an in-utero developmental error of their common embryological precursor, the mesonephric duct.

Monochorionic twins discordant for congenital heart disease: a referral center's experience and possible pathophysiologic mechanisms

To describe the spectrum of cardiac defects in monochorionic (MC) twins discordant for congenital heart disease (CHD) in a referral center population. Retrospective study of all twin gestations undergoing echocardiography between 2000 and 2009 at our institution. A total of 356 twin pairs were evaluated during the study period, 202 for suspected twin-twin transfusion syndrome (TTTS) and the remainder for other indications. Twenty-nine MC pairs were discordant for CHD: laterality defects, 24% [right (2) or left (3) isomerism (3), primitive heart (2)]; ventricular hypoplasia secondary to semilunar valve obstruction, 14% [hypoplastic left heart syndrome (2), severe pulmonary stenosis (PS) or atresia (2)]; valvar dysplasias in TTTS recipients, 27% [PS (4), mitral/tricuspid dysplasia (4)]; conjoining, 14% (4); and other developmental errors, 21% [conotruncal (1), tricuspid atresia (2), ventricular septal defect (2)]. The spectrum of lesions in individuals assumed to be genetically identical and the disproportionate incidence of laterality and ventricular hypoplasia in this population leads us to propose potential mechanisms for the development of CHD in this population including local environmental or epigenetic factors influencing gene expression differentially, abnormal reciprocal laterality signaling between twinned embryos, or placental vascular factors affecting hemodynamics, either early in gestation or later in the setting of TTTS, leading to valvar lesions and ventricular hypoplasia.

Who lives and who dies: Role of apoptosis in quashing developmental errors.

Apoptosis is essential for normal development. Large numbers of cells are eliminated by apoptosis in early neural development and during the formation of neural connections. However, our understanding of this life-or-death decision is incomplete, because it is difficult to identify dying cells by conventional strategies. Live imaging is powerful for studying apoptosis, because it can trace a death-fated cell throughout its lifetime. The Drosophila sensory organ development is a convenient system for studying neural-cell selection via lateral inhibition. We recently showed that about 20% of the differentiating neuronal cells die during sensory organ development, which results in the characteristic spatial patterning of the sensory organs. The eliminated differentiating neurons expressed neurogenic genes and high levels of activated Notch. Thus, live imaging allowed us to document the role of apoptosis in neural progenitor selection, and revealed that Notch activation is the mechanism determining which cells die during sensory organ development.

Chernobyl birds have smaller brains.

BackgroundAnimals living in areas contaminated by radioactive material from Chernobyl suffer from increased oxidative stress and low levels of antioxidants. Therefore, normal development of the nervous system is jeopardized as reflected by high frequencies of developmental errors, reduced brain size and impaired cognitive abilities in humans. Alternatively, associations between psychological effects and radiation have been attributed to post-traumatic stress in humans.Methodology/Principal FindingHere we used an extensive sample of 550 birds belonging to 48 species to test the prediction that even in the absence of post-traumatic stress, there is a negative association between relative brain size and level of background radiation. We found a negative association between brain size as reflected by external head volume and level of background radiation, independent of structural body size and body mass. The observed reduction in brain size in relation to background radiation amounted to 5% across the range of almost a factor 5,000 in radiation level. Species differed significantly in reduction in brain size with increasing background radiation, and brain size was the only morphological character that showed a negative relationship with radiation. Brain size was significantly smaller in yearlings than in older individuals.Conclusions/SignificanceLow dose radiation can have significant effects on normal brain development as reflected by brain size and therefore potentially cognitive ability. The fact that brain size was smaller in yearlings than in older individuals implies that there was significant directional selection on brain size with individuals with larger brains experiencing a viability advantage.

Apoptosis Ensures Spacing Pattern Formation of Drosophila Sensory Organs

In both vertebrates and invertebrates, developing organs and tissues must be precisely patterned. One patterning mechanism is Notch/Delta-mediated lateral inhibition. Through the process of lateral inhibition, Drosophila sensory organ precursors (SOPs) are selected and sensory bristles form into a regular pattern. SOP cell fate is determined by high Delta expression and following expression of neurogenic genes like neuralized. SOP selection is spatially and temporally regulated; however, the dynamic process of precise pattern formation is not clearly understood. In this study, using live-imaging analysis, we show that the appearance of neuralized-positive cells is random in both timing and position. Excess neuralized-positive cells are produced by developmental errors at several steps preceding and accompanying lateral inhibition. About 20% of the neuralized-positive cells show aberrant cell characteristics and high Notch activation, which not only suppress neural differentiation but also induce caspase-dependent cell death. These cells never develop into sensory organs, nor do they disturb bristle patterning. Our study reveals the incidence of developmental errors that produce excess neuralized-positive cells during sensory organ development. Notch activation in neuralized-positive cells determines aberrant cell fate and typically induces caspase-dependent cell death. Apoptosis is utilized as a mechanism to remove cells that start neural differentiation at aberrant positions and timing and to ensure robust spacing pattern formation.

Relative Clauses in Hong Kong English: A Corpus-based Perspective

This study, with the help of the International Corpus of English, contrastively explores uses of relative clauses by students in Hong Kong, Singapore and British English within the framework of world Englishes (Kachru, Asian Englishes: Beyond the Canon, Hong Kong University Press, 2005, Indian Journal of Applied Linguistics, 15: 85-95, 1989; Kachru & Nelson, World English in Asian Contexts, Hong Kong University Press, 2006). First, in the Hong Kong data, there is probably a tendency to use restrictive relative clauses led by WHICH in places where non-restrictive relative clauses led by WHICH are normally expected. Second, there is another tendency in the employment of non-restricted relative clauses led by THAT in Hong Kong university students' written work and it is interesting to note that this phenomenon seems to be more widespread in Hong Kong student writing than in Singapore student writing and no such cases were found out in the British subcorpus. Given that some distinctive patterns traditionally considered as developmental errors in the language learning process may also be seen as evidence of linguistic variations, second language teachers may need some tolerance towards this variation and compromise between “autonomy” and “grammaticality” in today's society of world Englishes (McKay, International English in Its Sociolinguistic contexts: Towards a Socially Sensitive EIL Pedagogy, Routledge, 2008). 本研究借助国际英语语料库，在“世界英语”（Kachru, Asian Englishes: Beyond the Canon, Hong Kong University Press, 2005, Indian Journal of Applied Linguistics, 15: 85-95, 1989; Kachru & Nelson, World English in Asian Contexts, Hong Kong University Press, 2006)的框架下探讨了香港英语、新加坡英语和英式英语中学生英语作文里的定语从句的使用情况。香港英语似乎往往会在一般情况下使用非限制性定语从句的地方使用以which引导的限制性定语从句。在香港学生英语作文中似乎还存在用that来引导非限制性定语从句的情况，这种情况比在新加坡英语中要多，在英式英语中不存在。这些特点被传统地认为是发展中的语言错误，但从“世界英语”的角度来看，有可能是语言变体的特点。在当今世界英语的社会里，二语老师也许应该对这种变异有所宽容，并在语言“自主性”以及“语法性”之间取得一定的妥协（McKay, International English in Its Sociolinguistic contexts: Towards a Socially Sensitive EIL Pedagogy, Routledge, 2008)。

Disturbances in the positioning, proliferation and apoptosis of neural progenitors contribute to subcortical band heterotopia formation

Cortical malformations are commonly associated with intractable epilepsy and other developmental disorders. Our studies utilize the tish rat, a spontaneously occurring genetic model of subcortical band heterotopia (SBH) associated with epilepsy, to evaluate the developmental events underlying SBH formation in the neocortex. Our results demonstrate that Pax6+ and Tbr2+ progenitors are mislocalized in tish+/− and tish−/−- neocortex throughout neurogenesis. In addition, mislocalized tish−/− progenitors possess a longer cell cycle than wild type or normally-positioned tish−/− progenitors, owing to a lengthened G2+M+G1 time. This mislocalization is not associated with adherens junction breakdown or loss of radial glial polarity in the ventricular zone (VZ), as assessed by immunohistochemistry against phalloidin (to identify F-actin), aPKC-λ and Par3. However, vimentin immunohistochemistry indicates that the radial glial scaffold is disrupted in the region of the tish−/− heterotopia. Moreover, lineage tracing experiments using in utero electroporation in tish−/− neocortex demonstrate that mislocalized progenitors do not retain contact with the ventricular surface and that ventricular/subventricular zone (SVZ) progenitors produce neurons that migrate into both the heterotopia and cortical plate (CP). Taken together, these findings define a series of developmental errors contributing to SBH formation that differs fundamentally from a primary error in neuronal migration.

Human fetal/tumor metakaryotic stem cells: pangenomic homologous pairing and telomeric end-joining of chromatids

Metakaryotic cells and syncytia with large, hollow, bell-shaped nuclei demonstrate symmetrical and asymmetrical amitotic nuclear fissions in microanatomical positions and numbers expected of stem cell lineages in tissues of all three primordial germ layers and their derived tumors. Using fluorescence in situ hybridization, mononuclear metakaryotic interphase cells have been found with only 23 centromeric and 23 telomeric staining regions. Syncytial bell-shaped nuclei found approximately during weeks 5–12 of human gestation display 23 centromeric and either 23 or 46 telomeric staining regions. These images suggest that (1) homologous chromatids pair at centromeres and telomeres, (2) all paired telomeres join end-to-end with other paired telomeres in all mononuclear and some syncytial metakaryotic cells, and (3) telomere junctions may open and close during the syncytial phase of development. Twenty-three telomeric joining figures could be accounted by 23 rings of one chromatid pair each, a single pangenomic ring of 23 joined chromatid pairs, or any of many possible sets of oligo-chromatid pair rings. As telomeric end-joining may affect peri-telomeric gene expression, a programmed sequence of telomeric end-joining associations in metakaryotic stem cells could guide developmental arboration and errors in, or interruptions of, this program could contribute to carcinogenesis.

New insights into the pathogenesis of spinal muscular atrophy

To clarify the pathomechanism of spinal muscular atrophy (SMA) with mutations in the gene for survival motor neuron (SMN) protein, postmortem neuropathological analyses were performed on spinal cords obtained at autopsy from 2 fetuses with SMA, 5 infants and a low teenager with SMA type 1, and a higher teenager with SMA type 2; the diagnosis of all of them was confirmed clinically and genetically. Histopathologically, it was noted that lower motor neurons (LMNs) in the SMA cases showed immature profiles characterized by fine Nissl bodies restricted to the periphery of small round somata with a few cell processes in the fetal period, and showed small-sized profiles in the postnatal period. LMNs began to reduce in size and number in the fetal period, ballooned neurons (BNs) appeared postnatally, and the remaining LMNs including BNs diminished with age. BNs were filled with phosphorylated neurofilament protein, and morphologically similar to but smaller than typical chromatolytic neurons as axonal reaction. The population of survived LMNs was relatively preserved in an SMA type 2 case, who lived to 17-year-old, as compared to SMA type 1 cases. Immunohistochemical analysis demonstrated expression of Bcl-2, Bax, activated caspase-3 and SMN in the LMNs prominent in the fetal cases. There was no significant difference in staining for these substances between the control and SMA cases. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay revealed no significant signal in the control and SMA cases. Given that downregulation of SMN leads to a failure in neurite outgrowth and neuromuscular contact of LMNs, the present results suggest the involvement of a fetal developmental maturation error as well as a postnatal retrograde dying-back degeneration of LMNs in SMN-mutated SMA.

Lumbar lipomyelomeningocele and sacrococcygeal teratoma in siblings: support for an alternative theory of spinal teratoma formation

Sacrococcygeal teratomas may arise in association with regional developmental errors affecting the caudal embryonic segments and may originate within lumbosacral lipomas. It is therefore possible that sacrococcygeal teratomas and lumbosacral lipomas represent related disorders of embryogenesis. Accordingly, the authors report the cases of 2 siblings. The first child (female) was born with a mature Altman Type III sacrococcygeal teratoma that was resected when she was a neonate. Subsequently, a younger brother was found soon after birth to have an L-4-level lipomyelomeningocele and underwent partial resection and spinal cord untethering at 4 months of age. Although familial forms of each of these conditions have been reported, this is, to the authors' knowledge, the first reported occurrence of lipomyelomeningocele and sacrococcygeal teratoma in siblings. They propose that an inherited regional tendency to developmental error affecting the caudal embryonic segments was shared by these siblings and resulted in spinal teratoma formation in one of them.

Commentary to the paper double neural tube defect: a case report and discussions on neural tube development by V. Ravindran

This is a case report of a child with double neural tube defect (NTD) comprising a parietal encephalocoele and an open thoracic myelomeningocoele. The authors use this case to endorse the multi-site neural tube closure theory as aetiology for all multiple NTDs. Proponents of this theory claim that neural tube defects occur at “collision sites” of neural tube closure with opposing closure directions, and because up to five or six of these waves are thought to be operational, there are, accordingly, multiple collision sites. The multi-site closure theory was used originally to explain the different favoured locations of encephalcoeles, and as such, the theory is seductive. At collision sites, the overlying myocutaneous tissues may be potentially weaker and, therefore, susceptible to being stretched but not disrupted by a focal herniation of the alar plates of the already closed cranial neural tube and surrounding meninges. The disorganised gyral development and cortical dysplasia of the herniated brain may be secondary to early tissue distortion. The overlying skin and meninges are intact. Spinal open neural tube defects (ONTD) are due to focal absence of neural plate closure, as shown in numerous, very credible animal experiments. The skin, muscles, neural arches and dura are wide open, and the exposed neural material is an unfused neural plate. This true “closure lesion” is thus fundamentally different from a “collision lesion” exemplified by the encephalocoele. Most spinal ONTDs are terminal lesions involving the end of the primary neural tube, but there are rare examples of segmental lesions in which the “suspended” open neural placode is flanked by normal spinal cord both rostrally and caudally. The incomplete neural plate closure occurs in a square-pulse fashion followed by resumption of normal closure. Three percent of ONTDs in our unit are segmental placodes. Most hemi-myelomeningocoeles associated with split cord malformation (SCM) are segmental lesions. Limited dorsal myeloschisis (LDM), though not technically “open”, is a segmental neural tube closure abnormality, as is dorsal lipoma, a lesion of segmental premature disjunction. If there can be one segmental closure failure, why not two or even three square pulse insults, separated in time, causing in tandem closure lesions resulting in either two segmental ONTDs or one segmental and one terminal ONTD? Other multiple neural tube closure abnormalities, though rare, have been reported, such as double LDMs, double dorsal lipomas and double dermal sinus tracts. Even double SCMs caused by multi-focal gastrulation defects with multiple endomeschymal tracts are well known in the literature. Thus, multiple spinal ONTDs can conceivably occur without invoking the multiple closure-wave theory, which, in the spinal cord will produce a very different lesion. It is not known why there should be abrupt recovery of normal neural tube closure after the square pulse insult. There could conceivably be transient presence of a teratogenic impulse that disturbs certain downstream transcription factors, without a fixed genomic mutation that would perpetuate the developmental error. It is thus the timing of the next transient insult that determines the location of the second neural tube defect, rather than the activities of the colliding zippers.

The Cantonese double object construction with bei2 ‘give’ in bilingual children: The role of input

This article examines the role of input in bilingual children’s acquisition of the Cantonese double object construction with bei2 ‘give’ from a usage-based perspective (Tomasello, 2003; Lieven & Tomasello, 2008). In this domain of grammar, bilingual Cantonese—English children use the non-target [ bei2-Recipient-Theme] order more frequently and for a more protracted duration than their monolingual counterparts (Yip & Matthews, 2007). We make use of corpus data to analyze the quantitative and qualitative aspects of the input that these bilingual children receive, and discuss three input factors to account for such vulnerability in bilingual children. First, the findings substantiate the idea that a bilingual child hearing fewer hours of Cantonese when compared to his or her monolingual age peers is likely to be exposed to fewer tokens of the target construction. Second, the findings indicate that the mapping between word order and thematic roles is not consistent in the Cantonese input, and as such is not conducive to learning for either bilingual or monolingual children. Third, simultaneous experience with the largely invariant [ give-Recipient-Theme] forms from the English input overlaps with and therefore entrenches the developmental errors in Cantonese. These three input factors conspire to make this grammatical domain in Cantonese particularly vulnerable in bilingual children.

Relationship between speech, oromotor, language and cognitive abilities in children with Down's syndrome

Children and young people with Down's syndrome present with deficits in expressive speech and language, accompanied by strengths in vocabulary comprehension compared with non-verbal mental age. Intelligibility is particularly low, but whether speech is delayed or disordered is a controversial topic. Most studies suggest a delay, but no studies explore the relationship between cognitive or language skills and intelligibility. This study sought to determine whether severity of speech disorder correlates with language and cognitive level and to classify the types of errors, developmental or non-developmental, that occur in the speech of children and adolescents with Down's syndrome. Fifteen children and adolescents with Down's syndrome (aged 9-18 years) were recruited. Participants completed a battery of standardized speech, language and cognitive assessments. The phonology assessment was subject to phonological and phonetic analyses. Results from each test were correlated to determine relationships. Individuals with Down's syndrome present with deficits in receptive and expressive language that are not wholly accounted for by their cognitive delay. Receptive vocabulary is a strength in comparison with expressive and receptive language skills, but it was unclear from the findings whether it is more advanced compared with non-verbal cognitive skills. The majority of speech errors were developmental in nature, but all of the children with Down's syndrome showed at least one atypical or non-developmental speech error. Children with Down's syndrome present with speech disorders characterized by atypical, and often unusual, errors alongside many developmental errors. A lack of correlation between speech and cognition or language measures suggests that the speech disorder in Down's syndrome is not simply due to cognitive delay. Better differential diagnosis of speech disorders in Down's syndrome is required, allowing interventions to target the specific disorder in each individual.

Molecular genetics of congenital atrial septal defects.

Congenital heart defects (CHD) are the most common developmental errors in humans, affecting 8 out of 1,000 newborns. Clinical diagnosis and treatment of CHD has dramatically improved in the last decades. Hence, the majority of CHD patients are now reaching reproductive age. While the risk of familial recurrence has been evaluated in various population studies, little is known about the genetic pathogenesis of CHD. In recent years significant progress has been made in uncovering genetic processes during cardiac development. Data from human genetic studies in CHD patients indicate that the genetic aetiology was presumably underestimated in the past. Inherited mutations in genes encoding cardiac transcription factors and sarcomeric proteins were found as an underlying cause for familial recurrence of non-syndromic CHD in humans, in particular cardiac septal defects. Notably, the cardiac phenotypes most frequently seen in mutation carriers are ostium secundum atrial septal defects (ASDII). This review outlines experimental approaches employed for the detection of CHD-related genes in humans and summarizes recent findings in molecular genetics of congenital cardiac septal defects with an emphasis on ASDII.

Delayed acquisition of irregular inflectional morphology in Hebrew in early sequential bilingualism

Acquisition of the irregular forms of inflectional morphology may be a challenge for bilingual students because of the possible effect of infrequent input. Focusing on irregular plural forms of languages such as Hebrew can contribute to better understanding how bilingual children cope with anomalous morphological forms. The present study compares Russian— Hebrew-speaking sequential bilingual children with Hebrew-speaking monolingual children in their command on four measures of irregular forms of Hebrew plural nouns at two data collection points: the beginning of the second grade and the beginning of the third grade, at a time when the acquisition of these forms is still going on. Although results show that the bilingual children continued to be less accurate than their monolingual peers in producing the irregular forms at the second point of data collection, the medium-size effect (Cohen, 1992) was obtained only on one of four measures. Furthermore, the finding attests to the significant improvement of both groups in the course of one school year on all categories of irregular plural forms. It was also found that both groups acquire the irregular forms of the Hebrew plural noun system in a similar way and exhibit related patterns of developmental errors.

3-D MR imaging of ectopia vasa deferentia

Ectopia vasa deferentia is a complex anomaly characterized by abnormal termination of the urethral end of the vas deferens into the urinary tract due to an incompletely understood developmental error of the distal Wolffian duct. Associated anomalies of the lower gastrointestinal tract and upper urinary tract are also commonly present due to closely related embryological development. Although around 32 cases have been reported in the literature, the MR appearance of this condition has not been previously described. We report a child with high anorectal malformation who was found to have ectopia vasa deferentia, crossed fused renal ectopia and type II caudal regression syndrome on MR examination. In addition to the salient features of this entity on reconstructed MR images, the important role of 3-D MRI in establishing an unequivocal diagnosis and its potential in facilitating individually tailored management is also highlighted.