Maternal Body Mass Index and Risk of Bronchopulmonary Dysplasia in Extremely Preterm Infants

OBJECTIVE

 We evaluated the relationship between maternal body mass index (BMI) and death or bronchopulmonary dysplasia (BPD). We hypothesized that in extremely low birth weight (ELBW; BW < 1,000 g) infants, the risk of death or BPD would be greater if the maternal BMI deviated further from the ideal BMI of 24.

STUDY DESIGN

 ELBW infants admitted to AdventHealth Neonatal Intensive Care Unit (NICU) between calendar years 2012 and 2017 were included in this retrospective observational study. BPD was defined as continuous supplemental oxygen use at 36 weeks post-menstrual age.

RESULT

 There was no association between the deviation of maternal BMI from the ideal of 24 and the composite outcome of death or BPD (6.9 ± 6.7 vs. 7.06 ± 6.6, pp = 0.966). However, there was a lower risk of death with a higher maternal BMI (p = 0.024). BPD was also associated with a higher maternal BMI (p = 0.045).

CONCLUSION

 Maternal BMI was not associated with the composite variable of death or BPD in ELBW infants. The lack of association was due to the contrast between high BMI and a lower risk of death and a higher risk for BPD.

KEY POINTS

· Maternal BMI was not associated with the composite outcome of death or BPD.. · Elevated BMI was associated with a higher risk of BPD.. · Elevated BMI was associated with a lower risk of death..

Early evolutionary divergence between papillary and anaplastic thyroid cancers

Background

Papillary thyroid cancer (PTC) is the most common thyroid carcinoma and exhibits an almost uniformly good prognosis, while anaplastic thyroid cancer (ATC) is less frequent and is one of the most aggressive cancers usually resistant to conventional treatment. Current hypothesis posits that ATC derives from PTC through the progressive acquisition of a discrete number of genomic alterations and implies that the mutational landscape of ATC resembles that of PTC. However, the clinical behaviour of ATC and PTC is radically different. We decided to address the disconnection between the clinical behaviour of ATC and PTC and the proposed model of the progressive development of ATC from PTC.

Patients and methods

We carried out exome sequencing of DNA from 14 ATC specimens including three cases of concomitant ATC and PTC as well as their corresponding normal DNA from 14 patients. The sequencing results were validated using droplet digital PCR. We carried out immunohistochemistry and immunofluorescence studies of the concomitant ATC and PTC cases. In addition, we integrated our sequencing results with the existing TCGA data.

Results

Most of the somatic mutations identified in the ATC component differed from the ones in PTC in the cases of concomitant ATC and PTC. The trunks of the phylogenetic trees representing the somatic mutations were short with long branches. In one case of concomitant PTC and ATC specimens, we observed an infiltration of PTC cells within the ATC component. Moreover, we integrated our results with data obtained from TCGA and observed that the most frequent mutations found in ATC presented high cancer cell fraction values and were significantly different from the PTC ones.

Conclusion

ATC diverge from PTC early in tumour development and both tumour types evolve independently. Our work allows the understanding of the relationship between ATC and PTC facilitating the clinical management of these malignancies.

Short-term outcome of psychogenic non-epileptic seizures after communication of the diagnosis

We previously described a communication strategy for the delivery of the diagnosis of psychogenic non-epileptic seizures (PNES) that was acceptable and effective at communicating the psychological cause of PNES. This prospective multicenter study describes the short-term seizure and psychosocial outcomes after the communication of the diagnosis and with no additional treatment. Participants completed self-report measures at baseline, two and six months after the diagnosis (seizure frequency, HRQoL, health care utilization, activity levels, symptom attributions and levels of functioning). Thirty-six participants completed the self-report questionnaires. A further eight provided seizure frequency data. After six months, the median seizure frequency had dropped from 10 to 7.5 per month (p=0.9), 7/44 participants (16%) were seizure-free, and an additional 10/44 (23%) showed greater than 50% improvement in seizure frequency. Baseline questionnaire measures demonstrated high levels of impairment, which had not improved at follow-up. The lack of change in self-report measures illustrates the need for further interventions in this patient group.

Recombinant human parainfluenza virus type 2 with mutations in V that permit cellular interferon signaling are not attenuated in non-human primates

The HPIV2 V protein inhibits type I interferon (IFN) induction and signaling. To manipulate the V protein, whose coding sequence overlaps that of the polymerase-associated phosphoprotein (P), without altering the P protein, we generated an HPIV2 virus in which P and V are expressed from separate genes (rHPIV2-P+V). rHPIV2-P+V replicated like HPIV2-WT in vitro and in non-human primates. HPIV2-P+V was modified by introducing two separate mutations into the V protein to create rHPIV2-L101E/L102E and rHPIV2-Delta122-127. In contrast to HPIV2-WT, both mutant viruses were unable to degrade STAT2, leaving virus-infected cells susceptible to IFN. Neither mutant, nor HPIV2-WT, induced significant amounts of IFN-beta in infected cells. Surprisingly, neither rHPIV2-L101E/L102E nor rHPIV2-Delta122-127 was attenuated in two species of non-human primates. This indicates that loss of HPIV2's ability to inhibit IFN signaling is insufficient to attenuate virus replication in vivo as long as IFN induction is still inhibited.

Long-range epigenetic silencing at 2q14.2 affects most human colorectal cancers and may have application as a non-invasive biomarker of disease

Large chromosomal regions can be suppressed in cancer cells as denoted by hypermethylation of neighbouring CpG islands and downregulation of most genes within the region. We have analysed the extent and prevalence of long-range epigenetic silencing at 2q14.2 (the first and best characterised example of coordinated epigenetic remodelling) and investigated its possible applicability as a non-invasive diagnostic marker of human colorectal cancer using different approaches and biological samples. Hypermethylation of at least one of the CpG islands analysed (EN1, SCTR, INHBB) occurred in most carcinomas (90%), with EN1 methylated in 73 and 40% of carcinomas and adenomas, respectively. Gene suppression was a common phenomenon in all the tumours analysed and affected both methylated and unmethylated genes. Detection of methylated EN1 using bisulfite treatment and melting curve (MC) analysis from stool DNA in patients and controls resulted in a predictive capacity of, 44% sensitivity in positive patients (27% of overall sensitivity) and 97% specificity. We conclude that epigenetic suppression along 2q14.2 is common to most colorectal cancers and the presence of a methylated EN1 CpG island in stool DNA might be used as biomarker of neoplastic disease.

Xiro-1 controls mesoderm patterning by repressing bmp-4 expression in the Spemann organizer

The Iroquois genes code for homeodomain proteins that have been implicated in the neural development of Drosophila and vertebrates. We show here for the first time that Xiro-1, one of the Xenopus Iroquois genes, is expressed in the Spemann organizer from the start of gastrulation and that its overexpression induces a secondary axis as well as the ectopic expression of several organizer genes, such as chordin, goosecoid, and Xlim-1. Our results also indicate that Xiro-1 normally functions as a transcriptional repressor in the mesoderm. Overexpression of Xiro-1 or a chimeric form fused to the repressor domain of Engrailed cause similar phenotypes while overexpression of functional derivatives of Xiro-1 fused with transactivation domains (VP16 or E1A) produce the opposite effects. Finally, we show that Xiro-1 works as a repressor of bmp-4 transcription and that its effect on organizer development is dependent on BMP-4 activity. We propose that the previously observed down regulation of bmp-4 in the dorsal mesoderm during gastrulation can be explained by the repressor activity of Xiro-1 described here. Thus, Xiro-1 seems to have at least two different functions: control of neural plate and organizer development, both of which could be mediated by repression of bmp-4 transcription.

Calcium mediates dorsoventral patterning of mesoderm in Xenopus

Calcium signals participate in the differentiation of electrically excitable and nonexcitable cells; one example of this differentiation is the acquisition of mature neuronal phenotypes. For example, transient elevations of the intracellular calcium concentration have been recorded in the ectoderm of early embryos, and this elevation has been proposed to participate in neural induction. Here, we present molecular evidence indicating that voltage-sensitive calcium channels (VSCC) are involved in early developmental processes leading to the establishment of the dorsoventral (D-V) patterning of a vertebrate embryo. We report that alpha1S VSCC are expressed selectively in the dorsal marginal zone at the early gastrula stage. The expression of the VSCC correlates with elevated intracellular calcium levels, as evaluated by the fluorescence of the intracellular calcium indicator Fluo-3. Misexpression of VSCC leads to a strong dorsalization of the ventral marginal zone and induction of the secondary axis but no direct neuralization of the ectoderm. Moreover, specific inhibition of VSCC by the use of calcicludine results in ventralization of the dorsal mesoderm. Together, these results indicate that calcium channels regulate mesodermal patterning by specificating the D-V identity of the mesodermal cells. The D-V patterning of the mesoderm has been shown to depend on a gradient of BMPs activity. We discuss the possibility that VSCC affect or act downstream of BMPs activity.

Induction and development of neural crest in Xenopus laevis

Neural crest cells are a migratory embryonic cell population that form at the border between the neural plate and the future epidermis. This border, the neural plate border, corresponds to the neural fold. The neural fold surrounds the entire neural plate, but only the lateral and posterior portions of the fold give rise to neural crest cells, while the anterior neural fold differentiates as forebrain. This review focuses on neural crest development in Xenopus laevis embryos, and analyzes aspects of the induction of the neural crest in Xenopus, summarizing available information relating to the expression of several genes in the neural crest. Two models for neural crest induction are discussed. In the first model, the neural crest is induced by the interaction between the neural plate and the epidermis. In the second, the specification of the neural plate border arises as a consequence of a gradient of BMP activity. The role of posteriorizing signals on neural crest specification is also discussed. Finally, we propose that the specification and differentiation of the neural crest is controlled by a cascade of transcription factors, encoded and expressed from a hierarchy of genes. A set of extracellular signals establishes the positional information in the ectoderm, which activates Prepattern genes (Gli, Xiro, Zic, Dlx, etc.) across extended and overlapping domains. A local combination of these genes at the neural plate border activates the cascade of neural crest specification, while different sets of genes are activated at both sides of the neural folds (in the epidermis and the neural plate). The genes activated in regions adjacent to the neural plate border have an inhibitory effect on the neural crest transcription program.

A novel function for the Xslug gene: control of dorsal mesendoderm development by repressing BMP-4

The Snail family of genes comprise a group of transcription factors with characteristic zinc finger motifs. One of the members of this family is the Slug gene. Slug has been implicated in the development of neural crest in chick and Xenopus by antisense loss of function experiments. Here, we have generated functional derivatives of Xslug by constructing cDNAs that encode the Xslug protein fused with the transactivation domain of the virus-derived VP16 activator or with the repressor domain of the Drosophila Engrailed protein. Our results suggest that Xslug normally functions as a transcriptional repressor and that Xslug-VP16 behaves as a dominant negative of Xslug. In the present work, we confirm and extend previous results that suggest that Xslug has an important function in neural crest development, by controlling its own transcription. In addition we have uncovered a new function for Xslug. We show that Xslug is expressed in the dorsal mesendoderm at the beginning of gastrulation, where is it able to upregulate the expression of dorsal genes. On the other hand when Xslug is expressed outside of the organizer it represses the expression of ventral genes. Our results indicate that this effect on mesodermal patterning depends on BMP activity, showing that Xslug can directly control the transcription of BMP-4.

Relationship between gene expression domains of Xsnail, Xslug, and Xtwist and cell movement in the prospective neural crest of Xenopus

The markers Xslug, Xsnail, and Xtwist all are expressed in the presumptive neural folds and are thought to delineate the presumptive neural crest. However, their interrelationship and relative spatiotemporal distributions are not well understood. Here, we present a detailed in situ hybridization analysis of the relative patterns of expression of these transcription factors from gastrulation through neurulation and post-neural crest migration. The three genes mark the prospective neural crest and roof plate, coming on sequentially, with Xsnail preceding Xslug preceding Xtwist. By combining gene expression analysis with a fate map of the same region using DiI labeling, we determined the correspondence between early and late domains of gene expression. At the beginning of gastrulation, Xsnail is present in a unique domain of expression in a lateral region of the embryo in both superficial and deep layers of the ectoderm, as are Xslug and Xtwist. During gastrulation and neurulation, the superficial layer moves faster toward the dorsal midline than the deep layer, producing a relative shift in these cell populations. By early neurula stage, the Xsnail domain is split into a medial domain in the superficial ectoderm (fated to become the roof plate) and a lateral domain in the deep layer of the ectoderm (fated to become neural crest). Xsnail is down-regulated in the most anterior neural plate and up-regulated in the posterior neural plate. Our results show that changes in the expression of Xsnail, Xslug, and Xtwist are a consequence of active cell movement in some regions coupled with dynamic changes in gene expression in other regions.

Development of neural crest in Xenopus

The neural crest is a unique cell population among embryonic cell types, displaying properties of both ectodermal and mesodermal lineages. Most of the recent studies examining the neural crest have been performed in avian embryos. Only in the first half of this century were amphibians extensively used. We first summarize this important older source of information, reviewing studies made since the turn of the century. Due to the increasingly detailed in cellular and molecular knowledge of the early development of Xenopus laevis, the remainder of the review focuses on this species. We describe the route of migration and fate of the neural crest and propose a new model of neural crest induction in which prospective cells are induced independently of the neural plate by a double gradient of a morphogen that patterns the entire ectoderm. This model is also discussed in a more general context in connection with the dorsoventral patterning of the neural tube. Finally, we discuss some ideas concerning neural crest evolution and propose a novel hypothesis about its phylogenetic origin.

Xenopus brain factor-2 controls mesoderm, forebrain and neural crest development

The forkhead type Brain Factor 2 from mouse and chicken help pattern the forebrain, optic vesicle and kidney. We have isolated a Xenopus homolog (Xbf2) and found that during gastrulation it is expressed in the dorsolateral mesoderm, where it helps specify this territory by downregulating BMP-4 and its downstream genes. Indeed, Xbf2 overexpression caused partial axis duplication. Interference with BMP-4 signaling also occurs in isolated animal caps, since Xbf2 induces neural tissue. Within the neurula forebrain, Xbf2 and the related Xbf1 gene are expressed in the contiguous diencephalic and telencephalic territories, respectively, and each gene represses the other. Finally, Xbf2 seems to participate in the control of neural crest migration. Our data suggest that XBF2 interferes with BMP-4 signaling, both in mesoderm and ectoderm.

The inductive properties of mesoderm suggest that the neural crest cells are specified by a BMP gradient

We have analyzed the role of mesoderm in the induction of the neural crest in Xenopus using expression of neural plate (Xsox-2) and neural crest (Xslug and ADAM). Conjugation experiments using different kinds of mesoderm together with embryonic dissection experiments suggest that the dorsolateral mesoderm is capable of specifically inducing neural crest cells. Neural crest markers can be induced in competent ectoderm at varying distances from the inducing mesoderm, with dorsal tissue inducing neural crest at a distance while dorsolateral tissue only induces neural crest directly in adjacent ectoderm. The results suggest that dorsal mesoderm has a high level of inducer and dorsolateral mesoderm has a lower level, consistent with a inductive gradient. We explored the possible role of BMP and noggin in the generation of such a hypothetical gradient and found that: (1) progressively higher levels of BMP activity are sufficient for the specification of neural plate, neural crest, and nonneural cells, respectively; (2) progressively higher levels of noggin are able to induce neural crest at greater distances from the source of inducer; and (3) modification of the levels of BMP activity causes induction of the neural crest in absence of neural plate, suggesting independent induction of these two tissues. We propose a model in which a gradient of BMP activity is established in the ectoderm by interaction between BMP in the ectoderm and BMP inhibitors in the mesoderm. Neural crest is induced when a threshold level of BMP is attained in the ectoderm. The dorsolateral mesoderm produces either BMP inhibitors or a specific neural crest inducer, with low BMP activity inducing neural plate while high BMP activity induces epidermis.

Inhibition of mesoderm formation by follistatin

Mesoderm induction requires interaction between cells of the animal and vegetal hemispheres of the embryo. Several molecules have been proposed as candidates for mesoderm-inducing signals, with activin a particularly strong candidate. However, it has not been possible to inhibit mesoderm formation in vivo by specifically blocking activin action. Follistatin is able to inhibit the action of activin but not that of the mature region of Vg1, a member of the transforming growth factor beta family. Follistatin therefore provides a useful tool for distinguishing between signalling by these two factors. We have overexpressed Xenopus follistatin mRNA and analysed the expression of several mesodermal markers. Our results show an inhibition of mesodermal formation by follistatin in a concentration-dependent manner, showing the requirement of activin for mesodermal induction.

Xiro, a Xenopus homolog of the Drosophila Iroquois complex genes, controls development at the neural plate

The Drosophila homeoproteins Ara and Caup are members of a combination of factors (prepattern) that control the highly localized expression of the proneural genes achaete and scute. We have identified two Xenopus homologs of ara and caup, Xiro1 and Xiro2. Similarly to their Drosophila counterparts, they control the expression of proneural genes and, probably as a consequence, the size of the neural plate. Moreover, Xiro1 and Xiro2 are themselves controlled by noggin and retinoic acid and, similarly to ara and caup, they are overexpressed by expression in Xenopus embryos of the Drosophila cubitus interruptus gene. These and other findings suggest the conservation of at least part of the genetic cascade that regulates proneural genes, and the existence in vertebrates of a prepattern of factors important to control the differentiation of the neural plate.

Role of FGF and noggin in neural crest induction

A study of the molecules noggin and fibroblast growth factor (FGF) and its receptor in the induction of the prospective neural crest in Xenopus laevis embryos has been carried out, using the expression of the gene Xslu as a marker for the neural crest. We show that when a truncated FGF receptor (XFD) was expressed ectopically in order to block FGF signaling Xslu expression was inhibited. The effect of XFD on Xslu was specific and could be reversed by the coinjection of the wild-type FGF receptor (FGFR). Inhibition of Xslu expression by XFD is not a consequence of neural plate inhibition, as was shown by analyzing Xsox-2 expression. When ectoderm expressing XFD was transplanted into the prospective neural fold region of embryos Xslu induction was inhibited. The neural crest can also be induced by an interaction between neural plate and epidermis. As this induction is suppressed by the presence of XFD in the neural plate and not in the epidermis, it suggests that the neural crest is induced by FGF from the epidermis. However, treatment of neural plate with FGF was not able to induce Xslug expression, showing that in addition to FGF other non-FGF factors are also required. Previously we have suggested that the ectopic ventral expression of Xslu produced by overexpression of noggin mRNA resulted from an interaction of noggin with a ventral signal. Overexpression of XFD inhibits this effect, suggesting that FGF could be one component involved in this ventral signaling. Overexpression of FGFR produced a remarkable increase in the expression of Xslu in the posterior neural folds and around the blastopore. Injections in different blastomeres of the embryo suggest that the target cells of this effect are the ventral cells. Finally, we proposed a model in which the induction of the neural crests at the border of the neural plate requires functional FGF signaling, which possibly interacts with a neural inducer such as noggin.

Neural crest formation in Xenopus laevis: mechanisms of Xslug induction

A study of the induction of the prospective neural crest in Xenopus laevis embryos has been carried out, using the expression of Xslug as a specific marker for the neural crest. We have analyzed the competence and the specification of the neural crest. The competence to express Xslug was analyzed using two different approaches: (1) in vitro culture of conjugates of dorsal mesoderm and ectoderm taken from embryos at different ages and (2) grafts of equivalent pieces of ectoderm in the neural fold region of a gastrula or a neurula. Similar results were obtained with both methods: the ectoderm loses the competence to respond to neural fold induction at the end of gastrulation. Neural crest specification was analyzed by culturing a region of the ectoderm that contained the prospective neural crest and analyzing Xslug expression. Our results show that neural folds are specified autonomously to express Xslug by the end of gastrulation. By grafting labeled neural plate into lateral epidermis we have shown that neural crest can be induced by an interaction between neural plate and epidermis. Furthermore, neural crest cells come from both tissues. We have discarded the possibility that these neural crest cells are induced by a signal coming from the underlying lateral plate, by a homeogenetic signal coming from the host neural plate, or by regeneration of crest cells from the dissected neural plate. We propose a model to explain how the neural crest cells are induced at the border of the neural plate in X. laevis.

Induction of the prospective neural crest of Xenopus

The earliest sign of the prospective neural crest of Xenopus is the expression of the ectodermal component of Xsna (the Xenopus homologue of snail) in a low arc on the dorsal aspect of stage 11 embryos, which subsequently assumes the horseshoe shape characteristic of the neural folds as the convergence-extension movements shape the neural plate. A related zinc-finger gene called Slug (Xslu) is expressed specifically in this tissue (i.e. the prospective crest) when the convergence extension movements are completed. Subsequently, Xslu is found in pre- and post-migratory cranial and trunk neural crest and also in lateral plate mesoderm after stage 17. Both Xslu and Xsna are induced by mesoderm from the dorsal or lateral marginal zone but not from the ventral marginal zone. From stage 10.5, explants of the prospective neural crest, which is underlain with tissue, are able to express Xslu. However expression of Xsna is not apparently specified until stage 12 and further contact with the inducer is required to raise the level of expression to that seen later in development. Xslu is specified at a later time. Embryos injected with noggin mRNA at the 1-cell stage or with plasmids driving noggin expression after the start of zygotic transcription express Xslu in a ring surrounding the embryo on the ventroposterior side. We suggest this indicates (a) that noggin interacts with another signal that is present throughout the ventral side of the embryo and (b) that Xslu is unable to express in the neural plate either because of the absence of a co-inducer or by a positive prohibition of expression. The ventral co-inducer, in the presence of overexpressed noggin, seems to generate an anterior/posterior pattern in the ventral part of the embryo comparable to that seen in neural crest of normal embryos. We suggest that the prospective neural crest is induced in normal embryos in the ectoderm that overlies the junction of the domains that express noggin and Xwnt-8. In support of this, we show animal cap explants from blastulae and gastrulae, treated with bFGF and noggin express Xslu but not NCAM although the mesoderm marker Xbra is also expressed. Explants treated with noggin alone express NCAM only. An indication that induction of the neural plate border is regulated independently of the neural plate is obtained from experiments using ultraviolet irradiation in the precleavage period. At certain doses, the cranial crest domains are not separated into lateral masses and there is a reduction in the size of the neural plate.

Morulae at compaction and the pattern of protein synthesis in mouse embryos

Compaction of mouse embryos at the 8-cell stage causes a drastic change in cell form and in cell-to-cell contacts in 3-4 h. We have studied the effect of inhibitors of transcription (alpha-amanitin), DNA replication (aphidicolin) and compaction (cytochalasin D, EGTA, alpha-lactalbumin and Con A) on the pattern of protein synthesis using gel electrophoresis. Our results show that the pattern of protein synthesis is regulated principally by passage through S phase during each early cell cycle rather than by de novo transcription, while changes induced in cell form or contacts do not alter the pattern significantly.

Distinct elements of the xsna promoter are required for mesodermal and ectodermal expression

Xsna, the Xenopus homologue of Drosophila snail, is expressed in both mesoderm and ectoderm. Expression occurs in all mesoderm initially but is down regulated in a tissue-specific fashion at the end of gastrulation in a way that reveals the subdivision of the mesoderm before its derivatives are overtly differentiated. Xsna is also expressed in the ectoderm of the prospective neural fold from stage 11, in a distinct band of cells surrounding the prospective neural plate, which we designate the neural plate border. The deep and superficial ectoderm compartments labelled by Xsna represent the prospective neural crest and the prospective roof of the neural tube, respectively. Xsna expression persists in neural crest cells during their subsequent migration. The role of the Xsna promoter in creating this pattern of expression has been investigated by injecting fertilised eggs with constructs containing the 5′ upstream sequence of the gene fused to a reporter. An element of 115 base pairs (−160 to −45 relative to the transcriptional start) is sufficient to drive appropriate reporter gene expression. The promoter does not contain a TATA or CAAT box and does not have a high GC content, but RNA synthesis starts precisely at 33 bases upstream to the translational start. The start sequence can be deleted so that transcription is initiated elsewhere without affecting the expression pattern. The distribution of Xsna promoter activity within the embryo, examined using beta-galactosidase (beta-gal) fusions, is similar to that of the endogenous mRNA seen by in situ hybridisation. The contribution of elements within the 5′ sequence have been assessed by comparing the expression patterns of constructs that have deletions in this region. Sequences from −112 to −97 are required for mesodermal expression and sequences from −96 to −44 are required for ectodermal expression. The behaviour of the injected promoter constructs differ in one important respect from the endogenous gene in that expression in an animal cap assay is not inducible by mesoderm-inducing factors but is inducible by cells of the vegetal pole.

Expression of Xenopus snail in mesoderm and prospective neural fold ectoderm

Expression of the Xsna gene during Xenopus laevis embryogenesis has been analysed by in situ hybridisation. Like its homologue snail in Drosophila, Xsna is expressed zygotically in all early mesoderm. Expression starts during stage 9 in the dorsal marginal zone and spreads to the ventral side by stage 10. During gastrulation, each cell begins to express as it involutes so that cells newly expressing Xsna are added to the forming mesoderm mantle in an anterior-to-posterior progression. Xsna expression is then down-regulated in a tissue-specific fashion that reveals the subdivision of the mesoderm before its derivatives are overtly differentiated; e.g., the appearance of the notochord, myotomes, and pronephroi are preceded by the disappearance of Xsna mRNA, while undifferentiated mesoderm remains labelled, even into tadpole stages. Xsna is expressed in the suprablastoporal endoderm during gastrulation and in its derivatives, the prechordal and sub-notochordal endoderm, during neurulation. Relationships between Xbra, Xtwi, and Xsna expression are examined. Xsna is also expressed in the prospective neural fold ectoderm from stage 11 in a low arc above the dorsal marginal zone, precisely identifying a distinct band of cells that surrounds the prospective neural plate that we designate the neural plate border. The anterior transverse neural fold, which becomes forebrain, ceases Xsna expression during neurulation. In the longitudinal neural folds, the deep and superficial ectoderm compartments labelled by Xsna expression are the prospective neural crest and prospective roof of the neural tube, respectively. Xsna expression persists in the neural crest during migration and in some derivatives at least until metamorphosis but ceases in the roof of the neural tube soon after neurulation.

Precipitated diazepam withdrawal elevates noradrenergic metabolism in primate brain

Following treatment for seven days with diazepam (2.0 mg/kg i.m., b.i.d.), administration of the benzodiazepine receptor antagonist RO 15-1788 (5 mg/kg) induced a severe withdrawal syndrome in vervet monkeys which included tremors, vomiting, vocalizations, chewing, and piloerection. Brain concentrations of the noradrenergic metabolite 3-methoxy-4-hydroxyphenylglycol (MHPG) were significantly higher in the precipitated withdrawal group than in the diazepam plus vehicle control group. Administration of RO 15-1788 without prior diazepam treatment had no effect on brain MHPG, nor did it produce withdrawal behaviors, but did produce an increase in the frequency of scratching. These results raise the possibility that increased central noradrenergic activity serves a role in benzodiazepine withdrawal similar to the role hypothesized for noradrenergic activity in opiate withdrawal.