Totally tubular: the mystery behind function and origin of the brain ventricular system

A unique feature of the vertebrate brain is the ventricular system, a series of connected cavities which are filled with cerebrospinal fluid (CSF) and surrounded by neuroepithelium. While CSF is critical for both adult brain function and embryonic brain development, neither development nor function of the brain ventricular system is fully understood. In this review, we discuss the mystery of why vertebrate brains have ventricles, and whence they originate. The brain ventricular system develops from the lumen of the neural tube, as the neuroepithelium undergoes morphogenesis. The molecular mechanisms underlying this ontogeny are described. We discuss possible functions of both adult and embryonic brain ventricles, as well as major brain defects that are associated with CSF and brain ventricular abnormalities. We conclude that vertebrates have taken advantage of their neural tube to form the essential brain ventricular system.     

Marshall J. Edwards: discoverer of maternal hyperthermia as a human teratogen

In a series of animal studies performed over a career spanning 40 years at the University of Sydney, Professor Marshall J. Edwards investigated the hypothesis that maternal hyperthermia during gestation can be teratogenic to the developing fetus. He is one of few investigators to have discovered a known human teratogen primarily through animal studies. In 1970 he earned his Ph.D. from the University of Sydney, writing a doctoral thesis entitled "A Study of Some Factors Affecting Fertility of Animals with Particular Reference to the Effects of Hyperthermia on Gestation and Prenatal Development of the Guinea-Pig." He went on to prove that hyperthermia-induced malformations in animals involve many organs and structures, particularly the central nervous system. Other defects include craniofacial anomalies, heart defects and hypodactyly, cataracts and coloboma, kyphoscoliosis, renal anomalies, dental agenesis, and abdominal wall defects. In a series of carefully planned and executed experiments, he demonstrated that the type of defect is related to the timing of the hyperthermic insult, and analyzed the underlying mechanisms. Cell death, membrane disruption, vascular disruption, and placental infarction were all implicated in causing embryonic damage. This special article reviews the scientific discoveries and personal philosophy of Marshall J. Edwards, the discoverer of maternal hyperthermia as a human teratogen.     

Mouse as a model for multifactorial inheritance of neural tube defects

Neural tube defects (NTDs) such as spina bifida and anencephaly are some of the most common structural birth defects found in humans. These defects occur due to failures of neurulation, a process where the flat neural plate rolls into a tube. In spite of their prevalence, the causes of NTDs are poorly understood. The multifactorial threshold model best describes the pattern of inheritance of NTDs where multiple undefined gene variants interact with environmental factors to cause an NTD. To date, mouse models have implicated a multitude of genes as required for neurulation, providing a mechanistic understanding of the cellular and molecular pathways that control neurulation. However, the majority of these mouse models exhibit NTDs with a Mendelian pattern of inheritance. Still, many examples of multifactorial inheritance have been demonstrated in mouse models of NTDs. These include null and hypomorphic alleles of neurulation genes that interact in a complex fashion with other genetic mutations or environmental factors to cause NTDs. These models have implicated several genes and pathways for testing as candidates for the genetic basis of NTDs in humans, resulting in identification of putative pathogenic mutations in some patients. Mouse models also provide an experimental paradigm to gain a mechanistic understanding of the environmental factors that influence NTD occurrence, such as folic acid and maternal diabetes, and have led to the discovery of additional preventative nutritional supplements such as inositol. This review provides examples of how multifactorial inheritance of NTDs can be modeled in the mouse. Birth Defects Research (Part C) 96:193–205, 2012. © 2012 Wiley Periodicals, Inc.     

Prevalence of periconceptional folic acid use and perceived barriers to the postgestation continuance of supplemental folic acid: survey results from a Teratogen Information Service

BACKGROUND: Fewer than 40% of U.S. women are taking folic acid supplements periconceptionally at a time when the risk of neural tube defects (NTDs) can be reduced by supplementation. A better understanding of the vitamin-taking habits of childbearing-age women and effective methods for improving periconceptional supplement use are needed. METHODS: A telephone survey conducted through the California Teratogen Information Service (TIS) between August 2003 and January 2004 assessed the prevalence and characteristics of pregnant callers who did not use folic acid supplements in the periconceptional period, and explored attitudes toward advice to continue vitamin use following pregnancy in order to be protected in a future pregnancy. RESULTS: A total of 327 pregnant women who called the TIS for information agreed to participate in the survey. More than half (53.2%) were not taking folic acid-containing supplements in the periconceptional period. Predictors of lack of use included a higher prepregnancy body mass index, younger maternal age, non-white race/ethnicity, lower education level, and unplanned pregnancy. One-quarter of the women said they would be willing to continue taking vitamins after the pregnancy if advised to do so by a physician. The remainder identified obstacles to following that advice--notably, not planning to become pregnant again and the belief that enough folate is derived from diet alone. CONCLUSIONS: More than half of the callers to the TIS were not compliant with recommendations regarding periconceptional folic acid supplementation. This represents an opportunity for TIS specialists and physicians to intervene in a current pregnancy to encourage maintenance of supplement use in the subsequent interpregnancy interval.     

Xenopus leads the way: Frogs as a pioneering model to understand the human brain

From its long history in the field of embryology to its recent advances in genetics, Xenopus has been an indispensable model for understanding the human brain. Foundational studies that gave us our first insights into major embryonic patterning events serve as a crucial backdrop for newer avenues of investigation into organogenesis and organ function. The vast array of tools available in Xenopus laevis and Xenopus tropicalis allows interrogation of developmental phenomena at all levels, from the molecular to the behavioral, and the application of CRISPR technology has enabled the investigation of human disorder risk genes in a higher‐throughput manner. As the only major tetrapod model in which all developmental stages are easily manipulated and observed, frogs provide the unique opportunity to study organ development from the earliest stages. All of these features make Xenopus a premier model for studying the development of the brain, a notoriously complex process that demands an understanding of all stages from fertilization to organogenesis and beyond. Importantly, core processes of brain development are conserved between Xenopus and human, underlining the advantages of this model. This review begins by summarizing discoveries made in amphibians that form the cornerstones of vertebrate neurodevelopmental biology and goes on to discuss recent advances that have catapulted our understanding of brain development in Xenopus and in relation to human development and disease. As we engage in a new era of patient‐driven gene discovery, Xenopus offers exceptional potential to uncover conserved biology underlying human brain disorders and move towards rational drug design.     

High prevalence of NTDs in Shanxi Province: a combined epidemiological approach

BACKGROUND: Shanxi Province has historically reported a high prevalence of NTDs. In order to establish baseline rates for NTDs and discuss the risk factors associated with sociodemographic, maternal characteristics, and geographic factors, we performed the present study using an approach combining population and hospital-based methodologies. METHODS: We used chi(2) and Fisher's exact tests to evaluate variation in the prevalence by selected covariates and computed crude ORs and 95% CIs. Adjusted odds ratios (AORs) were performed using logistic regression with all the covariates included in the model. RESULTS: The overall NTD prevalence during the 3 year study period was 199.38 per 10,000 births, with a higher NTD prevalence clustered in 46 villages within this geographic area. However, no statistical significance was found between NTD prevalence and the elevation of the villages or their distance from coal plants. AORs revealed women aged 20 and above had a lower risk of NTDs compared to those younger than 20 (AOR range 0.4-0.5). A higher risk of NTDs was observed among female infants (AOR 1.50; 95% CI: 1.04-2.17), women with four or more previous births (AOR 2.80; 95% CI: 1.20-6.52), and a previous history of birth defects (AOR 3.23; 95% CI: 1.46-7.12). CONCLUSIONS: This study has documented a high prevalence of NTDs in Shanxi. Similar variations to other reports were found in the risk of NTDs by maternal demographic characteristics and a clustering of NTDs in certain villages that require further exploration.     

Plasma vitamin values and antiepileptic therapy: case reports of pregnancy outcomes affected by a neural tube defect

BACKGROUND: Folic acid supplementation reduces the occurrence of neural tube defects (NTDs); however, it is not clear whether it protects against teratogenic effects of antiepileptic drugs. METHODS: We report the cases of four pregnant women receiving valproic acid therapy, who all had NTD-affected offspring, despite periconceptional 5 mg/day of folic acid supplementation (cases), and investigated homocysteine metabolism, linked with folate metabolism. Their plasma homocysteine, folates, and vitamin B6 and B12 results were compared with values of two other women, who were also receiving valproic acid and folic acid complement, but who had normal pregnancies (valproic acid controls), and values of 40 pregnant women who had normal pregnancies and were not receiving any therapy (controls without therapy). Because of the possible existence of a genetic susceptibility, polymorphisms in homocysteine metabolism were sought. RESULTS: Two cases showed a decreased phosphopyridoxal level, compared with levels in the controls not receiving therapy. The genotype TT (C677T) is an NTD genetic susceptibility, but it was observed in only one valproic acid control. Various polymorphisms were observed in the cases, but were also common in the controls. Several studies have reported that valproic acid therapy lowers vitamin B6 levels. Our case with the greatest decrease in plasma phosphopyridoxal, who was taking periconceptional folic acid plus pyridoxine therapy, had a normal second pregnancy outcome. CONCLUSIONS: In addition to folates, other vitamins, such as vitamin B6, may have played a role in NTDs in our patients taking an antiepileptic drug.     

The effect of fever, febrile illnesses, and heat exposures on the risk of neural tube defects in a Texas-Mexico border population

BACKGROUND: Hyperthermia produces neural tube defects (NTDs) in a variety of animal species. Elevated maternal body temperatures may also place the developing human embryo at risk. We examined the relation between maternal hyperthermia and the development of NTDs in a high-risk Mexican-American population. METHODS: Case-women were Mexican-American women with NTD-affected pregnancies who resided and delivered in any of the 14 Texas counties bordering Mexico, during 1995-2000. Control-women were randomly selected from study area residents delivering normal live births, frequency-matched to cases by hospital and year. Information on maternal fevers, febrile illnesses, exposures to heat generated from external sources, and hyperthermia-inducing activities was gathered through in-person interviews, conducted about six weeks postpartum. RESULTS: The risk effect (OR) associated with maternal fever in the first trimester, compared to no fever, was 2.9 (95% CI, 1.5-5.7). Women taking fever-reducing medications showed a lower risk effect (OR, 2.4; 95% CI, 1.0-5.6) than those who did not (OR, 3.8; 95% CI, 1.4-10.9). First-trimester maternal exposures to heat devices such as hot tubs, saunas, or electric blankets were associated with an OR of 3.6 (95% CI, 1.1-15.9). Small insignificant effects were observed for activities such as cooking in a hot kitchen (OR, 1.6; 95% CI, 1.0-2.6) and working or exercising in the sun (OR, 1.4; 95% CI, 0.9-2.2). CONCLUSIONS: Maternal hyperthermia increases the risk for NTD-affected offspring. Women intending to become pregnant should avoid intense heat exposures, carefully monitor and manage their febrile illnesses, and routinely consume folic acid supplements.     

Neural tumours of the neck presenting as thyroid nodules: a report of three cases

OBJECTIVES: Neural tumours of the neck may at times secondarily involve the thyroid and manifest clinically as thyroid nodules. On cytological evaluation these nodules may be confused with other spindle lesions of the thyroid. We report two cases of schwannoma and one case of a malignant peripheral nerve sheath tumour (MPNST) of the neck, which presented as thyroid nodules and evaluate the role of cytology in identifying these tumours. METHODS: The thyroid nodules in all the three cases were sampled by the non-aspiration technique using a 23-gauge needle. Both alcohol-fixed and air-dried smears were prepared and stained by the Papanicolaou and May-Grünwald-Giemsa stains. Cytology smears and histology sections from the resected specimens were reviewed, and the findings noted. RESULTS: Both the cases of schwannoma were correctly identified on cytology while the case of MPNST could only be typed as a spindle cell tumour. However, on cytology it was not possible to state whether the tumours were thyroidal or extrathyroidal in origin. CONCLUSIONS: Schwannomas of the neck are easily identifiable on cytology compared with MPNST. However, cytology alone is not helpful in identifying the origin of these tumours. As primary neural tumours of the thyroid are rare, the possibility of a soft tissue neural tumour extending into the thyroid should always be ruled out while evaluating these cases.     

Assessing the contributions of gene products to the form-shaping events of neurulation: a transgenic approach in chick

Most of our current knowledge on the tissue and cellular basis of neurulation in amniotes has been gained using the chick embryo as an experimental model system. Gene manipulation during chick neurulation has been difficult, greatly limiting our ability to assess the contribution of gene products to the tissue and cellular behaviors of neurulation. Using electroporation, we have developed a simple and reliable method for expressing transgenes in the ectoderm of the neural folds of chick embryos developing in whole-embryo culture. Sense- or antisense-expressing plasmids are electroporated, resulting in gain or loss of gene function, respectively. The morphogenesis of transgenic tissues was compared to the morphogenesis of contralateral wildtype tissues as neurulation was taking place. As a proof of principle, we present a functional analysis of the chick gene encoding Cartilage Linking Protein 1 (CRTL1), identified as a candidate neurulation gene using subtractive hybridization. This experimental approach provides a much-needed innovation for studying the mechanisms by which genes influence neurulation and reveals here important contributions of CRTL1 to the formation of the neural folds.     

Anatomy of a serial killer: differential diagnosis of tuberculosis based on rib lesions of adult individuals from the Coimbra Identified Skeletal Collection, Portugal

The role of new bone formation on visceral surfaces of ribs in the diagnosis of tuberculosis (TB) in past human populations has been explored by many researchers, using both skeletal remains with known causes of death and archaeological samples. This study focuses, firstly, on adult skeletons from the Coimbra Identified Skeletal Collection in Portugal and investigates the skeletal manifestations of individuals known to have died from TB; secondly, this study focuses on the role of rib lesions in the diagnostic criteria for TB. One hundred and fifty-seven males and 106 females aged between 22-87 years were examined; causes of death were assigned as pulmonary TB, extrapulmonary TB, and pulmonary non-TB; a control group, extrapulmonary non-TB, was selected from the remaining individuals. Of individuals with rib lesions, 85.7% (69/81) had pulmonary or extrapulmonary TB as an assigned cause of death, while 17.8% (16/90) of individuals with rib lesions had a non-TB cause of death. Rib lesions were significantly more common in individuals who had died from TB, although the lesions cannot be considered pathognomonic for TB. In individuals dying from pulmonary TB, ribs in the central part of the rib cage were most affected, at their vertebral ends. The lower part of the rib cage may be a marker for peritoneal TB, and "coral-like" new bone formation on ribs may be an indicator of neoplastic disease. Further work on rib involvement in TB in clinical contexts, and the study of further documented skeletal collections, are recommended.     

Electrical stimulation as an adjunct to spinal fusion: a meta-analysis of controlled clinical trials

This study was a meta-analysis to examine whether electrical stimulation has a specific effect on spinal fusion. Little evidence exists on the efficacy of electrical stimulation for improving fusion rate of spinal fusion surgery. Using MEDLINE (1966-2000) and EMBASE (1985-1999), a search for articles was carried out using the Medical Subject Headings: (1) electric stimulation or electromagnetic fields, (2) spinal fusion, (3) controlled or clinical trial, and (4) human. Data were extracted from all the hit articles and additionally collected from appropriate journal lists. A total of five randomized controlled trials (RCT) on bones assessing healing of spinal fusion were identified and scored on methodological quality. All the identified studies reported positive findings, but the quality score of each trial showed wide flaws. Because of relatively homogenous subjects who had spine fusion and radiographic assessment from these studies, pooling of the data was able to be performed. Excluding one trial with the lowest score, the combined results of four trials, whose major endpoints were the success rate of the fusion, revealed a statistically significant effect of electrical stimulation with various techniques, but the selected trials still showed wide variation in view of stimulation modalities and treatment protocol. The pooled result of the studies in this review revealed the efficacy of electrical stimulation based on proved methodological quality. As problems on therapeutic modality and protocol remain, there is a further need for improvement in design to constitute acceptable proof and to establish treatment programs that better demonstrate electrical stimulation effects on spinal fusion.     

Value of radiologically guided fine needle aspiration cytology (FNAC) in the diagnosis of spinal tuberculosis: a study of 29 cases

FNAC is a simple diagnostic tool for the initial evaluation of various deep seated pathological lesions. This study describes the applicability and practical aspects of the technique in establishing the diagnosis of spinal tuberculosis (TB) with the aid of radiographic guidance. The study was conducted in a major teaching hospital in Kuwait between the years 1985 and 1994. Twenty-nine patients (M:F = 18:11 and age range 8-72 years) with clinically and/or radiologically suspected spinal TB were seen in the Department of Cytology, Mubarak Al Kabeer Hospital. The patients were re-examined by either computed tomography (CT) scanning (n = 19) or fluoroscopy (n = 10) to localize the lesion for FNAC. FNAC smears were routinely stained with Papanicolaou and Diff Quik stains and one smear of each case was stained with Ziehl-Neelsen (Z-N) stain for acid-fast bacilli (AFB). Aspirated purulent material or syringe washings of dry aspirates were also submitted for microbiological cultures including AFB. Radiological and cytological findings were recorded in each case. Radiological findings included: bony rarefaction and destruction (93.1%), narrowed disc space (89.7%), soft tissue calcification (65.5%) and para-vertebral abscess formation (51.7%). Cytological findings included: epithelioid cell granulomas (89.7%), granular necrotic background (82.8%) and lymphocytic infiltration (75.9%). Smears were positive for AFB in 51.7% of cases. A positive AFB culture was obtained in 82.8% of cases, including all cases with positive AFB on smear by Z-N stain. Radiologically guided FNAC with AFB culture is a simple, reliable and practical approach to diagnosing spinal TB lesions. With a high diagnostic yield, it allows immediate initiation of specific treatment, helps to avoid invasive diagnostic procedures, and decreases hospitalization time.