Anaphylaxis to galacto-oligosaccharides--an evaluation in an atopic population in Singapore.

Anaphylaxis to galacto-oligosaccharides (GOS), a prebiotic, has been described in atopic patients following its supplementation in commercial milk formula in South-East Asia. The epidemiology of this usual allergy to a carbohydrate is unknown. This study evaluated the prevalence of allergy to two formulations of commercial GOS, Vivinal™ GOS (vGOS) and Oligomate™ , in an atopic cohort. Atopic subjects (n = 487) from two specialist allergy clinics were surveyed via structured questionnaire and underwent skin prick tests to GOS. Subjects with positive skin prick tests to GOS (n = 30, 6.2%) underwent basophil activation tests, and a subset (n = 13) underwent oral challenge tests to both formulations of GOS. Six subjects had positive challenges to vGOS; and none to Oligomate. By extrapolating the BAT and oral challenge results, the prevalence of allergy to vGOS is estimated at up to 3.5% (95% CI 2.2-5.5%) of our atopic population. Our findings show that GOS allergy may be common amongst atopics in Singapore.

Adolescent preventive health care: what do parents want?

OBJECTIVE: To understand parental opinions about which topics should be discussed during adolescent preventive health visits and how best to incorporate adolescent confidentiality into these visits. STUDY DESIGN: Cross-sectional, web-based survey of a national sample of 1025 parents of adolescents. RESULTS: Response rate was 71%. From a list of 18 possible topics, the 3 most frequently selected as being "very important for the doctor to discuss during adolescent well child examinations" were "diet/nutrition" (75%), "exercise/sports" (67%), and "physical changes of puberty" (60%). There was variability in topic popularity by parents' race/ethnicity and gender and by adolescents' age, health status, and gender. Most parents (66%) believed it was "very/somewhat" important for adolescents to have private time with the doctor during these visits, yet a substantial proportion of parents (46%) preferred that the doctor disclose to them the confidential information obtained during these private encounters. CONCLUSIONS: Parents find numerous topics important for discussion during well adolescent health care visits suggesting that parents might value a broad range of preventive care services for adolescents. However, some parents appear conflicted about incorporating adolescent confidentiality into prevention-focused visits.

Regional gray matter growth, sexual dimorphism, and cerebral asymmetry in the neonatal brain.

Although there has been recent interest in the study of childhood and adolescent brain development, very little is known about normal brain development in the first few months of life. In older children, there are regional differences in cortical gray matter development, whereas cortical gray and white matter growth after birth has not been studied to a great extent. The adult human brain is also characterized by cerebral asymmetries and sexual dimorphisms, although very little is known about how these asymmetries and dimorphisms develop. We used magnetic resonance imaging and an automatic segmentation methodology to study brain structure in 74 neonates in the first few weeks after birth. We found robust cortical gray matter growth compared with white matter growth, with occipital regions growing much faster than prefrontal regions. Sexual dimorphism is present at birth, with males having larger total brain cortical gray and white matter volumes than females. In contrast to adults and older children, the left hemisphere is larger than the right hemisphere, and the normal pattern of fronto-occipital asymmetry described in older children and adults is not present. Regional differences in cortical gray matter growth are likely related to differential maturation of sensory and motor systems compared with prefrontal executive function after birth. These findings also indicate that whereas some adult patterns of sexual dimorphism and cerebral asymmetries are present at birth, others develop after birth.

Cancer genetics.

OBJECTIVES: To provide a basic overview of genetics, focusing on breast and ovarian cancer susceptibility mutations on BRCA1 and BRCA2. DATA SOURCES: Research and review articles and government internet sites. CONCLUSION: The advances in molecular biology has enabled health care providers to be proactive rather than reactive in predicting some cancers and offering prevention strategies to greatly reduce the risk of developing cancer. Our expanding knowledge base of genetics may one day provide tailored treatment, and predict recurrence rates for all cancers. IMPLICATIONS FOR NURSING PRACTICE: The science of genetics will impact every aspect of health care, from primary care to specialized care. Nurses are on the front line and will be expected to recognize patterns of disease that may indicate a possible genetic link, educate the family about the implications of a potential genetic susceptibility and refer the family for counseling. To accomplish this, each nurse should have a minimum basic knowledge of genetics, and formal education for those who educate and counsel.

V102862 (Co 102862): a potent, broad-spectrum state-dependent blocker of mammalian voltage-gated sodium channels.

1. 4-(4-Fluorophenoxy)benzaldehyde semicarbazone (V102862) was initially described as an orally active anticonvulsant with robust activity in a variety of rodent models of epilepsy. The mechanism of action was not known. We used whole-cell patch-clamp techniques to study the effects of V102862 on native and recombinant mammalian voltage-gated Na+ channels. 2. V102862 blocked Na+ currents (I(Na)) in acutely dissociated cultured rat hippocampal neurons. Potency increased with membrane depolarization, suggesting a state-dependent mechanism of inhibition. There was no significant effect on the voltage dependence of activation of I(Na). 3. The dissociation constant for the inactivated state (K(I)) was approximately 0.6 microM, whereas the dissociation constant for the resting state (K(R)) was >15 microM. 4. The binding to inactivated channels was slow, requiring a few seconds to reach steady state at -80 mV. 5. The mechanism of inhibition was characterized in more detail using human embryonic kidney-293 cells stably expressing rat brain type IIA Na+ (rNa(v)1.2) channels, a major Na+ channel alpha subunit in rat hippocampal neurons. Similar to hippocampal neurons, V102862 was a potent state-dependent blocker of rNa(v)1.2 channels with a K(I) of approximately 0.4 microM and K(R) approximately 30 microM. V102862 binding to inactivated channels was relatively slow (k(+) approximately = 1.7 microM(-1) s(-1)). V102862 shifted the steady-state availability curve in the hyperpolarizing direction and significantly retarded recovery of Na+ channels from inactivation. 6. These results suggest that inhibition of voltage-gated Na+ channels is a major mechanism underlying the anticonvulsant properties of V102862. Moreover, understanding the biophysics of the interaction may prove to be useful in designing a new generation of potent Na+ channel blocker therapeutics.

Cochlear neuropathy in human presbycusis: Confocal analysis of hidden hearing loss in post-mortem tissue.

Recent animal work has suggested that cochlear synapses are more vulnerable than hair cells in both noise-induced and age-related hearing loss. This synaptopathy is invisible in conventional histopathological analysis, because cochlear nerve cell bodies in the spiral ganglion survive for years, and synaptic analysis requires special immunostaining or serial-section electron microscopy. Here, we show that the same quadruple-immunostaining protocols that allow synaptic counts, hair cell counts, neuronal counts and differentiation of afferent and efferent fibers in mouse can be applied to human temporal bones, when harvested within 9 h post-mortem and prepared as dissected whole mounts of the sensory epithelium and osseous spiral lamina. Quantitative analysis of five "normal" ears, aged 54-89 yrs, without any history of otologic disease, suggests that cochlear synaptopathy and the degeneration of cochlear nerve peripheral axons, despite a near-normal hair cell population, may be an important component of human presbycusis. Although primary cochlear nerve degeneration is not expected to affect audiometric thresholds, it may be key to problems with hearing in noise that are characteristic of declining hearing abilities in the aging ear.

Co-expression of Interleukin-15 Enhances the Protective Immune Responses Induced by Immunization with a Murine Malaria MVA-Based Vaccine Encoding the Circumsporozoite Protein.

Malaria remains a major global public health problem with an estimated 200 million cases detected in 2012. Although the most advanced candidate malaria vaccine (RTS,S) has shown promise in clinical trials, its modest efficacy and durability have created uncertainty about the impact of RTS,S immunization (when used alone) on global malaria transmission. Here we describe the development and characterization of a novel modified vaccinia virus Ankara (MVA)-based malaria vaccine which co-expresses the Plasmodium yoelii circumsporozoite protein (CSP) and IL-15. Vaccination/challenge studies showed that C57BL/6 mice immunized with the MVA-CSP/IL15 vaccine were protected significantly better against a P. yoelii 17XNL sporozoite challenge than either mice immunized with an MVA vaccine expressing only CSP or naïve controls. Importantly, the levels of total anti-CSP IgG were elevated about 100-fold for the MVA-CSP/IL15 immunized group compared to mice immunized with the MVA-CSP construct that does not express IL-15. Among the IgG subtypes, the IL-15 expressing MVA-CSP vaccine induced levels of IgG1 (8 fold) and IgG2b (80 fold) higher than the MVA-CSP construct. The significantly enhanced humoral responses and protection detected after immunization with the MVA-CSP/IL15 vaccine suggest that this IL-15 expressing MVA construct could be considered in the development of future malaria immunization strategies.

The Reagent [K(18-crown-6)][RuH(PPh(3))(2)(eta(5)-7,8-C(2)B(9)H(11))] as a Precursor to New Ruthenacarborane Complexes.

In ethanol the charge-compensated molecule exo-nido-ruthenacarborane [5,6,10-{RuCl(PPh(3))(2)}-5,6,10-&mgr;-(H)(3)-10-H-7,8-C(2)B(9)H(8)] reacts with KOH to afford the anionic closo-complex [RuH(PPh(3))(2)(eta(5)-7,8-C(2)B(9)H(11))](-) isolated as its K(+) (2a) or [K(18-crown-6)](+) (2b) salt. Treatment of 2a with CO gives [Ru(CO)(PPh(3))(2)(eta(5)-7,8-C(2)B(9)H(11))] (3a) in high yield; its structure was determined by X-ray crystallography. In contrast 2b reacts with CO to yield the salt [K(18-crown-6)][RuH(CO)(PPh(3))(eta(5)-7,8-C(2)B(9)H(11))] (2d). Reaction of 2b with [RuCl(2)(PPh(3))(3)] affords [Ru(2)(&mgr;-H)(H)(PPh(3))(4)(eta(5)-7,8-C(2)B(9)H(11))] (5), which with CO produces [Ru(2)(&mgr;-H)(&mgr;-sigma: eta(5)-7,8-C(2)B(9)H(10))(CO)(4)(PPh(3))(2)] (6), the structure of which was established by X-ray diffraction. The molecule has a metal-metal bond bridged on one side by a hydrido ligand and on the other by a nido-7,8-C(2)B(9)H(10) fragment. The latter is eta(5)-coordinated to a ruthenium atom ligated by a PPh(3) and a CO ligand and is also sigma-bonded to the second ruthenium which carries three CO molecules and a PPh(3) group. The sigma bond utilizes a boron lying in an alpha site with respect to the carbons in the ring coordinated to the Ru(CO)(PPh(3)) moiety. Reactions between 2b or 2d and [CuCl(PPh(3))(3)] and [AuCl(PPh(3))], respectively, afford the bimetal complexes [RuM(&mgr;-H)(L)(PPh(3))(2)(eta(5)-7,8-C(2)B(9)H(11))] [M = Cu, L = PPh(3) (7a), L = CO (7b); M = Au, L = PPh(3) (8a), L = CO (8b)]. X-ray diffraction studies are reported for 7a and 8a, revealing in the case of the former a structure in which an exopolyhedral B-Hright harpoon-up Cu bond supplements the Ru(&mgr;-H)Cu interaction.

Group programmes in early intervention services.

AIM: Group interventions can be a developmentally appropriate treatment option for young people with mental illness; however, there is a paucity of research into these programmes. This study had three aims: (i) to document and compare both clinicians' and clients' reasons for referral to the Orygen Youth Health Recovery Group Program (RGP); (ii) to describe demographic characteristics of patients referred to the RGP; and (iii) to delineate and differentiate characteristics of clients who do and do not engage with the RGP's activities. METHODS: Referral and assessment data from 212 clients referred to the RGP between July 2001 and November 2003 were collated and analysed. RESULTS: Main reasons for referral to the programme were relationships followed by vocational/educational issues. Similarly, the most common goals identified by clients were around relationships, followed by time use and vocational issues. Clients referred to the RGP but who did not attend were more likely to have a psychotic disorder, to be older, unemployed and have difficulties with time management and substance use. CONCLUSIONS: Social functioning and vocation are important considerations in facilitating young people's recovery from mental illness. Such issues can be addressed within the context of psychosocial recovery group programmes. Further research is needed not only to address problems regarding client engagement but also to evaluate outcomes from participation in such programmes.

Prenatal and neonatal brain structure and white matter maturation in children at high risk for schizophrenia.

OBJECTIVE: Schizophrenia is a neurodevelopmental disorder associated with abnormalities of brain structure and white matter, although little is known about when these abnormalities arise. This study was conducted to identify structural brain abnormalities in the prenatal and neonatal periods associated with genetic risk for schizophrenia. METHOD: Prenatal ultrasound scans and neonatal structural magnetic resonance imaging (MRI) and diffusion tensor imaging were prospectively obtained in the offspring of mothers with schizophrenia or schizoaffective disorder (N=26) and matched comparison mothers without psychiatric illness (N=26). Comparisons were made for prenatal lateral ventricle width and head circumference, for neonatal intracranial, CSF, gray matter, white matter, and lateral ventricle volumes, and for neonatal diffusion properties of the genu and splenium of the corpus callosum and corticospinal tracts. RESULTS: Relative to the matched comparison subjects, the offspring of mothers with schizophrenia did not differ in prenatal lateral ventricle width or head circumference. Overall, the high-risk neonates had nonsignificantly larger intracranial, CSF, and lateral ventricle volumes. Subgroup analysis revealed that male high-risk infants had significantly larger intracranial, CSF, total gray matter, and lateral ventricle volumes; the female high-risk neonates were similar to the female comparison subjects. There were no group differences in white matter diffusion tensor properties. CONCLUSIONS: Male neonates at genetic risk for schizophrenia had several larger than normal brain volumes, while females did not. To the authors' knowledge, this study provides the first evidence, in the context of its limitations, that early neonatal brain development may be abnormal in males at genetic risk for schizophrenia.

Conformational analysis of PEt3 and P(OMe)3 in metal complexes.

The conformations of the archetypal acyclic phosphorus ligands PEt(3) and P(OMe)(3) are classified on the basis of the observation that torsions about the P-C (or P-O) bonds show favoured conformations lying close to gauche (+/-60 degrees) or anti values (180 degrees). Analysis of the symmetry of the conformation space defined by the three M-P-X-C (X = CH(2) or O) torsion angles (t(1-3)) implies the existence of seven unique conformer types (A (aaa), B (g(+)g(+)g(+)), C (ag(+)g(+)), D (aag(+)), E (g(-)ag(+)), F (ag(-)g(+)), G (g(-)g(+)g(+)) and their symmetry equivalents) arising from the combinations of g(-), g(+) and a torsions. These conformers are observed in 1972 M-PEt(3) and 735 M-P(OMe)(3) fragments from crystal structures of metal complexes in the CSD following the popularity sequence: F > C >> D > B > G > E >> A for M-PEt(3); and: C > D > F >> E >> A, B, G. for M-P(OMe)(3). Pathways for low-energy interconversion of these conformers, dominated by single chain flip routes, are readily inferred for M-P(OMe)(3). The conformers of M-PEt(3) are apparently less readily interconverted. The popularity of conformations is only loosely related to the energies of these conformations as calculated by DFT or MM methods for two-, four- (square planar) and six-coordinate metal complexes of these ligands (and free PEt(3) and P(OMe)(3)). It would appear that the conformational preferences observed are determined by a balance between intra-ligand effects (repulsion between chains and avoidance of syn-pentane-like); inter-ligand effects (repulsions between gauche substituents at P and cis co-ligands notably when the coordination number at the metal is high); and residual anomeric effects (weakly favouring anti conformations in P(OMe)(3) species).

Prenatal mild ventriculomegaly predicts abnormal development of the neonatal brain.

BACKGROUND: Many psychiatric and neurodevelopmental disorders are associated with mild enlargement of the lateral ventricles thought to have origins in prenatal brain development. Little is known about development of the lateral ventricles and the relationship of prenatal lateral ventricle enlargement with postnatal brain development. METHODS: We performed neonatal magnetic resonance imaging on 34 children with isolated mild ventriculomegaly (MVM; width of the atrium of the lateral ventricle >/= 1.0 cm) on prenatal ultrasound and 34 age- and sex-matched control subjects with normal prenatal ventricle size. Lateral ventricle and cortical gray and white matter volumes were assessed. Fractional anisotropy (FA) and mean diffusivity (MD) in corpus callosum and corticospinal white matter tracts were determined obtained using quantitative tractography. RESULTS: Neonates with prenatal MVM had significantly larger lateral ventricle volumes than matched control subjects (286.4%; p < .0001). Neonates with MVM also had significantly larger intracranial volumes (ICV; 7.1%, p = .0063) and cortical gray matter volumes (10.9%, p = .0004) compared with control subjects. Diffusion tensor imaging tractography revealed a significantly greater MD in the corpus callosum and corticospinal tracts, whereas FA was significantly smaller in several white matter tract regions. CONCLUSIONS: Prenatal enlargement of the lateral ventricle is associated with enlargement of the lateral ventricles after birth, as well as greater gray matter volumes and delayed or abnormal maturation of white matter. It is suggested that prenatal ventricle volume is an early structural marker of altered development of the cerebral cortex and may be a marker of risk for neuropsychiatric disorders associated with ventricle enlargement.

Elevated levels of total (maternal and fetal) beta-globin DNA in maternal blood from first trimester pregnancies with trisomy 21.

BACKGROUND: Elevated levels of circulating fetal DNA have been observed in maternal plasma when a trisomy 21 fetus is confirmed. However, these studies have been limited to pregnancies carrying a male fetus. We sought to quantify total (fetal and maternal) DNA from dried blood spots (DBS) for use as an additional factor in multi-parameter prenatal screening for aneuploidy. METHODS: Maternal DBS were obtained from the NICHD-sponsored multi-center cohort (BUN) study. Seventeen confirmed trisomy 21 (mean gestational age 12.23 +/- 0.77 weeks) cases were each matched by gestational age to euploid controls (n = 30). DNA was extracted and quantitative PCR was performed to measure four non-chromosome 21 loci, including glyceraldehyde-3-phosphate dehydrogenase (GAPDH) (12p13), beta-globin (11p15.5), beta-actin (7p15-12) and p53 (17p13.1). RESULTS: Beta-globin DNA levels were significantly elevated (P = 0.003) in 13 of 17 trisomy 21 cases (4.08 +/- 1.78 Geq/ml x 10(5)) compared with matched controls (2.35 +/- 1.84 Geq/ml x 10(5)). Following conversion of beta-globin concentrations into multiples of the median (MoM), MoM for trisomy 21 cases was 2.8 compared with 1.0 in euploid cases. No significant differences in levels of circulating GAPDH, beta-actin and p53 sequences were detected. CONCLUSIONS: This work demonstrates differential levels of circulating beta-globin DNA in maternal blood of euploid and trisomy 21 cases. Sequence-specific quantification could provide an additional measure to improve non-invasive methods of prenatal screening to detect trisomy 21 using dried blood. Beta-globin in particular is an attractive biomarker that could contribute to enhance multiple serum parameter testing in the first trimester.

Quantity versus quality: optimal methods for cell-free DNA isolation from plasma of pregnant women.

PURPOSE: Methods to isolate cell-free fetal DNA from maternal plasma are critical in developing noninvasive fetal DNA testing strategies. Given that plasma consists of heterogeneous DNA-size fragments in a complex mix of proteins, recovery and analysis of this DNA are understandably inefficient. To facilitate recovery, we performed qualitative and quantitative analysis of DNA isolated from maternal plasma. METHODS: DNA isolated from maternal blood (n = 15) was compared using five different DNA isolation protocols: two conventional, two column-based, and one magnetic-bead based. Purity and concentration of DNA recovered were determined with a NanoDrop spectrophotometer. Real-time polymerase chain reaction quantification of the beta-globin and DYS1 loci was performed to determine total and fetal-specific genome equivalents, respectively. RESULTS: DNA quality and quantity were different among the five methods tested. Although purity and concentration of total DNA were greatest with the conventional boiling-lysis approach, correct detection of a male fetus was achieved in only 62.5% of cases. DNA isolation using the magnetic beads yielded the highest quantity of total DNA (2018.83 +/- 4.09 GEq/mL), with 100% fetal DNA detection. CONCLUSIONS: Optimal plasma DNA recovery protocols must take into account DNA purity and concentration. We confirm that the magnetic-beads method provides a fast, simple, sensitive, and specific approach to purify plasma DNA. The resulting high-quality DNA facilitates efficient examination of fetal DNA sequences.

Orthodontic bonding to porcelain: a comparison of bonding systems.

STATEMENT OF PROBLEM: Direct bonding of orthodontic brackets to porcelain surfaces has been plagued by failure. PURPOSE: The purpose of this study was to compare the bond strengths of several different bonding systems when bonding orthodontic brackets to porcelain-fused-to-metal surfaces. MATERIAL AND METHODS: Fifty natural glazed feldspathic porcelain-fused-to-noble metal disks 6 mm in diameter and 3 mm in height (1 mm metal and 2 mm porcelain) were fabricated and divided into 5 groups of 10. A different bonding system (GC America Fuji LC, American Ortho Spectrum, 3M Transbond, TP Orthodontics Python, and Kerr Herculite) was assigned to each group, and 50 identical orthodontic brackets were bonded (with the above mentioned systems) to each disk according to each manufacturer's instructions. Each system except TP Orthodontics Python conditioned with phosphoric acid (35% to 37.5%) and all systems were primed with silane before bonding. The specimens were subjected to gradual shear forces up to 123 N in a universal testing machine (Instron Corp, Canton, Mass.) until fracture. The shear bond strength of the bonding systems between the porcelain surface and the bracket was measured in megapascals (MPa). Failures were observed via a Zeiss optical microscope (10x); Tukey's HSD Test and analysis of variance were used to determine significance between the bonding systems at P<.05 level of significance. RESULTS: Failure of all of specimens was adhesive between the porcelain surface and the bonding agents. On the basis of a current literature review, bonding systems were categorized as clinically acceptable if they had a shear bond strength of 6 to 8 MPa. The 3M Transbond Bonding System, American Orthodontics Spectrum Bonding System, and GC America Fuji Ortho LC Bonding System performed within this clinically acceptable range (6 to 8 MPa), whereas Kerr Herculite Bonding System and TP Orthodontics Python Bonding System did not (2 to 4 MPa). The bond strengths of GC America Fuji Ortho LC, 3M Transbond, and American Orthodontics Spectrum were significantly greater (mean = 2.3 times) than TP Orthodontics Python or Kerr Herculite bonding systems. CONCLUSION: Within the limitations of this study, the results reaffirm the regimen of conditioning with phosphoric acid and priming with silane before bonding orthodontic brackets to feldspathic porcelain fused to noble metal. All products indicated for this purpose may not achieve satisfactory bond strengths; however, because they do not all include the critical steps of conditioning with phosphoric acid and priming with silane. The 3M Transbond Bonding System, American Orthodontics Spectrum Bonding System, and GC America Fuji Ortho LC Bonding System performed within the clinically acceptable range (6 to 8 MPa), whereas Kerr Herculite Bonding System and TP Orthodontics Python Bonding System did not (2 to 4 MPa).

tipE regulates Na+-dependent repetitive firing in Drosophila neurons.

The tipE gene, originally identified by a temperature-sensitive paralytic mutation in Drosophila, encodes a transmembrane protein that dramatically influences sodium channel expression in Xenopus oocytes. There is evidence that tipE also modulates sodium channel expression in the fly; however, its role in regulating neuronal excitability remains unclear. Here we report that the majority of neurons in both wild-type and tipE mutant (tipE-) embryo cultures fire sodium-dependent action potentials in response to depolarizing current injection. However, the percentage of tipE- neurons capable of firing repetitively during a sustained depolarization is significantly reduced. Expression of a tipE+ transgene, in tipE- neurons, restores repetitive firing to wild-type levels. Analysis of underlying currents reveals a slower rate of repolarization-dependent recovery of voltage-gated sodium currents during repeated activation in tipE- neurons. This phenotype is also rescued by expression of the tipE+ transgene. These data demonstrate that tipE regulates sodium-dependent repetitive firing and recovery of sodium currents during repeated activation. Furthermore, the duration of the interstimulus interval necessary to fire a second full-sized action potential is significantly longer in single- versus multiple-spiking transgenic neurons, suggesting that a slow rate of recovery of sodium currents contributes to the decrease in repetitive firing in tipE- neurons.

Cell-free fetal DNA and intact fetal cells in maternal blood circulation: implications for first and second trimester non-invasive prenatal diagnosis.

Both intact fetal cells as well as cell-free fetal DNA are present in the maternal circulation and can be recovered for non-invasive prenatal genetic diagnosis. Although methods for enrichment and isolation of rare intact fetal cells have been challenging, diagnosis of fetal chromosomal aneuploidy including trisomy 21 in first- and second-trimester pregnancies has been achieved with a 50-75% detection rate. Similarly, cell-free fetal DNA can be reliably recovered from maternal plasma and assessed by quantitative PCR to detect fetal trisomy 21 and paternally derived single gene mutations. Real-time PCR assays are robust in detecting low-level fetal DNA concentrations, with sensitivity of approximately 95-100% and specificity near 100%. Comparing intact fetal cell versus cell-free fetal DNA methods for non-invasive prenatal screening for fetal chromosomal aneuploidy reveals that the latter is at least four times more sensitive. These preliminary results do not support a relationship between frequency of intact fetal cells and concentration of cell-free fetal DNA. The above results imply that the concentration of fetal DNA in maternal plasma may not be dependent on circulating intact fetal cells but rather be a product of growth and cellular turnover during embryonic or fetal development.