Chloral hydrate for sedation of children with asthma during dental treatment.

AIM: We hypothesised that chloral hydrate is safe and effective for sedation during dental treatments for children with mild asthma. We evaluated the safety and efficacy of chloral hydrate by measuring changes in heart rate (HR), transcutaneous oxygen saturation, (SpO2), asthma score, behaviour, types and frequency of adverse reactions associated with chloral hydrate were assessed throughout treatment. MATERIALS AND METHODS: Children (<10 years old) with mild asthma undergoing dental treatments received a single 65 mg/kg oral dose of chloral hydrate liquid 1 hour prior to treatment in an open label trial. Heart rate (HR), SpO2, asthma score, behaviour, types and frequency of adverse reactions associated with chloral hydrate were assessed throughout treatment. Asthma score was obtained before and after treatment. Thirty minutes after treatment, SpO2, HR, and level of consciousness was assessed. RESULTS: Twenty four children were enrolled and 92% (22/24) recovered from sedation without respiratory depression. Two experienced mild respiratory depression related to chloral hydrate. Asthma was not a contributing factor as they did not experience wheezing, cough, tachypnoea, or retractions. Inhaled nitrous oxide supplemented chloral hydrate sedation in 63% (15/24) children to achieve effective cooperation. Three children had a SpO2 <95% (2 during treatment, 1 during recovery). CONCLUSION: Chloral hydrate 65 mg/kg administered a as single oral dose appears to be safe with respect to disease exacerbation for children with mild asthma undergoing dental treatment. Due to ineffective sedation and mild respiratory depression associated with chloral hydrate, newer, easily titrated medications, such as midazolam, may offer advantages.

Analysis of the RELN gene as a genetic risk factor for autism.

Several genome-wide screens have indicated the presence of an autism susceptibility locus within the distal long arm of chromosome 7 (7q). Mapping at 7q22 within this region is the candidate gene reelin (RELN). RELN encodes a signaling protein that plays a pivotal role in the migration of several neuronal cell types and in the development of neural connections. Given these neurodevelopmental functions, recent reports that RELN influences genetic risk for autism are of significant interest. The total data set consists of 218 Caucasian families collected by our group, 85 Caucasian families collected by AGRE, and 68 Caucasian families collected at Tufts University were tested for genetic association of RELN variants to autism. Markers included five single-nucleotide polymorphisms (SNPs) and a repeat in the 5'-untranslated region (5'-UTR). Tests for association in Duke and AGRE families were also performed on four additional SNPs in the genes PSMC2 and ORC5L, which flank RELN. Family-based association analyses (PDT, Geno-PDT, and FBAT) were used to test for association of single-locus markers and multilocus haplotypes with autism. The most significant association identified from this combined data set was for the 5'-UTR repeat (PDT P-value=0.002). These analyses show the potential of RELN as an important contributor to genetic risk in autism.

Equilibrium and non-equilibrium dynamics of the cranio-mandibular complex and cervical spine.

A dynamic model of the inverted pendulum characteristics of the head and cervical spine is presented. Using simple approximations and a single rotational-degree-of-freedom approach, the model is shown to conform to the classical mathematical description of an inverted pendulum motion. It also exhibits the well-known point of unstable equilibrium which is a standard property of such systems. Specific predictions of this theoretical description are compared against other values for the tilt, angular velocity and acceleration of the head during acceleration-sled testing, and with the Kapitza relation for mechanical-dither stabilization of an inverted pendulum. Numerical evaluations of the dynamic variables, resonant frequencies and time constants important to the problem are provided, and suggestions are made about how further results might be derived from extended versions of the model. This approach can now be refined to serve as a testing ground for analysing the biomechanics of traumatic neck injuries and for interpreting the possible roles that mandibular dysfunctions and dental malocclusion may play in disorders of the cervical spine. (Some background needed for exploring the latter possibility is presented.)

Carrier-envelope offset dynamics of mode-locked lasers.

We investigate coupling mechanisms between the amplitude and the carrier-envelope offset phase in mode-locked lasers. We find that nonlinear beam steering in combination with the intracavity prism compressor is the predominant mechanism that causes amplitude-to-phase conversion in our laser. A second mechanism, induced by self-steepening, is also identified. These mechanisms are important for stabilizing the carrier-envelope offset phase and also explain the extremely low pulse-to-pulse energy fluctuations observed in some lasers with carrier-envelope lock. The coupling mechanisms described have important implications for applications of few-cycle optical pulses.

HIV type 1 Tat inhibits tumor necrosis factor alpha-induced repression of tumor necrosis factor receptor p55 and amplifies tumor necrosis factor alpha activity in stably tat-transfected HeLa Cells.

The human immunodeficiency virus type 1 (HIV-1) Tat protein is a key regulatory protein in the HIV-1 replication cycle. Tat interacts with cellular transcriptional factors and cytokines, such as tumor necrosis factor (TNF-alpha), and alters the expression of a variety of genes in HIV-1-infected and noninfected cells. To further elucidate the mechanisms by which HIV-1 Tat amplifies the activity of TNF-alpha, we transfected the HIV-1 tat gene into an epithelial (HeLa) cell line. We observed that Tat-expressing cells had increased NF-kappa B-dependent trans-activational activity due to enhanced NF-kappa B--DNA binding in response to TNF-alpha treatment. Tumor necrosis factor receptor (TNFR) p55 was the prominent receptor, as neutralizing antibodies to TNFR p55, but not to TNFR p75, blocked TNF-alpha-mediated NF-kappa B activation. Furthermore, tat-transfected cells were more sensitive to TNF-alpha-induced cytotoxicity and only the neutralizing antibodies to TNFR p55 completely protected the cells. To determine whether TNFR p55 was involved in amplification of cellular response to TNF-alpha by HIV-1 Tat, we investigated the effect of TNF-alpha on TNFR p55 expression in the tat-transfected cells. TNF-alpha treatment resulted in a reduction in both TNFR p55 mRNA and protein levels in the control cells but not in the tat-transfected cells as determined with Northern blot and Western blot analyses, respectively. Our results indicate that HIV-1 Tat may inhibit TNF-alpha-induced repression of TNFR p55 and thereby amplify TNF-alpha activity in these stably transfected cells.

Biased distribution of inverted and direct Alus in the human genome: implications for insertion, exclusion, and genome stability.

Alu sequences, the most abundant class of large dispersed DNA repeats in human chromosomes, contribute to human genome dynamics. Recently we reported that long inverted repeats, including human Alus, can be strong initiators of genetic change in yeast. We proposed that the potential for interactions between adjacent, closely related Alus would influence their stability and this would be reflected in their distribution. We have undertaken an extensive computational analysis of all Alus (the database is at http://dir.niehs.nih.gov/ALU) to better understand their distribution and circumstances under which Alu sequences might affect genome stability. Alus separated by <650 bp were categorized according to orientation, length of regions sharing high sequence identity, distance between highly identical regions, and extent of sequence identity. Nearly 50% of all Alu pairs have long alignable regions (>275 bp), corresponding to nearly full-length Alus, regardless of orientation. There are dramatic differences in the distributions and character of Alu pairs with closely spaced, nearly identical regions. For Alu pairs that are directly repetitive, approximately 30% have highly identical regions separated by <20 bp, but only when the alignments correspond to near full-size or half-size Alus. The opposite is found for the distribution of inverted repeats: Alu pairs with aligned regions separated by <20 bp are rare. Furthermore, closely spaced direct and inverted Alus differ in their truncation patterns, suggesting differences in the mechanisms of insertion. At larger distances, the direct and inverted Alu pairs have similar distributions. We propose that sequence identity, orientation, and distance are important factors determining insertion of adjacent Alus, the frequency and spectrum of Alu-associated changes in the genome, and the contribution of Alu pairs to genome instability. Based on results in model systems and the present analysis, closely spaced inverted Alu pairs with long regions of alignment are likely at-risk motifs (ARMs) for genome instability.

Absolute frequency measurement of the 435.5-nm (171)Yb+-clock transition with a Kerr-lens mode-locked femtosecond laser.

We have measured the frequency of the 6s(2)S(1/2)(2)-5d D(3/2)(2) electric-quadrupole transition of (171)(Yb) (+) with a relative uncertainty of 1x10(-14) , nu(Yb)=688358 979309312Hz +/-6Hz . We used a femtosecond frequency comb generator to phase-coherently link the optical frequency derived from a single trapped ion to a cesium-fountain-controlled hydrogen maser. This measurement is one of the most accurate measurements of optical frequencies ever reported, and it represents a contribution to the development of optical clocks based on a (171)Yb(+)-ion standard.

Inverted Alu repeats unstable in yeast are excluded from the human genome.

The nearly one million ALU: repeats in human chromosomes are a potential threat to genome integrity. ALU:s form dense clusters where they frequently appear as inverted repeats, a sequence motif known to cause DNA rearrangements in model organisms. Using a yeast recombination system, we found that inverted ALU: pairs can be strong initiators of genetic instability. The highly recombinagenic potential of inverted ALU: pairs was dependent on the distance between the repeats and the level of sequence divergence. Even inverted ALU:s that were 86% homologous could efficiently stimulate recombination when separated by <20 bp. This stimulation was independent of mismatch repair. Mutations in the DNA metabolic genes RAD27 (FEN1), POL3 (polymerase delta) and MMS19 destabilized widely separated and diverged inverted ALU:s. Having defined factors affecting inverted ALU: repeat stability in yeast, we analyzed the distribution of ALU: pairs in the human genome. Closely spaced, highly homologous inverted ALU:s are rare, suggesting that they are unstable in humans. ALU: pairs were identified that are potential sites of genetic change.

Intensity-induced mode shift in a femtosecond laser by a change in the nonlinear index of refraction.

The modes of the comb spectrum of a Kerr-lens mode-locked laser are frequency shifted versus the corresponding cw modes of the cavity by an intensity-induced change in the index of refraction in the Kerr medium. We demonstrate this effect and discuss novel schemes for fast frequency control of the comb spectrum.

Noise suppression in femtosecond mid-infrared light sources.

An experimental and theoretical study of intrinsic correlations and noise-suppression mechanisms in two-stage femtosecond mid-IR light sources is presented. The setup, based on parametric amplification in BBO and subsequent difference-frequency mixing in AgGaS(2), delivers approximately 100-fs mid-IR pulses with 1-2-muJ energy. Exceptionally low pulse-energy fluctuations of only 0.2% in the mid-IR (lambda approximately 3-6 mum) are found, which are much smaller than the Ti:sapphire amplifer noise. The noise suppression is analyzed and found to stem from the interplay between dispersion and pump depletion.

Long-term changes in connexin32 gap junction protein and mRNA expression following cocaine self-administration in rats.

Considerable evidence indicates a critical role for dopamine in the reinforcing effects of cocaine. Because dopamine has been shown to be a critical modulator of gap junction communication in both eye and brain, we sought to examine whether extended intravenous cocaine self-administration would affect the expression of gap junction channel-forming proteins (connexins). Using ELISA, Western analysis, immunohistochemistry, semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR), and non-radioactive in situ hybridization, we demonstrate that withdrawal from chronic cocaine self-administration causes lasting changes in connexin32 (Cx32) expression in the nucleus accumbens and hippocampus at 2, 7 and 21 days after the last cocaine injection. A sustained decrease in Cx32 protein and mRNA levels is noted in areas that have been implicated in cocaine craving (i.e. nucleus accumbens and subfields of the hippocampal formation). A progressive increase in gap junction protein and mRNA expression is noted in areas that become hyperexcitable after chronic cocaine exposure (i.e. CA1 hippocampal neurons). We speculate that gap junction communication may be critically involved in reinforcement processes and neuroadaptive changes produced by drugs of abuse.

Superradiant rayleigh scattering from a bose-einstein condensate

Rayleigh scattering off a Bose-Einstein condensate was studied. Exposing an elongated condensate to a single off-resonant laser beam resulted in the observation of highly directional scattering of light and atoms. This collective light scattering is caused by the coherent center-of-mass motion of the atoms in the condensate. A directional beam of recoiling atoms was built up by matter wave amplification.

A biomechanical model of the craniomandibular complex and cervical spine based on the inverted pendulum.

The head and neck constitute an inverted pendulum that is stabilized during consciousness by neuromuscular restoring forces. An analysis of the dynamics of this inverted pendulum suggests that the mechanics of the mandible and temporomandibular joint might couple into those of the pendulum's stabilization process. In this article, physical principles of the inverted pendulum model as these apply to the head and neck are explored, and the authors describe implications of mandibular mechanics for the forces acting on the head and neck at equilibrium. This novel application of the inverted pendulum model predicts that alteration or pathology of temporomandibular mechanics would lead to perturbations of the normal forces acting in the head and neck. Under certain circumstances, these perturbations could be expected to contribute to symptoms and result in additional or accelerated degenerative effects.

Sealant status and factors associated with sealant presence among children in Milwaukee, WI.

To determine the percent of school-children aged 6-14 years with sealants placed in their permanent molars in the City of Milwaukee. 2) To describe factors associated with sealant presence among these children. 3) To describe differences, if any, among ethnic majority and minority groups. Twelve public schools agreed to participate in this project. After consent forms were obtained, 1,234 dental exams were performed. A 15-item pretested questionnaire was given to each child to take home for the parent(s) to complete. Response rate was 60 percent (N = 742). Data were analyzed using frequencies and Chi-Square tests (P-value < 0.05). Only 9.6 percent of the sample had sealants on their permanent molars. Variables that were found associated with children more likely to have sealants included: gender (female children more likely than males); children with a recent dental exam; children having a regular dentist; parents having heard about sealants before this study; parents' correct knowledge regarding the purpose of sealants; higher level of parents' education; higher parents' total annual income; ethnicity (Caucasian children more likely than Hispanic, African American, American Indian, or Asian children); and age (children in the older group, 10-14 years, more likely than children in the younger group, 6-9 years). Percent of school-children with sealants on their permanent molars in the city of Milwaukee is low. Efforts are needed to increase the knowledge of sealants by the general public as well as to promote sealant use by dentists in both private practice and public health programs, especially for minority children.

Comparison of TOBEC-derived total body fat with fat pad weights.

Total body electrical conductivity (TOBEC) predictions of overall body fat were compared to combined perirenal and epididymal fat pad weights. The latter are considered to be reasonable estimates of overall adiposity. TOBEC was used to measure the body composition of 40 male Long-Evans and two male Sprague-Dawley rats ranging in weight from 210-505 g. The animals were then sacrificed and the perirenal and epididymal fat pads were removed and weighed. Core temperature was recorded before and after TOBEC values were collected. To assess the effect of position, two values were obtained for young rats: one when the tail was tucked under the rat's body and another when the tail was extended such that the full length of the measurement chamber was occupied. The TOBEC-predicted body fat was significantly different for these two positions. The best correlation between fat pad weight and TOBEC-predicted body fat (r = 0.83) was obtained when young animals were in the tail-extended position. The reliability of TOBEC readings appears to be reasonably good with mature rats.

p53 oligomerization and DNA looping are linked with transcriptional activation.

We examined the role of p53 oligomerization in DNA binding and in transactivation. By conventional electron microscopy (EM) and scanning transmission EM, we find that wild-type tetramers contact 18-20 bp at single or tandem 19 bp consensus sequences and also stack in apparent register, tetramer on top of tetramer. Stacked tetramers link separated DNA binding sites with DNA loops. Interestingly, the p53(1-320) segment, which lacks the C-terminal tetramerization domain, binds DNA consensus sites as stacked oligomers. Although the truncated protein binds DNA with reduced efficiency, it nevertheless induces DNA looping by self-association. p53, therefore, has a C-terminal tetramerization domain that enhances DNA binding and a non-tetrameric oligomerization domain that stacks p53 at consensus sites and loops separated consensus sites via protein-protein interactions. Using model promoters, we demonstrate that wild-type and tetramerization-deficient p53s activate transcription well when tandem consensus sites are proximal to TATA sequences and poorly when tandem sites are distal. In the presence of proximal sites, however, stimulation by distal sites increases 25-fold. Tetramerization and stacking of tetramers, therefore, provide dual mechanisms to augment the number of p53 molecules available for activation through p53 response elements. DNA looping between separated response elements further increases the concentration of local p53 by translocating distally bound protein to the promoter.

p53 domains: structure, oligomerization, and transformation.

Wild-type p53 forms tetramers and multiples of tetramers. Friedman et al. (P. N. Friedman, X. B. Chen, J. Bargonetti, and C. Prives, Proc. Natl. Acad. Sci. USA 90:3319-3323, 1993) have reported that human p53 behaves as a larger molecule during gel filtration than it does during sucrose gradient sedimentation. These differences argue that wild-type p53 has a nonglobular shape. To identify structural and oligomerization domains in p53, we have investigated the physical properties of purified segments of p53. The central, specific DNA-binding domain within murine amino acids 80 to 320 and human amino acids 83 to 323 behaves predominantly as monomers during analysis by sedimentation, gel filtration, and gel electrophoresis. This consistent behavior argues that the central region of p53 is globular in shape. Under appropriate conditions, however, this segment can form transient oligomers without apparent preference for a single oligomeric structure. This region does not enhance transformation by other oncogenes. The biological implications of transient oligomerization by this central segment, therefore, remain to be demonstrated. Like wild-type p53, the C terminus, consisting of murine amino acids 280 to 390 and human amino acids 283 to 393, behaves anomalously during gel filtration and apparently has a nonglobular shape. Within this region, murine amino acids 315 to 350 and human amino acids 323 to 355 are sufficient for assembly of stable tetramers. The finding that murine amino acids 315 to 360 enhance transformation by other oncogenes strongly supports the role of p53 tetramerization in oncogenesis. Amino acids 330 to 390 of murine p53 and amino acids 340 to 393 of human p53, which have been implicated by Sturzbecher et al. in tetramerization (H.-W. Sturzbecher, R. Brain, C. Addison, K. Rudge, M. Remm, M. Grimaldi, E. Keenan, and J. R. Jenkins, Oncogene 7:1513-1523, 1992), do not form stable tetramers under our conditions. Our findings indicate that p53 has at least two autonomous oligomerization domains: a strong tetramerization domain in its C-terminal region and a weaker oligomerization domain in the central DNA binding region of p53. Together, these domains account for the formation of tetramers and multiples of tetramers by wild-type p53. The tetramerization domain is the major determinant of the dominant negative phenotype leading to transformation by mutant p53s.

Factors that contribute to the reduced weight gain following chronic ventromedial hypothalamic stimulation.

This report follows up our earlier finding that chronic ventromedial hypothalamic stimulation caused an inhibition of weight gain. In this study we examined the contribution of stimulation-induced activity and brown adipose tissue thermogenesis to the reduced weight gain following three sessions of low-level stimulation delivered every other day to the ventromedial hypothalamus and adjacent areas. During stimulation trials, activity level was ranked on a dichotomous scale. Weight gain and food intake were subsequently monitored for an additional 4 weeks, after which the effects of a 60-s stimulation trial on the temperature of core and interscapular brown adipose tissue were evaluated. The highest activity was associated with the ventromedial hypothalamic sites and this factor contributed significantly to the difference in weight gain and food intake resulting from stimulation of the ventromedial hypothalamus and other areas. These differences largely disappeared during the follow-up period. With little exception, none of the sites elicited temperature changes in brown adipose tissue. As demonstrated in acute work, the contribution of stimulation-induced activity must be dissociated from the metabolic changes that occur in response to ventromedial hypothalamic stimulation.

p53 domains: identification and characterization of two autonomous DNA-binding regions.

We have investigated the DNA-binding, oligomerization, and trans-activation functions of isolated segments of murine p53. We find that p53 has two autonomous DNA-binding regions. One domain, from amino acid 280 to 390, forms stable tetramers and binds DNA nonspecifically. The biological significance, if any, of this DNA-binding activity is not known. A second domain, from amino acid 80 to 290, does not form stable tetramers under stringent conditions but binds DNA both specifically and nonspecifically. The specific DNA-binding function of p53, therefore, resides in the highly conserved central region of the protein and does not require stable tetramerization. Amino acids 1-290, which include both the specific DNA-binding domain and the amino-terminal acidic region, activate a p53-specific promoter in vivo. This finding strongly argues that the DNA-binding activity of p53 segment 80-290 is physiologically significant. The role of tetramerization in p53 function remains to be determined.

Formation of stable p53 homotetramers and multiples of tetramers.

We have used gradient gel electrophoresis and chemical cross-linking to analyze the quaternary structure of purified, wild-type, murine p53. Under nondenaturing conditions, p53 electrophoreses as tetramers and multiples of tetramers. Under denaturing conditions, fully cross-linked p53 also behaves as tetrameric structures. We confirmed the composition of the tetramers by partially cross-linking p53 and dissociating tetramers into monomers, dimers, and trimers.