Lifetime needle sharing: a predictive analysis

Through understanding predictors of needle sharing, it may be possible to design AIDS prevention interventions more effectively. Data were collected from a sample of 416 patients in two New York City methadone programs in 1990. Questions were asked about needle sharing and about a battery of predictors covering 11 psychosocial domains. Based on factor analysis, these were reduced to seven factors: criminal history, antisocial characteristics, social integration, severity of psychiatric problems, current drug involvement, physical health, and personality disorders. Bivariate analyses showed that criminal involvement, antisocial characteristics, social integration, and age were significantly related to needle sharing. With the seven factors, as well as age, gender, and ethnicity simultaneously examined by means of regression analysis, it was found that criminal involvement, severity of psychiatric problems, and age were all positively associated with needle sharing. Implications for treatment are discussed.

Counselling risk figures for fragile X carrier females of varying band sizes for use in predicting the likelihood of retardation in their offspring

We have derived risk figures for fra(X) syndrome carrier mothers based on their DNA status. Clinical and molecular information was analysed in 200 carrier mothers and their offspring. Individuals were classified as affected by a requirement for special education. Risk figures were calculated using the genotype of the intellectually normal offspring in order to reduce ascertainment bias. Analysis was made on women with differing mutation size to predict the proportion of affected offspring. Using this method the following risk figures were derived: 1. For carrier women with an increase (delta) of 0.06-0.14 Kb, the risk for having an affected son was 29% (1 in 3.5) and 25% for daughters (1 in 4). This predicts an overall 73% chance of a normal child. 2. For delta size 0.15-0.24 Kb, the risk of having an affected son was 46% (1 in 2.2) and 32% for daughters (1 in 3.1), predicting a 61% chance of a normal child. 3. For delta size > 0.24 Kb, normal transmitting male offspring were not seen, i.e., the risk for males was 50% (1 in 2) and for females 32% (1 in 3.1) which predicts a 59% chance of a normal child.

Ultrasound-guided fetal intravascular transfusions for severe erythroblastosis, 1984-1993

The results of the first 10 years' experience in ultrasound-guided fetal intravascular transfusions at the Royal Women's Hospital were reviewed. Since the first transfusion, a variety of techniques have been employed in 78 fetuses, all with severe erythroblastosis. A total of 288 intrauterine transfusions have been attempted with an overall survival rate of 75.6% (59 of 78). The overall survival rate for delivered fetuses improved from 64.3% (18 of 28) in 1984-1987, to 82.0% (41 of 50) in 1988-1993. There was a total of 33 hydropic fetuses, of whom 20 (60.6%) survived, significantly fewer compared with 86.7% (39 of 45) of the nonhydropic fetuses (odds ratio [OR] 0.25, 95% confidence interval [CI] 0.09 to 0.70, p < .01). Fetuses who were sicker at the time of transfusion, as reflected by larger haemoglobin deficits, had lower survival rates, as did those requiring transfusions at earlier gestational ages. When these variables were allowed for, the survival rate significantly improved over time (OR 6.3, 95% CI 1.3 to 30.4, p < 0.05), probably reflecting the increased skill of the ultrasonologists, but the presence of hydrops per se was no longer important. Variations of the technique employed, such as exchange or intraperitoneal transfusion, or different sites for transfusion, were not significantly related to survival.

Solution structure of a GA mismatch DNA sequence, d(CCATGAATGG)2, determined by 2D NMR and structural refinement methods

GA mismatches in DNA have drawn attention because of their special repair mechanisms, stability, and variety of conformations. A symmetric 10-base oligodeoxyribonucleotide duplex, d(CCATGAATGG)2, containing two GA mismatches has been investigated by one- and two-dimensional multinuclear NMR and molecular refinement procedures to ascertain the conformational details of the 5'-pyrimidine-GA-purine-3' sequence. A molecular model established from the NMR results has a B-type right-handed helix with each of the bases retaining the normal anti-glycosidic torsional angles. Type I mismatched base pairs have GNH2-AN7 and GN3-ANH2 (edge-to-edge) hydrogen bonds, while type II base pairs have GN1H-AN1 and GO6-ANH2 (face-to-face) bonds. The conformation at the GA mismatch site has type I GA base pairs and an unusual cross-strand stacking of the adjacent G5 and A6 bases, which causes significant overwinding of the helix at the mismatch site. Unusual shifts of the 31P resonances suggest that the phosphate linkage between G5 and A6 is no longer in the low-energy BI conformation. One-dimensional imino and phosphorus NMR studies were carried out on a number of DNA sequences containing adjacent 5'-GA-3' mismatched base pairs to investigate the sequence dependence of the conformations and base-pairing types. Type I and type II conformations have very different imino proton and 31P NMR spectral patterns that can be used to classify any sequence with adjacent GA mismatches by base-pairing and conformational type. The NMR results indicate that the conformation selected is dictated completely by the flanking sequence: 5'-pyrimidine-GA-purine-3' sequences adopt the type I conformation, while 5'-purine-GA-pyrimidine-3' sequences have the type II conformation.

Neonatal alloimmune thrombocytopenia. A case report and a review of the literature

A 32-year-old woman in her third pregnancy underwent fetal blood sampling because of a previous child with neonatal thrombocytopenia. At 33 weeks' gestation, fetal thrombocytopenia was diagnosed. Treatment was instituted antenatally with serial fetal platelet transfusions and corticosteroid therapy. Delivery was by Caesarean section at 37 weeks' gestation. Neonatal treatment included further platelet transfusion and immunoglobulin infusion. Recovery of the neonate was complete on discharge from hospital 10 days after birth. The aetiology, diagnosis, clinical presentations and therapeutic options in cases of alloimmune thrombocytopenia are discussed.

Molecular structure of cyclic diguanylic acid at 1 A resolution of two crystal forms: self-association, interactions with metal ion/planar dyes and modeling studies

Cyclic ribodiguanylic acid, c-(GpGp), is the endogenous effector regulator of cellulose synthase. Its three dimensional structure from two different crystal forms (tetragonal and trigonal) has been determined by x-ray diffraction analysis at 1 A resolution. Both structures were solved by direct methods and refined by block-matrix least squares refinement to R-factors of 0.112 (tetragonal) and 0.119 (trigonal). In both crystal forms, two independent c-(GpGp) molecules associate with each other to form a self-intercalated dimer. All four c-(GpGp) molecules have very similar backbone conformation. The riboses are in the C3'-endo pucker with pseudorotation angles ranging from -7.2 degrees to 16.5 degrees and the bases have anti glycosyl chi angles (-175.5 degrees to 179.7 degrees). In the tetragonal form, a hydrated cobalt ion is found to coordinate to two N7 atoms of adjacent guanines, forcing these two guanines to destack with a large dihedral angle (33 degrees). This metal coordination mechanism has been noted previously in other Pt- or Co-GMP complexes and may be relevant to the binding of the anticancer drug cisplatin to a GpG sequence in DNA. A model of the adduct between cisplatin and a d(CAATGGATTG) duplex has been constructed in which the induced bending of the DNA helix at the Pt crosslinking site is 33 degrees, consistent with earlier electrophoretic analyses. Moreover, c-(GpGp) exhibits unusual spectral properties not seen in other cyclic dinucleotides. It interacts with planar organic intercalator molecules in ways similar to double helical DNA. We propose a cage-like model consisting of a tetrameric c-(GpGp) aggregate in which a large cavity (host molecule) is generated to afford a binding site for certain planar intercalators (guests molecules). The aggregate likely uses a hydrogen bonding scheme the same as that found in the G-quartet molecules, e.g., telomere DNA. The conformation of c-(GpGp) also suggests that certain nearest-neighbor intercalators may be synthesized on the basis of its unique molecular framework. Modeling studies have been carried out to test this hypothesis.

Structural effects of the C2-methylhypoxanthine:cytosine base pair in B-DNA: A combined NMR and X-ray diffraction study of d(CGC[m2I]AATTCGCG)

C2-Methylhypoxanthine (m2I) is a synthetic analog of guanine with the N2-amino group replaced by a methyl group. We have studied the structural consequence of the m2I incorporation in DNA by a combination of X-ray crystallographic, NMR, and enzymatic analyses. The crystal structure of d(CGC[m2I]AATTCGCG) has been solved and refined to an R factor of 20.7% at 2.25-A resolution. In the DNA duplex, the two independent m2I:C base pairs maintain the Watson-Crick scheme. While the C2-methyl group of m2I is in van der Waals contact with the O2 of the base-paired cytosine, it only causes the base pair to have slightly higher propeller twist and buckle angles. Its solution structure was analyzed by the NMR refinement procedure SPEDREF [Robinson, H., & Wang, A. H.-J. (1992) Biochemistry 31, 3524-3533] using 2D nuclear Overhauser effect data. Two starting models, a relaxed fiber model and an X-ray model, were subjected to the NOE-constrained refinement using 1518 NOE cross-peak integrals to arrive at the final models with (NOE) R factors of 13.8% and 14.3%, respectively. The RMSD between the two refined models (all atoms included) is 1.23 A, which presently seems to be near the limit of convergence of NOE-based refinement. The local structures of the two models are in better agreement as measured by the RMSD of the dinucleotide steps, falling in the range 0.54-0.98 A. Both refined solution structures confirm that the m2I dodecamer structure is of the B-DNA type with a narrow minor groove at the AT region, as observed in the crystal. However, significant differences exist between the crystal and solution structures in parameters such as pseudorotation angles, propeller twist angles, etc. The solution structure tends to have a more uniform backbone conformation, an observation consistent with that concluded from the laser Raman study of d(CGCAAATTTGCG) [Benevides, J. M., Wang, A. H.-J., van der Marel, G. A., van Boom, J. H., & Thomas, G. J., J. (1988) Biochemistry 27, 931-938]. Three related dodecamers, d(CGCGAATTCGCG), d(CGC[m2I]AATTCGCG), and d(CGC[e6G]AATTCGCG), were tested as substrates for the restriction endonuclease EcoRI. The m2I dodecamer was active, but the e6G dodecamer was not. Our results illustrate the complementarity in terms of the structural information provided by the two methods, X-ray diffraction and NMR.

Silicon lithium niobate electro-optic waveguide modulator structures in the parallel-plate configuration

Waveguide modulators incorporating paralle-plate electrodes are investigated by computer modeling. Metal-electrode structures differ from severe optical losses that are due to surface plasmons. Siliconelectrode structures exhibit lower losses. Bandwidth is limited by the resistivity and the proximity of the electrodes. Doping the silicon improves conductivity but incireases optical absorption. Device optimization involves a trade-off between bandwidth and optical loss. Devices are fabricated by the use of substrates of silicon on sapphire, with rf sputtered lithium niobate films and plasma-enhanced chemical vapor-deposited hydrogenated amorphous silicon for the upper electrodes. The electro-optic coefficient of these lithium niobate films is ~50% of the value for bulk material. The results indicate the possibility of using these devices for combining silicon integrated circuits with waveguide modulators on a common substrate.

5'-CGA sequence is a strong motif for homo base-paired parallel-stranded DNA duplex as revealed by NMR analysis

The structure of the non-self-complementary DNA heptamer d(CGACGAC) at low pH has been determined by the quantitative NMR refinement procedure designated SPEDREF (SPEctral-Driven REFinement). Acid-base titration of the molecule indicated a prominent n = 2 pKa near 6.8. In the pH range up to 6.0, the heptamer forms a remarkably stable double helix, which was conclusively shown to be an unusual homobase-paired parallel-stranded double helix (termed II-DNA). In this II-DNA helix, the 5'-CGA trinucleotide is the structural motif that accounts for the stability, with the C+-C hemiprotonated base pair (in which C+ is N3-protonated cytosine) providing for the alignment site and the unusual interstrand G-A base stack in the GpA step furnishing the additional stabilizing forces. The exchangeable proton data from two-dimensional nuclear Overhauser effect spectroscopy are in total agreement with the refined structure. We conclude that the 5'-CGA or other related sequences (e.g., 5'-CCGA) are powerful motifs in promoting the II-DNA or II-RNA conformations that may play certain biological functions.

Two adjacent residues in staphylococcal enterotoxins A and E determine T cell receptor V beta specificity

The T cell receptor (TCR) V beta-determining region of two bacterial superantigens, staphylococcal enterotoxin A (SEA) and SEE, has been mapped to the COOH-terminal region of SEA and SEE using a panel of recombinant SEA/SEE hybrids. Total TCR V beta mRNA enrichment in human peripheral blood T cell cultures was determined by a novel single-tube amplification technique using a redundant V beta-specific primer. SEA routinely enriched mRNA coding for hV beta 1.1, 5.3, 6.3, 6.4, 6.9, 7.3, 7.4, and 9.1, while SEE, which is 83% homologous to SEA, enriched hV beta 5.1, 6.3, 6.4, 6.9, and 8.1 mRNA. Exchanging residues 206 and 207 was sufficient to convert in toto the TCR V beta response of human peripheral T lymphocytes. In addition, an SEA-reactive murine T cell line, SO3 (mV beta 17), unresponsive to wild-type SEE responded to SEE-S206N207, while an SEE-specific human T cell line, Jurkat (hV beta 8.1), unresponsive to SEA was stimulated strongly by SEA-P206D207. Exchanging all other regions of SEA and SEE except residues 206 and 207 did little to change the V beta response. Thus, the V beta binding region appears to be a stable, discrete domain localized within the COOH-terminal region that is largely unaffected by the considerable amino acid variability between SEA and SEE. This region may interact directly with TCR V beta.

Unusual DNA conformation at low pH revealed by NMR: parallel-stranded DNA duplex with homo base pairs

We have investigated the conformational potentials of several DNA oligonucleotides containing sequences related to 5'-CGA in neutral pH and low pH (< 5.0) conditions. One-dimensional proton NMR spectra show that d(CGATCG), d(TCGATCGA), and d(CGATCGATCG) exhibit new sets of resonances at low pH (approximately 3.8-4.4), when compared to those from the neutral pH samples. The low pH form and the neutral pH form are in slow equilibrium. Analyses of the data suggest that these sequences under low pH conditions adopt structures distinct from B-DNA. Two-dimensional nuclear Overhauser effect spectroscopy (2D NOESY) data from the DNA hexamer d(CGATCG) of the neutral and low pH samples were used to analyze their respective structures in solution. An iterative NOE spectral-driven refinement procedure, SPEDREF [Robinson, H., & Wang, A. H.-J. (1992) Biochemistry 31, 3524-3533], was used to show that the neutral pH structure is close to canonical B-DNA. In contrast, analysis of the low pH form using the 2D NOESY data suggests that its structure is consistent with a right-handed parallel-stranded (PS) double helix with symmetrical non-Watson-Crick (C+:C, G:G, A:A, T:T) homo base pairs. Supporting evidence for the PS helix includes the asymmetric inversion-recovery relaxation times associated with the two ends of the helix. The structure is favored by the 5'-CGA sequence in which the cytosines provide the C+:C pairing for the nucleation step and the GpA step is significantly stabilized by the interstrand G-A stacking interactions.(ABSTRACT TRUNCATED AT 250 WORDS)

Fragile X syndrome without CCG amplification has an FMR1 deletion

We describe a patient with typical clinical features of the fragile X syndrome, but without cytogenetic expression of the fragile X or an amplified CCG trinucleotide repeat fragment. The patient has a previously uncharacterized submicroscopic deletion encompassing the CCG repeat, the entire FMR1 gene and about 2.5 megabases of flanking sequences. This finding confirms that the fragile X phenotype can exist, without amplification of the CCG repeat or cytogenetic expression of the fragile X, and that fragile X syndrome is a genetically homogeneous disorder involving FMR1. We also found random X-inactivation in the mother of the patient who was shown to be a carrier of this deletion.

Zinc regulates the function of two superantigens

Staphylococcal enterotoxins bind with high affinity to class II major histocompatibility complex proteins and subsequently stimulate large numbers of T cells via the V beta portion of the T-cell receptor. Binding of enterotoxin A and enterotoxin E to HLA-DR was completely abolished by low levels of EDTA, whereas binding of toxic shock toxin was unaffected. Addition of Zn2+ to as little as 2 microM excess over EDTA completely reconstituted binding, but Ca2+, Mg2+, Cu2+, Fe2+, and Mn2+ had no effect. The dissociation constant (Kd) of 65Zn2+ binding to a single site on purified enterotoxin A was 2 microM, and addition of purified HLA-DR1 did not alter the Kd, indicating that the binding site was exclusive to enterotoxin A. In the presence of saturating levels of zinc the Kd for enterotoxin A binding to purified HLA-DR1 was 25 nM. Thus, zinc binding is an essential first step in the formation of the major histocompatibility complex binding domain of at least two bacterial superantigens. Given the measured Kd of zinc binding to enterotoxin A, serum levels of free zinc (0.2-1.0 microM) may well regulate the toxic sequelae by these two superantigens.

Population screening for fragile X

A screening programme to detect fragile X syndrome has been operating in New South Wales, Australia, since 1984. The aim of this programme is to find previously unidentified individuals with the syndrome so that their extended families can be properly informed of the risks before making decisions about childbearing. 14,225 individuals attending adult and child facilities for the intellectually handicapped have been screened, of whom 8172 have been offered testing for the fragile X syndrome with a 79% uptake of the service. 253 probands were found, and in the extended families 818 females at 25-100% risk of being carriers were interviewed and counselled. Continuing contact was maintained and prenatal diagnosis was offered. The effect of the programme was assessed in a subgroup of 90 individuals, most of whom were appreciative of the service and felt that they had been adequately informed. The influence of knowing the diagnosis and its genetic implications were also assessed, the main consequences being a 26% reduction in births and a 61% uptake of prenatal diagnosis. Improved techniques for diagnosis of fragile X have benefited the families identified and counselled, suggesting that systematic screening for fragile X should be an essential component of community genetic services.

Mortality in the fragile X syndrome: preliminary data

Mortality was studied among 348 males and 433 females who had or who carried the gene for the fragile X syndrome. The average age of death was about 12 years lower than in the general population for both men and women but this was likely a bias of ascertainment. The commonest causes of death were cardiovascular, cerebrovascular and malignant disease similar to those in the general population. No evidence for any specific disease susceptibility was found in this preliminary study.

A simple spectral-driven procedure for the refinement of DNA structures by NMR spectroscopy

We have developed a simple and quantitative procedure (SPEDREF) for the refinement of DNA structures using experimental two-dimensional nuclear Overhauser effect (2D NOE) data. The procedure calculates the simulated 2D NOE spectrum using the full matrix relaxation method on the basis of a molecular model. The volume of all NOE peaks is measured and compared between the experimental and the calculated spectra. The difference of the experimental and simulated volumes is minimized by a conjugated gradient procedure to adjust the interproton distances in the model. An agreement factor (analogous to the crystallographic R-factor) is used to monitor the progress of the refinement. The procedure is an The agreement is considered to be complete when several parameters, including the R-factor, the energy associated with the molecule, the local conformation (as judged by the sugar pseudorotation), and the global conformation (as judged by the helical x-displacement), are refined to their respective convergence. With the B-DNA structure of d(CGATCG) as an example, we show that DNA structure may be refined to produce calculated NOE spectra that are in excellent agreement with the experimental 2D NOE spectra. This is judged to be effective by the low R-factor of approximately 15%. Moreover, we demonstrate that not only are NOE data very powerful in providing details of the local structure but, with appropriate weighting of the NOE constraints, the global structure of the DNA double helix can also be determined, even when starting with a grossly different model. The reliability and limitations of a DNA structure as determined by NMR spectroscopy are discussed.

New X-linked syndrome of mental retardation, gynecomastia, and obesity is linked to DXS255

We describe 14 males from 3 successive generations in a family who have X-linked mental retardation (XLMR), obesity, gynecomastia, speech difficulties, emotional lability, tapering fingers, and small feet. Linkage analysis using markers spread along the X chromosome demonstrated a gene localisation close to the centromere. Maximum lod scores for markers near the centromere, all at theta = 0.00, were 1.36 for DXS72, and 1.46 for DXYS1. The closest flanking markers which showed recombination were DXS84 and DXS94, defining the physical localisation within Xp21.1-q22. DXS255 was fully informative with lod-1 confidence interval for theta of 0.00-0.12. Clinical findings and linkage data in this family distinguish it from the Börjeson-Forssman-Lehmann syndrome and other previously described XLMR syndromes.

Clinical screening score for the fragile X (Martin-Bell) syndrome

A clinical score based on the manifestations of the fragile(X) syndrome has been formulated and applied to all individuals included in a fragile(X) case finding program in New South Wales. The total score can vary from 0 to 10. Individuals are scored 0, 1, or 2 in each of 5 categories considered indicative of the fragile(X) phenotype: family history of intellectual handicap, face length, ear configuration, personality, and body habitus. In a study of 1,206 individuals where the clinical scores were prospective (i.e., they had been given before the cytogenetic results were known) the percentage of those with the fragile(X) increased from 0.6% of those with scores of 4 or less to 14.6% with scores 5-7 and to 67% of those with scores 8-10. We have found the score simple to use in the circumstances where screening takes place (sheltered workshops and schools) and have reduced the number of individuals tested cytogenetically by 45%.

Binding of the antitumor drug nogalamycin and its derivatives to DNA: structural comparison

The three-dimensional molecular structures of the complexes between a novel antitumor drug nogalamycin and its derivative U-58872 with a modified DNA hexamer d[m5CGT(pS)Am5CG] have been determined at 1.7- and 1.8-A resolution, respectively, by X-ray diffraction analyses. Both structures (in space group P6(1)) have been refined with constrained refinement procedure to final R factors of 0.208 (3386 reflections) and 0.196 (2143 reflections). In both complexes, two nogalamycins bind to the DNA hexamer double helix in a 2:1 ratio with the elongated aglycon chromophore intercalated between the CpG steps at both ends of the helix. The aglycon chromophore spans across the GC Watson-Crick base pairs with its nogalose lying in the minor groove and the aminoglucose lying in the major groove of the distorted B-DNA double helix. Most of the sugars remain in the C2'-endo pucker family, except three deoxycytidine residues (terminal C1, C7, and internal C5). All nucleotides are in the anti conformation. Specific hydrogen bonds are found in the complex between the drug and guanine-cytosine bases in both grooves of the helix. One hydroxyl group of the aminoglucose donates a hydrogen bond to the N7 of guanine, while the other receives a hydrogen bond from the N4 amino group of cytosine. The orientation of these two hydrogen bonds suggests that nogalamycin prefers a GC base pair with its aglycon chromophore intercalating at the 5'-side of a guanine (between NpG), or at the 3'-side of a cytosine (between CpN) with the sugars pointing toward the GC base pair. The binding of nogalamycin to DNA requires that the base pairs in DNA open up transiently to allow the bulky sugars to go through, suggesting that nogalamycin prefers GC sequences embedded in a stretch of AT sequences.

NMR studies on the binding of antitumor drug nogalamycin to DNA hexamer d(CGTACG)

The interactions between a novel antitumor drug nogalamycin with the self-complementary DNA hexamer d(CGTACG) have been studied by 500 MHz two dimensional proton nuclear magnetic resonance spectroscopy. When two nogalamycins are mixed with the DNA hexamer duplex in a 2:1 ratio, a symmetrical complex is formed. All non-exchangeable proton resonances (except H5' & H5") of this complex have been assigned using 2D-COSY and 2D-NOESY methods at pH 7.0. The observed NOE cross peaks are fully consistent with the 1.3 A resolution x-ray crystal structure (Liaw et al., Biochemistry 28, 9913-9918, 1989) in which the elongated aglycone chromophore is intercalated between the CpG steps at both ends of the helix. The aglycone chromophore spans across the GC Watson-Crick base pairs with its nogalose lying in the minor groove and the aminoglucose lying in the major groove of the distorted B-DNA double helix. The binding conformation suggests that specific hydrogen bonds exist in the complex between the drug and guanine-cytosine bases in both grooves of the helix. When only one drug per DNA duplex is present in solution, there are three molecular species (free DNA, 1:1 complex and 2:1 complex) in slow exchange on the NMR time scale. This equilibrium is temperature dependent. At high temperature the free DNA hexamer duplex and the 1:1 complex are completely destabilized such that at 65 degrees C only free single-stranded DNA and the 2:1 complex co-exist. At 35 degrees C the equilibrium between free DNA and the 1:1 complex is relatively fast, while that between the 1:1 complex and the 2:1 complex is slow. This may be rationalized by the fact that the binding of nogalamycin to DNA requires that the base pairs in DNA open up transiently to allow the bulky sugars to go through. A separate study of the 2:1 complex at low pH showed that the terminal GC base pair is destabilized.