Novel DNMT3A germline mutations are associated with inherited Tatton-Brown-Rahman syndrome.

Tatton-Brown-Rahman syndrome (TBRS) was recently described in 13 isolated cases with de novo mutations in the DNMT3A gene. This autosomal dominant condition is characterized by tall stature, intellectual disability and a distinctive facial appearance. Here, we report six cases of inherited TBRS caused by novel DNMT3A germline mutations. The affected individuals belong to two sib-ships: four from an Old Order Amish family in America and two from a French Canadian family in Canada. All of them presented with characteristic features of TBRS, including dysmorphic facial features, increased height, intellectual disability, and variable additional features. We performed clinical exome sequencing and identified two mutations in the DNMT3A gene, a c.2312G>A (p.Arg771Gln) missense mutation in the Amish family and a c.2296_2297delAA (p.Lys766Glufs*15) small deletion in the French Canadian family. Parental DNA analysis by Sanger sequencing revealed that the Amish mutation was inherited from the healthy mosaic father. This study reflects the first cases with inherited TBRS and expands the phenotypic spectrum of TBRS.

The role of arsenic in the hydrolysis and DNA metalation processes in an arsenous acid-platinum(ii) anticancer complex.

Platinum(ii)-based molecules are the most commonly used anticancer drugs in the chemotherapeutic treatment of tumours but possess serious side effects and some cancer types exhibit resistance with respect to these compounds (e.g. cisplatin). For these reasons, the research of new compounds that can bypass this limitation is in continuous development. Recently, mixed Pt(ii)-As(iii) systems have been synthesized and tested as potential anticancer agents. The mechanism of action of these kinds of drugs is unclear. Since in other platinum(ii) containing drugs, hydrolysis plays an important role in the activation of the compound before it reaches DNA, we have explored the aquation process using density functional theory (DFT), focusing our attention on the arsenoplatin complex, [Pt(µ-NHC(CH3)O)2ClAs(OH)2]. As DNA is believed to be the cellular target for Pt anticancer drugs, the metalation mechanism of DNA purine bases has been also investigated. Also for this new drug it appears that guanine is the preferred site with respect to adenine as with other platinum-containing compounds. A comparison with cisplatin is performed in order to highlight the contribution of arsenic in the anticancer activity of this new proposed anticancer agent.

Mechanistic investigation of trimethylamine-N-oxide reduction catalysed by biomimetic molybdenum enzyme models.

In this paper, we report a theoretical investigation of the reduction reaction mechanism of Me3NO using molybdenum containing systems that are functional and structural analogues of trimethylamine N-oxide reductase mononuclear molybdenum enzyme. The reactivity of the monooxomolybdenum(IV) benzenedithiolato complex and its derivatives to carbamoyl (t-BuNHCO) and acylamino (t-BuCONH) substituents on the benzene rings in both cis and trans arrangements was explored. The calculated energy profiles describing the steps of two mechanisms of attack considered viable (named cis- and trans-attack) by the Me3NO substrate at cis and trans positions with respect to the oxo ligand show that the attack on cis is energetically more favourable than the attack on trans. Along the pathway for the cis-attack the first step of the reaction, that is rate-determining for all the studied compounds, is the approach of the substrate to the Mo centre in cis to the oxo ligand that causes a distortion of the initial square-pyramidal geometry of the complex. The reaction steps involved in the trans position attack were also explored. Calculations confirm that, as previously suggested, the introduction of ligands able to form intramolecular NH···S hydrogen bonds accelerates the reduction of the Me3NO substrate and contributes to the tuning of the reactivity of molybdoenzyme models.

The working mechanism of the ß-carbonic anhydrase degrading carbonyl sulphide (COSase): a theoretical study.

In order to give insights into the working mechanism of the novel characterized enzyme carbonyl sulphide hydrolase (COSase), which efficiently converts COS into H2S and CO2, we have performed a detailed theoretical investigation using the framework of density functional theory (using B3LYP and M06 exchange-correlation functionals) by the cluster model approach. In the final part of the reaction the metal ion is unable to form a pentacoordinated species. The B3LYP-D3 and M06 potential energy surfaces have a very similar shape. The elucidation of the catalytic reduction of COS is important in view of its role in environmental chemistry.

Insight into the promiscuous activity of human carbonic anhydrase against the cyanic acid substrate from a combined QM and QM/MM investigation.

The promiscuous activity of human carbonic anhydrase (hCAII) against a non-physiological cyanic acid substrate has been investigated by using a combined QM and QM/MM level of theory. Results show that the hCAII is able to hydrate the cyanic acid by a reaction mechanism similar to that of the CO2 native substrate. The energy barrier for the nucleophilic attack is found to be 15.6 and 4.3 kcal mol(-1) at QM and QM/MM levels, respectively. This result underlines the importance of taking into account the surrounding residues around the active site in the presence of the substrate having small molecular sizes. The carbamate is strongly stabilized with respect to the bicarbonate of the native substrate indicating a more difficult release of the reaction product.

The Cuban program for predictive testing of SCA2: 11 years and 768 individuals to learn from.

Having reported the world's highest prevalence of spinocerebellar ataxia type 2 (SCA2), health professionals in Cuba developed a program for the predictive testing of this condition. Between February 2001 and December 2011, a total of 1050 individuals requested their inclusion in the presymptomatic testing (PST) program. Their medical records were retrospectively analyzed in the present descriptive study. A total of 768 participants completed the protocol, 204 withdrew and 78 were excluded. The PST uptake was 24.91%. Females predominated and 70.96% had negative test results. Their main motivations were risk assessment in their descendants, physical and psychological preparation to cope with the disease and planning for the future. The profile of Cuban participants in the predictive testing program is similar to the one reported for other programs all over the world, nevertheless the genetic counseling practice at the community level is a distinctive aspect, which is valuable in providing at-risk individuals with wide and proper knowledge before their testing inclusion request. The SCA2 predictive testing program has high uptake rates and is renowned in our population. Future research is needed to assess the long-term psychological impact in the participants, their partners and relatives.

Hemodynamic versus adrenergic control of cat right ventricular hypertrophy.

The purpose of this study was to determine whether cardiac hypertrophy in response to hemodynamic overloading is a primary result of the increased load or is instead a secondary result of such other factors as concurrent sympathetic activation. To make this distinction, four experiments were done; the major experimental result, cardiac hypertrophy, was assessed in terms of ventricular mass and cardiocyte cross-sectional area. In the first experiment, the cat right ventricle was loaded differentially by pressure overloading the ventricle, while unloading a constituent papillary muscle; this model was used to ask whether any endogenous or exogenous substance caused uniform hypertrophy, or whether locally appropriate load responses caused ventricular hypertrophy with papillary muscle atrophy. The latter result obtained, both when each aspect of differential loading was simultaneous and when a previously hypertrophied papillary muscle was unloaded in a pressure overloaded right ventricle. In the second experiment, epicardial denervation and then pressure overloading was used to assess the role of local neurogenic catecholamines in the genesis of hypertrophy. The degree of hypertrophy caused by these procedures was the same as that caused by pressure overloading alone. In the third and fourth experiments, beta-adrenoceptor or alpha-adrenoceptor blockade was produced before and maintained during pressure overloading. The hypertrophic response did not differ in either case from that caused by pressure overloading without adrenoceptor blockade. These experiments demonstrate the following: first, cardiac hypertrophy is a local response to increased load, so that any factor serving as a mediator of this response must be either locally generated or selectively active only in those cardiocytes in which stress and/or strain are increased; second, catecholamines are not that mediator, in that adrenergic activation is neither necessary for nor importantly modifies the cardiac hypertrophic response to an increased hemodynamic load.

On the copper(II) ion coordination by prion protein HGGGW pentapeptide model.

The interaction of the octapeptide domain of the prion protein with the transition-metal-ion Cu2+ was studied at the DFT level by using the HGGGW pentapeptide as a model to mimic the PHGGGWGQ octarepeat sequence. Ten complexes, in which the metal ion exhibits different coordinations, were considered. Our results indicate that the lowest-energy structure is characterized by a tetracoordinated metal center and that this tendency of the ion to assume the square planar geometry is strong enough to prevent the addition of a further water molecule in its coordination sphere. The role of tryptophan was found to cause a lowering of the system energy due to the stabilizing effect of the electrostatic interaction between the Trp aromatic indole and histidine imidazole rings.

Cardiac atrioventricular junctional tissues in hearts from infants who died suddenly.

The cause of sudden infant death syndrome is not known at present. Most agree that in the majority of cases it involves primary apnea. However, cardiac abnormalities probably account for a subset of these deaths. An investigation into the structure of the atrioventricular (AV) junctional tissues of the heart would provide insight into the frequency of sudden death in infants that might result from abnormal cardiac morphology. The hearts of seven infants who died from diagnosed sudden infant death syndrome were examined by serially sectioning and studying this critical region of the heart. The hearts of these infants could be divided into three groups on the basis of their morphologic features. In the first group, represented by two cases, there were marked variations from normal, the most striking feature being the presence of accessory pathways. In the second group, represented by four cases, the AV junctional tissues were not fully mature and clusters of AV nodal and bundle cells were dispersed throughout the anulus fibrosus. In the third group, the structure of the junctional tissues was normal. There remains a distinct subset of infants who might have died suddenly and unexpectedly from cardiac abnormalities that needs to be more completely defined.

Interaction of cysteine with Cu2+ and group IIb (Zn2+, Cd2+, Hg2+) metal cations: a theoretical study.

The structure and energetics of complexes obtained upon interaction between cysteine and Zn2+, Cd2+, Hg2+ and Cu2+ cations were studied using quantum chemical density functional theory calculations with the 6-311++G** orbital basis set and relativistic pseudopotentials for the cations. Different coordination sites for metal ions on several cysteine conformers were considered. In their lowest energy complexes with the amino acid, the Zn2+ and Cd2+ cations appear to be three-coordinated to carbonyl oxygen, nitrogen and sulfur atoms, whereas the Cu2+ and Hg2+ ions are coordinated to both the carbonyl oxygen and sulfur atoms of one of the zwitterion forms of the amino acid. Bonds of metal cations with the coordination sites are mainly ionic except those established with sulfur, which show a small covalent character that become most significant when Cu2+ and Hg2+ are involved. The order of metal ion affinity proposed is Cu>Zn>Hg>Cd.

Potassium measurements in the extracellular spaces of normal and failing cat myocardium.

After periods of quiescence, papillary muscles and trabeculae from normal and hypertrophied-failing cat hearts were subjected to ionic stress induced by stimulation (drive) at different frequencies. Patterns of change in extracellular potassium concentration were measured using ion-selective microelectrodes and were shown to be significantly different in certain key parameters. In both types of tissue, extracellular potassium activity initially increased from the level in the bathing medium, reached a peak, and then returned toward the original levels. However, the time for this to occur was significantly longer in the hypertrophied-failing muscles than in the normal controls. Also, after more than 5 min of drive, the potassium activity in the extracellular spaces was significantly higher in the hypertrophied-failing tissue than in the normal tissue. The results of these experiments indicate that there may be quantitative differences between normal and hypertrophied-failing cardiac muscles with regard to the regulation of ionic balance.

Medicinal chemistry based on the sugar code: fundamentals of lectinology and experimental strategies with lectins as targets.

Theoretical calculations reveal that oligosaccharides are second to no other class of biochemical oligomery in terms of coding capacity. As integral part of cellular glycoconjugates they can serve as recognitive units for receptors (lectins). Having first been detected in plants, lectins are present ubiquitously. Remarkably for this field, they serve as bacterial and viral adhesins. Following a description of these branches of lectinology to illustrate history, current status and potential for medicinal chemistry, we document that lectins are involved in a wide variety of biochemical processes including intra- and intercellular glycoconjugate trafficking, initiation of signal transduction affecting e. g. growth regulation and cell adhesion in animals. It is thus justified to compare crucial carbohydrate epitopes with the postal code ensuring correct mail routing and delivery. In view of the functional relevance of lectins the design of high-affinity reagents to occupy their carbohydrate recognition domains offers the perspective for an attractive source of new drugs. Their applications can be supposed to encompass the use as cell-type-selective determinant for targeted drug delivery and as blocking devices in anti-adhesion therapy during infections and inflammatory disease. To master the task of devising custom-made glycans/glycomimetics for this purpose, the individual enthalpic and entropic contributions in the molecular rendezvous between the sugar receptor under scrutiny and its ligand in the presence of solvent molecules undergoing positional rearrangements need to be understood and rationally exploited. As remunerative means to this end, cleverly orchestrated deployment of a panel of methods is essential. Concerning the carbohydrate ligand, its topological parameters and flexibility are assessed by the combination of computer-assisted molecular-mechanics and molecular-dynamics calculations and NMR-spectroscopic measurements. In the presence of the receptor, the latter technique will provide insights into conformational aspects of the bound ligand and into spatial vicinity of the ligand to distinct side chains of amino acids establishing the binding site in solution. Also in solution, the hydrogen-bonding pattern in the complex can be mapped with monodeoxy and monofluoro derivatives of the oligosaccharide. Together with X-ray crystallographic and microcalorimetric studies the limits of a feasible affinity enhancement can be systematically probed. With galactoside-binding lectins as instructive mo del, recent progress in this area of drug design will be documented, emphasizing the general applicability of the outlined interdisciplinary approach.

A study of ruptured tubal ectopic pregnancy.

OBJECTIVE: Ectopic pregnancy continues to be a leading cause of maternal morbidity and of reduced childbearing potential among women of reproductive age. Because of tubal rupture it is still the main cause of pregnancy-related death during the first trimester. The purpose of our study was to evaluate factors that may predispose a woman to rupture of a tubal ectopic pregnancy. METHODS: In this retrospective study of 693 ectopic pregnancies from three McGill University teaching hospitals, we compared risk factors, preoperative ultrasound, and serum hCG levels between cases with ruptured and unruptured tubal ectopic pregnancy. RESULTS: The age and the number of pregnancies among the two groups of women were similar. The gestational age of women with an unruptured tube was 6.9 +/- 1.9 weeks, and of those with a ruptured tube, the gestational age was 7.2 +/- 2.2 weeks. Tubal rupture was encountered more often in women with at least one child than in childless women. History of ectopic pregnancy was found in 35% of women with an unruptured tubal pregnancy and in 26% of those with a ruptured tube. Serum hCG levels at the time of treatment were not significantly different among the two groups of women. Eleven percent of women with a ruptured tube had serum beta-hCG levels of less that 100 IU/L. CONCLUSION: Tubal rupture is encountered more often in women with no history of ectopic pregnancy and in those with at least one child. This suggests that ectopic pregnancy is less suspected in these women. Tubal rupture is encountered less often in ampullary pregnancy and in small ectopic pregnancies. There is no correlation between serum beta-hCG levels and tubal rupture, and rupture can occur even when serum beta-hCG levels are very low.

Isolated clubfoot diagnosed prenatally: is karyotyping indicated?

OBJECTIVE: To evaluate the appropriateness of fetal karyotyping after prenatal sonographic diagnosis of isolated unilateral or bilateral clubfoot. METHODS: We retrospectively reviewed a database of fetal abnormalities diagnosed by ultrasound at a single tertiary referral center from July 1994 to March 1999 for cases of unilateral or bilateral clubfoot. Fetuses who had additional anomalies diagnosed prenatally, after targeted sonographic fetal anatomy surveys, were excluded. Outcome results included fetal karyotype diagnosed by amniocentesis, or newborn physical examination by a pediatrician. RESULTS: During the 5-year period, 5,731 fetal abnormalities were diagnosed from more than 27,000 targeted prenatal ultrasound examinations. There were 51 cases of isolated clubfoot. The mean maternal age at diagnosis was 30.5 years. The mean gestational age at diagnosis was 21.6 weeks. Twenty-three of the women (45%) were at increased risk of fetal aneuploidy, on the basis of advanced maternal age or abnormal maternal serum screening. Six women (12%) had positive family histories of clubfoot; however, no cases of aneuploidy were found by fetal karyotype evaluation or newborn physical examination. All cases of clubfoot diagnosed prenatally were confirmed at newborn physical examination, and no additional malformations were detected. CONCLUSION: After prenatal diagnosis of isolated unilateral or bilateral clubfoot, there appeared to be no indication to offer karyotyping, provided that a detailed sonographic fetal anatomy survey was normal and there were no additional indications for invasive prenatal diagnoses.

Density functional computations of proton affinity and gas-phase basicity of proline.

The proton affinity and gas-phase basicity of proline were evaluated by using density functional theory coupling the B3-LYP hybrid functional with the extended 6--311++G** basis set. Cis and trans conformations of the carboxyl moiety for both exo and endo ring structures were considered for the neutral proline. The results show that the most stable structure of proline has the endo ring conformation with the carboxyl group in the cis position. The structure at the global minimum is stabilized by an intramolecular hydrogen bond. The nitrogen of the ring in the exo form is the preferred protonation site. The calculated proton affinity (924.3 kJ mol(-1)) and gas-phase basicity (894.4 kJ mol(-1)) are in very good agreement with the experimental counterparts.

A genetic linkage study of familial breast-ovarian cancer.

Linkage analysis was conducted in 17 families identified by the familial occurrence of breast and ovarian cancer using a series of 17 serologic and biochemical markers. Lod scores suggestive of linkage of breast/ovarian cancer susceptibility to the RH blood group locus on chromosome 1p were obtained. When the presence of fibrocystic disease of the breast in a first-degree relative of an affected family member was added as an indicator of susceptibility, the evidence for linkage increased. No evidence of linkage to GPT or ABO, both previously suggested to be linked to breast cancer susceptibility, was seen in this study.

Gas-phase metal ion (Li+, Na+, Cu+) affinities of glycine and alanine.

The gas-phase metal affinities of glycine and alanine for Li+, Na+ and Cu+ ions have been determined theoretically employing the hybrid B3LYP exchange-correlation functional and using extended basis sets. All computations indicate that the metal ion affinity (MIA) decreases on going from Cu+ to Li+ and Na+ for both the considered amino acids. The absolute MIA values are close to the experimental counterparts with the exception of lithium for which a deviation of about 7 kcal/mol at the B3LYP level is obtained. The optimized structures indicate that Li+, Na+ and Cu+ prefer a bidentate coordination, bonding with both nitrogen and oxygen atoms of amino acids.