Relationship between right ventricular diastolic dysfunction, right atrial phasic function and ventricular filling in pulmonary arterial hypertension

Background

In pulmonary arterial hypertension (PAH) patients, the right ventricle (RV) stiffens due to hypertrophy, fibrosis and intrinsic (sarcomeric) stiffness. In these patients, end-diastolic elastance (stiffness, Eed) is associated with parameters of disease severity and predicts mortality. However, the effect of RV stiffness on RV filling and the effect of increased filling pressures on right atrial (RA) function remain elusive.

Purpose

To examine the relationship between RV diastolic stiffness and RA phasic function and the effect of diastolic dysfunction on ventricular filling in PAH patients.

Methods

Using single-beat pressure-volume analyses we determined Eed in controls (n=31) and baseline, treatment naive PAH patients (63 idiopathic, 9 hereditary and 25 connective tissue disease associated). We also measured RA reservoir, conduit and active strain by tissue tracking on cardiac magnetic resonance images. Furthermore, interventricular dyssynchrony was defined as a right to left difference in time to peak circumferential strain >52ms (97.5th percentile in controls).

Results

End-diastolic pressure was higher in PAH patients (16±7 mmHg) than in controls (8±4 mmHg; p<0.001). Median Eed in patients was 0.635 mmHg/mL (IQR: 0.40–0.99), while in controls it was 0.20 mmHg/mL (IQR: 0.15–0.24). In comparison with controls, patients had reduced RA reservoir (14.3±5.1% vs. 19.1±4.3%; p<0.001) and conduit strain (−5.6±3.4% vs. −12.4±3.3%; p<0.001), while RA active strain was enhanced (−9.0±4.0% vs. −7.5±2.8%; p=0.019). In patients with a stiff RV (Eed above median), RA conduit strain was worse than in patients with a more compliant RV as illustrated in figure A. However, no correlation between RA active strain and Eed was observed (Spearman rho 0.06; p=0.57).

Passive filling time of the RV (end-systole until start of atrial contraction) was shorter in patients than in controls (244±136ms vs. 365±103ms; p<0.001). Higher heart rate and ventricular dyssynchrony are causes of a shorter passive filling time in patients as illustrated in figure B. When comparing patients with short vs. long passive filling time (cutoff median of 220ms), the RV passive filling volume was lower (24±15ml vs. 42±19ml; p<0.001). The active filling volume was slightly higher, although not significantly (25±17ml vs. 19±15ml; p=0.12).

Conclusion

Stiffening of the RV in PAH patients is accompanied by increased filling pressures and decreased RA conduit strain, while there is no correlation between Eed and RA active strain. Higher heart rate and ventricular dyssynchrony lead to shorter passive filling time of the RV, which in turn leads to lower passive filling volume. In contrast, the active filling volume is preserved in these patients.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): The Netherlands Organization for Scientific Research

The effect of pulmonary arterial hypertension specific treatment on the left ventricle in patients with pulmonary arterial hypertension

Background

Pulmonary arterial hypertension (PAH) is characterized by right ventricular (RV) pressure overload, leading to RV dilation, failure and death. In the course of the disease, the left ventricle (LV) is often impaired, due to interventricular interaction. Although the impact of PAH treatment on the RV has been well described, less is known on the LV.

Purpose

To examine effects of advanced PAH treatments on the volumes, function and strain of the left atrium and ventricle.

Methods

This is a retrospective study. All patients underwent CMR and right heart catheterization, both at diagnosis and at 12-months follow up. Ventricular volumes and LV filling rate were calculated from the stack of short axis cine images using Simpsons method while left atrial (LA) volumes from the 4-chamber cine images using the area-length method. Tissue tracking was used for the evaluation of myocardial deformation. The LV endocardial and epicardial borders were manually delineated in all analysed sections with the initial contour set at end-diastole. All analyses were performed offline using dedicated software.

Results

In total, 66 patients (mean age 56.3±17.9 years, 67%women, 77%idiopathic and heritable PAH, 23% connective tissue disease associated PAH) and 29 normal controls were included. The improvement in metrics of right and left heart size and function after the initiation of advanced PAH treatment, are presented in panel A. Of note, LV stroke volume was markedly increased (54.6±19.6ml at baseline vs 70.8±21.7ml at follow up, p<0.0001) to reach controls. LV filling was markedly increased in latter two-thirds of the diastolic phase (panel B), especially at atrial kick point (arrow). Change in LA max volume was associated with changes in diastolic filling (r=0.354, p=0.004), LV end-diastolic and end-systolic volumes and stroke volume. These correlations were more robust in patients that increased LV filling compared to those that failed to increase LV filling (panels C-E). No association between changes in LV circumferential strain and LV volume load was observed. A weak correlation of change of LV peak longitudinal strain with stroke volume (r=−0.345, p=0.006), LV end diastolic volume (r=−0.284, p=0.027), LV ejection fraction (r=−0.337, p=0.008) and LA maximum area (r=−0.447, p<0.0001) was observed. The changes of LV strain showed no correlation with the changes in patients' haemodynamics.

Conclusion

Improvement in stroke volume after the initiation of advanced PAH treatment is associated with an increase in LA size, LV end diastolic volume and normalisation of strain. This reflects the improved filling state of the left ventricle and the potential of the left atrium to monitor treatment effects.

Changes after PAH treatment

Funding Acknowledgement

Type of funding source: None

Effect of macitentan on left ventricular (LV) function in pulmonary arterial hypertension (PAH): results from REPAIR

Introduction

PAH impacts right ventricular (RV) structure and function but also leads to changes in the LV due to RV/LV interaction and underfilling. REPAIR, the first PAH study to use a primary endpoint assessed by cardiac MRI (cMRI), reported that RV stroke volume (RVSV) increased by 12 mL and pulmonary vascular resistance (PVR) decreased by 38% from baseline (BL) to Week 26 with macitentan.

Purpose

To assess the effect of macitentan on LV function in patients with PAH.

Methods

REPAIR (NCT02310672) was a 52-week, multicentre, open-label, single-arm, phase 4 study assessing the effect of macitentan primarily on RV structure and function, determined by cMRI and right heart catheterisation. Macitentan 10 mg was initiated in treatment-naïve patients, in patients receiving stable background phosphodiesterase type-5 inhibitor (PDE5i) at BL, or in initial combination with PDE5i. Exploratory LV endpoints were assessed by cMRI at Weeks 26 and 52. Safety was assessed up to end of study treatment +30 days in all patients who received ≥1 dose of macitentan (N=87). Patients with BL and Week 26 assessments for both PVR and RVSV were included in the modified Full Analysis Set (mFAS; N=71).

Results

In the mFAS, 57 (80%) patients were female. At BL, median age was 45 years; median (Q1, Q3) six-minute walk distance was 395 (323, 483) m; 48%/51% of patients were WHO functional class II/III; 59% had idiopathic PAH. Compared to BL, at Weeks 26 and 52 there were significant changes in LV cMRI parameters (table). The most common AEs were peripheral oedema (22%), headache (21%) and dizziness (14%).

Conclusions

Macitentan led to improvements in LV mass, volume and function, including clinically-relevant increases in LV stroke volume, at both 26 and 52 weeks in patients with PAH. Safety was consistent with other macitentan clinical trial data.

Funding Acknowledgement

Type of funding source: Other. Main funding source(s): Actelion Pharmaceuticals Ltd

Single photon emitters in exfoliated WSe2 structures

Crystal structure imperfections in solids often act as efficient carrier trapping centres, which, when suitably isolated, act as sources of single photon emission. The best known examples of such attractive imperfections are well-width or composition fluctuations in semiconductor heterostructures (resulting in the formation of quantum dots) and coloured centres in wide-bandgap materials such as diamond. In the recently investigated thin films of layered compounds, the crystal imperfections may logically be expected to appear at the edges of commonly investigated few-layer flakes of these materials exfoliated on alien substrates. Here, we report comprehensive optical micro-spectroscopy studies of thin layers of tungsten diselenide (WSe2), a representative semiconducting dichalcogenide with a bandgap in the visible spectral range. At the edges of WSe2 flakes (transferred onto Si/SiO2 substrates) we discover centres that, at low temperatures, give rise to sharp emission lines (100 μeV linewidth). These narrow emission lines reveal the effect of photon antibunching, the unambiguous attribute of single photon emitters. The optical response of these emitters is inherently linked to the two-dimensional properties of the WSe2 monolayer, as they both give rise to luminescence in the same energy range, have nearly identical excitation spectra and have very similar, characteristically large Zeeman effects. With advances in the structural control of edge imperfections, thin films of WSe2 may provide added functionalities that are relevant for the domain of quantum optoelectronics.

Influence of additives on the structure of surfactant-free microemulsions

In surfactant-free microemulsions, the combination ethanol/antagonistic salt behaves like a surfactant.

Dependence of the structural, transport and magnetic properties of Tl(1-y)Fe(2-z)(Se(1-x)S(x))2 with isovalent substitution of Se by S

The effect of selenium substitution by sulfur in the Tl(1-y)Fe(2-z)Se(2) antiferromagnet was studied by x-ray and electron diffraction, magnetization and transport measurements. Tl(0.8)Fe(1.5)(Se(1-x)S(x))(2) (nominal composition) solid solution was synthesized in the full x range (0 ≤ x(S) ≤ 1) using the sealed tube technique. No superconductivity was found down to 4.2 K in the series despite the fact that the optimal crystallographic parameters, determined by Rietveld refinements, are reached in the series (i.e. the Fe-(Se, S) interplane height and (Se, S)-Fe-(Se, S) angle for which the critical superconducting transition T(c) is usually maximal in pnictides). A quasi-full Tl site (y ~ 0.05) compared to significant alkaline deficiency (y = 0.2-0.3) in analogous A(1-y)Fe(2-z)Se(2) (A = K, Rb, Cs), and the resulting differences in iron valency, density of states and doping, are suggested as an explanation for this absence of superconductivity. Transmission electron microscopy confirmed the existence of an ordered iron vacancies network in the samples of the Tl(0.8)Fe(1.5)(Se(1-x)S(x))(2) series in the form of the tetragonal √5a × √5a × c superstructure (I4/m). The Néel temperature (T(N)) indicating the onset of antiferromagnetism order in this √5a × √5a × c supercell is found to decrease from 450 K in the selenide (x = 0) to 330 K in the sulfide (x = 1). Finally, we demonstrate a direct linear relationship between T(N) and the Fe-(Se, S) bond length (or Fe-(Se, S) height).

Disorder effects in pnictides: a tunneling spectroscopy study

We present the synthesis and the tunneling spectroscopy study of superconducting FeSe(0.5)Te(0.5) (T(c) = 14 K), SmFeAsO(0.85) (T(c) = 54 K) and SmFeAsO(0.9)F(0.1) (T(c) = 45 K). The samples were characterized by Rietveld refinement of x-ray diffraction patterns and transport as well as temperature-dependent magnetic measurements. Tunneling experiments on FeSe(0.5)Te(0.5) revealed a single superconducting gap ∼ 1 meV in BCS-like tunneling conductance spectra. In SmFeAsO(0.85) and SmFeAsO(0.9)F(0.1), however, more complex spectra were observed, characterized by two gap-like structures at ∼ 4 and ∼ 10 meV. These spectra are qualitatively understood assuming a two-band superconductor with a 's ±' order parameter. We show that, depending on the sign relation between the pairing amplitudes in the two bands, the interband quasiparticle scattering has a crucial effect on the shape of the tunneling spectra. On the other hand, single-gap spectra found in FeSe(0.5)Te(0.5) are more compatible with a disorder-induced 's '-wave gap, due to the Se-Te substitution.

Territorial organization of the lowland classic maya

Thus far I have discussed ancient Maya sociopolitical structure from the upper levels of the hierarchy downward. Let me now summarize their territorial organization from the bottom upward, starting at the hamlet level (Fig. 8). The smallest unit of settlement-one usually overlooked by archeological surveys in the lowland rain forest-was probably a cluster of thatched huts occupied by a group of related families; larger clusters may have been divided into four quadrants along the lines suggested by Coe (26). Because of the long fallow period (6 to 8 years) characteristic of slash-and-burn agriculture in the Petén, these small hamlets are presumed to have changed location over the years, although they probably shifted in a somewhat circular fashion around a tertiary ceremonial-civic center for whose maintenance they were partly responsible. These tertiary centers were spaced at fairly regular intervals around secondary ceremonial-civic centers with pyramids, carved monuments, and palace-like residences. In turn, the secondary centers occurred at such regular intervals as to form hexagonal patterns around primary centers, which were still larger, with acropolises, multiple ceremonial plazas, and greater numbers of monuments. In some cases, the distance between secondary centers was roughly twice the distance between secondary and tertiary centers, creating a lattice of nested hexagonal cells. This pattern, which conforms to a Western theoretical construct, was presumably caused by factors of service function, travel, and transport. The pattern was not recognized by the Maya at all. They simply recognized that a whole series of smaller centers were dependent on a primary center and therefore mentioned its emblem glyph. Linking the centers of the various hexagons were marriage alliances between members of royal dynasties, who had no kinship ties with the farmers in the hamlets. Out of the large number of primary centers available to them, the Maya selected four as regional capitals. True to their cosmology, the Maya regarded these capitals as associated with the four quadrants of their realm, regardless of their actual location. Each was the home city for a very important dynasty whose junior members probably ruled secondary centers. Since the hexagonal lattices were probably adjusted to variations in population density, each of the four quadrants of the Maya realm probably controlled a comparable number of persons. So strong was the cognized model that, despite the rise and fall of individual centers, there seem always to have been four capitals, each associated with a direction and, presumably, with a color. There is still a great deal to learn about the social, political, and territorial organization of the lowland Maya, and parts of the picture presented here need far more data for their confirmation. What seems likely is that the Maya had an overall quadripartite organization (rather than a core and buffer zone) and that within each quadrant there was at least a five-tiered administrative hierarchy of capital, secondary center, tertiary center, village, and hamlet. Perhaps most significant, there was no real conflict between the lattice-like network predicted by locational analysis and the cosmological four-part structure predicted by epigraphy and ethnology.

Ultrasonic properties near 50 K of the quasi-one-dimensional conductors A(0.30)MoO(3) (A = K, Rb) and Rb(0.30)(Mo(1-x)V(x))O(3)

The charge density wave (CDW) nonlinear conductivity of the blue bronzes A(0.30)MoO(3) (A = K, Rb) shows two different regimes depending on the temperature: a strongly damped CDW motion above ∼50 K and a CDW motion with almost no damping below ∼50 K. In a search for an elastic signature of this CDW behaviour, we performed ultrasonic measurements on A(0.30)MoO(3) single crystals in the temperature range 4-300 K. In Rb(0.30)MoO(3), at T∼50 K, upon cooling, a large increase of the sound velocity for the longitudinal mode measured along the [Formula: see text], [102] and b directions is observed. The ultrasonic attenuation coefficient shows an increase down to 50 K followed by a plateau. Similar results are found in K(0.30)MoO(3). In V-doped samples, Rb(0.30)(Mo(1-x)V(x))O(3) (x = 0.4%) the anomaly broadens and is shifted towards higher temperatures. The results are discussed in relation to the changes in the CDW rigidity, disorder and dielectric response. A scenario based on a glass transition for the CDW superstructure is proposed.

Observation of correlations up to the micrometer scale in sliding charge-density waves

A high resolution coherent x-ray diffraction experiment has been performed on the charge-density wave (CDW) system K0.3MoO3. The 2kF satellite reflection associated with the CDW has been measured with respect to external dc currents. In the sliding regime, the 2kF satellite reflection displays secondary satellites along the chain axis which corresponds to correlations up to the micrometer scale. This super long-range order is 1500 times larger than the CDW period itself. This new type of electronic correlation seems inherent to the collective dynamics of electrons in charge-density wave systems. Several scenarios are discussed.

Anisotropy of the Sommerfeld coefficient in magnesium diboride single crystals

The anisotropic field dependence of the Sommerfeld coefficient gamma has been measured down to B-->0 by combining specific heat and Hall probe magnetization measurements in MgB2 single crystals. We find that gamma(B,theta) is the sum of two contributions arising from the sigma and pi band, respectively. We show that gammasigma(B,theta)=B/Bc2(theta) where Bc2(theta)=Bc2ab/sqrt[sin2theta+Gamma2cos2theta] with Gamma approximately 5.4 (theta being the angle between the applied field and the c axis) and gammapi(B,theta)=gammapi(B)=B/Bpi(B). The "critical field" of the pi band Bpi is fully isotropic but field dependent increasing from approximately 0.25 T for B< or =0.1 T up to 3 T approximately Bc2c for B-->3 T. Because of the coupling of the two bands, superconductivity survives in the pi band up to 3 T but is totally destroyed above for any orientation of the field.

Sulfatide is essential for the maintenance of CNS myelin and axon structure

Galactocerebroside (GalC) and sulfatide are abundant myelin lipids. In mice incapable of synthesizing these lipids, myelin is thin and regionally unstable and exhibits several subtle structural abnormalities. Although galactolipid-null mice have been beneficial in the analysis of galactolipid function, it has not been possible to differentiate between the functions of GalC and sulfatide with these mice alone. In the present work, we have analyzed a murine model that forms normal levels of GalC but is incapable of synthesizing sulfatide. By comparing a plethora of morphological features between the galactolipid-null and the sulfatide-null mice, we have begun to differentiate between the specific functions of these closely related lipids. The most striking difference between these two mutants is the reduction of myelin developmental abnormalities (e.g., redundant and uncompacted myelin sheaths) in young adult sulfatide-null mice as compared with the galactolipid-null animals. Although sulfatide appears to play a limited role in myelin development, this lipid is essential for myelin maintenance, as the prevalence of redundant, uncompacted, and degenerating myelin sheaths as well as deteriorating nodal/paranodal structure is increased significantly in aged sulfatide-null mice as compared with littermate wildtype mice. Finally, we show that the role played by sulfatide in CNS maintenance is not limited to the myelin sheath, as axonal caliber and circularity are normal in young adult mutant mice but are significantly altered in aged sulfatide-null animals.

Charge density wave dislocation as revealed by coherent x-ray diffraction

Coherent x-ray diffraction experiments have been performed on high quality crystals of the charge density wave (CDW) system K0.3MoO3. The satellite reflections associated with the CDW have been measured as a function of the 20-microm-diameter beam position. For some positions, regular fringes have been observed. We show that this observation is consistent with the presence of a single CDW dislocation. Beyond charge density wave systems, this experiment shows that coherent x-ray diffraction is a suitable tool to probe topological defects embedded in the bulk.

Dependence of the superconducting transition temperature on the doping level in single-crystalline diamond films

Homoepitaxial diamond layers doped with boron in the 10(20)-10(21) cm(-3) range are shown to be type II superconductors with sharp transitions (approximately 0.2 K) at temperatures increasing from 0 to 2.1 K with boron contents. The critical concentration for the onset of superconductivity in those 001-oriented single-crystalline films is about 5-7 10(20) cm(-3). The H-T phase diagram has been obtained from transport and ac-susceptibility measurements down to 300 mK.

Anisotropies of the lower and upper critical fields in MgB2 single crystals

The temperature dependence of the upper (H(c2)) and lower (H(c1)) critical fields has been deduced from Hall probe magnetization measurements of high quality MgB2 single crystals along the two main crystallographic directions. We show that Gamma(H(c2))=H(c2 axially ab)/H(c2 axially c) and Gamma(H(c1))=H(c1 axially c)/H(c1 axially ab) differ significantly at low temperature (being approximately 5 and approximately 1, respectively) and have opposite temperature dependencies. We suggest that MgB2 can be described by a single field dependent anisotropy parameter gamma(H) (=lambda(c)/lambda(ab)=xi(ab)/xi(c)) that increases from Gamma(H(c1)) at low field to Gamma(H(c2)) at high field.

Direct transition from Bose glass to normal state in the (K,Ba)BiO3 superconductor

The introduction of columnar defects in (K,Ba )Bi O3 single crystals shifts both the irreversibility and thermodynamic transition lines, respectively, deduced from ac susceptibility (and/or transport) and specific heat measurements, upwards. This shift can be attributed to the defect-induced decrease of the difference (Delta F) between the free energies in the superconducting and the normal states, assuming that the position of the superconducting transition is given by the condition absolute value Delta F approximately k(B )T/xi(3 ). This criterion also perfectly reproduces the influence of the angle between the tracks and the external field. This result suggests that no vortex liquid phase exists in this system.

Superconductivity in doped sp3 semiconductors: the case of the clathrates

We present a joint experimental and theoretical study of the superconductivity in doped silicon clathrates. The critical temperature in Ba(8)@Si-46 is shown to strongly decrease with applied pressure. These results are corroborated by ab initio calculations using MacMillan's formulation of the BCS theory with the electron-phonon coupling constant lambda calculated from perturbative density functional theory. Further, the study of I(8)@Si-46 and of gedanken pure silicon diamond and clathrate phases doped within a rigid-band approach show that the superconductivity is an intrinsic property of the sp(3) silicon network. As a consequence, carbon clathrates are predicted to yield large critical temperatures with an effective electron-phonon interaction much larger than in C60.

Anisotropic enhancement of superconductivity in heavy-ion irradiated (K, Ba)BiO3

We have measured the specific heat, resistivity, and ac susceptibility of (K,Ba)BiO3 single crystals before and after introduction of either point or columnar defects by electron (EI) or heavy-ion irradiation (HII). While the magnetic field dependence of these properties remains mainly unaffected by EI, the irreversibility line and the location of the specific heat anomaly are both shifted up in temperature after HII. The shift is apparent only if the magnetic field is applied parallel to the ion tracks. For perpendicularly applied fields, both lines lie at the same field as in the pristine sample. These experiments call the nature of the vortex liquid state into question.

Anomalous magnetic field dependence of the thermodynamic transition line in the isotropic superconductor (K,Ba)BiO3

Thermodynamic (specific heat, reversible magnetization, tunneling spectroscopy) and transport measurements have been performed on high quality (K,Ba)BiO3 single crystals. The temperature dependence of the magnetic field H(C(p)) corresponding to the onset of the specific heat anomaly presents a clear positive curvature. H(C(p)) is significantly smaller than the field H(Delta) for which the superconducting gap vanishes but is closely related to the irreversibility line deduced from transport data. Moreover, the temperature dependence of the reversible magnetization presents a strong deviation from the Ginzburg-Landau theory emphasizing the peculiar nature of the superconducting transition in this material.

Two-gap state density in MgB(2): a true bulk property or a proximity effect?

We report on the temperature dependence of the quasiparticle density of states in the simple binary compound MgB(2) directly measured using scanning tunneling microscope (STM). To achieve high quality tunneling conditions, a small crystal of MgB(2) is used as a tip in the STM experiment. The "sample" is chosen to be a 2H- NbSe(2) single crystal presenting an atomically flat surface. At low temperature the tunneling conductance spectra show a gap at the Fermi energy followed by two well-pronounced conductance peaks on each side. They appear at voltages V(S) approximately +/-3.8 mV and V(L) approximately +/-7.8 mV. With rising temperature both peaks disappear at the T(C) of the bulk MgB(2), a behavior consistent with the model of two-gap superconductivity. The possibility of a particular proximity effect is also discussed.

Evidence for diverging barriers in the disordered vortex solid in the (K,Ba)BiO(3) superconducting oxide

Vortex dynamics has been investigated in the cubic (K,Ba)BiO (3) superconductor using ac susceptibility measurements on a large frequency range (0.03 Hz<omega<60 kHz). Power law diverging barriers have been obtained on both sides of the order-disorder transition line. The mu exponent remains close to 5/2 (elastic creep value) in some part of the disordered phase and finally decreases at high temperature and/or high field, in good agreement with the recent plastic collective creep theory [J. Kierfeld, H. Nordborg, and V. M. Vinokur, Phys. Rev. Lett., 85, 4948 (2000)].

A Bragg glass phase in the vortex lattice of a type II superconductor

Although crystals are usually quite stable, they are sensitive to a disordered environment: even an infinitesimal amount of impurities can lead to the destruction of crystalline order. The resulting state of matter has been a long-standing puzzle. Until recently it was believed to be an amorphous state in which the crystal would break into 'crystallites'. But a different theory predicts the existence of a novel phase of matter: the so-called Bragg glass, which is a glass and yet nearly as ordered as a perfect crystal. The 'lattice' of vortices that contain magnetic flux in type II superconductors provide a good system to investigate these ideas. Here we show that neutron-diffraction data of the vortex lattice provides unambiguous evidence for a weak, power-law decay of the crystalline order characteristic of a Bragg glass. The theory also predicts accurately the electrical transport properties of superconductors; it naturally explains the observed phase transitions and the dramatic jumps in the critical current associated with the melting of the Bragg glass. Moreover, the model explains experiments as diverse as X-ray scattering in disordered liquid crystals and the conductivity of electronic crystals.

Evidence for two superconducting energy gaps in MgB(2) by point-contact spectroscopy

Experimental support is found for the multiband model of the superconductivity in the recently discovered system MgB(2) with the transition temperature T(c) = 39 K. By means of Andreev reflection, evidence is obtained for two distinct superconducting energy gaps. The sizes of the two gaps ( Delta(S) = 2.8 meV and Delta(L) = 7 meV) are, respectively, smaller and larger than the expected weak coupling value. Because of the temperature smearing of the spectra the two gaps are hardly distinguishable at elevated temperatures, but when a magnetic field is applied the presence of two gaps can be demonstrated close to the bulk T(c) in the raw data.

Social adjustment of adolescents at risk for schizophrenia: the Jerusalem Infant Development Study

OBJECTIVE

To better understand whether poor social adjustment, a core characteristic of schizophrenic illness, may also be an indicator of vulnerability in young people who are at genetic risk for schizophrenia, but who do not have schizophrenia.

METHOD

Between 1992 and 1996, 27 Israeli adolescents with a schizophrenic parent, 29 adolescents with no mentally ill parent, and 30 adolescents with a parent having a nonschizophrenic mental disorder were assessed on multiple domains of social adjustment measured using the Social Adjustment Inventory for Children and Adolescents and the Youth Self-Report.

RESULTS

Young people with a schizophrenic parent showed poor peer engagement, particularly heterosexual engagement, and social problems characterized by immaturity and unpopularity with peers. These social adjustment difficulties in youths at risk for schizophrenia could not be attributed solely to the presence of early-onset mental disorders, although problems were greater in those with disorders in the schizophrenia spectrum. Young people whose parents had other disorders showed different patterns of social maladjustment characterized by difficult, conflictual relationships with peers and family.

CONCLUSION

Adolescents at risk for schizophrenia have social deficits that extend beyond early-onset psychopathology and that may reflect vulnerability to schizophrenic disorder.

Effects of galactolipid elimination on oligodendrocyte development and myelination

The galactolipids galactocerebroside and sulfatide, which require the enzyme UDP-galactose:ceramide galactosyltransferase (CGT) for their synthesis, are among the most prevalent molecules in the myelin sheath. Numerous studies, mainly using antibody perturbation methods in vitro, have suggested that these molecules are crucial mediators of oligodendrocyte differentiation and myelin formation. Although we have previously demonstrated that myelin formation occurs in CGT null mutant mice, which are incapable of synthesizing the myelin galactolipids, here we show that there are developmental alterations in the CNS of these animals. There is a significant decrease in the number of myelinated axon segments in the mutant spinal cord despite normal levels of myelin gene-specific mRNAs and proteins. Also, there is an increased cellularity in the mature mutant spinal cord and the distinctive morphology of the additional cells suggests that they are actively myelinating oligodendrocytes. Using in situ hybridization techniques, we show that there is a 50% increase in the number of oligodendrocytes in the mutant spinal cord. The data suggest that galactolipids play an important developmental role in regulating the maturation program and final number of oligodendrocytes.

Neurobehavioral deficits at adolescence in children at risk for schizophrenia: The Jerusalem Infant Development Study

BACKGROUND

The Jerusalem Infant Development Study is a prospective investigation comparing offspring of schizophrenic parents with offspring of parents who have no mental disorder or have nonschizophrenic mental disorders. During infancy and school age, a subgroup of offspring of schizophrenic parents showed global neurobehavioral deficits that were hypothesized to be indicators of vulnerability to schizophrenia. The purposes of the present investigation were to determine if neurobehavioral deficits were present in the offspring of schizophrenics at adolescence, to examine their stability over time, and to explore their relation to concurrent mental adjustment.

METHODS

Sixty-five Israeli adolescents were assessed on a battery of neurologic and neuropsychological assessments. They were also administered psychiatric interviews from which best-estimate DSM-III-R diagnoses and scores of global adjustment were derived.

RESULTS

Adolescents with poor neurobehavioral functioning were identified from composites of motor and cognitive-attentional variables. A disproportionate number of offspring of schizophrenic parents (42%; 10/24), and especially male offspring of schizophrenic parents (73%; 8/11), showed poor neurobehavioral functioning relative to offspring of nonschizophrenic parents (22%; 9/41). Adolescent offspring of schizophrenics with poor neurobehavioral functioning had been poorly functioning at earlier ages and had poor psychiatric adjustment at adolescence. All 4 offspring of schizophrenics receiving schizophrenia spectrum diagnoses by adolescence showed a pattern of poor neurobehavioral functioning across developmental periods.

CONCLUSIONS

Results are consistent with the hypothesis that individuals at genetic risk for schizophrenia may display lifelong neurobehavioral signs that are indicators of vulnerability to schizophrenia and that are associated with psychiatric adjustment generally and schizophrenic spectrum disorder specifically.