Low vitamin C and increased oxidative stress and cell death in mice that lack the sodium-dependent vitamin C transporter SVCT2

The sodium-dependent vitamin C transporter (SVCT2) is responsible for the transport of vitamin C into cells in multiple organs, from either the blood or the cerebrospinal fluid. Mice null for SVCT2 (SVCT2(-/-)) do not survive past birth but the cause of death has not yet been ascertained. After mating of SVCT2(+/-) males and SVCT2(+/-) females, fewer SVCT2(-/-) and SVCT2(+/-) progeny were observed than would be expected according to Mendelian ratios. Vitamin C levels in SVCT2(-/-), SVCT2(+/-), and SVCT2(+/+) were genotype-dependent. SVCT2(-/-) fetuses had significantly lower vitamin C levels than littermates in placenta, cortex, and lung, but not in liver (the site of vitamin C synthesis). Low vitamin C levels in placenta and cortex were associated with elevations in several markers of oxidative stress: malondialdehyde, isoketals, F(2)-isoprostanes, and F(4)-neuroprostanes. Oxidative stress was not elevated in fetal SVCT2(-/-) lung tissue despite low vitamin C levels. In addition to the expected severe hemorrhage in cortex, we also found hemorrhage in the brain stem, which was accompanied by cell loss. We found evidence of increased apoptosis in SVCT2(-/-) mice and disruption of the basement membrane in fetal brain. Together these data show that SVCT2 is critical for maintaining vitamin C levels in fetal and placental tissues and that the lack of SVCT2, and the resulting low vitamin C levels, results in fetal death and, in SVCT2(-/-) mice that survive the gestation period, in oxidative stress and cell death.

Epitaxial graphene on SiC(0001): more than just honeycombs

Using scanning tunneling microscopy with Fe-coated W tips and first-principles calculations, we show that the interface of epitaxial graphene/SiC(0001) is a warped graphene layer with hexagon-pentagon-heptagon (H(5,6,7)) defects that break the honeycomb symmetry, thereby inducing a gap and states below E(F near the K point. Although the next graphene layer assumes the perfect honeycomb lattice, its interaction with the warped layer modifies )the dispersion about the Dirac point. These results explain recent angle-resolved photoemission and carbon core-level shift data and solve the long-standing problem of the interfacial structure of epitaxial graphene on SiC(0001).

Evidence for an anomalous like-sign dimuon charge asymmetry

We measure the charge asymmetry A ≡ (N++ - N--)/(N++ + N--) of like-sign dimuon events in 6.1 fb-1 of pp collisions recorded with the D0 detector at a center-of-mass energy square root(s) = 1.96   TeV at the Fermilab Tevatron collider. From A we extract the like-sign dimuon charge asymmetry in semileptonic b-hadron decays: A(sl)(b) = -0.009 57 ± 0.002 51(stat) ± 0.001 46(sys). It differs by 3.2 standard deviations from the standard model prediction A(sl)(b)(SM) = (-2.3(-0.6)(+0.5)) × 10(-4), and provides first evidence of anomalous CP violation in the mixing of neutral B mesons.

The clinical significance of occult hepatitis B transfusion in Taiwan--a look-back study

OBJECTIVES

A look-back study was conducted to determine the clinical significance of occult hepatitis B virus (HBV) blood transfusion in an HBV hyperendemic area.

AIM

To improve the blood transfusion safety.

BACKGROUND

Occult HBV is transmissible through blood transfusion in HBV-naÏve recipients. However, its impact on recipients with prevalent HBV infection in HBV hyperendemic areas is unclear.

METHODS/MATERIALS

In 2006, 12 occult HBV blood donors were found from 10 824 repository samples by nucleic acid testing. The 74 corresponding recipients were identified and their pre- and post-transfusion clinical information was gathered, and the living recipients were recalled for follow-up. From the available archival sera, the HBV DNA was examined and sub-genomic sequences between paired donor and recipient were compared using polymerase chain reaction-based assays.

RESULTS

Among the 74 recipients, 18 were still alive and 12 returned to our clinic. From the available serological profiles, 76% of recipients had ongoing or recovered HBV infection before transfusion. Only 24 recipients had available post-transfusion serological profiles and none seroconverted to be hepatitis B surface antigen (HBsAg) positive. Moreover, except for the prior HBsAg carriers, the recipients' HBV DNA levels after transfusion were low (<20 IU/mL). One recipient had identical HBV surface gene sub-genomic sequence (384 nucleotides) to his donor. After transfusion, no recipient developed post-transfusion hepatitis (PTH) and the clinical outcome was good.

CONCLUSION

In HBV hyperendemic areas, occult hepatitis B transfusion might not lead to HBsAg carriage or PTH. The risk of transfusion-transmitted HBV infection was probably lower than that in non-endemic areas because most recipients had already experienced HBV infection.

Aeolian sediment evidence that global cooling has driven late Cenozoic stepwise aridification in central Asia

It has been a long held view that uplift of the Tibetan Plateau dominated stepwise climatic drying in central Asia during the late Cenozoic. On the other hand, global cooling may also have forced Asian drying and the subsequent formation of aeolian deposits in north China. Until now, whether the Tibetan uplift or the global cooling has been the first-order driver controlling stepwise Asian drying has remained a contentious issue. In this study, we examine the thick aeolian silt deposit, which is regarded as a good archive of palaeoclimatic changes in central Asia and north China, in order to qualitatively reconstruct the drying process in Asia during the late Cenozoic. On the basis of our long-term field surveys, laboratory analyses and previous investigations, we have obtained time sequences of Asian drying from the early Miocene to late Pleistocene; we compare this newly reconstructed time series of Asian aridification with the time series of global cooling and Tibetan uplift to identify the first-order driver of stepwise Asian aridification. A good match between the drying and global cooling might indicate that global cooling was the most likely driver of stepwise drying in interior Asia. On the other hand, controversy regarding timing and amplitude of Tibetan uplift during the late Cenozoic suggests that the prevailing conclusion that Tibetan uplift forces Asian drying should be regarded as immature. A mechanism that global cooling drove the Asian drying is tentatively suggested.

Molecular hydrogen desorption from amorphous surfaces at low temperature

We studied the desorption of hydrogen molecules from amorphous silicates of composition (Fe(x)Mg(1 - x))(2)SiO(4) (0 < x < 1) using thermal programmed desorption (TPD). Selected measurements of formation of molecular hydrogen on and desorption from a single crystal olivine sample were done for comparison. The experiments were conducted in conditions as close as technically possible to those found in selected interstellar medium environments, where the formation of molecular hydrogen takes place on dust grains. From molecular desorption data, we derive the energy distribution of binding sites using a direct inversion method. The application of this type of data to the study of elementary processes of migration of atoms and molecules on and ejection from disordered surfaces at low temperature is discussed.

Peripheral adenosine A2A receptors are involved in carrageenan-induced mechanical hyperalgesia in mice

Here we studied the role of peripheral adenosine A(2A) receptors in mechanical hyperalgesia during inflammation using mice lacking the A(2A) receptors. Unilateral s.c. administration of the local inflammatory agent λ-carrageenan induced profound mechanical hyperalgesia 24 h after administration in the ipsilateral hind paw in wild-type mice. In homozygous mice lacking the A(2A) receptors, carrageenan-induced hyperalgesia was significantly reduced compared to wild type controls. The reduction in inflammatory hyperalgesia seen in A(2A) receptor knock-out mice was not associated with changes in paw edema. CGS 21680, a selective A(2A) receptor agonist, produced significantly more mechanical hyperalgesia in wild type females than in wild type males upon direct s.c. injection into the hindpaw whereas it had no effect upon systemic administration. The hyperalgesic effect of CGS 21680 was markedly reduced in the A(2A) knock-out mice of both sexes. Subcutaneous ZM-241,385, a selective A(2A) receptor antagonist, injected into the hindpaw reduced the mechanical hyperalgesia following carrageenan in female mice, but not in males. The results indicate that activation of peripheral adenosine A(2A) receptors during inflammation is associated with mechanical hyperalgesia, and that this effect is more prominent in females than in males.

In vitro cytotoxicity and hemocompatibility studies of Ti-Nb, Ti-Nb-Zr and Ti-Nb-Hf biomedical shape memory alloys

The in vitro cytotoxicity and hemocompatibility of the Ti-Nb, Ti-Nb-Zr and Ti-Nb-Hf biomedical shape memory alloys (SMAs) were investigated by cell culture (L-929 fibroblast cell), hemolytic test and platelet adhesion test, with CP Ti as a reference material. The cytotoxicity test indicates that all the Ti-Nb, Ti-Nb-Zr and Ti-Nb-Hf SMAs show over 94% cell viability for different incubation times (2, 4 and 7 days) in comparison with a negative control and CP Ti. The cell morphology observation shows good polygon-like adherent growth and proliferation of L-929 in the extracts of all the test samples and CP Ti. These results suggest excellent cytocompatibility for the Ti-Nb, Ti-Nb-Zr and Ti-Nb-Hf SMAs. The hemolytic test reveals that the hemolysis ratios of the Ti-Nb, Ti-Nb-Zr and Ti-Nb-Hf alloys are far less than 5%, so they cannot give rise to acute hemolysis. The platelet morphology observation shows almost the same adhered platelet morphology and activation ratio for the test samples in comparison with CP Ti, except the Ti-22Nb-6Hf alloy, which shows a lower activation ratio of platelets, indicating excellent blood compatibility. Therefore, it is proposed that the Ti-Nb, Ti-Nb-Zr and Ti-Nb-Hf SMAs will be candidates to replace Ti-Ni for biomedical applications.

Intracerebroventricular delivery of glucocerebrosidase reduces substrates and increases lifespan in a mouse model of neuronopathic Gaucher disease

Gaucher disease is caused by a deficit in the enzyme glucocerebrosidase. As a consequence, degradation of the glycolipids glucosylceramide (GluCer) and glucosylsphingosine (GluSph) is impaired, and their subsequent buildup can lead to significant pathology and early death. Type 1 Gaucher patients can be treated successfully with intravenous replacement enzyme, but this enzyme does not reach the CNS and thus does not ameliorate the neurological involvement in types 2 and 3 Gaucher disease. As one potential approach to treating these latter patients, we have evaluated intracerebroventricular (ICV) administration of recombinant human glucocerebrosidase (rhGC) in a mouse model of neuronopathic Gaucher disease. ICV administration resulted in enzyme distribution throughout the brain and alleviated neuropathology in multiple brain regions of this mouse model. Treatment also resulted in dose-dependent decreases in GluCer and GluSph and significantly extended survival. To evaluate the potential of continuous enzyme delivery, a group of animals was treated ICV with an adeno-associated viral vector encoding hGC and resulted in a further extension of survival. These data suggest that ICV administration of rhGC may represent a potential therapeutic approach for type 2/3 Gaucher patients. Preclinical evaluation in larger animals will be needed to ascertain the translatability of this approach to the clinic.

A mathematical model of the murine ventricular myocyte: a data-driven biophysically based approach applied to mice overexpressing the canine NCX isoform

Mathematical modeling of Ca(2+) dynamics in the heart has the potential to provide an integrated understanding of Ca(2+)-handling mechanisms. However, many previous published models used heterogeneous experimental data sources from a variety of animals and temperatures to characterize model parameters and motivate model equations. This methodology limits the direct comparison of these models with any particular experimental data set. To directly address this issue, in this study, we present a biophysically based model of Ca(2+) dynamics directly fitted to experimental data collected in left ventricular myocytes isolated from the C57BL/6 mouse, the most commonly used genetic background for genetically modified mice in studies of heart diseases. This Ca(2+) dynamics model was then integrated into an existing mouse cardiac electrophysiology model, which was reparameterized using experimental data recorded at consistent and physiological temperatures. The model was validated against the experimentally observed frequency response of Ca(2+) dynamics, action potential shape, dependence of action potential duration on cycle length, and electrical restitution. Using this framework, the implications of cardiac Na(+)/Ca(2+) exchanger (NCX) overexpression in transgenic mice were investigated. These simulations showed that heterozygous overexpression of the canine cardiac NCX increases intracellular Ca(2+) concentration transient magnitude and sarcoplasmic reticulum Ca(2+) loading, in agreement with experimental observations, whereas acute overexpression of the murine cardiac NCX results in a significant loss of Ca(2+) from the cell and, hence, depressed sarcoplasmic reticulum Ca(2+) load and intracellular Ca(2+) concentration transient magnitude. From this analysis, we conclude that these differences are primarily due to the presence of allosteric regulation in the canine cardiac NCX, which has not been observed experimentally in the wild-type mouse heart.