pH-dependent water permeability switching and its memory in MoS2 membranes.

Intelligent transport of molecular species across different barriers is critical for various biological functions and is achieved through the unique properties of biological membranes1-4. Two essential features of intelligent transport are the ability to (1) adapt to different external and internal conditions and (2) memorize the previous state5. In biological systems, the most common form of such intelligence is expressed as hysteresis6. Despite numerous advances made over previous decades on smart membranes, it remains a challenge to create a synthetic membrane with stable hysteretic behaviour for molecular transport7-11. Here we demonstrate the memory effects and stimuli-regulated transport of molecules through an intelligent, phase-changing MoS2 membrane in response to external pH. We show that water and ion permeation through 1T' MoS2 membranes follows a pH-dependent hysteresis with a permeation rate that switches by a few orders of magnitude. We establish that this phenomenon is unique to the 1T' phase of MoS2, due to the presence of surface charge and exchangeable ions on the surface. We further demonstrate the potential application of this phenomenon in autonomous wound infection monitoring and pH-dependent nanofiltration. Our work deepens understanding of the mechanism of water transport at the nanoscale and opens an avenue for the development of intelligent membranes.

Early initiation of direct anticoagulation after stroke in patients with atrial fibrillation.

BACKGROUND AND PURPOSE: The safety of early initiation of anticoagulant therapy in patients with ischaemic stroke related to atrial fibrillation (AF) is unknown. We investigated the safety of early initiation of direct oral anticoagulants (DOACs), vitamin K antagonists (VKAs) or no anticoagulation. METHODS: This observational, retrospective, single-centre study included consecutive patients with recent (<4 weeks) ischaemic stroke and AF. The primary outcome was the rate of major (intracranial and extracranial) bleeding in patients on different treatment schemes, i.e. DOACs, VKAs and not anticoagulated. We also investigated the rate of ischaemic cerebrovascular events and mortality. RESULTS: We included 959 consecutive patients with AF and ischaemic stroke followed up for an average of 16.1 days after the index event. A total of 559 out of 959 patients (58.3%) were anticoagulated with either VKAs (n = 259) or DOACs (n = 300). Anticoagulation was started after a mean of 7 ± 9.4 days in the DOAC group and 11.9 ± 19.7 days in the VKA group. Early initiation of any anticoagulant was not associated with an increased risk of any major bleeding [odds ratio (OR), 0.49; 95% confidence intervals (CI), 0.21-1.16] and in particular of intracranial bleeding (OR, 0.47; 95% CI, 0.17-1.29; P = 0.143) compared with no anticoagulation. In contrast to VKAs (OR, 0.78; 95% CI, 0.28-2.13), treatment with DOACs (OR, 0.32; 95% CI, 0.10-0.96) reduced the rate of major bleeding compared with no anticoagulation. Early recurrences of ischaemic stroke did not differ significantly among the three groups. CONCLUSIONS: Starting DOACs within a mean of 7 days after stroke appeared to be safe. Randomized controlled studies are needed to establish the added efficacy of starting anticoagulation early after stroke.

Responses of the mammary transcriptome of dairy cows to altered photoperiod during late gestation.

Cows exposed to short day photoperiod (SD, 8L:16D) during the 60-day nonlactating period prior to parturition produce more milk in their subsequent lactation compared with cows exposed to long day photoperiod (LD, 16L:8D). Although this response is well established in dairy cows, the underlying mechanisms are not understood. We hypothesized that differential gene expression in cows exposed to SD or LD photoperiods during the dry period could be used to identify the functional basis for the subsequent increase in milk production during lactation. Pregnant, multiparous cows were maintained on an SD or LD photoperiod for 60 days prior to parturition. Mammary biopsies were obtained on days -24 and -9 relative to parturition and Affymetrix GeneChip Bovine Genome Arrays were used to quantify gene expression. Sixty-four genes were differentially expressed (P ≤ 0.05 and fold-change ≥ |1.5|) between SD and LD treatments. Many of these genes were associated with cell growth and proliferation, or immune function. Ingenuity Pathway Analysis predicted upstream regulators to include TNF, TGF-ß1, interferon-γ, and several interleukins. In addition, expression of 125 genes was significantly different between day -24 and day -9; those genes were associated with milk component metabolism and immune function. The interaction of photoperiod and time affected 32 genes associated with insulin-like growth factor I signaling. Genes differentially expressed in response to photoperiod were associated with mammary development and immune function consistent with the enhancement of milk yield in the ensuing lactation. Our results provide insight into the mechanisms by which photoperiod affects the mammary gland and subsequently lactation.

Lesion locations influencing baseline severity and early recovery in ischaemic stroke.

BACKGROUND AND PURPOSE: Strokes caused by lesions to certain brain areas are associated with poor outcome, which is important both prognostically and to understand the neural basis for recovery. However, lesion anatomy associations with outcome may occur because of effects on baseline severity rather than because of effects on recovery per se. Here, all common stroke locations were surveyed to determine the strongest lesion anatomy associations separately for baseline functional severity and proportional recovery. Since most recovery occurs early, the focus here is on functional changes over the first week. METHOD: Global functional scores (National Institutes of Health Stroke Scale) at baseline and proportional recovery over 1 week were derived from the records of 550 ischaemic stroke patients and related to magnetic resonance imaging lesion location using voxel-lesion mapping. The effects of lesions extending over more than one location were also considered. Cross-validation estimated the percentage of recovery rate variance (r(2) ) accountable by lesion location information. RESULTS: High baseline severity was associated with lesions to the left capsule, striatum and thalamocortical white matter, whereas high recovery rate was associated with lesions to more superficial left fronto-temporal areas. Low recovery rates were associated with lesions to bilateral parietal, right insula, medial frontal, capsule and brainstem. Inclusion of these regions into a multivariate model of proportional recovery rate increased r(2) from 8% to 45%. CONCLUSION: The strongest stroke lesion location associations with 1-week recovery were identified, and it was shown that anatomical information accounts for a sizeable proportion of early recovery variability.

Intravenous immunoglobulin increases plasma viscosity without parallel rise in blood pressure.

WHAT IS KNOWN AND OBJECTIVE: Intravenous immunoglobulin (IVIg) is a commonly used therapy for autoimmune disease, but may cause chronic hypertension and thrombosis. We determined whether: (i) IVIg systematically affects blood pressure in the short term; (ii) acute changes in plasma viscosity because of IVIg correlate with blood pressure effects; (iii) effects of IVIg on acute blood pressure are related to baseline blood pressure or hypertension status and (iv) IVIg influences plasma markers of inflammation, anticardiolipin antibodies and homocysteine as additional putative prothrombotic risk factors. METHODS: Twenty adults with autoimmune neurological disease who received a course of IVIg were evaluated immediately before and after each infusion, on every day of the course. Blood pressure, pulse and the following haematological parameters were determined: plasma viscosity, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), haematocrit, fibrinogen, interleukin-6 (IL-6), homocysteine and anticardiolipin positivity. RESULTS: Intravenous immunoglobulin caused both acute and cumulative rises in plasma viscosity across a treatment course, but no concordant changes in blood pressure. There was also no correlation between individual blood pressure changes and viscosity, baseline blood pressure or hypertension status. Levels of IL-6 rose across the course of therapy, but the acute-phase reactants CRP and fibrinogen did not. One patient developed anticardiolipin antibodies during therapy. WHAT IS NEW AND CONCLUSION: Individual courses of IVIg do not systematically raise blood pressure. Where IVIg is found to cause hypertension, this does not appear to be due to a direct effect of IVIg on plasma viscosity.

Characterization of bovine glucose transporter 1 kinetics and substrate specificities in Xenopus oocytes.

Glucose is an essential substrate for lactose synthesis and an important energy source in milk production. Glucose uptake in the mammary gland, therefore, plays a critical role in milk synthesis. Facilitative glucose transporters (GLUT) mediate glucose uptake in the mammary gland. Glucose transporter 1 (GLUT1) is the major facilitative glucose transporter expressed in the bovine mammary gland and has been shown to localize to the basolateral membrane of mammary epithelial cells. Glucose transporter 1 is, therefore, thought to play a major role in glucose uptake during lactation. The objective of this study was to determine the transport kinetic properties and substrate specificity of bovine GLUT1 using the Xenopus oocyte model. Bovine GLUT1 (bGLUT1) was expressed in Xenopus oocytes by microinjection of in vitro transcribed cRNA and was found to be localized to the plasma membrane, which resulted in increased glucose uptake. This bGLUT1-mediated glucose uptake was dramatically inhibited by specific facilitative glucose transport inhibitors, cytochalasin B, and phloretin. Kinetic analysis of bovine and human GLUT1 was conducted under zero-trans conditions using radio-labeled 2-deoxy-D-glucose and the principles of Michaelis-Menten kinetics. Bovine GLUT1 exhibited a Michaelis constant (K(m)) of 9.8 ± 3.0mM for 2-deoxy-d-glucose, similar to 11.7 ± 3.7 mM for human GLUT1. Transport by bGLUT1 was inhibited by mannose and galactose, but not fructose, indicating that bGLUT1 may also be able to transport mannose and galactose. Our data provides functional insight into the transport properties of bGLUT1 in taking up glucose across mammary epithelial cells for milk synthesis.

Error rates in SARS-CoV-2 testing examined with Bayes' theorem.

The SARS-CoV-2 pandemic has created a demand for large scale testing, as part of the effort to understand and control transmission. It is important to quantify the error rates of test equipment under field conditions, which might differ significantly from those obtained in the laboratory. A literature review on SARS-CoV-2 reverse-transcription polymerase chain reaction (RT-PCR) is used to construct a clinical test confusion matrix. A simple correction method for bulk test results is then demonstrated with examples. The required sensitivity and specificity of a test are explored for societal needs and use cases, before a sequential analysis of common example scenarios is explored. The analysis suggests that many of the people with mild symptoms and positive test results are unlikely to be infected with SARS-CoV-2 in some regions. It is concluded that current and foreseen alternative tests can not be used to "clear" people as being non-infected. Recommendations are given that regional authorities must establish a programme to monitor operational test characteristics before launching large scale testing; and that large scale testing for tracing infection networks in some regions is not viable, but may be possible in a focused way that does not exceed the working capacity of the laboratories staffed by competent experts. RT-PCR tests can not be solely relied upon as the gold standard for SARS-CoV-2 diagnosis at scale, instead clinical assessment supported by a range of expert diagnostic tests should be used.

Modulation of fusiform cortex activity by cholinesterase inhibition predicts effects on subsequent memory.

Cholinergic influences on memory are likely to be expressed at several processing stages, including via well-recognized effects of acetylcholine on stimulus processing during encoding. Since previous studies have shown that cholinesterase inhibition enhances visual extrastriate cortex activity during stimulus encoding, especially under attention-demanding tasks, we tested whether this effect correlates with improved subsequent memory. In a within-subject physostigmine versus placebo design, we measured brain activity with functional magnetic resonance imaging while healthy and mild Alzheimer's disease subjects performed superficial and deep encoding tasks on face (and building) visual stimuli. We explored regions in which physostigmine modulation of face-selective neural responses correlated with physostigmine effects on subsequent recognition performance. In healthy subjects physostigmine led to enhanced later recognition for deep- versus superficially-encoded faces, which correlated across subjects with a physostigmine-induced enhancement of face-selective responses in right fusiform cortex during deep- versus superficial-encoding tasks. In contrast, the Alzheimer's disease group showed neither a depth of processing effect nor restoration of this with physostigmine. Instead, patients showed a task-independent improvement in confident memory with physostigmine, an effect that correlated with enhancements in face-selective (but task-independent) responses in bilateral fusiform cortices. Our results indicate that one mechanism by which cholinesterase inhibitors can improve memory is by enhancing extrastriate cortex stimulus selectivity at encoding, in a manner that for healthy people but not in Alzheimer's disease is dependent upon depth of processing.

Desert Tortoise Gopherus agassizii: Cutaneous Water Loss.

Evaporative water loss from the integument of the desert tortoise Gopherus agassizii constitutes a major proportion of the water loss, but is far less than in tortoises from wetter regions. Respiratory water loss also is less.

Cutaneous water loss in reptiles.

Cutaneous and respiratory evaporation were compared in five species of reptiles at 23 degrees C. There seemed to be a clear correlation between water loss and aridity of the animal's habitat, total evaporation from the desert lizard Sauromalus obesus being about 5 percent of that from the crocodilian Caiman sclerops. Cutaneous evaporation was the major avenue of water loss in all animals examined. This is contrary to the common belief that reptilian skin is practically impermeable to water.

Inactivation of a diol epoxide by dihydrodiol dehydrogenase but not by two epoxide hydrolases.

The mutagenicity of r-8,t-9-dihydroxy-t-10, 11-oxy-8,9,10,11-tetrahydrobenz[a]anthracene (BA-8,9-diol 10, 11-oxide) toward Salmonella typhimurium TA 100 is not decreased by the presence of large amounts of highly purified microsomal or cytosolic epoxide hydrolase. However, highly purified dihydrodiol dehydrogenase inactivates this diol epoxide, which is a major DNA-binding metabolite of benz[a]anthracene. The K-region epoxide, benz[a]anthracene 5,6-oxide (BA 5,6-oxide) is efficiently inactivated by microsomal epoxide hydrolase, is much less readily inactivated by cytosolic epoxide hydrolase, and is not inactivated by dihydrodiol dehydrogenase. This inactivation of a diol epoxide by dihydrodiol dehydrogenase points to a new significance of this enzyme and a new level of control for diol epoxides.

Effects of cholinergic enhancement on visual stimulation, spatial attention, and spatial working memory.

We compared behavioral and neural effects of cholinergic enhancement between spatial attention, spatial working memory (WM), and visual control tasks, using fMRI and the anticholinesterase physostigmine. Physostigmine speeded responses nonselectively but increased accuracy selectively for attention. Physostigmine also decreased activations to visual stimulation across all tasks within primary visual cortex, increased extrastriate occipital cortex activation selectively during maintained attention and WM encoding, and decreased parietal activation selectively during maintained attention. Finally, lateralization of occipital activation as a function of the visual hemifield toward which attention or memory was directed was decreased under physostigmine. In the case of attention, this effect correlated strongly with a decrease in a behavioral measure of selective spatial processing. Our results suggest that, while cholinergic enhancement facilitates visual attention by increasing activity in extrastriate cortex generally, it accomplishes this in a manner that reduces expectation-driven selective biasing of extrastriate cortex.

Highly purified CD38+ and CD38- sub-clones derived from the same chronic lymphocytic leukemia patient have distinct gene expression signatures despite their monoclonal origin.

CD38 expression is an important prognostic marker in chronic lymphocytic leukemia (CLL) with high levels of CD38 associated with shorter overall survival. In this study, we used gene expression profiling and protein analysis of highly purified cell-sorted CD38(+) and CD38(-) chronic lymphocytic leukemia cells to elucidate a molecular basis for the association between CD38 expression and inferior clinical outcome. Paired CD38(+) and CD38(-) CLL cells derived from the same patient were shown to be monoclonal by V(H) gene sequencing but despite this, CD38(+) CLL cells possessed a distinct gene expression profile when compared with their CD38(-) sub-clones. Importantly, CD38(+) CLL cells relatively over expressed vascular endothelial growth factor (VEGF) and appeared to preferentially utilize an internal autocrine VEGF survival loop. Elevated VEGF expression was associated with increased expression of the anti-apoptotic protein Mcl-1. Inhibition of VEGF receptor signaling also resulted in a reduction in cell viability. In contrast, exogenous VEGF caused a significant increase in CD38(-) CLL cell viability and a marked induction of Mcl-1; both effects were less obvious in CD38(+) CLL cells. Taken together, our data provide a biological rationale for the poor prognosis of CD38(+) CLL and indicate that both VEGF and Mcl-1 may prove to be useful therapeutic targets.

Consequences of mitochondrial injury induced by pharmaceutical fatty acid oxidation inhibitors is characterized in human and rat liver slices.

Inhibition of liver mitochondrial beta-oxidation by pharmaceuticals may lead to safety concerns including mitochondrial dysfunction, lipid accumulation, inflammation and necrosis. In this study, the consequences of mitochondrial beta-oxidation inhibition by pharmaceuticals is investigated in human and rat liver slices. The fatty acid oxidation inhibitors Etomoxir and CPI975, inhibit the rate limiting mitochondrial beta-oxidation enzyme carnitine palmitoyltransferase I, while FOX988 and SDZ51-641, sequester mitochondrial coenzyme A to inhibit carnitine palmitoyltransferase II. Mitochondrial dysfunction was evident by a significant decrease of liver slice ATP levels and mitochondrial injury was verified by ultrastructural changes in morphology, manifested as enlarged mitochondria, C- or O-shaped mitochondria, and granular or crystalline inclusions. Gene expression changes were evident prior to changes in mitochondrial morphology. Time- and concentration dependent changes in mitochondrial genes linked with respiration and mitochondrial fatty acid beta-oxidation were associated with an up-regulation of peroxisome fatty acid oxidation genes, likely as a compensatory mechanism for the inhibition of the mitochondrial pathways. Gene expression changes preceding the decline of liver slice ATP and GSH levels included an up-regulation of stress response and oxidative stress gene expression, as well as genes linked with transcription, transporters, proliferation, cell matrix and signaling. In association with the decline of liver slice ATP and GSH was increased apoptosis and inflammation. Caspase activity, a functional indicator of apoptosis, was significantly increased as well as an up-regulation of genes linked with apoptosis. The increased gene and protein expression of the pro-inflammatory cytokine IL-8, produced by endothelial cells, is likely in response to the manifestation of oxidative stress and GSH depletion; further amplifying the oxidative stress response induced by the fatty acid oxidation inhibitors and triggering an inflammatory response. In summary, human and rat liver slices exhibited similar effects to the inhibitors of mitochondrial beta-oxidation, and the mitochondrial injury is associated with apoptosis and inflammation in the liver slices.

Determination of hyperfine field distributions in amorphous magnets.

We present an overview of two leading methods of determining probability distributions from Mössbauer spectra, using the model amorphous magnet Fe(80)B(20). A comparison is made between the maximum-entropy method, which permits analysis using truly arbitrary parameter probability distributions, and a Voigtian-based analysis, which uses a sum of Gaussian components to create parameter distributions of pseudo-arbitrary shape. Our results indicate that, in Fe(80)B(20), a Gaussian distribution of magnetic hyperfine fields is a very good approximation, although small deviations from a Gaussian shape are evident. We find that the apparent existence of correlations between the isomer shift and magnetic hyperfine field parameters, as found using Voigt-based analyses, may be an artefact of imposing a Gaussian shape on the parameter distributions. We conclude that maximum entropy and Voigtian analyses together provide a very powerful means of characterizing magnetic materials with Mössbauer spectroscopy.

Metabolism of benzo(a)pyrene by subcellular fractions of rat liver: evidence for similar patterns of cytochrome P-450 in rough and smooth endoplasmic reticulum but not in nuclei and plasma membrane.

Since our earlier work (P. Stasiecki, F. Oesch, G. Bruder, E.D. Jarasch, and W.W. Franke, Eur. J. Cell Biol., 21: 79-92, 1980) had shown that carcinogen-metabolizing monooxygenase activity was present in almost all investigated cellular membranes, the possibility of differential control of the various metabolic pathways in the individual cellular membranes arose. Using high pressure liquid chromatography we have now studied the benzo(a)pyrene metabolites formed by rough and smooth endoplasmic reticulum, nuclei, and plasma membrane as well as mitochondrial fractions and investigated the metabolic cooperation between the monooxygenases and epoxide hydrolase in these fractions. Since various cytochrome P-450 isozymes catalyze the oxidative attack on the benzo(a)pyrene molecule at defined preferential sites, this analysis also provides an indirect trace of potential differences in the pattern of cytochrome P-450 isozymes present in the individual membranes. The metabolic profiles produced by the two most active fractions, smooth and rough endoplasmic reticulum, were very similar to each other but different from those produced by the other three preparations. The metabolite pattern produced by incubations containing nuclear fractions differed slightly from that produced by the fractions of endoplasmic reticulum, but plasma membrane and mitochondria produced markedly different patterns. Since the similarity of the benzo(a)pyrene metabolite pattern produced by the smooth and rough endoplasmic reticulum suggested similar cytochrome P-450 isozyme patterns in these two subfractions, they were further investigated by the use of selective inducers as well as a broad spectrum substrate, 7-ethoxy-coumarin, in the absence and presence of selective inhibitors. Treatment of animals with trans-stilbene oxide or phenobarbital (a) increased the total amount of metabolites per protein mass and time, (b) changed the pattern of metabolites, but (c) induced a pattern of metabolites which was again very similar in rough and smooth endoplasmic reticulum. Even more distinct changes were found following treatment with 3-methylcholanthrene or beta-naphthoflavone. Both of these compounds (a) preferentially induced the activity of rough endoplasmic reticulum, (b) changed the profile of metabolites, but (c) again did not disturb the similarities of the benzo(a)pyrene metabolite pattern between both fractions.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of furosemide on unidirectional fluxes of sodium and chloride across the skin of the frog, Rana pipiens.

1. The diuretic furosemide, when added to the outside solution at a concentration of 5-10-4 M, increases the electrical potential difference (PD) across the isolated frog skin, but the short-circuit current (Isc) is unchanged. Lower concentrations had no significant effect on these electrical parameters. 2. When SO42- or NO3- are substituted for Cl- in the Ringer's solution furosemide has no effect on the PD or Isc. 3. Simultaneous unidirectional fluxes of Na+ and Cl- show that furosemide (5-10-4 M outside) reduces both the influx and outflux of Cl-, while the Na+ fluxes are not altered. 4. Furosemide (5-10-4 M) on the corium side of the frog skin had no significant effect on either PD, Isc or undirectional fluxes of Cl-. 5. It is suggested that furosemide reduces passive Cl- transfer, possibly by interacting with the Cl-/Cl- exchange diffusion mechanism which has been observed in this tissue. These observations further suggest that perhaps the diuretic action of furosemide may be mediated by such an effect on passive Cl- permeability which is linked to the active Cl- transport mechanism in the renal tubule.

Latency of epoxide hydratase and its relationship to that of UDPglucuronyltransferase.

Epoxide hydratase activity in liver microsomal preparations from adult made rats is latent to a slight extent. Maximal activations with neutral or anionic detergents were 30-60% whilst UDPglucuronyltransferase was maximally activated by 160-830% by the same detergents. Activation of microsomal epoxide hydratase requires much higher amounts of neutral or anionic detergents than activation of microsomal UDPglucuronyltransferase. High concentrations of inorganic salt, sonication or freeze-thawing which activate microsomal UDPglucuronyltransferase have no influence on microsomal epoxide hydratase activity. From this it appears that the activation which may involve either removal of a permeability barrier or release from conformational restraint occurs more easily for UDPglucuronyltransferase than for epoxide hydratase and that the activation of microsomal epoxide hydratase requires breakage of some hydrophobic bonds between the enzyme and membrrane component(s).

Inhibition of alpha-aminoisobutyric acid uptake by diisothiocyanostilbenedisulphonic acid in the amphibian cornea.

alpha-Aminoisobutyric acid accumulation of the toad's (Bufo marinus) cornea and lens is inhibited by 4,4'-diisothiocyano-2,2'-stilbenedisulfonic acid. This effect is seen at pH 8.4; at pH 7.4 a small increase in aminoisobutyric acid uptake was observed. Efflux of aminoisobutyric acid is unchanged by diisothiocyanostilbenedisulphonic acid at either pH. The inhibitory effect of diisothiocyanostilbenedisulphonic acid on aminoisobutyric acid accumulation appears to reflect a direct action on membrane mechanisms that mediate its influx.