Evolution of Nanowire Transmon Qubits and Their Coherence in a Magnetic Field.

We present an experimental study of flux- and gate-tunable nanowire transmons with state-of-the-art relaxation time allowing quantitative extraction of flux and charge noise coupling to the Josephson energy. We evidence coherence sweet spots for charge, tuned by voltage on a proximal side gate, where first order sensitivity to switching two-level systems and background 1/f noise is minimized. Next, we investigate the evolution of a nanowire transmon in a parallel magnetic field up to 70 mT, the upper bound set by the closing of the induced gap. Several features observed in the field dependence of qubit energy relaxation and dephasing times are not fully understood. Using nanowires with a thinner, partially covering Al shell will enable operation of these circuits up to 0.5 T, a regime relevant for topological quantum computation and other applications.

Experimentally simulating the dynamics of quantum light and matter at deep-strong coupling.

The quantum Rabi model describing the fundamental interaction between light and matter is a cornerstone of quantum physics. It predicts exotic phenomena like quantum phase transitions and ground-state entanglement in ultrastrong and deep-strong coupling regimes, where coupling strengths are comparable to or larger than subsystem energies. Demonstrating dynamics remains an outstanding challenge, the few experiments reaching these regimes being limited to spectroscopy. Here, we employ a circuit quantum electrodynamics chip with moderate coupling between a resonator and transmon qubit to realise accurate digital quantum simulation of deep-strong coupling dynamics. We advance the state of the art in solid-state digital quantum simulation by using up to 90 second-order Trotter steps and probing both subsystems in a combined Hilbert space dimension of ∼80, demonstrating characteristic Schrödinger-cat-like entanglement and large photon build-up. Our approach will enable exploration of extreme coupling regimes and quantum phase transitions, and demonstrates a clear first step towards larger complexities such as in the Dicke model.

Interaction of tolbutamide and cytosolic nucleotides in controlling the ATP-sensitive K+ channel in mouse beta-cells.

1. In mouse pancreatic beta-cells the role of cytosolic nucleotides in the regulation of the sulphonylurea sensitivity of the adenosine 5'-triphosphate-sensitive K+ channel (KATP-channel) was examined. Patch-clamp experiments with excised inside-out membrane patches were carried out using an experimental protocol favouring phosphorylation of membrane proteins. 2. In the absence of Mg2+, the KATP-channel-inhibiting potency of cytosolic nucleotides decreased in the order ATP = adenosine 5'-O-(3-thiotriphosphate) (ATP gamma S) > adenosine 5'-diphosphate (ADP) > adenosine 5'-O-(2-thiodiphosphate) (ADP beta S) = adenylyl-imidodiphosphate (AMP-PNP) > 2'-deoxyadenosine 5'-triphosphate (dATP) > uridine 5'-triphosphate (UTP) > 2'-deoxyadenosine 5'-diphosphate (dADP) > guanosine 5'-triphosphate (GTP) > guanosine 5'-diphosphate (GDP) > uridine 5'-diphosphate (UDP). 3. In the presence of Mg2+, the inhibitory potency of cytosolic nucleotides decreased in the order ATP gamma S > ATP > AMP-PNP > ADP beta S > dATP > UTP. In the presence of Mg2+, the KATP-channels were activated by dADP, GTP, GDP and UDP. 4. Tolbutamide inhibited the KATP-channels not only in the presence but also in the prolonged absence of Mg2+. In nucleotide-free solutions, the potency of tolbutamide was very low. When about half of the KATP-channel activity was inhibited by ATP, AMP-PNP, ADP beta S or ADP (absence of Mg2+), the potency of tolbutamide was increased. 5. Tolbutamide (100 microM) slightly enhanced the channel-inhibiting potency of AMP-PNP and inhibited the channel-activating effect of MgGDP in a non-competitive manner. 6. Channel activation by MgGDP (0.5 mM) competitively antagonized the inhibitory responses to AMP-PNP (1 MicroM- 1 mM). This effect of GDP was neutralized by tolbutamide (100 MicroM).7. The stimulatory effect of 0.5 mM MgGDP was neutralized by 200 MicroM AMP-PNP. Under these conditions the potency of tolbutamide was much higher than in the presence of 0.5 mM MgGDP alone or in the absence of any nucleotides.8. dADP (0.3-1 mM) increased the potency of tolbutamide. Additional application of 200 MicroM AMPPNP caused a further increase in the potency of tolbutamide.9. In conclusion, in the simultaneous presence of inhibitory and stimulatory nucleotides, binding of sulphonylureas to their receptor causes direct inhibition of channel activity, non-competitive inhibition of the action of stimulatory nucleotides and interruption of the competitive interaction between stimulatory and inhibitory nucleotides. The latter effect increases the proportion of KATP- channels staying in the nucleotide-blocked state. In addition, this state potentiates the direct effect of sulphonylureas.

Location of the sulphonylurea receptor at the cytoplasmic face of the beta-cell membrane.

1. In insulin-secreting cells the location of the sulphonylurea receptor was examined by use of a sulphonylurea derivative representing the glibenclamide molecule devoid of its cyclohexy moiety (compound III) and a benzenesulphonic acid derivative representing the glibenclamide molecule devoid of its cyclohexylurea moiety (compound IV). At pH 7.4 compound IV is only present in charged form. 2. Lipid solubility declined in the order tolbutamide > compound III > compound IV. 3. The dissociation constant (KD) for binding of compound IV to the sulphonylurea receptor in HIT-cells (pancreatic beta-cell line) was similar to the KD value for tolbutamide and fourfold higher than the KD value for compound III. 4. In mouse pancreatic beta-cells, drug concentrations inhibiting adenosine 5'-triphosphate-sensitive K+ channels (KATP-channels) half-maximally (EC50) were determined by use of the patch-clamp technique. When the drugs were applied to the extracellular side of outside-out or the intracellular side of inside-out membrane patches, the ratio of extracellular to intracellular EC50 values was 281 for compound IV, 25.5 for compound III and 1.2 for tolbutamide. 5. In mouse pancreatic beta-cells, measurement of KATP-channel activity in cell-attached patches and recording of insulin release displayed much higher EC50 values for compound IV than inside-out patch experiments. A corresponding, but less pronounced difference in EC50 values was observed for compound III, whereas the EC50 values for tolbutamide did not differ significantly. 6. It is concluded that the sulphonylurea receptor is located at the cytoplasmic face of the beta-cell plasma membrane. Receptor activation is induced by the anionic forms of sulphonylureas and their analogues.

Diazoxide-sensitivity of the adenosine 5'-triphosphate-dependent K+ channel in mouse pancreatic beta-cells.

1. In mouse pancreatic beta-cells the regulation of the diazoxide-sensitivity of the adenosine 5'-triphosphate-dependent K+ channel (K-ATP-channel) was examined by use of the patch-clamp technique. 2. In intact beta-cells incubated at 37 degrees C in the presence of 3 mM D-glucose, diazoxide did not affect the single channel conductance but stimulated channel-opening activity. Diazoxide produced half-maximal effects at 82 microM and 13 fold activation at maximally effective concentrations (300-400 microM). The response to diazoxide (300 microM) was not completely suppressed by saturating tolbutamide concentrations (1 or 5 mM). 3. Inside-out patch-clamp experiments were carried out using an experimental protocol favouring phosphorylation of membrane proteins. Under these conditions diazoxide was ineffective in the absence of any nucleotides, weakly effective in the presence of MgATP (26 or 87 microM) and strongly effective in the presence of the Mg complexes of adenosine 5'-diphosphate, 2'-deoxyadenosine 5'-diphosphate or guanosine 5'-diphosphate (MgADP, MgdADP or MgGDP). 4. In inside-out patches exposed to nucleotide-free solutions, saturating concentrations of tolbutamide did not cause complete block of K-ATP-channels. When the channels were activated by MgdADP (48 microM), tolbutamide was even less effective. Sensitization of MgdADP-induced channel activation by diazoxide further weakened the effects of tolbutamide. 5. Diazoxide (50 or 300 microM) prevented the complete channel block induced by saturating tolbutamide concentrations in the presence of Mg2+ and ADP (1 mM). 6. In the presence of Mg2", the K-ATP-channel-blocking potency of cytosolic ATP decreased in the order inside-out> outside-out> whole-cell configuration of the patch-clamp technique.7. It is concluded that the K-ATP-channel is controlled via four separate binding sites for inhibitory nucleotides (e.g. free ATP and ADP), stimulatory nucleotides (MgADP, MgdADP, MgGDP), sulphonylureas and diazoxide. Strong inhibition of the channel openings by sulphonylureas results from occupation of both sites for nucleotides. Diazoxide is only effective when the site for stimulatory nucleotides is occupied.

Desensitization of insulin secretory response to imidazolines, tolbutamide, and quinine. II. Electrophysiological and fluorimetric studies.

Prolonged in vitro exposure (18 h) of pancreatic islets to insulin secretagogues that block ATP-dependent K(+) channels (K(ATP) channels), such as sulfonylureas, imidazolines, and quinine, induced a desensitization of insulin secretion (Rustenbeck et al., pages 1685-1694, this issue). To elucidate the underlying mechanisms, K(ATP) channel activity, plasma membrane potential and the cytosolic Ca(2+) concentration ([Ca(2+)](i)) were measured in mouse single B-cells. In B-cells desensitized by phentolamine or quinine (100 microM each) K(ATP) channel activity was virtually absent and could not be elicited by diazoxide. Desensitization by alinidine (100 microM) induced a marked reduction of K(ATP) channel activity, which could be reversed by diazoxide, whereas exposure to idazoxan (100 microM) or tolbutamide (500 microM) had no lasting effect on K(ATP) channel activity. Correspondingly, phentolamine-, alinidine-, and quinine-desensitized B-cells were markedly depolarized, whereas B-cells that had been exposed to tolbutamide or idazoxan had an unchanged resting membrane potential. The increase in [Ca(2+)](i) normally elicited by phentolamine and alinidine was suppressed after desensitization by these compounds, whereas the [Ca(2+)](i) increase by re-exposure to quinine was markedly reduced and that by tolbutamide only minimally affected as compared with control-cultured B-cells. The increase in [Ca(2+)](i) elicited by a K(+) depolarization was diminished in secretagogue-pretreated B-cells, the extent depending on the secretagogue. This effect was closely correlated with the degree of depolarization after pretreatment with the respective secretagogue. In conclusion, the apparently uniform desensitization of secretion by K(ATP) channel blockers is due to different effects at two stages located distally in the stimulus-secretion coupling: either at the stage of [Ca(2+)](i) regulation, where the increase is depressed as a consequence of a persistent depolarization (e.g. in the case of phentolamine or alinidine) and/or at the stage of exocytosis, which responds only weakly to substantial increases in [Ca(2+)](i) (in the case of tolbutamide).

Effects of imidazoline compounds on cytoplasmic Ca2+ concentration and ATP-sensitive K+ channels in pancreatic B-cells.

Phentolamine, an alpha-adrenoceptor-blocking agent with an imidazoline structure, induces an increase in the cytoplasmic Ca2+ concentration of pancreatic B-cells. This effect occurs at a concentration (32 microM) at which phentolamine is able to enhance glucose-induced insulin secretion. The increase in cytoplasmic Ca2+ concentration caused by phentolamine is additive to the one elicited by a maximally effective concentration of tolbutamide (100 microM). Imidazoline-binding sites in insulin-secreting HIT cells can also be occupied by the guanidinium compound guanabenz, which was found to be a potent and reversible blocker of ATP-dependent K(+)-channels in B-cells. In contrast to phentolamine, guanabenz blocks the ATP-dependent K(+)-channels only in the inside-out mode, but not in the cell-attached mode of the patch-clamp technique. In conclusion, imidazolines and structurally related compounds block ATP-dependent K(+)-channels by binding to the cytoplasmic face of the plasma membrane, and may have effects on other ion channels which contribute to the elevation of cytoplasmic Ca2+ concentration and, consequently, to insulin release.

Mitochondria present in excised patches from pancreatic B-cells may form microcompartments with ATP-dependent potassium channels.

Experiments with inside-out patches excised from pancreatic B-cells have yielded evidence that mitochondria are often contained in the cytoplasmic plug protruding into the tip of patch pipette. When intact B-cells were loaded with the fluorescent mitochondrial stain, rhodamine 123, and membrane patches excised from these cells, a green fluorescence could be observed in the lumen at the tip of the patch pipette. The same result was obtained with the mitochondrial stain, MitoTracker Green FM, which is only fluorescent in a membrane-bound state. Furthermore, the open probability of ATP-dependent potassium (K(ATP)) channels in inside-out patches was influenced by mitochondrial fuels and inhibitors. Respiratory substrates like tetramethyl phenylene diamine (2 mM) plus ascorbate (5 mM) or alpha-ketoisocaproic acid (10 mM) reduced the open probability of K(ATP) channels in inside-out patches significantly (down to 57% or 65% of control, respectively). This effect was antagonized by the inhibitor of cytochrome oxidase, sodium azide (5 mM). Likewise, the inhibitor of succinate dehydrogenase, malonate (5 mM), increased the open probability of K(ATP) channels in the presence of succinate (1 mM). However, oligomycin in combination with antimycin and rotenone did not increase open probability. Although it cannot be excluded that these effects result from a direct interaction with the K(ATP) channels, the presence of mitochondria in the close vicinity permits the hypothesis that changes in mitochondrial metabolism are involved, mitochondria and K(ATP) channels thus forming functional microcompartments.

Inhibition of human insulin gene transcription by peroxisome proliferator-activated receptor gamma and thiazolidinedione oral antidiabetic drugs.

BACKGROUND AND PURPOSE: The transcription factor peroxisome proliferator-activated receptor gamma (PPARgamma) is essential for glucose homeostasis. PPARgamma ligands reducing insulin levels in vivo are used as drugs to treat type 2 diabetes mellitus. Genes regulated by PPARgamma have been found in several tissues including insulin-producing pancreatic islet beta-cells. However, the role of PPARgamma at the insulin gene was unknown. Therefore, the effect of PPARgamma and PPARgamma ligands like rosiglitazone on insulin gene transcription was investigated. EXPERIMENTAL APPROACH: Reporter gene assays were used in the beta-cell line HIT and in primary mature pancreatic islets of transgenic mice. Mapping studies and internal mutations were carried out to locate PPARgamma-responsive promoter regions. KEY RESULTS: Rosiglitazone caused a PPARgamma-dependent inhibition of insulin gene transcription in a beta-cell line. This inhibition was concentration-dependent and had an EC(50) similar to that for the activation of a reporter gene under the control of multimerized PPAR binding sites. Also in normal primary pancreatic islets of transgenic mice, known to express high levels of PPARgamma, rosiglitazone inhibited glucose-stimulated insulin gene transcription. Transactivation and mapping experiments suggest that, in contrast to the rat glucagon gene, the inhibition of the human insulin gene promoter by PPARgamma/rosiglitazone does not depend on promoter-bound Pax6 and is attributable to the proximal insulin gene promoter region around the transcription start site from -56 to +18. CONCLUSIONS AND IMPLICATIONS: The human insulin gene represents a novel PPARgamma target that may contribute to the action of thiazolidinediones in type 2 diabetes mellitus.

Loss of insulin-induced inhibition of glucagon gene transcription in hamster pancreatic islet alpha cells by long-term insulin exposure.

AIMS/HYPOTHESIS: Diabetes mellitus type 2 is characterised by hyperglucagonaemia, resulting in hepatic glucose production and hyperglycaemia. Considering that insulin inhibits glucagon secretion and gene transcription, hyperglucagonaemia in the face of hyperinsulinaemia in diabetes mellitus type 2 suggests that there is insulin resistance also at the glucagon-producing pancreatic islet alpha cells. However, the molecular mechanism of alpha cell insulin resistance is unknown. Therefore, the effect of molecules implicated in conferring insulin resistance in some other tissues was investigated on insulin-induced inhibition of glucagon gene transcription in alpha cells. METHODS: Reporter gene assays and biochemical techniques were used in the glucagon-producing hamster pancreatic islet alpha cell line InR1-G9. RESULTS: From among 16 agents tested, chronic insulin treatment was found to abolish insulin-induced inhibition of glucagon gene transcription. Overproduction of constitutively active protein kinase B (PKB) still inhibited glucagon gene transcription after chronic insulin treatment; together with a markedly reduced insulin-induced phosphorylation and, thus, activation of PKB, this indicates that targets upstream of PKB within the insulin signalling pathway are affected. Indeed, chronic insulin treatment markedly reduced IRS-1 phosphorylation, insulin receptor (IR) autophosphorylation and IR content. Cycloheximide and in vivo labelling experiments attributed IR downregulation to enhanced degradation. CONCLUSIONS/INTERPRETATION: These results show that an extended exposure of alpha cells to insulin induces IR downregulation and loss of insulin-induced inhibition of glucagon gene transcription. They suggest that hyperinsulinaemia, through IR downregulation, may confer insulin resistance to pancreatic islet alpha cells in diabetes mellitus type 2.

Cytosolic nucleotides enhance the tolbutamide sensitivity of the ATP-dependent K+ channel in mouse pancreatic B cells by their combined actions at inhibitory and stimulatory receptors.

In the plasma membrane of pancreatic B cells, a K+ channel (K-ATP channel) has been identified that is regulated by cytoplasmic nucleotides. This channel is inhibited by sulfonylureas. We have previously shown that the potency of tolbutamide is much lower in excised membrane patches than in intact cells, unless the internal side of the membrane is exposed to the Mg2+ complex of ADP (MgADP). In the present study, the mechanism of this interactive control by sulfonylureas and nucleotides was examined using the inside-out configuration of the patch-clamp technique. When test solutions containing Mg2+ ions were applied, the opening activity of the K-ATP-channels was strongly stimulated by 2'-deoxyadenosine-5'-diphosphate (dADP) or GDP, slightly stimulated by ADP, and inhibited by adenosine-5'-O-(2-thiodiphosphate) (ADP beta S) or adenylyl-imidodiphosphate (AMP-PNP). In the presence of Mg2+, not only ADP but also its analogues dADP (1 mM) and ADP beta S (0.1 mM) enhanced the potency of tolbutamide for channel inhibition; dADP at a low concentration (0.2 mM), GDP (0.2-1 mM), and AMP-PNP (0.2 mM) did not alter the potency of tolbutamide. The particular feature of the test solutions that enhanced the potency of tolbutamide was the presence of Mg(2+)-bound and free nucleotides at channel-stimulating and channel-inhibiting concentrations, respectively. In the presence of Mg2+ and 0.2 mM dADP or 0.2-1 mM GDP, 0.2 mM AMP-PNP intensified the response to tolbutamide by serving as channel-inhibiting component. MgAMP-PNP did not stimulate the opening activity of the K-ATP channel. The sensitivity to tolbutamide that was enhanced by a submaximally effective ADP concentration was further increased by AMP-PNP or ATP but not by GDP. The sensitivity to the sulfonylurea analogue meglitinide was also enhanced by ADP. It is concluded that nucleotides inhibit and activate the K-ATP channel by interaction with two separate receptor sites at the cytoplasmic face of the B cell membrane. Effective inhibition of the channel openings by sulfonylureas results from the simultaneous occupation of both sites by appropriate nucleotides.

Bathing/hygiene self-care deficit: defining characteristics and related factors across age groups and diagnosis-related groups in an acute care setting.

The purpose of this descriptive study was to validate the nursing diagnosis, bathing/hygiene self-care deficit. Defining characteristics and related factors were abstracted retrospectively from a computerized patient care planning database. Data were treated to descriptive statistics and chi-square analysis to determine frequencies and percentages. Major support was found for the defining characteristic "inability to wash body or body parts" (84%) and minor support was garnered for "inability to obtain/access water source" (77%). Related factors associated with the diagnosis were also examined for this acute-care patient population. The percentages of occurrence were decreased activity tolerance (40%); mobility impairment (24%), pain (19%), musculoskeletal impairment (19%), neuromuscular impairment (9%), and perceptual or cognitive impairment (4%). The diagnosis was found among 80 DRGs and across all age groups (range, 9-92 years).

Ancient HLA genes from 7,500-year-old archaeological remains.

In the past decade there has been increasing interest in cloning DNA from ancient and preserved tissues. Most studies, however, have focused on mitochondrial or chloroplast genes, present at hundreds to thousands of copies per cell compared with one or two for each nuclear gene. With a probe containing Alu repeat sequences, Pääbo isolated a 3.4-kilobase DNA fragment from a 2,400-year-old Egyptian mummy which was subsequently shown to contain an intron of the nuclear gene HLA-DQA (ref. 11). Here we report a more targeted approach to the characterization of nuclear genes from archaeological specimens. The Windover pond of central Florida has provided skeletal and soft tissue remains from 165 humans, radiocarbon-dated to be 6,990-8,130 years old. Using DNA obtained from one individual we have characterized segments from six nuclear genes: that for beta 2-microglobulin and five members of the class I HLA heavy chain gene family. Distinctive patterns of nucleotide substitution in the cloned heavy chain gene segments permit tentative assignment of the HLA-A,B type of the ancient individual.

Inter- and intrapopulation studies of ancient humans.

For a genetic analysis of ancient human populations to be useful, it must be demonstrated that the DNA samples under investigation represent a single human population. Toward that end, we have analyzed human DNA from the Windover site (7000-8000 BP). MHC-I analysis, using allele-specific oligonucleotide hybridization to PCR amplified Windover DNA, microsatellite analysis by PCR of the APO-A2 repeat and mtD-loop 3' region sequencing on multiple individuals spanning nearly the full range of estimated burial dates all confirm the hypothesis that there is a persistence of both nuclear and mitochondrial haplotypes at Windover throughout its entire period of use. Thus, Windover can be considered a single population. Neighbor-joining tree analysis of mtDNA sequences suggests that some mitochondrial types are clearly related to extant Amerind types, whereas others, more distantly related, may reflect genetically distinct origins. A more complete sequence analysis will be required to firmly resolve this issue. Calibrating genetic relationships deduced by tree analysis, radiocarbon dates and burial position, yields a human mtD-loop DNA rate of evolution of 3700 to 14,000 years per percent change. Both values are within the range of recent, independently calculated values using estimates of evolutionary divergence or theoretical population genetics. Thus we are beginning to realize the promise of ancient DNA analysis to experimentally answer heretofore unapproachable questions regarding human prehistory and genetic change.

Blepharophimosis syndrome is linked to chromosome 3q.

Blepharophimosis syndrome (BPES, blepharophimosis eyelid syndrome) is a distinctive congenital eyelid malformation which can occur sporadically or be inherited in an autosomal dominant fashion. Previous reports have described associated cytogenetic abnormalities on chromosome 3q. We have ascertained and sampled two BPES families with apparent autosomal dominant inheritance and have tested for linkage with 17 polymorphic markers on 3q. Multipoint analysis generated a maximum LOD score of 3.23 using the markers RHO, ACPP and D3S1238. No evidence of genetic heterogeneity was observed. These studies provide the first non-cytogenetic evidence that a defective gene responsible for BPES is located on 3q22.