The variable domain from dynamin-related protein 1 promotes liquid-liquid phase separation that enhances its interaction with cardiolipin-containing membranes

Dynamins are an essential superfamily of mechanoenzymes that remodel membranes and often contain a "variable domain" important for regulation. For the mitochondrial fission dynamin, dynamin-related protein 1, a regulatory role for the variable domain (VD) is demonstrated by gain- and loss-of-function mutations, yet the basis for this is unclear. Here, the isolated VD is shown to be intrinsically disordered and undergo a cooperative transition in the stabilizing osmolyte trimethylamine N-oxide. However, the osmolyte-induced state is not folded and surprisingly appears as a condensed state. Other co-solutes including known molecular crowder Ficoll PM 70, also induce a condensed state. Fluorescence recovery after photobleaching experiments reveal this state to be liquid-like indicating the VD undergoes a liquid-liquid phase separation under crowding conditions. These crowding conditions also enhance binding to cardiolipin, a mitochondrial lipid, which appears to promote phase separation. Since dynamin-related protein 1 is found assembled into discrete punctate structures on the mitochondrial surface, the inference from the present work is that these structures might arise from a condensed state involving the VD that may enable rapid tuning of mechanoenzyme assembly necessary for fission.

The variable domain from the mitochondrial fission mechanoenzyme Drp1 promotes liquid-liquid phase separation

Dynamins are an essential superfamily of mechanoenzymes that remodel membranes and often contain a "variable domain" (VD) important for regulation. For the mitochondrial fission dynamin, Drp1, a regulatory role for the VD is demonstrated by mutations that can elongate, or fragment, mitochondria. How the VD encodes inhibitory and stimulatory activity is unclear. Here, isolated VD is shown to be intrinsically disordered (ID) yet undergoes a cooperative transition in the stabilizing osmolyte TMAO. However, the TMAO stabilized state is not folded and surprisingly appears as a condensed state. Other co-solutes including known molecular crowder Ficoll PM 70, also induce a condensed state. Fluorescence recovery after photobleaching experiments reveal this state to be liquid-like indicating the VD undergoes a liquid-liquid phase separation under crowding conditions. These crowding conditions also enhance binding to cardiolipin, a mitochondrial lipid, raising the possibility that phase separation may enable rapid tuning of Drp1 assembly necessary for fission.

β-cell-selective inhibition of DNA damage response signaling by nitric oxide is associated with an attenuation in glucose uptake

Nitric oxide (NO) plays a dual role in regulating DNA damage response (DDR) signaling in pancreatic β-cells. As a genotoxic agent, NO activates two types of DDR signaling; however, when produced at micromolar levels by the inducible isoform of NO synthase, NO inhibits DDR signaling and DDR-induced apoptosis in a β-cell-selective manner. DDR signaling inhibition by NO correlates with mitochondrial oxidative metabolism inhibition and decreases in ATP and NAD+. Unlike most cell types, β-cells do not compensate for impaired mitochondrial oxidation by increasing glycolytic flux, and this metabolic inflexibility leads to a decrease in ATP and NAD+. Here, we used multiple analytical approaches to determine changes in intermediary metabolites in β-cells and non-β-cells treated with NO or complex I inhibitor rotenone. In addition to ATP and NAD+, glycolytic and tricarboxylic acid cycle intermediates as well as NADPH are significantly decreased in β-cells treated with NO or rotenone. Consistent with glucose-6-phosphate residing at the metabolic branchpoint for glycolysis and the pentose phosphate pathway (NADPH), we show that mitochondrial oxidation inhibitors limit glucose uptake in a β-cell-selective manner. Our findings indicate that the β-cell-selective inhibition of DDR signaling by NO is associated with a decrease in ATP to levels that fall significantly below the KM for ATP of glucokinase (glucose uptake) and suggest that this action places the β-cell in a state of suspended animation where it is metabolically inert until NO is removed, and metabolic function can be restored.

Understanding Reentrance in Frustrated Magnets: The Case of the Er_{2}Sn_{2}O_{7} Pyrochlore

Reentrance, the return of a system from an ordered phase to a previously encountered less-ordered one as a controlled parameter is continuously varied, is a recurring theme found in disparate physical systems, yet its microscopic cause is often not investigated thoroughly. Here, through detailed characterization and theoretical modeling, we uncover the microscopic mechanism behind reentrance in the strongly frustrated pyrochlore antiferromagnet Er_{2}Sn_{2}O_{7}. We use single crystal heat capacity measurements to expose that Er_{2}Sn_{2}O_{7} exhibits multiple instances of reentrance in its magnetic field B vs temperature T phase diagram for magnetic fields along three cubic high symmetry directions. Through classical Monte Carlo simulations, mean field theory, and classical linear spin-wave expansions, we argue that the origins of the multiple occurrences of reentrance observed in Er_{2}Sn_{2}O_{7} are linked to soft modes. These soft modes arise from phase competition and enhance thermal fluctuations that entropically stabilize a specific ordered phase, resulting in an increased transition temperature for certain field values and thus the reentrant behavior. Our work represents a detailed examination into the mechanisms responsible for reentrance in a frustrated magnet and may serve as a template for the interpretation of reentrant phenomena in other physical systems.

Magnetic properties of the Ising-like rare earth pyrosilicate: D-Er2Si2O7

Ising-like spin-1/2 magnetic materials are of interest for their ready connection to theory, particularly in the context of quantum critical behavior. In this work we report detailed studies of the magnetic properties of a member of the rare earth pyrosilicate family, D-Er₂Si₂O₇, which is known to display a highly anisotropic Ising-likeg-tensor and effective spin-1/2 magnetic moments. We used powder neutron diffraction, powder inelastic neutron spectroscopy (INS), and single crystal AC susceptibility to characterize its magnetic properties. Neutron diffraction enabled us to determine the magnetic structure below the known transition temperature (T_N= 1.9 K) in zero field, confirming that the magnetic state is a four-sublattice antiferromagnetic structure with two non-collinear Ising axes, as was previously hypothesized. Our powder INS data revealed a gapped excitation at zero field, consistent with anisotropic (possibly Ising) exchange. An applied field of 1 T produces a mode softening, which is consistent with a field-induced second order phase transition. To assess the relevance of D-Er₂Si₂O₇to the transverse field Ising model, we performed AC susceptibility measurements on a single crystal with the magnetic field oriented in the direction transverse to the Ising axes. This revealed a transition at 2.65 T at 0.1 K, a field significantly higher than the mode-softening field observed by powder INS, showing that the field-induced phase transitions are highly field-direction dependent as expected. These measurements suggest that D-Er₂Si₂O₇may be a candidate for further exploration related to the transverse field Ising model.

Novel Strongly Spin-Orbit Coupled Quantum Dimer Magnet: Yb_{2}Si_{2}O_{7}

The quantum dimer magnet (QDM) is the canonical example of quantum magnetism. The QDM state consists of entangled nearest-neighbor spin dimers and often exhibits a field-induced triplon Bose-Einstein condensate (BEC) phase. We report on a new QDM in the strongly spin-orbit coupled, distorted honeycomb-lattice material Yb_{2}Si_{2}O_{7}. Our single crystal neutron scattering, specific heat, and ultrasound velocity measurements reveal a gapped singlet ground state at zero field with sharp, dispersive excitations. We find a field-induced magnetically ordered phase reminiscent of a BEC phase, with exceptionally low critical fields of H_{c1}∼0.4 and H_{c2}∼1.4  T. Using inelastic neutron scattering in an applied magnetic field we observe a Goldstone mode (gapless to within δE=0.037  meV) that persists throughout the entire field-induced magnetically ordered phase, suggestive of the spontaneous breaking of U(1) symmetry expected for a triplon BEC. However, in contrast to other well-known cases of this phase, the high-field (μ_{0}H≥1.2  T) part of the phase diagram in Yb_{2}Si_{2}O_{7} is interrupted by an unusual regime signaled by a change in the field dependence of the ultrasound velocity and magnetization, as well as the disappearance of a sharp anomaly in the specific heat. These measurements raise the question of how anisotropy in strongly spin-orbit coupled materials modifies the field induced phases of QDMs.

Quantum Spin Ice Dynamics in the Dipole-Octupole Pyrochlore Magnet Ce_{2}Zr_{2}O_{7}

Neutron scattering measurements on the pyrochlore magnet Ce_{2}Zr_{2}O_{7} reveal an unusual crystal field splitting of its lowest J=5/2 multiplet, such that its ground-state doublet is composed of m_{J}=±3/2, giving these doublets a dipole-octupole (DO) character with local Ising anisotropy. Its magnetic susceptibility shows weak antiferromagnetic correlations with θ_{CW}=-0.4(2)  K, leading to a naive expectation of an all-in, all-out ordered state at low temperatures. Instead, our low-energy inelastic neutron scattering measurements show a dynamic quantum spin ice state, with suppressed scattering near |Q|=0, and no long-range order at low temperatures. This is consistent with recent theory predicting symmetry-enriched U(1) quantum spin liquids for such DO doublets decorating the pyrochlore lattice. Finally, we show that disorder, especially oxidation of powder samples, is important in Ce_{2}Zr_{2}O_{7} and could play an important role in the low-temperature behavior of this material.

Behavior of the breathing pyrochlore lattice Ba3Yb2Zn5O11 in applied magnetic field

The breathing pyrochlore lattice material Ba₃Yb₂Zn₅O₁₁ exists in the nearly decoupled limit, in contrast to most other well-studied breathing pyrochlore compounds. As a result, it constitutes a useful platform to benchmark theoretical calculations of exchange interactions in insulating Yb³⁺ magnets. Here we study Ba₃Yb₂Zn₅O₁₁ at low temperatures in applied magnetic fields as a further probe of the physics of this model system. Experimentally, we consider the behavior of polycrystalline samples of Ba₃Yb₂Zn₅O₁₁ with a combination of inelastic neutron scattering and heat capacity measurements down to 75 mK and up to fields of 10 T. Consistent with previous work, inelastic neutron scattering finds a level crossing near 3 T, but no significant dispersion of the spin excitations is detected up to the highest applied fields. Refinement of the theoretical model previously determined at zero field can reproduce much of the inelastic neutron scattering spectra and specific heat data. A notable exception is a low temperature peak in the specific heat at  ∼0.1 K. This may indicate the scale of interactions between tetrahedra or may reflect undetected disorder in Ba₃Yb₂Zn₅O₁₁.

Disordered Route to the Coulomb Quantum Spin Liquid: Random Transverse Fields on Spin Ice in Pr_{2}Zr_{2}O_{7}

Inelastic neutron scattering reveals a broad continuum of excitations in Pr_{2}Zr_{2}O_{7}, the temperature and magnetic field dependence of which indicate a continuous distribution of quenched transverse fields (Δ) acting on the non-Kramers Pr^{3+} crystal field ground state doublets. Spin-ice correlations are apparent within 0.2 meV of the Zeeman energy. A random phase approximation provides an excellent account of the data with a transverse field distribution ρ(Δ)∝(Δ^{2}+Γ^{2})^{-1}, where Γ=0.27(1)  meV. Established during high temperature synthesis due to an underlying structural instability, it appears disorder in Pr_{2}Zr_{2}O_{7} actually induces a quantum spin liquid.

Iridium containing honeycomb Delafossites by topotactic cation exchange

We report the structure and magnetic properties of two new iridium-based honeycomb Delafossite compounds, Cu3NaIr2O6 and Cu3LiIr2O6, formed by a topotactic cation exchange reaction. The starting materials Na2IrO3 and Li2IrO3, which are based on layers of IrO6 octahedra in a honeycomb lattice separated by layers of alkali ions, are transformed to the title compounds by a topotactic exchange reaction through heating with CuCl below 450 °C; higher temperature reactions cause decomposition. The new compounds display dramatically different magnetic behavior from their parent compounds - Cu3NaIr2O6 has a ferromagnetic like magnetic transition at 10 K, while Cu3LiIr2O6 retains the antiferromagnetic transition temperature of its parent compound but displays significantly stronger dominance of antiferromagnetic coupling between spins. These results reveal that a surprising difference in the magnetic interactions between the magnetic Ir ions has been induced by a change in the non-magnetic interlayer species. A combination of neutron and X-ray powder diffraction is used for the structure refinement of Cu3NaIr2O6 and both compounds are compared to their parent materials.

Order by disorder spin wave gap in the XY pyrochlore magnet Er2Ti2O7

The recent determination of a robust spin Hamiltonian for the antiferromagnetic XY pyrochlore Er2Ti2O7 reveals a most convincing case of the "Order-by-Quantum-Disorder" mechanism for ground state selection. This mechanism relies on quantum fluctuations to remove an accidental symmetry of the magnetic ground state, and selects a particular ordered spin structure below TN=1.2 K. The removal of the continuous degeneracy results in an energy gap in the spectrum of spin wave excitations, long wavelength pseudo-Goldstone modes. We have measured the Order-by-Quantum-Disorder spin wave gap at a zone center in Er2Ti2O7, using low incident energy neutrons and the time-of-flight inelastic scattering method. We report a gap of Δ=0.053±0.006  meV, which is consistent with upper bounds placed on it from heat capacity measurements and roughly consistent with the theoretical estimate of ∼0.02  meV, further validating the spin Hamiltonian that led to that prediction. The gap is observed to vary with the square of the order parameter, and goes to zero for T∼TN.

What are you looking at? Moving toward an attentional timeline in insomnia: a novel semantic eye tracking study

STUDY OBJECTIVES

To date, cognitive probe paradigms have been used in different guises to obtain reaction time measurements suggestive of an attention bias towards sleep in insomnia. This study adopts a methodology which is novel to sleep research to obtain a continual record of where the eyes-and therefore attention-are being allocated with regard to sleep and neutral stimuli.

DESIGN

A head mounted eye tracker (Eyelink II,SR Research, Ontario, Canada) was used to monitor eye movements in respect to two words presented on a computer screen, with one word being a sleep positive, sleep negative, or neutral word above or below a second distracter pseudoword. Probability and reaction times were the outcome measures.

PARTICIPANTS

Sleep group classification was determined by screening interview and PSQI (> 8 = insomnia, < 3 = good sleeper) score.

MEASUREMENTS AND RESULTS

Those individuals with insomnia took longer to fixate on the target word and remained fixated for less time than the good sleep controls. Word saliency had an effect with longer first fixations on positive and negative sleep words in both sleep groups, with largest effect sizes seen with the insomnia group.

CONCLUSIONS

This overall delay in those with insomnia with regard to vigilance and maintaining attention on the target words moves away from previous attention bias work showing a bias towards sleep, particularly negative, stimuli but is suggestive of a neurocognitive deficit in line with recent research.

Thermal conductivity of Ho2Ti2O7 along the [111] direction

Thermal transport measurements have been made on the spin-ice material Ho(2)Ti(2)O(7) in an applied magnetic field with both the heat current and the field parallel to the [111] direction for temperatures from 50 mK to 1.2 K. A large magnetic field >6 T is applied to suppress the magnetic contribution to the thermal conductivity in order to extract the lattice conductivity. The low field thermal conductivity thus reveals a magnetic field dependent contribution to the conductivity which both transfers heat and scatters phonons. We interpret these magnetic excitations as monopolelike excitations and describe their behavior via existing Debye-Hückel theory.

Neutron Laue diffraction study on the magnetic phase diagram of multiferroic MnWO4 under pulsed high magnetic fields

We have combined time-of-flight neutron Laue diffraction and pulsed high magnetic fields at the Spallation Neutron Source to study the phase diagram of the multiferroic material MnWO(4). The control of the field-pulse timing enabled an exploration of magnetic Bragg scattering through the time dependence of both the neutron wavelength and the pulsed magnetic field. This allowed us to observe several magnetic Bragg peaks in different field-induced phases of MnWO(4) with a single instrument configuration. These phases were not previously amenable to neutron diffraction studies due to the large fields involved.

Neurocognitive sequelae in African American and Caucasian children with multiple sclerosis

OBJECTIVE

To examine domain-specific neurocognitive differences between African American (AA) and Caucasian (CA) patients with pediatric-onset multiple sclerosis (POMS).

METHODS

An extensive battery of neuropsychological tests was given to each subject, including tests in all major domains of cognitive function. Point-biserial correlations between ethnicity and test performance were computed. Significant correlations were followed up with hierarchical multiple regression analysis, accounting for clinical and demographic variables before examining ethnic differences.

RESULTS

Forty-two patients with POMS including 20 AA and 22 CA subjects were assessed. The cohorts did not differ in age, gender, socioeconomic status, disease duration, disability score, immunoglobulin G index, or number of relapses in the first 2 years of disease. Retaining some of these variables as covariates in the hierarchical regression analysis, the AA cohort performed worse on measures of language (p < 0.001) and complex attention (p < 0.01) than their CA peers.

CONCLUSION

AA patients with POMS may be at higher risk for adverse cognitive impact in the areas of language and complex attention. Longitudinal characterization of cognitive pathology is critical for the development of effective intervention strategies to prolong cognitive functioning in POMS cohorts.

Magnetoelastics of a spin liquid: X-ray diffraction studies of Tb2Ti2O7 in pulsed magnetic fields

We report high resolution single crystal x-ray diffraction measurements of the frustrated pyrochlore magnet Tb2Ti2O7, collected using a novel low temperature pulsed magnet system. This instrument allows characterization of structural degrees of freedom to temperatures as low as 4.4 K, and in applied magnetic fields as large as 30 T. We show that Tb2Ti2O7 manifests intriguing structural effects under the application of magnetic fields, including strongly anisotropic giant magnetostriction, a restoration of perfect pyrochlore symmetry in low magnetic fields, and ultimately a structural phase transition in high magnetic fields. It is suggested that the magnetoelastic coupling thus revealed plays a significant role in the spin liquid physics of Tb2Ti2O7 at low temperatures.

Two-dimensional kagome correlations and field induced order in the ferromagnetic XY pyrochlore Yb2Ti2O7

Neutron scattering measurements show the ferromagnetic XY pyrochlore Yb2Ti2O7 to display strong quasi-two-dimensional (2D) spin correlations at low temperature, which give way to long range order (LRO) under the application of modest magnetic fields. Rods of scattering along 111 directions due to these 2D spin correlations imply a magnetic decomposition of the cubic pyrochlore system into decoupled kagome planes. A magnetic field of approximately 0.5 T applied along the [110] direction induces a transition to a 3D LRO state characterized by long-lived, dispersive spin waves. Our measurements map out a complex low temperature-field phase diagram for this exotic pyrochlore magnet.

The effect of ractopamine supplementation at 5 ppm of swine finishing diets on growth performance, carcass composition and ultimate pork quality

Five hundred thirty-six finishing pigs were placed on experiment for an average of 26 d prior to slaughter, to determine the effects of 5 mg ractopamine hydrochloride (RAC) per kg of diet on growth performance, carcass composition and the eating quality of pork. Treatments included a control diet similar to a western Canadian commercial finishing diet and a treatment diet containing 5 mg RAC kg-1 with elevated amino acids, vitamins and minerals. The experiment started when average animal weight was 86 kg; pigs were marketed at an average liveweight of 118 kg. Two pigs were selected from each of 32 pens in week 4 of the experiment, for detailed carcass and meat quality evaluation, providing 16 pigs per gender per treatment. RAC-fed pigs reached market weight 4 d sooner (P < 0.05), grew 13 % faster (P < 0.05) and had 13% better feed efficiency (P < 0.05) than the controls. RAC-fed pigs also had 1 mm less backfat and 2.5 mm thicker loins (P < 0.05). Ultimate pH, purge loss and visual colour scores were unaffected by treatment but RAC-fed pigs had lower CIE a* and b* measurements (P < 0.05). RAC had no effect on juiciness, flavour, saltiness or overall acceptability (P > 0.10), but increased Warner-Bratzler shear force and reduced taste panel tenderness slightly (P < 0.05). The inclusion of 5 mg RAC kg-1 in a commercial finishing diet will increase the rate and efficiency of gain and improve carcass composition. Minimal impact on pork quality can also be expected with the use of RAC fed at this level. Key words: Ractopamine, swine, carcass composition, pork quality, beta-adrenergic agonist

Evidence for gapped spin-wave excitations in the frustrated Gd2Sn2O7 pyrochlore antiferromagnet from low-temperature specific heat measurements

We have measured the low-temperature specific heat of the geometrically frustrated pyrochlore Heisenberg antiferromagnet Gd2Sn2O7 in zero magnetic field. The specific heat is found to drop exponentially below approximately 350 mK. This provides evidence for a gapped spin-wave spectrum due to an anisotropy resulting from single-ion effects and long-range dipolar interactions. The data are well fitted by linear spin-wave theory, ruling out unconventional low-energy magnetic excitations in this system, and allowing a determination of the pertinent exchange interactions in this material.

Structural and Electronic Properties of Bis[2-(pyrazin-2-ylamino)-4-(pyridin-2-yl)thiazolato]iron(II) and Its Solvated Derivatives

The uncharged complex [Fe( pzapt )2] [ pzapt is the deprotonated form of 2-(pyrazin-2-ylamino)-4-(pyridin-2-yl) thiazole ] crystallizes with varying degrees of solvation , depending on the solvent. The electronic properties of the solvates differ. For all of them temperature dependence of the magnetic moment is observed, associated with a continuous temperature-induced singlet (1A1) ↔ quintet (5T2) transition. The transition is centred below room temperature for the benzene solvates but the unsolvated and chloroform solvate complexes exist predominantly in a singlet low-spin state. Overall the stabilization of the singlet state is greater in this system than in the previously studied [Fe( papt )2] [ paptH = 2-(pyridin-2-ylamino)-4-(pyridin-2-yl) thiazole ]. A spin equilibrium has been characterized for both [Fe( pzapt )2] and [Fe( papt )2] in methanol solution. The crystal structure of [Fe( pzapt )2].3/2C6H6 reveals Fe-N bond lengths consistent with both singlet and quintet state iron(II) being present. The benzene molecules are incorporated into the lattice as groups of three by occupying channels created by the packing of the complex molecules. Bis [2-(pyrazin-2-ylamino)-4-(pyridin-2-yl) thiazole ]iron(II) sesquibenzene solvate: monoclinic, space group P 21/c, a 14.894(7), b 12.601(2), c 16.777(8) Ǻ, β 94.57(2)°, Z 4.

Peptide growth factors elicit estrogen receptor-dependent transcriptional activation of an estrogen-responsive element

Epidermal growth factor (EGF) elicits estrogen receptor (ER)-dependent physiological sequelae and estrogen-like biochemical effects on the ER in the mouse uterus. These in vivo observations indicate that EGF may elicit some of its actions by activation of the ER. The effect of peptide growth factors on activation of a consensus estrogen-responsive element was assessed in a strain of Ishikawa human endometrial adenocarcinoma cells with negligible levels of ERs, as determined by Western blot and [3H]estradiol binding, and in BG-1 human ovarian adenocarcinoma cells, which contain abundant ERs. EGF and transforming growth factor-alpha induced transcriptional activation of a consensus ERE in an ER-dependent manner in both cell types. Transcriptional activation by the growth factors was inhibited by ICI 164,384, an ER receptor antagonist, and neutralizing antibodies to the EGF receptor. Immunodetection of the ER in BG-1 cells demonstrated that receptor levels were not induced by transforming growth factor-alpha vs. untreated cells. ER deletion mutants containing amino acids 1-339 and 121-599 were transfected into Ishikawa cells. The 1-339 mutant was more active in inducing transcription after EGF treatment than the 121-599 mutant. Estrogen only stimulated transcription in the presence of the 121-599 mutant, while 1-339 was inactive. Interestingly, synergism between a physiological dose of estrogen and peptide growth factors was observed. The presence of cross-talk between EGF receptor and ER signaling pathways suggests that interactions between growth factors and steroid receptors may modulate hormonal activity influencing normal and aberrant function in mammalian cells.

Lung growth in newborn guinea pigs: effects of endurance exercise

Newborn Hartley albino guinea pigs were exercised daily on a rodent treadmill at 25 m/min, 0 degree grade for a maximum of 1 1/2 h. Groups were exercised for 1, 2 and 3 weeks. Controls were age-matched sedentary animals. A separate group of animals was sacrificed after 12 h of life to establish baseline lung growth data. A morphological and biochemical comparison was made between the lungs of exercised and sedentary animals. No effect of exercise on lung growth was observed. After 2 weeks of exercise animals had diminished somatic growth compared to the controls. The data was pooled from exercised and control guinea pigs at 1 and 3 weeks, at which time there were no differences, in order to obtain normal growth data. The only change between 0 week and 1 week was a slight increase in femur length. Between 1 week (and also 0 week) and 3 weeks there were significant increases in lung volume, lung weight, protein content, inter-alveolar wall distance, mean chord length of alveoli and ducts, and gas exchanging surface area. The guinea pig lung is well alveolated at birth and there was no evidence of subsequent alveolar multiplication. Enlargement of airspaces suggested that lung growth was primarily brought about by dilation. The lack of alveolar multiplication following exercise may be due to the fact the alveoli are fully developed at birth.

Localization of the estrogen receptor in uterine cells by affinity labeling with [3H]tamoxifen aziridine

The possibility that estrogen receptors may exist in uterine plasma membranes was investigated by covalent labeling of estrogen receptors in mouse uterine cells with [3H]tamoxifen aziridine (TA). Isolated epithelial and stromal cells of immature mice were incubated with [3H]TA in the presence or absence of unlabeled tamoxifen, homogenized and separated into nuclear, cytosolic and microsomal fractions by differential centrifugation. These fractions were subjected to SDS-polyacrylamide gel electrophoresis and the proteins labeled covalently with TA were visualized by autoradiography. Proteins labeled specifically with [3H]TA were observed almost exclusively in the nuclear fraction of both epithelial and stromal cells. In contrast, very little labeled protein was detected in the cytosolic or microsomal fraction. Although these data do not preclude the possibility that estrogen binding sites are present in plasma membranes of uterine cells, this cellular fraction is definitely not labeled to a significant extent by [3H]TA. Thus, if membrane estrogen binding sites exist, their structural conformations may be different from that of nuclear estrogen receptors.

Epidermal growth factor binding and receptor distribution in the mouse reproductive tract during development

The ontogeny of the epidermal growth factor (EGF) receptor in the different cell types in the neonatal and immature mouse uterus and vagina was examined. Immunohistochemical examination of prenatal and neonatal reproductive tracts with a polyclonal antibody to the EGF receptor shows immunoreactive EGF receptors as early as Day 13 of gestation. Autoradiographic analysis of tissue sections at 3 to 17 days of age (the day of birth is Day 1) demonstrates that both uterine and vaginal epithelial and stromal cells are capable of binding 125I-labeled EGF. Both the 125I-labeled EGF autoradiography and immunohistochemistry in whole tissue show higher EGF receptor levels in the uterine epithelium than the uterine stroma. The presence of EGF receptors was also confirmed by affinity labeling and Scatchard analysis of isolated uterine cell types at 7 and/or 17 days of age. However, in contrast to the autoradiography and immunohistochemistry data of intact tissue, the affinity labeling and Scatchard data of isolated cells indicate that the uterine stroma contains higher levels of EGF receptor than that of the uterine epithelium. The reason for this discrepancy between the different techniques is, as yet, unknown. Regardless of the differences in the actual numbers of EGF receptors obtained, our data demonstrate that the developing mouse reproductive tract contains immunoreactive EGF receptors that are capable of binding 125I-labeled EGF.

Preoperative risk assessment in cardiac surgery: comparison of predicted and observed results

In the present climate of quality-assurance policies, rigorous requirements for informed consent, and a constantly changing patient population, a system of preoperative risk assignment and postoperative correlation was developed to monitor and evaluate surgical performance. Patients were categorized by operation, priority (emergent, urgent, elective), New York Heart Association Functional Class, and risk. Risk was assigned before operation using data from the Coronary Artery Surgery Study (CASS) and the recent literature. Data were collected by a full-time data manager and were stored and analyzed by computer. From January 1, 1984, to July 1, 1985, 1,303 patients underwent operation for acquired disease. This group included 913 patients undergoing isolated primary coronary artery bypass grafting (CABG). The comparison of predicted and observed results showed: (Table: see text). For patients undergoing isolated primary CABG, the elective group had an operative mortality of 0.6% (2/329); the urgent group, 1.1% (5/450); and the emergent group, 5.2% (7/134). Preoperative risk assignment is an effective method of quality assurance. Female sex and age older than 60 years, which predicted an operative mortality of 2 to 5% in the CASS study and other recent series, did not predict a similar risk in our series.

Sepsis due to triple lumen central venous catheters

We prospectively studied 96 consecutive catheterizations in 65 patients who required triple lumen central venous catheters. The incidence of catheter associated bacteremia was 3.1 per cent. Staphylococcus epidermidis was the organism involved in all instances.

Performance of the Smeloff aortic valve beyond ten years

The Smeloff aortic valve has remained unchanged in design and material since 1966. To assess the long-term performance of this prosthesis, we reviewed 394 consecutive patients undergoing elective aortic valve replacement. Concomitant coronary artery bypass grafting was performed in 26.4% of these patients. Follow-up was complete in 96%; maximum follow-up was 13.1 years (mean 4.3 years). The operative mortality was 7.4%. Actuarial survival rate, including operative mortality, was 66.3% +/- 2.8% at 5 years and 48.7% +/- 4.5% at 10 years. Thromboembolism for the entire group occurred at a rate of 3.8% per patient-year. Patients who underwent anticoagulation continuously had a rate of embolision of 1.8% per patient-year. All patients had a 5 year embolus-free rate of 91% +/- 2% and a 10 year embolus-free rate of 85% +/- 3%. Patients receiving anticoagulants had a 5 year embolus-free rate of 92% +/- 2% and a 10 year embolus-free rate of 89% +/- 3%. There was no mechanical failure or prosthetic thrombosis in 1,690 patient-years of follow-up. The Smeloff aortic valve has excellent long-term durability and thromboembolism is low in patients receiving anticoagulants.

A program for infection surveillance utilizing an infection control liaison nurse

Today's infection control programs require a practical, efficient, and effective surveillance system. The Epidemiology Section of a 650-bed, university-affiliated hospital has implemented a two-phase approach. Phase I is surveillance by service. Each service receives a minimum of 2 months' concentrated surveillance, with critical care units monitored each month. The entire hospital is covered within a year. Monthly statistics are issued for each surveyed service and the individual patient units within that service. Phase II involves the infection control liaison nurse (ICLN). An ICLN, established in each patient unit, monitors infection control practices and acts as a liaison between the unit and the epidemiology section. Selected candidates are trained by the epidemiology section. The ICLN aids in more immediate identification of problems and better monitoring of aseptic practices. This approach is effective and manageable. Better understanding of unit problems result in more relevant educational programs with time to conduct additional activities. Statistics have more meaning and support for infection control is improved.

An epidemic of resistant Salmonella in a nursery. Animal-to-human spread

A Salmonella heidelberg epidemic in a hospital nursery was traced to infected calves on a dairy farm where the mother of the index patient lived. The Salmonella isolates from all cases were resistant to chloramphenicol, sulfamethoxazole, and tetracycline. Verification of the spread of infection from the farm animals to a hospital population is unusual and raises questions about the hazards of antibiotic animal-feed preparations that may induce infection with resistant organisms in humans.

Lacunarity for compact groups

Let G be a compact Abelian group with character group X. A subset Delta of X is called a [unk](q) set (1 < q < infinity) if for all trigonometric polynomials f = [unk](k=1) (n) alpha(k)chi(k) (chi(1),...,chi(n) [unk] Delta) an inequality parallelf parallel(q) [unk] [unk] parallelf parallel(1) obtains, where [unk] is a positive constant depending only on Delta. The subset Delta is called a Sidon set if every bounded function on Delta can be matched by a Fourier-Stieltjes transform. It is known that every Sidon set is a [unk](q) set for all q. For G = T, X = Z, Rudin (J. Math. Mech., 9, 203 (1960)) has found a set that is [unk](q) for all q but not Sidon. We extend this result to all infinite compact Abelian groups G: the character group X contains a subset Delta that is [unk](q) for all q, 1 < q < infinity, but Delta is not a Sidon set.