Absence Of CS Research Articles

A 10-year cohort on prognostic outcomes in patients presenting with acute myocardial infarction complicated by cardiogenic shock and/or cardiac arrest

Abstract Background Cardiogenic shock (CS) and cardiac arrest (CA) complicating acute myocardial infarction (AMI) portend unfavourable outcomes. This study examined the prognosis of patients presenting with AMI complicated by CS and/or CA. Methods Consecutive patients presented with AMI to a percutaneous coronary intervention-capable tertiary institution between 2011 and 2021 were studied. Patients were stratified based on the presence or absence of CS (CS+ or CS−) and CA (CA+ or CA−). The primary outcome was 30-day cardiovascular-related mortality. Subgroup analyses based on AMI-type and sex were conducted. Kaplan-Meier curves for cardiovascular-related mortality based on the AMI-type and sex were constructed. Results The study included 11,608 AMI patients, 283 of whom had CS+/CA+, 1,068 had CS+/CA−, 54 had CS−/CA+ and 10,203 had CS−/CA−. Cardiovascular-related mortality was significantly higher for CS+/CA+ (57.6%), followed by CS+/CA− (41.6%), CS−/CA+ (20.4%) and CS−/CA− (2.4%). Kaplan-Meier curves demonstrated CS+/CA+ group had the highest mortality (HR=36.26; 95% CI: 29.71–44.25, p<0.001), followed by CS+/CA− (HR=21.59; 95% CI: 18.47–25.24, p<0.001) and CS−/CA+ (HR=9.18; 95% CI: 5.02–16.80, p<0.001), with CS−/CA− as the reference. Those with NSTEMI had consistently higher cardiovascular-related mortality rates than their STEMI counterparts for all groups, apart from the CS+/CA+ group. The sex-specific analysis demonstrated that the survival curves for females with CS+/CA+, CS+/CA− and CS−/CA+ converged, whilst the survival curves for males diverged over time. The multivariable Cox regression revealed the presence of CS and CA are independent predictors of cardiovascular-related mortality, but not NSTEMI, when adjusted for age, gender, diabetes, left ventricular ejection fraction, chronic renal failure, and culprit vessel. Conclusions AMI associated with CA and CS portends the least favourable survival, followed by those with CS or CA alone. Excess mortality was observed in the traditionally perceived lower-risk groups, particularly in women. This calls for increased awareness amongst clinicians when managing this subset of high-risk patients. Funding Acknowledgement Type of funding sources: None.

Predicting the mandibular growth spurt.

To develop a prediction model that combined information derived from chronological age, sex, and the cervical vertebral maturation (CVM) method to predict the pubertal spurt in mandibular growth. A total of 50 subjects (29 females, 21 males) were selected from the American Association of Orthodontists Foundation Craniofacial Growth Legacy Collection, the University of Michigan Growth Study, and the Denver Child Growth study. A total of 456 lateral cephalograms were analyzed, and a multilevel logistic model was applied. The outcome variable was the presence or absence of the mandibular pubertal growth peak. The predictive variables were chronological age up to the third order, sex, presence or absence of CS 3 interactions between age and sex, age and CS 3, sex and CS 3. The mean age ± standard deviation (SD) at the first cephalogram was 8.2 ± 0.5 years, whereas the mean age at the last cephalogram was 16.5 ± 1.1 years. The mean interval ± SD between two consecutive cephalograms was 1.0 ± 0.1 years. The mean age ± SD at the lateral cephalogram obtained immediately before the mandibular pubertal growth peak was 12.1 ± 1.1 years for females and 13.2 ± 0.8 years for males. The greatest increase in mandibular length occurred after CS 3 in 78% of the subjects. The presence of CS 3, age, second-order age, sex, and the interaction between age and sex were all statistically significant predictors of the mandibular pubertal growth spurt. CS 3, chronological age, and sex can be used jointly to predict the pubertal peak in mandibular growth.

Cases of Eastern equine encephalitis in humans associated with Aedes canadensis, Coquillettidia perturbans and Culiseta melanura mosquitoes with the virus in New York State from 1971 to 2012 by analysis of aggregated published data.

From 1971 to 2012, in New York State, years with human Eastern equine encephalitis (EEE) were more strongly associated with the presence of Aedes canadensis, Coquillettidia perturbans and Culiseta melanura mosquitoes infected with the EEE virus (Fisher's exact test, one-sided P = 0.005, 0.03, 0.03) than with Culiseta morsitans, Aedes vexans, Culex pipiens-restuans, Anopheles quadrimaculatus or Anopheles punctipennis (P = 0.05, 0.40, 0.33, 1.00, 1.00). The estimated relative risk of a case in a year in which the virus was detected vs. not detected was 14.67 for Ae. canadensis, 6.38 for Cq. perturbans and 5.50 for Cs. morsitans. In all 5 years with a case, Cs. melanura with the virus was detected. In no year was there a case in the absence of Cs. melanura with the virus. There were 18 years with no case in the presence of Cs. melanura with the virus. Such observations may identify the time of increased risk, and when the methods may be used to prevent or reduce exposure to vector mosquito species in this geographic region.

Features of climacteric syndrome in women with endometriosis

Share of patients with endometriosis among women of perimenopausal age is about 50% thus the problem of climacteric syndrome (СS) is extremely actual. The processes of maladaptation of neurocircular regulation are observed at reproductive age especially in this category of women. Considering the above-mentioned, research of the CS`s run of the disease; against the background of endometriosis and the choice of the correct tactics of the management of such patients becomes extremally crucial. The article deals with issues of identification of the frequency of CS in patients with endometriosis and features of development of the disease.The exanimated group of patients consisted of 1055 women of late reproductive and perimenopausal women (from 39 to 55 years), 520 of them had diagnosis endometriosis (control group) and 535 without endometriosis(comparison group). At the next stage were examined 323 women: 170 with endometriosis and 153 without this pathology, which were divided into groups depending on the presence or absence of CS’s symptoms. Also were searched four electronic databases.During the analysis of groups of patients were studied, it was found that the incidence of CS in group of women with endometriosis was significantly higher (p <0.05) than in the comparison group, with manifestations of the CS earlier than in women of the general population. Were found the following risk factors for the development of a climacteric syndrome against the backdrop of endometriosis: psychical and intellectual overload, the presence of chronic stressful situations, adverse environmental conditions of living and harmful factors of labor, menstrual disorders in reproductive age, especially abnormal uterine bleeding, premenstrual syndrome, three or more abortions, the absence of birth in the history, the presence of postoperative surgical interventions in reproductive age, as well as significant somatic burdened anamnesis.Given the results of the study, it can be argued that the CS is the psycho-emotional and vegetative crisis which in combination with severe premorbid background – endometriosis, significantly increases the impact on the general condition of both physical and mental health, including social activity and quality of life than the development of an independent disease. This determines the relevance of the study of the possibilities of using therapeutic and preventive measures not only for the safe correction of menopausal disorders, but also to relief the severity of the symptoms of endometriosis.

Gold diffusion into and out of quartz-hosted fluid inclusions during re-equilibration experiments at 600–800 °C and 2 kbar

Fluid inclusions were synthesized in quartz and subsequently re-equilibrated in fluids of different compositions to investigate whether the Au content of fluid inclusions can be modified via Au diffusion through the host quartz. In one experiment fluid inclusions containing 5wt% KCl were synthesized in platinum capsules at 2kbar, 800°C and then re-equilibrated at the same conditions for 4days in a fluid containing 20.1wt% NaCl, 3.5wt% HCl and ~100ppm Cs enclosed in a gold capsule. LA-ICP-MS analyses of 5–10 fluid inclusions before and after the re-equilibration experiment demonstrate that the inclusions gained up to 570ppm Au and up to 0.23wt% Na during the re-equilibration process. Their unchanged high K-content and the absence of Cs within the inclusions proves that they remained physically closed during the re-equilibration, and thus that Na and Au were gained by diffusion through the quartz lattice. In a similar experiment conducted at 600°C the fluid inclusions gained up to 140ppm Au within 14days. Reverse experiments were conducted by synthesizing Au-bearing fluid inclusions in gold capsules and then re-equilibrating them in platinum capsules, which caused the inclusions to lose up to several hundred ppm Au. In both type of experiments Au diffusion appears to have been driven by chemical potential gradients of Au between the fluid inclusions and the external fluid. Additional experiments were performed to test whether Au is able to diffuse into fluid inclusions in response to loss of H+, or indirectly as a consequence of diffusional Cu-gain and corresponding formation of Cu-rich sulfide daughter crystals. However no evidence for Au uptake via such mechanisms was found.If Au concentrations in natural, quartz-hosted fluid inclusions from magmatic-hydrothermal ore deposits are affected, then they likely lost Au rather than gained it. At temperatures below 400°C diffusional loss or gain of Au is considered unlikely in magmatic-hydrothermal systems, but potentially was significant in samples from orogenic Au gold deposits.

Assessment of the bioavailability and depuration of uranium, cesium and thorium in snails (Cantareus aspersus) using kinetics models

Uranium ore waste has led to soil contamination that may affect both environmental and soil health. To analyze the risk of metal transfer, metal bioavailability must be estimated by measuring biological parameters. Kinetic studies allow taking into account the dynamic mechanisms of bioavailability, as well as the steady state concentration in organisms necessary to take into account for relevant risk assessment. In this way, this work aims to model the snail accumulation and excretion kinetics of uranium (U), cesium (Cs) and thorium (Th). Results indicate an absence of Cs and Th accumulation showing the low bioavailability of these two elements and a strong uranium accumulation in snails related to the levels of soil contamination. During the depuration phase, most of the uranium ingested was excreted by the snails. After removing the source of uranium by soil remediation, continued snails excretion of accumulated uranium would lead to the return of their initial internal concentration, thus the potential trophic transfer of this hazardous element would stop.

Involvement of Hippocampal Inputs and Intrinsic Circuit in the Acquisition of Context and Cues During Classical Conditioning in Behaving Rabbits

Learning-related changes in strength in selected hippocampal synapses have been described recently. However, information is scarce regarding the spatial-temporal sequence of changes in synaptic weights taking place during the acquisition of a classical conditioning task and the contribution of both context (environmental details) and cues (conditioned and unconditioned stimuli: CS, US) to those activity-dependent changes. We recorded in rabbits the monosynaptic field excitatory postsynaptic potentials (fEPSPs) evoked at 6 different hippocampal synapses during the acquisition and extinction of a classical eyeblink conditioning using trace or delay paradigms, as well as during pseudoconditioning and in the absence of CS and US presentations (context). Context and pseudoconditioning training evoked early, lasting changes in synaptic strength in perforant pathway synapses in dentate gyrus (PP-DG), and hippocampal CA3 (PP-CA3) and CA1 (PP-CA1) areas. Pseudoconditioning also evoked early, nonlasting changes in strength within the intrinsic hippocampal circuit (CA3-CA1 and CA3-cCA1 synapses). In contrast, during both trace and delay training sessions, synaptic changes in strength were mostly noticed within the intrinsic hippocampal circuit (DG-CA3, CA3-CA1, CA3-cCA1). The response of hippocampal synapses to afferent impulses seems to be modulated by both context and cues during associative learning in behaving rabbits.

Effect of Cs + ions on the electrochemical nanogravimetric response of platinum electrode in acid media

Platinum electrodes have been investigated in sulfuric acid solutions in the presence and absence of Cs + ions by electrochemical quartz crystal nanobalance (EQCN). An unusual potential dependence of the quartz crystal frequency response has been observed in the presence of Cs + ions. The frequency decrease is more pronounced in the region of the underpotential deposition of hydrogen, and the frequency decrease in the double layer region diminishes as the concentration ratio of Cs + and H + ions increases. After immersion in Cs 2SO 4 solutions the frequency change was higher than that expected taking into account the density and viscosity. The effects observed can be explained by the specific adsorption of Cs + ions on the Pt surface, which competes with the hydrogen adsorption. At more positive potentials than the potential of zero charge (pzc) a desorption of the Cs + ions starts. In this potential region both Cs + and HSO 4 − ions are adsorbed at the platinum surface. In the double layer region the mass change caused by the desorption of Cs + ions and the starting adsorption of sulfate ions compensates each other.

Inwardly rectifying K+ (Kir) channels antagonize ictal‐like epileptiform activity in area CA1 of the rat hippocampus

Reactive glial cells, for example, from patients with temporal lope epilepsy have a reduced density of inward rectifying K(+) (Kir) channels and thus a reduced K(+) buffering capacity. Evidence is accumulating that this downregulation of Kir channels could be implicated in epileptogenesis. In rat hippocampal brain slices, prolonged exposure to the nonselective Kir channel antagonist, Cs(+) (5 mM), gives rise to an epileptiform field potential (Cs-FP) in area CA1 composed of an initial positive (interictal-like) phase followed by a prolonged negative (ictal-like) phase. We have previously shown that the interictal-like phase depends on synaptic activation. The present study extends these findings by showing that the ictal-like phase of the Cs-FP is (i) sensitive to osmotic expansion of the extracellular space, (ii) reversed very quickly during wash out of Cs(+), and (iii) re-established in the presence of Ba(2+) (30-200 microM) or isosmotic low extracellular concentration of Na(+) ([Na(+)](o), 51.25 mM). The interictal-like phase showed less or no sensitivity to these treatments. In the complete absence of Cs(+), the Cs-FP could be fully reconstructed by the combined application of 4-aminopyridine (0.5 mM), an isosmotic high extracellular concentration of K(+) ([K(+)](o), 7 mM), and low [Na(+)](o) (51.25 mM). These results suggest that the interictal-like phase is initiated through synaptic activation and results from an unspecific increase in neuronal excitability, whereas the ictal-like phase is entirely dependent on blockade of Kir channels in CA1. We propose that glial dysfunction-related loss of Kir channels may not alone be sufficient for starting the induction process, but will likely increase the tendency of an epileptogenic process to proceed into seizure activity.

Cs+ and Ba2+ Selective Transport by a Novel Self-Assembled Isoguanosine Ionophore Through Polymer Inclusion and Bulk Liquid Membranes

5'-(Tert-butyldimethylsilyl)-2',3'-O-isopropylidene isoguanosine(isoG 1) serves as a selective Cs+ carrier in liquid membrane transport. IsoG~1 is a lipophilic nucleoside that self-assembles via hydrogen bonds and cation-dipole interactions to form a stable decamer sandwich complex with Cs+. Using an acidic receiving phase, Cs+ transport through polymer inclusion membranes (PIMs) was observed at concentrations of isoG 1 below 21 mM. When isoG 1 was precomplexed with Cs+ to give the (isoG 1)10-Cs+decamer, flux was observed above 21 mM carrier. The Cs+ flux increased with increasing carrier concentration of the precomplexed (isoG 1)10-Cs+ decamer. The Cs+ transport selectivity by isoG 1 was investigated in the presence of sodium salt solutions of high concentration. Excellent Cs+ flux and selectivity over the other alkali metal cations was observed in PIMs and bulk liquid membranes (BLMs). In the absence of Cs+, this ionophore exhibitsgood Ba2+ selectivity in BLMs.

Prevention of acute rejection with antithymocyte globulin, avoiding corticosteroids, and delaying cyclosporin after renal transplantation.

Despite their well-known side-effects, corticosteroids (Cs) are currently used after kidney transplantation. Avoidance of Cs may improve patient quality of life and eventual long-term survival. We report on a regimen using antithymocyte globulin (ATG) and mycophenolate mofetil (MMF) for induction, and cyclosporin (CsA) plus MMF for maintenance treatment of recipients of primary kidney transplantation. We studied 11 consecutive, non-sensitized renal transplant patients (nine cadaver and two living donors). Initial immunosuppression consisted of ATG (1.5 mg/kg/day, i.v.) given for 10 days and MMF (1.0 g/b.i.d.). CsA (8 mg/kg, in two divided doses) was started on post-operative day 11. Cs were only allowed in the case of MMF discontinuation, for the treatment of acute rejection, and in the event of recurrence of the primary glomerulonephritis. All patients completed the entire 10-day ATG course. Main side-effects included fever (>38 degrees C) and serum sickness, observed in 73 and 27% of the patients respectively. The incidence of acute rejection was 27% (three of 11 patients). In two patients with acute rejection, serum sickness was concomitantly diagnosed and renal histology was partially compatible with immune-complex disease. The remaining patient had two episodes of low-grade rejection. All rejection episodes were rapidly reversed. Two patients (18%) were treated with ganciclovir for cytomegalovirus (CMV) infection. Two patients (18%) are currently receiving Cs for recurrence of the native glomerulonephritis and two rejection episodes respectively. All patients are currently alive with functioning kidneys (average follow-up of 8.4 months; average creatinine level of 128 micromol/l). This pilot study suggests that ATG induction in combination with MMF and delayed introduction of CsA, in the absence of Cs, is not well tolerated in recipients of kidney transplants. An earlier introduction of calcineurin inhibitors and/or a shorter course of ATG may reduce the incidence of fever and serum sickness secondary to ATG.

High bovine blastocyst development in a static in vitro production system using sofaa medium supplemented with sodium citrate and myo-inositol with or without serum-proteins

We describe a bovine embryo culture system that supports repeatable high development in the presence of serum or BSA as well as under defined conditions in the absence of those components. In the first experiment, embryo development in SOF with amino acids (SOFaa), sodium citrate (SOFaac) and myo-inositol (SOFaaci) and with BSA or polyvinyl alcohol (PVA) was compared with that in a M199 granulosa cell co-culture (M199 co-culture). Subsequently, development and cell numbers of blastocysts cultured under defined conditions in SOFaaci with PVA (SOFaaci-PVA), or under undefined conditions in SOFaaci with 5% cow serum (SOFaaciCS) or M199 co-culture were compared. The repeatability of culture results in SOFaaci-CS was checked by weekly replicates (n = 30) spread over 11 months. The viability of embryos developed in SOFaaci-PVA was estimated by transfer of morphologically good blastocysts (n = 10) to synchronized recipients. In the second experiment, the effect of omitting CS or BSA from IVM and IVM-IVF on subsequent embryo development in SOFaaci-PVA or in SOFaaci-CS was investigated. Blastocyst development in SOFaa-PVA, SOFaac-PVA, SOFaa-BSA and M199 was 16 ± 3, 23 ± 2 ab, 30 ± 8 a and 36 ± 7 a%, respectively (P ab < 0.05). Additional inclusion of myoinositol resulted in 42 ± 1 a% blastocysts in SOFaaci-PVA vs 19 ± 3 b% in SOFaac-PVA, 47 ± 7 a% in SOFaac-BSA, and 36 ± 7 a% in M199 co-culture, respectively (P ab < 0.01). In 30 replicates, the average cleavage and blastocyst rates of oocytes in SOFaaci-CS were 87 ± 4 and 49 ± 5%, respectively. Five normal calves were produced after transfer of 10 blastocysts developed in defined culture medium (i.e., SOFaaci-PVA). Defined IVM or IVM-IVF (i.e., in absence of CS and BSA) reduced cleavage rates (83 ± 3 and 55 ± 3% vs 90 ± 1% in presence of CS; P < 0.01). Subsequent embryo development in SOFaaci-CS was not affected in either of these defined conditions. However, cleavage and blastocyst rates under completely defined IVP conditions were 54 ± 7 and 19 ± 4%, respectively. It was concluded that under defined culture conditions, addition of citrate and myo-inositol improved blastocyst development to rates comparable to those obtained with serum, BSA or co-culture and that the quality of blastocysts was not affected by the absence of serum or BSA. However, serum was essential during IVM/IVF for normal fertilization and subsequent high blastocyst development.

Use-dependent block of Ih in mouse dorsal root ganglion neurons by sinus node inhibitors.

1. The sinus node inhibitors UL FS 49 and DK-AH 269 reduce heart rate by slowing diastolic depolarization rate in the sino-atrial (SA) node, which might originate from the use-dependent blockade of a hyperpolarization-activated current If. A hyperpolarization-activated current Ih, which is present in many types of neurons, is similar to If. We studied the effects of these drugs on Ih in cultured mouse dorsal root ganglion (DRG) neurons. 2. With the whole-cell patch-clamp technique use-dependent block of Ih was observed. The steady-state block following a voltage-clamp pulse train (1-s steps from -38 to -108 mV applied at 0.5 Hz) was dependent on drug concentration and showed an apparent Kd of 0.1 and 0.79 microM with DK AH 269 and UL-FS 49 respectively. 3. The rate of block increased linearly with drug concentration. The rate of recovery from block was, however, much slower compared to cardiac tissue. 4. There was no significant effect of UL-FS 49 on the activation curve. 5. At high concentrations of UL-FS 49 a clear association of the drug with the open channel was observed. 6. When the cell was stimulated at a frequency of 3 Hz, a distinct hyperpolarization was observed in the presence of extracellular Cs+ or when Ih was blocked with UL-FS 49, but not in the absence of Cs+ and UL-FS 49. 7. These results indicate that Ih protects the cell against hyperpolarizations and subsequent inexcitability. The action of the drugs on the hyperpolarization-activated current in cardiac and neuronal tissue show some similarities; however, some pronounced differences indicate that different subtypes of the channel might exist.

Contextual learning and cue association in fear conditioning in mice: a strain comparison and a lesion study

Fear conditioning with electric shock (unconditioned stimulus, US) paired with tone cue (conditioned stimulus, CS) has been extensively applied in recent molecular neurobiological analysis of hippocampal dysfunction in mice because the context-dependent test phase of this learning paradigm is claimed to detect hippocampal impairment in a specific manner, whereas the cue-dependent test serves as a control situation independent of hippocampal function. These claims are based on hippocampal lesion studies performed with rats and have not been conclusively confirmed with mice with specific hippocampal lesion. Therefore, I investigated how hippocampal ibotenic acid lesion affects conditioned fear in mice. I confirm that extensive lesions localized to the hippocampus impair context-dependent learning but also show that, unlike in the original rat studies, the behavioral impairment is only partial. Furthermore, studying two inbred strains of mice (C57BL/6 and DBA/2) with highly different hippocampal function, I show that the presence or absence of CS during training may influence the mouse's ability to learn complex multiple contextual stimuli in a genotype-dependent manner. I conclude that performance at the `context' test may be based on complex configural (hippocampal) learning but it can also be based on a more simple elemental (non-hippocampal) learning thus leading to potentially false-negative findings in the analysis of hippocampal dysfunction.

Syntheses and X-ray Powder Structures of K(2)(ZrSi(3)O(9)).H(2)O and Its Ion-Exchanged Phases with Na and Cs.

A zirconium trisilicate compound, with composition K(2)ZrSi(3)O(9).H(2)O (1), was prepared under mild hydrothermal conditions and was structurally characterized by using its X-ray powder diffraction data. The compound crystallizes in the space group P2(1)2(1)2(1) with a = 10.2977(2) Å, b = 13.3207(3) Å, c = 7.1956(1) Å, and Z = 4. The asymmetric unit consists of a metal atom, a trisilicate group, and three lattice positions corresponding to two cations and a water oxygen atom. In the structure, the Zr atom is octahedrally coordinated by the six terminal oxygens of the trisilicate group. The trisilicate groups exist as linear chain polymers connected to each other through the Zr atoms. This arrangement leads to channels and cavities in the structure that are occupied by the cations and water molecules. The K(+) ions in compound 1 were exchanged for Cs(+) ions in two steps. In the first case about 50% of the K(+) ions were exchanged to give a compound with composition K(0.9)Cs(1.1)ZrSi(3)O(9).H(2)O (2). Compound 2 was then loaded with additional Cs(+) ions which resulted in a phase K(0.5)Cs(1.5)ZrSi(3)O(9).H(2)O (3). These exchanged phases retain the crystal symmetry of compound 1, but their unit cell dimensions have expanded as a result of large Cs(+) ions replacing the smaller K(+) ions. Structure analyses of the exchanged phases show that the cations found in the cavities of compound 1 are highly selective for Cs(+) ions. A small amount of Cs ions also go to a site in the large channel that is very close to that occupied by the water oxygen in compound 1. In the absence of Cs, this site is filled with water molecules. The second cation found in the channel of 1 is partially occupied by water and K(+) ions. The K(+) ions in compound 1 were completely exchanged for Na(+) ions, and the compound thus obtained, Na(2)ZrSi(3)O(9).H(2)O (4), was treated with Cs(+) ions in a manner similar to that carried out for compound 1. The low Cs(+) ion phase, Na(0.98)Cs(1.02)ZrSi(3)O(9).H(2)O (5), and the high Cs(+) ion phase, Na(0.6)Cs(1.4)ZrSi(3)O(9).H(2)O (6), show ion distributions very similar to compounds 2 and 3 except for the fact that in the Na phases a small amount Cs(+) ion also goes to the second cation site. Compound 1 on heating releases the lattice water and transforms into a hexagonal phase, K(2)ZrSi(3)O(9), corresponding to the mineral wadeite. In the high-temperature phase the silicate group exists as a condensed cyclic group and the K(+) ions are sandwiched between trisilicate groups. A possible pathway for this conversion is also discussed.

Transient and sustained depolarization of retinal ganglion cells by Ih.

1. Using whole cell patch-clamp methods, we have identified an inward cationic current activated by hyperpolarization (Ih) in somata of goldfish retinal ganglion cells. 2. Ih activated at test potentials between -70 and -105 mV, and did not appear to inactivate during prolonged hyperpolarizations under voltage clamp. During step hyperpolarizations from holding potentials between -70 and -40 mV, apparent activation was faster at more negative test potentials. On repolarization from -105 mV to holding potentials between -75 and -55 mV, Ih deactivated exponentially at rates showing no marked voltage dependence (tau = approximately 100 ms). 3. Ih tail currents reversed at membrane potentials consistent with a relative permeability to Na+ and K+ of roughly 0.5, when pipette and bath solutions both contained Na+ and K+. 4. Ih was readily blocked by extracellular Cs+ (3 mM), but was resistant to block by tetraethylammonium (30 mM), Ba2+ (1 mM), or Co2+ (2.4 mM). 5. Time-dependent voltage rectification developed during injection of hyperpolarizing current under current clamp. After current injection ceased, membrane potential depolarized beyond resting potential, often leading to anode-break-like spikes. Both voltage rectification and voltage overshoot were suppressed by extracellular Cs+. 6. Voltage-clamp measurements in the presence and absence of Cs+ were used to model membrane potential changes produced by exogenous current injections, by hyperpolarizing synaptic inputs, and by termination of both. Modeled responses resembled membrane potential changes measured under current clamp when terms for activation and deactivation of Ih were included. 7. The voltage rectification and anode-break-like spikes observed in isolated cells resemble those recorded during and after light-evoked hyperpolarizations of retinal ganglion cells in situ. Ih may transiently augment retinal ganglion cell excitability after termination of hyperpolarizing light stimuli, and thus promote encoding of stimulus timing.

Oxidation of Cesium-Modified Graphite Supported on a Ru(001) Surface

The oxidation of Cs-modified graphite supported on a Ru(001) surface has been investigated by thermal desorption spectroscopy (TDS) and X-ray photoelectron spectroscopy (XPS). The major oxidation products are CO and CO[sub 2] with a product ratio of about 2:1; in contrast, for the nonmodified case, the oxidation of graphite leads only to the formation of CO. XPS results of oxygen adsorbed on a cesium-covered graphitic surface indicate the presence of Cs peroxide and Cs superoxide with Cs peroxide being the most thermally stable species. Oxygen released from Cs peroxide decomposition at elevated temperature enhances the oxidation of graphite and leads to an unusually narrow CO desorption feature, while the graphite oxidation in the absence of Cs is characterized by a broad CO desorption feature. The experiments demonstrate that Cs modification leads to both activity and selectivity changes in the oxidation of surface graphite. We observe a faster carbon removal and also the new reaction pathway: CO[sub 2] formation. 41 refs., 6 figs.

Replacement of cellular potassium by caesium in Chlorella emersonii: differential sensitivity of photoautotrophic and chemoheterotrophic growth

Summary: Photoautotrophic growth of Chlorella emersonii in the presence of 1 mM-CsCl resulted in a 34% increase in cell doubling time and an 83% reduction in the final cell yield as compared to growth in the absence of Cs+. In contrast, the presence of 1 mM-Cs+ had no effect on chemoheterotrophic growth in the dark with glucose. These observations were correlated with the stage of growth at which Cs+-induced cellular K+ loss was evident. For photoautotrophically growing cells this occurred during the exponential growth phase (after 4 d); for chemoheterotrophically growing cells this was during stationary phase (after 10 d). Inhibition of chemoheterotrophic cell division occurred after 2 d in 50 mM-Cs+ or 5 d in 20 mM-Cs+, and coincided with a decline in intracellular K+ to ∼2 nmol (106 cells)−1. Accumulation of Cs+ ceased after 2 d in both of these cases. Cell doubling times during chemoheterotrophic growth remained approximately constant at internal K+ levels between 7 and 28 nmol (106 cells)−1. In contrast, a decline in intracellular K+, from 42 to 19 nmol (106 cells)−1, after 4 d photoautotrophic growth in the presence of Cs+, was concurrent with the 34% increase in cell doubling times. Photosynthesizing cells accumulated approximately 2-fold more Cs+ than respiring cells after incubation for 12 h in HEPES buffer, pH 8. Culture age and intracellular K+ levels had little effect on the ability of C. emersonii to accumulate Cs+. Externally supplied K+ inhibited Cs+ accumulation to a greater extent in photosynthesizing cells (75% inhibition at 10 mM- K+, 1 mM-Cs+) than in respiring cells (50% inhibition at 10 mM-K+, 1 mM-Cs+). Greatly elevated Na+ light in the absence and presence of 10 mM-Cs+ accumulation in both cases. Incubation of cells in buffer in the light in the absence and presence of 10 mM-Cs+ resulted in decreases in cellular K+ of 44% and 77% respectively and a concomitant 66% reduction in the rate of photosynthesis in both cases. A Cs+-induced K+ loss of 71% from respiring cells had no effect on the rate of respiration. These results indicate that it is not the presence of Cs+ in cells that is growth inhibitory, but rather the resulting loss of K+ and that photosynthesis and photoautotrophic growth are more sensitive to this K+ loss than respiration and chemoheterotrophic growth.

The chemisorption and coadsorption of water and oxygen on Cs-dosed Cu(110)

The adsorption of H 2O and the coadsorption of oxygen and H 2O on Cu(110) containing overlayers of Cs have been studied with thermal desorption mass spectroscopy (TDS), X-ray photoelectron spectroscopy, Auger electron spectroscopy, and work function measurements. On clean Cu(110), H 2O adsorbs at 110 K and desorbs intact at 175 K, with no measurable dissociation probability (< 0.5%). In the presence of Cs a, the heat of adsorption of H 2O is increased by ∼ 50%, and the cleavage of OH bonds during TDS becomes highly probable when θ Cs * exceeds ∼ 0.5 monolayers (i.e., the work-function minimum). In this case, hydrogen adatoms are produced which associatively desorb as H 2 at ∼ 440 K (or ∼ 200 K for Cs multilayers). In addition, a CsOH a species is produced which decomposes at ∼ 510 K., probably via the evolution of gaseous (CsOH) 2 dimers. When Cs a and O a are both present on the surface, the cleavage of OH bonds to produce surface hydroxyl species proceeds already at 110 K, considerably colder than in the presence of either Cs a or O a alone. In addition, Cs a allows the production of approximately twice as much OH a than with O a alone. This OH a desorbs as H 2O at ∼ 350–420 K via the disproportionation reaction 20H a→ H 2O g+O a, considerably warmer than in the absence of Cs. It is postulated that this Cs-induced stabilization of OH a may be responsible for the promotional effect of Cs in water-gas shift catalysis over Cu. While H 2O a has a dipole pointing toward the surface, OH a creates a substantial dipole moment pointing away from the Cu. Upon dosing H 2O to Cs/O/Cu(110), the CsOH a species is also produced, and it decomposes at a slightly higher temperature than in the absence of O a (∼ 500–580 K).

Alkaline basalt-phonolite rocks from the Singen area, Hegau, southern F.R.G.

Pliocene volcanic rocks in the Singen ara, southern F.R.G., belong to an alkaline basalt-phonolite suite. The basalts show an average of 18% olivine xenocrysts, 5% augite xenocrysts, a groundmass of augite-melilite and some nepheline. Hydrous mafic minerals, such as hornblende and < 1% biotite, are present only in phonolite. Olivine was found to include spinel inclusions, and to have (Mg 0.83Fe 0.17) 2SiO 4 composition. Partial melting of 3–7% of appropriate pyrolite (clinopyroxene-olivine wehrlite with a small amount of basalt) may account for the magmatic composition of these rocks. Rimming of xenocrystic augite by pigeonite, and then by an outer rim of augite slightly richer in Fe, is common. These xenocrysts are followed successively by the crystallization of microphenocrysts of groundmass augite and then groundmass augite. The percentage of ferri Tschermak's molecule in augite rims seems to increase as Fe 3+ increases during the crystallization of clinopyroxene, and the presence of Na in excess of K indicates the presence of acmite fraction. The presence of feldspathoids in the basalt-phonolite rocks, the absence of Cs and Rb from the basalts, the composition of olivine xenocrysts and the presence of spinel inclusions indicate an origin from the lower half of the spinel peridotite zone in the upper part of the mantle, i.e. at 50–60-km depth. Ba, Th and U show a close affinity with K. Ba/Sr and K/Sr ratios, and Sc appear higher in alkali olivine-melilite rocks than those found in high-Al 2O 3 basalts. The reverse is true for K/Ba.