Energy release in the solar corona from spatially resolved magnetic braids.

It is now apparent that there are at least two heating mechanisms in the Sun's outer atmosphere, or corona. Wave heating may be the prevalent mechanism in quiet solar periods and may contribute to heating the corona to 1,500,000 K (refs 1-3). The active corona needs additional heating to reach 2,000,000-4,000,000 K; this heat has been theoretically proposed to come from the reconnection and unravelling of magnetic 'braids'. Evidence favouring that process has been inferred, but has not been generally accepted because observations are sparse and, in general, the braided magnetic strands that are thought to have an angular width of about 0.2 arc seconds have not been resolved. Fine-scale braiding has been seen in the chromosphere but not, until now, in the corona. Here we report observations, at a resolution of 0.2 arc seconds, of magnetic braids in a coronal active region that are reconnecting, relaxing and dissipating sufficient energy to heat the structures to about 4,000,000 K. Although our 5-minute observations cannot unambiguously identify the field reconnection and subsequent relaxation as the dominant heating mechanism throughout active regions, the energy available from the observed field relaxation in our example is ample for the observed heating.

Low Altitude Solar Magnetic Reconnection, Type III Solar Radio Bursts, and X-ray Emissions.

Type III solar radio bursts are the Sun's most intense and frequent nonthermal radio emissions. They involve two critical problems in astrophysics, plasma physics, and space physics: how collective processes produce nonthermal radiation and how magnetic reconnection occurs and changes magnetic energy into kinetic energy. Here magnetic reconnection events are identified definitively in Solar Dynamics Observatory UV-EUV data, with strong upward and downward pairs of jets, current sheets, and cusp-like geometries on top of time-varying magnetic loops, and strong outflows along pairs of open magnetic field lines. Type III bursts imaged by the Murchison Widefield Array and detected by the Learmonth radiospectrograph and STEREO B spacecraft are demonstrated to be in very good temporal and spatial coincidence with specific reconnection events and with bursts of X-rays detected by the RHESSI spacecraft. The reconnection sites are low, near heights of 5-10 Mm. These images and event timings provide the long-desired direct evidence that semi-relativistic electrons energized in magnetic reconnection regions produce type III radio bursts. Not all the observed reconnection events produce X-ray events or coronal or interplanetary type III bursts; thus different special conditions exist for electrons leaving reconnection regions to produce observable radio, EUV, UV, and X-ray bursts.

Challenges in biodegradation of trace organic contaminants--gasoline oxygenates and sex hormones.

Advances in analytical methods have led to the identification of several classes of organic chemicals that are associated with adverse environmental effects. Two such classes of organic chemicals, gasoline oxygenates and sex hormones, are used to illustrate challenges associated with the biodegradation of trace organic contaminants. Gasoline oxygenates can be present in groundwater, alone, or commingled with xylene, at appreciable concentrations. However, target-treated water standards dictate that gasoline oxygenates be reduced to the microgram-per-liter concentration range before consumption. Sex hormones, on the other hand, are present in wastewater matrixes in the part-per-trillion concentration range, and the biggest challenge that must be met, before optimizing their removal, is facilitating their detection.

Clonidine-specific antisera recognize an endogenous clonidine-displacing substance in brain.

An endogenous substance in brain, clonidine-displacing substance, binds to the same receptor populations as clonidine and is biologically active. Since receptor binding sites can be modeled by using specific antiligand antibodies, we tested the hypothesis that polyclonal antibodies raised in rat and rabbit against the clonidine analog p-aminoclonidine coupled to hemocyanin would recognize compounds structurally related to clonidine, including clonidine-displacing substance. Binding to anti-p-aminoclonidine antibodies was examined by using a competitive radioimmunoassay with tritiated p-aminoclonidine as the radioligand. Central vasodepressor agents that, like clonidine, are known to bind with high affinity to both imidazole sites and alpha 2-adrenergic receptors in brain inhibited radioligand binding to anti-p-aminoclonidine antibodies. All of these agents contain imidazol(in)e and phenyl ring moieties as part of their chemical structures (e.g., oxymetazoline); a number of other compounds without one or both of these rings failed to cross-react with the antisera. Clonidine-displacing substance, partially purified from bovine brain, also inhibited specific radioligand binding to anti-p-aminoclonidine antibodies. The inhibition was dose dependent and high affinity (IC50, 4 Units). The endogenous substance had no effect on the apparent affinity of the antibodies for the radioligand, but blocked a specific number of binding sites. Immunoprecipitation experiments showed that authentic clonidine-displacing substance, that which displaces tritiated p-aminoclonidine binding to membrane receptors, is recognized by anti-p-aminoclonidine antibodies. We conclude that a unique subset of structural determinants required for ligand interaction with both imidazole and alpha 2-adrenergic receptors is critical for binding to anti-p-aminoclonidine antibodies, and that since clonidine-displacing substance is recognized by highly clonidine-specific antisera, it may also contain these determinants within its structure, namely the imidazol(in)e and phenyl ring systems.

Dopamine-induced reduction in the density of guanine nucleotide-sensitive D1 receptors in human postmortem brain in the absence of apparent D1: D2 interactions.

The effects of dopamine and guanine nucleotides on the binding of the D1 dopamine receptor antagonist ligand [3H]SCH 23390 were examined in membranes prepared from putamen, caudate and nucleus accumbens of human postmortem brain. Dopamine induced a concentration-dependent decrease in the apparent maximum number of binding sites (Bmax) in each brain region studied, and displaced binding in a biphasic manner consistent with the presence of both high and low affinity states of the D1 receptor; the GTP analogue Gpp(NH)p transformed this biphasic displacement to a monophasic pattern consistent with a shift of high affinity sites to a low affinity state. However, the selective D2 antagonist eticlopride did not reverse the action of dopamine to decrease Bmax. These data suggest that dopamine decreases Bmax for D1 receptors through a high affinity, guanine nucleotide-sensitive agonist binding site, but fail to reveal D1:D2 interactions at this synaptic level.

Relationship of dietary iodide and drinking water disinfectants to thyroid function in experimental animals.

The importance of dietary iodide on the reported hypothyroid effect of drinking water disinfectants on thyroid function was investigated. Previous studies have also showed differences in the relative sensitivity of pigeons and rabbits to chlorinated water. Pigeons and rabbits were exposed for 3 months to diets containing high (950 ppb) or low (300 ppb) levels of iodide and to drinking water containing two levels of chlorine. Results showed that the high-iodide diet prevented the hypothyroid effect observed in pigeons given the low-iodide diet and chlorinated drinking water. Similar trends were observed in rabbits exposed to the same treatment; however, significant hypothyroid effects were not observed in this animal model. The factor associated with the observed effect of dietary iodide on the chlorine-induced change in thyroid function is unknown, as is the relative sensitivity of rabbits and pigeons to the effect of chlorine. Several factors may explain the importance of dietary iodide and the relative sensitivity of these species. For example, the iodine formed by the known reaction of chlorine with iodide could result in a decrease in the plasma level of iodide because of the relative absorption rates of iodide and iodine in the intestinal tract, and the various types and concentrations of chloroorganics (metabolites) formed in the diet following the exposure of various dietary constituents to chlorine could affect the thyroid function. The former factor was investigated in the present studies. Results do not confirm a consistent, significant reduction in the plasma level of iodide in rabbits and pigeons exposed to chlorinated water and the low-iodide diet. The latter factor is being investigated.

Non-ICU care of hemodynamically stable mechanically ventilated patients.

OBJECTIVE: To analyze a 4 1/2-year experience caring for hemodynamically stable mechanically ventilated patients on a nonmonitored respiratory care floor (RCF) for therapeutic outcome, utilization, and costs. DESIGN: A retrospective medical records review. SETTING: ICUs and an RCF of a university-affiliated tertiary care center. PARTICIPANTS: Two hundred twenty-four patients requiring more than 24 h of mechanical ventilation cared for on the RCF. RESULTS: The mean age of patients was 67 +/- 17 years. Of the admissions, 58% were from the medical ICU, 28% were from surgical ICUs, and 9.4% were from general medical floors. Patients spent 50 +/- 66 days mechanically ventilated on the RCF. Overall survival was 50.4% with 93.8% of surviving patients successfully weaned from mechanical ventilation. Survival by diagnostic group demonstrated highest probability of survival in patients with trauma and lowest in patients with multisystem failure. Of the survivors, 39% were discharged home, 34% to a rehabilitation unit, and 24% to a skilled nursing facility. Savings based on differential of costs between the ICU and RCF, primarily from reduced staffing requirements, were estimated at $4.1 million. CONCLUSION: Use of a nonmonitored RCF for the care of hemodynamically stable mechanically ventilated patients yields acceptable therapeutic outcomes while providing the institution with increased flexibility in critical care bed management and significant financial savings.

Clonidine-displacing substance is present in peripheral tissues of the rat.

Clonidine-displacing substance (CDS) is biologically active in the brain, as well as the gastric fundus, platelets and vas deferens. We sought to determine whether CDS is contained within peripheral tissues in the rat. Using competitive radioimmunoassay with a clonidine-specific antiserum and 3H-p-aminoclonidine rat adrenal gland and gastric fundus were shown to contain significantly greater amounts of CDS-like radioimmunoactivity than the brain; intermediate-to-low activity was present in the heart, small intestine, serum, kidney and liver. Lung and skeletal muscle exhibited near-background levels. CDS may not be unique to the brain, but also may be synthesized and stored in peripheral organs.

Behavioural pharmacology of 'D-1-like' dopamine receptors: further subtyping, new pharmacological probes and interactions with 'D-2-like' receptors.

1. D-1 receptors are now recognised to play a critical psychopharmacological role in the regulation of unconditioned motor and numerous other aspects of behaviour. 2. There appears to exist a broad family of 'D-1-like' receptors in terms both of differential coupling to distinct messenger/transduction mechanisms and of gene cloning, whose behavioural roles remain to be clarified. 3. The adenylyl cyclase-inhibiting benzazepine SK&F 83959 induces behavioural responses in rats that are similar to those induced by the full efficacy cyclase-stimulating isochroman A 68930 but not to those induced by its high efficacy partial agonist benzazepine congener R-6-Br-APB; these data indicate roles for individual 'D-1-like' receptors in mediating distinct elements of dopaminergic behaviour. 4. The putative D-1 autoreceptor agonist B-HT 920 and the putative D-3 agonist 7-OH-DPAT demonstrate different behavioural profiles when given both alone and in combination with the selective 'D-1-like' antagonist BW 737C; D-3 receptors may participate in cooperative/synergistic but not in oppositional 'D-1-like': 'D-2-like' interactions. 5. Such interactions apparent at the level of behaviour are complemented by evidence for similar interactions at numerous alternative levels of function, though these may differ between rodent and primate species. 6. A broader range of more selective agonists and antagonists, able to distinguish between individual members of the 'D-1-like' and of the 'D-2-like' receptor families are needed to clarify these issues.

The effects of lead on the developing central nervous system of the rat.

Biochemical and structural development of the cerebral cortex of rat pups is delayed by low levels of lead administered in the dam's drinking water during gestation and suckling periods. These changes in brain development coincide with delays in the development of exploratory and locomotor activity and impaired learning. Subsequent cross-fostering experiments have shown that delays in synaptogenesis and in the development of exploratory behavior were attributed entirely to the prenatal, as opposed to the postnatal, exposure to lead at the low dose levels utilized. Examination of the variations in blood lead concentrations in pups and dams during gestation and until weaning at 21 days of postnatal age indicated that a substantial increase in blood lead concentrations occurred late in pregnancy. At 200 mg of Pb/liter of drinking water, peak blood Pb concentrations were observed to be approximately 60 micrograms/dl in dams and 80 micrograms/dl in pups on the 20th day of gestation. By the 10th postnatal day blood Pb concentrations had decreased to 35 micrograms/dl in dams and 40 microgram/dl in pups despite an increased consumption of drinking water containing the same concentration of Pb during this period. (Delays in cerebral cortical development were observed after 10 days of postnatal age). Tracer studies utilizing 203Pb indicate that the rate of Pb absorption was substantially increased in the pregnant, relative to the non-pregnant, dam. Although a similar increase in 45Ca absorption was also observed during pregnancy, increases in Pb absorption were enhanced by Pb-pretreatment, whereas Ca absorption was independent of Pb-pretreatment. From this data it is concluded that the apparently greater sensitivity of postnatal development on prenatal Pb exposure is secondary to enhanced Pb absorption in the pregnant rat. In vitro metabolic studies in isolated cerebral cortex slices taken from 15 day old rat pups exposed to Pb revealed increased glucose and oxygen consumption in response to elevations in the potassium concentration of the incubation media. This evidence of metabolic uncoupling in the immature rat cerebral cortex may be causally related to the measured delays in brain development.

Differences in reported symptom profile between panic disorder and other DSM-III-R anxiety disorders.

Previous research has indicated that reports of panic attacks are associated with a different set of symptoms to reports of generalized anxiety. The present two studies attempted to extend these findings to specific (situational) fears. In Study 1, 55 subjects with panic disorder were compared on their symptom profile during their panic attacks to 65 subjects with other anxiety disorders [simple phobia, social phobia and obsessive-compulsive disorder (OCD)] during response to their feared cue. The results indicated that, compared to subjects with other anxiety disorders, subjects with panic disorder were more likely to report parasthesias, dizziness, faintness, unreality, dyspnea, fear of dying and fear of going crazy/losing control. In Study 2, 90 subjects meeting diagnostic criteria for both panic disorder and another anxiety disorder (simple phobia, social phobia or OCD) were compared on the symptoms experienced during their unexpected panic attacks and their situationally-triggered fears respectively. Combining the symptoms found in Study 1 to differ between the groups into a linear combination, there was a significant interaction found between the type of fear reaction (panic attack vs cued fear response) and symptom group. Taken together, these findings suggest that reports of unexpected panic attacks associated with panic disorder are characterized by a different symptom profile to reports of specific fear reactions that are part of a phobic disorder or OCD.

X-ray microanalysis of calcium, potassium, and phosphorus in liver mitochondria stressed by carbon tetrachloride.

Previous measurements of elemental concentrations in liver mitochondria have generally required homogenization and fractionation of liver tissue, a procedure in which it is difficult to rule out ion movement between subcellular units. New techniques involving cryoultramicrotomy of rapidly frozen tissue, high resolution scanning transmission electron microscopy, and X-ray microanalysis were used to measure those elements in rat liver mitochondria reported to have changed following oral administration of carbon tetrachloride (CCl4). Increases in liver mitochondrial calcium were found 24 hr following intoxication by CCl4. Significant early (2 hr) mitochondrial increases in potassium and phosphorus were found following administration of CCl4. The electron microscope technique using quick-frozen samples promises to allow measurement of intracellular ionic concentrations under virtually lifelike conditions.

Clonidine-specific antibodies as models for imidazole and alpha 2-adrenergic receptor binding sites: implications for the structure of clonidine-displacing substance.

Polyclonal antisera raised against para-aminoclonidine coupled to haemocyanin exhibit high affinity for para-aminoclonidine, clonidine and chloroethylclonidine (IC50 less than 100 nmol/l). Anti-para-aminoclonidine antibodies also cross-react with naphazoline, oxymetazoline and tolazoline at moderate concentrations (IC50, 300-500 mumol/l); the phenyl-imidazoles detomidine, medetomidine and MPV830 are weakly cross-reactive (IC50 greater than 0.2 mmol/l). All of these compounds bind with high affinity to both imidazole and alpha 2-adrenergic receptors. Compounds which are imidazole- or alpha 2-specific do not cross-react with anti-para-aminoclonidine antibodies (IC50 greater than 1 mmol/l). Anti-para-aminoclonidine also recognizes an endogenous clonidine-displacing substance in the brain. Thus, (a) binding to anti-para-aminoclonidine antibodies defines a subset of phenyl-imidazol(in)e ligands which bind to both imidazole and alpha 2-adrenergic receptors, suggesting that anti-para-aminoclonidine recognition sites resemble a hybrid of the two receptor types; (b) antibodies to imidazole- or alpha 2-specific agents may be useful as models for differentiating between these types; (c) since clonidine-displacing substance is recognized by anti-para-aminoclonidine antibodies, it may have phenyl and imidazole rings as parts of its chemical structure.

Prevalence of small-scale jets from the networks of the solar transition region and chromosphere.

As the interface between the Sun's photosphere and corona, the chromosphere and transition region play a key role in the formation and acceleration of the solar wind. Observations from the Interface Region Imaging Spectrograph reveal the prevalence of intermittent small-scale jets with speeds of 80 to 250 kilometers per second from the narrow bright network lanes of this interface region. These jets have lifetimes of 20 to 80 seconds and widths of ≤300 kilometers. They originate from small-scale bright regions, often preceded by footpoint brightenings and accompanied by transverse waves with amplitudes of ~20 kilometers per second. Many jets reach temperatures of at least ~10(5) kelvin and constitute an important element of the transition region structures. They are likely an intermittent but persistent source of mass and energy for the solar wind.

Hunger and the vocalizations of infant gerbils.

Infant gerbils were deprived of food by removing their mother from the cage for 3 hr on alternate days, during which time they remained with their father. These infants were compared with a control group which remained with their mother while the father was removed. Litters lost weight when deprived of food but they received similar levels of parental care, warmth, and tactile stimuli to those of nonfood-deprived litters. There were no significant effects on the vocalizations of the young when tested either in isolation or in the nest with other pups. This apparent absence of a mode of communicating nutritional state is discussed with reference to normal interactions between adults and the litter and the role of vocalizations produced in response to heat loss.

Experimental approaches to evaluating the role of environmental factors in the development of cardiovascular disease.

Epidemiologic studies have suggested factors in drinking water influence on the human cardiovascular system. A clear identification of the factors involved requires more invasive techniques and more strict experimental controls than can usually be applied in epidemiologic studies. Consequently laboratory animals are often used to expand and support epidemiologic data. For laboratory purposes cardiovascular toxicology must be broken down to effects on the myocardium, the vasculature and the kidney. Further division may be necessary to take into account the influence of the neuroendocrine system or other systems that influence the function of the cardiovascular system. Since environmental influences upon the cardiovascular disease are relatively subtle (versus the acute effects of some drugs) it is assumed that major difficulties are chronic in nature. Accordingly, it is suggested that laboratory experimentation focus on either chronic toxin exposure or short-term exposure to stressed or genetically susceptible animals. A variety of in vivo and in vitro tests may be necessary to relate the toxicity realized in animals to what might be expected in man. Wide species differences with respect to the susceptibility of particular target tissues must be taken into account to clearly apply the results to man. Similarly, special characteristics of stressed and genetically susceptible animals must be understood to avoid deceptive results.

Hypochlorite-serum reaction products inhibit porcine vascular endothelial cell growth in culture.

In vitro toxicity studies wer initiated in order to determine if chlorination affects vascular endothelial cells. Twelfth to twentieth passage porcine aortic vascular endothelial cells (PAE) were grown to confluency and replated in the presence of complete media (Eagle's minimum essential media supplemented with 20% fetal bovine serum) which had been preincubated for 30 minutes with 15.0 mg/liter chlorine. During a 72-hour exposure period, control PAE cells grew to confluency, an increase of approximately 9 fold in the number of cells/plate. Those cells exposed to media preincubated with 15.0 mg/liter chlorine derived from sodium hypochlorite increased only 6 fold. There was no sign of cell killing, but an apparent inhibition of cell division. No effect was seen when either the amino acid or vitamin component of the complete media was reacted at the 15.0 mg dose level. However, when the serum component was preincubated with 15.0 mg chlorine/liter as sodium hypochlorite, an inhibition in growth rate similar to the complete media occurred.

Barium bioavailability as the chloride, sulfate, or carbonate salt in the rat.

This study was conducted to determine how the bioavailability of a low concentration of barium (Ba) in drinking water is affected by the anion. Male Sprague Dawley rats weighing 250-300 grams were maintained on a diet of less than 1 mg Ba/kg of food for at least 1 month prior to experimentation. Rats were given 10.0 mg 131Ba/liter as sulfate (SO4), chloride (Cl), or carbonate (CO3) at pH 7.0. Animals were sacrificed at 2, 5, 10, 20, 30, 60, and 120 minutes and 24 hours after intubation. When 131Ba was administered, as Cl, 131Ba in blood rose linearly for 10 minutes and then less rapidly until the highest number of counts was measured at 60 minutes. At 24 hours 131Ba was still at 90% of peak levels. Five tissues were tested 24 hours after dosing for 131Ba. In decreasing order of 131Ba concentration they were heart, eye, skeletal muscle, kidney, and liver. 131Ba in the heart reached 8x that observed in blood 24 hours after dosing. In the eye, 131Ba increased linearly for 1 hour. Isotope concentrations in the eye eventually reached 2.5x that observed in blood. When 131Ba was administered as SO4 or CO3, 131Ba in blood was respectively 85% or 45% of levels, of 131Ba from 131BaCl2. Initial uptake of 131Ba and deposition in the eye were not different when administered as Cl or SO4.