Melting of Diamond at High Pressure

Melting of diamond at high pressure and the properties of liquid carbon at pressures greater than 1 megabar were investigated with a first-principles molecular dynamics technique. The results indicate an increase of the diamond melting temperature with pressure, which is opposite to the behavior of silicon and germanium. This is contrary to long-held assumptions, but agrees with recent experiments, and has important implications for geology and astrophysics. As is the case for the solid phase of carbon at low temperature, which changes greatly with pressure from graphite to diamond, the structural and bonding properties of liquid carbon vary strongly with pressure.

Effects of the pre-column in automated on-column injection capillary gas chromatography

In this work, we investigated the effects of pre-columns and press-fit connectors on automated cold on-column injection capillary gas chromatography. Verapamil, a calcium channel blocking vasodilator used in the treatment of angina, arrhythmias and hypertension, and norverapamil, an active metabolite, were used as model compounds in these investigations. Wide-bore fused-silica tubing deactivated with OV-1701-vinyl was also studied with respect to its suitability as pre-column material. The detector response of verapamil versus an internal standard was consistent at micrograms/ml and ng/ml levels, while that of norverapamil decreased with the amount injected. However, the decrease in response of norverapamil appeared to be unrelated to the presence of a pre-column or press-fit connector in the chromatographic system.

The effect of M1 muscarinic blockade on behavior and physiological responses following traumatic brain injury in the rat

Dicyclomine (1 mg/kg or 10 mg/kg), scopolamine (1 mg/kg), or saline was administered intraperitoneally to rats 15 min prior to moderate fluid percussion brain injury. A variety of reflexes and responses were measured up to 60 min following injury, and body weight and several neurological measures were taken daily up to 10 days following injury. All 3 antimuscarinic treatments reduced the duration of transient behavioral suppression as assessed by these measures. It appears that blockade of the M1 muscarinic receptor can attenuate transient behavioral suppression associated with concussive brain injury. Thus, stimulation of M1 muscarinic receptors may mediate components of reversible traumatic unconsciousness following cerebral concussion. No differences were observed between saline and antimuscarinic treatments in the incidence or duration of apnea following injury. Scopolamine pretreatment significantly elevated heart rate prior to injury, but had no significant effect on the responses of heart rate and blood pressure to experimental concussion. Both doses of dicyclomine significantly reduced resting heart rate, but unlike scopolamine, significantly enhanced the cardiovascular response to fluid percussion injury. Antimuscarinic treatment significantly reduced body weight loss and certain motor deficits, including beam balance and beam walk performance, following concussive head injury. Scopolamine and both doses of dicyclomine appeared to be equally effective in reducing long-term deficits. Data from these experiments indicate that at least some of the long-term behavioral deficits following moderate levels of brain injury may involve the binding of acetylcholine to M1 muscarinic receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of acetylcholine depletion on behavior following traumatic brain injury

Rats were injected with either saline; A-4 (40 mg/kg, i.p.), a bis tertiary amine derivative of hemicholinium-3; or A-5 (50 micrograms/kg, i.p.), a bis quaternary amine derivative of hemicholinium-3, 1 h prior to moderate fluid percussion brain injury. A variety of reflexes and responses were measured up to 60 min following injury, and body weight and several neurological measures were taken daily up to 10 days following injury. Pretreatment with either A-4 or A-5 significantly attenuated components of transient behavioral suppression, as well as more enduring deficits in body weight and beam walk and beam balance performance. A-4 administered prior to fluid percussion was found to reduce striatal, but not pontine, acetylcholine content. A-5 did not significantly reduce acetylcholine content in either area. Both A-4 and A-5 pretreatment prevented a significant increase in acetylcholine content in the cerebrospinal fluid following fluid percussion injury; however, only A-5 significantly reduced plasma acetylcholine content. These results confirm cholinergic involvement in the production of both transient and longer-lasting behavioral deficits following traumatic brain injury. Furthermore, traumatic brain injury may allow plasma constituents to gain access to the central nervous system.

The effects of morphine and traumatic brain injury on central cholinergic neurons

This study examined the effects of morphine and fluid percussion traumatic brain injury (TBI) on the activity of cholinergic neurons in specific areas of the rat brain 12 min after injury. Acetylcholine (ACh) turnover, used as an index of cholinergic neuronal activity, was determined using gas chromatography-mass spectrometry. Although morphine administration alone in general did not significantly affect ACh content and turnover in specific brain areas, morphine administered prior to TBI either prevented injury-induced changes in ACh turnover (dorsal pontine tegmentum) or actually reduced the rate constant for ACh utilization (kACh) and the turnover rate of ACh (TRACh) following injury (thalamus, amygdala, cingulate/frontal cortex, and hippocampus). Thus, the protective effects of morphine against enduring behavioral deficits following TBI may involve the inhibition of central cholinergic neurons.

Disposition of the plant phenol ellagic acid in the mouse following oral administration by gavage

1. The absorption, distribution and elimination of 3H-ellagic acid, a putative antimutagen and anticarcinogen, was studied in male Swiss-Webster mice following oral administration. 2. Levels of 3H-ellagic acid were highest in blood 30 min after administration, in urine and bile 120 min post-administration, and in liver, lung and kidney 15 min after administration [corrected]. 3. Free ellagic acid and its conjugates were present in urine, bile and blood. H.p.l.c. analysis of the organic solvent extracts of urine, bile and blood indicated the presence of four metabolites in urine, two in blood and one in bile. 4. Sulphate ester, glucuronide and glutathione conjugates of ellagic acid were present in urine, bile and blood. H.p.l.c. analysis of organic solvent extracts after aryl sulphatase or beta-glucuronidase treatment showed that ellagic acid was the major component present. 5. Absorption of 3H-ellagic acid occurred mostly within two hours after oral administration. Levels in blood, bile and tissues were low and almost all of the absorbed dose was excreted in urine. 6. More than 53% of the orally administered 3H-ellagic acid remained in the gastrointestinal tract at 24 h. Approximately 19% was excreted in faeces and 22% in urine at 24 h. 7. Of the 24 h faecal radioactivity 93% was extractable into organic solvents and more than 80% of this fraction was free ellagic acid. Only one metabolite was found in faeces.

Ellagic acid metabolism and binding to DNA in organ explant cultures of the rat

Ellagic acid (EA) is a plant phenolic compound with postulated antimutagenic and anticarcinogenic activity. In this study, explants of esophagus, forestomach, colon, bladder, trachea, lung and liver from male Sprague-Dawley rats (130-140 g) were incubated in culture medium containing [3H]EA (20 microM, 4.5 microCi/ml) for 24 h at 37 degrees C. After extraction, purification and quantitation of explant DNA significant differences in the binding of EA to the DNA was observed. The most binding occurred in esophagus and the least in lung. Analysis of the organsoluble fraction of the culture medium by high performance liquid chromatography yielded 3 metabolites of EA. None of the metabolites were identified. Elution of water-soluble metabolites from an alumina column showed that there were sulfate ester, glucuronide and glutathione conjugates of EA in the explant culture medium from all the organs. The profile of water-soluble conjugates was very similar between colon and forestomach and between trachea and lung. These results indicate that EA binds to DNA in different tissues and that tissues metabolize EA to both organosoluble and water-soluble products.

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Simultaneous measurement of local glucose utilization and blood flow in the rat brain: an autoradiographic method using two tracers labeled with carbon-14

A simplified technique that uses two radionuclide tracers has been devised to measure local cerebral glucose utilization (ICGU) and local cerebral blood flow (ICBF) in the same rat. The method employs [14C]-2-deoxyglucose and [14C]iodoantipyrine to produce an autoradiogram before and another after extraction into chloroform of the [14C]iodoantipyrine from the brain sections. The chloroform-extracted autoradiogram yields ICGU, and the difference in tissue carbon-14 concentration between the two autoradiograms permits calculation of ICBF. The double-isotope technique provides values of ICGU and ICBF that are statistically indistinguishable from those derived from conventional single-isotope methods.