On-line HfF5(-)/WF5(-) separation in an O2-filled radiofrequency quadrupole gas cell.

RATIONALE: An experimental Isobar Separator for Accelerator Mass Spectrometry (ISAMS) instrument has been used to demonstrate an on-line separation of HfF5(-) from its isobar WF5(-). This is necessary, in addition to sample preparation chemistry, for measuring (182)Hf at natural levels by Accelerator Mass Spectrometry (AMS). METHODS: The device utilizes a radiofrequency quadrupole (RFQ) controlled gas cell, wherein anion-gas reactions at eV energies attenuate the interfering isobars of the analyte molecular anions, leaving HfF5(-) for AMS analysis. The RFQ also helps to control the multiple scattering resulting from the ion-gas collisions. RESULTS: O2 gas was used in the HfF5(-)/WF5(-) separation and WF5(-) was attenuated by nearly 3 orders of magnitude while maintaining ~75% transmission of HfF5(-). It is expected that the transmission and attenuation can be increased by further research. CONCLUSIONS: This result advances the possibility of detecting natural (182)Hf when AMS is supplemented with an isobar separator in the injection system.

SU-E-I-55: Cumulative Radiation Exposure and Cancer Risk Estimates in Pediatric Hydrocephalus Patients Undergoing Repeat Or Multiple CT.

PURPOSE: Children with a shunt for hydrocephalus often undergo multiple follow-up head CT scans, increasing the risk for long-term effects of ionizing radiation. The study is to define a conservative estimate of frequent CT head scans for pediatric patients with a shunt for hydrocephalus and to quantify their cumulative CT radiation doses and lifetime attributable risk of developing cancer. METHODS: All children at age of less than 17 years with a shunt for hydrocephalus who underwent non-enhanced head CT at a tertiary hospital between 2007 and 2011 were identified and categorized by total number of scans per study period as non-frequently (<3), or frequently (>=3) scanned. We retrospectively identified the number of CT head scans, dose length product (DLP) and the applied scan parameters according to age, gender and study time. Effective doses were estimated using age- specific DLP to effective dose conversion coefficients. Lifetime attributable cancer risk was then estimated based on the BEIR VII. RESULTS: During the 5-year study period, a total of 264 children (mean age, 5.5 years; range less than one month to 17 years; 146 boys and 118 girls) underwent 747 CT head scans, of whom 100 patients (41.7%) were frequently scanned. The median and mean of frequently scans are 4 and 5.33, with the most frequently scanned patient underwent 34 CT head scans from birth to 4 years and 1 month age. The average effective dose was 15.71 mSv, ranging from 3.65 mSv to 64.70 mSv. The estimated lifetime attributable cancer risk is one in 637, ranging from one in 2739 to one in 155, based on the standardized BEIR VII conversion of 0.0001/mSv. CONCLUSIONS: The children with shunts have a substantially increased risk of developing cancer from cumulative CT radiation exposure.

SU-E-I-46: Quantitative Effects of Clinical Practice on the Efficiency of CT Tube Current Modulation for Radiation Dose Reduction.

PURPOSE: CT tube current modulation (TCM) represents one of the most important and efficient methods for radiation dose reduction and has been well accepted. However, the possible influence of clinical practice is likely to be ignored although venders may provide clinical protocols and instructions. This study is designed to further investigate the quantitative effects of clinical operation, including radiograph direction and patient positioning, on the efficiency of TCM by measuring patient radiation dose and image quality. METHODS: An anthromorphologic chest phantom was scanned in a Sensation 40 and a lightSpeed 16 CT scanner, respectively, using routine chest protocols with TCM. We first investigated the effects of radiograph direction. Anterior-posterior (AP), lateral, and posterior-anterior (PA) directions were chosen. CTDIvol and dose-length-product (DLP) were recorded for analyses. Our second experiment studied the influence of patient position. First the phantom was positioned at the iso-center then scanned with AP direction. CTDIvols and DLPs were recorded as reference. Then the phantom was moved out of iso-center, up or down 2 and 4 cm respectively then scanned. CTDIvols and DLPs were recorded for comparison. For each setting, image noise was measured. RESULTS: CTDIvol increases approximately 20% for PA direction, compared to AP or lateral direction which generates similar CTDIvol and DLP with TCM. Image noise for the PA direction is less than those for the AP or lateral directions. CTDIvol increases approximately 9% for LightSpeed 16 and 13% for Sensation 40 when the phantom was moved up 4 cm, while CTDIvol decreases approximately 5% for LightSpeed 16 and 8% for Sensation 40 when the phantom was moved down 4 cm. CONCLUSIONS: Our quantitative study can direct clinical practice to improve the efficiency of CT tube current modulation and reduce patient radiation dose.

A comparison of nucleic acid amplification techniques for the assessment of bacterial viability.

AIMS: The ability to determine the presence and viability status of bacteria by molecular methods could offer significant advantages to the food, environmental and health sectors, in terms of improved speed and sensitivity of detection. METHODS AND RESULTS: In this study, we have assessed three amplification techniques, PCR, RT-PCR and NASBA, for their ability to detect nucleic acid persistence in an E. coli strain following heat-killing. NASBA offered the greatest sensitivity of the three methods tested. The presence of residual DNA and mRNA could be detected by PCR and NASBA, respectively, for up to 30 h postdeath, by which time cell death had been confirmed by culture methods. Thus a single quantitative measurement based on nucleic acid amplification did not permit unequivocal determination of cell viability. CONCLUSIONS, SIGNIFICANCE AND IMPACT OF THE STUDY: The correlation between cell viability and persistence of nucleic acids must be well characterized for a particular analytical situation before molecular techniques can be substituted for traditional culture methods.

Interlaboratory study on thermal cycler performance in controlled PCR and random amplified polymorphic DNA analyses.

BACKGROUND: Intercomparisons of PCR-based data between laboratories require an assurance of assay reproducibility. We performed an interlaboratory study to investigate the contribution made by a variety of thermal cyclers to PCR performance as measured by interblock reproducibility and intrablock repeatability. METHODS: Two standardized assays designed to minimize the introduction of non-thermal-cycler-dependent variations were evaluated by 18 laboratories in the United Kingdom, using 33 thermal cyclers of various makes and models. We used a single-product (590 bp) PCR, established in our laboratory as a robust and specific reaction. The second reaction, a multiproduct random amplified polymorphic DNA (RAPD) PCR, was known to be more susceptible to small changes in block temperature and was therefore considered a way of assessing block uniformity with respect to temperature. Assay repeatability data were analyzed with respect to temperature calibration status, the type of temperature control mechanism, thermal cycler age, and the presence of oil overlay or heated lid systems. RESULTS: All (100%) of the laboratories produced the correct target for the single-product PCR assay, although substantial variation in yield in replicate reactions was observed in 9.4% of these. The RAPD reaction generated results that varied extensively both within the same block and between different thermal cyclers. For eight replicates of a positive sample, 88% intrablock repeatability was demonstrated in calibrated thermal cyclers, which decreased to 63% in noncalibrated instruments. CONCLUSIONS: Irrespective of the make and model of thermal cycler, temperature-calibrated instruments consistently generated more repeatable RAPD data than noncalibrated instruments. Guidelines are offered on optimizing and monitoring thermal cycler performance.

Ischemic exercise and the muscle metaboreflex.

In exercising muscle, interstitial metabolites accumulate and stimulate muscle afferents. This evokes the muscle metaboreflex and raises arterial blood pressure (BP). In this report, we examined the effects of tension generation on muscle metabolites and BP during ischemic forearm exercise in humans. Heart rate (HR), BP, P(i), H(2)PO(4)(-), and pH ((31)P-NMR spectroscopy) data were collected in 10 normal healthy men (age 23 +/- 1 yr) during rhythmic handgrip exercise. After baseline measurements, the subjects performed rhythmic handgrip for 2 min. At 2 min, a 250-mmHg occlusion cuff was inflated, and ischemic handgrip exercise was continued until near fatigue (Borg 19). Measurements were continued for an additional 30 s of ischemia. This protocol was performed at 15, 30, 45, and 60% of the subjects' maximum voluntary contraction (MVC) in random order. As tension increased, the time to fatigue decreased. In addition, mean arterial pressure and HR were higher at 60% MVC than at any of the other lower tensions. The NMR data showed significantly greater increases in H(2)PO(4)(-), P(i), and H(+) at 60% than at 15 and 30% MVC. Therefore, despite the subjects working to the same perceived effort level, a greater reflex response (represented by BP and HR data) was elicited at 60% MVC than at any of the other ischemic tensions. These data are consistent with the hypothesis that, as tension increases, factors aside from insufficient blood flow contribute to the work effect on muscle metabolites and the magnitude of the reflex response.

Forearm training reduces the exercise pressor reflex during ischemic rhythmic handgrip.

We examined the effects of unilateral, nondominant forearm training (4 wk) on blood pressure and forearm metabolites during ischemic and nonischemic rhythmic handgrip (30 1-s contractions/min at 25% maximal voluntary contraction). Contractions were performed by 10 subjects with the forearm enclosed in a pressurized Plexiglas tank to induce ischemic conditions. Training increased the endurance time in the nondominant arm by 102% (protocol 1). In protocol 2, tank pressure was increased in increments of 10 mmHg/min to +50 mmHg. Training raised the positive-pressure threshold necessary to engage the pressor response. In protocol 3, handgrip was performed at +50 mmHg and venous blood samples were analyzed. Training attenuated mean arterial pressure (109 +/- 5 and 98 +/- 4 mmHg pre- and posttraining, respectively, P < 0.01), venous lactate (2.9 +/- 0.4 and 1.8 +/- 0.3 mmol/l pre- and posttraining, respectively, P < 0.01), and the pH response (7.21 +/- 0.02 and 7.25 +/- 0.01, pre- and posttraining, respectively, P < 0.01). However, deep venous O2 saturation was unchanged. Training increased the positive-pressure threshold for metaboreceptor engagement, reduced metabolite concentrations, and reduced mean arterial pressure during ischemic exercise.

Design and construction of a long-term continuous video-EEG monitoring unit for simultaneous recording of multiple small animals.

In recent years several new rat models of human limbic/mesial temporal lobe epilepsy have been described [1,2,4-7,11,15-17]. Unlike earlier models such as kindling in which the seizures are induced by an exogenous stimulus, these new models are characterized by seizures that occur spontaneously at random intervals. Although the spontaneity of the seizures makes these models more like human epilepsy, documentation of these seizures by direct observation is highly inefficient, and sub-behavioral electrographic seizures could be missed. Continuous paper EEG and video recording have been used [5-7,15], but these techniques are resource intensive. The slow paper speed required by long-term paper recordings limits the ability to differentiate between true seizure activity and electrical artifact. Subtle behavioral seizures are likely to be missed during rapid review of video recordings alone [16]. Ambulatory cassette EEG recordings have been used [3], but the systems require expensive proprietary hardware, and the systems have limited channels for recording (8-16). To improve the utility of the models, we developed a long-term EEG/video monitoring system to detect the electrographic seizures and document their behavioral accompaniment. The system is based on commercially available components, including a computerized EEG seizure detection system that was initially developed for human seizure monitoring [8,9,13]. Seizures are reliably detected and the data are reduced so that 24 h of recording can be reviewed in 30-90 min. Although the computer program is accurate, special care must be taken in system design and construction to reduce sources of electrical artifact that can cause false detections when multiple animals are recorded simultaneously on a single EEG machine. During data review it is necessary to differentiate between electrical artifact induced by animal activity from true seizure activity by key EEG patterns. Certain seizure patterns (less than 3 hz. low amplitude) will not be detected by the seizure detection program, but the system is highly effective for typical limbic seizures and may be useful for the animal models of absence epilepsy [12,14]. It can also be used as a continuous or intermittent EEG/physiological recording device for experiments that examine animals' spontaneous behavior and the EEG correlate (e.g. sleep/wake cycles, learning and memory tasks).

Prostate cancer screening in the prostate, lung, colorectal and ovarian cancer screening trial of the National Cancer Institute.

Screening for prostate cancer and subsequent treatment is of unknown benefit but carries known treatment related morbidity and mortality risks. The recent enthusiasm for screening in the United States contrasts sharply with the more cautious attitudes of the European and Canadian medical communities. Current data from screening series without randomization and controls are inadequate to determine screening benefit. The prostate, lung, colorectal and ovarian cancer (randomized, controlled) screening trial of the National Cancer Institute, to include 74,000 men (and 74,000 women) 60 to 74 years old, has a design power of 90% to determine a 20% reduction of prostate cancer mortality from a baseline and 3 subsequent annual screens using prostate specific antigen and digital rectal examination. Randomization of participants into this trial began on November 16, 1993. Ten screening centers nationwide, a coordinating center, a laboratory and a biorepository are participating under contract.

Modeling gas exchange in a closed plant growth chamber.

Fluid transport models for fluxes of water vapor and CO2 have been developed for one crop of wheat and three crops of soybean grown in a closed plant growth chamber. Correspondence among these fluxes is discussed. Maximum fluxes of gases are provided for engineering design requirements of fluid recycling equipment in growth chambers. Furthermore, to investigate the feasibility of generalized crop models, dimensionless representations of water vapor fluxes are presented. The feasibility of such generalized models and the need for additional data are discussed.

The evolution of a rat model of chronic spontaneous limbic seizures.

The evolution of untreated partial epilepsy is unknown. This study uses a newly developed model of chronic limbic epilepsy to determine whether seizures inexorably worsen in duration, frequency and behavioral accompaniment. The seizures begin following an episode of limbic status epilepticus induced by continuous electrical stimulation of the hippocampus, and they persist for more than a year (longest duration followed). We monitored 10 rats continuously with combined EEG and closed circuit television for 24 weeks following the first recorded spontaneous seizure. Seizure duration, behavioral accompaniment and frequency all intensified during the early stages, but the last 12-16 weeks of the study were characterized by a plateau for all measures. The results showed significant increases that occurred over the first 12 weeks only (P < 0.01 for duration and behavioral accompaniment, P < 0.05 for seizure frequency). These findings suggest that untreated epilepsy will undergo an early maturation process, but that once the seizures mature they remain stable over a prolonged period. It was also noted that 67% (P < 0.00001) of the seizures occurred during the day, suggesting that the sleep-wake cycle has a strong influence on the occurrence of seizures in this model of limbic epilepsy.

The ontogeny of seizures in a rat model of limbic epilepsy: evidence for a kindling process in the development of chronic spontaneous seizures.

Kindling is an experimental model for epilepsy in which repeated stimuli induce longer electrographic seizures and eventually cause behavioral convulsions. Although kindling has some features that are similar to chronic human epilepsy, it is not known whether this process plays a role in the development of chronic seizure disorders. We have recently described a rat model of chronic spontaneous limbic seizures that has a number of similarities to human limbic epilepsy. To determine whether a kindling process is involved in the ontogeny of the seizures in this animal model, we continuously monitored 16 rats with EEG and closed circuit television until they had experienced a minimum of 5 and as many as 10 seizures following the first motor seizure. All animals had at least one non-motor seizure before the first motor event (mean 5.1 +/- 0.9 S.E.M. initial non-motor seizures, range 1-12). In addition the seizures significantly lengthened in duration with succeeding events (mean 90 s for the first motor seizure to mean 110 s for the tenth subsequent seizure). These data demonstrate that there is a kindling process involved in the early development of chronic limbic seizures.

Lead content in 70 brands of dietary calcium supplements.

OBJECTIVES: Elevated lead levels in calcium supplements may pose a health risk, particularly to children with milk intolerance who rely on these products to meet their calcium requirement. Earlier reports chiefly focused on the lead content in supplements derived from bonemeal and dolomite. This study undertook to determine the lead levels in the major forms of calcium supplements currently available. METHODS: The lead content was measured in 70 brands of calcium supplements grouped in the following five categories: dolomite, bonemeal, refined and natural source calcium carbonate, and calcium chelates. RESULTS: The lead levels measured in the supplements ranged from 0.03 microgram/g to 8.83 micrograms/g. Daily lead ingestion rates revealed that about 25% of the products exceeded the US Food and Drug Administration's "provisional" total tolerable daily intake of lead for children aged 6 years and under. Less than 20% of the supplements had "normalized" lead levels comparable to or lower than that reported for cow's milk. CONCLUSIONS: Children are the most sensitive to the low-level effects of lead. If calcium supplements are to provide an alternate source of calcium to some of these individuals, they should also deliver concomitant lead dosages no greater than those obtained from milk products themselves.

Initial evaluation of a human immunoglobulin M monoclonal antibody (HA-1A) in humans.

A human monoclonal antibody (HA-1A) directed against bacterial endotoxin was administered to 15 patients with incurable malignant disease. No adverse effects were noted following single intravenous infusions of 0.05 to 100 mg. Pharmacokinetics were evaluated in nine patients receiving 10 mg (n = 3), 25 mg (n = 3), and 100 mg (n = 3). Seven of these patients had initial peak serum concentrations greater than 80% of predicted values with plasma disappearance curves fitting a one-compartment system and a plasma half-life of 31.5 h (range of 20.3-44.6 h). The peak serum concentrations and area under the curve values were proportional to the dose of HA-1A administered. One patient had a hypercatabolic state with low levels of serum albumin and IgM. He achieved 65% of the predicted value for peak serum concentration of HA-1A with a plasma half-life of 12.3 h. A second patient had detectable serum HA-1A for only 15 min following infusion without an adequate technical or biologic explanation. We were unable to demonstrate antibody to HA-1A in sera from these nine patients either prior to therapy or during 28 days postinfusion using a "double-antigen" radiometric assay. This study suggests that HA-1A human monoclonal antibody administration is well tolerated by patients. Phase I trials will need to be carried out to characterize further the pharmacokinetics and toxicity of HA-1A in patients with gram-negative sepsis.

In vitro and in vivo antibacterial activities of the fluoroquinolone WIN 49375 (amifloxacin).

WIN 49375 (amifloxacin) is a synthetic antibacterial agent of the quinolone class. It is similar in chemical structure to pefloxacin but differs by containing a methylamino, rather than an ethyl, substituent at the 1-N position. The activity of WIN 49375 in vitro was comparable to those of norfloxacin and pefloxacin against Enterobacteriaceae and generally greater than those of tobramycin and cefotaxime. WIN 49375 was more active in vitro than carbenicillin and mezlocillin against Pseudomonas aeruginosa isolates and showed moderate activity against Staphylococcus aureus, with MICs of less than or equal to 2 micrograms/ml. The in vitro activity of WIN 49375 was not markedly affected by the presence of human serum, the size of the bacterial inoculum, or changes in pH between 6 and 8. Against systemic, gram-negative bacterial infections in mice, WIN 49375 was generally less active than cefotaxime but more active than gentamicin. WIN 49548, the major piperazinyl-N-desmethyl metabolite of WIN 49375, was aa effective as the parent drug against experimental infections in mice when given parenterally. When administered orally, however, this metabolite was less potent than WIN 49375. WIN 49375 was highly active by the oral route, with 50% effective doses within two- to threefold of those obtained with parenteral medication.

Novel amino-substituted 3-quinolinecarboxylic acid antibacterial agents: synthesis and structure-activity relationships.

A series of novel 3-quinolinecarboxylic acid derivatives have been prepared and their antibacterial activity evaluated. These derivatives are characterized by fluorine attached to the 6-position and substituted amino groups appended to the 1- and 7-positions. Structure-activity relationship studies indicate that antibacterial potency is greatest when the 1-substituent is methylamino and the 7-substituent is either 4-methyl-1-piperazinyl, 16, or 1-piperazinyl, 21. Derivatives 16 and 21, the 1-methylamino analogues of pefloxacin and norfloxacin, respectively, show comparable in vitro and in vivo antibacterial potency to these two known agents. The activity (vs. Escherichia coli Vogel) of 16 (amifloxacin) is the following: in vitro MIC (microgram/mL) = 0.25; in vivo (mice) PD50 (mg/kg) = 1.0 (po), 0.6 (sc).

Acetaminophen: a practical pharmacologic overview.

Acetaminophen is an effective analgesic and antipyretic agent with few adverse effects when used in recommended dosages. The drug is metabolized mainly in the liver, and the several end products have no harmful effects. An intermediate compound in a minor metabolic pathway, however, is toxic; it is normally inactivated by glutathione. In the case of an acetaminophen overdose the hepatic stores of glutathione seem to become depleted, leaving the toxic intermediate free to damage liver tissue. Such damage is unlikely to occur unless the plasma concentration of acetaminophen peaks above 150 micrograms/mL--a level far in excess of the 5 to 20 micrograms/mL achieved with therapeutic doses of the drug. Long-term therapeutic use of acetaminophen does not appear to be associated with liver damage, although some case reports suggest the possibility. Acetaminophen poisoning follows an acute overdose and, if untreated, is manifested clinically by an initial phase of nonspecific signs and symptoms, a latent period in which the liver transaminase levels rise and then, 3 to 5 days after the ingestion, signs of more serious hepatic dysfunction. Most patients do not progress beyond the first or second phase. They and those who survive the third phase recover with no residual injury to the liver. Appropriate antidotal therapy markedly reduces the severity of the initial damage.