Amplification of the amoA Gene from Diverse Species of Ammonium-Oxidizing Bacteria and from an Indigenous Bacterial Population from Seawater

Vol. 61, no. 7, p. 2705, column 2, lines 9 to 16: these sentences should read as follows. "These two sequences show 75% identity at the DNA level to the published N. europaea sequence and show 85% identity to each other. Interestingly, the regions that our primers were designed to target show 5 and 3 mismatches with the Nitrosospira sequence and 2 and 2 mismatches with the Nitrosolobus sequence for the forward and reverse primers, respectively." [This corrects the article on p. 2702 in vol. 61.].

Siggaard-Andersen algorithm-derived p50 parameters: perturbation by abnormal hemoglobin-oxygen affinity and acid-base disturbances

The p50 and derived indexes, calculated by using the Siggaard-Andersen algorithm from a single measurement of arterial blood gas tensions and hemoglobin-oxygen saturation, are used to assess tissue oxygen availability in critical illness. We tested the accuracy of the Siggaard-Andersen p50 algorithm over a wide range of pathophysiologic conditions. Blood gases, cooximetry, and calculation of standard and in vivo p50 were performed at multiple saturations, CO2 tensions, and H+ concentrations on blood with normal (standard p50 of 26.1 and 26.7 mm Hg), increased (19.0 and 25.4), and reduced (33.9 and 38.2) hemoglobin-oxygen affinity, as well as on high-affinity blood from two patients with diabetic ketoacidosis (16.7 and 20.8). Log p50 in vivo/pH plots were constructed to determine the Bohr effect. Except in the normal affinity specimens (coefficient of variation < 1.7%), standard p50 values showed high variability (coefficient of variation > 5.9%), with saturation-linked bias and distortion of the Bohr effect. Standard p50 was overestimated by up to 11 mm Hg as saturation approached 97%. Although base deficit correction of the stored specimens (6.9 < pH < 7.1) restored the Bohr effect and improved the accuracy of standard p50 calculations (coefficient of variation = 4.4% and 2.9%), saturation-linked bias persisted. We conclude that Siggaard-Andersen p50 calculations may be misleading when there are disturbances of hemoglobin-oxygen affinity and acid-base balance, owing to changes in shape of the hemoglobin-dissociation curve. When metabolic acidosis occurs with high hemoglobin-oxygen affinity, as can occur in critical illness, indexes derived by the Siggaard-Andersen algorithm on arterial blood may greatly overestimate oxygen availability.

Peri-operative administration of rectal diclofenac sodium. The effect on renal function in patients undergoing minor orthopaedic surgery

In a randomized, double-blind study, we administered placebo and diclofenac sodium 100 mg suppositories 1 h pre-operatively and on the first post-operative morning to 22 adult patients undergoing minor orthopaedic surgery. A standardized post-operative intravenous fluid regimen was instituted until oral fluids were tolerated. Renal function was assessed pre-operatively, and on the first and second post-operative days by the measurement of urine output, creatinine, urea, sodium, potassium and NAG (N-acetyl-b-D-glucosaminidase) levels and serum creatinine, urea, sodium and potassium concentrations. On the first post-operative day, the diclofenac group demonstrated a reduced urinary sodium excretion. On the second post-operative day, a reduced urinary NAG/creatinine ratio was observed in the diclofenac group when compared to placebo. We conclude that peri-operative administration of diclofenac causes changes in renal function consistent with prostaglandin inhibition on the first post-operative day but had no lasting adverse effects in this group of patients. Our results reinforce the need for caution when administering this drug in the context of pre-existing renal impairment.

Fractionation of visuoperceptual dysfunction in Parkinson's disease

There is considerable evidence that visuoperceptual function is impaired in Parkinson's disease although this view remains contentious. The issue is confounded by studies which have demonstrated impairment of visual sensation, in particular high-contrast visual acuity, in Parkinson's disease. We have measured the visuoperceptual performance of 16 patients with mild to moderate Parkinson's disease, both on and off drugs, and 16 age and sex matched control subjects on non-motor tests of visual resolution, static perception, and dynamic perception. Performance on the perceptual tasks was measured in terms of perceptual resolutions and was found impaired in the parkinsonian group. After removal of the contribution of poorer visual resolution, the overall visual perception remained impaired, although to a relatively subtle degree, such that the difference between the two groups on its static and dynamic components did not reach significance.

Amplification of the amoA gene from diverse species of ammonium-oxidizing bacteria and from an indigenous bacterial population from seawater

Because the chemolithotrophic ammonium-oxidizing bacteria are an integral component of nitrogen biogeochemistry, a sensitive and accurate method to detect this ecologically important group of microorganisms is needed. The amoA gene of these organisms encodes the active site of ammonia monooxygenase, an enzyme unique to this group of nitrifying bacteria. We report here the use of the PCR technique to detect the amoA gene from pure cultures of chemolithotrophic ammonium-oxidizing bacteria, ammonium oxidizers introduced into filtered seawater, and the natural bacterial population of an unfiltered seawater sample. Oligonucleotide primers, based on the published amoA sequence from Nitrosomonas europaea, were used to amplify DNA from pure cultures of Nitrosomonas europaea, Nitrosomonas cryotolerans, and Nitrosococcus oceanus and from bacteria in seawater collected offshore near the Florida Keys. Partial sequencing of the amplification products verified that they were amoA. These primers, used in conjunction with a radiolabeled amoA gene probe from Nitrosomonas europaea, could detect Nitrosococcus oceanus inoculated into filter-sterilized seawater at 10(4) cells liter-1. Native marine bacteria containing amoA could also be detected at their naturally occurring titer in oligotrophic seawater. Amplification of the gene for ammonia monooxygenase may provide a method to estimate the distribution and relative abundance of chemolithotrophic ammonium-oxidizing bacteria in the environment.

The effects of physostigmine on the electroretinogram in the beagle dog

The purpose of the study was to correlate electroretinogram (ERG) parameters with increasing levels of plasma, erythrocyte and ocular tissue cholinesterase inhibition using the beagle dog as a model for human neurovisual toxicity. The anticholinesterase compound physostigmine was administered at various steady-state intravenous infusion rates based on pharmacokinetic estimates of plasma and red blood cell cholinesterase inhibition. The most sensitive parameter was the b-wave amplitude of the rod response, which was significantly depressed compared to pretreatment at all levels of acute cholinesterase depression. The overall maximal ERG response demonstrated a trend of declining a- and b-wave amplitudes, which corresponded with the increased levels of cholinesterase depression, but these differences were not significant. The depression of the electroretinogram rod and cone amplitudes appeared to parallel plasma cholinesterase inhibition more closely than erythrocyte cholinesterase activity. Ocular tissue cholinesterase activity was significantly depressed in the retina (70%), cornea (60%) and dorsal rectus extraocular muscle (46%). Electroretinography may be a useful physiological tool for evaluating the ocular toxicity of certain chemicals or pharmaceuticals associated with cholinesterase biomarker activity.

Survey of antimony workers: mortality 1961-1992

The mortality of a census population and a prospective cohort of men employed on an antimony smelter in the north east of England was followed up from 1961-1992. The workers studied were exposed to a variety of agents including antimony and its oxides, arsenic and arsenic oxides, sulphur dioxide, and polycyclic aromatic hydrocarbons. The regional mortality rates were used to calculate expected deaths and a group of zircon sand workers employed on the site were used as a comparison group. For the census population of men working on the smelter before 1961 a significant increase in deaths from lung cancer was found (32 observed v 14.7 expected, P < 0.001). A similar excess was seen among maintenance men (12 observed v 5.3 expected P = 0.016). No such excess was found in the cohort recruited after 1960 (5 observed v 9.2 expected, maintenance workers 3 observed v 2.8 expected). There was evidence of a minimum latency period of around 20 years between first exposure and death from lung cancer. No evidence was found for a correlation between length of time worked and mortality from lung cancer. The results show that an increased risk of lung cancer existed in the workers employed before 1961, but it was not possible to attribute this excess to any particular agent. Mortality analysed by five year calendar periods of first exposure show a lessening of effect after 1955. Although the power of the study is clearly less for more recent periods of exposure the absence of any excess in the population after 1960 is encouraging.

A comparison of three induction agents in paediatric anaesthesia--cardiovascular effects and recovery

We studied 30 children undergoing circumcision randomly allocated to receive either thiopentone 4 mg.kg-1, propofol 2.5 mg.kg-1 or midazolam 0.5 mg.kg-1 (n = 10) IV over 30 seconds at induction of anaesthesia. Blood pressure and pulse rate during the first 15 minutes of induction were recorded by a Finapres 2300e and a Cardiocap CM-104, and changes from preinduction baseline compared between the three induction agents and the two recording instruments. Postoperatively, blood levels of the induction agents were measured and recovery from anaesthesia was assessed by clinical criteria, mood and sedation scores and psychomotor performance. The Cardiocap data revealed no statistically significant haemodynamic differences between the three induction agents. Finapres data demonstrated that propofol caused a greater decrease in mean arterial pressure when compared to thiopentone at one minute (P = 0.01) and the MAP remained significantly lower than midazolam at five minutes (P = 0.02), illustrating an advantage of continuous over intermittent non-invasive blood pressure monitoring. The midazolam group took longer to identify themselves compared to both the propofol (P = 0.005) and the thiopentone groups (P = 0.02), but there was no difference in the groups in time to eye-opening. Psychomotor performance on awakening was significantly worse in the midazolam group compared to the propofol (P < 0.03) and thiopentone groups (P < 0.02). Most children had recovered to 80% of their best, practised, unmedicated, preoperative performance four hours after awakening, irrespective of the induction agent administered. Drug blood levels correlated weakly with both methods of psychomotor assessment (r > or = 0.6). Of the three induction agents, thiopentone caused the least haemodynamic perturbation on induction, and anaesthesia induced with midazolam caused the greatest psychomotor impairment on awakening. Within one hour patients in all drug groups were equally awake, co-operative and co-ordinated.

Effects of atropine in the beagle dog measured by quantitative electroencephalography and regional cortical analysis

A treatment-by-subjects design was used to identify and characterize quantitative electroencephalography (qEEG) changes, at rest and under stimulus conditions, in Beagle dogs given 3 dose levels of atropine sulfate. In general, total power, absolute delta and theta amplitudes increased, while relative beta contribution and spectral frequency 90 decreased, as increased levels of atropine were administered. Regional analysis of this qEEG dataset suggests cortical mapping and contour plot imaging can be done in the dog. Through statistical analysis and visual evaluation of regional patterns may be more acceptable for interpretation in regulatory toxicology studies until normative databases are developed.

Premedication with oral midazolam in children--an assessment of psychomotor function, anxiolysis, sedation and pharmacokinetics

We studied 30 children, aged 4 to 12 years, undergoing elective circumcision, premedicated with midazolam 0.5 mg.kg-1 and atropine 0.02 mg.kg-1 by mouth. A modified postbox test and the coding component of the Wechsler intelligence scale (WISC-R) was used to assess the preoperative effect of premedication on psychomotor function. Mood and sedation were also scored and related to serum midazolam concentrations. The children showed a significant decline in psychomotor performance 30 and 60 minutes after premedication when compared with their best unmedicated performance recorded the previous evening. This decline in psychomotor performance was only weakly associated with serum midazolam concentrations (r = 0.1). The postbox toy ratio is a suitable measurement of psychomotor performance in children because of its simplicity and ease of use in the clinical environment, although it may suffer the "test-retest" limitations of similar types of assessment. The sedative and anxiolytic effects of midazolam provide a quiet environment for a smooth induction of anaesthesia.

A patient's experience of a new post-operative patient-controlled analgesic technique

A patient underwent major spinal surgery, twice within a 3 week period. On the first occasion his post-operative pain was managed by conventional morphine patient-controlled analgesia (PCA). After the second procedure his pain was managed by a patient-controlled computer-assisted titration of alfentanil. This provided the opportunity to compare the efficacy of these two drug regimens in the same subject. The results showed comparable quality of analgesia and sedation and similar effects on respiration. However, the patient expressed a preference for morphine PCA.

A quantitative electroencephalographic method for xenobiotic screening in the canine model

A method, using quantitative electroencephalography (qEEG), was developed for screening xenobiotics in conjunction with neurological examinations, for defining toxicodynamic profiles of certain drugs and chemicals in the dog. The standard 10-channel montage was used to evaluate normotonic, auditory, visual, and somatosensory cortical activity. Compressed spectral analysis and Fourier Transformation determined spectral edge frequencies, distribution of the total, fractional and absolute powers of delta, theta, alpha, and beta frequencies as parameters. The alpha 2-agonist, xylazine, was used to detect treatment-related differences, threshold effect levels, and qEEG-target parameters. An increase in theta and alpha activity, and a shift to lower spectral edge frequency were noted. Visual stimulation was the least sensitive test condition in detecting significant changes in measured parameters. Data derived by qEEG may make a reliable contribution to the physiologic interpretation, along with biochemical, clinical, and pathological data collected during a regulatory study.

The effect of premedication on oxygen saturation during the post-premedication period in 20 Chinese children undergoing elective surgery

Peri-operative continuous pulse oximetric data were studied in healthy Chinese children randomly allocated to receive either pethidine 1 mg kg-1 and atropine 0.02 mg kg-1 intramuscularly 90 min prior to surgery (n = 10), or midazolam 0.5 mg kg-1 and atropine 0.02 mg kg-1 orally, 120 min before surgery (n = 10). Data were collected during the night before surgery, after premedication and for 8 h post-operatively. The pulse oximeter (Nellcor N-200E) output was retrospectively evaluated using Satmaster, a computer programme which permits storage, retrieval, signal evaluation and compilation of oximetric data. There was no significant difference in the frequency, duration, or magnitude ofdesaturation episodes recorded during the post-premedication period compared to the desaturation episodes which occurred in the same child during normal sleep, on the night before surgery. Furthermore, there was no significant difference in the desaturation data between the two premedicant regimens. No child recorded a genuine desaturation less than 80% for longer than 15 s at any time during the study. Neither regimen significantly depressed saturation in otherwise healthy children presenting for minor surgical procedures.

Bioavailability and pharmacokinetics of metoclopramide in cattle

The bioavailability of metoclopramide was investigated in three steers following administration of 8 mg/kg by the oral, abomasal (cannula), and intravenous routes, using a Latin square design. The mean (+/- SD) oral and abomasal bioavailabilities were 51.3 +/- 30.7% and 76.2 +/- 15.5%, respectively. The mean value for clearance (Cl) was 20.1 +/- 5.9 ml/min and the volume of distribution (Vd) was 0.51 +/- 0.19 l/kg. Additional pharmacokinetic parameters for metoclopramide were determined following intravenous administration to seven cows. A predominate two-compartment model of distribution was found in six cows with a t 1/2 alpha harmonic mean of 24.2 min and a range of 11.2-72.4 min, a t 1/2 beta harmonic mean of 53.1 min and a range of 31.1-134.1 min, a Cl of 42.2 +/- 8.7 ml/min, and a Vd of 2.1 +/- 0.8 l/kg. To better define the relationship between metoclopramide concentration and release of prolactin, a treatment-by-subjects infusion study was conducted in which four different loading doses followed by constant infusion were used. A steady-state metoclopramide concentration (MCPss) of 8.8 +/- 2.6 ng/ml was associated with a three-fold elevation of prolactin to a mean value of 12.1 +/- 3.1 ng/ml in six yearling steers. Steady state serum prolactin concentrations (PRLss) did not rise significantly above 23.3 +/- 6.9 ng/ml, even when MCPss reached a concentration of 518.5 +/- 151.2 ng/ml. The short half-life, moderate Vd, low minimum pharmacologically effective concentration, and rapid Cl found for metoclopramide in cattle in this study, suggest that a continuous release device could potentially be useful in the application of this drug in the prevention and treatment of fescue toxicosis.

Use of two oximeters to investigate a method of movement artefact rejection using photoplethysmographic signals

Oxygen haemoglobin saturations and plethysmograph signal amplitudes were recorded from two oximeters placed on the fingers and toes of 10 patients undergoing oesophagectomy, to assess a method of removing motion artefact from saturation recordings. By examining changes in the plethysmograph amplitude that preceded changes in saturation, episodes of desaturation caused by movement artefacts were removed from the data. The reliability of the method was then determined by scrutinizing two concurrent oximetric profiles from each patient. A total of 1600 h of data were evaluated. Desaturations occurring contemporaneously in both oxygen saturation profiles were presumed genuine, whereas a desaturation occurring in only one of the profiles was classified as artefactual. Our method had a sensitivity of 96%, a positive predictive power of 98% and a specificity of 60%. We modified the method to increase specificity and re-evaluated our data. We found that a useful increase in specificity was associated with a considerable decline in sensitivity.

Preoperative and postoperative oxygen saturation in the elderly following spinal or general anaesthesia--an audit of current practice

We have compared the incidence of preoperative and postoperative oxygen desaturation in 20 elderly patients undergoing dynamic hip screw insertion for fractured neck of femur, allocated randomly to two groups to receive subarachnoid anaesthesia (SA, n = 10) or a general anaesthetic (GA, n = 10). Oximetry data were recorded during the preoperative night and the first 48 hours after surgery using Satmaster. Data associated with zero amplitude signal were automatically invalidated by the software and decreases in SpO2 which were preceded by contemporaneous changes in signal amplitude which conformed to a previously described template were assumed to be artefactual and were discarded from final data analysis. Data demonstrated a wide interpatient variability. However, those patients who desaturated preoperatively continued to do so in the postoperative period. The differences between the preoperative and postoperative oximetry profiles were examined for each patient and demonstrated a significantly longer time spent with SpO2 < 90% in the GA group compared with the SA group, in all the recorded time periods, except on the day of surgery. The SA group showed an improvement in oxygen saturation postoperatively when compared to the preoperative night, spending less time with an SpO2 < 85%. We conclude that the subarachnoid anaesthetic technique was associated with a lower incidence of postoperative oximetry desaturation when compared with general anaesthetic for these elderly patients undergoing repair of fractured neck of femur.

A central executive deficit in patients with Parkinson's disease

Eight patients with Parkinson's disease and eight matched controls were tested for concurrent task performance to examine whether Parkinson's disease produces deficits in the coordinating and integrating function of the central executive component of Baddeley's working memory model. Consistent with this prediction, the patients showed a significant decline in performance on a random pursuit tracking task while recalling digit span forward sequences, whereas the controls showed no such change. Performance on the component pursuit and digit span tasks, which did not differ between groups, was equated across subjects by varying the size of a target square and by using individual subjects' digit spans. The patient group also produced poorer word fluency scores and reported higher levels of depression, but there was no significant impairment on the Wisconsin card sort test. There was no association between dual task performance and any psychometric measure, target size, or disease related variables. Baddeley's working memory model is advantageous in providing a rich conceptual basis to explore and characterise cognitive abilities in patients with Parkinson's disease.

An electroretinogram protocol for toxicological screening in the canine model

A five-step electroretinogram protocol was developed for the dog to be used as a painless screening test for ocular effects of drugs or pesticides. Standard conditions of frequency band width, stimulus intensity, dark adaptation time and non-confounding anesthesia method were selected to allow analysis of wave components. The protocol demonstrated an acceptable level of inter-subject variability for compiling an age appropriate database, and for the detection of possible retinal component toxicities in chronic dog studies. This electrophysiologic procedure may serve to corroborate biochemical, clinical and pathology data, in establishing a compound's no-observable-effect-level (NOEL).

A multistage system to detect epileptiform activity in the EEG

A PC-based system has been developed to automatically detect epileptiform activity in sixteen-channel bipolar EEG's. The system consists of three stages: data collection, feature extraction, and event detection. The feature extractor employs a mimetic approach to detect candidate epileptiform transients on individual channels, while an expert system is used to detect focal and nonfocal multichannel epileptiform events. Considerable use of spatial and temporal contextual information present in the EEG aids both in the detection of epileptiform events and in the rejection of artifacts and background activity as events. Classification of events as definite or probable overcomes, to some extent, the problem of maintaining high detection rates while eliminating false detections. So far, the system has only been evaluated on development data but, although this does not provide a true measure of performance, the results are nevertheless impressive. Data from 11 patients, totaling 180 minutes of sixteen-channel bipolar EEG's, have been analyzed. A total of 45-71% (average 58%) of epileptiform events reported by the human expert in any EEG were detected as definite with no false detections (i.e., 100% selectivity) and 60-100% (average 80%) as either definite or probable but at the expense of up to nine false detections per hour. Importantly, the highest detection rates were achieved on EEG's containing little epileptiform activity and no false detections were made on normal EEG's.

Simultaneous determination of flumazenil, midazolam and metabolites in human biological fluids by liquid chromatography

A simple procedure for the simultaneous determination of flumazenil, midazolam, 1-hydroxymethylmidazolam and 4-hydroxymidazolam in plasma or urine in surgical patients is described. The assay involves a preliminary extraction of the drugs, metabolites and internal standard (flurazepam) from biological fluid into an organic solvent mixture (dichloromethane-diethyl ether, 40:60 v/v). The extract was evaporated to dryness at 40 degrees C under a gentle stream of nitrogen. The residue was re-dissolved in distilled methanol (80 microliters) and a 30-microliters aliquot was injected via an automatic sampler into the liquid chromatograph and eluted with the mobile phase (32% acetonitrile in 0.004 M sodium hydrogenphosphate buffer containing 1 ml of triethylamine and adjusted to pH 7.2) at a flow-rate of 1.5 ml/min on a 30-microns C8 precolumn linked to a 4-microns Nova-pak C18 cartridge column (100 mm x 8 mm I.D.) at ambient temperature (25 degrees C). The eluate was detected at 220 nm.

Changes in the radiation treatment of cancer of the anus in Glasgow

The survival and complication rate of two groups of patients with carcinoma of anus were compared. The first group of 20 patients were treated between 1974 and 1983 by double plane implantation using radium or equivalent caesium needles and supplementary external beam radiotherapy to groin nodes if present. The second group of 26 patients were treated between 1984 and 1990 by external beam radiotherapy followed by a jig implant using afterloading iridium needles. 5-year survival was superior in the second group (73% vs. 40%) with a lower incidence of radiation-induced complications.

Identification of metoclopramide metabolites in the urine of cattle by gas chromatography-mass spectrometry and high-performance liquid chromatography-photodiode array detection

The urinary metabolites of metoclopramide (4-amino-5-chloro-N-[2-diethylaminoethyl]-2-methoxybenzamide) were identified in cows. The drug was administered intravenously, voided urine was collected, and individual urine extracts were analysed by gas chromatography-mass spectrometry and high-performance liquid chromatography-photodiode array detection. The parent compound and one major metabolite (4-amino-5-chloro-N-[2-(ethylamino)ethyl]-2-methoxybenzamide) were common to all individuals. In addition to the parent and major metabolite, a second, minor metabolite was identified in two cows as 4-amino-5-chloro-N-[2-(diethylamino)ethyl]-2-hydroxybenzamide. The identity of the minor metabolite was confirmed by comparison with a standard synthesized by a new method. Metabolite identification and characterization in food animal species allows the design of safety and environmental impact studies and relative metabolite ratios between dose treatment groups.

The Finapres 2300e finger cuff. The influence of cuff application on the accuracy of blood pressure measurement

Blood pressure measurements associated with malapplication of a finger cuff were compared with contemporaneous intra-arterial pressure data in seven volunteers to determine the influence of cuff application on the accuracy of the Finapres 2300e. Systolic readings in all cuff positions differed from arterial line data by more than the recommended standard and tight and loose cuff applications under and over-read respectively, in all subjects. The results show the Finapres to be sensitive to small degrees of finger cuff malapplication which contribute to the bias on direct arterial comparison and limit the reliability of the instrument in clinical practice.