Denitrification and dissimilatory nitrate reduction to ammonium (DNRA) in a temperate re-connected floodplain.

The relative magnitudes of, and factors controlling, denitrification and dissimilatory nitrate reduction to ammonium (DNRA) were measured in the soil of a re-connected temperate floodplain divided into four different land management zones (grazing grassland, hay meadow, fritillary meadow and a buffer zone). Soil samples were collected from each zone to measure their respective potentials for nitrate attenuation using 15N both at the surface and at depth in the soil column and additional samples were collected to measure the lability of the organic carbon. Denitrification capacity ranged between 0.4 and 4.2 (µmol N g(-1) dry soil d(-1)) across the floodplain topsoil and DNRA capacity was an order of magnitude lower (0.01-0.71 µmol N g(-1) d(-1)). Land management practice had a significant effect on denitrification but no significant effects were apparent for DNRA. In this nitrogen-rich landscape, spatial heterogeneity in denitrification was explained by differences in lability and the magnitude of organic carbon associated with different management practices (mowing and grazing). The lability of organic carbon was significantly higher in grazing grassland in comparison to other ungrazed areas of the floodplain, and consequently denitrification capacity was also highest in this area. Our results indicate that bacteria capable of DNRA do survive in frequently flooded riparian zones, and to a limited extent, compete with denitrification for nitrate, acting to retain and recycle nitrogen in the floodplain. Exponential declines in both denitrification and DNRA capacity with depth in the floodplain soils of a hay meadow and buffer zone were controlled primarily by the organic carbon content of the soils. Furthermore, grazing could be employed in re-connected, temperate floodplains to enhance the potential for nitrate removal from floodwaters via denitrification.

Poor sensitivity of routine fetal anomaly ultrasound screening for antenatal detection of atrioventricular septal defect.

OBJECTIVE: To report the antenatal detection rate in a consecutive series of liveborn infants with atrioventricular septal defect (AVSD). DESIGN: Review and analysis of referrals for detailed fetal echocardiography and postnatal diagnosis of AVSD. SETTING: Tertiary referral centre for congenital heart disease centre with data prospectively collected between 1996 to 2001. RESULTS: 92 consecutively liveborn infants with AVSDs were identified of which 27 (29%) were detected by routine obstetric antenatal ultrasound. The antenatal diagnosis rate was worse for liveborn infants with trisomy 21 (12 of 49 (25%) v 15 of 43 (35%) chromosomally normal children) and for infants with AVSD without other structural heart disease (18 of 74 (24%) v 9 of 18 (50%) infants with associated structural heart disease). CONCLUSION: Despite the potential ability of fetal ultrasound to detect AVSDs, the antenatal diagnosis rate is poor. This is particularly true for infants with trisomy 21 and is of importance when counselling parents with an apparently normal fetal ultrasound scan.

Sediment nutrient characteristics and aquatic macrophytes in lowland English rivers.

Aquatic macrophytes play an important role in the nutrient dynamics of streams. As a result, there is much interest in their use as trophic indicators. However, the relationship between aquatic macrophytes and the trophic status of rivers is a complex one, partly because of the effects of a wide range of environmental variables and partly because submerged, rooted macrophytes can absorb nutrients from the river sediments and/or the water column. Experiments which have tried to establish the relative importance of sediments or water as sources of nutrients are inconclusive and further work is needed to establish how sediment nutrient characteristics vary within and among rivers (spatially and temporally) and the inter-relationships between sediment nutrients, water column chemistry and macrophytes. This paper presents the initial findings from a study of 17 lowland rivers in southern England which is exploring the spatial variability of sediment characteristics (total and inorganic phosphorus, total nitrogen, organic carbon, silt-clay fraction and organic matter content) and the relationship with aquatic macrophytes. The preliminary analysis indicates that although sediment characteristics are highly variable within 100-m river reaches, the variability across the 17 rivers is even greater; this is despite the limited geographic and trophic range of the study sites. The results presented in this paper also give some indication of the sediment characteristics associated with five macrophyte species but it is too early to ascribe sediment preferences for particular species.

Efficacy of treatment of inflammatory cytologic abnormalities detected by papanicolaou smears: a pilot study.

OBJECTIVE: To evaluate the efficacy of metronidazole versus no treatment for the empiric treatment of inflammatory cytologic changes. MATERIALS AND METHODS: Patients with inflammatory changes on Pap smear were serially assigned to receive no treatment or metronidazole by one of three regimens: 2 grams orally as a single dose, 500 milligrams orally twice daily for 7 days, or 5 grams (in gel form) vaginally twice daily for 5 days. Smears were repeated 3 months after treatment. RESULTS: The repeat smear was normal in 47 of 63 patients treated with a single dose, 40 of 62 patients treated orally for 7 days, 14 of 21 patients treated with vaginal gel, and 29 of 49 of the control group. Chi-square analysis showed no statistical significance between groups. CONCLUSION: There is no statistically significant difference in the resolution of cytologic inflammatory changes among the study groups. Empiric metronidazole treatment has no benefit.

Dystrophic calcification of the fetal myocardium.

Intramural cardiac masses were detected antenatally in three fetuses by echocardiography. The masses were initially thought to be rhabdomyomas. All three pregnancies were terminated and histology showed dystrophic calcification in all, with no evidence of tumour. Therefore, dystrophic calcification of the fetal myocardium may have a similar appearance to single or multiple rhabdomyomas. This should be considered when counselling parents after detection of masses in the fetal heart, particularly when considering the risk of associated tuberous sclerosis.

Assessing the sequence specificity in the binding of Co(III) to DNA via a thermodynamic approach.

The interaction specificities of Co(III) with DNA were investigated via consideration of thermodynamic characteristics of the duplex to single strand transition for DNA oligomers incubated in the presence of [Co(NH3)5(OH2)](ClO4)3. It has previously been demonstrated that incubation of the DNA oligomer [(5medC-dG)4]2 with this cobalt complex leads to coordination of the cobalt center to the DNA, presumably at N7 of guanine bases [D. C. Calderone, E. J. Mantilla, M. Hicks, D. H. Huchital, W. R. Murphy, Jr. and R. D. Sheardy, (1995) Biochemistry 34, 13841]. In this report, DNA oligomers of different sequence were incubated with [Co(NH3)5(OH2)](ClO4)3 via protocols developed previously and the treated oligomers were subjected to thermal denaturation for comparison to the untreated oligomers. The DNA oligomers were designed in order to investigate the sequence specificity, if any, in the reaction of the cobalt complex with DNA. The values of Tm, delta HvH, and delta n (the differential ion binding term) obtained from the thermal denaturations were used to assess the sequence specificity of the interaction. For all oligomers, treated or untreated, Tm and delta HvH vary linearly with log [Na+] and hence the value of delta n is a function of the Na+ concentration. The results indicate no significant reaction between the cobalt complex and oligomers possessing isolated -GA- or -CG- sites; however, the thermodynamic characteristics of DNA oligomers possessing either an isolated -GG- site or an isolated -GC- site were altered by the treatment. Atomic absorption studies of the treated oligomers demonstrate that only the DNA oligomers possessing isolated -GG- or -GC- sites bind cobalt. Hence, the changes in the thermodynamic properties of these oligomers are a result of cobalt binding with a remarkable sequence specificity.

Age of learning affects rate-dependent processing of stops in a second language.

The aim of this study was to assess the effect of speaking rate changes on the perception of English stop consonants by four groups of subjects: English and Spanish monolinguals, 'early' Spanish/English bilinguals who learned English in childhood, and 'late' bilinguals who learned English in adulthood. Subjects identified, and then later rated for goodness as exemplars of the English /p/ category, the members of two voice onset time (VOT) continua. The English monolinguals identified a well-defined range of VOT stimuli as English /p/, and stimuli with longer VOT values as 'exaggerated' instances of English /p/. Their goodness ratings increased as VOT increased, then showed a systematic decrease as VOT began to exceed values typical for English /p/. The English monolinguals' goodness ratings also varied systematically as a function of speaking rate, which was simulated in the two continua by varying syllable duration. The Spanish monolinguals, on the other hand, failed to consistently identify any of the stimuli as English /p/. Although speaking rate influenced their goodness ratings, the Spanish monolinguals' rate effects differed significantly from the English monolinguals'. The early bilinguals resembled the English monolinguals, and differed from the Spanish monolinguals to a greater extent than did the late Spanish/English bilinguals. This was taken as support for the hypothesis that early bilinguals are more likely than are late bilinguals to establish new phonetic categories for stop consonants in a second language.

Temporal differences in praziquantel- and oxamniquine-induced tegumental damage to adult Schistosoma mansoni: implications for drug-antibody synergy.

A temporal study of the effects on the tegument of Schistosoma mansoni adult worm following in vivo praziquantel and oxamniquine treatment was performed. Drug-induced damage to the tegument, exposure of surface antigens and attachment of host antibody occurred rapidly, within 1 h, following praziquantel treatment. Oxamniquine-treated worms required 4-8 days for these effects to be apparent. The 2 drugs differed in the degree and sites of damage on the worm surface. The administration of 2 different polyspecific rabbit sera with drug significantly increased the efficacy of praziquantel when administered with the drug, but not when given 6-9 days after drug treatment. In contrast, only 1 serum was synergistic with oxamniquine when administered with drug and both sera were synergistic when given 6-9 days after drug treatment. The effect of immune killing of drug-treated worms is discussed.

Transoesophageal echocardiography in neonates, infants and children: applicability and diagnostic value in everyday practice of a cardiothoracic unit.

OBJECTIVE: To determine the applicability of and information obtained by transoesophageal echocardiography in neonates, infants, and children in every day practice of a cardiothoracic unit. DESIGN: Four month prospective study. SETTING: Supraregional centre for paediatric cardiothoracic services. PATIENTS AND METHODS: 58 patients aged between four days and 16 years with a wide range of cardiovascular disease underwent transoesophageal echocardiography under sedation or general anaesthetic. One of two paediatric probes (6 or 7 mm diameter), or an adult probe (13 mm in diameter) was used. Whenever possible the investigation was immediately preceded by precordial echocardiography. MAIN OUTCOME MEASURES: Success, failure, technical difficulties, and complications of probe introduction and, when possible, comparison of the information obtained with that obtained from precordial echocardiography. RESULTS: Introduction of the probe was successful in 57 of the 58 patients. The only complication encountered was transient bradycardia during manipulation of the probe in a 2.2 kg baby. The adult (13 mm) probe was successfully used in children as small as 7.0 kg. Below this weight a smaller paediatric probe was required. In 56% of cases transoesophageal ultrasound provided information not obtained from the precordial approach. The technique was of particular value perioperatively and in the immediate postoperative period in neonates and infants and in the presence of valve prostheses and the investigation of mediastinal tumours in older children. CONCLUSIONS: Transoesophageal echocardiography is a valuable additional investigative tool for children of all ages. It is of particular value when acquisition of precordial image is impaired around the time of and after operation and in children with prosthetic valves or mediastinal tumour. Image quality was superior with the adult probe and we recommend the use of this probe unless the patient's weight is below 7 kg, when a paediatric probe allows this technique to be used usefully and safely in babies as small as 2.2 kg.

Continuous wave Doppler echocardiography after surgical repair of coarctation of the aorta.

OBJECTIVE: To find how closely pressure gradients across the aortic arch derived from Doppler echocardiography reflect gradients measured by catheter after surgical repair of coarctation of the aorta. DESIGN: Pressure drop across the aortic arch was measured simultaneously by continuous wave Doppler and double lumen catheter in 20 patients with repaired coarctation of the aorta. RESULTS: The peak pressure drop estimated by Doppler was almost invariably higher than the peak to peak gradient measured by catheter, as might be expected. Wide variation was seen between the Doppler measured pressure drop and instantaneous peak gradient measured by catheter, ranging from +22 to -17 mm Hg. The reasons for these differences are unclear but are probably related to a combination of complex flow dynamics in the aortic arch, difficulty in closely aligning the Doppler beam with flow, and inability to measure flow velocity immediately proximal to the site of the surgical repair with continuous wave Doppler. CONCLUSIONS: Continuous wave Doppler echocardiography may significantly overestimate or underestimate the pressure drop after repair of coarctation and it should be interpreted with caution in individual patients. Catheterisation with angiography remains the reference standard for assessment of surgical repair of the aortic arch.

Left atrial clot in patients with mitral prostheses: increased rate of detection after recent systemic embolism.

We studied 70 patients with mitral valvar replacements by both transthoracic and transoesophageal echocardiography. Fifteen subjects had recently suffered a suspected embolic episode. The remainder (55) were studied for other clinical reasons. Transthoracic echocardiography demonstrated thrombus in only 1 of the 70 patients. By contrast, transoesophageal examination revealed thrombus in 8 out of 15 patients with recent suspected embolism and 3 out of 55 without. Thrombus was most commonly seen in patients with biological valvar prostheses whose anticoagulation had been discontinued. When patients with prosthetic mitral valves present with a suspected embolic episode, transoesophageal echocardiography is strongly recommended. This study also suggests that transoesophageal echocardiography may be useful for evaluating patients with biological valves if anticoagulation is withdrawn so as to identify formation of thrombus at the earliest possible stage.

Failure of Doppler ultrasound to detect coarctation of the aorta.

Normal velocities of flow in the aortic arch were recorded in a patient presenting with clinical signs of aortic coarctation. Angiography demonstrated complete coarctation with extensive collateral supply to the descending aorta: there was a systolic pressure difference of 40 mm Hg between the ascending and descending segments of the aorta. Despite reports of the value of Doppler ultrasound in the diagnosis of coarctation, the finding of normal velocities of flow within the aortic arch does not necessarily exclude the presence of an obstructive lesion.

The value of transesophageal echocardiography in the investigation of acute prosthetic valve dysfunction.

When patients present with suspected prosthetic valve dysfunction, investigation is usually instituted to delineate the site and cause thereof. Precordial cross-sectional echocardiography is often helpful in this respect, but in the patient with acute pulmonary edema, imaging may be impaired because of discomfort and respiratory distress. The information obtained may also be suboptimal as a result of concomitant obesity, chest wall deformity, and pulmonary disease. In addition, further difficulties may relate to the acoustic shadowing produced by the metallic portion of the valve and its sewing ring, especially with valves in the mitral position. In such patients, cardiac catheterization may cause further decompensation and is associated with a recognized increase in morbidity and mortality. Angiography does not accurately site regurgitant jets in relation to the prosthetic valve concerned and will not detect the presence of vegetations. Transesophageal echocardiography circumvents many of these imaging difficulties and we evaluated its use in five patients with prosthetic heart valves who presented acutely ill, in severe pulmonary edema and suspected prosthetic heart valve failure. In each case, the diagnosis of valve dysfunction was established, and precise information regarding the site and cause of the failure was obtained. No complications or deterioration in patient condition resulted from the procedure and the findings were confirmed at surgery performed within 24 hours in all five patients. Transesophageal echocardiography should be included in the assessment of acute prosthetic heart valve failure.

Lower extremity telescopic orthosis for immediate fitting in paraplegia.

For initial gait training with the paraplegic patient, a lower extremity telescoping orthosis has been developed. This brace eliminates the time-consuming fabrication, considerable weight, and cumbersome use of conventional knee-ankle-foot orthoses and is easily adjustable to a wide range of patients. Particularly during the early phase of rehabilitation, this brace offers significant advantages to the patient with lower extremity disabilities.

Reproducibility and persistence of abnormal transmitral flow velocity patterns detected by pulsed Doppler ultrasound.

This prospective study examines the reproducibility and persistence of abnormal transmitral flow detected using pulsed Doppler ultrasound on 2 separate occasions between 2 days and 6 weeks apart. The 22 patients included were accepted consecutively from those having an abnormal diastolic flow pattern at initial examination. Abnormal flow velocity patterns were defined as those exhibiting reversal of the ratio of the passive filling velocity (E) and active atrial transport velocity (A). There was no significant difference between the separately recorded values for the ratio of the peak E and A velocities or of the ratio of the planimetered areas beneath each of the velocity waves, with positive correlations for both sets of values (r = 0.68, r = 0.67). Significant positive correlation also existed between the mean rates of acceleration to each of the E and A velocity peaks of the transmitral waveform recorded on separate occasions (r = 0.68, r = 0.95). Interobserver variation for the analysis of hard-copy pulsed Doppler recordings between two trained observers was less than 5% and intraobserver error for recording analysis was less than 2% for both observers. Abnormal transmitral flow velocity patterns persist unchanged in the absence of therapeutic intervention and the acceptably small observer error in the recording and analysis of such flow patterns allows consistent and clinically reliable data to be obtained.

Doppler ultrasound of normally functioning mechanical mitral and aortic valve prostheses.

Doppler ultrasound flow velocities across clinically normally functioning mitral (Bjork-Shiley, Medtronic Hall, Lillehei-Kaster, Duromedic and Starr-Edwards) and aortic (Bjork-Shiley, Medtronic Hall, Lillehei-Kaster and Duromedic) valve prostheses are described. To enable ease of reference for the echocardiographer and to avoid the need for time-consuming calculations of pressure drops and effective valve orifice areas, peak flow velocities and, where relevant, pressure half times across valves of different types and sizes are tabulated. In the mitral position, there was significant negative correlation between peak velocity and valve size and between pressure half time and valve size only when a large number and a wide range of sizes of a given type of mitral prosthesis was studied. Similarly, there was significant negative correlation between peak velocity and aortic valve size for Bjork-Shiley and Duromedic valves. Regurgitant jets were detected across 18.4% of mitral and 42% of aortic prostheses.

Doppler echocardiographic characteristics of the Carpentier-Edwards xenograft.

In order to define ranges of normal velocities for the Carpentier-Edwards xenograft, 38 mitral, 24 aortic and 9 tricuspid prostheses were studied with pulsed or continuous wave Doppler at a mean interval of 38 months following surgery. All patients had clinically normal prosthetic valve function and no clinical or radiographic signs of heart failure. Mean peak velocity across aortic prostheses was 244 cm s-1 (SD 48). There was weak correlation (r = 0.54, P less than 0.01) between peak velocity and time since valve implantation, but no significant difference in peak velocity across valves of different size. In the mitral position, mean peak velocity was 164 cm s-1 (SD 24) and mean pressure half time 90 ms (SD 23). There was again no significant difference between valves of different size. There was a weak correlation between pressure half time and time since implantation (r = 0.44, P less than 0.01), but there was no relationship between the latter and peak velocity. In the tricuspid position, mean peak velocity was 150 cm s-1 (SD 12) and mean pressure half time 163 ms (SD 50). The Doppler indices of obstruction to blood flow for prostheses in the mitral and aortic positions showed a significant increase with time after implantation.

Behavioral effects of mid-pregnancy administration of lidocaine and mepivacaine in the rat.

Sperm-positive female Long-Evans hooded rats were injected with 6 mg/kg lidocaine (with epinephrine), 6 mg/kg mepivacaine, or saline, into the masseter muscle of the jaw on Day 11 of gestation. Birth, growth, and litter composition were unaffected by the drug treatment, as was shuttle box acquisition. Offspring of drug-treated dams had longer latencies than controls on the first day of negative geotaxis training, and were more sensitive to electric footshock. Lidocaine-dosed offspring responded less in the presence of the correct cue in the visual discrimination task, and mepivacaine-dosed animals were hypoactive in the open field. In a second study, offspring of lidocaine-dosed dams were slower to develop the righting reflex, made more errors in acquiring a water maze, had longer suppression times in a conditioned suppression task, and had longer latencies in the tail flick test. Dosing had no effect upon birth and growth, shuttle box, or footshock sensitivity. These data demonstrate that midgestational exposure to lidocaine or mepivacaine at a dose near the limits of permissible human exposure produces significant behavioral changes in the offspring. This preliminary study suggests that development of some portion of the central nervous system is altered by such exposure. Further work is required to determine the parameters and the extent of the effect.