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Biomedical subjects

J E Brown

Publications and source records attributed to J E Brown.

At least 19 recordsLinked to original sources
PubMed2006

The derivation of radionuclide transfer parameters for and dose-rates to an adult ringed seal (Phoca hispida) in an Arctic environment.

Radionuclide transfer parameters and dose-rates for an adult ringed seal from Svalbard have been determined based on empirical and estimated tissue activity concentrations and detailed dietary and habitat information. Whole-body equivalent concentration factors determined for anthropogenic radionuclides ranged from 10(1) ((90)Sr) to 10(2) ((137)Cs, (238)Pu and (239,240)Pu), while natural radionuclides ranged from 10(2) ((210)Pb) to 10(4) ((210)Po). Employing a dietary composition of 40% fish, 40% zooplankton and 20% benthic invertebrates, a whole-body biological half-life of 29 days was derived for (137)Cs. A total dose-rate of approximately 0.19microGyh(-1) (1.7mGya(-1)) was derived for an adult ringed seal; this dose-rate is virtually entirely attributable to the internal components of (210)Po and (40)K. The dose-rates associated with the presence of anthropogenically derived radionuclides in the present assessment fall many orders of magnitude below the dose-rates at which any biological effects would be expected.

Animals↗
PubMed2006

Soil-dependent uptake of 137Cs by mushrooms: experimental study in the Chernobyl accident areas.

The influence of agrochemical properties of forest soils and growth conditions on 137Cs aggregated transfer factors from soil to different species of forest mushrooms have been analysed. Statistically significant correlations between 137Cs soil to mushroom aggregated transfer factors and agrochemical soil properties have been revealed. The experimental data show that 137Cs aggregated transfer factors depend on the mushroom's trophic group, biological family, genus and species. They also strongly depend on forest soil properties and their values can be estimated with the use of multiple regression equations constructed from agrochemical soil parameters which most closely correlate with the 137Cs transfer parameters for particular mushroom groups.

Agaricales↗
PubMed2006

Development of a methodology for assessing the environmental impact of radioactivity in Northern Marine environments.

The requirement to assess the impacts of radioactivity in the environment explicitly and transparently is now generally accepted by the scientific community. A recently developed methodology for achieving this end for marine ecosystems is presented within this paper. With its clear relationship to an overarching system, the marine impact assessment is built around components of environmental transfer, ecodosimetry and radiobiological effects appraisal relying on the use of "reference organisms". Concentration factors (CFs), dynamic models and, in cases where parameters are missing, allometry have been employed in the consideration of radionuclide transfer. Dose conversion coefficients (DCCs) have been derived for selected flora and fauna using, inter alia, dose attenuation and chord distribution functions. The calculated dose-rates can be contextualised through comparison with dose-rates arising from natural background and chronic dose-rates at which biological effects have been observed in selected "umbrella" endpoints.

Animals↗
PubMed2006

Patterns and inventories of radioactive contamination of island sites of the Yenisey River, Russia.

The distribution of radioactive contamination at three island sites downstream from the Krasnoyarsk Mining and Chemical Combine (KMCC) was studied with the objectives of mapping contamination levels, interpreting radionuclide distributions through consideration of alluvial processes and determining radionuclide inventories. Contamination was measured using in situ gamma spectrometry and landforms characterised using topographic surveying methods. Maximum (137)Cs contamination densities (700 kBq m(-2)) were found on low- and middle-level floodplains and low-lying interconnecting areas of Beriozovy Island (16 km from the KMCC). On Mikhin Island (180 km from the KMCC) maximum total (60)Co, (152)Eu and (154)Eu activity concentrations (30-40 kBq m(-2)) occur in low-lying areas inundated during flooding. Maximum (137)Cs and total (60)Co, (152)Eu and (154)Eu contamination densities on Cheriomukhov Island (250 km from the KMCC) were 390 and 50 kBq m(-2), respectively. Estimated (137)Cs inventories were 145, 148 and 16GBq for Beriozovy, Mikhin and Cheriomukhov Islands, respectively.

Cesium Radioisotopes↗
PubMed2005

Radioactive contamination of the Balchug (Upper Yenisey) floodplain, Russia in relation to sedimentation processes and geomorphology.

The radioactive contamination of a riverine floodplain, heavily influenced by discharges from Krasnoyarsk-26, has been studied with respect to sedimentation processes and the geomorphology of the Upper Yenisey floodplain. The study was effected by implementation of a regime of in situ observations and measurements, sampling, and the interpretation of satellite images. The results of the study indicate that on the Balchug Bypass Floodplain, radionuclide contamination is primarily influenced by the thickness of the deposited sediments, and the area can be considered as two depositional environments. The Balchug floodplain area was contaminated due to sedimentation of radionuclide-contaminated alluvium, whose depositional regime significantly changed after the construction of a hydroelectric power station in 1967. Contamination levels are lower on the upstream part of the floodplain where sediment depth is less than 0.2-0.3 m, and this contamination started to accumulate in 1967, while the downstream part of the floodplain, exhibiting deeper deposits, displays higher levels of radionuclide contamination because radionuclides began to deposit here in 1958 when the Krasnoyarsk-26 Mining and Chemical Combine (KMCC) commenced operation. Radionuclide contamination of the floodplain is also related to the elevation of the floodplain, higher regions of the floodplain typically having lower contamination than low-lying areas, which tend to be frequently inundated with sediments being deposited during such inundations. Local relief, its orientation, and vegetation cover have also combined to form sediment traps with significantly higher radionuclide contamination. Lithological analysis combined with radiometric assay indicates a total 137Cs floodplain inventory of 33.7 GBq.

Cesium Radioisotopes↗
PubMed2005

Modern management of salivary calculi.

BACKGROUND: The aim was to investigate the results of a minimally invasive approach to the management of salivary calculi. METHODS: Four hundred and fifty-five salivary calculi (323 submandibular and 132 parotid) were treated using extracorporeal shock-wave lithotripsy (ECSWL), fluoroscopically guided basket retrieval or intraoral stone removal under general anaesthesia. The techniques were used either alone or in combination. RESULTS: ECSWL achieved complete success (stone and symptom free) in 87 (39.4 percent) of 221 patients (84 of 218 primary and all of three secondary procedures; 43 of 131 submandibular, 44 of 90 parotid). Basket retrieval cured 124 (74.7 percent) of 166 patients (103 of 136 primary and 21 of 30 secondary procedures; 80 of 109 submandibular, 44 of 57 parotid). Intraoral surgical removal was successful in a further 137 (95.8 percent) of 143 patients with submandibular stones (99 of 101 primary, 36 of 38 secondary and two of four tertiary procedures). The overall success rate for the three techniques was 348 (76.5 percent) of 455. CONCLUSION: A minimally invasive approach to the management of salivary calculi is to be encouraged. All three techniques described have low morbidity and afford the possibility of retaining a functional gland.

Adolescent↗
PubMed2005

Production and validation of the use of gamma phage for identification of Bacillus anthracis.

Gamma phage specifically lyses vegetative cells of Bacillus anthracis and serves as part of the basis for identification of isolates from agar cultures. We report our study to standardize gamma phage production and preparation and to validate the assay for routine use. Unstable phage preparations were largely reduced through propagation of phage on blood agar cultures of the avirulent B. anthracis strain CDC684 and were adequately stable for extended storage beyond 1 to 2 years at 4 degrees C, provided that the preparation initially gave rise to clearly discernible plaques (macroplaques, 5 to 10 mm in diameter) on dilution at 1:8 or greater during potency testing with the Sterne strain or its equivalent. The primary intent of the assay was to test nonhemolytic, ground-glass-appearing bacterial B. anthracis-like colonies arising from culture of clinical or nonclinical samples on 5% sheep blood agar. Specifically, the assay was designed to show clear or primarily clear circular zones of lysis on bacterial lawns at the site of gamma phage inoculation after incubation at 35 degrees C +/- 2 degrees C for 20 h. When tested with 51 B. anthracis strains and 49 similar non-B. anthracis Bacillus species, the analytical specificity was >95%, a value that is intentionally low because our study design included two rare nonsusceptible B. anthracis strains as well as a rare susceptible non-B. anthracis strain, B. cereus ATCC 4342. Repeatability, day-to-day precision, and analyst-to-analyst precision were superior. The assay was rugged to variations among phage lots, phage concentration, amounts of bacterial inoculum, and incubation times as short as 6 to 8 h. System suitability evaluation showed improved robustness when bacterial lawns were tested with high- and low-density inoculum using the first and second quadrants of a serial four-quadrant streak on 5% sheep blood agar plates.

Animals↗
PubMed2004

Polysynaptic pathways from the vestibular nuclei to the lateral mammillary nucleus of the rat: substrates for vestibular input to head direction cells.

The activity of some neurons in the lateral mammillary nucleus (LMN) of the rat corresponds with the animal's current head direction (HD). HD cells have been studied extensively but the circuitry responsible for the generation and maintenance of the HD signal has not been established. The present study tested the hypothesis that a polysynaptic pathway connects the vestibular nuclei with the LMN via one or more relay nuclei. This circuitry could provide a substrate for the integration of sensory input necessary for HD cell activity. This hypothesis is based upon the prior demonstration that labyrinthectomy abolishes HD selectivity in thalamic neurons. Viral transneuronal tracing with pseudorabies virus (PRV) was used to test this hypothesis. We injected recombinants of PRV into the LMN and surrounding nuclei of adult male rats and defined the patterns of retrograde transneuronal infection at survival intervals of 60 and 72 h. Infected medial vestibular neurons (MVN) were only observed at the longest postinoculation interval in animals in which the injection site was localized largely to the LMN. Robust infection of the dorsal tegmental nucleus (DTN) and nucleus prepositus hypoglossi (PH) in these cases, but not in controls, at both survival intervals identified these nuclei as potential relays of vestibular input to the LMN. These data are consistent with the conclusion that vestibular information that contributes to the LMN HD cell activity is relayed to this caudal hypothalamic cell group via a polysynaptic brainstem circuit.

Animals↗
PubMed2004

Glandular function after intraoral removal of salivary calculi from the hilum of the submandibular gland.

We studied 43 patients (25 women and 18 men) who had salivary calculi removed from the hilum of the submandibular gland. Preoperatively they had clinical and radiographic examinations, and glandular function was measured scintigraphically in 38 patients. Postoperative follow-up was based on history, clinical examination, structured questionnaire, and scintigraphy. Stone(s) were removed successfully in 42 patients (97%). During the follow-up of a mean of 24 months (range 4-47), 37 patients were symptom-free and 2 patients had mild obstructive symptoms that did not require intervention. The other 4 patients had repeated infections that necessitated removal of the gland under general anaesthesia. Preoperative and postoperative scintigraphic assessments were made in 37 patients (88%). There was a significant increase in the functional fraction and the excretion rate in the gland after removal of the calculus. We conclude that glandular function improves to varying degrees in most patients after the removal of a salivary calculus.

Female↗
PubMed2004

Intra-oral removal of stones from the hilum of the submandibular gland: report of technique and morbidity.

There is increasing evidence to show that the submandibular gland regains function after stone removal and sialoadenectomy may not be the treatment of choice for proximal calculi. A technique of hilar stone removal is described with results and morbidity reported in a series of 55 patients. Stones were retrieved in 54 patients (98%) but four glands (8%) were subsequently removed due to recurrent obstruction. There were no complications related to the procedure (nerve injury, bleeding, infection or scarring) and the morbidity was less than reported for sialoadenectomy.

Adult↗
PubMed2004

Radiation doses to aquatic organisms from natural radionuclides.

A framework for protection of the environment is likely to require a methodology for assessing dose rates arising from naturally occurring radionuclides. This paper addresses this issue for European aquatic environments through a process of (a) data collation, mainly with respect to levels of radioactivity in water sediments and aquatic flora and fauna, (b) the use of suitable distribution coefficients, concentration factors and global data where data gaps are present and (c) the utilisation of a reference organism approach whereby a finite number of suitable geometries are selected to allow dose per unit concentration factors to be derived and subsequent absorbed dose calculations (weighted or unweighted) to be made. The majority of the calculated absorbed dose, for both marine and freshwater organisms, arises from internally incorporated alpha emitters, with 210Po and 226Ra being the major contributors. Calculated doses are somewhat higher for freshwater compared to marine organisms, and the range of doses is also much greater. This reflects both the much greater variability of radionuclide concentrations in freshwater as compared to seawater, and also variability or uncertainty in concentration factor values. This work has revealed a number of substantial gaps in published empirical data especially for European aquatic environments.

Animals↗
PubMed2003

Bone resorption predicts for skeletal complications in metastatic bone disease.

Relationships between the rate of bone resorption (measured by urinary N-telopeptide (Ntx) excretion) and a range of skeletal complications have been evaluated in patients with metastatic bone disease. A total of 121 patients had monthly measurements of Ntx during treatment with bisphosphonates. All skeletal-related events, plus hospital admissions for bone pain and death during the period of observation, were recorded. Data were available for 121 patients over the first 3-month period of monitoring (0-3 months) and 95 patients over the second 3-month period (4-6 months). N-telopeptide levels were correlated with the number of skeletal-related events and/or death (r=0.62, P<0.001 for 0-3 months and r=0.46, P<0.001 for 4-6 months, respectively). Patients with baseline Ntx values > or =100 nmol mmol(-1) creatinine (representing clearly accelerated bone resorption) were 19.48 times (95% CI 7.55, 50.22) more likely to experience a skeletal-related event/death during the first 3 months than those with Ntx <100 (P<0.001). In a multivariate logistic regression model, Ntx was highly predictive for events/death. This study is the first to indicate a strong correlation between the rate of bone resorption and the frequency of skeletal complications in metastatic bone disease. N-telopeptide appears useful in the prediction of patients most likely to experience skeletal complications and thus benefit from bisphosphonate treatment.

Aged↗
PubMed2003

Extracorporeal shockwave lithotripsy in the management of salivary calculi.

BACKGROUND: The aim was to investigate the results of extracorporeal shockwave lithotripsy in the management of salivary calculi using a dedicated sialolithotriptor. METHODS: Some 122 salivary calculi (84 submandibular and 38 parotid) were treated in an experimental study using a sialolithotriptor. RESULTS: Complete success was achieved in 40 procedures (33 per cent), 27 of 84 submandibular and 13 of 38 parotid calculi. A further 43 patients (35 per cent) were rendered asymptomatic although some stone debris remained in the duct (26 submandibular and 17 parotid). Failure (retention of stone debris and continued symptoms) occurred in 39 patients (32 per cent), 30 submandibular and eight parotid glands. The chance of failure increased with the size of the calculus and increasing duration of symptoms. CONCLUSION: Extracorporeal shockwave lithotripsy provides a useful option for the management of salivary calculi, particularly for stones less than 7 mm in diameter.

Adolescent↗
PubMed2002

A 'weighted' 137Cs inventory calculation of Reservoir 11, Mayak P.A., Russia with the novel use of remotely sensed information and sample data in a GIS.

The objective of this study was to make a robust 137Cs inventory calculation for Reservoir 11 in the Mayak Production Associations industrial cascade of reservoirs. High resolution satellite photographs provided information about the original Techa River and floodplain environment before, during and also after Reservoir 11 was constructed. The images provided important clues about the old Techa River system and also showed the extent of the contaminated area. Sediment cores were sampled along a transect in Reservoir 11, and perpendicular to the Techa River in 1996. 13Cs contamination densities were in the range 344-4030 kBq m(-2) and appear to exhibit a strong dependence on relative position along the transect, with more central positions exhibiting the highest actual levels. The contamination densities derived from the seven cores were combined with (published) data from four core samples collected in a 1994 field campaign. Sample data and images were integrated in a geographical information system (GIS). The GIS aided in the definition of distinctive floodplain classes, the so-called sediment 'facies', area calculations and in the positioning of 1994 and 1996 sample profiles in the reservoir. The resulting inventory estimate for Reservoir 11, is a factor 4-10 lower than earlier calculations. Analysis of the uncertainty in the calculations has been carried out and provides support for the integrity of the new method.

Cesium Radioisotopes↗
PubMed2002

Does the vestibular system contribute to head direction cell activity in the rat?

Head direction cells (HDC) located in several regions of the brain, including the anterior dorsal nucleus of the thalamus (ADN), postsubiculum (PoS), and lateral mammillary nuclei (LMN), provide the neural substrate for the determination of head direction. Although activity of HDC is influenced by various sensory signals and internally generated cues, lesion studies and some anatomical and physiological evidence suggest that vestibular inputs are critical for the maintenance of directional sensitivity of these cells. However, vestibular inputs must be transformed considerably in order to signal head direction, and the neuronal circuitry that accomplishes this signal processing has not been fully established. Furthermore, it is unclear why the removal of vestibular inputs abolishes the directional sensitivity of HDC, as visual and other sensory inputs and motor feedback signals strongly affect the firing of these neurons and would be expected to maintain their directional-related activity. Further physiological studies will be required to establish the role of vestibular system in producing HDC responses, and anatomical studies are needed to determine the neural circuitry that mediates vestibular influences on determination of head direction.

Animals↗
PubMed2002

Temporal trends for 99Tc in Norwegian coastal environments and spatial distribution in the Barents Sea.

The objective of this study was to reassess 99Tc transit times and transfer factors, from Sellafield to northern Norway, and to determine the extent of 99Tc migration to the Barents Sea. Filtered seawater samples were collected on a monthly basis from Hillesøy, northern Norway, and in February 1999 from the Barents Sea. Results showed an increase in levels of 99Tc at Hillesøy where activity concentrations have increased from a baseline of 0.2-0.4Bq m(-3) to a maximum of 1.6 Bq m(-3). A transit time of 42 months and a transfer factor of 6Bq m(-3) per PBq a(-1) have been derived, using cross-correlation analysis. The current study predicts that future levels are unlikely to increase dramatically over the levels observed in 1998. Levels of 99Tc in the Barents Sea ranged from 0.2 Bq m(-3) to 1.1 Bq m(-3) showing the influence of new 99Tc inputs by early 1999.

Environmental Pollutants↗