COMMITTED EFFECTIVE DOSE FROM NATURAL RADIONUCLIDES IN FARM-RAISED AND WILD CATFISH IN IBADAN, NIGERIA.

There is extensive contamination of the aquatic environment when rivers and streams flow through areas of high human activities such as industrial cities and major towns. These contaminations may include enhanced background levels of naturally occurring radioactive materials resulting from rapid urbanization and other human activities. The natural radionuclides (40K, 238U (226Ra) and 232Th (228Ra)) contents of farm-raised and wild catfish in five fish farms and three major rivers within Ibadan metropolis have been studied using gamma spectrometry. The results indicate that the average committed effective doses from the ingestion of the two sets of catfishes are 104 ± 37 and 104 ± 32 µSv/y for farm-raised and wild catfish, respectively. It can be concluded that the consumption of the catfishes poses no immediate radiological hazards to the population of the study area.

Acetylcholinesterase inhibitor from Anthocleista vogelii leaf extracts.

BACKGROUND: Anthocleista vogelii (Planch) is used in folk medicine in conditions related to inflammation and oxidative stress. This suggests that some of its constituents could possess ability to reduce oxidative damage to cells and ameliorate inflammatory conditions which are two prominent features in the brain of a person suffering from Alzheimer's disease. AIM OF STUDY: The leaf extracts were investigated for their bioactive constituents in our quest for novel compounds for the management of Alzheimer's disease. MATERIALS AND METHODS: Anthocleista vogelii crude leaf extract obtained from 80% methanol was successively partitioned with n-hexane, dichloromethane (DCM), ethyl acetate (EtOAc) and n-butanol. This gave four solvent fractions of the crude extract. These fractions and isolated compound were subjected to acetylcholinesterase (AChE) inhibitory activity test using the microplate assay method. The structure of the isolated compound was determined using spectroscopic methods (1D and 2D NMR, and MS). RESULTS: The results of the acetylcholinesterase inhibitory assay revealed that n-BuOH and ethyl acetate fractions had the best activity with IC50 of 564.58 and 727.63 µg/mL respectively. Activity directed fractionation of each of these fractions led to the isolation of the same compound identified as a C-glucosylflavone; isovitexin-7-O-methyl ether (swertisin). This rare C-glucosylflavone co-exist as two rotamers and exhibited duplication of NMR signals. It is reported from this plant for the first time. Swertisin displayed better acetylcholinesterase inhibitory activity with IC50 of 32.09 µg/mL than physostigmine (eserine) with IC50 of 56.09 µg/mL used as a standard. CONCLUSIONS: This study reports isolation and characterization of a rare C-glycosylflavone; isovitexin-7-O-methyl ether (swertisin). Isolated compound exhibited duplication of NMR signals and better acetylcholinesterase inhibitory activity than eserine used as a standard. The activity exhibited by this compound suggests that it could be useful in the management of Alzheimer's disease.

Intra- and inter-specific variation in alarm pheromone produced by Solenopsis fire ants.

Some fire ants of the genus Solenopsis have become invasive species in the southern United States displacing native species by competition. Although the displacement pattern seems clear, the mechanisms underlying competitive advantage remain unclear. The ability of ant workers to produce relatively larger amount of alarm pheromone may correspond to relative greater fitness among sympatric fire ant species. Here we report on quantitative intra-specific (i.e. inter-caste) and inter-specific differences of alarm pheromone component, 2-ethyl-3,6-dimethylpyrazine (2E36DMP), for several fire ant species. The alarm pheromone component was extracted by soaking ants in hexane for 48 h and subsequently quantified by gas chromatography-mass spectrometry at single ion monitoring mode. Solenopsis invicta workers had more 2E36DMP than male or female alates by relative weight; individual workers, however, contained significantly less pyrazine. We thus believe that alarm pheromones may serve additional roles in alates. Workers of Solenopsis richteri, S. invicta, and hybrid (S. richteri × S. invicta) had significantly more 2E36DMP than a native fire ant species, Solenopsis geminata. The hybrid fire ant had significantly less 2E36DMP than the two parent species, S. richteri and S. invicta. It seems likely that higher alarm pheromone content may have favored invasion success of exotic fire ants over native species. We discuss the potential role of inter-specific variation in pyrazine content for the relationship between the observed shifts in the spatial distributions of the three exotic fire ant species in southern United States and the displacement of native fire ant species.

Radioactivity in drilled and dug well drinking water of Ogun state Southwestern Nigeria and consequent dose estimates.

Activity concentrations of (40)K, (226)Ra, (228)Ac and (235)U were measured in 11 dug and 9 drilled well water samples from 3 large cities in Ogun state, Southwestern Nigeria, consumed by the population living in the cities. The measurement was done using co-axial type high-purity germanium (HPGe) detector (Canberra Industries Inc.). The measured activity concentrations in the water samples ranged from 1.74 +/- 1.83 to 4.69 +/- 0.17 Bq l(-1); 2.89 +/- 0.62 to 7.79 +/- 7.22 Bq l(-1); 0.35 +/- 0.07 to 1.17 +/- 0.40 Bq l(-1) and 0.18 +/- 0.05 to 4.77 +/- 0.34 Bq l(-1) for (40)K, (226)Ra, (228)Ac and (235)U, respectively. Total annual effective dose rates from the ingestion of these radionuclides in the untreated wells were estimated using measured activity concentrations in the radionuclides and their ingested dose conversion factors. Estimated annual effective dose rates ranged from 0.04 to 6.82; 0.01 to 1.36 and 0.01 to 1.49 mSv y(-1) for age groups <1, 2-7 and > or =17 y, respectively. Committed dose for age group > or =17 y ranged from 8.8 x 10(-4) to 8.9 x 10(-2) Sv. The calculated annual effective dose values due to the ingestion of (226)Ra in the Awujale, Ake, Saboab, Alagbon, Alapora and Totoro samples exceeded International Commission on Radiological Protection limit of 1.0 mSv y(-1) for individual public exposure. These wells are recommended for treatment that would remove radium from their waters.

An assessment of natural radioactivity of soils and its external radiological impact in southwestern Nigeria.

Soil samples collected from five states in the southwestern part of Nigeria have been analyzed for activity concentration of gamma-ray emitters. The States were Oyo, Lagos, Ondo, Ogun, and Osun. Activity concentration measurement was carried out using a co-axial type high purity germanium (HPGe) detector. Spectral analyses were performed using spectrometry software. The activity concentration measured ranged from 0.03 +/- 0.2 Bq kg(-1) for 137Cs to 1,358.6 +/- 28.5 Bq kg(-1) for (40)K. (40)K accounted for most of the activity. The calculated absorbed dose rates in air at 1.0 m above the ground ranged from 6 to 303 nGy h(-1) with a mean and standard deviation of 60.5 nGy h(-1) and 63.2 nGy h(-1), respectively. Estimated annual outdoor effective dose equivalent varied from 8 to 370 mSv y(-1). The calculated collective dose equivalent values for the five states ranged from 87,000 person-Sv to 600,000 person-Sv. The estimated annual outdoor effective values were considerably higher than the world soil average value of 70 microSv y(-1) reported by the International Commission on Radiological Protection.

Determination of natural radioactivity in drinking water in private dug wells in Akure, Southwestern Nigeria.

Gamma spectrometry of well water was done to measure the activity concentrations of gamma-emitters 226Ra and 228Ra from 238U and 232Th series, respectively, and 40K in their waters. Measurements were done using high-purity (HPGe) co-axial detectors (Canberra, GC 2018-7500 ) coupled to Canberra Multichannel Analyser system. Activity concentrations ranged from 0.57 to 26.86, 0.20 to 60.06 and 0.35 to 29.01 Bq l(-1) for 226Ra, 228Ra and 40K, respectively. Activity concentrations were compared with data from other parts of the world and used to estimate annual effective dose for three age groups. Total annual effective doses from the intake of these radionuclides in the waters ranged from 0.02 to 76.84, 0.02 to 38.80 and 0.05 to 481.60 mSv y(-1) for age group <1, 2-7 and > or =17 y, respectively. These values are considerably higher than both the World Health Organisation and the International Commission on Radiological Protection limits.

Evaluation of absorbed dose rate and annual effective dose equivalent due to terrestrial gamma radiation in rocks in a part of Southwestern Nigeria.

The average outdoor absorbed dose rate in air and the average annual effective dose equivalent due to terrestrial gamma radiation from 40K, 238U and 232Th in rocks in Ondo and Ekiti States, Southwestern Nigeria have been evaluated from measurements of the concentrations of these radionuclides in this environmental material. The concentration measurements were obtained using a very sensitive gamma spectroscopic system consisting of a 7.6 cm x 7.6 cm NaI(Tl) scintillation detector coupled to a computerised ACCUSPEC installation. The average absorbed dose rate and average annual effective dose equivalent was found to be 8.33 +/- 2.76 nGy x h(-1) and 8.7 +/- 2.9 microSv x y(-1) respectively.

Distribution of natural radioactivity in rocks from Ikogosi-Ekiti, Southwestern Nigeria and its radiological implications.

The natural radioactivity in some rock samples in Ikogosi-Ekiti, Southwestern Nigeria, has been measured using a very sensitive gamma spectroscopic system consisting of a 76 mm x 76 mm NaI(TI) scintillation detector system coupled to a versatile Canberra Series 10 plus multichannel analyzer. The average concentrations of natural radioisotopes 238U, 232Th, and 40K are 57.9 +/- 28.1 Bq kg-1, 81.6 +/- 23.8 Bq kg(-1) and 1203.1 +/- 687.2 Bq kg(-1), respectively. These average values give rise to a mean absorbed dose rate of 0.128 +/- 0.051, microGy h(-1) at a height of 1.0 m and an effective dose equivalent of 156.90 microSv (y-1). The results indicate no radiological anomaly. The data presented here will serve as a baseline survey for primordial radionuclide concentrations in rocks of the area.