Internal dose assessment of <Superscript>210</Superscript>Po using biokinetic modeling and urinary excretion measurement

The mysterious death of Mr. Alexander Litvinenko who was most possibly poisoned by Polonium-210 (²¹⁰Po) in November 2006 in London attracted the attention of the public to the kinetics, dosimetry and the risk of this high radiotoxic isotope in the human body. In the present paper, the urinary excretion of seven persons who were possibly exposed to traces of ²¹⁰Po was monitored. The values measured in the GSF Radioanalytical Laboratory are in the range of natural background concentration. To assess the effective dose received by those persons, the time-dependence of the organ equivalent dose and the effective dose after acute ingestion and inhalation of ²¹⁰Po were calculated using the biokinetic model for polonium (Po) recommended by the International Commission on Radiological Protection (ICRP) and the one recently published by Leggett and Eckerman (L&E). The daily urinary excretion to effective dose conversion factors for ingestion and inhalation were evaluated based on the ICRP and L&E models for members of the public. The ingestion (inhalation) effective dose per unit intake integrated over one day is 1.7 × 10⁻⁸ (1.4 × 10⁻⁷) Sv Bq⁻¹, 2.0 × 10⁻⁷ (9.6 × 10⁻⁷) Sv Bq⁻¹ over 10 days, 5.2 × 10⁻⁷ (2.0 × 10⁻⁶) Sv Bq⁻¹ over 30 days and 1.0 × 10⁻⁶ (3.0 × 10⁻⁶) Sv Bq⁻¹ over 100 days. The daily urinary excretions after acute ingestion (inhalation) of 1 Bq of ²¹⁰Po are 1.1 × 10⁻³ (1.0 × 10⁻⁴) on day 1, 2.0 × 10⁻³ (1.9 × 10⁻⁴) on day 10, 1.3 × 10⁻³ (1.7 × 10⁻⁴) on day 30 and 3.6 × 10⁻⁴ (8.3 × 10⁻⁵) Bq d⁻¹ on day 100, respectively. The resulting committed effective doses range from 2.1 × 10⁻³ to 1.7 × 10⁻² mSv by an assumption of ingestion and from 5.5 × 10⁻² to 4.5 × 10⁻¹ mSv by inhalation. For the case of Mr. Litvinenko, the mean organ absorbed dose as a function of time was calculated using both the above stated models. The red bone marrow, the kidneys and the liver were considered as the critical organs. Assuming a value of lethal absorbed dose of 5 Gy to the bone marrow, 6 Gy to the kidneys and 8 Gy to the liver, the amount of ²¹⁰Po which Mr. Litvinenko might have ingested is therefore estimated to range from 27 to 1,408 MBq, i.e 0.2–8.5 μg, depending on the modality of intake and on different assumptions about blood absorption.     

Radioactive aerosols released from the Chernobyl Shelter into the immediate environment

The release of radioactive particles through large gaps in the containment of the destroyed Chernobyl reactor was assessed during two measurement periods. In 1996–1999, a total radionuclide flow rate of 274 Bq s⁻¹ or 8.64 × 10⁹ Bq year⁻¹ was determined. These releases were predominantly due to ¹³⁷Cs (78.5%), ⁹⁰Sr (21.1%), and ^239+240Pu (0.4%). The mean activity concentration in the aerosol measured directly at the gaps was about 240 mBq m⁻³ with an activity median aerodynamic diameter (AMAD) of 2.4 μm for ¹³⁷Cs, 120 mBq m⁻³ with an AMAD in the range 3.1–13 μm for ⁹⁰Sr, 1.8 mBq m⁻³ with an AMAD in the range 3.5–11 μm for ^239+240Pu, and 2.0 mBq m⁻³ with an AMAD of 1.5 μm for ²⁴¹Am. The resulting total inhalation dose rate calculated close to the gaps was about 100 nSv h⁻¹. In the near environment, the mean ¹³⁷Cs activity in the aerosol was 2.2 mBq m⁻³ with an AMAD of 2.2 μm, which gave rise to an inhalation dose rate of about two orders of magnitude lower than the corresponding dose rate at the gaps. Occasionally, however, dose levels were measured in the near environment that were similar to those at the gaps. In 2000–2003, lower activity concentrations were observed. The decrease was more pronounced at the gaps than in the near environment. The results indicate that effective dose due to inhalation must be considered for the dose assessment of construction workers who will be deployed at the Chernobyl site to reconstruct the old or to build the new Shelter, in the future.     

Leaching of depleted uranium in soil as determined by column experiments

The basic features of the leachability of depleted uranium (DU) projectiles in soil was investigated by using 12 projectiles (145–294 g DU) and 16 columns installed in an air-conditioned laboratory. Two soils widely distributed in Europe, a sandy-loamy cambisol and a silty-loamy luvisol, were filled into the columns (3.3 kg dry soil each). The effluents of all columns were collected weekly during the observation period of 1 year. In 648 samples, ²³⁵U and ²³⁸U were determined by inductively coupled plasma mass spectrometry. The leaching rates of ²³⁸U from natural uranium were in general about 0.01 μg week^-1 or smaller, while those of ²³⁸U from the DU munitions varied considerably and reached values of up to 100 μg week^-1, for the different columns. In total, about 0.3 μg natural uranium corresponding to 20 ppm of its inventory in the soil was leached during the observation period. From the projectiles, an average of about 50 μg DU were leached corresponding to 18 ppm of the corroded DU mass (about 1.6% of the mean initial DU mass of the projectiles). Assuming that corrosion and leaching continue as observed, the mobilisation of ²³⁸U from DU munitions will last, on an average, for thousands of years in the soils investigated, while the munitions themselves will have been corroded after a much shorter time. It is proposed to use, for the investigated soil types, the mean leaching rates of the six columns with projectiles for transport calculations of ²³⁸U to the groundwater and, thus, for a better risk assessment of the water-dependent uptake pathways of DU.     

In vitro production of metabolism-enhancing phytoecdysteroids from <Emphasis Type="Italic">Ajuga turkestanica</Emphasis>

In order to develop a sustainable source of metabolism-enhancing phytoecdysteroids, cell suspension and hairy root cultures were established from shoot cultures of wild-harvested Ajuga turkestanica, a medicinal plant indigenous to Uzbekistan. Precursors of phytoecdysteroids (acetate, mevalonic acid cholesterol) or methyl jasmonate (an elicitor) were added to subculture media to increase phytoecdysteroid accumulation. In cell suspension cultures, 20-hydroxyecdysone (20E) content increased 3- or 2-fold with the addition of 125 or 250 μM methyl jasmonate, respectively, compared to unelicited cultures. Precursor addition, however, did not provoke phytoecdysteroid accumulation. In hairy root cultures, addition of sodium acetate, mevalonic acid, and methyl jasmonate, but not cholesterol, increased phytoecdysteroid content compared to unelicited cultures. Hairy root cultures treated with 150 mg l⁻¹ sodium acetate, or 15 or 150 mg l⁻¹ mevalonic acid, increased 20E content approximately 2-fold to 19.9, 20.4 or 21.7 μg mg⁻¹, respectively, compared to control (10.5 μg mg⁻¹). Older hairy root cultures, extracted after the seventh subculture cycle, also showed increases in 20E content (24.8 μg mg⁻¹), turkesterone (0.9 μg mg⁻¹) and cyasterone (8.1 μg mg⁻¹) compared to control cultures maintained for a shorter duration of four subculture cycles. Doses of 10 or 20 μg ml⁻¹ hairy root extract increased protein synthesis by 25.7% or 31.1%, respectively, in a C2C12 mouse skeletal cell line. These results suggest that sustainable production of metabolically active phytoecdysteroid can be achieved through hairy root culture systems. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Biochemical properties of lipoxygenase from opium poppy chloroplasts

Lipoxygenase (LOX) from opium poppy (Papaver somniferum L.) chloroplasts was isolated and 126.1-fold purified to electrophoretic homogeneity by combination of ion-exchange chromatography on HA-Ultragel column and affinity chromatography on a linoleyl-aminopropyl agarose column. The relative molecular mass of the LOX determined by SDS-PAGE was 92 kDa. Kinetic properties of purified LOX were determined in spectrophotometric assay by using of linoleic acid (K_M = 1.78 mM and V_max = 11.4 μmol mg⁻¹ min⁻¹) and linolenic acid (K_M = 1.27 mM and V_max = 10.2 μmol mg⁻¹ min⁻¹). The optimum pH was 6.0 for both linoleic and linolenic acid dioxygenation catalyzed by LOX. HPLC analysis of the products revealed a dual positional specificity of linoleic acid dioxygenation at pH 6.0 with ratio of 9- and 13-hydroperoxide products being about 1:1. The activity of purified LOX was stimulated by Mg²⁺ and Ca²⁺.     

Improvement of artemisinin production by chitosan in hairy root cultures of <Emphasis Type="Italic">Artemisia annua</Emphasis> L.

Artemisinin production by hairy roots of Artemisia annua L. was increased 6-fold to 1.8 μg mg⁻¹ dry wt over 6 days by adding 150 mg chitosan l⁻¹. The increase was dose-dependent. Similar treatment of hairy roots with methyl jasmonate (0.2 mM) or yeast extract (2 mg ml⁻¹) increased artemisinin production to 1.5 and 0.9 μg mg⁻¹ dry wt, respectively.     

Metabolic rate of Arctic charr eggs depends on their parentage

The metabolic rate (specific heat output) of individual eyed-stage eggs of Arctic charr Salvelinus alpinus (Linnaeus, 1758) originating from different families was measured with direct microcalorimetry. Metabolic rates varied between 2.3–7.9 μW ind⁻¹ and 0.06–0.22 μW mg⁻¹. Absolute heat output was unrelated to egg size, but size-scaled or specific heat output was negatively correlated with egg size, measured as diameter, dry mass or fresh mass. Metabolic rates varied significantly between families, suggesting that genetic and/or maternal effects affect embryonic metabolism in Arctic charr. Heat output increased almost linearly from 3.4 to 16.7 μW ind⁻¹ (0.09–0.67 μW mg⁻¹) during the embryonic development. Although the metabolic rate varied between the families and egg metabolic rate increased during development, there was an unexpected disconnect between metabolic rate and hatching time.     

Reconstruction and forecast of doses due to ingestion of <Superscript>137</Superscript>Cs and <Superscript>90</Superscript>Sr after the Chernobyl accident

The assessment doses due to ingestion of ¹³⁷Cs and ⁹⁰Sr for the population suffering from the Chernobyl accident was performed on the basis of the new mechanistic ecological model for assessment of radiological consequences of agricultural lands contamination (EMARC). The EMARC model allows estimation of internal doses based on ecological factors influencing the contamination of foodstuff, for the post-accidental years in the countries of the former Soviet Union. The EMARC model allows estimation of all quantities required in radiation hygiene practice. For example, the proposed analytical method may be used for both retrospective dose reconstruction and prospective estimates of annual dose and integrated “life-time” dose, for different age intervals. According to the EMARC model, estimated reference “life-time” doses for adults are between 7 and 269 μSv kBq⁻¹ m² for ¹³⁷Cs, and between 25 and 235 μSv kBq⁻¹ m² for ⁹⁰Sr. Maximal doses were estimated for persons who were 3, 9 and 11 years old, at the time of the accident and these doses exceed those for adults by a factors of 1, 5 for ⁹⁰Sr, and 1.4 for ¹³⁷Cs.     

Changes in protein pattern during different developmental stages of somatic embryos in chickpea

Mature embryonic axes were used for chickpea (Cicer arietinum L.) regeneration via somatic embryogenesis. Qualitative and quantitative estimation of protein profile during somatic embryogenesis by SDS-PAGE and densitometric analysis showed differential expression of various storage proteins at different stages of somatic embryo development, which was compared with the profile of developing seeds. Total protein content in somatic embryos of chickpea increased from globular stage [2.9 μg mg⁻¹(f.m.)] to cotyledonary stage [4.8 μg mg⁻¹(f.m.)] and then started decreasing during onset of maturation and germination [up to 1.5 μg mg⁻¹(f.m.)]. Differential expression of seed storage proteins, late embryogenesis abundant (LEA) proteins and proteins related with stress response were documented at different stages of somatic embryogenesis. Germinating somatic embryos showed degradation products of several seed storage proteins and the appearance of new polypeptides (76.8, 67.6, 49.9 and 34.2 kDa), which were absent during differentiation of somatic embryos. A low molecular mass (17.7 kDa) polypeptide was uniformly present during all stages of somatic embryogenesis and it may belong to a group of stress-related proteins. This study describes the expression of true seed storage proteins like legumin, vicilin, convicilin and their subunits at different stages of somatic embryogenesis, which may serve as excellent markers for embryogenic pathway of regeneration in chickpea.     

Carbon metabolism in in vitro cultures of date palm: the role of carboxylases (PEPC and RubisCO)

While describing major trends of carbon metabolism during the initiation and expression of somatic embryogenesis in date palm (Phoenix dactylifera L., cv. Deglet Nour), we have investigated the role of two carboxylases, namely PEPC (Phosphoenolpyruvate carboxylase, EC 4.1.1.31) and RubisCO (Ribulose 1,5-bisphosphate carboxylase/oxygenase, EC 4.1.1.39), in embryogenic and non-embryogenic cultures. The detection of PEPC activity on polyacrylamide native gels after electrophoresis revealed the presence of 3 active isoforms in crude extracts from the embryogenic (E) callus strain, whereas only a single band was present in the non-embryogenic (NE) one. The level of PEPC specific capacity was of the same order (3.9 ± 1.2 μmol CO₂ h⁻¹ mg⁻¹ TSP) in both types of cultures. Further changes in carboxylase (PEPC and RubisCO) activities during the growth and development of somatic embryo–derived plantlets were also analysed. The PEPC/RubisCO ratio was found to progressively decrease (from 17.7 to 0.2) throughout the in vitro development of plantlets, due to a substantial depletion of PEPC activity, which decreased from 5.3 to 1.2 μmol CO₂ h⁻¹ mg⁻¹ TSP. Concomitantly, RubisCO assumed greater importance (from 0.3 to 5.3 μmol CO₂ h⁻¹ mg⁻¹ _TSP ) and became the main route for inorganic carbon fixation. Western blot analysis using polyclonal antibodies raised against PEPC and RubisCO purified from tobacco leaves confirmed this trend in terms of relative enzyme abundance. This revised version was published online in June 2006 with corrections to the Cover Date.     

Estimation of fungal biomass in the decaying cones ofPinus densiflora

Fungal biomass in the decaying cones ofPinus densiflora was investigated. Leaching, immobilization and mobilization phases were recognized in the decomposition process of cones. Fungal biomass was estimated by the agar-film technique, using a conversion factor of 0.62 mg dry wt. mm⁻³ of hyphal volume to biomass and a factor of 2.5 for in-efficiencency of homogenization. The fungal biomass was 4.9±2.1 (mean±S.D.) mg dry wt. g⁻¹ dry matter in the cones on the tree, 11±6 mg g⁻¹ in the leaching phase, 19±7 mg g⁻¹ in the immobilization phase and 30±15 mg g⁻¹ in the mobilization phase. It significantly increased after cones had lain on the forest floor, and also in the immobilization phase. The latter result suggests that the fungal biomass contributed to the immobilization of nitrogen in the decomposition process. The ratio of ergosterol content to fungal biomass in the cones was 2.9–8.8 μg mg⁻¹ dry wt., lying in the range of 2–16 μg mg⁻¹ reported for mycelia. This suggested that the estimate of fungal biomass was reasonable. Reduction in this ratio with the dry weight loss in the cones suggested that the proportion of relatively active fungal biomass decreased with the progress of decomposition.     

Effect of Mg2+ on the Structure and Function of Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase

Mg²⁺ in various concentrations was added to purified Rubisco in vitro to gain insight into the mechanism of molecular interactions between Mg²⁺ and Rubisco. The enzyme activity assays showed that the reaction between Rubisco and Mg²⁺ was two order, which means that the enhancement of Rubisco activity was accelerated by low concentration of Mg²⁺ and slowed by high concentration of Mg²⁺. The kinetics constant (K _m) and V _max was 1.91 μM and 1.13 μmol CO₂ mg⁻¹ protein∙min⁻¹, respectively, at a low concentration of Mg²⁺, and 3.45 μM and 0.32 μmol CO₂∙mg⁻¹ protein∙min⁻¹, respectively, at a high concentration of Mg²⁺. By UV absorption and fluorescence spectroscopy assays, the Mg²⁺ was determined to be directly bound to Rubisco; the binding site of Mg²⁺ to Rubisco was 0.275, the binding constants (K _A) of the binding site were 6.33 × 10⁴ and 5.5 × 10⁴ l·mol⁻¹. Based on the analysis of the circular dichroism (CD) spectra, it was concluded that the binding of Mg²⁺ did not alter the secondary structure of Rubisco, suggesting that the observed enhancement of Rubisco carboxylase activity was caused by a subtle structural change in the active site through the formation of the complex with Mg²⁺.     

Production of β-galactosidase from thermophilic fungus Rhizomucor sp

A thermostable β-galactosidase was produced extracellularly by a thermophilic Rhizomucor sp, with maximum enzyme activity (0.21 U mg⁻¹) after 4 days under submerged fermentation condition (SmF). Solid state fermentation (SSF) resulted in a nine-fold increase in enzyme activity (2.04 U mg⁻¹). The temperature range for production of the enzyme was 38–55°C with maximum activity at 45°C. The optimum pH and temperature for the partially purified enzyme was 4.5 and 60°C, respectively. The enzyme retained its original activity on incubation at 60°C up to 1 h. Divalent cations like Co²⁺, Mn²⁺, Fe²⁺ and Zn²⁺ had strong inhibitory effects on the enzyme activity. The K _m and V _max for p-nitrophenyl-β- _D-galactopyranoside and o-nitrophenyl-β - _D-galactopyranoside were 0.39 mM, 0.785 mM and 232.1 mmol min⁻¹ mg⁻¹ respectively. The K _m and V _max for the natural substrate lactose were 66.66 μM and 0.20 μ mol min⁻¹ mg⁻¹. Received 10 March 1997/ Accepted in revised form 17 July 1997     

Properties of two endoglucanases from a mutant strain <Emphasis Type="Italic">Trichoderma</Emphasis> sp. M<Subscript>7</Subscript> with potential application in the paper industry

Two endoglucanases were purified to electrophoretic homogeneity from the culture filtrate of a mutant strain Trichoderma sp. M₇. EG-III and EG-IV had Mr of 49.7 and 47.5 kDa, and estimated pi values of 3.7 and 6.35, respectively. The optimal pH and temperature values were determined to be pH 5.0 and 60°C for the first cellulase, whereas pH 5.2 and 50 °C were optimal for the other. Endoglucanases exhibited typical Michaelis-Menten kinetics with K _m and V values of 2.9 mg ml⁻¹ and 60498.5 μmol min⁻¹ mg⁻¹ for EG-III and 3.8 mg ml⁻¹ and 22650.9 μmol min⁻¹ mg⁻¹ for EG-IV, respectively. Mn²⁺, Cu²⁺ and Pd²⁺ strongly inhibited the enzymes. EC-IV catalyzed the hydrolysis of Na-CMC and hydroxyethyl cellulose (HEC) only, whereas EG-III displayed high activity towards xylans, also. Different preferences towards cellulosic substrates and their regions define a different role of the investigated enzymes in the degradation of plant biomass. Published in Russian in Prikladnaya Biokhimiya i Mikrobiologiya, 2009, Vol. 45, No. 2, pp. 171–175. The article is published in the original.     

Purification and Characterization of the Glutathione-S-transferases from the Northern Quahog Mercinaria mercinaria

Glutathione-S-transferase (GST) was isolated from the northern hardshell clam Mercinaria mercinaria (quahog) using a two-step procedure involving ammonium sulfate precipitation and affinity chromatography. Kinetic analysis of the purified enzyme using 1-chloro-2,4-dinitrobenzene as substrate revealed a specific activity of 38.0 μmol min⁻¹ mg⁻¹, while V _max and K _m values were estimated as 48.0 μmol min⁻¹ mg⁻¹ and 0.24 mM, respectively. Electrophoretic analysis of GST indicated multiple forms of the dimeric enzyme in quahogs with subunit molecular masses of 22, 24, 25, and 27 kDa. Isoelectric focusing analysis resulted in pI values for three isoenzymes of 5.1, 4.9, and 4.6. The acidic pI values obtained indicated that quahog GST belongs to the π class. Inhibition of quahog GST by tetrapyrroles was similar to that of GST from oyster and rat liver. Quantitative comparison of tetrapyrrole inhibition patterns of quahog GST with those of oyster and rat liver GST indicated lower inhibition rates by three of the four tetrapyrroles tested (bilirubin, biliverdin, and chlorophillyin), suggesting that quahog GST could differ structurally or functionally from oyster and rat liver GSTs. Received March 17, 1998; accepted August 18, 1998.     

Comparison of relative rates of BTEX biodegradation using respirometry

Biodegradation of BTEX by a microbial consortium isolated from a closed municipal landfill was studied using respirometric techniques. The kinetics of biodegradation were estimated from experimental oxygen uptake data using a nonlinear parameter estimation technique. All of the six compounds were rapidly degraded by the microbial culture and no substrate inhibition was observed at the concentration levels examined (200 mg L⁻¹ as COD). Microbial growth and contaminant degradation were adequately described by the Monod equation. Considerable differences were observed in the rates of BTEX biodegradation as seen from the estimates of the kinetic parameters. A three-fold variation was seen in the values of the maximum specific growth rate, μ_max. The highest value of μ_max was 0.389 h⁻¹ for p-xylene while o-xylene was characterized by a μ_max value of 0.14 h⁻¹, the lowest observed in this study. The half saturation coefficient, K _s, and the yield coefficient, Y, varied between 1.288–4.681 mg L⁻¹ and 0.272–0.645 mg mg⁻¹, respectively. Benzene and o-xylene exhibited higher resistance to biodegradation while toluene and p-xylene were rapidly degraded. Ethylbenzene and m-xylene were degraded at intermediate rates. In biodegradation experiments with a multiple substrate matrix, substrate depletion was slower than in single substrate experiments, suggesting an inhibitory nature of substrate interaction. Received 15 February 1998/ Accepted in revised form 5 July 1998     

Influence of human biokinetics of strontium on internal ingestion dose of <Superscript>90</Superscript>Sr and absorbed dose of <Superscript>89</Superscript>Sr to organs and metastases

The objective of the present work is to apply the plasma clearance parameters to strontium, previously determined in our laboratory, to improve the biokinetic and dosimetric models of strontium-90 (⁹⁰Sr) used in radiological protection; and also to apply this data for the estimation of the radiation doses from strontium-89 (⁸⁹Sr) after administration to patients for the treatment of the painful bone metastases. Plasma clearance and urinary excretion of stable strontium tracers of strontium-84 (⁸⁴Sr) and strontium-86 (⁸⁶Sr) were measured in GSF-National Research Center for Environment and Health (GSF) in 13 healthy German adult subjects after intravenous injection and oral administration. The biological half-life of strontium in plasma was evaluated from 49 plasma concentration data sets following intravenous injections. This value was used to determine the transfer rates from plasma to other organs and tissues. At the same time, the long-term retention of strontium in soft tissue and whole body was constrained to be consistent with measured values available. A physiological urinary path was integrated into the biokinetic model of strontium. Parameters were estimated using our own measured urinary excretion values. Retention and excretion of strontium were modeled using compartmental transfer rates published by the International Commission on Radiological Protection (ICRP), the SENES Oak Ridge Inc. (SENES), and the Urals Research Center for Radiation Medicine (TBM). The results were compared with values calculated by applying our GSF parameters (GSF). For the dose estimation of ⁸⁹Sr, a bone metastases model (GSF-M) was developed by adding a compartment, representing the metastases, into the strontium biokinetic model. The related parameters were evaluated based on measured data available in the literature. A set of biokinetic parameters was optimized to represent not only the early plasma kinetics of strontium but also the long-term retention measured in soft tissue and whole body. The ingestion dose coefficients of ⁹⁰Sr were computed and compared with different biokinetic model parameters. The ingestion dose coefficients were calculated as 2.8 × 10⁻⁸, 2.1 × 10⁻⁸, 2.5 × 10⁻⁸ and 3.8 × 10⁻⁸ Sv Bq⁻¹ for ICRP, SENES, TBM and GSF model parameters, respectively. Moreover, organ absorbed dose for the radiopharmaceutical of ⁸⁹Sr in bone metastases therapy was estimated based on the GSF and ICRP biokinetic model parameters. The effective doses were 3.3, 1.8 and 1.2 mSv MBq⁻¹ by GSF, GSF-M, and ICRP Publication 67 model parameters, respectively, compared to the value of 3.1 mSv MBq⁻¹ reported by ICRP Publication 80. The absorbed doses of red bone marrow and bone surface, 17 and 21 mGy MBq⁻¹ calculated by GSF parameters, and 7.1 and 8.8 mGy MBq⁻¹ by GSF-M parameters, are comparable to the clinical results of 3–19 mGy MBq⁻¹ for bone marrow and 16 mGy MBq⁻¹ for bone surface. Based on the GSF-M model, the absorbed dose of ⁸⁹Sr to metastases was estimated to be 434 mGy MBq⁻¹. The strontium clearance half-life of 0.25 h from the plasma obtained in the present study is obviously faster than the value of 1.1 h recommended by ICRP. There are no significant changes for ingestion dose coefficients of ⁹⁰Sr using different model parameters. A model including the metastases was particularly developed for dose estimation of ⁸⁹Sr treatment for the pain of bone metastases.     

Production of plants resistant to <Emphasis Type="Italic">Alternaria carthami</Emphasis> via organogenesis and somatic embryogenesis of safflower cv. NARI-6 treated with fungal culture filtrates

The present study describes a system for efficient plant regeneration via organogenesis and somatic embryogenesis of safflower (Carthamus tinctorius L.) cv. NARI-6 in fungal culture filtrates (FCF)-treated cultures. FCF was prepared by culturing Alternaria carthami fungal mycelia in selection medium for host-specific toxin production. Cotyledon explants cultured on callus induction medium with different levels of FCF (10–50%) produced embryogenic callus. In organogenesis, 42.2% microshoots formed directly from embryogenic callus tissues in plant regeneration medium with 40% FCF. Isolated embryogenic callus cultured on embryo induction medium containing 40% FCF induced 50.2% somatic embryogenesis. Embryo germination percentage was decreased from 64.5 to 28 in embryo maturation medium containing 40% FCF. However, nine plantlets from organogenesis and 24 plantlets from somatic embryogenesis were selected as FCF-tolerant. Alternaria carthami fungal spores (5 × 10⁵ spores/ml) sprayed on the leaves of FCF-tolerant plants showed enhanced survival rate over control plants, which plants were more susceptible to fungal attack. The number of leaf spot lesions per leaf was decreased from 3.4 to 0.9 and their lesion length was also reduced from 2.9 to 0.7 mm in organogenic derived FCF-tolerant plants over control. In somatic embryo derived FCF-tolerant plants, the number of lesions was decreased from 3.1 to 0.4 and the lesion size was also reduced to 2.7–0.5 mm when compared to the control. This study also examined antioxidant enzyme activity in FCF-tolerant plants. Catalase (CAT) activity was slightly decreased whereas peroxidase (POD) activity was increased to a maximum of 42% (0.19 μmol min⁻¹ mg⁻¹ protein) from organogenesis and 47% (0.23 μmol min⁻¹ mg⁻¹ protein) from embryogenesis in FCF-tolerant plants. Superoxide dismutase (SOD) activity was also increased to 17% (149 U mg⁻¹ protein) and 19.5% (145 U mg⁻¹ protein) in FCF-tolerant plants derived from organogenesis and somatic embryogenesis when compared with control plants.     

Biochemical characterization of the carotenoid 1,2-hydratases (CrtC) from <Emphasis Type="Italic">Rubrivivax gelatinosus</Emphasis> and <Emphasis Type="Italic">Thiocapsa roseopersicina</Emphasis>

Two carotenoid 1,2-hydratase (CrtC) genes from the photosynthetic bacteria Rubrivivax gelatinosus and Thiocapsa roseopersicina were cloned and expressed in Escherichia coli in an active form and purified by affinity chromatography. The biochemical properties of the recombinant enzymes and their substrate specificities were studied. The purified CrtCs catalyze cofactor independently the conversion of lycopene to 1-HO- and 1,1′-(HO)₂-lycopene. The optimal pH and temperature for hydratase activity was 8.0 and 30°C, respectively. The apparent K _m and V _max values obtained for the hydration of lycopene were 24 μM and 0.31 nmol h⁻¹ mg⁻¹ for RgCrtC and 9.5 μM and 0.15 nmol h⁻¹ mg⁻¹ for TrCrtC, respectively. Sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis revealed two protein bands of 44 and 38 kDa for TrCrtC, which indicate protein processing. Both hydratases are also able to convert the unnatural substrate geranylgeraniol (C20 substrate), which functionally resembles the natural substrate lycopene.