Genotoxic effect of ozone in human peripheral blood leukocytes

The genotoxic effect of ozone was studied in human leukocytes in vitro, using the single cell gel electrophoresis (SCGE) assay. Cell treatment for 1 h at 37 degrees C with 0.9-5.3 mM O(3) resulted in a dose-dependent increase of DNA damage, comparable to that induced by 4-40 mM of H(2)O(2), used as a positive control. This effect of ozone was reversed by post-treatment incubation of the cells for 45-90 min at 37 degrees C, and prevented by pre-incubation of the cells with catalase (20 microg/ml). These results demonstrate that O(3) induces DNA-damage in primary human leukocytes. The damage is rapidly repaired, and probably mediated by the formation of H(2)O(2).     

Anaerobic incubation enhances the colony formation of a polA recB strain of Escherichia coli K-12.

Escherichia coli strain E247 (polA1 recB21) has reduced colony formation (even at the permissive temperature of 30 degrees C) because of a poor suppressor mutation (sup-126). The colony formation was enhanced in the absence of oxygen about 3-fold at 30 degrees C and 10(6)-fold at 43 degrees C, suggesting that a polA recB strain was inviable due to oxygen toxicity. Colony formation was also increased by incubation in an agar medium containing the reducing agent thioglycolate and incubation in the presence of chloroform-killed Saccharomyces cerevisiae pet+ cells, but not pet cells. Since the E247 strain viability was inversely dependent on the oxygen pressure and since the strain was more sensitive to superoxide radical than either the polA or the recB mutant, it seems likely that the polA and recB genes play a role in repairing DNA damage during respiration.     

Oxygen enhances phosphine toxicity for postharvest pest control

Phosphine fumigations under superatmospheric oxygen levels (oxygenated phosphine fumigations) were significantly more effective than the fumigations under the normal 20.9% atmospheric oxygen level against western flower thrips [Frankliniella occidentalis (Pergande)] adults and larvae, leafminer Liriomyza langei Frick pupae, grape mealybug [Pseudococcus maritimus (Ehrhorn)] eggs, and Indianmeal moth [Plodia interpunctella (Hübner)] eggs and pupae. In 5-h fumigations with 1,000 ppm phosphine at 5 degrees C, mortalities of western flower thrips increased significantly from 79.5 to 97.7% when oxygen was increased from 20.9 to 40% and reached 99.3% under 80% O2. Survivorships of leafminer pupae decreased significantly from 71.2% under 20.9% O2 to 16.2% under 40% O2 and reached 1.1% under 80% O2 in 24-h fumigations with 500 ppm phosphine at 5 degrees C. Complete control of leafminer pupae was achieved in 24-h fumigations with 1,000 ppm phosphine at 5 degrees C under 60% O2 or higher. Survivorships of grape mealybug eggs also decreased significantly in 48-h fumigations with 1,000 ppm phosphine at 2 degrees C under 60% O2 compared with the fumigations under 20.9% O2. Indian meal moth egg survivorships decreased significantly from 17.4 to 0.5% in responses to an oxygen level increase from 20.9 to 40% in 48-h fumigations with 1,000 ppm phosphine at 10 degrees C and reached 0.2% in fumigations under 80% O2. When the oxygen level was reduced from 20.9 to 15 and 10% in fumigations, survivorships of Indianmeal moth eggs increased significantly from 17.4 to 32.9 and 39.9%, respectively. Increased O2 levels also resulted in significantly lower survival rates of Indianmeal moth pupae in response to 24-h fumigations with 500 and 1,000 ppm phosphine at 10 degrees C and a complete control was achieved in the 1,000 ppm phosphine fumigations under 60% O2. Oxygenated phosphine fumigations have marked potential to improve insecticidal efficacy. Advantages and limitations of oxygenated phosphine fumigation are discussed.     

Effect of incubation atmosphere and temperature on isolation of Campylobacter jejuni from human stools

To determine the optimal conditions for isolation of Campylobacter jejuni from human fecal specimens, we compared incubation atmospheres that contained about 5, 10, and 15% oxygen with the 17% oxygen produced in candle jars and also compared incubation temperatures of 37 and 42 degrees C. At 42 degrees C, C. jejuni was isolated from all 16 specimens; however, colony sizes were larger when plates were incubated in 5 and 10% oxygen than in the other two atmospheres. At 37 degrees C some positive cultures were missed in 15% oxygen and in the candle jar. The largest colony sizes were obtained in 5% oxygen. For each atmospheric condition tested, the colonies were larger at 42 than at 37 degrees C. When incubation is done at 42 degrees C, use of a candle jar is adequate; however, at 37 degrees C candle jars should not be used for isolation of C. jejuni from human feces.     

Hydrogen peroxide metabolism in alveolar macrophages after exposure to hypoxia and heat

High temperature can change the effects of intra- and intercellular regulators and therefore modify the cellular response to hypoxia. We investigated H(2)O(2) production by alveolar macrophages, isolated from adult male rats, which were incubated under conditions of oxygen deficiency and high temperature (experiment in vitro). The incubation of these cells for 2 hours at 10 % or 5 % oxygen led only to slight fluctuations in the H(2)O(2) level, while the rise of temperature from 37 degrees C up to 42 degrees C significantly increased its generation. Level of thiobarbituric acid-reactive substances (TBARS) underwent similar changes. Under these conditions the accumulation of H(2)O(2) was found to be caused mainly by its decreased cleavage rather than its enhanced production. This is indicated by decreased catalase and glutathione peroxidase activity together with a parallel absence of significant changes in superoxide dismutase (SOD) activity. Slight fluctuation of reduced glutathione level and the pronounced increase of glucose-6-phosphate dehydrogenase (G6PD) activity were detected. Strong (5 %) but not moderate (10 %) lack of oxygen led to a sharp increase in formation of cellular nitrite ions by alveolar macrophages. In general, our data showed that high temperature did not lead to any qualitative shifts of defined hypoxia-derived changes in oxidant/antioxidant balance in alveolar macrophages, but promoted sensitivity of cells to oxygen shortage.     

Stereochemistry of the enolization of scytalone by scytalone dehydratase

In D(2)O, scytalone exchanges its two C2 hydrogen atoms for deuterium atoms at different rates. At pD 7.0 and 25 degrees C, half-lives for the exchanges are 0.8 and 10 days for the pro-S and pro-R hydrogens, respectively. The differential exchange rates allow for the preparation of multiple scytalone samples (through incubation of scytalone in D(2)O and then back exchanging with H(2)O) having differential levels of deuterium enrichment at the C2 pro-S and pro-R positions. From these samples, the stereochemical preference for hydrogen abstraction during the dehydration reaction mediated by the enzyme scytalone dehydratase was determined. At pH 7. 0, deuterium at the pro-S position has little effect on enzyme catalysis, whereas deuterium at the pro-R position produces kinetic isotope effects of 2.3 (25 degrees C), 5.1 (25 degrees C), and 6.7 (6.8 degrees C) on k(cat), k(cat)/K(m), and the single-turnover rate, respectively. The results are fully consistent with the enzyme catalyzing a syn elimination through an E1cb-like mechanism. The syn elimination is compatible with the interactions realized between a scytalone boat conformation and key active site residues as modeled from multiple X-ray crystal structures of the enzyme in complexes with inhibitors.     

Effect of hydroxylated fullerene C60(OH)25 on macrophage plasma membrane integrity

Our study has shown that the damaging effect of hydroxylated fullerene C60(OH)25 on mouse peritoneal macrophage plasma membranes increased when we enlarged the concentration of fullerene in the incubation media (from 0.005 to 0.5 mg/ml), the incubation temperature (from 22 degrees C to 37 degrees C) and the time of incubation (from 30 to 90 min). In conditions of the H2O2-induced membrane damage, fullerene was observed to intensify the H2O2-induced damaging effect at a concentration of 0.05 mg/ml and reduce it at a concentration of 0.5 mg/ml. In conditions of the UV-induced membrane damage, it was discovered that the damaging effect of UV increased when C60(OH)25 nanoparticles were added to the incubation media before irradiation and decreased when they were added after irradiation. Eventual participation of ROS in damaging effects of C60(OH)25 was discussed.     

Estimation of protease activity in soils at low temperatures by casein amendment and with substitution of buffer by demineralized water

The aim of this work was to modify the method of Ladd and Buttler (1972), by substituting Tris-HCl buffer (pH 8.52) with demineralized water (DEMI H(2)O), in order to assess its suitability for measurement of casein-protease activity at pH levels close to those of real soil in H(2)O. Measurements were undertaken over a range of incubation temperatures from 3 to 49 degrees C. Testing was performed on one organic soil and two different mineral soils. The substitution of Tris-HCl buffer by DEMI H(2)O at 49 degrees C decreased casein-protease activity to 67.25% in mineral soil and to 53.76% in organic soil. With decreasing temperature casein-protease activity decreased the most in organic soil, i.e., 0.07% of original its value at 3 degrees C. The incubation period was extended to maximally 336 h at 3 degrees C to totally obtain >10.0% of L-tyrosine equivalents released at optimum or close to optimum temperature and pH conditions. The Q(10) values of casein-protease activity measured after substituting Tris-HCl buffer with DEMI H(2)O were unexpectedly high. Between the temperatures of 3 and 49 degrees C Q(10) ranged from 3.46 to 4.25, whereas between 3 and 25 degrees C Q(10) ranged from 6.78 to 11.08. Therefore, the modified method of Ladd and Buttler (1972) presented can be used for measurement of soil casein-protease activity under pH conditions close to that of real soil pH and at an averaged soil temperatures measured in the field. This modification makes possible an expression of soil casein-protease activity potential - when being combined with measurements of casein-protease activity under optimum or close to optimum temperature and pH conditions, if high concentration of casein is present.     

Thermoregulatory physiology of the Crested Pigeon<Emphasis Type="Italic"> Ocyphaps lophotes</Emphasis> and the Brush Bronzewing<Emphasis Type="Italic"> Phaps elegans</Emphasis>

The metabolic physiology of the Crested Pigeon (Ocyphaps lophotes) and the Brush Bronzewing (Phaps elegans) is generally similar to that expected for birds of their size, but the Crested Pigeon has a number of characteristics which would aid survival in hot and dry regions. Body temperature increased similarly for the Crested Pigeon (from 38.8 degrees C to 41.5 degrees C) and the Brush Bronzewing (39.3 degrees C to 41.4 degrees C) over ambient temperatures (T(a)s) from 10 degrees C to 35 degrees C. Both species became hyperthermic (body temperature, T(b)>42 degrees C) at T(a)=45 degrees C. Basal metabolic rate of the Crested Pigeon (0.65 ml O(2) g(-1) h(-1) at 40 degrees C) was approximately 71% of that predicted for a columbid bird, while BMR of the Brush Bronzewing (0.87 ml O(2) g(-1) h(-1) at 20 degrees C to 40 degrees C) was approximately 102% of predicted. Total evaporative water loss increased exponentially with T(a) for both species, from <1 mg H(2)O g(-1) h(-1) at 10 degrees C to >12 mg H(2)O g(-1) h(-1) at 45 degrees C. It was similar and low for both species at T(a)<30 degrees C, but was higher for the Brush Bronzewing than the Crested Pigeon at T(a)>30 degrees C. Ventilatory minute volume matched oxygen consumption, such that oxygen extraction efficiency did not change with T(a) and was similar for both species (approximately 20%). Expired air temperature was considerably lower than T(b) for both species at T(a)<35 degrees C, potentially reducing respiratory water loss by approximately 65% at T(a)=10 degrees C to approximately 30% at T(a)=35 degrees C. Cutaneous evaporative cooling was significant for both species, with skin resistance decreasing as T(a) increased. The Crested Pigeon had a lower skin resistance than the Brush Bronzewing at T(a)=45 degrees C. The Brush Bronzewing had apparently reached its maximum cutaneous water loss at 30 degrees C and relied on panting to cool at higher T(a).     

Secretion of endogenous regulators of Na K ATPase by isolated rat duodenum in osmotic stimulation of its mucous membrane]

The experiments in vitro have shown that perfusion of the isolated duodenum cavity in rats by hypotonic (20 mosmol/l H2O) or hypertonic (500 mosmol/l H2O) solutions of NaCl and mannitol during 10 min stimulates secretion of endogenic factors (activators or inhibitors of enterocytes of Na+, K(+)-ATPase) into the serous incubation solution. Contact of the duodenum mucose surface with isotonic (300 mosmol/l H2O) solutions does not stimulate the secretion of this enzyme regulators. Endogenic substance are thermostable: they retain activity relative to Na+, K+ ATPase of enterocytes after heating (100 degrees C, 10 min duration) of serous incubation solutions.     

Effects of temperature and fertilizer on activity and community structure of soil ammonia oxidizers

We investigated the effect of temperature on the activity of soil ammonia oxidizers caused by changes in the availability of ammonium and in the microbial community structure. Both short (5 days) and long (6.5, 16 and 20 weeks) incubation of an agricultural soil resulted in a decrease in ammonium concentration that was more pronounced at temperatures between 10 and 25 degrees C than at either 4 degrees C or 30-37 degrees C. Consistently, potential nitrification was higher between 10 and 25 degrees C than at either 4 degrees C or 37 degrees C. However, as long as ammonium was not limiting, release rates of N2O increased monotonously between 4 and 37 degrees C after short-term temperature adaptation, with nitrification accounting for about 35-50% of the N2O production between 4 and 25 degrees C. In order to see whether temperature may also affect the community structure of ammonia oxidizers, we studied moist soil during long incubation at low and high concentrations of commercial fertilizer. The soil was also incubated in buffered (pH 7) slurry amended with urea. Communities of ammonia oxidizers were assayed by denaturant gradient gel electrophoresis (DGGE) of the amoA gene coding for the alpha subunit of ammonia monooxygenase. We found that a polymerase chain reaction (PCR) system using a non-degenerated reverse primer (amoAR1) gave the best results. Community shifts occurred in all soil treatments after 16 weeks of incubation. The community shifts were obviously influenced by the different fertilizer treatments, indicating that ammonium was a selective factor for different ammonia oxidizer populations. Temperature was also a selective factor, in particular as community shifts were also observed in the soil slurries, in which ammonium concentrations and pH were better controlled. Cloning and sequencing of selected DGGE bands indicated that amoA sequences belonging to Nitrosospira cluster 1 were dominant at low temperatures (4-10 degrees C), but were absent after long incubation at low fertilizer treatment. Sequences of Nitrosospira cluster 9 could only be detected at low ammonium concentrations, whereas those of Nitrosospira cluster 3 were found at most ammonium concentrations and temperatures, although individual clones of this cluster exhibited trends with temperature. Obviously, ammonia oxidizers are able to adapt to soil conditions by changes in the community structure if sufficient time (several weeks) is available.     

Photolysis of N-hydroxpyridinethiones: a new source of hydroxyl radicals for the direct damage of cell-free and cellular DNA.

N-Hydroxypyridine-2-thione (2-HPT), known to release hydroxyl radicals on irradiation with visible light, and two related compounds, viz. N-hydroxypyridine-4-thione (4-HPT) and N-hydroxyacridine-9-thione (HAT), were tested for their potency to induce DNA damage in L1210 mouse leukemia cells and in isolated DNA from bacteriophage PM2. DNA single-strand breaks and modifications sensitive to various repair endonucleases (Fpg protein, endonuclease III, exonuclease III, T4 endonuclease V) were quantified. Illumination of cell-free DNA in the presence of 2-HPT and 4-HPT gave rise to damage profiles characteristic for hydroxyl radicals, i.e. single-strand breaks and the various endonuclease-sensitive modifications were formed in the same ratios as after exposure to established hydroxyl radical sources. In contrast, HAT plus light gave rise to a completely different DNA damage profile, namely that characteristic for singlet oxygen. Experiments with various scavengers (t-butanol, catalase, superoxide dismutase) and in D2O as solvent confirmed that hydroxyl radicals are directly responsible for the DNA damage caused by photoexcited 2-HPT and 4-HPT, while the damage by HAT plus light is mediated by singlet oxygen and type I reactions. The type of DNA damage characteristic of hydroxyl radicals was also observed in L1210 mouse leukemia cells when treated with 2-HPT plus light or with H2O2 at 0 degrees C. t-Butanol (2%) inhibited the cellular DNA damage by approximately 50%. A dose of 2-HPT plus light that generated single-strand breaks at a frequency of 5 x 10(-7)/bp was associated with 50% cell survival. No DNA damage and cytotoxicity was observed after treatment with 2-HPT in the dark. We propose that 2-HTP and 4-HTP may serve as new agents to study the consequences of DNA damage induced by hydroxyl radicals in cells. In addition, the data provide direct evidence that hydroxyl radicals are ultimately responsible for the genotoxic effects caused by H2O2 in the dark.     

Effect of modified Fenton's reaction on microbial activity and removal of PAHs in creosote oil contaminated soil

This study describes the removal of polycyclic aromatic hydrocarbons (PAHs) from creosote oil contaminated soil by modified Fenton's reaction in laboratory-scale column experiments and subsequent aerobic biodegradation of PAHs by indigenous bacteria during incubation of the soil. The effect of hydrogen peroxide addition for 4 and 10 days and saturation of soil with H(2)O(2) on was studied. In both experiments the H(2)O(2) dosage was 0.4 g H(2)O(2)/g soil. In completely H(2)O(2)-saturated soil the removal of PAHs (44% within 4 days) by modified Fenton reaction was uniform over the entire soil column. In non-uniformly saturated soil, PAH removal was higher in completely saturated soil (52% in 10 days) compared to partially saturated soil, with only 25% in 10 days. The effect of the modified Fenton's reaction on the microbial activity in the soil was assessed based on toxicity tests towards Vibrio fischeri, enumeration of viable and dead cells, microbial extracellular enzyme activity, and oxygen consumption and carbon dioxide production during soil incubation. During the laboratory-scale column experiments, the toxicity of column leachate towards Vibrio fischeri increased as a result of the modified Fenton's reaction. The activities of the microbial extracellular enzymes acetate- and acidic phosphomono-esterase were lower in the incubated modified Fenton's treated soil compared to extracellular enzyme activities in untreated soil. Abundance of viable cells was lower in incubated modified Fenton treated soil than in untreated soil. Incubation of soil in serum bottles at 20 degrees C resulted in consumption of oxygen and formation of carbon dioxide, indicating aerobic biodegradation of organic compounds. In untreated soil 20-30% of the PAHs were biodegraded during 2 months of incubation. Incubation of chemically treated soil slightly increased PAH-removal compared to PAH-removal in untreated soil.     

Renal excretion of 8-oxo-7,8-dihydro-2'-deoxyguanosine in Wistar rats with increased O(2) consumption due to cold stress

DNA damage by reactive oxygen species is of special interest in the development of cancer and in aging. The renally excreted amount of 8-oxo-7,8-dihydro-2'-deoxyguanosine (oxo(8)dG) is a potential noninvasive marker of oxidative DNA damage. The respiratory chain of mitochondria is one source for the formation of reactive oxygen species. In the present study we investigated in Wistar rats (n = 7; mean body weight at start, 307.4 +/- 11 g) the effect of an increased O(2) consumption, i.e., energy expenditure, due to cold stress on the renally excreted amount of oxo(8)dG. First, the rats were housed for 4 days at 23.5 degrees C (basic period, BP), and then for 6 days at 10 degrees C (cold stress period, CSP), and finally for 3 days at 23.5 degrees C (recovery period, RP). The O(2) consumption (L O(2)/day/kg weight) was significantly (P < 0.0001) on average 50% higher in CSP (69.0 +/- 3.9) than in BP (45.8 +/- 4.8), and similar in BP and RP (44.3 +/- 5.4). The average renal excretion of oxo(8)dG (pmol/day/kg weight) was significantly (P < 0.025) on average 13% higher in CSP (375.5 +/- 27.7) than in BP (333.2 +/- 47. 4) and similar in BP and RP (331.8 +/- 34.3). Maximum increase in oxo(8)dG excretion of on average 17% was on the third to fifth day of the CSP. This study reveals that an increase in O(2) consumption of 50% resulted in a much lower increase in the renal excretion of oxo(8)dG.     

Deuterium oxide stabilizes conformation of tubulin:a biophysical and biochemical study

The present study was aimed to elucidate the mechanism of stabilization of tubulin by deuterium oxide (D(2)O). Rate of decrease of tryptophan fluorescence during aging of tubulin at 4 degrees C and 37 degrees C was significantly lower in D(2)O than in H(2)O. Circular dichroism spectra of tubulin after incubation at 4 degrees C, suggested that complete stabilization of the secondary structure in D(2)O during the first 24 hours of incubation. The number of available cysteine measured by DTNB reaction was decreased to a lesser extent in D(2)O than in H(2)O. During the increase in temperature of tubulin, the rate of decrease of fluorescence at 335 nm and change of CD value at 222 nm was lesser in D(2)O. Differential Scanning calorimetric experiments showed that the T(m) values for tubulin unfolding in D(2)O were 58.6 degrees C and 62.17 degrees C, and in H(2)O those values were 55.4 degrees C and 59.35 degrees C.     

Effects of temperature on metabolism,ventilation, and oxygen extraction in the southern brown bandicoot Isoodon obesulus (Marsupialia: Peramelidae)

The effects of ambient temperatures (T(a)) from 10 degrees to 35 degrees C on metabolism, ventilation, and oxygen extraction were examined for the southern brown bandicoot (Isoodon obesulus). Oxygen consumption (VO2) followed the pattern typical for endotherms, decreasing with increasing T(a) from 10 degrees to 25 degrees C. It did not significantly change between Ta=25 degrees and 35 degrees C (the thermoneutral zone). VO2 was approximately 2.4 times higher at Ta=10 degrees C (0.967 mL O(2) g(-1) h(-1)) compared with basal (0.410 mL O(2) g(-1) h(-1)) at Ta=30 degrees C. While the metabolic rates of the bandicoots were basal at Ta=30 degrees C, respiratory frequency (f(R)) was 24.6 breaths min(-1), tidal volume (V(T)) was 7.79 mL, minute volume (V(I)) was 191.3 mL min(-1), and oxygen extraction efficiency (EO2) was 26.8%. Increased VO2 at Ta< or =25 degrees C was associated with a large increase in V(I) due to increases in V(T) and f(R). A greater proportion of the change was due to the increase in tidal volume. EO2 was constant at approximately 26% for all T(a) up to and including 30 degrees C. At Ta=35 degrees C, EO2 decreased to 17.7%, f(R) increased to 35.6 breaths min(-1), and V(T) decreased to 7.22 mL. The metabolic and ventilatory physiology of the southern brown bandicoot are typical of an unspecialized medium-sized marsupial.     

Human beta-interferon incubated with muscle homogenate is protected by albumin but not by proteinase inhibitors.

The scarce bioavailability of beta-interferon (IFN-beta) after intramuscular administration is probably due either to the binding of IFN-beta to interstitial matrix, or to lymphatic absorption and/or to local breakdown by lysosomal proteinases from muscle. In this work, we first showed that after intramuscular injection, the apparent bioavailability of natural human IFN-beta is about 10% of that of recombinant IFN-alpha 2 and then we evaluated the effects of proteinase inhibitors and albumin on IFN-beta incubated at 37 degrees C with muscle homogenate. IFN biological activity decreased spontaneously by about 20% after incubation for 6 hr at 37 degrees C in Hanks' solution, but it was almost completely lost after incubation with muscle homogenate. Proteinase inhibitors (alpha 1-antitrypsin, alpha 2-macroglobulin, aprotinin, soybean trypsin inhibitor, leupeptin, EP-459, and EP-475) failed to block the inactivation of IFN-beta by muscle proteinases, whereas albumin exerted a partial but consistent protection.     

Labeling and quality control of 188Re-lanreotide.

Lanreotide was labelled with 188Re obtained from 188W/188Re generator, using stannous ion as reducing agent, ascorbic acid as stabilizers and hydroxy ethylidene bisphosphonate (HEDP) as intermediary ligand at different molar ratios, pH and incubation times. Best yields (>95%) were obtained using molar ratios SnF2/lanreotide, ascorbic/lanreotide and HEDP/lanreotide of 40, 12 and 260, respectively, pH 1-2 with an incubation at 100 degrees C for 30 min. Quality control evaluation and stability of the radiolabel compound was done by the following selected methods: chromatography in Whatman 3 MM with MEK and NaCl 0.15 M as solvents, ITLC-SG with ethanol-HCl 0.01N (90:10); reverse phase extraction cartridge (Sep-pak C18, Waters Associated) and RP-HPLC with radiometric and UV detection (220 nm) using MCH-5 n-capp column with linear gradient from 90% H2O (TFA 0.1%): 10% ACN (TFA 0.1%) up to 10% H2O (TFA 0.1%):90% ACN (TFA 0.1%) in 30 min, at flow 1 ml/min. Biodistribution in normal mice showed that 188Re-lanreotide is excreted mainly through the hepatobiliary system: more than 70% I.D. is present in gallbladder and intestines at 2 hr post injection. The stability of the 188Re-peptide bond by cysteine challenge test at 37 degrees C, during 2 and 24 hr of incubation time, reveals that approximately 300 and 100 molar ratio cys/peptide is required to displace 50% of the 188Re from the complex. In vitro stability of 188Re-lanreotide at room temperature (Rt) was demonstrated during 24 hr Future works must be done in order to investigate its binding capacity to somatostatin receptors.     

Hypoxia interferes with ABA metabolism and increases ABA sensitivity in embryos of dormant barley grains

Two mechanisms have been suggested as being responsible for dormancy in barley grain: (i) ABA in the embryo, and (ii) limitation of oxygen supply to the embryo by oxygen fixation as a result of the oxidation of phenolic compounds in the glumellae. The aim of the present work was to investigate whether hypoxia imposed by the glumellae interferes with ABA metabolism in the embryo, thus resulting in dormancy. In dormant and non-dormant grains incubated at 20 degrees C and in non-dormant grains incubated at 30 degrees C (i.e. when dormancy is not expressed), ABA content in the embryo decreased dramatically during the first 5 h of incubation before germination was detected. By contrast, germination of dormant grains was less than 2% within 48 h at 30 degrees C and embryo ABA content increased during the first hours of incubation and then remained 2-4 times higher than in embryos from grains in which dormancy was not expressed. Removal of the glumellae allowed germination of dormant grains at 30 degrees C and the embryos did not display the initial increase in ABA content. Incubation of de-hulled grains under 5% oxygen to mimic the effect of glumellae, restored the initial increase ABA in content and completely inhibited germination. Incubation of embryos isolated from dormant grains, in the presence of a wide range of ABA concentrations and under various oxygen tensions, revealed that hypoxia increased embryo sensitivity to ABA by 2-fold. This effect was more pronounced at 30 degrees C than at 20 degrees C. Furthermore, when embryos from dormant grains were incubated at 30 degrees C in the presence of 10 microM ABA, their endogenous ABA content remained constant after 48 h of incubation under air, while it increased dramatically in embryos incubated under hypoxia, indicating that the apparent increase in embryo ABA responsiveness induced by hypoxia was, in part, mediated by an inability of the embryo to inactivate ABA. Taken together these results suggest that hypoxia, either imposed artificially or by the glumellae, increases embryo sensitivity to ABA and interferes with ABA metabolism.