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Plant Physiology Mar 1988Photosynthetic carbon fixation in guard cells was reexamined in experiments with highly purified guard cell protoplasts from Vicia faba L. irradiated with red light. The...
Photosynthetic carbon fixation in guard cells was reexamined in experiments with highly purified guard cell protoplasts from Vicia faba L. irradiated with red light. The fate of (14)CO(2) (4.8 microcuries of NaHCO(3); final concentration: 100 micromolar) supplied to these preparations was investigated with two-dimensional paper, and thin layer chromatography. Rates of CO(2) fixation were 5- to 8-fold higher in the light than in darkness. Separation of acid-stable products into water-insoluble, neutral, and anionic fractions showed that more radioactivity was incorporated into the neutral fraction in the light than in the dark. In the dark, malate and aspartate comprised 90% of the radiolabel found in the anionic fraction, whereas in the light, radioactivity was also found in 3-phosphoglyceric acid (PGA), sugar monophosphates, sugar diphosphates, and triose phosphates. Phosphorylated compounds contained up to 60% of the label in the light-treated anionic fraction. Phosphatase treatment and rechromatography of labeled sugar diphosphate showed the presence of ribulose, a specific metabolite of the photosynthetic carbon reduction pathway (PCRP). In time-course experiments, labeled PGA was detected within 5 seconds. With time, the percentage of label in PGA decreased and that in sugar monophosphate increased. We conclude that PGA is a primary carboxylation product of the PCRP in guard cells and that the activity of the PCRP, and phosphoenolpyruvate-carboxylase is metabolically regulated.
PubMed: 16665973
DOI: 10.1104/pp.86.3.700 -
Journal of Nuclear Medicine : Official... May 1994SPECT imaging with 123I-labeled methyl 3 beta-(4-iodophenyl)tropane-2 beta-carboxylate ([123I]beta-CIT) in nonhuman primates has shown brain striatal activity, which...
UNLABELLED
SPECT imaging with 123I-labeled methyl 3 beta-(4-iodophenyl)tropane-2 beta-carboxylate ([123I]beta-CIT) in nonhuman primates has shown brain striatal activity, which primarily reflects binding to the dopamine transporter. The biodistribution and calculated radiation-absorbed doses of [123I]beta-CIT administered to eight healthy subjects were measured with attention to the accurate determination of organ time-activity data.
METHODS
Whole-body transmission images were obtained with a scanning line source for attenuation correction of the emission images. Following administration of 92.5 +/- 22.2 MBq (2.5 +/- 0.6 mCi) of [123I]beta-CIT, subjects were imaged with a whole-body imager every 30 min for 3 hr, every 60 min for the next 3 hr and at 12, 24 and 48 hr postinjection. Regional body conjugate counts were converted to microcuries of activity, with a calibration factor determined in a separate experiment using a distributed source of 123I.
RESULTS
The peak brain uptake represented 14% of the injected dose, with 2% of the activity approximately overlying the striatal region. Highest radiation-absorbed doses were to the lung (0.1 mGy/MBq, 0.38 rads/mCi), liver (0.087 mGy/MBq, 0.32 rads/mCi) and lower large intestine (0.053 mGy/MBq, 0.20 rads/mCi).
CONCLUSIONS
Iodine-123-beta-CIT is a promising SPECT agent for imaging of the dopamine transporter in humans with favorable dosimetry and high brain uptake.
Topics: Adult; Brain; Cocaine; Female; Humans; Iodine Radioisotopes; Male; Radiation Dosage; Tissue Distribution; Tomography, Emission-Computed, Single-Photon
PubMed: 8176456
DOI: No ID Found -
Plant Physiology Feb 1989The pedicel of tomato fruit (Lycopersicon esculentum Mill., cv ;Rutgers') of different developmental stages from immature-green (IG) to red was injected on the vine with...
The pedicel of tomato fruit (Lycopersicon esculentum Mill., cv ;Rutgers') of different developmental stages from immature-green (IG) to red was injected on the vine with 7 microcuries [(14)C(U)]sucrose and harvested after 18 hours. Cell walls were isolated from outer pericarp and further fractionated yielding ionically associated pectin, covalently bound pectin, hemicellulosic fraction I, hemicellulosic fraction II, and cellulosic fraction II. The dry weight of the total cell wall and of each cell wall fraction per gram fresh weight of pericarp tissue decreased after the mature-green (MG) stage of development. Incorporation of radiolabeled sugars into each fraction decreased from the IG to MG3 (locules jellied but still green) stage. Incorporation in all fractions increased from MG3 to breaker and turning (T) and then decreased from T to red. Data indicate that cell wall synthesis continues throughout ripening and increases transiently from MG4 (locules jellied and yellow to pink in color) to T, corresponding to the peak in respiration and ethylene synthesis during the climacteric. Synthesis continued at a time when total cell wall fraction dry weight decreased indicating the occurrence of cell wall turnover. Synthesis and insertion of a modified polymer with removal of other polymers may produce a less rigid cell wall and allow softening of the tissue integrity during ripening.
PubMed: 16666568
DOI: 10.1104/pp.89.2.477 -
Stomatologija 2007The aim of this study was to evaluate the effect of cyclic 3', 5' adenosin-monophosphate (cAMP) on DNA synthesis of embryonic alveolar bone in tissue culture.
UNLABELLED
The aim of this study was to evaluate the effect of cyclic 3', 5' adenosin-monophosphate (cAMP) on DNA synthesis of embryonic alveolar bone in tissue culture.
MATERIAL AND METHODS
Bone fragments were cultured in the medium composed of 80% medium 199, 15% horse serum, 4 mg/ml glucose, 100 microg/ml penicillin using the grid method. The explants were cultured up to 12 days. In the second series, the effect of cAMP in a concentration of 10(-6)M on bone during 12 days was studied. DNA synthesis was determined by calculating mitotic labelling indices for (3)H-thymidine incorporation into cells within cultured explants at 3 to 12 days. The medium was supplemented with 1 microCurie/ml (3)H-thymidine for 4 hours and processed for autoradiography. The mitotic labelling index was determined in the histological sections. All values wer presented as mean+/-standard deviation. Statistical significance was defined by p-values of 0.05 or less.
RESULTS
Morphological and statistical analysis showed that there were differences in mitotic incidence (MI) and silver grain densities over osteoblasts in control cultures and with cAMP. The mean value of MI was 4,627+/-1,001 in control and 7,706+/-1,188 in the cultures where cAMP was added (p<0.05).
CONCLUSION
Thus cAMP inhibited bone resorption and stimulated new bone formation in tissue culture. This study provides a novel concept that may help to identify new therapeutic targets.
Topics: Alveolar Process; Animals; Autoradiography; Bone Matrix; Bone Resorption; Calcification, Physiologic; Cell Count; Cell Proliferation; Culture Media; Cyclic AMP; DNA; Mice; Mitotic Index; Osteoblasts; Osteogenesis; Radiopharmaceuticals; Thymidine; Tissue Culture Techniques; Tritium
PubMed: 18303273
DOI: No ID Found -
The Western Journal of Medicine Aug 1974Gallium-67 ((67)Ga) citrate was administered intravenously (50 microcuries per kg of body weight) to patients in whom acute and chronic urinary tract infections were...
Gallium-67 ((67)Ga) citrate was administered intravenously (50 microcuries per kg of body weight) to patients in whom acute and chronic urinary tract infections were suspected. Scanning was done, using both the Anger-type scintillation camera and the rectilinear scanner, 24 to 78 hours after injection of the isotope. The preliminary results imply that (67)Ga renal uptake is present in patients with pyelonephritis whether overt or silent, as well as in patients with uretero-sigmoidostomies. However, (67)Ga renal uptake is not present in patients with radiographic evidence of chronic pyelonephritis without active infection and in patients without renal disease.
Topics: Acute Disease; Adult; Chronic Disease; Diagnosis, Differential; Female; Gallium; Humans; Kidney; Male; Pyelonephritis; Radioisotopes; Radionuclide Imaging
PubMed: 4847435
DOI: No ID Found -
Journal of Nuclear Medicine : Official... Feb 1982The absorbed radiation dose that would result from the oral or intravenous administration of SeHCAT (23-[75Se]selena-25-homotaurocholate) has been calculated using the... (Comparative Study)
Comparative Study
The absorbed radiation dose that would result from the oral or intravenous administration of SeHCAT (23-[75Se]selena-25-homotaurocholate) has been calculated using the MIRD tables and formulas and data from measurements of whole-body distribution and from long-term whole-body counting in rats, mice, and man. When SeHCAT is administered to normal subjects, the gallbladder is the critical organ, receiving 12 mrad (oral dose) or 22 mrad (i.v.) per microcurie. The whole-body dose is 1 mrad/microCi, whatever the route of administration. In severe hepatic failure the liver might receive 200 mrad/microCi. The activity likely to be used in routine clinical practice is 10 microCi. Where a whole-body counter is used, an activity of 1 microCi has proved adequate. Even at an administered activity of 25 microCi, the absorbed dose is small compared with established techniques of investigating the gastrointestinal tract.
Topics: Administration, Oral; Animals; Body Burden; Cholestasis; Energy Transfer; Gallbladder; Humans; Injections, Intravenous; Mice; Radiation Dosage; Radioisotopes; Rats; Selenium; Taurocholic Acid; Time Factors; Tissue Distribution; Whole-Body Counting
PubMed: 6799623
DOI: No ID Found -
Plant Physiology Jun 1967The incorporation of (3)H-thymidine into nuclear DNA of leaf cells of Nanthium pennsylvanicum was studied as a function of concentration and specific activity of the...
The incorporation of (3)H-thymidine into nuclear DNA of leaf cells of Nanthium pennsylvanicum was studied as a function of concentration and specific activity of the radioisotope. From the assessment of the average number of grains per nucleus and the percent of labeled nuclei, it was concluded that the incorporation was a linear function of concentration of the exogenous radioisotopic solution and a logarithmic function of the incubation time. Ten microcuries per milliliter on the average yielded 20% of labeled nuclei with 18 grains per nucleus. Seven-fold increase in concentration only doubled the amount of (3)H-thymidine incorporated. The lamina regions near the vein incorporated a significantly greater amount of the radioisotope than the lamina region at some distance from the vein. The specific activities of 2, 3.35, 6.7 and 15.3 c/mmole had no effect upon the amount of (3)H-thymidine incorporated, if the amount of microcuries of the incubation solution was the same in each activity. Considering the total number of molecules, the estimated rates of incorporation indicated that at the activity of 2 c/mmole, the system operated with about 7 times higher rates as compared with the activity of 15.3 c/mmole.
PubMed: 16656575
DOI: 10.1104/pp.42.6.814 -
Journal of Nuclear Medicine : Official... Feb 1986A simple, inexpensive dual-detector system has been developed for measurement of positronemitting receptor-binding drugs in the human brain. This high efficiency...
A simple, inexpensive dual-detector system has been developed for measurement of positronemitting receptor-binding drugs in the human brain. This high efficiency coincidence counting system requires that only a few hundred microcuries of labeled drug be administered to the subject, thereby allowing for multiple studies without an excessive radiation dose. Measurement of the binding of [11C]carfentanil, a high affinity synthetic opiate, to opiate receptors in the presence and in the absence of a competitive opiate antagonist indicates the potential utility of this system for estimating different degrees of receptor occupation in the human brain.
Topics: Binding, Competitive; Brain; Calibration; Carbon Radioisotopes; Electrons; Equipment Design; Fentanyl; Humans; Naloxone; Radioligand Assay; Receptors, Opioid; Scintillation Counting
PubMed: 3012020
DOI: No ID Found -
Journal of Nuclear Medicine : Official... Aug 1979The EMT-6 sarcoma-like tumor of BALB/c mice can be grown as a solid subcutaneous transplantable tumor in vivo or as a monolayer culture in vitro. We have studied the...
The EMT-6 sarcoma-like tumor of BALB/c mice can be grown as a solid subcutaneous transplantable tumor in vivo or as a monolayer culture in vitro. We have studied the uptake of gallium-67 by this tumor growing subcutaneously on the backs of 6-week-old BALB/c mice. After i.v. administration of Ga-67 citrate, tumor uptakes were as high as any others reported for mouse tumors. Also, for unknown reasons, there was appreciable reduction in tumor uptake with increasing amounts of Ga-67 citrate, even in the microcurie range. Furthermore, when mouse serum is prelabeled with Ga-67 and then injected, the EMT-6 uptake is greater than with Ga-67 administered as citrate (p less than 0.02). We believe that the finding of avid Ga-67 uptake in vivo helps to establish this unique in vivo/in vitro tumor system as a valid experimental model for studies regarding the mechanism of Ga-67 accumulation by neoplastic tissue.
Topics: Animals; Gallium; Gallium Radioisotopes; Mice; Mice, Inbred BALB C; Neoplasm Transplantation; Receptors, Drug; Sarcoma, Experimental; Transferrin; Transplantation, Homologous
PubMed: 541731
DOI: No ID Found -
Plant Physiology May 1973Eastern white pines (Pinus strobus L.) in their 3rd year of growth photoassimilated 35, 110, 220, or 400 microcuries of (14)CO(2) on a single occasion in the spring when...
Eastern white pines (Pinus strobus L.) in their 3rd year of growth photoassimilated 35, 110, 220, or 400 microcuries of (14)CO(2) on a single occasion in the spring when needle expansion was occurring. Once assimilated into organic products and translocated to various sinks, the retained (14)C represented an internal chronic source of ionizing radiation to the plant. About 2.5 months later, the pines were harvested, and the distribution of (14)C activity was determined. In addition, new needle lengths, fresh weights, and rates of processes involving CO(2) exchange were measured.All parameters measured were affected in those pines which initially assimilated 220 or 400 microcuries of (14)CO(2), whereas no significant differences were observed between control plants and those initially assimilating 35 microcuries. Plants incorporating 110 microcuries were intermediate in their responses. The percentage of assimilated (14)C retained by the plants decreased as the initial activity of assimilated (14)C increased, with the losses of (14)C occurring through both respiration and the shedding of needles. The pines which assimilated 35 microcuries of (14)CO(2) retained about 70% of the (14)C; those which assimilated 400 microcuries retained only about 28%. The distribution of the (14)C activity recovered from all the plants was essentially the same; about 65% of the total (14)C recovered was in the new needles and 13% in the roots.
PubMed: 16658445
DOI: 10.1104/pp.51.5.954