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PubMed1976

Photochemical studies and ultraviolet sensitization of Escherichia coli thymidylate kinase by various halogenated substrate analogs.

The effect of 5-iodo-2'-deoxyuridine monophosphate (IdUMP), various 5-halogenated-5'-azido-2', 5' -dideoxyuridine derivatives, 2'-deoxy-6-azauridine (AzdUrd), and its halogenated analogs on the ultraviolet sensitization of Escherichia coli thymidylate kinase has been investigated. Only those compounds iodinated in position 5 enhance the rate of ultraviolet inactivation of this enzyme. However, 5'-azido nucleosides with iodo, bromo, chloro, or fluoro substituents in position 5 neither protect nor sensitize thymidylate kinase to ultraviolet inactivation. Thymidine 5'-monophosphate partially protects the enzyme against ultraviolet inactivation either in the presence or absence of ultraviolet-sensitizing iodinated analogs. Magnesium ion does not enhance the ultraviolet inactivation of thymidylate kinase by 5-iodinated nucleoside analogs. The kinatic data support an active site-directed enhancement of the enzyme to ultraviolet inactivation by 5-iodo-2'-deoxyuridine monophosphate, since the concentration of IdUMP required to attain 50% maximal enhancement is 0.24 mM which is in good agreement with its Ki of 0.18 mM. When either [125I]IdUMP or [2-14C]IdUMP was irradiated with the enzyme, both radioactivities were associated with the enzyme, however only with the 14C analog was the amount bound at half-saturation essentially equal to the amount required to inactivate the enzyme by 50%. These data support the hypothesis that the active entity in the enhancement by IdUMP of thymidylate kinase inactivation during ultraviolet irradiation is the uridylate free radical which is formed photochemically from IdUMP. Photochemical studies of 6-azauracil (AzUra), 2'-deoxy-6-azauridine, and 5-iodo-2'-deoxy-6-azauridine (IAzdUrd) were performed. Photolysis of IAzdUrd in the presence of a hydrogen donor yields AzdUrd which upon further photolysis yields the photohydrate. The photohydrate of AzdUrd when incubated in the dark at pH 5.2 is 90% converted back to AzdUrd, whereas the photohydrate of AzUra is only partially (20%) converted to AzUra. The rate of deiodination of IAzdUrd is 2.1-fold greater than that of IdUMP. Although the Ki of IdUMP and IAzdUrd is similar, the increased photosensitivity of the aza analog accounts for the much greater enhancement of ultraviolet inactivation of thymidylate kinase. The ability of a compound to enhance the ultraviolet inactivation of deoxythymidylate kinase is correlated with the potential of the compound to produce a free radical rather than a photohydrate when the enzyme-substrate analog complex is irradiated.

Escherichia coli↗

PubMed1984

Tumor uptake of radiolabelled pyrimidine bases and pyrimidine nucleosides in animal models: VI. 1-(3'-[36Cl]-chloro-, 1-(3'-[82Br]-bromo- and 1-(3'-[123I]-Iodo-3'-deoxy-beta-D-arabinofuranosyl)uracil.

3'-Radiohalogenated (36Cl, 82Br and 123I) "arabino" pyrimidine nucleosides were evaluated as potential tumor diagnostic agents in tumor bearing animals. No preferential tissue uptake was observed. The compounds were excreted mainly unchanged in the urine. The 3'-[36Cl]- and 3'-[82Br]-3'-deoxyarabino nucleosides exhibited biliary uptake. The low uptake of injected radioactivity by the tumor was probably due to the combined effects of the lack of a C-3' hydroxyl group in the "ribo" configuration, the presence of a halogen, the structural rigidity imposed by the presence of a halogen and the short biological half-lives of the compounds.

Animals↗

PubMed1988

The preparation of porcine (Tyr-A14-2H) insulin and its characterization by mass spectrometry.

The title compound was prepared by catalytic deiodination of (Tyr-A14-3-I) insulin with deuterium gas. Under special conditions (large excess of PdO in CH3OD/D2O at pH 9.2) developed to minimize problems due to poisoning of the catalyst, deuterated insulin was produced in yields of about 35% after purification by reversed phase HPLC. For analysis, the deuterated insulin was digested with V8 protease and was shown by mass spectrometry to have incorporated deuterium to an extent of 96.6 atom %, exclusively in a pentapeptide containing Tyr A14. The title compound should prove useful to those workers studying insulin by mass spectrometry, and use of the method with tritium gas in place of deuterium should permit the preparation of a specifically labelled radioactive insulin analogue which behaves identically to the natural hormone.

Animals↗

PubMed1993

Improved synthesis of (5Z)-7-(3-endo-[(benzenesulfonamido)-bicyclo[2.2.1]heptyl]hept-5-enoic acid (S-145) derivatives and their iodine-125-labeled radioligands for the study of thromboxane A2 receptor.

An improved synthetic scheme for (5Z)-7-(3-endo-[(benzenesulfonamido)-bicyclo[2.2.1]heptyl)-h ept-5-enoic acid (S145) and its analogs has been designed. The procedure involves direct sulfonylation of 2-allyl-3-aminobicyclo[2.2.1]heptane intermediate followed by ozonolysis and addition of a C5 carboxyl unit. The yield of the final product was significantly improved. (5Z)-7-(3-endo-[(4-iodobenzenesulfonamido)-bicyclo [2.2.1]heptyl)hept-5-enoic acid (HS-145) and (5Z)-7-(3-endo-[(4-hydroxy-benzensulfonamido)-bicyclo [2.2.1]heptyl)hept-5-enoic acid (HS-145) were synthesized directly without any protection and deprotection steps. [125I](5Z)-7-(3-endo-[(4- iodobenzensulfonamido)-bicyclo[2.2.1]heptyl)hept-5-enoic acid ([125I]HS-145) was prepared from IS-145 through an organotin intermediate and [125I]sodium iodide with high specific radioactivity and good recovery of radioactivity. [125I](5Z)-7-(3-endo-[(4-hydroxy 3-iodo-benzenesulfonamido)-bicyclo[2.2.1]-heptyl)hept-5-enoic acid ([125I]HS-145) was prepared by direct iodination with sodium iodide using a modified chloramine-T method. Both [125I]HS-145 and [125I]HS-145 were found to be valuable radioligands for studying thromboxane A2 (TXA2) receptor.

Blood Platelets↗

PubMed1984

Sodium butyrate-induced adhesion in mastocytoma cells.

Sodium butyrate induced adhesion of cultured mastocytoma p-815 cells to the surface of a standard tissue culture grade petri dish. The ratio of the number of adherent cells to that of total cells (adherent plus floating cells) was dependent on the serum concentration and on the dose of sodium butyrate. During approximately the first 6 hr after the addition of sodium butyrate, no cells adhered. The optimum conditions for adhesion were provided by 2 mM sodium butyrate and 15% fetal calf serum, 44 hr after addition of this compound. Morphologically, adherent cells consisted of spindle-shaped and round cells: the latter clustered to the former. Low concentrations of actinomycin D (0.005 microgram/mL) and of cycloheximide (0.5 microgram/mL) inhibited cell adhesion. Adherent cells were easily detached by 0.25% trypsin-0.02% EDTA but not by EDTA alone. Adherent mastocytoma cells which were cultured in the presence of 2 mM sodium butyrate, re-adhered to the surface of the dish. The ratio of adhesion in the second dish, however, was very low (35% after 2 hr incubation). Radioactive iodinated surface proteins of butyrate-treated adherent cells showed two new bands (70,000 and 92,000 D) which were not detected in control cells, but there was no difference in the extent of labeling of high molecular weight protein (250,000 D) between butyrate-treated and control cells.

Animals↗

PubMedDate not supplied

Synthesis and evaluation of 2-(3'-iodo-4'-aminophenyl)-6-hydroxybenzothiazole for in vivo quantitation of amyloid deposits in Alzheimer's disease.

A potent and brain permeable amyloid ligand has been identified as a lead compound capable of I-123/125-labelling for single photon emission computed tomography (SPECT) imaging. In this study, we report the synthesis and I-125-radiolabelling of Compound 6 and its in vitro and in vivo properties. Compound 6 [2-(3'-iodo-4'-aminophenyl)-6-hydroxybenzothiazole] bound to synthetic A beta(1-40) fibrils in a saturable manner, exhibiting an affinity (Ki) of 11+/-1.1 nM in a competitive binding assay using a tritiated thioflavin T analog ([3H]BTA-1) as radioligand. [125I]6 binding to synthetic A beta(1-40) fibrils fit a single-site model. [125I]6 exhibited several-fold higher binding to homogenates of frontal cortex from post-mortem Alzheimer's disease brain relative to age-matched control brain homogenates. No difference in binding was observed in cerebellum. The ratio of radioactivity concentration between frontal cortex and cerebellum was 6-fold higher in AD brain homogenates than the age-matched control. [125I]6 also readily penetrated the blood-brain barrier in normal control mice with an average radioactivity concentration of 6.43+/-0.62%ID/g detected in the whole brain at 2 min post i.v. injection. At 30 min, the radioactivity concentration decreased to 0.40+/-0.05%ID/g, indicating good clearance in the absence of amyloid deposits in the brain.

Alzheimer Disease↗

PubMed1996

Labeling of insulin with non-radioactive 127I and application to incorporation of radioactive 125I for use in receptor-binding experiments by high-performance liquid chromatography.

Conditions for the labeling of insulin with radioactive iodine isotopes were investigated by means of incorporation of non-radioactive 127I into the peptide. Either the chloramine-T (CT) or lactoperoxidase-hydrogen peroxide (LPO) technique was applied and reversed-phase high-performance liquid chromatography (RP-HPLC) was used for analysis of the reaction products. The LPO method provided the 127I-labeled peptide within 15-30 min, whereas the CT alternative yielded the labeled substrate even within 15 s. However, the latter reaction can only be controlled in a reproducible manner with difficulty and undesired side-reactions became increasingly prominent when the reaction time of 15 s was exceeded for only a few seconds. In another experiment, the LPO technique was applied for radiolabeling insulin with 125I. The product was first purified by size-exclusion chromatography (SEC) and then subjected to RP-HPLC. SEC yielded two peaks. The smaller one, which eluted at a slightly higher Kd value (accounting for about 14% of total radioactivity) predominantly consisted of material eluting at the column's void volume under the conditions of RP-HPLC, whereas the main SEC fraction (accounting for about 86% of total radioactivity) yielded a single peak, as shown by HPLC. The radioactive material attributable to the main SEC fraction revealed the expected receptor-binding properties, as evidenced by displacement experiments with non-radioactive insulin, as well as the action of tetradecanoyl phorbol acetate on the binding characteristics and thus indicating formation of a labeled hormone retaining biological activity.

Binding, Competitive↗

PubMed1984

Preparation of 125I-protein A usable for up to 10 months in immunoassays.

Chloramine-T iodination of protein A from Staphylococcus aureus and gel electrophoretic purification of the iodination mixture results in a stable tracer of high specific and functional activity. Following repeated gel electrophoresis of the tracer only a single component was observed. The specific activity of the 125I-protein A was between 30 and 55 muCi/micrograms. The binding of 125I-protein A to rabbit immunoglobulin exceeded 90% and the tracer competed effectively with unlabelled protein A in binding to cells incubated with sera containing surface antibodies. Storage of the tracer for up to 46 weeks resulted in a moderate decrease in maximal binding to immunoglobulin (from 91% to 64%), in TCA precipitable radioactivity (from 97% to 80%) and an approx. 30% decrease in the ability to detect cell bound immunoglobulin. It is concluded that gel electrophoretic purification of 125I-protein A produces a tracer with a very long shelf life.

Chloramines↗

PubMed1994

Determination of sulfated peptides by differential iodination.

A sequential approach was developed to label tyrosine sulfate and peptides containing tyrosine sulfate selectively. Amino acids and peptides containing tyrosine and tyrosine sulfate were first iodinated using chloramine-T-method. Reaction products were determined by RP-HPLC. Mono- and biiodination of tyrosine and several model peptides was achieved within 120 s incubation time. Iodination of free tyrosine sulfate and sulfated cholecystokinin26-33 was less than 5%. After desulfation of the reaction products with 1 N HCl successful radioiodination of desulfated tyrosine was carried out whereas tyrosine did incorporate radioactive iodine only 10%. As shown by RP-HPLC specific labeling of tyrosine sulfate containing peptides with 125iodine was achieved.

Amino Acid Sequence↗

PubMed1975

New immunolatex spheres: visual markers of antigens on lymphocytes for scanning electron microscopy.

New immunochemical reagents consisting of antibodies bound to small latex spheres were used as visual markers for the detection and localization of cell surface antigens by scanning electron microscopy. Cross-linked latex spheres of various sizes from 300 to 3,4000 A in diameter were synthesized by aqueous emulsion copolymerization of methacrylate derivatives containing hydroxyl and carboxyl functional groups. Proteins and other molecules containing primary amino groups were covalently bonded to the acrylic spheres under a variety of mild conditions by the aqueous carbodiimide, cyanogen bromide, and glutaraldehyde methods. For use in the indirect immunochemical-labeling technique, goat antibodies directed against rabbit immunoglobulins were bonded to the spheres. These immunolatex reagents were shown to bind only to cells (red blood and lymphocytes) which had previously been sensitized with rabbit antibodies against cell surface antigens. Mouse spleen lymphocytes with exposed immunoglobulins on their surface (B cells) were labeled with these spheres and distinguished from unlabeled or T lymphocytes by scanning electron microscopy. The distribution of Ig receptors on lymphocytes was also studied using the spheres as visual markers. When lymphocytes were fixed with glutaraldehyde and subsequently labeled with the immunolatex reagents, a random distribution was observed by scanning electron microscopy; a patchy distribution was observed when unfixed lymphocytes were used. These results are consistent with studies using ferritin-labeled antibodies (S. De Petris and M. Raff. 1973. Nature [Lond.]. 241:257.) and support the view that Ig receptors on lymphocytes undergo translational diffusion. In addition to serving as visual markers for scanning electron microscopy, these latex spheres tagged with fluorescent or radioactive molecules have applications as highly sensitive markers for fluorescent microscopy and as reagents for quantitative studies of cell surface antigens and other receptors.

Animals↗

PubMed1973

Radiation and pregnancy.

Irradiation during pregnancy may occur either as the result of radioactive pollution of the environment, or during a medical procedure using x-rays or radionuclides. While the former is usually unforeseeable, the latter is known and accepted by both physician and patient.Recent statistics estimate that about one quarter of pregnant women have had a radiographic experience during the pregnancy, either for obstetrical reasons or in the course of medical and dental examinations. The amount of radiation delivered to the fetus is in the range of one rad or less. Radionuclidic procedures may result in fetal radiocontamination, chiefly after placental transfer and fetal uptake. Radioiodine, radioactive calcium and selenomethionine are dangerous for the fetus, since they cross the placenta freely and are taken up by fetal tissues. The labelled proteins, radiocolloids and some mercury compounds remain in the maternal compartment and therefore can affect the fetus only through their gamma radiation at some distance from the fetus.The teratogenic effect, the leukemogenic threshold and the lowered resistance to neonatal infections have been demonstrated after irradiation with doses far higher than those encountered during diagnostic applications of ionizing radiation. Statistical data suggest an increase of susceptibility to leukemia in infancy after intra-uterine irradiation at a diagnostic level. Cytogenic analysis may.... offer valuable data for the establishment of the extent of radiation damage.

Chromosome Aberrations↗

PubMed1983

Synthesis of a 125I-radiolabeled penicillin for penicillin-binding proteins studies.

Radioiodination of penicillin X (p-hydroxybenzylpenicillin) with 125INa, using the chloramine-T method, is simple and almost quantitative. The product thus obtained can be used without further purification for the penicillin-binding proteins (PBPs) assay. The chemical structure of 125I-penicillin X is very close to that of penicillin G, and the affinity of the two compounds for the PBPs are very similar. 125I-penicillin X can then advantageously replace [14C]penicillin G in these experiments, as its specific radioactivity is 2000 Ci/mol, in our preparations, instead of about 50 Ci/mol; thus, the experimental procedure is simplified and the autoradiography exposure time is reduced to 12-48 h.

Autoradiography↗

PubMed1992

Neutral endopeptidase inhibition increases the urinary excretion and plasma levels of endothelin.

The pathway for removal of the circulating potent vasoconstrictor peptide, endothelin (ET), is unclear. To determine the contribution of neutral endopeptidase (NEP) to ET metabolism, urinary excretion (UETV) and plasma levels of ET (P(ET)) were measured after infusion of the NEP inhibitor (NEP-I), SQ 29,072 (30 mg/kg [n = 10] and 60 mg/kg [n = 6]), in anesthetized Munich Wistar rats. Both doses significantly increased UETV at 30, 60, and 90 minutes; the maximal effect was obtained 30 minutes after infusion, and the response was longer in rats pretreated with the higher dose of the inhibitor. P(ET) increased 36% and 55% (P less than or equal to .05) at 30 and 120 minutes after injection of the larger dose of SQ 29,072. We also studied the effect of NEP-I on the excretion of exogenous ET after the infusion of 125I-ET (1 microCi) in rats pretreated with either NEP-I or vehicle. In rats treated with the lower dose of the inhibitor, urinary radioactivity increased 2.1- and 1.5-fold (P less than or equal to .05 v control) after 30 and 60 minutes, respectively. After the higher dose of NEP-I, urinary radioactivity increased 2.7- and 1.7-fold (P less than or equal to .05). The distribution of the urinary radioactivity as defined by high-performance liquid chromatography (HPLC) showed that intact labeled ET accounts for only 6% to 9% of the total counts recovered in urine from control rats, while the remainder was either free iodine or other products of hydrolysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗

PubMed1992

Radioiodinated 1-(2-fluoro-4-iodo-2,4-dideoxy-beta-L-xylopyranosyl)-2-nitroimidazole: a novel probe for the noninvasive assessment of tumor hypoxia.

1-(2-Fluoro-4-iodo-2,4-dideoxy-beta-L-xylopyranosyl)-2-nitroimidazole (FIAZP) has been synthesized and labeled with radioiodine (125I). Radioiodinated FIAZP is one of a series of sugar-coupled 2-nitroimidazoles developed in our laboratory as probes for noninvasive scintigraphic assessment of tumor hypoxia. An in vivo biodistribution study with [125I]FIAZP in the murine BALB/c EMT-6 tumor model showed a tumor-to-blood ratio of 6, 24 h after injection, with 0.5% of the injected dose present per gram of tumor. These values are several times higher than the respective ratios and distribution values in any of the organs, with the exception of liver. Radioactivity from tissues other than tumor and liver declined with time, following the decline of blood radioactivity. Rapid whole-body elimination of radioactivity was observed (> 96% in 24 h). The thyroid showed little uptake of radioactivity, indicating minimal in vivo deiodination. 1-(2-Fluoro-4-iodo-2,4-dideoxy-beta-L-xylopranosyl)-2-nitroimidazo le appears to undergo hypoxia-dependent binding in tumor tissue at levels comparable to those of other sugar-coupled 2-nitroimidazoles. The potential for imaging with this compound is discussed.

Animals↗

PubMed1991

[Studies on microleakage of three kinds of dental restorative materials].

In this article we studied the microleakage of three kinds of dental restorative materials by using 131I label compounds and 3H label compounds. The results revealed that the radioactive isotope reverse diffusion method has the advantages of which it is quantitative and sensitive. It is an acceptable and feasible measuring method. Under the condition described in this article, microleakage phenomenon exists in all the test materials and the margin sealing ability of EB composite resins is superior to the others.

Composite Resins↗

PubMed1998

Influence of iodine-131 solution volume and storage time on in vitro dissolution.

OBJECTIVE: This investigation was conducted to determine the influence of 131I solution volume and storage time on the in vitro release of radioiodide from capsules. METHODS: In vitro dissolution profiles for 131I sodium iodide capsules compounded in a centralized nuclear pharmacy were determined using the USP XXIII Dissolution Test. Iodine-131 solution volumes of 0.05, 0.15 and 0.25 ml and storage times of 2, 5, 7 and 9 days were considered. RESULTS: By 80 min after initiation of the dissolution test, more than 95% of the 131I was released from capsules prepared with 0.15 and 0.25 ml of the 131I solution. The 0.05-ml capsules reached 95% at 55 min. Capsules prepared with 0.05 ml of solution and stored 2, 5, 7 or 9 days released over 95% of the radioactivity within 65 min. Capsules prepared with 0.25 ml of solution and stored for 2, 5, 7 or 9 days released over 95% of the 131I by 55 min after initiation of the dissolution test. CONCLUSION: Neither the different volume of radioactive sodium iodide solution used in the preparation of capsules nor the time of storage greatly influenced the release of 131I from the capsules. Based on dissolution profiles, it appears that the bioavailability of 131I would not be influenced by factors studied in this investigation.

Capsules↗

PubMed1991

Synthesis and properties of sulfhydryl-group-specific reagents containing 125I.

125I-containing compounds that react specifically with sulfhydryl groups were prepared in yields of 30 to 40% on the basis of starting 125I quantity. The synthetic precursors were commercially available heterobifunctional crosslinkers and the peptide L-arginyl-L-tyrosine. Two types of sulfhydryl specific reagents were prepared: 3-(2-pyridyldithio)propionylarginyl-[125I]-monoiodotyrosine, which permits reversible incorporation of 125I at sulfhydryl sites, and 3-maleimidopropionylarginyl- [125I]monoiodotyrosine, an irreversible labeling reagent. These products were isolated in a highly radiochemically pure form by C18 HPLC. The second-order rate constants for the reaction of 3-(2-pyridyldithio)propionylarginylmonoiodotyrosine and 3-maleimidopropionylarginylmonoiodotyrosine with N-acetylcysteine were 28 +/- 3 M-1 s-1 and 154 +/- 4 M-1 s-1, respectively, at pH 7.3. Storage of carrier-free 3-(2-pyridyldithio)propionylarginyl-[125I]monoiodotyrosine and 3-maleimidopropionylarginyl-[125I]monoiodotyrosine at -80 degrees C at a radioactive concentration of 0.4 mCi/ml resulted in conversion of 125I to species that did not react covalently with sulfhydryl groups. This process occurred with first-order kinetics and a t1/2 of 5.7 days for the pyridyldithio compound and 7.5 days for the maleimido compound. No conversion was observed during storage at -80 degrees C at radioactive concentrations of 0.02 mCi/ml or less. The labeling properties of these compounds were examined using red blood cell proteins as a test system. 3-(2-Pyridyldithio)propionylarginyl- [125I]monoiodotyrosine and maleimidopropionylarginyl-[125I]monoiodotyrosine reacted preferentially with membrane - associated sulfhydryl groups when incubated with intact red blood cells.

Blood Proteins↗

PubMed1992

Evaluation of N-alkyl derivatives of radioiodinated spiperone as radioligands for in vivo dopamine D2 receptor studies: effects of lipophilicity and receptor affinity on the in vivo biodistribution.

A series of radioiodinated spiperone (2'-ISP) derivatives bearing amide N-alkyl substituents (N-methyl-2'-ISP, N-ethyl-2'-ISP, and N-propyl-2'-ISP) were synthesized and evaluated as potential singlet photon emission computed tomographic radiopharmaceuticals for visualizing dopaminergic receptors. The lipophilicity of these ligands (i.e., the partition coefficient for octanol-phosphate buffer) increased as the chain length increased. Investigation of blood-brain barrier permeability in rats showed a parabolic relationship between the brain uptake index and the partition coefficient. In vitro competitive binding studies showed that the relative affinity for the dopamine D2 receptor was in the order of N-propyl-2'-ISP greater than 2'-ISP greater than N-methyl-2'-ISP approximately N-ethyl-2'-ISP. In vivo biodistribution studies showed that the initial brain uptake correlated fairly well with the brain uptake index and that the kinetics of the radioactivity specifically bound to the striatum were strongly influenced by the dopamine receptor binding affinity of the compounds. Thus, the in vivo behavior of these N-alkylated 2'-ISP derivatives involved a complex interplay between receptor affinity, lipophilicity, and blood-brain barrier permeability.

Animals↗