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At least 163 records · Page 9Linked to original sources
PubMed1995

A new 99mTc labelling method for leucocytes: in vitro and in vivo comparison with 99mTc-HMPAO.

A new method for the labelling of mixed leucocytes with 99mTc-tropolone was optimized and compared with a 99mTc-HMPAO leucocyte labelling procedure in vitro and in vivo. In the present study, leucocytes obtained from patients suffering from Crohn's disease, were isolated and labelled with 99mTc-HMPAO or labelled according the new 99mTc-tropolone procedure using 9.8 mM tropolone, 1 microM stannous chloride and 0.8 mM potassium borohydride (KBH4) at pH 5.5-6. Labelling efficiency with 99mTc-tropolone yielded 92 +/- 3%, which is higher compared to the 99mTc-HMPAO labelling procedure (64 +/- 13%) using 10(8) of leucocytes. In vitro stability and viability of both the tropolone and the HMPAO labelled cells was investigated. The viability test of the 99mTc-labelled leucocytes was performed in autologous plasma at 37 degrees C and compared with unlabelled leucocytes. After 18 hours of incubation a significant (P < 0.05) higher stability was observed for 99mTc-tropolone labelled leucocytes (84 +/- 5%) compared with that of 99mTc-HMPAO labelled leucocytes (73 +/- 5%). The viability of the 99mTc-labelled leucocytes observed for both labelling procedures was similar to unlabelled leucocytes. In vivo experiments were performed in mice. 99mTc-tropolone or 99mTc-HMPAO labelled murine mixed leucocytes were injected in mice, with a Staphylococcus aureus ATCC 25923 thigh infection. Analysis of scintigraphic images yielded a faster clearance of the 99mTc-tropolone labelled leucocytes. This was most likely due to a significant (P < 0.02) higher liver uptake at 4 hours after administration of the 99mTc-tropolone labelled leucocytes (19%) in comparison with 99mTc-HMPAO labelled cells (9%). Faster and significant (P < 0.02) higher accumulation of the 99mTc-tropolone labelled leucocytes was observed at the site of infection compared with 99mTc-HMPAO labelled leucocytes at all time-intervals after the administration of the 99mTc-labelled leucocytes. The new 99mTc-tropolone leucocyte labelling procedure, offers an attractive low-cost agent for research purposes.

Abscess↗
PubMed1985

The dissociation of some 111In chelates in the presence of transferrin and haemoglobin studied by PAC.

The interaction of [111In]Tris-chelates with protein molecules in aqueous solution at room temperature has been studied using time-integral and time-differential PAC. Increasing amounts of apo-transferrin were added to solutions of [111In]tropolonate, -acetylacetonate, -oxinate and -oxine sulphate, and of haemoglobin to [111In]tropolonate. The transfer of 111In from chelate to protein was monitored by time-integral PAC measurements. Analysis of these data in erms of stability constants showed that with added transferrin complete dissociation of each 111In chelate occurred with increasing protein concentration, the radiolabel being sequestered by the protein molecules. Confirmation of this was provided by time-differential PAC measurements at four tropolone:transferrin relative concentrations, and in the pure systems. A value for the first stability constant of transferrin is presented. Analysis of time-integral PAC data showed that added haemoglobin did not cause complete dissociation of [111In]tropolonate, a [111In]tropolone-haemoglobin complex being formed. Time-differential PAC studies of the [111In]tropolonate:haemoglobin and [111In]haemoglobin systems at 77 K and 295 K supported this conclusion, revealing quadrupole frequencies of 14.0 +/- 0.6 MHz in [111In]haemoglobin and 9.1 +/- 1.1 MHz in the mixed system.

Drug Stability↗
PubMed1979

Toxic interaction between narcotic analgesics and inhibitors of catechol-O-methyltransferase.

A lethal synergism between morphine and tropolone, an inhibitor of catechol-O-methyltransferase, was previously noted in adult male Holtzman rats. The present research demonstrates that this phenomenon generalizes across factors of sex, age, strain (Sprague--Dawley, Wistar) and species (Swiss albino mice). Acute toxicity was also significantly increased (1.5--1.9 times) in the case of codeine, methadone, meperidine and levorphanol, but to a lesser extent than for morphine (4.0 times) in the S-D strain. Another COMT inhibitor, 3,5-dihydroxy-4-methoxybenzoic acid, interacted with morphine in S-D rats to an equal degree as did tropolone. Post-treatment with 1 mg/kg of naloxone in rats or naltrexone in mice reduced the high lethality associated with morphine plus tropolone. There was a pronounced lowering of whole brain norepinephrine (NE) level after morphine plus tropolone in Wistar rats with doses of each component that alone caused no change in NE. Brain dopamine (DA) was elevated by tropolone and by its combination with morphine. Each drug alone caused slight lowering of brain serotonin. Enhancement by tropolone of the toxicity of (+)-amphetamine in mice and rats was of similar magnitude as for morphine. The possible role of brain NE and/or DA in the sensitivity to acute toxic effects of opioids in rodents is suggested by these data, as well as a parallel in this regard with amphetamine-type stimulants.

Aging↗
PubMed1987

Toxicity of indium-111 on the radiolabeled lymphocyte.

The radiolabeling of lymphocytes with 111In has resulted in detectable toxic changes in the cells. The mechanisms of toxicity for lymphocytes have been related to the label's radioactivity and to the chelator used to mediate the intracellular localization. These mechanisms were examined by assessing cellular function with mitogen-mediated blastogenesis after labeling lymphocytes with either the chelator (tropolone) alone, 111In complexed with tropolone, or cadmium (the decay product of 111In) complexed with tropolone. Successful lymphocyte labeling with 111In was shown to be dependent upon the concentration of the chelator (tropolone). Increasing concentrations of tropolone inhibited lymphocyte function to a variable degree. Further reduction in cellular function was detected after incorporation of a constant amount of 111In or 111In's decay product, cadmium. Lymphocyte function was decreased by these two labels in a parallel linear manner. This same toxic effect was seen after labeling with small constant amounts of tropolone and increasing quantities of 111In or cadmium. Thus, although both the required chelator and the radiobiologic exposure have a deleterious effect on the lymphocyte, significant lymphocyte toxicity appears to result from the metal-to-cell interaction as a result of the metal decay product (cadmium).

Cadmium↗