Cerebral blood flow imaging with thallium-201 diethyldithiocarbamate SPECT

Thallium-201 diethyldithiocarbamate ([201TI]DDC) was studied in humans as an agent for cerebral blood flow imaging. Brain uptake proved to be complete 90 sec after injection with no appreciable washout or redistribution for hours. Intracarotid injection suggested an almost 100% extraction during the first passage. Whole-body distribution studies demonstrated a brain uptake of 4.3% of the dose compared with 0.9% for [201TI]chloride. No differences were found in the distribution of [201TI]DDC versus [201TI]chloride in other organs. After the injection of 3 mCi 201TI, good quality single photon emission computed tomographic (SPECT) images of the brain were obtained with both a rotating gamma camera and a multidetector system. In ischemic brain disease, perfusion defects were easily demonstrated. We conclude that [201TI]DDC is a suitable radiopharmaceutical for SPECT studies of cerebral blood flow.

Technetium-99m diethyldithiocarbamate (DDC): comparison with thallium-201 DDC as an agent for brain imaging

Technetium-99m diethyldithiocarbamate (99mTc-DDC) was prepared by reduction of [99mTc]pertechnetate with formamidine sulfinic acid in the presence of DDC at alkaline pH, both from extemporaneous solutions and in a kit formulation. The properties of 99mTc-DDC were compared in vitro and in vivo with those of 201Tl-DDC, an agent used for cerebral perfusion imaging (CPI). 99mTc-DDC is a lipophilic complex but its oil/water partition coefficient is lower than that of 201Tl-DDC. 99mTc-DDC also shows greater binding to plasma proteins. Studies in rabbits show that 99mTc-DDC enters the brain but is not retained to the same extent as 201Tl-DDC. This lack of retention may be because 99mTc-DDC does not decompose rapidly in lipid media as 201Tl-DDC does. These results suggest that 99mTc-DDC in its present formulation is not suitable for CPI with SPECT.

The effect of 5,5'-dithiobis(1-methyltetrazole) on cytoplasmic aldehyde dehydrogenase and its implications for cephalosporin-alcohol reactions

Cephalosporin antibiotics with a 1-methyltetrazole-5-thio side chain have the ability to cause an unpleasant flushing reaction if they are taken some time before the drinking of alcohol. It is proposed that the explanation for this is that the side chain becomes liberated in vivo and oxidized to 5,5'-dithiobis(1-methyltetrazole) or to a mixed disulfide analogue which then inactivates aldehyde dehydrogenase. Support for this proposal is given by the results below concerning the interaction in vitro between the disulfides and sheep liver cytoplasmic aldehyde dehydrogenase. 5,5'-Dithiobis(1-methyltetrazole) has a rapid and pronounced inactivatory effect, very similar in many ways (though not identical) to that of disulfiram, to which it has a structural similarity. (Disulfiram is widely used therapeutically to deter alcoholics from drinking.) 1-Methyl-5-methylthiotetrazole (which is a simple model of the antibiotics) and the free 1-methyltetrazole-5-thiol have no effect on the enzyme in vitro, but methyl 5-(1-methyltetrazolyl) disulfide is a potent inactivator; this also supports the proposed pathway.

Assay for mitolactol and its bifunctional alkylating metabolites in plasma

A method involving precolumn derivatization and high-performance liquid chromatography is described for the measurement of mitolactol levels in plasma. The basis of the assay is the reaction at pH 7.4 and 50 degrees C of mitolactol with diethyldithiocarbamate to form 1,6-bis(diethyldithiocarbamoyl)-2,3,4,5-tetrahydroxyhexane. This derivative is then extracted into chloroform, resolved by normal-phase chromatography, and detected by UV (254 nm) absorbance. The method quantitates the sum of mitolactol and its active bifunctional metabolites, bromoepoxydulcitol and dianhydrogalactitol, in plasma down to concentrations of 0.5 microM. The pharmacokinetic parameters of the drug in mice have been determined following the intraperitoneal injection of either 20 or 100 mg/kg of body weight. Absorption from the peritoneal cavity was largely complete by 5 min. Parameters obtained include a first-order elimination constant, k = 0.92 X 10(-2) min-1 and an apparent volume of distribution, Vd = 0.78 L/kg. For a 100-mg/kg dose, the area under the concentration-time curve was 49 mM X min, and the mean peak drug concentration was reached at 40 min following intraperitoneal injection. Concentrations of mitolactol in total plasma and in plasma ultrafiltrates were identical, indicating that the drug is not (less than 4%) reversibly bound to plasma proteins.

A high-performance liquid chromatographic assay with improved selectivity for cisplatin and active platinum (II) complexes in plasma ultrafiltrate

cis-Diamminedichloroplatinum(II) (DDP) was measured in plasma ultrafiltrate following derivatization with sodium diethyldithiocarbamate (DDTC) by quantitation against a nickel chloride internal standard. A chloroform extract containing the Pt(DDTC)2 and Ni(DDTC)2 complexes was separated by reversed-phase high-performance liquid chromatography on a C18 radial compression column. The complex was eluted with methanol/water, 4/1, at a flow rate of 1.5 ml/min, and was detected at 254 nm. The limit of sensitivity was 0.1 microgram/ml DDP in the ultrafiltrate. This analytical approach was validated by comparison to graphite furnace atomic absorption spectrophotometric determinations of duplicate samples. There was clearly a component of the ultrafiltrable platinum present that was resistant to derivatization by DDTC. Evidence is presented that this component, presumably Pt(II) complexed with endogenous small molecules, is non cytotoxic and, hence, that this method may be selective for "active Pt(II)." This method offers an advantage over atomic absorption determination of total platinum in ultrafiltrate which does not discriminate between active and inactive forms, and over off-line FAA detection of parent DDP in HPLC eluates which ignores other active forms. Using this technique we have measured the pharmacokinetics of DDTC-reactive Pt(II) in humans after either i.v. infusion or infusion of DDP into the peritoneal cavity of patients with ovarian carcinoma.

High-performance liquid chromatographic determination of platinum (II) in plasma ultrafiltrate and urine: comparison with a flameless atomic absorption spectrometric method

A technically simple, rapid and sensitive high performance liquid chromatographic assay for cis-dichlorodiammineplatinum (II) in human plasma ultrafiltrate and urine is described. The drug was chelated by exchange with diethyldithiocarbamate and extracted into chloroform. Nickel (II) was used as an internal standard which allows correction for the matrix effects observed with previous chromatographic and spectrometric methods. Chromatography was performed on a mu-Bondapak CN column and the eluent measured spectrophotometrically at 254 nm. Precision and reproducibility were both excellent and the detection limit was less than 50 ng/ml using only 1 ml of biological fluid.

[Quantitative determination of toxic elements in microbiologically produced technical protein feeds. 3. Photometric determination of trace amounts of arsenic using silver diethyldithiocarbamate and the atomic absorption spectrometry-hydride technic]

With a view to the determination of trace amounts of arsenic in microbiologically produced protein feeds, the authors compared the results yielded by the photometric method using silver diethyl dithiocarbamate ( AgDDTC ) with those obtained by means of the atomic absorption spectrometry(AAS)-hydride technique. Prior to analysis, the samples were dry-ashed after addition of Mg/Mg(NO3)2 or digested with nitric acid. Further comparative results were obtained by neutron-activation analysis. These methods were used to analyze novel protein feeds produced from yeast and bacterial biomasses, as well as some fermentation raw materials, for arsenic. A comparison of the values found with literature data relative to the arsenic contents of conventional protein feeds and foods shows that the novel microbiologically produced protein feeds are absolutely able to compete with protein feeds and foods currently used.

201Tl-diethyldithiocarbamate: a possible radiopharmaceutical for brain imaging

For estimating regional brain perfusion with a gamma camera lipophilic radiopharmaceuticals are required. This paper describes the development of 201Tl-diethyldithiocarbamate (201TlDDC). First the compound NaDDC was tested for stability and an assay was developed. Next the 201TlDDC complex was prepared and checked for lipophilicity and stability by paper chromatography. A scintigraphic pilot study using this agent in a rabbit showed considerable brain uptake, compared to 201TlCl. Finally we performed a study in rats on the distribution of 201TlDDC in different organs. The results confirmed the lipophilicity of the agent. Within the first hour the percentage of injected dose per gram tissue was 2.73% in the cerebrum and 1.35% in the cerebellum. These data are in good agreement with some other agents used for assessment of brain blood flow.

Phosphine analysis in post mortem specimens following ingestion of aluminium phosphide

Phosphine was detected in post mortem stomach and contents, blood, and liver specimens of a man who had ingested tablets containing aluminium phosphide. The phosphine was released from the samples after acid treatment and analysed by means of a headspace gas chromatographic technique using a nitrogen phosphorus detector.

Colorimetric determination of agarose-immobilized proteins by formation of copper-protein complexes

A simple, reliable, and sensitive colorimetric procedure for the determination of proteins bound to agarose is described. The procedure utilizes the capacity of diethyldithiocarbamate to react with cupric ions resulting in a complex of dark yellow color. The extent of reduction in the color, due to chelation of Cu2+ by the immobilized proteins, indicates the amount of protein. The optimum conditions for the determination of immobilized proteins are investigated. The formation of Cu2+-protein complex proceeds stepwise until enough excess of Cu2+ is present to form the final complex. The reliability of the procedure requires that all the protein species, samples and standards, are in the final Cu2+-protein complex form. A comparative study on the determination of different proteins bound to agarose using this method as well as other methods, such as protein balance, modified Lowry reaction, and direct ultraviolet spectrophotometry, is described. The method is substantially more reliable, accurate, and simple than previously described methods.

The influence of reducing agents on the composition of 99Tc-complexes: implications for 99mTc-radiopharmaceutical preparation

The use of formamidine sulphinic acid as a reducing agent in the presence of technetium-99-pertechnetate and diethyldithiocarbamate ligand has been shown to yield a complex containing a Tc = CO bond. The carbon monoxide present in this complex originates from the reducing agent itself. Evidence is presented which suggests that this carbonyl complex is present in the 99mTc-diethyldithiocarbamate preparation obtained by the use of formamidine sulphinic acid as the reducing agent. Use of hydrazine as a reducing agent yields a complex containing a Tc = N bond. It is apparent that when reducing agents such as hydrazine or formamidine sulphinic acid are used in the preparation of 99mTc-radiopharmaceuticals, the possibility of the formation of complexes structurally different to those obtained by the use of stannous chloride must be considered.

Urine analysis of platinum species derived from cis-dichlorodiammineplatinum(II) by high-performance liquid chromatography following derivatization with sodium diethyldithiocarbamate

A clinically useful method is described for the quantitative analysis of platinum species derived from cis-dichlorodiammineplatinum(II) in urine. The drug and its biodegradation products are derivatized directly in urine by reaction with sodium diethyldithiocarbamate (DDTC) to form a common product, a 2:1 DDTC-platinum adduct. This complex is stable and can be quantitatively extracted into 0.1 volumes of chloroform. An aliquot of the chloroform layer is then subjected to high-performance liquid chromatography on a muBondapak CN column and the eluent monitored spectrophotometrically at 254 nm. At this wavelength the DDTC-platinum adduct has a molar absorptivity of 43,000, and platinum levels of 25 ng/ml or urine can be detected with a precision of +/- 2.5% and an accuracy of +/- 4%.

The determination of nonesterified fatty acids in blood serum using a stable cupric reagent

A modification of the method for the determination of nonesterified fatty acids in blood serum using a stable cupric reagent stabilized with sodium citrate, has been developed. 33 g of NaCl are dissolved in 100 ml of the described reagent, and its pH should not be additionally adjusted. The reagent is stable for at least one year if kept in the refrigerator at 5 degrees C. The determination may be done in 0.1--0.2 ml of blood serum. The relationship between the absorbance and concentration of palmitic acid is still linear at a concentration of 2500 mumol/l. Error of the method is +/- 3%.

High-performance liquid chromatographic analysis of dianhydrogalactitol in plasma by derivatization with sodium diethyldithiocarbamate

A high-performance liquid chromatographic method is described for measuring submicrogram quantities of dianhydrogalactitol, a promising anti-neoplastic agent, in plasma. The drug is derivatized directly in plasma with sodium diethyldithiocarbamate to form a bis(dithiocarbamoyl) ester which absorbs UV light at 254 nm (am 17,000). The derivatized product is then extracted quantitatively into chloroform and separated by normal phase chromatography (muBondpak CN column). Dianhydrogalactitol concentration below 50 ng/ml of plasma can be detected in the eluent.

Chelate extraction and flame atomic absorption spectrometric determination of nanogram amounts of manganese in blood and animal tissue

A method for the determination of manganese in blood and animal tissue has been developed involving wet digestion of the sample by perchloric and nitric acids, complexing with sodium diethyldithiocarbamate, and extracting with methyl isobutyl ketone at pH 6.7. The methyl isobutyl ketone is removed, and the residue is dissolved in 0.05N HCl in acetone-water (9 + 1) and is aspirated into an air-acetylene flame of an atomic absorption spectrometer. The limit of detectability is about 10 ng Mn/ml in the solution aspirated or 2 ng Mn/ml in bovine blood for a 20 ml sample.

Superoxide anion as a mediator of drug-induced oxidative hemolysis

The superoxide dismutase inhibitor diethyldithiocarbamate (DDC) was utilized to study the toxic effect of 1,4-naphthoquinone 2-sulfonate (NQ), a structural analog of the hemolytic drug, menadione, on red cells. NQ was shown to react with hemoglobin and result in the generation of superoxide anion (O2-). Red cells treated with NQ were found to undergo a gradual disappearance of their oxyhemoglobin and also hemolyze. Red cells pretreated with DDC to inhibit cellular superoxide dismutase were found to be markedly sensitive to oxyhemoglobin destruction and hemolysis in the presence of NQ. Superoxide dismutase-inhibited red cells were also found to undergo a slow autohemolysis in the absence of NQ. No evidence for lipid peroxidation was obtained for red cells treated with NQ either in the presence or the absence of DDC. Ghosts prepared from superoxide dismutase-inhibited red cells exposed to NQ were found to retain a green hemoglobin-derived pigment.