The effect of entacapone (OR-611) on brain [18F]-6-L-fluorodopa metabolism: implications for levodopa therapy of Parkinson's disease

We used PET and [18F]-6-L-fluorodopa ([18F]dopa) to measure the effect of a peripheral COMT inhibitor, entacapone, on the extracerebral metabolism and subsequent striatal uptake of [18F]dopa. Four parkinsonian patients and six age-matched normal controls were each scanned twice, once after carbidopa (150 mg) plus placebo and once after carbidopa (150 mg) plus entacapone (400 mg or 800 mg). Without entacapone premedication, by 90 minutes from injection, only 22% of the [18F] signal in plasma represented unmetabolized [18F]dopa (the balance being 3-O-methyl[18F]dopa). After entacapone medication, this fraction increased to 56% of the [18F] signal (p < 0.0001). We did not find any significant differences between the changes observed in patients versus controls or between those subjects who received 400 mg entacapone versus 800 mg in either this or any of the other reported measures. PET image contrast increased in all cases, reflecting an increase in the specific striatal signal ([striatum-occipital]:occipital ratio increased 38% [p < 0.0001]). Entacapone did not alter the rate of striatal uptake and decarboxylation of [18F]dopa as estimated using a graphic approach with metabolite-corrected plasma as input function to calculate the influx constant, Ki(p) (p = NS). This confirms that such an analytic approach adequately corrects for the effect of extracerebral [18F]dopa methylation. In contrast, the influx constant Ki(o) (calculated using occipital counts as the input function) increased 45% after entacapone (p < 0.0001). This demonstrates the sensitivity of this analytic approach to the presence of peripheral 3-O-methyl[18F]dopa and provides an estimate of the percentage increase in brain free [18F]dopa resulting from entacapone premedication.

Quantitation of [11C]diprenorphine cerebral kinetics in man acquired by PET using presaturation, pulse-chase and tracer-only protocols

The quantitation of regional cerebral in vivo opioid receptor rate constants using [11C]diprenorphine and positron emission tomography (PET) using 3 types of protocol (presaturation, pulse-chase naloxone displacement and tracer-only protocols) together with measurements of regional cerebral blood flow is described in normal volunteers. Arterial blood was sampled continuously for radioactivity and was corrected for metabolites and plasma/blood partition of radioactivity to provide a continuous plasma input function. A compartmental model involving 3 tissue compartments was used to describe the regional cerebral pharmacokinetics of the tracer. The compartments comprised: (1) free plus rapidly exchanging non-specifically bound ligand, (2) specifically bound, naloxone displaceable ligand, and (3) a kinetically distinguishable non-specifically bound pool. Regional estimates of fractional rate constants relating to specific binding were obtained using naloxone in a pulse-chase design of tracer displacement. Less precise estimates of these rate constraints were obtained from single-tracer-only studies, but when binding was expressed as the tissue total volume of distribution relative to plasma there was good correlation with regional values obtained from pulse-chase studies performed in the same individuals. The application of these protocols to the measurement of indices of regional-specific opioid receptor binding in the human brain is discussed.

Optimization of a time-resolved immunofluorometric assay for tumor-associated trypsin inhibitor (TATI) using the streptavidin-biotin system

We have developed two 'sandwich'-type time-resolved immunofluorometric assays (IFMA) for tumor-associated trypsin inhibitor (TATI) using monoclonal and polyclonal antibodies. In the standard assay the monoclonal antibody was immobilized onto the walls of polystyrene microstrip wells and the polyclonal reagent was labeled with a europium chelate. We tested various assay conditions in order to optimize the assay for sensitivity and measuring range. Purification of the labeled antibody by hydrophobic interaction chromatography was found to be the most important single factor affecting sensitivity. Assay sensitivity and range were also improved by acid treatment of the solid phase antibody. To improve the sensitivity further the streptavidin/biotin (SAB) system was incorporated into the IFMA technique. In this simple and fast streptavidin/biotin IFMA (SAB-IFMA) we used streptavidin-coated wells to which we added biotinylated monoclonal antibody and a serum or urine sample. After incubation for 1.5 h and washing, the polyclonal europium-labeled tracer antibody was added. After incubation for 1 h the wells were washed and the Eu fluorescence measured. The assay performance of the SAB-IFMA was compared to the standard IFMA and radioimmunoassay (RIA). The detection limit was 0.05 microgram/l and the analytical range 3000-fold. The mean analytical recovery was 101%. Other advantages of the SAB-IFMA were high sensitivity and the low amounts of monoclonal antibody required, only 1/50 of that used in the standard IFMA.

Radioligands for PET studies of central benzodiazepine receptors and PK (peripheral benzodiazepine) binding sites--current status

The status of the radiochemical development and biological evaluation of radioligands for PET studies of central benzodiazepine (BZ) receptors and the so-called peripheral benzodiazepine binding sites, here discriminated and referred to as PK binding sites, is reviewed against current pharmacological knowledge, indicating those agents with present value and those with future potential. Practical recommendations are given for the preparation of two useful radioligands for PET studies, [N-methyl-11C]flumazenil for central BZ receptors, and [N-methyl-11C]PK 11195 for PK binding sites. Quality assurance and plasma metabolite analysis are also reviewed for these radioligands and practical recommendations are given on methodology for their performance.

Dose dependent occupancy of central dopamine D2 receptors by the novel neuroleptic CP-88,059-01: a study using positron emission tomography and 11C-raclopride

Positron emission tomography (PET) and 11C-raclopride were used to measure the occupancy of central dopamine D2 receptors by a new neuroleptic, CP-88,059-1. In a double blind dose escalation study, seven healthy male subjects received a predose of between 2 mg and 60 mg CP-88,059-1, 5 h before PET scanning. One additional subject was assigned to placebo predose. Receptor occupancy was defined as the percentage reduction in binding potential compared with that seen in the subject predosed with placebo and with that seen in seven unmedicated normal volunteers previously studied. Binding of 11C-raclopride decreased in a dose dependent manner, and 85% dopamine D2 receptor occupancy was achieved with the highest dose of CP-88,059-1. The findings confirm that brain dopamine D2 receptors are blocked by CP-88,059-1 and suggest that an effective antipsychotic dose will be between 20 mg and 40 mg. The study high-lights the potential of positron emission tomography in the preclinical evaluation of new drugs.

The use of 2-[18F]fluoro-2-deoxy-D-glucose as a potential in vitro agent for labelling human granulocytes for clinical studies by positron emission tomography

In this study, 2-[18F]fluoro-2-deoxy-D-glucose, [( 18F]FDG) was used to radiolabel human granulocytes in vitro for possible clinical use by positron emission tomography (PET). Uptake of [18F]FDG was dependent on the amount of glucose in the labelling medium, e.g. when 1 x 10(7) granulocytes were incubated with [18F]FDG containing 15 micrograms/mL glucose 80% of [18F]FDG was incorporated within 30 min, but in the presence of 1 mg/mL of glucose it was reduced to 2%. Increasing the cell concentration and activating the granulocytes with Streptococcus pneumoniae, opsonized zymosan or phorbol myristate acetate all increased the uptake of [18F]FDG. Retention of the [18F]FDG by the cells as [18F]FDG-6-phosphate was also dependent on the extracellular glucose concentration, 9% was released within 60 min in the absence of glucose, but 27% in the presence of 1 mg/mL glucose.

Imaging of metastatic colorectal cancer with tumour-activated killer lymphocytes

Adoptive immunotherapy may be useful for treating or visualising metastatic cancer. Lymphocytes were taken from 6 patients with metastatic colorectal cancer and cultured with cells from the patients primary tumour to produce tumour-activated killer (TAK) lymphocytes. We re-injected each patient with IIIIn-labelled TAK cells in order to visualise metastases. Images were taken with a gamma-camera for up to 48 h after injection. Metastases were revealed as early as 4 h in the lung and as late as 48 h in the abdomen. Liver images produced "cold" spots corresponding to metastatic lesions. Lymph nodes were not visualised. Re-injection of TAK cells raised against autologous colorectal tumours reveals the sites of metastases.

Tumor-associated trypsin participates in cancer cell-mediated degradation of extracellular matrix

We have recently demonstrated that many cancer cell lines produce a novel trypsinogen isoenzyme called tumor-associated trypsinogen 2 (TAT-2). It was found during a search of the target protease for tumor-associated trypsin inhibitor (TATI). We now show that degradation of subendothelial cell extracellular matrix (ECM) by four different cell lines (COLO 205 colon carcinoma, K-562 erythroleukemia, CAPAN-1 pancreatic carcinoma, and HT 1080 fibrosarcoma) can be partially inhibited by TATI or neutralizing trypsin antibodies. When cells were cultured in serum-free medium on ECM, TATI and trypsin antibodies inhibited the release of immunoreactive fibronectin fragments from ECM by 47-54 and 40%, respectively. Degradation of isotopically labeled ([3H]serine, [3H]proline, and [35S]sulfate) ECM was also significantly prevented by TATI. At its maximum, it exerted a 57% inhibition on the degradation of [3H]serine-labeled ECM. Plasminogen added exogenously to the culture medium further potentiated the proteolysis of ECM. Interestingly, addition of enteropeptidase, an activator of TAT-2, also enhanced cell-mediated proteolysis as assessed by degradation of purified fibronectin coated onto the surface of wells. Immunoblot analysis showed that enteropeptidase-mediated proteolysis generated a pattern of fibronectin fragments similar to that obtained by digestion of purified fibronectin by TAT-2. These results demonstrate the existence of a proteolytic system in tumor cells which is dependent on the activation of TAT-2. We suggest that TAT-2 is involved in a protease cascade-stimulating tumor cell invasion and degradation of extracellular matrix.

Human colon carcinoma, fibrosarcoma and leukemia cell lines produce tumor-associated trypsinogen

Previous studies have indicated that cyst fluid of ovarian tumors contains 2 trypsinogen isoenzymes, called tumor-associated trypsinogen-I (TAT-I) and trypsinogen-2 (TAT-2), the levels of which correlate with the degree of malignancy of the tumors. In addition, these cyst fluids contain large amounts of tumor-associated trypsin inhibitor (TATI), which is also expressed in many other human tumors. In the present study we examined the production of TAT-I, TAT-2 and TATI in 9 established tumor-cell lines. TAT-2 was produced by 5 cell lines. Its concentration in the conditioned medium of COLO 205 colon adenocarcinoma cells, K-562 erythroleukemia cells and fibrosarcoma cell lines HT 1080, 8387 and A 9733 was 460 micrograms/l, 9.8 micrograms/l, 21 micrograms/l, 8.8 micrograms/l and 0.24 micrograms/l, respectively. TAT-I was detectable in the conditioned medium of COLO 205 and HT 1080 cells at concentrations of 64 micrograms/l and 0.5 micrograms/l, respectively. TATI was detected only in the media of COLO 205 cells at a concentration of 23 micrograms/l. TAT-2 zymogen was purified from the conditioned medium of COLO 205 and HT 1080 cells by immunoaffinity chromatography. According to its aminoterminal amino acid sequence, a molecular mass of 28 kDa by SDS-PAGE, elution pattern in ion-exchange chromatography and ability to be activated by enteropeptidase, the zymogen is identical to that previously isolated from cyst fluid of ovarian tumors. In addition, we found that TAT-2 secretion could be down-regulated by dexamethasone in HT 1080 cells but not in COLO 205 cells. The abundant production of TAT-2 isoenzyme in different cancer cell lines suggests that it could contribute to the increased proteolytic activity of many human tumors.

Labelling autologous platelets with 111In tropolonate for platelet kinetic studies: limitations imposed by thrombocytopenia

An in vitro method of radiolabelling platelets with 111In tropolonate in plasma has been devised enabling imaging and cell kinetic studies to be performed in patients with thrombocytopenia (TP) using autologous, rather than donor, platelets. Platelets from 10 TP patients, with platelet counts ranging from 4-91 x 10(9)/l, were labelled in 50% plasma with 111In tropolonate, containing the optimum tropolone concentration of 2 x 10(-4) mol/l, at platelet concentrations ranging from 0.08-4.5 x 10(9)/ml resulting in labelling efficiencies (LE) between 51 and 86%. In 4 patients, red cells contaminated the platelets but this was corrected for by measuring the proportion of 111In on the platelets prior to injection and in the post-injection blood samples. Platelet recovery (PR), mean platelet life-span (MPLS) and platelet production rate (PPR) were calculated and splenic and hepatic images were taken. The results clearly show that useful clinical data can be obtained by this method even in patients with severe TP.

Osteomyelitis

The use of 111In-labelled granulocyte scintigraphy is recognized as a reliable method for detecting osteomyelitis and has similar sensitivity and significantly increased specificity compared to bone scintigraphy and 67Ga studies. Recent published work using pure granulocytes labelled with 111In tropolonate to detect osteomyelitis resulted in sensitivity of 100% and specificity of 92%. 99Tcm as an alternative granulocyte label offers advantages of convenience, lower radiation dose and higher image resolution. We have scanned 20 patients with suspected osteomyelitis using autologous granulocytes labelled with 99Tcm hexamethylpropyleneamineoxime (HMPAO), 12 of whom had prosthetic joints. The scan results were correlated with clinical, radiographic, microbiological and histological findings. Sensitivity was 100% and specificity was 93% which compares favourably with results obtained using 111In-labelled granulocytes. We believe that labelled granulocyte scintigraphy is a useful investigation in the diagnosis of osteomyelitis and that 99Tcm HMPAO appears to be at least as useful as 111In as the labelling agent.

99Tcm-HMPAO labelled leucocytes: comparison with 111In-tropolonate labelled granulocytes

The lipophilic complex, 99Tcm-hexamethylpropyleneamine oxime (HMPAO) is an efficient leucocyte label, and labels granulocytes with more stability than mononuclear leucocytes. The recovery of 99Tcm-HMPAO granulocytes, expressed as the percentage of injected granulocyte-associated activity circulating as granulocyte-associated activity 40-45 min after injection, was 37% (S.E. 3%), similar to the recovery of 111In-labelled granulocytes isolated and labelled in plasma using tropolone. The T1/2 of 99Tcm-HMPAO labelled granulocytes in blood was 4.4 h (S.E. 0.4 h), less than that of 111In-labelled granulocytes, although when a correction was made for 99Tcm elution, it was 6.4 h. The initial biodistribution of 99Tcm-labelled leucocytes was similar to 111In-labelled granulocytes, with a rapid initial lung transit, prominent splenic activity, bone marrow activity and minimal hepatic activity, although, unlike 111In, 99Tcm activity was also seen in urine, occasionally in the gallbladder, and, from about 4 h, consistently in the colon. Bone marrow activity was particularly prominent with 99Tcm. About 6% of 99Tcm was excreted in the faeces up to 48 h after injection, and about 17% in urine up to 24 h. The time-activity curves of reticuloendothelial activity up to 24 h were broadly similar for the two labelled cell preparations, and the differences that were observed can be explained on the basis of a higher rate of 99Tcm elution. Clinical information given by the two agents was similar in 27 of 30 patients who received both. Of the three who gave different information, one received 111In-labelled granulocytes which were considered to be functionally suboptimal and two, with inflammatory bowel disease, showed different distributions of abnormal bowel activity. We conclude that with respect to granulocyte kinetics and clinical data, 99Tcm-HMPAO labelled leucocytes are comparable with 111In-tropolonate labelled granulocytes.

The development of a clinical protocol for the radiolabelling of mixed leucocytes with 99Tcm-hexamethylpropyleneamine oxime

To devise a protocol for the radiolabelling of mixed leucocytes with 99Tcm-hexamethylpropyleneamine oxime (99Tcm-HMPAO), the effect of HMPAO concentration, cell concentration, plasma concentration and anticoagulant on the uptake of the lipophilic complex was measured, together with the stability of the 99Tcm on the labelled cells. It was found that cell uptake was rapid, independent of HMPAO concentration over the range 20-80 micrograms ml-1, but dependent on cell and plasma concentration. Incubation of mixed leucocytes from 85 ml blood with 1 ml ACD-plasma and 4 ml 99Tcm-HMPAO containing 400 MBq 99Tcm for 10 min at room temperature gave optimum results and was used in 90 patients. The mean labelling efficiency, which was the amount of added 99Tcm incorporated by the cells, was 55% (+/- 13 S.D.), of which 77% were incorporated by the granulocytes, 17% by the mononuclear cells and 6% by the platelets and erythrocytes. During a 1 h incubation in plasma 9% (+/- 4% S.D.) of the 99Tcm were released from the labelled mixed leucocytes. This occurred predominantly from the mononuclear cells.

Investigations to determine the optimum conditions for radiolabelling human platelets with 99Tcm-hexamethyl propylene amine oxime (99Tcm-HM-PAO)

99Tcm-hexamethyl propylene amine oxime (99Tcm-HM-PAO) has been evaluated as an agent to radiolabel human platelets in vitro. The rate of uptake of this lipophilic complex, the effect of HM-PAO, plasma and platelet concentration were measured to determine the optimum conditions for radiolabelling platelets for short-term clinical investigations of thromboses. The complex was made according to the manufacturer's instructions and immediately added to isolated platelets in vitro. The rate of labelling was slower than for leucocytes, reaching a plateau after approximately 40 min at room temperature (RT). Increasing the temperature to 37 degrees C did not increase the labelling efficiency (LE). Addition of plasma to platelets at a cell concentration of 1 x 10(9) [corrected] ml-1 reduced the LE from 66% in saline to 52% in 20% ACD-plasma. However, increasing the platelet concentration from 5 x 10(8) to 2 x 10(9) ml-1, increased the LE from 9 to 76% for platelets labelled in 20% plasma for 30 min at RT. The in vitro stability of the 99Tcm in the labelled cells showed that 7% of the radioactivity were immediately released from the platelets and a further 13% were eluted during a 60 min incubation in plasma at 37 degrees C. It has been concluded that incubation of platelets at RT with 99Tcm-HM-PAO containing 80 micrograms ml-1 HM-PAO at a cell concentration of 1 x 10(9) ml-1 or greater, results in a high LE, with more than 85% of the 99Tcm being retained by the platelets during a 60 min incubation in plasma.

Inflammation: imaging with Tc-99m HMPAO-labeled leukocytes

Leukocytes labeled with technetium-99m hexamethylpropyleneamine oxime (HMPAO) were used in 100 patients: 32 with suspected inflammatory bowel disease, 17 with fever of unknown origin, 21 with suspected abdominal sepsis, 20 with suspected bone sepsis, seven with bronchiectasis, and three with recent myocardial infarction. The distribution of activity in patients subsequently shown not to have inflammatory bowel disease was similar to that previously described for indium-111-labeled leukocytes. However, in this study, activity was also seen in the kidneys and bladder and occasionally the gallbladder on both early (1-3 hours) and late (24 hours) views, and in the colon in late views. Migration of Tc-99m-labeled granulocytes was seen in inflammatory disease as early as 30 minutes after injection, while normal bowel activity was not seen before 4 hours. The sensitivity of Tc99m-labeled leukocytes in the detection of inflammation was 100%, the specificity was 95%.

Optimum conditions for radiolabelling human granulocytes and mixed leucocytes with 111In-tropolonate

To determine the optimum conditions for the in vitro radiolabelling of human granulocytes with 111In-tropolonate for clinical studies, the factors which affected the amount of 111In bound to the cells, the labelling efficiency (LE), were measured. These included the tropolone concentration, labelling medium and cell concentration. The tropolone concentration was dependent on the amount of plasma in the labelling medium; with 90% ACD plasma it was 4 x 10(-4) M and with Hepes saline buffer it was 4 x 10(-5) M. Using these tropolone concentrations and a low granulocyte concentration of 1 x 10(7) ml-1, the LE in 90% ACD plasma was 29% and in buffer was 74%. However, increasing the cell concentration to 1 x 10(8) ml-1 gave a LE of 90% in buffer and plasma. The optimum conditions for clinical studies involved incubating granulocytes, or mixed leucocytes as a source of granulocytes, at a cell concentration of at least 5 x 10(7) cell/ml in 1 ml ACD plasma, pH 7-7.6 with 0.1 ml tropolone at 4.4 x 10(-3) M mixed with no more than 100 microliter 111InCl3 for 15 min at room temperature. Under these conditions more than 96% of the 111In was taken up by the granulocytes and only 3% of the 111In was released from the labelled cells during a 30 min incubation in plasma. 111In-tropolonate is therefore an efficient agent for stably radiolabelling human granulocytes in plasma for clinical studies.

Syphilis in women of reproductive age in Mogadishu, Somalia: serological survey

In Mogadishu, Somalia 223 women of childbearing age, including prostitutes, were tested for serum markers for syphilis by the Venereal Disease Research Laboratory (VDRL) test and the Treponema pallidum haemagglutination assay (TPHA). Sera reactive in either of these tests were tested for IgM antibodies by solid phase haemadsorption assay (SPHA). Three per cent of sera from 67 pregnant women and none of those from 71 educated women gave positive results that were confirmed with the TPHA. In contrast, 58% of sera from 85 prostitutes were confirmed as being positive, 26% of which were SPHA positive, which indicated active syphilis. The proportion of TPHA positive sera increased with age among the prostitutes. As venereal syphilis is highly prevalent in prostitutes in Mogadishu, a strategy of intervention based on screening followed by treatment seems to be indispensable.

Sexually transmitted viral infections in various population groups in Mogadishu, Somalia

The prevalence of serum antibodies to human immunodeficiency virus (HIV), herpes simplex virus (HSV), and cytomegalovirus (CMV) and of hepatitis B virus (HBV) markers was investigated in different population groups, including prostitutes, in Mogadishu, Somalia. Hepatitis B surface antigen (HBsAg) was detected in 37% of pregnant women, 4% of neonates, 22% of educated women, and 20% of prostitutes. No significant difference between the groups was observed for HBV. In contrast to figures reported from South East Asia, the prevalence of hepatitis Be antigen (HBeAg) was 18% in prostitutes and only 3% in all other HBsAg positive subjects. The prevalence of antibodies to HSV (100%) and CMV (90%) was very high, but antibodies against HIV were not detected in any of 471 sera. As the routes of transmission for HBV and HIV infections are considered to be similar, HIV will probably spread rapidly in Somalia once this virus has been introduced into the country.

A simple in vitro method of radiolabelling human erythrocytes in whole blood with 113mIn-tropolonate

A simple and rapid in vitro procedure has been developed for selectively radiolabelling erythrocytes in whole blood using 113mIn-tropolonate. A maximum labelling efficiency of 97% was achieved, of which 95.5% was on the erythrocytes after only 5 min incubation of whole blood at room temperature. The optimum amount of tropolone for labelling whole blood was 10 micrograms of tropolone per ml of blood using acid-citrate dextrose (ACD) as the anticoagulant and 50 micrograms of tropolone per ml of blood using heparin. Under these optimum conditions, only 2.5% of the cell-bound 113mIn was released from the labelled cells during a 1 h in vitro incubation in cell-free plasma, irrespective of the anticoagulant used. These results suggest that 113mIn-tropolonate may prove to be a useful in vitro agent for labelling erythrocytes for short-term clinical investigations, especially at centres where 99mTc and 111In are unavailable.

Clinical experience with 99mTc-hexamethylpropylene-amineoxime for labelling leucocytes and imaging inflammation

Hexamethylpropylene-amineoxime (HMPAO) forms a lipid-soluble neutral complex with 99mTc which is rapidly incorporated into leucocytes in vitro. In six patients with suspected or known inflammatory disease, a "mixed" leucocyte suspension isolated from 85 ml blood anticoagulated with acid-citrate-dextrose was labelled by 99mTc-HMPAO with a mean efficiency of 47% (SE2%), of which 78% (3) was taken up by granulocytes. Activity eluted more rapidly from other cell types in vitro than from granulocytes, which remained firmly labelled. Mean initial biodistribution of the label and granulocyte recovery in blood of 32% (8) at 30-40 min showed that the granulocytes were not significantly activated during labelling. All six patients were positive for inflammatory disease, as early as 30 min in five patients and at 3 h in the sixth; they all remained positive at 20-24 h. Four patients also received 111In-labelled "pure" granulocytes. In terms of detail, the 99mTc images were comparable or superior to the 111In images.

The importance of radiolabelling human granulocytes with 111In-tropolonate or 111In-2-mercaptopyridine-N-oxide in plasma containing acid-citrate-dextrose

When blood cells are radiolabelled in plasma, for example with 111In-tropolonate, the plasma always contains an anticoagulant, usually acid-citrate-dextrose (ACD) or heparin. The effect of ACD and heparin on the labelling efficiency (LE) and optimum concentration of ligand required to radiolabel human granulocytes in plasma with 111In-tropolonate or 111In-2-mercaptopyridine-N-oxide (111In-merc) has been measured. The concentrations of ligand (tropolone or merc) required for maximum cell labelling in plasma containing ACD were 4 X 10(-4) M tropolone and 1 X 10(-4) M merc, whereas using plasma containing heparin, the optimum concentrations were 10-fold higher, at 4 X 10(-3) M and 1 X 10(-3) M respectively. At the optimum ligand concentrations, the LE for 1 X 10(8) granulocytes labelled in plasma containing ACD was 90% using 111In-tropolonate and 82% using 111In-merc, whereas using plasma containing heparin they were 68% and only 20%, respectively. Addition of ACD to heparinised plasma abolished the necessity for more ligand and increased the LE to the same values as those for plasma containing ACD alone. These results clearly demonstrate that to obtain a high LE using the lowest possible concentrations of tropolone or merc, the granulocytes must be labelled in plasma containing ACD.

Technetium-99m autologous phagocyte scanning: a new imaging technique for inflammatory bowel disease

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Erythrocyte radiolabelling: in vitro comparison of chromium, technetium, and indium in undamaged and heat damaged cells

The stability of the commonly used red cell radio labels chromium-51, indium-(111 or 113m), and technetium-99m, within intact red cells and stroma and their distribution within the cell were compared in undamaged and heat damaged red cells in relation to the clinical use of heat damaged cells in the assessment of splenic function. Chromium-51 labelled haemoglobin both in undamaged and heat damaged cells; indium predominantly labelled haemoglobin in undamaged cells but labelled stroma in heat damaged cells, even when the cells were labelled before heating; technetium-99m predominantly labelled haemoglobin in undamaged cells but only labelled stroma in heat damaged cells if these were heated before labelling. Indium was more firmly bound by stroma prepared from heat damaged cells, and technetium-99m showed a high rate of elution both from cells and stroma, although this rate was lower for heat damaged cells.

PAC studies of 111In binding to transferrin, tropolone and acetylacetone in aqueous solutions

Time integral and time-differential PAC measurements have been made over a wide temperature range in aqueous solutions of [111In]tropolonate and [111In]acetylacetonate. The quadrupole frequency in the latter is approximately 30% higher than that in the former and the molecular volumes derived from rotational correlation times show the expected differences. Apo-transferrin was separately added to the two 111In-chelates and the transfer of activity from chelate to transferrin followed as a function of relative molar concentrations. Very much larger molar ratios of transferrin to tropolone than of transferrin to acetylacetone were required before substantial transfer of 111In from chelate to transferrin took place. This difference in affinity for transferrin could be one significant factor in explaining the enhanced ability of [111In]tropolonate to label blood cells in the presence of plasma. The determination of PAC parameters in [111In]transferrin over a range of temperatures showed that the values of quadrupole frequency obtained depended on the number of binding sites assumed. For only one 111In site per molecule, the quadrupole frequency increases by over 50% as the temperature is reduced below the freezing point of the solution. If two 111In sites are assumed there appears to be a change in the percentage occupancy of the two sites on either side of the transition.

Lung transit of 111Indium-labelled granulocytes. Relationship to labelling techniques

The early in vivo distribution of 111Indium-labelled granulocytes, recorded by dynamic imaging using a gamma camara and computer, varied according to the separation and labelling technique. Following i.v. bolus injection, 4 kinetic patterns could be identified: (A) rapid transit through the pulmonary vasculature, (B) delayed transit through the lung with clearance by about 30 min, (C) complete retention by the lung, for up to 10 min, followed by slow release over a period of 1 to 2 h, (D) delayed transit through the lung with a similar time course to (B) but with subsequent heavy liver uptake. Granulocytes labelled with 111In-tropolonate and maintained in plasma throughout the labelling procedure, whether injected as a 'pure' (separated by plasma-enriched density gradient centrifugation) or 'crude' (separated by differential centrifugation) preparation, displayed type A kinetics, thought to most closely represent the normal behaviour of granulocytes. 'Crude' cells labelled in saline with 111In-acetylacetonate displayed type B kinetics. 'Pure' cells isolated on Percoll-saline and labelled in saline with 111In-acetylacetonate displayed type C kinetics, thought to represent granulocyte 'stimulation' and/or damage, or type D kinetics, thought to represent severe damage. The importance is stressed of labelling granulocytes for kinetic studies with a technique that results in minimal alteration of cell behaviour.

Imaging of inflammation with indium-111 tropolonate labeled leukocytes

Indium-111 tropolonate has recently been introduced as a new cell-labeling agent. It has the interesting property of labeling cells in plasma with high efficiency, and may therefore promote an improvement in viability of labeled cells. This paper describes our initial experience with In-111 tropolonate as a leukocyte label for abscess imaging. Pure populations of separated granulocytes, as well as crude leukocyte preparations, have been labeled. Of 101 studies performed, 51 were positive (no false positives) and 50 negatives, of which only two were false negatives. Localization in sites of inflammation was prominent and rapid. Of 36 positive studies, 27 were already positive at 40 min following injection and an additional nine at 3 hr. Of the other 15 positive studies, 11 were scanned for the first time at 3 hr, when they were positive. Granulocytes labeled with this agent in plasma showed minimal sequestration in lungs and liver, interpreted as indicating improved viability in comparison with cells displaying prolonged lung sequestration.

Cell labelling and cell damage with indium-111 acetylacetone-an alternative to indium 111 oxine

The labelling of HeLa S3 cells with 111In acetylacetone (111In-acac) was studied together with cell damage, measured by the reduction in colony-forming ability of labelled cells. Using 2 X 10(5) cells/ml in Hepes saline buffer at pH 7.6 incubated with 7.4-185 kBq (0.2-5.0 microCi)/ml 111In-acac, containing 0.19% acetylacetone for 15 minutes at room temperature, 60-80% 111In was bound to the cells. The cell binding was linear with activity and resulted in an exponential reduction in colony forming ability and a D0 of 26 kBq (0.7 microCi)/2 X 10(5) cells. Radiation was shown to be the major cause of cell damage. It is concluded that 111In-acac is preferable to 111In oxine because it is soluble in physiological buffers, which eliminates the use of ethanol; it is quick and easy to prepare; and compared with previous results using HeLa S3 cells labelled with 111In oxine, 111In-acac gives much more reproducible results and is no more toxic. Clinically 111In-acac was shown to give similar results to 111In oxine.

Cell damage resulting from the labeling of rat lymphocytes and HeLa S3 cells with In-111 oxine

Rat thoracic-duct lymphocytes and HeLa S3 cells were labeled in vitro with different amounts of indium-111 oxine. The labeled rat lymphocytes were tested for their ability to recirculate normally in syngeneic rats; the labeled HeLa S3 cells for their ability to divide to form colonies in tissue culture. Both cell types behaved normally by these criteria when labeled with small amounts of indium-111 oxine but at higher doses were obviously damaged. Evidence was obtained for the HeLa S3 cells that this damage was primarily radiation-induced. These findings may impose limitations on the use of In-111 oxine as a cell label for clinical purposes.

Paraffins of Cigar Smoke

Column chromatography was used to isolate a fraction from cigar smoke condensate containing a homologous series of normal paraffinic hydrocarbons; the individual hydrocarbons were separated by gas-liquid chromatography and characterized by their infrared spectra, mass spectra, and gas chromatographic behavior. Those compounds identified include the normal paraffins from dodecane to pentacosane. This fraction was isolated from the smoke condensates of four cigar types containing unblended filler tobacco that varied considerably in smoking characteristics. Qualitatively, the four types were identical, but quantitative differences were observed.