Interstitial Mr Lymphography Using Gd-Carrying Liposomes

The detection of metastasis in lymph nodes is greatly enhanced by the use of contrast media. Interstitial injection of lymphography contrast agents requires only injection of a low dose of the agent, and leads to high accumulation in regional lymph nodes with only minor side effects.

We were able to show the suitability of liposome-encapsulated gadobutrol as an interstitially injectable lymphography contrast agent in an experimental animal model. For screening of possible lymphotrophic compounds a guinea pig model was used. Accumulation of the contrast agent in 3 successive lymph node groups was determined 4 h after subcutaneous injection of the contrast agent (about 0.1 ml of a 30 mmol Gd/1 solution resulting in a total dose of 10 μmol/kg) into the interdigital skin fold of a hind limb. The Gd concentration in the first lymph node group (popliteal) was 540 μmol/1 (16% dose/g tissue), in the second group (inguinal): 260 μmol/1 (8% dose/g tissue), and in the third group (iliacal): 910 μmol/1 (27% dose/g tissue).

Moreover, this compound was completely eliminated and well tolerated.

[On the economic burden of MRSA in Germany]

INTRODUCTION

Methicillin-resistant S. aureus (MRSA) usually exhibits resistance not only against β-lactam antibiotics but also against other classes of antibiotics with the result that infections caused by this bacterium are difficult to treat. Due to additional morbidity and mortality a high economic burden can be expected.

AIM

The aim of this study was to outline the cost effects caused by MRSA colonisation and infections and to quantify the annual economic burden in Germany by using published data in order to assess the costs due to MRSA in Germany.

METHODS

Based on the available literature we estimated tangible and intangible costs per patient associated with MRSA. Total costs were calculated using data of the MRSA-KISS and the Federal Bureau of Statistics as well as other prevalence data. These costs are shown in prices of the year 2011.

RESULTS

Direct costs occurring in German hospitals are estimated to be between 354.29 million € and 1.55 billion €. Productivity losses due to an extended duration of disease are evaluated to be at least 92.77 million € while lost quality adjusted life years due to MRSA infections are estimated at 0.292 * t per infected patient (where t denotes the time of the associated health impairment).

CONCLUSION

It is not possible to quantify the total cost of illness caused by MRSA in Germany due to a lack of data on some of the direct costs (e. g., in rehabilitation facilities) as well as on the indirect and intangible costs. Nevertheless it can be shown that colonisation and infections caused by MRSA impose high costs on the health-care system and the whole economy as well.

Eprosartan in the Primary Prevention of Cardiac Allograft Vascular Disease: A Double-Blind Prospectively Randomized Study using Intravascular Ultrasound

The angiotensin blocker (ARB) eprosartan (600 mg once daily) and the calcium antagonist diltiazem (90 mg twice daily) were studied in a 24-month prospective, randomized, double-blind trial involving 53 heart transplant patients. The study compared their effects on the development of post-transplant cardiac allograft vasculopathy, a condition that frequently impairs long-term post-transplantation survival and where angiotensin blockers might be expected to play a preventive role. From baseline to month 12, the mean plaque volume increased by 7.7 mm3 for eprosartan-treated patients and by 34.4 mm3 for diltiazem-treated patients, but the eprosartan-related trend for reduced myointimal hyperplasia was not statistically significant. The trend in favour of eprosartan for secondary parameters (mean intimal index, vessel volume, lumen volume and coronary flow reserve) also failed to reach significance. The lack of effect might be due to a lower than planned sample size and observation periods due to recruitment difficulties. A larger study is required to confirm these preliminary findings.

Osteoarthritis: pathobiology-targets and ways for therapeutic intervention

Osteoarthritis is first and foremost the ongoing destruction of the articular cartilages of joints. Therefore, the extracellular matrix and the cells of the articular cartilages are the primary targets of osteoarthritis therapy. This tries to inhibit enzymatic destruction of the extracellular cartilage matrix as well as the modification of the cellular phenotype of the chondrocytes: cell degeneration and cell death are alongside anabolic activation and stabilization of the cellular phenotype of major interest. However, apart from the cartilage and its cells, other tissues of the joints are also important for the symptoms of the disease, which basically all originate outside the articular cartilage. In addition, changes in the subchondral bone as well as the synovial capsule and membrane are important at least for the progression of the disease process. All the named tissues offer different directions and ways for therapeutic intervention.

Qualitative evaluation of titanium implant integration into bone by diffraction enhanced imaging

Diffraction enhanced imaging (DEI) uses refraction of x-rays at edges, which allows pronounced visualization of material borders and rejects scattering which often obscures edges and blurs images. Here, the first evidence is presented that, using DEI, a destruction-free evaluation of the quality of integration of metal implants into bone is possible. Experiments were performed in rabbits and sheep with model implants to investigate the option for DEI as a tool in implant research. The results obtained from DEI were compared to conventional histology obtained from the specimens. DE images allow the identification of the quality of ingrowth of bone into the hydroxyapatite layer of the implant. Incomplete integration of the implant with a remaining gap of less than 0.3 mm caused the presence of a highly refractive edge at the implant/bone border. In contrast, implants with bone fully grown onto the surface did not display a refractive signal. Therefore, the refractive signal could be utilized to diagnose implant healing and/or loosening.

[Periprosthetic bone loss after total hip endoprosthesis. Dependence on the type of prosthesis and preoperative bone configuration]

The changes of the periprosthetic bone density were examined with DEXA in 81 patients over a period of 1 year after implantation of cementless total hip endoprosthesis. Four types of endoprostheses (Vision 2000/Duraloc, ALPHA-Fit/ALPHA-Lock Plus, CLS/Allofit, Mayo/Trilogy) were implanted. Information on the changes of the periprosthetic bone density depending on the type of the prosthesis and the bony situation at the femur before operation was expected from these measurements. In all types of stems the strongest reduction of the bone density was found in the region of the calcar femoris, and the smallest changes were found distally and medially of the tip of the prostheses. In the prosthesis with shorter stem the change of the bone density was altogether clearly lower than in prostheses with longer stem. With increasing size of the prosthesis with proximally porous coating made from cobalt-chrome alloy, proximal atrophy was observed more frequently, whilst in the prosthesis made from titanium alloy with completely rough-blasted surface the distal hypertrophy increased. A low preoperative corticalis-bone marrow index strengthened the proximal atrophy in proximally porously coated prosthesis made from cobalt-chrome alloy and led in the prosthesis with completely rough-blasted surface more often to distal hypertrophy of the bone.

Osteointegration of hydroxyapatite-titanium implants coated with nonglycosylated recombinant human bone morphogenetic protein-2 (BMP-2) in aged sheep

Osteointegration of metal implants into aged organisms can be severely compromised due to reduced healing capacity of bone, lack of precursor cells for new bone formation, or osteoporosis. Here, we report on successful implant healing in a novel model of aged sheep in the presence of nonglycosylated bone morphogenetic protein 2 (BMP-2). Ewes of 8 to 12 years with significant radiologic and histologic signs of osteoporosis and adipocytic bone marrow received a cylindrical hydroxyapatite-titanium implant of 12 x 10 mm. BMP-2 has been produced as a bacterial recombinant fusion protein with maltose-binding protein and in vitro generation of mature BMP-2 by renaturation and proteolytic cleavage. A BMP-2 inhibition ELISA was developed to measure the in vitro release kinetics of bioactive human BMP-2 from immersed solid implant materials by using Escherichia coli expressed and biotinylated recombinant human BMP-2 receptor IA extracellular domain (ALK-3 ECD). The implants were placed laterally below both tibial plateaus, with the left leg implant carrying 380 microg BMP-2. Both implant types became integrated within the following 20 weeks. The control implant only integrated at the cortical bone, and little new bone formation was found within the pre-existing trabecular bone or the marrow cavity. Marrow fat tissue was partially replaced by unspecific connective tissue. In contrast, BMP-2-coated implants initiated significant new bone formation, initially in trabecular arrangements to be replaced by cortical-like bone after 20 weeks. The new bone was oriented towards the cylinder. Highly viable bone marrow appeared and filled the lacunar structures of the new bone. In mechanical tests, the BMP-2-coated implants displayed in average 50% higher stability. This animal model provided first evidence that application of nonglycosylated BMP-2 coated on solid implants may foster bone healing and regeneration even in aged-compromised individuals.

Prophylaxis of heterotopic bone formation by radiotherapy -- a comparison between pre- and postsurgical activity

INTRODUCTION

Heterotopic bone formation after total hip replacement is estimated to occur in about 30% of all patients. It may develop into restriction of mobility and persisting pain.

MATERIAL AND METHODS

From 1991 to 1998, 90 patients with uncemented total hip replacement and known risks to develop heterotopic bone formation were treated by radiotherapy (14 patients received 5 x 3 gy between the first and the fifth postoperative day, 13 patients received 1 x 7 gy between 24 hours postoperative, 63 Patients received 1 x 7 gy between 24 hours preoperative) using gamma ray or high-energy photons. The distance between radiation and surgical procedure was never more than 24 hours. Clinical and radiological assessment was carried out 3, 6 and 12 month after surgery.

RESULTS

Independent of the method of radiotherapy no clinically relevant ossification was noticed on the follow up in any of the 90 patients.

CONCLUSION

The results of this study show the efficiency of radiotherapy in the prophylaxis of heterotopic bone formation, independent of the three applied methods. It seems to be important, that the interval between radiation and surgery is not longer than 24 hours. Because of possible risks and logistic problems preoperative radiation should be preferred over postsurgical treatment.

Efficacy of eprosartan in combination with HCTZ in patients with essential hypertension

This randomised, double-blind study was designed to investigate the efficacy of a once-daily (OD) combination of the AT(1) receptor blocker, eprosartan 600 mg, and the thiazide diuretic, hydrochlorothiazide (HCTZ) 12.5 mg, in patients with mild to moderate hypertension (sitting diastolic blood pressure (sitDBP) > or =98 mm Hg and < or =114 mm Hg) not adequately controlled with eprosartan 600 mg OD. A total of 494 patients entered the open-label monotherapy run-in phase, which consisted of eprosartan 600 mg OD for 3 weeks. Patients who responded to monotherapy were not eligible to enter the randomised phase of the study and were withdrawn. The remaining 309 patients were then randomised to either eprosartan 600 mg plus HCTZ 12.5 mg OD or to continue on eprosartan 600 mg OD. In the eprosartan plus HCTZ combination group, both sitDBP and sitting systolic blood pressure (sitSBP) were significantly reduced compared with the eprosartan monotherapy group. In addition, the response rate was higher in the combination group compared with the monotherapy group. There were no significant effects on reduction of sitDBP due to gender, prior use of antihypertensives or baseline severity of hypertension. The tolerability profile for the combination group was similar to that for the monotherapy group. Headache was the most frequent adverse event in both treatment groups. The majority of adverse events were mild to moderate in intensity. In this study of patients who were unresponsive to eprosartan monotherapy for 3 weeks, a combination product of eprosartan 600 mg and HCTZ 12.5 mg was shown to be an effective and well tolerated treatment.

Filter extrusion of liposomes using different devices: comparison of liposome size, encapsulation efficiency, and process characteristics

Liposomes were prepared by stepwise extrusion through 5, 1, 0.4, 0.2, 0.1 and 0.05 microm pore sizes using two different filter-extruders, the continuous high pressure device Dispex Maximator (CE) or alternatively the discontinuous Avestin LiposoFast (DE). The liposome dispersions obtained were compared in terms of particle size, lamellarity and encapsulation efficiency of calcein. The liposomes were smaller with CE than DE at all stages due to higher flow rates and pressure drops, except for final filter pore size (0.05 microm) where both preparations had similar sizes. The particle size analysis technique itself had a strong influence on the liposome sizes measured. For bigger liposomes (extruded through 0.4 microm filters) the Nicomp 370 revealed bigger volume-based mean particle sizes along with more stringent differences between volume-based and number-based diameters than the Malvern Zetasizer. In contrast, for small liposomes extruded through 0.05 microm filters, similar liposome sizes were found no matter which of the two PCS techniques or cryo-transmission electron microscopy was used. In congruence to the liposome sizes measured, encapsulation efficiencies were smaller for CE than DE at all filter stages except the final (0.05 microm). No lipid loss occurred and lyso-phosphatidylcholine formation was negligible irrespective of which extrusion technique was used.

Characterization of continuously extruded iopromide-carrying liposomes for computed tomography blood-pool imaging

RATIONALE AND OBJECTIVES

Contrast-carrying liposomes are potentially useful as computed tomography (CT) blood-pool agents. In the present study, preliminary safety, pharmacokinetics, and the CT imaging behavior of continuously extruded iopromide-carrying liposomes were studied.

METHODS

Iopromide liposomes were prepared by continuous high-pressure extrusion. Cell membrane-damaging characteristics were assessed in vitro in dog erythrocytes. Acute and subchronic toxicity and pharmacokinetics parameters were determined in rats. Computed tomography imaging efficiency was studied in rabbits.

RESULTS

The iopromide-carrying liposomes caused only minor morphological changes in dog erythrocytes. The median lethal dose in rats was approximately 4.5 g of total iodine per kilogram of body weight. In a subchronic tolerance study in rats that were administered six doses of 1 g iodine per kilogram twice a week, no adverse effects were observed. The pharmacokinetics in rats was dose dependent, and elimination of iopromide was almost complete within 7 days after intravenous administration. In rabbits, at a dose of 300 mg total iodine per kilogram, the iopromide-carrying liposomes displayed prolonged blood circulation, with mean CT density differences > 60 Hounsfield units (aorta) for up to 10 minutes.

CONCLUSIONS

The iopromide liposomes were well tolerated, almost completely excreted, and have potential as a CT blood-pool imaging agent.

The chemokine receptor CCR2 is involved in macrophage recruitment to the injured peripheral nervous system

Wallerian degeneration is one of the most elementary reactions of the nervous system after transection of axons, leading to the recruitment of mononuclear cells from the systemic circulation. However, the exact mechanisms regulating this cell invasion have not yet been clarified in detail. Chemokines and their receptors play a central role in leukocyte trafficking, in particular the chemokine MCP-1 has been strongly implicated in macrophage recruitment to the injured nervous system. The present study investigates the course of Wallerian degeneration after transection of the sciatic nerve in mice deficient in two chemokine receptors: CCR2, the main receptor for MCP-1, and CCR5, a marker for Th1 T lymphocytes but also present on macrophages. The number of invading macrophages was determined by immunocytochemistry for three typical macrophage antigens (F4/80, Mac-1, LFA-1). The chemokine receptor CCR2 was expressed by infiltrating cells in the transected nerve stumps. Macrophage invasion was significantly impaired in CCR2-knockout mice when compared with wildtype controls and CCR5-deficient mice. Subsequently, there was a corresponding decrease in myelin phagocytosis due to the reduced invasion of phagocytic macrophages. These data demonstrate the involvement of the chemokine receptor CCR2 in macrophage recruitment to the injured nervous system.

Antianginal and anti-ischaemic efficacy of tedisamil, a potassium channel blocker

OBJECTIVE

To determine the efficacy and safety of the potassium channel blocker tedisamil versus placebo in the treatment of patients with stable angina.

DESIGN

Prospective, double blind, placebo controlled study. 203 patients first completed a seven day placebo run in. They were then randomised to receive 50 mg, 100 mg or 150 mg tedisamil twice daily, or placebo. Treadmill exercise testing was carried out at baseline and after 14 days of double blind treatment.

MAIN OUTCOME MEASURES

Primary efficacy parameters were an increase in total exercise duration and a reduction of the sum of ST segment depression using six ECG leads at maximum workload at trough (12 hours after last medication). Secondary aims included increase in exercise time to onset of 0.1 mV ST segment depression, increase in exercise time to onset of any anginal pain, and reduction in ST segment depression in any of the six specified leads at maximum workload. These were all at trough. The same parameters were also assessed at peak concentrations (two hours after administration). Overall attacks of angina and the use of short acting nitrates were assessed from patient diaries.

RESULTS

Tedisamil led to a dose dependent prolongation of exercise duration (significant at all concentrations), an effect that was greater at peak than at trough. Treatment also led to a significant dose dependent reduction in the sum of ST segment depression at both trough and peak concentrations. Tedisamil also decreased (in a dose dependent way) the frequency of anginal attacks and the consumption of short acting nitrates, an improvement that became significant for all doses in the second treatment week. Adverse events with tedisamil were few. There was a pronounced rise in the incidence of diarrhoea with the 150 mg twice daily regimen. Bradycardic effects and increases in QT interval were dose dependent, but were no more evident at exercise than at rest.

CONCLUSIONS

Tedisamil, at doses of 50-100 mg twice daily, was found to be an effective antianginal and anti-ischaemic agent. At doses above 100 mg twice daily its main side effect, diarrhoea, becomes pronounced; therefore the 50-100 mg twice daily regimen appears to be appropriate.

Induction of apoptosis in porcine thyroid follicles by transforming growth factor beta1 and epidermal growth factor

For thyroid cells in culture DNA fragmentation and morphological changes related to apoptosis were first described in dog thyroid cells after deprivation of serum, epidermal growth factor or thyrotropin. With intact porcine thyroid follicles in three-dimensional culture, the effect of deprivation of growth factors and of incubation with transforming growth factor beta1 (TGF-beta1), epidermal growth factor (EGF), thyrotropin (TSH) or insulin-like growth factor I (IGF-I) on the incidence of apoptosis was studied. Thyroid follicles were embedded in growth factor-depleted Matrigel and cultured in serum-free medium with or without growth factors for 7 days followed by incubation for 4, 24 and 72 h with TGF-beta1 (2 or 5 ng/mL). The percentage of apoptotic cells was determined by direct counting in electron-microscopy. Approximately 1% of apoptotic bodies could be detected in unstimulated follicles. This was unchanged in the presence of TSH (1 mU/mL) or IGF (10 ng/mL) but significantly increased up to 3.99 +/- 1.24% with 2 ng/mL of EGF. After incubation with TGF-beta apoptosis increased dose-dependently to 4.05 +/- 0.67% with 2 ng/mL TGF-beta1 and 5.16 +/- 1.75% with 5 ng/mL TGF-beta1. The incidence of necrotic cells remained constant at about 1 to 2%. Preincubation of follicles with 2 ng/mL of EGF followed by incubation with 5 ng/mL TGF-beta1 increased the rate of apoptic bodies up to 13.19 +/- 1.9%. We conclude that growth factor depletion in thyroid follicles in three-dimensional culture does not lead to apoptosis. TGF-beta1, however, induces apoptosis even in quiescent thyroid follicular cells and is significantly more pronounced in growing thyroid cells. EGF, which is a dedifferentiating growth factor for thyroid cells, also induces apoptosis. As EGF enhances TGF-beta1 mRNA and protein in thyroid follicular cells, the induction of apoptosis by EGF might also be due to TGF-beta1.

CT blood pool enhancement in primates with lopromide-carrying liposomes containing soy phosphatidyl glycerol

RATIONALE AND OBJECTIVES

The purpose of this study was to determine the feasibility of using iodinated liposomes as blood pool agents for computed tomography (CT) in nonhuman primates.

MATERIALS AND METHODS

Five normal adult baboons (15-21 kg) were anesthetized and intravenously injected with iopromide containing soy phosphatidyl glycerol liposomes with a diameter of 195 nm. Each animal received a dose of 300 mg total iodine per kilogram (46% encapsulation).

RESULTS

The animals tolerated the injections well, experiencing no measurable electrocardiographic changes, and recovered uneventfully from anesthesia. Sequential helical CT scans of the baboons from the base of the skull to the symphysis pubis acquired up to 40 minutes after injection showed persistent blood pool enhancement. Maximum mean enhancement of major vascular structures was 106 HU at 1 minute after contrast medium injection. Mean blood pool enhancement was 76, 72, and 67 HU at 10, 20, and 40 minutes after injection, respectively. Liver and spleen were enhanced by 40 and 41 HU, respectively, 40 minutes after injection. No significant enhancement was measured in the brain and pancreas.

CONCLUSION

Soy phosphatidyl glycerol with iopromide liposomes produces prolonged vascular enhancement and has potential as a blood pool CT contrast agent in primates.

[Evaluation of the effects of bioadhesive substances as addition to oral contrast media: an experimental study]

PURPOSE

To evaluate the additional effect of bioadhesives in combination with iotrolan and barium as oral contrast media in an animal model.

METHOD

The bioadhesives Noveon, CMC, Tylose and Carbopol 934 were added to iotrolan and barium. The solutions were administered to rabbits by a feeding tube. The animals were investigated by computed tomography (CT) and radiography after 0.5, 4, 12, 24 and in part after 48 hours. Mucosal coating and contrast filling of the bowel were evaluated.

RESULTS

Addition of bioadhesives to oral contrast media effected long-term contrast in the small intestine and colon, but no improvement in continuous filling and coating of the gastrointestinal tract was detected. Mucosal coating was seen only in short regions of the caecum and small intestine. In CT the best results for coating were observed with tylose and CMC, in radiography additionally with carbopol and noveon. All contrast medium were well tolerated.

CONCLUSION

The evaluated contrast medium solutions with bioadhesives have shown long-term contrast but no improvement in coating in comparison to conventional oral contrast media.

Effects of tedisamil, atenolol and their combination on heart and rate-dependent QT interval in healthy volunteers

AIMS

Tedisamil is a new blocker of K+ currents in cardiac tissues, exerts bradycardic effects and has shown clinical efficacy in angina pectoris. Theoretically, when coadministered with a beta-adrenoceptor blocker the tedisamil combination could induce dangerous bradycardia and QT interval prolongation. Therefore, the aim of this study was to evaluate the effects of tedisamil and atenolol alone and in combination, on heart rate and QT interval duration at rest and during exercise tests.

METHODS

The effects of tedisamil (100 mg twice daily) and atenolol (50 mg twice daily) on heart rate and QT interval duration were analysed in a three-period crossover study in healthy male volunteers.

RESULTS

This study showed that tedisamil exerted a significant (P<0.05) bradycardic action at rest (-10 beats min(-1); 95% CI: -6 to -15 beats min(-1)) similar to atenolol (-14 beats min(-1); -11 to -17) and drug combination (-9 beats min(-1); -6 to -12). During exercise, at the highest comparable workload, heart rate did not decrease significantly with tedisamil but decreased significantly with atenolol (-42 beats min(-1); -37 to -47) and combination (-47 beats min(-1); -41 to 52). Atenolol did not modify QT interval duration. Tedisamil alone and in combination with atenolol increased QT interval duration by 12% (95% CI: 7 to 17%) and 12% (8 to 16) respectively at RR=1000 ms, but not at RR<700 ms (combination). Tedisamil alone and in combination induced a reverse rate-dependent QT interval prolongation.

CONCLUSIONS

These results indicate that the combination of tedisamil and atenolol is not associated with excessive bradycardia or excessive QT interval prolongation in healthy subjects.

Biodistribution and computed tomography blood-pool imaging properties of polyethylene glycol-coated iopromide-carrying liposomes

RATIONALE AND OBJECTIVES

Surface-modified contrast-carrying liposomes potentially are useful as computed tomography (CT) blood-pool agents. The biodistribution and CT-imaging behavior of conventional as well as polyethylene glycol (PEG)-coated iopromide-carrying liposomes were tested. Two different types of PEG-ylated lipids were used to demonstrate possible differences.

METHODS

Iopromide-containing liposomes were prepared by a continuous high-pressure extrusion method and subsequently PEG-ylated by simple mixing with either DSPE-PEG2000 or CHHS-PEG2000. The resulting liposomes were investigated in rats (biodistribution) and rabbits (imaging).

RESULTS

Surface modification with CHHS-PEG consistently resulted in less effective stabilization of liposomes in the blood than with DSPE-PEG. In the biodistribution study, no significant differences in blood concentration could be found 1 hour after injection between the different formulations at a dose of 250 mg total iodine/kg body weight (approximately 500 mg lipid/kg). At this dose, the unmodified as well as the DSPE-PEG liposomes displayed prolonged blood circulation with CT density differences above 70 Hounsfield units (aorta) for up to 20 minutes (n = 1).

CONCLUSIONS

DSPE-PEG-coated and unmodified liposomes proved to be useful for CT blood-pool imaging displaying favorable imaging properties. Future studies will have to demonstrate whether PEG-ylation offers diagnostic or toxicologic advantages over conventional vesicles in this indication.

Interstitial MR lymphography using Gd-carrying liposomes

The detection of metastasis in lymph nodes is greatly enhanced by the use of contrast media. Interstitial injection of lymphography contrast agents requires only injection of a low dose of the agent, and leads to high accumulation in regional lymph nodes with only minor side effects. We were able to show the suitability of liposome-encapsulated gadobutrol as an interstitially injectable lymphography contrast agent in an experimental animal model. For screening of possible lymphotrophic compounds a guinea pig model was used. Accumulation of the contrast agent in 3 successive lymph node groups was determined 4 h after subcutaneous injection of the contrast agent (about 0.1 ml of a 30 mmol Gd/l solution resulting in a total dose of 10 mumol/kg) into the interdigital skin fold of a hind limb. The Gd concentration in the first lymph node group (popliteal) was 540 mumol/l (16% dose/g tissue), in the second group (inguinal): 260 mumol/l (8% dose/g tissue), and in the third group (iliac): 910 mumol/l (27% dose/g tissue). Moreover, this compound was completely eliminated and well tolerated.

Pharmacokinetics of iopromide liposomes in rabbits

PURPOSE

The dose-proportionality of pharmacokinetics of an iodinated contrast medium, iopromide, encapsulated into liposomes was investigated.

METHODS

Following single intravenous administration of 150 mg iodine/kg (potential diagnostic dose) and a five-fold higher dose in rabbits the pattern of elimination was studied until 7 d and the blood concentrations were monitored up to 72 h after administration. The iodine concentration in the liver was calculated on the basis of the blood concentration and related to the concentration measured in the rabbit liver.

RESULTS

The dose-normalized blood concentration-time profiles of the encapsulated iodine were not superimposable. Contrary to the low dose a steady-state concentration of 2.8 mg iodine/mL was observed in blood for 60 min after the high dose administration indicating a saturation of the liposomal liver uptake. For both doses the elimination of iodine occurred predominantly via the kidneys and was complete 7 d after administration. The dose-normalized amounts of iodine excreted with the urine were similar for both dose groups. From the blood data it was calculated that doses up to about 300 mg iodine/kg should result in a dose-proportional increase of liposomal liver uptake before saturation occurs. This was confirmed by the measured iodine liver concentrations after increasing the doses stepwise from 150 to 750 mg iodine/kg.

CONCLUSIONS

In rabbits for the dose range 150 to 750 mg iodine/kg iopromide liposomes reveal dose-dependent pharmacokinetics due to a saturation in liver uptake which occurs for doses of 300 mg iodine/kg corresponding to 300 mg lipid/kg onwards.

Characterization of iopromide liposomes

RATIONALE AND OBJECTIVES

Iopromide-carrying liposomes were prepared and were characterized pharmaceutically and biologically.

METHODS

The liposomes were prepared by the ethanol evaporation method and were characterized by quasi-elastic light scattering (size) and equilibrium dialysis (encapsulation efficiency and stability). Acute and subchronic toxicity was tested in mice and/or rats and cardiovascular tolerance in rabbits. Pharmacokinetic parameters were determined in rats. Computed tomography (CT) imaging efficiency was obtained from rat and rabbit studies.

RESULTS

The mean diameter was 0.5 +/- 0.1 micron and the encapsulation efficiency ranged between 30% and 40%. The liposomes were stable in human and rabbit plasma for approximately 24 hours. The LD50 in mouse and rat was approximately 3 g iodine/kg. In a subchronic toxicity study in rats with six doses of 1 g iodine/kg given every three days, no adverse effects were observed. The pharmacokinetics in rats were dose-dependent. Increasing the dose resulted in lower total clearance, and longer terminal half-life. Elimination of iodine was complete and the main route of excretion was via the kidneys. A clinically relevant computed tomography enhancement of the liver was reached after approximately 200 mg iodine/kg in rats and 150 mg iodine/kg in rabbits.

CONCLUSIONS

The iopromide-carrying liposomes were well tolerated in animal studies and seemed to be suitable for the imaging of the liver.

Preparation and evaluation of lyophilized iopromide-carrying liposomes for liver tumor detection

RATIONALE AND OBJECTIVES

The objective of the present investigation was to demonstrate a new method for the production of iopromide-carrying liposomes. We studied biodistribution and elimination behavior, as well as the computed tomography (CT) liver imaging properties.

METHODS

Iopromide-containing liposomes were prepared by the ethanol evaporation method and subsequently lyophilized. The resuspended liposomes were tested in rats and rabbits.

RESULTS

After resuspension, liposomes with a mean diameter of 467 +/- 66 nm and an encapsulation rate of 41.5 +/- 5.5% were obtained. In rats, a marked accumulation of liposomal iopromide was found in the liver and spleen. In rabbits, complete renal elimination of iopromide within 7 days was demonstrated. At a dose of 150 mg total iodine/kg, a small tumor (< 0.5 cm) could be detected in a VX-2-bearing rabbit.

CONCLUSIONS

The ethanol evaporation method proved to be suitable for the reproducible large-scale manufacture of iopromide liposomes with high encapsulation. The resuspended liposomes displayed favorable biodistribution, elimination and imaging characteristics.

A cis-acting element responsible for early gene induction by extracellular cAMP in Dictyostelium discoideum

We have analysed the promoter of the Dictyostelium discoideum alpha-L-fucosidase (ALF) gene, and have identified a 58 bp fragment responsible for transcriptional activation mediated by extracellular cAMP. Replacement of regulatory sequences in the cAMP-independent actin 15 promoter by this fragment confers cAMP regulation to the hybrid promoter. A cAMP analog with high affinity to the cell surface cAMP receptor can induce transcription from the endogenous as well as from the hybrid promoter. Gel-shift experiments show that the 58 bp fragment is a target for nuclear DNA-binding proteins, and that a specific complex is formed in response to cAMP stimulation. The major cAMP-dependent DNA.protein complex is formed with a 22 bp subfragment which we have termed DCRE (Dictyostelium cAMP responsive element).

Regulation of the Discoidin I gamma gene in Dictyostelium discoideum: identification of individual promoter elements mediating induction of transcription and repression by cyclic AMP

We dissected the promoter of the developmentally induced and cyclic AMP-repressed discoidin I gamma gene and identified a sequence element essential for developmental induction. Transfer of the element to an inactive heterologous promoter demonstrated that this sequence is sufficient to confer expression in axenically growing cells and to induce gene activity in development after growth on bacteria. A 16-base-pair sequence within this element was shown to be sufficient for induction in the discoidin promoter context and was used to reactivate different truncated promoter constructs. This led to the localization of an element necessary for down regulation of gene expression by extracellular cyclic AMP.