Changes in Organ Weight, Sperm Quality and Testosterone Levels After Aluminum (Al) and Indium (In) Administration to Wistar Rats

BACKGROUND

Aluminum and indium are widely used in industrial manufacturing, in pharmaceutical products, in medical treatments, and in food packaging, so they could reach organisms by different way. In order to clarify whether these elements are dangerous, we already demonstrated the ultrastructural modifications observed in the testicles, the epididymides, and the seminal vesicles of rat. Their pro-oxidative effect was also confirmed concomitantly to a decrease in anti-oxidant defenses in the blood, the testicles, and the liver. Thus, it seemed very logic to evaluate damages in the reproductive organs, especially on the exocrine and endocrine functions of the testicles.

METHODS

Aluminum and indium were intraperitoneally administered to male Wistar rats. Sperm solution was obtained from cauda epididymides. Motility, viability, density, and malformation of spermatozoa solution were assessed. Serum total unconjugated testosterone concentrations were measured using RIA technique.

RESULTS

Our results showed a decrease in weight of the testicles, epididymides, and seminal vesicles of indium-treated rats and an increase in the weight of their kidneys. A decrease in motility, viability, and density of epididymides stored sperm as well as generation of many spermatozoa malformations was also observed especially in indium-treated rats. Testosterone levels were increased in indium but were enhanced in aluminum group. This confirmed our previous studies showing that aluminum and indium are toxic for the testicular tissues. This could be explained by the generation of reactive oxygen species (ROS) affecting strongly the exocrine and the endocrine functions of the testicles.

CONCLUSION

Aluminum and indium are disturbing elements for the exocrine and endocrine functions of rat testicles.

Shell-Free Copper Indium Sulfide Quantum Dots Induce Toxicity in Vitro and in Vivo

Semiconductor quantum dots (QDs) are attractive fluorescent contrast agents for in vivo imaging due to their superior photophysical properties, but traditional QDs comprise toxic materials such as cadmium or lead. Copper indium sulfide (CuInS₂, CIS) QDs have been posited as a nontoxic and potentially clinically translatable alternative; however, previous in vivo studies utilized particles with a passivating zinc sulfide (ZnS) shell, limiting direct evidence of the biocompatibility of the underlying CIS. For the first time, we assess the biodistribution and toxicity of unshelled CIS and partially zinc-alloyed CISZ QDs in a murine model. We show that bare CIS QDs breakdown quickly, inducing significant toxicity as seen in organ weight, blood chemistry, and histology. CISZ demonstrates significant, but lower, toxicity compared to bare CIS, while our measurements of core/shell CIS/ZnS are consistent with literature reports of general biocompatibility. In vitro cytotoxicity is dose-dependent on the amount of metal released due to particle degradation, linking degradation to toxicity. These results challenge the assumption that removing heavy metals necessarily reduces toxicity: indeed, we find comparable in vitro cytotoxicity between CIS and CdSe QDs, while CIS caused severe toxicity in vivo compared to CdSe. In addition to highlighting the complexity of nanotoxicity and the differences between the in vitro and in vivo outcomes, these unexpected results serve as a reminder of the importance of assessing the biocompatibility of core QDs absent the protective ZnS shell when making specific claims of compositional biocompatibility.

In Vivo Biotransformations of Indium Phosphide Quantum Dots Revealed by X-Ray Microspectroscopy

Many attempts have been made to synthesize cadmium-free quantum dots (QDs), using nontoxic materials, while preserving their unique optical properties. Despite impressive advances, gaps in knowledge of their intracellular fate, persistence, and excretion from the targeted cell or organism still exist, precluding clinical applications. In this study, we used a simple model organism (Hydra vulgaris) presenting a tissue grade of organization to determine the biodistribution of indium phosphide (InP)-based QDs by X-ray fluorescence imaging. By complementing elemental imaging with In L-edge X-ray absorption near edge structure, unique information on in situ chemical speciation was obtained. Unexpectedly, spectral profiles indicated the appearance of In-O species within the first hour post-treatment, suggesting a fast degradation of the InP QD core in vivo, induced mainly by carboxylate groups. Moreover, no significant difference in the behavior of bare core QDs and QDs capped with an inorganic Zn(Se,S) gradient shell was observed. The results paralleled those achieved by treating animals with an equivalent dose of indium salts, confirming the preferred bonding type of In³⁺ ions in Hydra tissues. In conclusion, by focusing on the chemical identity of indium along a 48 h long journey of QDs in Hydra, we describe a fast degradation process, in the absence of evident toxicity. These data pave the way to new paradigms to be considered in the biocompatibility assessment of QD-based biomedical applications, with greater emphasis on the dynamics of in vivo biotransformations, and suggest strategies to drive the design of future applied materials for nanotechnology-based diagnosis and therapeutics.

Fluorescence Imaging of Electrically Stimulated Cells

Designing high-throughput screens for voltage-gated ion channels has been a tremendous challenge for the pharmaceutical industry because channel activity is dependent on the transmembrane voltage gradient, a stimulus unlike ligand binding to G-protein-coupled receptors or ligand-gated ion channels. To achieve an acceptable throughput, assays to screen for voltage-gated ion channel modulators that are employed today rely on pharmacological intervention to activate these channels. These interventions can introduce artifacts. Ideally, a high-throughput screen should not compromise physiological relevance. Hence, a more appropriate method would activate voltage-gated ion channels by altering plasma membrane potential directly, via electrical stimulation, while simultaneously recordingthe operation of the channel in populations of cells. The authors present preliminary results obtained from a device that is designed to supply precise and reproducible electrical stimuli to populations of cells. Changes in voltage-gated ion channel activity were monitored using a digital fluorescent microscope. The prototype electric field stimulation (EFS) device provided real-time analysis of cellular responsiveness to physiological and pharmacological stimuli. Voltage stimuli applied to SK-N-SH neuroblastoma cells cultured on the EFS device evoked membrane potential changes that were dependent on activation of voltage-gated sodium channels. Data obtained using digital fluorescence microscopy suggests suitability of this system for HTS.

Short-Term Synaptic Plasticity Regulation in Solution-Gated Indium-Gallium-Zinc-Oxide Electric-Double-Layer Transistors

In the biological nervous system, synaptic plasticity regulation is based on the modulation of ionic fluxes, and such regulation was regarded as the fundamental mechanism underlying memory and learning. Inspired by such biological strategies, indium-gallium-zinc-oxide (IGZO) electric-double-layer (EDL) transistors gated by aqueous solutions were proposed for synaptic behavior emulations. Short-term synaptic plasticity, such as paired-pulse facilitation, high-pass filtering, and orientation tuning, was experimentally emulated in these EDL transistors. Most importantly, we found that such short-term synaptic plasticity can be effectively regulated by alcohol (ethyl alcohol) and salt (potassium chloride) additives. Our results suggest that solution gated oxide-based EDL transistors could act as the platforms for short-term synaptic plasticity emulation.

Theranostic etoposide phosphate/indium nanoparticles for cancer therapy and imaging

Etoposide phosphate (EP), a water-soluble anticancer prodrug, is widely used for treatment of many cancers. After administration it is rapidly converted to etoposide, its parent compound, which exhibits anticancer activity. Difficulty in parenteral administration necessitates the development of a suitable nanoparticle delivery system for EP. Here we have used indium both as a carrier to deliver etoposide phosphate to tumor cells and as a SPECT imaging agent through incorporation of (111)In. Etoposide phosphate was successfully encapsulated together with indium in nanoparticles, and exhibited dose dependent cytotoxicity and induction of apoptosis in cultured H460 cancer cells via G2/M cell cycle arrest. In a mouse xenograft lung cancer model, etoposide phosphate/indium nanoparticles induce tumor cell apoptosis, leading to significant enhancement of tumor growth inhibition compared to the free drug.

Evaluation of in vitro antileishmanial activity of curcumin and its derivatives "gallium curcumin, indium curcumin and diacethyle curcumin"

BACKGROUND AND OBJECTIVES

Leishmania parasites are intracellular haemoflagellates that infect macrophages of the skin and viscera to produce diseases in their vertebrates hosts. Antileishmania therapy is based on pentavalent antimony compounds which toxicity of these agents and the persistence of side effects are severe. Curcumin was identified to be responsible for most of the biological effects of turmeric. Turmeric plant extracts (curcumin and other derivatives) have anti-inflammatory, anti-arthritic, antioxidant, anti-microbial, antileishmanial, hepato protective, anti-cancer, anti-ulcer and anti diabetic activity.

MATERIALS AND METHODS

Stock solutions of curcumin, indium curcumin, diacetylcurcumin and Gallium curcumin were made up in DMSO. From the each stock solution serial dilutions were made with phosphate buffered saline and 100 µl of each prepared concentration was added to each well of 96-well micro plate. All tests were performed in triplicate. Negative control only received RPMI-1640 medium with a parasite density of 106 parasites /ml and the positive control contained varying concentrations of standard antileishmania compound, Amphotericine B. MTT solution was prepared as 5 mg/ml in RPMI-1640 and 20 µl of this concentration was added to each well. Antileishmania effects of test agents and control were evaluated by using the MTT assay.

RESULTS

Mean growth inhibition of triplicate for each concentration of test agents and control were measured. The IC50 values for curcumin, gallium curcumin [ga (CUR) 3], indium curcumin [in (CUR)3], Diacethyle Curcumin (DAC ) and Amphotericine B were 38 µg/ml, 32 µg/ml, 26 µg/ml, 52 µg/ml and 20 µg/ml respectively. Indium curcumin [in (CUR) 3] with IC50 values of 26 µg/ml was more effective than other three test agents against Leishmania. Mean growth inhibition of triplicate for Amphotericine B as control drug, was 20 µg/ml.

CONCLUSIONS

Indium curcumin and Gallium curcumin complex showed more antileishmanial activity than curcumin and diacetylcurcumin and could be suitable candidates for further investigations.

Aqueous synthesis of highly luminescent AgInS₂-ZnS quantum dots and their biological applications

Highly emissive and air-stable AgInS2-ZnS quantum dots (ZAIS QDs) with quantum yields of up to 20% have been successfully synthesized directly in aqueous media in the presence of polyacrylic acid (PAA) and mercaptoacetic acid (MAA) as stabilizing and reactivity-controlling agents. The as-prepared water-dispersible ZAIS QDs are around 3 nm in size, possess the tetragonal chalcopyrite crystal structure, and exhibit long fluorescence lifetimes (>100 ns). In addition, these ZAIS QDs are found to exhibit excellent optical and colloidal stability in physiologically relevant pH values as well as very low cytotoxicity, which render them particularly suitable for biological applications. Their potential use in biological labelling of baculoviral vectors is demonstrated.

Synthesis and characterization of some new Schiff base complexes of group 13 elements, ab initio studies, cytotoxicity and reaction with hydrogen peroxide

A novel tetradentate Schiff base, naphthabza-H2=N,N'-bis(naphthylidene)-2-aminobenzylamine, and a series of aluminum(III), gallium(III), and indium(III) complexes with general formula, MLNO3, were synthesized and characterized by elemental analysis, 1H NMR, FT-IR, UV-Vis spectroscopy and thermogravimetric method. The product of the reaction of complexes with hydrogen peroxide was characterized by similar techniques. According to the ab initio calculations aluminum and gallium complexes have five-coordinated structures and indium complex is a six-coordinated one. Also, the growth inhibitory effects of the complexes toward K562 cancer cell line were measured and the results for these complexes are as follows: Al>Ga>In.

Cytotoxicity of InP/ZnS quantum dots related to reactive oxygen species generation

Indium phosphide (InP) quantum dots (QDs) have emerged as a presumably less hazardous alternative to cadmium-based particles, but their cytotoxicity has not been well examined. Although their constituent elements are of very low toxicity to cells in culture, they nonetheless exhibit phototoxicity related to generation of reactive oxygen species by excited electrons and/or holes interacting with water and molecular oxygen. Using spin-trap electron paramagnetic resonance (EPR) spectroscopy and reporter assays, we find a considerable amount of superoxide and a small amount of hydroxyl radical formed under visible illumination of biocompatible InP QDs with a single ZnS shell, comparable to what is seen with CdTe. A double thickness shell reduces the reactive oxygen species concentration approximately two-fold. Survival assays in five cell lines correspondingly indicate a distinct reduction in toxicity with the double-shell InP QDs. Toxicity varies significantly across cell lines according to the efficiency of uptake, being overall significantly less than what is seen with CdTe or CdSe/ZnS. This indicates that InP QDs are a useful alternative to cadmium-containing QDs, while remaining capable of electron-transfer processes that may be undesirable or which may be exploited for photosensitization applications.

Acylated glycosides of hydroxy fatty acid methyl esters generated from the crude resin glycoside (pharbitin) of seeds of Pharbitis nil by treatment with indium(III) chloride in methanol

Treatment of the crude ether-insoluble resin glycoside (convolvulin) from seeds of Pharbitis nil (Pharbitis Semen), called pharbitin, with indium(III) chloride in methanol provided seven oligoglycosides of hydroxy fatty acid methyl esters partially acylated by 2-methyl-3-hydroxybutyric (nilic) and 2S-methylbutyric acids. Their structures were elucidated on the basis of NMR and MS data and chemical conversions.

Oxygenation of Human Blood Using Photocatalytic Reaction

This report, as a proof of concept, presents the results of oxygenation of human blood using photocatalytic reaction (at lambda = 352 nm) involving the semiconductor thin film junction: tin doped indium oxide (ITO)/nano titanium oxide (TiO2 in anatase structure). These thin films were prepared at room temperature (300 K) on quartz, using reactive DC Magnetron sputtering techniques from pure metallic targets. The results indicate that when 10.0 mL of blood was exposed to ITO/nano TiO2 (14.32 cm surface area) at a wavelength of 352 nm for 120 minutes, the absolute increase in the whole blood oxygen content was 10.13 mL of oxygen per 100.0 mL of blood. This experiment, to our knowledge, is the first of its kind on human blood.

In vitro effect of free and complexed indium(III) against Mycobacterium tuberculosis

In mycobacteria, the study of inhibition by metal ions has been limited by the absence of suitable molecular vectors. Recently, we reported on the inhibitory activity of a family of chelators, macrocyclic compounds (MCC), against Mycobacterium tuberculosis. In this study equimolar concentrations of the free cations vanadium(IV), arsenic(III), iron(III), indium(III) and bismuth(III), and as 1:1 complexes with the MCC 1,4,8,11-tetraazacyclotetradecane-1,4,8,11-tetra-acetic acid (TETA) were tested in vitro against M. tuberculosis using the Bactec 460 TB radiometric technology (Becton-Dickinson, MD, USA). Radiometric inhibition above 80% was obtained with free indium(III) and bismuth(III), and ranged from 80% to 99%, with the complexes of TETA with vanadium(IV), bismuth(III) and indium(III), in the order of increasing activity. The highest radiometric inhibition levels were obtained with the [In(TETA)]- complex, which caused drops of up to 4 log units in cellular viability. The minimal inhibitory concentration of this compound was evaluated at 3 microM.

Synthesis and characterization of dual function vanadyl, gallium and indium curcumin complexes for medicinal applications

Novel bis[4-hydroxy-3-methoxyphenyl]-1,6-heptadiene-3,5-dione (curcumin) complexes with the formula, ML(3), where M is Ga(III) or In(III), or of the formula, ML(2) where M is [VO](2+), have been synthesized and characterized by mass spectrometry, infrared and absorption spectroscopies, and elemental analysis. A new ligand, bis[4-acetyl-3-hydroxyphenyl]-1,6-heptadiene-3,5-dione (diacetylbisdemethoxycurcumin, DABC) was similarly characterized; an X-ray structure analysis was performed. Vanadyl complexes tested in an acute i.p. testing protocol in STZ-diabetic rats showed a lack of insulin enhancing potential. Vanadyl complexes were, however, more cytotoxic than were the ligands alone in standard MTT (3-[4,5-dimethylthiazole-2-yl]ate, -2,5-diphenyl-tetrazolium bromide) cytotoxicity testing, using mouse lymphoma cells. With the exception of DABC, that was not different from VO(DABC)(2), the complexes were not significantly different from one another, with IC(50) values in the 5-10 microM range. Gallium and indium curcumin complexes had IC(50) values in the same 5-10 microM range; whereas Ga(DAC)(3) and In(DAC)(3) (where DAC=diacetylcurcumin) were much less cytotoxic (IC(50)=20-30 microM). Antioxidant capacity was decreased in VO(DAC)(2), Ga(DAC)(3), and In(DAC)(3), compared to vanadyl, gallium and indium curcumin, corroborating the importance of curcumin's free phenolic OH groups for scavenging oxidants, and correlated with reduced cytotoxic potential.

In vitro IL-1beta release from gingival fibroblasts in response to pure metals, dental alloys and ceramic

Little information is available on the immunological basis for side-effects of dental materials. The objective of this study is to evaluate effects of pure metals, dental alloys and ceramic on cell viability and interleukin-1 beta (IL-1beta) release in three-dimensional human gingival fibroblast cultures as an indicator of their biological performance in gingival tissues. The gingival fibroblast cultures were exposed to test specimens fabricated from nickel, iron, molybdenum, copper, indium, gold, Ni-Cr-Mo alloy (Remanium CS), Au-Pt-In alloy (Pontostar) and a dental ceramic (In-ceram). Cell viability was determined by the MTT method 24 and 48 h after exposure. Assays for IL-1beta were carried out by ELISA. Statistical analysis was performed applying the non-parametric Mann-Whitney pairwise test. Dental ceramic and gold did not influence cell viability after 24 and 48 h. Cell viability was determined after 24 and 48 h to nickel (79-77%), iron (92-90%), molybdenum (86-83%), copper (48-36%), indium (90-90%), Remanium CS (83-80%), Pontostar (94-91%) compared with control cultures. Dental ceramic, Pontostar and gold had no significant influence on IL-1beta secretion. The highest amounts of IL-1beta (10-fold) levels were determined in cell cultures exposed to copper. Indium, molybdenum and iron induced twofold IL-1beta levels compared with untreated control cultures. These results support that some metals may alter immune responses and thereby contribute to a variety of dental pathological conditions and three-dimensional cell culture models for gingival fibroblasts appear to be suitable for in vitro studies.

Evaluation of the Therapeutic Response to In-111-DTPA Octreotide-Based Targeted Therapy in Liver Metastatic Neuroendocrine Tumors According to CT/MRI/US Findings

Thirteen (13) patients with liver neuroendocrine carcinomas metastases, positive for somatostatin receptors, confirmed by scintigraphy were infused with 4070-7030 MBq per session of In-111-octreotide after selective hepatic catheterization, exploiting the catastrophic activity of Indium Auger and Internal Conversion electron emission on cell DNA. Evaluation of the treatment was assessed by ultrasonography (US) as well as by computed tomography and/or magnetic resonance imaging scans. US appears to be the imaging procedure of choice because the examination is sensitive for evaluating lesions' edema and cystic components, provides precise measurement of tumor size, and is inexpensive. Degeneration US signs were classified in stage I (an echolucent rim in the periphery of the lesion), stage IIa (lesion with large cystic spaces), stage IIb (tiny cystic spaces) and stage III (absorption of the cystic component or stable cystic remnants).

Induction of apoptosis by iron depletion in the human breast cancer MCF-7 cell line and the 13762NF rat mammary adenocarcinoma in vivo

It is known that the interruption of normal iron metabolism with chelators of iron, toxic metals, toxic metals bound to transferrin, or anti-transferrin receptor antibodies leads to significant inhibition of tumor cell growth in cell culture systems and animal models. In the present study, we found that iron depletion was produced by the iron chelator deferoxamine mesylate, the free toxic metals gallium or indium, and the toxic metals gallium or indium bound to transferrin in the MCF-7 human breast cancer cell line, and this induced the condensation and fragmentation of chromatin, and the formation of DNA fragments characteristic of apoptosis. The induction of apoptosis was quantitated with acridine orange and ethidium bromide staining of apoptotic cells, separation of fragmented DNA from radiolabeled cells, and in situ terminal deoxynucleotidyl transferase-mediated dUTP-digoxigenin nick end labeling (TUNEL) assays. The apoptosis, caused by deferoxamine mesylate, and gallium or indium bound to transferrin in the MCF-7 cells, can be completely inhibited by excess ferric chloride or equimolar iron-loaded transferrin. Gallium-transferrin and indium-transferrin complexes induced more apoptosis than their respective salts in the MCF-7 cells. Deferoxamine mesylate induced a small increase in the endogenous expression of both the bcl-2 and bax genes in the MCF-7 cells and this can be prevented by ferric chloride. In the 13762NF rat mammary adenocarcinoma model, in situ TUNEL assays showed that the iron-deficiency following a low iron diet or intravenous injection of deferoxamine mesylate produced 5.32 +/- 3.90% and 6.46 +/- 3.58% of apoptotic cells, respectively, compared to 2.01 +/- 1.20% of apoptotic cells in the control rats maintained on a normal diet (p < 0.05 and p < 0.01, respectively, Student's t-test). This is the first report of iron depletion caused by a low iron diet or deferoxamine mesylate treatment inducing apoptosis in rats bearing the 13762NF marnmary adenocarcinoma.

Inhibition of experimental pulmonary metastasis by controlling biodistribution of catalase in mice

In a previous study, we showed that targeted delivery of bovine liver catalase to hepatocytes by direct galactosylation augmented the inhibitory effect of the enzyme on experimental hepatic metastasis of colon carcinoma cells (unpublished data). Here, we examined the ability of catalase to inhibit tumor metastasis to the lung by controlling its biodistribution. Four types of catalase derivative, Gal-CAT, Man-CAT, Suc-CAT and PEG-CAT, were synthesized. Experimental pulmonary metastasis was induced in mice by i.v. injection of 1 x 10(5) colon 26 tumor cells. An i.v. injection of catalase (35,000 units/kg) partially, but significantly, decreased the number of colonies in the lung 2 weeks after tumor injection, from 93 +/- 29 (saline injection) to 63 +/- 23 (p < 0.01). Suc-CAT, Man-CAT and Gal-CAT showed effects similar to those of catalase on the number of colonies. However, PEG-CAT greatly inhibited pulmonary metastasis to 22 +/- 11 (p < 0.001). Furthermore, s.c. injection of catalase also greatly inhibited metastasis (11 +/- 6, p < 0.001). Neither inactivated catalase nor BSA showed any effects on the number of metastatic colonies, indicating that the enzymatic activity of catalase to detoxify H(2)O(2) is the critical factor inhibiting metastasis. (111)In-PEG-CAT showed a sustained concentration in plasma, whereas s.c.-injected (111)In-catalase was slowly absorbed from the injection site. These results suggest that retention of catalase activity in the circulation is a promising approach to inhibit pulmonary metastasis.

[Chemiluminescence suppression in roots of Pisum sativum L. by various metal ions]

The effect of rare metal ions on the activity of the peroxidase system in Pisum sativum L. roots was studied by luminol-dependent chemiluminescence. Trivalent ions of scandium, gallium, indium, and lanthanum, to different extents, inhibit the chemiluminescence of damaged P. sativum roots. A decreased generation of superoxide due to the formation of the complex between metal ions and NADP can underlie the inhibited activity of peroxidase system. The possible mechanism of inhibition of the peroxidase system activity by metal ions is discussed.

A factor produced by Escherichia coli K-12 inhibits the growth of E. coli mutants defective in the cytochrome bd quinol oxidase complex: enterochelin rediscovered

Escherichia coli produces an extracellular factor that inhibits the aerobic growth of Cyd- mutants, defective in the synthesis or assembly of the cytochrome bd-type quinol oxidase. This paper shows that such a factor is the iron-chelating siderophore enterochelin. Mutants in entA or aroB, defective in the production of enterochelin, did not produce the factor that inhibits the growth of cydAB and cydDC mutants; purified enterochelin inhibited the growth of Cyd- mutants, but not that of wild-type cells. Other iron-chelating agents, particularly ethylenediamine-di(o-hydroxyphenylacetic acid) (EDDHA), whose complex with Fe(III) has a large stability constant (log K = 33.9), also inhibited the growth of Cyd- mutants at micromolar concentrations, but not that of wild-type cells. Supplementation of agar plates with Fe(III) or boiled catalase prevented the inhibition of Cyd- mutants by the extracellular factor. Spontaneous mutants isolated by being able to grow in the presence of the extracellular factor on plates also showed increased resistance to iron chelators. The reducing agent ascorbate, ascorbate plus In(III), ascorbate plus Ga(III), or Ga(III) alone, also alleviated inhibition by the extracellular factor, presumably by reducing iron to Fe(II) and complexing of the siderophore with alternative trivalent metal cations. The preferential inhibition of Cyd- mutants by the extracellular factor and other iron chelators is not due to decrease in expression, activity or assembly of cytochrome bo', the major alternative oxidase mediating quinol oxidation. Cyd- mutants overproduce siderophores, presumably reflecting intracellular iron deprivation.

Labelling of bleomycin with Auger-emitter increases cytotoxicity in squamous-cell cancer cell lines

PURPOSE

To investigate the cytotoxicity of bleomycin (BLM), two Auger-emitting bleomycin complexes (indium-111 ((111)In)-BLMC) and (111)InCl3 in three squamous cell cancer (SCC) cell lines.

MATERIAL AND METHODS

Three recently established SCC cell lines were investigated using the 96-well clonogenic assay. Concentrations causing 50% inhibition in cell survival (IC50) were calculated for BLM and two specific activities of (111)In-BLMC (40 MBq/mg BLM (low) and 195 MBq/mg BLM (high)).

RESULTS

(111)In-BLMC (low) was the most toxic to the SCC cell lines. (111)In-BLMC containing 4.9-fold more activity of (111)In (195 MBq/mg BLM) was more effective than BLM (p=0.0029), but not as toxic as (111)In-BLMC (low) (p=0.0023). UT-SCC-19A had a IC50 value for BLM as low as 4.1 nM, whereas IC50 values for (111)In-BLMC (low) and (111)In-BLMC (high) were 2.0 nM and 2.6 nM, respectively. The most chemoresistant cell line UT-SCC-12A had a IC50 value for BLM of 18.8 nM, for (111)In-BLMC (low) 10.7 nM and for (111)In-BLMC (high) 12.7 nM. (111)InCl3 had no cell killing effect.

CONCLUSIONS

This study shows that (111)In-BLMC is superior in SCC cell killing compared with BLM. These data provide the basis for further clinical investigations of (111)In-BLMC.

[Cytocompatibility of dental alloys containing palladium]

The cytoxicity and the 50% lethal concentration (LC50) has been assessed in vitro by the colony forming method in extracts of 5 precious or semiprecious alloys and of oxides and chlorides of the metal contained in these alloys: Pd, Ag, Cu, Zn, Sn, In and Ga. All alloy extracts in culture medium induced cell death depending on their composition. In, Ga and Sn compounds showed the most favorable cell viability, Cu and Ag salts induced the lowest survival rate.

Antineoplastic drugs that interfere with iron metabolism in cancer cells

Normal iron metabolism can be perturbed with iron chelators, toxic metals that bind to transferrin, toxic metals bound to transferrin or antineoplastic agents covalently linked to transferrin. These agents cause significant inhibition of tumor cell growth in cell culture and have been shown to have significant in vivo antineoplastic activity. Cell culture studies showed that deferoxamine mesylate inhibits cell growth and division in both the MCF-7 human breast and HeLa human cervical carcinoma cell lines. Animal studies demonstrated that when deferoxamine mesylate is injected intravenously into rats that are on a low iron diet, there is a significant reduction in the growth of 13762NF mammary adenocarcinomas. Gallium, indium and the antineoplastic agent cisplatin were bound to the iron binding site of transferrin and inhibit the growth of malignant carcinoma cell lines. Gallium-transferrin and indium-transferrin were at least 10 times more inhibitory to both MCF-7 and HeLa cell lines than their free salts. Further cell culture studies demonstrated that cisplatin-transferrin complexes act synergistically with doxorubicin to inhibit the growth of cultured MCF-7 cells. In a Phase I clinical trial of cisplatin-transferrin complex there was a 36% (four of 11 patients) response rate in breast cancer patients with advanced disease. In a second clinical study the sequential administration of deferoxamine mesylate (2 days at 6 g/day in 8 hrs), cisplatin-transferrin complex (7 days at 500 mg/day) and FAC (5-fluorouracil, doxorubicin and cyclophosphamide at 450, 45 and 450 mg/m2, respectively) to advanced breast cancer patients resulted in partial responses in seven of eight patients treated. Future work will concentrate on substituting transferrin based agents with daunorubicin or doxorubicin attached to the surface of the transferrin, and gallium or indium bound to the iron binding site, to increase efficacy of the second component of the sequential combination chemotherapy.

The influence of dental metal alloys on cell proliferation and fibronectin arrangement in human fibroblast cultures

The biocompatibility of six single-phase dental metal alloys was studied by determining cell proliferation rates correlated to the arrangement of fibronectin (FN) in fibroblast cultures. Immunocytochemical methods were used to detect cell proliferation by 5-bromodeoxyuridine (BrdU) incorporation, and FN organization [i.e. diffuse in the extracellular matrix and organized in fibrils or in focal adhesions (FA)] in human fibroblast cultures. Cell proliferation rates were related to FN arrangement and in particular a higher percentage of cells in the S-phase was related to a predominance of FA. The greatest difference in behaviour compared to that of the controls was detected after 120 and 168 hr: at these times, as well as at previous ones, the alloy with the highest Au content seemed the most biocompatible among those tested, as it behaved in a very similar way to the controls. In contrast, fibroblasts exposed to the other five alloys showed different behaviours from the controls. It is assumed that a correlation exists between FN organization and the percentage of BrdU-positive cells, and that these features vary in the presence of different alloys. The observation of FN arrangement together with cell proliferation rates could be another useful tool in determining the biocompatibility of dental metal alloys.

Response of L-929 fibroblasts, human gingival fibroblasts, and human tissue mast cells to various metal cations

Recent data suggest that under certain conditions, various metal cations are released from dental alloys. These ions may produce adverse effects in various cell types in vivo. In this study, the cytopathogenic effects of 13 metal cations on murine L-929 fibroblasts, human gingival fibroblasts, and human tissue mast cells were analyzed in vitro. Several metal cations (dose range, from 0.0033 to 1.0 mmol/L) were found to induce dose-dependent inhibition of 3H-thymidine incorporation into cultured fibroblasts. The rank order of potency (lowest observed effect level, LOEL) for L-929 fibroblasts was: Ag+ > Pt4+ > Co2+ > In3+ > Ga3+ > Au3+ > Cu2+ > Ni2+ > Zn2+ > Pd2+ > Mo5+ > Sn2+ > Cr2+. A similar rank order of potency was obtained for primary human gingival fibroblasts: Pt4+ > Ag+ > Au3+ > In3+ > Ga3+ > Ni2+ > Co2+ > Zn2+ > Cu2+ > Cr2+ > Pd2+ > Mo5+ > Sn2+. In primary human mast cells, Ag+ and Au3+ caused dose-dependent toxic histamine release, whereas the other metal cations were ineffective over the dose range tested. To investigate the mechanism of metal cation-induced effects, we performed DNA as well as electron microscopic analyses on cultured fibroblasts. Both the DNA pattern and the ultrastructure of L-929 cells and gingival fibroblasts after exposure to cytopathogenic metal cations revealed signs of necrosis but no signs of apoptosis. Together, our data provide evidence that various metal cations produce dose-dependent cytopathogenic effects in distinct cell types, including human gingival fibroblasts and human tissue mast cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Alterations in the heme biosynthetic pathway from the III-V semiconductor metal, indium arsenide (InAs)

The effects of indium and arsenic on the heme biosynthetic pathway have been well documented but the effects of indium arsenide (InAs), the next possible generation of the III-V semiconductors, are unknown. Male Syrian golden hamsters were given s.c. injections of sodium arsenite (As3+), indium chloride (In3+) or indium arsenide (InAs). Erythrocyte delta-aminolevulinic acid dehydratase (ALAD) activity was inhibited in all exposure groups, while hepatic ALAD activity was not significantly changed. In contrast, the activity of renal ALAD was found to be statistically decreased by As3+ at 10 days, but increased at 30 days, while In3+ and InAs inhibited this enzyme activity at all time points. In vitro studies showed that hepatic ALAD activity was more sensitive to In3+ than As3+, suggesting that the effects of InAs in vivo on this enzyme are due primarily to the In rather than the As moiety. Studies of urinary porphyrin excretion patterns in animals treated with InAs showed marked, early 2-4-fold increase in the excretion of the penta-, hexa- and heptacarboxyl porphyrin at 1-5 days which continued through day 30 of the study. In contrast, there was a slow and steady rise in the excretion of coproporphyrin I and III which reached a maximum at day 30. The results of these studies indicate that both the In and As moieties of InAs are biologically active following InAs exposure and that the enzymes in the heme pathway, such as ALAD, may have great utility as markers of exposure/toxicity for these agents.

Modification of radiation sensitivity by salts of the metals beryllium and indium and the rare earths cerium, lanthanum and scandium

The LD50 of 46 salts of metals and rare earths (lanthanoids) was determined in mice. Half the LD50 of the compounds was then combined with lethal radiation (10.5 Gy) and the modification of survival time was scored. Only the metals beryllium and indium and the rare earths cerium, lanthanum and scandium displayed activity in our assay. They were then tested at a wider range of lower doses and reduced survival time in a dose-dependent fashion. This appears to be compatible with enhancement of radiation sensitivity. The interaction of these metals and rare earths with radiation adds a new facet to their toxicological spectrum and, by enhancing radiation effects, may influence estimates of risk. On the other hand, the radiosensitizing properties of the metals may be useful for further development of compounds to be used as adjuncts in specific situations of cancer radiotherapy.

Metal-induced conformational heterogeneity of transferrins: a spectroscopic study of indium(III) and other metal(III)-substituted transferrins

The conformation in solution of three different metal(III)-transferrins, namely aluminum(III), gallium(III) and indium(III) transferrin, was investigated by absorption, CD, 1H NMR and 13C NMR spectroscopies. The formation of the respective metal-transferrin complexes and the characteristic 2:1 metal-to-protein binding stoichiometry were unambiguously demonstrated, in all cases, through UV difference studies. The 13C NMR spectra of these metallotransferrins in the carbonyl region are very similar to one another pointing out that the arrangement of the synergistic anion in the binding site must be essentially the same. However, the CD spectra in the near UV (aromatic region) reveal the occurrence of significant differences between indium transferrin, on one side, and the other two derivatives, on the other. Also, the 1H NMR spectra exhibit a number of different features suggesting the occurrence of metal-induced conformational heterogeneity around the metal sites. Such metal-induced conformational heterogeneity probably affects the transferrin-receptor recognition process, resulting in a different metabolic fate of these metals in the organisms.

Effects of agents that inhibit cellular iron incorporation on bladder cancer cell proliferation

Agents that interfere with cellular iron (Fe) incorporation inhibit tumor cell proliferation, including metals that bind to transferrin (Tf) such as gallium (Ga) or indium (In) and Fe chelators such as desferrioxamine (DFO). Ga nitrate is effective in the treatment of metastatic bladder cancer and these patients exhibit evidence for interference with Fe metabolism. We show here that bladder cancer cell proliferation in vitro is dependent on Tf-Fe. Concentrations of DFO that can be readily achieved in vivo inhibit cellular proliferation even in the presence of physiologic concentrations of Tf-Fe. Inhibition of proliferation by Tf-Ga is associated with decreased cellular Fe incorporation. However, when a physiologic concentration of Tf-Fe is added to an equimolar concentration of Tf-Ga, significant Fe incorporation is evident despite inhibition of proliferation. Thus, besides interference with Fe incorporation, Ga may also interfere with intracellular Fe distribution and/or directly inhibit an Fe- (or non-Fe-) requiring process necessary for cellular proliferation. DFO followed sequentially by Tf-Ga results in marked potentiation of inhibition of proliferation. The effects of this combination appear to be related to both interference with Fe metabolism and increased Ga uptake. This sequential combination may be useful in the treatment of bladder cancer.

Indium inhibits gap junctional communication between rat hepatocytes in primary culture

The effect of indium on gap junctional communication was investigated in primary cultured rat hepatocytes. Treatment of hepatocytes with indium chloride at concentrations of 100 microM to 1 mM for 2 h resulted in dose-dependent inhibition of gap junctional communication between hepatocytes. The effect of indium on hepatocytes was also evaluated using two indices for cell viability: lactate dehydrogenase (LDH) leakage and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction. Indium did not cause any increase in LDH leakage from hepatocytes at the above concentrations, but inhibition of MTT reduction was observed at concentrations above 500 microM. These results suggest that the gap junctions between hepatocytes may be vulnerable sites to indium toxicity.

Group IIIA-metal hydroxides indirectly neutralize the voltage sensor of the voltage-dependent mitochondrial channel, VDAC, by interacting with a dynamic binding site

The voltage-dependent, anion-selective mitochondrial channel, VDAC, undergoes two different conformational changes from the open to a closed state under positive and negative applied electric fields. Micromolar quantities of aluminum hydroxide and other metal trihydroxides have recently been shown to be able to inhibit this voltage-dependent closure (Dill et al. (1987) J. Membr. Biol. 99, 187-196; Zhang and Colombini (1989) Biochim. Biophys. Acta 991, 68-78). It was suggested that the inhibition results from the neutralization of the positively charged voltage sensors by the metal species. In the present study, the dynamics of the metal-binding site accompanying channel closure was investigated by adding In(OH)3 to only one side of the membrane and examining its effect on the channel's gating processes. Indium added to open channels inhibited channel closure only when the metal-containing side was on the lower potential side of the applied field. If indium was added only to the higher-potential side, the channels closed and tended to remain closed after the field was abolished. The addition of metal hydroxide after closing the channels with a negative potential on the metal side did not result in channel re-opening as would be expected for sensor neutralization. Inhibition occurred immediately, however, if the channels were first allowed to open briefly. The closed-state selectivity seemed to be very similar in the absence or presence of the metal, indicating that the metal-binding sites are not located within the pore of the channel in the closed conformation. The results are consistent with a voltage-dependent translocation across the membrane of each of two metal-binding sites on VDAC. This translocation is tightly coupled with channel opening and closing.

Effects of transferrin-indium on cellular proliferation of a human leukemia cell line

In previous studies, we have demonstrated that transferrin-gallium inhibits cellular proliferation by a mechanism whereby cellular iron utilization is impaired. Since indium, a similar class 3A metal, has not been well studied, we examined its effects on cellular iron uptake and cellular proliferation. In these studies, we provide evidence that indium, when bound to transferrin, has a 50-fold higher effect on inhibition of cellular proliferation than indium added as indium salt. Cells exposed to relatively low concentrations of transferrin-indium exhibit markedly increased transferrin receptor expression but, as with transferrin-gallium, these cells incorporate an inappropriately low amount of iron, suggesting that there is a defect in the release of internalized iron from transferrin. In further studies, we utilize a monoclonal antibody against transferrin receptor that inhibits transferrin-mediated iron uptake. This antibody exhibits a dose-related inhibition of cellular proliferation, and when both transferrin-indium and monoclonal antibody are added to media, there is a more than additive effect on inhibition of cellular proliferation.

Indium selectively increases the cytochrome P-450 dependent O-dealkylation of coumarin derivatives in male mice

Indium pretreatment of rats and mice has been reported to decrease the concentration of cytochrome P-450, thereby reducing the activity of some cytochrome P-450 dependent enzymatic reactions. The present study reveals that pretreatment of C57Bl/6JHan mice of both sexes with one s.c. dose of 120 mg of In2(SO4)3.5 H2O per kg of body weight decreases the concentration of cytochrome P-450 to about 65% of control levels. Neither cytochrome b5 nor NADPH-cytochrome P-450 reductase is affected. Hepatic microsomal ethoxyresorufin O-deethylase activity declines to about 75% of control values. In contrast, with coumarin substrates, a sex dependence in the direction of change is observed: in female mice indium decreases the activity to about 75%, whereas in males it enhances the activity to 140%. Moreover, with 7-(methoxy-14C)coumarin as substrate, indium-pretreated male mice exhale about 180% and females about 65% of 14CO2 compared to the corresponding controls. A close correlation between the in vivo and in vitro effects of indium on the metabolism of the coumarin derivatives is suggested. After isolation and purification of cytochrome P-450, SDS-PAGE indicates in indium-pretreated male mice an intensification of a 48.5 kDa protein band which is decreased in females. Immunological studies using antibodies raised against control female cytochrome P-450 show cross reactivity among all microsomes used in these experiments. High percentages of inhibition occur in microsomes with high molecular activity towards coumarin derivatives. The in vitro kinetics of antibody-inhibited O-deethylation of 7-ethoxycoumarin seems to obey a non- or partial-competitive type of inhibition. Indium pretreatment of mice produces sex-dependent effects on the metabolism of coumarin derivatives.

Inhibition by aluminum hydroxide of the voltage-dependent closure of the mitochondrial channel, VDAC

Micromolar quantities of aluminum have been found (Dill et al. (1987) J. Membrane Biol. 99, 187-196) to reduce the voltage dependence of the mitochondrial outer membrane channel, VDAC, from Neurospora crassa. In the present study, various metallic and organic ions were tested for possible aluminum-like effect, and only the trivalent metals exhibited a similar ability to reduce the channels voltage dependence. However, trivalency alone was not sufficient because lanthanum (III) had no effect. Quantitative analyses with three group IIIA metals (A1, Ga, and In) showed that, of the structural characteristics examined, the ability to form sufficient M(OH)3 at experimental pH was the primary property shared by all the effective metals. While providing new insight into the nature of VDAC's sensor, these results also indicate that aluminum-cell interaction may result from the presence of AI(OH)3 in solution in addition to the widely accepted AI3+-mediated interactions. While the [AI3+] is vanishingly low at neutral pH, the trihydroxide is the major form and should be considered as an important candidate for aluminum-induced cellular effects.

In vitro function of indium-111 oxine-labeled human monocytes

Mononuclear phagocytes (monocytes and macrophages) are widely distributed throughout the body. Indium-111 (111In) oxine has been a useful radioactive label in studies of in vivo cellular kinetics and distribution. In preparation for in vivo monocyte investigations in humans, this study was designed to determine the effects of labeling human blood monocytes with 111In on their function in vitro. The monocytes labeled with an efficiency of 57.9 +/- 14.2% (range of 47-95%). The 111In eluted from the cells at a rate of 0.25%/h over 48 h in vitro. The labeled monocytes had a slight, but statistically significant, reduction in their ability to phagocytize or mediate antibody-dependent cellular cytotoxicity of antibody-coated sheep erythrocytes. The labeled cells were not different than control monocytes with respect to viability (trypan blue exclusion and lactate dehydrogenase release), adherence to plastic, hydrogen peroxide production, chemotaxis to N-formyl methionylleucylphenylalanine, and antibody-independent lysis of the tumor cells U937 and HeLa. 111In-labeled human monocytes should be useful for in vivo studies of mononuclear phagocyte kinetics and distribution in normal and diseased subjects.

Effect of unlabeled indium oxine and indium tropolone on the function of isolated human lymphocytes

The purpose of this study was to compare the effect of indium oxine and indium-tropolone complexes (nonradiolabeled) on the function of isolated human lymphocytes. peripheral lymphocytes were obtained from 15 normal volunteers and incubated with indium oxine or indium tropolone according to the standard techniques currently used when cells are radiolabeled for subsequent in vivo studies. The phytohemagglutinin-induced (PHA) lymphocyte transformation and a more specific lymphocyte functional test (the mixed lymphocyte reaction) were performed following incubation with the indium complexes. The results indicate that PHA transformation is not affected by either indium oxine or indium tropolone, whereas both chelates reduced the mixed lymphocyte reaction. This suggests that these substances have a selective toxic effect only on a functionally distinct lymphocyte subset (i.e., the cytotoxic T cells) and indicates that there is no significant difference between the two indium chelates in terms of their effect on lymphocyte function.

[111In]oxine labelling of polymorphonuclear leucocytes: doubts concerning elution and effects on cell behaviour

Polymorphonuclear leucocytes (PMN) from normal human subjects were labelled with [111In]oxine (20 muCi 10(8) cells). In the presence of 20% autologous serum (AS), dissociation of 111In from the cells resulted in mean losses of radioactivity of 13% at 3 h and 30% at 24 h. Adherence of 111In-labelled PMN to cultured porcine endothelial monolayers was increased by 40.7 +/- 31.6% after 60 min incubation in 20% AS at 37 degrees C when compared with unlabelled cells. Phagocytosis and intracellular killing of Candida albicans were unaltered by labelling. Elution of 111In from labelled PMN together with enhanced adhesiveness may have important implications for the study of PMN kinetics and the investigation of inflammatory disease.

[In vitro and in vivo studies using 111 indium oxine, 111 indium oxine sulfate and 99m Tc oxine in erythrocyte labeling]

The optimal conditions for red blood cell labelling using 111indium oxine, 111indium oxine sulphate and 99mTc oxine were established both in vitro as well as in vivo. The coagulant had no effect on labelling efficiency. Other variables such as the incubation time, temperature, duration, cell number and concentration of the complex exert a significant influence on labelling efficiency. Labelling efficiency of red blood cells is very high also under non-optimum conditions as compared with other cells (leucocytes, platelets).

An evaluation and comparison of the pulpal response to gold foil and indium alloy

All teeth restored with gold foil had pulpal changes marked by persistent hemorrhage, destruction of odontoblasts, and inflammation. Bacteria were found more frequently on cavity walls of teeth restored with gold foil and with increasing frequency for all materials as the observation period became longer. The presence or absence of bacteria could not be related to the pulpal response for either indium alloy or gold foil. Because this and previous studies indicated that gold foil in direct contact with prepared dentin surfaces produces pulpal injury, a base to protect the pulp is indicated. Indium alloy or another appropriate base could be used for the required pulpal protection.

Optimization of the DTPA mixed-anhydride reaction with antibodies at low concentration

Diethylenetriaminepentaacetic acid (DTPA) was conjugated with antibody to human serum albumin (Ab) at low concentration (300 micrograms/ml, 2.0 microM) via the DTPA carboxycarbonyl mixed-anhydride method. To study parameters determining the balance between the degree of conjugation and the antibody-binding activity of Ab, a known concentration of the anhydride prepared at isobutylchloroformate (IBC)-to-DTPA ratios of 1, 2.1, or 4.2 was reacted with Ab. The percentage yields of the anhydride were determined by spectrophotometric and gravimetric titration. By the former method the percentage yields, based on DTPA concentration, were 18, 24, and 220, respectively, when the IBC-to-DTPA ratios were 1, 2.1, and 4.2. The corresponding percentage yields were 17, 39, and 262 when determined by the latter method. When the anhydride was prepared at an IBC-to-DTPA ratio of 2.1, an optimum conjugation giving three indium atoms per Ab was obtained, with 64% retention of antibody-binding activity. For an IBC-to-DTPA ratio of 1, the antibody retained almost 100% binding activity but the number of indium atoms incorporated (0.2) was too small. For an IBC-to-DTPA ratio of 4.2, up to 22 indium atoms were incorporated but antibody-binding activity was completely destroyed.

Alteration of hepatic microsomal structure and function by indium chloride. Ultrastructural, morphometric, and biochemical studies

The effects of indium-chloride (InCl3) on hepatocyte structure and function were studied in male rats injected with doses of 0, 10, 20, or 40 mg of InCl3/kg and killed after 16 hours. Fragmentation and degranulation of the rough endoplasmic reticulum and increased numbers of In- and Fe-containing autophagic lysosomes were the most marked cellular changes observed by electron microscopy. Morphometric analyses of hepatocytes disclosed a maximal 4-fold increase in the volume density of the lysosome compartment and a 2-fold decrease in the volume density of the vacuole compartment. Surface densities of the mitochondrial cristae and rough endoplasmic reticulum were increased by 1.5-fold, whereas the surface densities of the smooth endoplasmic reticulum showed a maximal increase of 7-fold. These structural changes were associated with inhibition of microsomal aniline hydroxylase by as much as 50% and ethoxyresorufin-O-deethylase by as much as 30% but no change in aminopyrine demethylase activity. Microsomal acid phosphatase activity was also decreased to 74% of control, whereas beta-glucuronidase was unchanged. Mild inhibition of mitochondrial respiratory function but no changes in marker enzyme activities were noted. Lysosomal marker enzyme activities were also unaffected, with the exception of acid phosphatase, which was maximally decreased to 55% of control. The data indicate that acute InCl3 injection produces a primary effect on hepatocyte endoplasmic reticulum structure with attendant changes in both heme- and nonheme-dependent biochemical functions. These findings suggest that altered regulation of hepatic microsomal heme metabolism by indium and other metals occurs as part of a general process involving degradative changes in the endoplasmic reticulum structure due to membrane damage with subsequent lysosomal autophagy of nonfunctional components.

Labelling of lymphocytes with indium 111 oxine: effect on cell surface phenotype and antibody-dependent cellular cytotoxicity

Indium 111 oxine is currently used to label peripheral lymphocytes in order to study the kinetics of these cells in vivo. Since the quantity of radioisotope for labelling is still a matter of controversy, we have investigated in vitro the effect of increasing the concentration of indium 111 oxine on the lymphocyte surface phenotype and the antibody-dependent cellular cytotoxicity (ADCC) using lymphocytes from normal subjects. The cell surface phenotype, as evaluated by 2 monoclonal antibodies, was not affected whereas ADCC, at any of the doses used, was significantly reduced compared to the baseline value. The implications of these results for the use of indium 111 oxine for the in vivo studies are discussed.

Antibacterial effect of the scandium and indium complexes of enterochelin on Escherichia coli

Enterochelin, the iron chelator produced by a number of pathogenic enterobacteria, appears to be an essential metabolite for multiplication within the host, where it transports iron from the host iron-binding proteins to the bacteria. Previous work showed that complexes of enterochelin containing either scandium (Sc3+) or indium (In3+) exerted a bacteriostatic effect on Klebsiella pneumoniae in serum, whilst the Sc3+ complex exerted a significant therapeutic effect on mice infected with K. pneumoniae. These observations have now been extended to a number of pathogenic serotypes of Escherichia coli including those carrying either the K1 antigen or the ColV plasmid. The Sc3+ and In3+ complexes each exert a bacteriostatic effect on these organisms growing in either whole serum or media containing an iron-binding protein. Evidence is presented that the Sc3+ complex may act as a competitive inhibitor of the Fe3+ complex. In contrast to their effects on K. pneumoniae, sideramines other than enterochelin fail to reverse the bacteriostatic effect of the Sc3+ complex of enterochelin in E. coli, suggesting that the complex produces a more profound derangement of metabolism in this organism. The Sc3+ complex exerts a significant therapeutic effect on E. coli infections in mice although the In3+ complex is less active.

Technical considerations in the study of indium-111-oxine labelled platelet survival patterns in dogs

A detailed technique for labelling canine platelets with Indium-111-oxine for the study of platelet survival patterns in four to six dogs at a time was developed. Useful modifications of earlier methods included splitting of the platelet rich plasma into multiple aliquots to improve pelleting efficiency at low gravity forces, use of saved platelet poor plasma to flush out injection syringes, and prompt use of commercial Indium-111-oxine sources 3 to 5 minutes after mixing with Ringer's Citrate Dextrose. Avoidable pitfalls of the method included excessive lengths of incubation time in plasma free medium and loss of labelling efficacy by exposure of the chelate to iron or other metal contaminants in glassware. The method was used to study changes in platelet survival time in dogs with large synthetic arterial prostheses, and gave results in good agreement with earlier studies using Chromium-51 labelled platelets.

Measurement of antigen concentrations with a one-step inhibition assay

A device is described which is used to measure the concentration of antigen in solution. A wedge-shaped gap containing the antigen to be detected is bounded on one side by a reservoir containing specific antiserum and on the opposite side by a detection slide which has been previously coated with a layer of adsorbed antigen. As the antibodies diffuse through the gap, they complex with the soluble antigen in the wedge until these become saturated leaving additional antibody free to complex with antigen on the detection slide. By allowing diffusion to continue for an appropriate time, it is possible to relate the distance along the gap where this has occurred to the concentration of antigen within the gap. Using human IgG as a model antigen, we have been able to measure concentrations down to approximately 10 micrograms/ml with this test.

Antibacterial effect of scandium and indium complexes of enterochelin on Klebsiella pneumoniae

A number of studies point to the conclusion that enterochelin, the iron chelator produced by a number of pathogenic enterobacteria, may be an essential metabolite for bacterial multiplication within the host. The compound removes iron from complexes with the host iron-binding proteins transferrin and lactoferrin, and the resulting ferric enterochelin is assimilated by the bacterial cell. It was reasoned that complexes of enterochelin with ions other than Fe3+ might act as antimetabolites and inhibit bacterial multiplication by interfering with the assimilation of ferric enterochelin. Enterochelin forms complexes with a number of group III and transition metal ions. The complex containing scandium exerts a bacteriostatic effect on Klebsiella pneumoniae in serum, whereas the indium complex induces a large increase in the generation time. The Fe3+ complexes of other microbial iron-transporting compounds are capable of reversing the bacteriostatic effect of the Sc3+ complex of enterochelin, suggesting that the compound acts solely by interfering with the enterochelin system of iron transport. Preliminary experiments show that the Sc3+ complex probably acts as a competitive inhibitor of ferric enterochelin. The Sc3+ complex of enterochelin exerts a therapeutic effect on intraperitoneal K. pneumoniae infections in mice similar to that obtained with kanamycin sulfate.