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Biomedical subjects

R Arnould

Publications and source records attributed to R Arnould.

At least 19 recordsLinked to original sources
PubMed1993

Labelled polycyanoacrylate nanoparticles for human in vivo use.

Isobutyl and isohexyl cyanoacrylate nanoparticles are used as drug carriers, particularly for some anti-cancer drugs. Body distribution as well as pharmacokinetics have been well studied in animal and partially in man. Labelling of the monomer itself or of the carried drug with beta-emitters allowed such studies. In man, however, organ distribution and uptake could easily be done and followed by means of scintigraphy (imaging) techniques if one could achieve nanoparticle labelling with gamma-emitting isotopes. We have developed labelling methods able to supply such carriers using gamma-emitters like radioactive iodine (125I or 131I), indium or technetium. We used DTPA as a spacer in order to fix the last two isotopes. This would mean that any other gamma-emitting cation can theoretically be tried pending on its ability to be chelated by DTPA. The preparations were obtained with high labelling yields, usually > 80% and were relatively stable in human plasma over the whole period of investigation. 111In and 99mTc labelled forms have been administered to rabbit and then to man with 60-75% accumulation in the reticulo-endothelial system.

Animals↗
PubMed1984

Production of the effector molecule thymidine by human lung alveolar macrophages.

Cultured human alveolar macrophages (HAM phi) were found to produce soluble factors which inhibit tritiated thymidine [( 3H]-TdR) incorporation into tumour cells in vitro. We present evidence that thymidine (TdR) can be detected in HAM phi culture supernatants by thin-layer chromatography. Moreover, TdR secretion by HAM phi is an active process. Using [6-14C]-orotic acid as an early precursor to TdR and [3H]-TMP as the phosphorylation product, we were able to show that cultured HAM phi transformed them into labelled TdR. The very efficient thin-layer chromatography of the labelled metabolites was backed up by high-pressure liquid chromatography of nucleotides. HAM phi produce TdR by de novo synthesis and dephosphorylation. This phenomenon is due to the lack of thymidine kinase in normal mature macrophages. Since TdR, in high concentrations, can inhibit DNA synthesis through the 'TdR blockade' phenomenon, it is suggested that TdR secretion by HAM phi is a mechanism of non-specific modulation of tumour cell growth but highly restricted to the immediate macrophage microenvironment in vivo. The effectiveness of the thymidine gradient may thus be quite narrow, but is worthy of interest.

Animals↗
PubMed1978

[Role of protein in control of the growing chick's appetite].

After a short study of the literature about the effect of proteins on the food intake regulation, the authors conclude that the only way to compare two feeds about their intake level consist in a comparison with animals of nearly the same live weight by expressing the intakes plotted against live weight. Themselves, they compare ingestions by chickens of rations which vary by their protein level and quality. In a first step, authors show that increasing the protein content of the ration led to a rise in the food intake, but then, beyond a critical level of protein, the food intake decreases gradually. In a second step, authors show that a better quality of the food protein leads to an increase on intake. In conclusion, proteins influence food intake not because they satisfy the nitrogen need of the animal, but because they saturate the blood in products coming from the catabolism of their non utilised fraction.

Animals↗
PubMedDate not supplied

Pharmacokinetics of daunorubicin and daunorubicinol in plasma, P388 and B16 tumours. Comparison with in vitro cytotoxicity data.

The comparison of pharmacokinetics of DNR in mouse plasma, in the DNR naturally resistant B16 melanoma and in the DNR naturally sensitive P388 leukemia showed that there is no direct correlation between total concentrations of this drug in tumours and the sensitivity resistance of these tissues. A finding which demonstrates the inadequacy of distribution models to select new potential anticancer drugs. Cytotoxicity of DNR and its metabolites to B16 melanoma and P388 leukemia cell lines were determined in vitro. Calculated inhibitory concentrations 50 (IC50) were compared to maximal concentrations determined by pharmacokinetic studies. In all cases in vitro IC50 were lower than Cmax values. Moreover, resistant cells in vivo were found to be sensitive to DNR and metabolites when they are propagated in vitro. Tissue concentrations, as well as in vitro data, were fitted to appropriate models by an original program (FADHA) which uses the simplex method to minimize a non-linear cost function. Best fit models were chosen by statistical criteria.

Analysis of Variance↗
PubMedDate not supplied

Human melanoma targeting with alpha-MSH-melphalan conjugate.

A conjugate made of alpha-MSH as a drug carrier and melphalan has been designed in order to target human melanoma cells. Iodination of the alpha-MSH moiety led to a relatively stable tracer which could be easily separated and analysed by reverse phase high pressure liquid chromatography. The conjugate was found to be unstable at neutral pH and a serious denaturation can take place at concentrations exceeding 100 micrograms/ml, especially in plasma. Receptor-mediated cytotoxicity has been shown by the use of cultured alpha-MSH receptor positive/negative cells as well as in vivo B16 murine melanoma model. Body distribution and uptake of the labelled compound were unaltered as compared to those of labelled free hormone. alpha-MSH receptor recognition properties also remained unchanged with a better apparent affinity of the conjugate probably due to the alkylating activity of melphalan itself. Using human melanoma dendritic cells expressing more than 10,000 alpha-MSH binding sites per cell as an in vitro model, we were able to demonstrate higher cytotoxicities as compared to melphalan-treated cells. In contrast, melanoma cells with low receptivity did not show higher cytotoxicity. P388D1 mouse plasmocytoma cells lacking receptors were much more sensitive to melphalan than the conjugate. This phenomenon appeared to be related with the number of binding sites expressed at the time of the experiment as well as cell differentiation and the doubling time. Our findings strongly support the concept of a receptor-mediated cytotoxicity and may enable the in vivo melphalan delivery to target tissues to be increased, achieving an improvement of drug penetration inside melanoma cells.

Amino Acid Sequence↗
PubMedDate not supplied

Use of an alpha-melanocyte-stimulating hormone analogue to improve alpha-melanocyte-stimulating hormone receptor binding assay in human melanoma.

In order to optimize the detection and measurement of alpha-melanocyte-stimulating hormone (alpha-MSH) receptivity in human melanoma cells, and the authors replaced the natural hormone by [Nle4,D-Phe7]-alpha-MSH, a more stable and potent analogue in the receptor binding assay commonly performed with alpha-MSH. The following parameters were investigated: temperature, incubation time, number of cells, and ratio of labelled to unlabelled hormone. Optimal conditions for each assay were determined. The results demonstrate that the analogue has identical binding sites to alpha-MSH, as similar reciprocal displacements of each labelled (125I) hormone by serial dilutions of unlabelled alpha-MSH or [Nle4,D-Phe7]-alpha-MSH (10(-12) M to 10(-6) M) were obtained. To further compare the two hormones, we performed a screening of various human cell lines: ten melanomas and five nonmelanomas. The assay with [Nle4,D-Phe7]-alpha-MSH yielded more receptor expression on six of ten melanoma lines against only four of ten with the natural hormone. In conclusion, the use of radiolabelled [Nle4,D-Phe7]-alpha-MSH analogue instead of labelled alpha-MSH improved both sensitivity and reproducibility in this receptor binding assay on human melanoma lines.

Humans↗
PubMedDate not supplied

Alpha-melanocyte-stimulating hormone immunoreactivity in human melanoma metastases extracts.

Seven human melanoma metastases were extracted in order to check the possible presence of any alpha-melanocyte stimulating hormone (MSH) immunoreactivity. The aim of that study was to provide some explanation for, mainly, two observations that we have already made and reported: 1) increased plasma alpha-MSH levels in melanoma of tumour-bearing patients as compared with tumour-free patients; 2) the presence of specific alpha-MSH receptors on human melanoma cells in culture. We could measure large amounts of immunoreactive alpha-MSH in all tumours ranging from 0.31 to 4.27 pmoles per g of wet tissue. Further identification of the extracted material by high-performance liquid chromatography revealed compounds of higher molecular weight and more hydrophobic than synthetic alpha-MSH. In addition, purified extracts could also displace 125I-labelled alpha-MSH from its cellular binding sites in an alpha-MSH specific radio-receptor binding assay. Our findings would suggest a possible presence of some hormone precursor(s) inside the melanoma tumours.

Aged↗
PubMedDate not supplied

In vitro cytotoxicity of hexamethylmelamine (HMM) and its derivatives.

The cytotoxicity of hexamethylmelamine (HMM) and its metabolites was investigated in three murine cell lines: one in vitro naturally sensitive to HMM (RC) and two in vivo naturally resistant (P388 and P388D1). The percentage of viable cells was determined both by the in situ reduction of a tetrazolium salt (MTT assay) and by the uptake of labelled thymidine into DNA (3HTdR assay). Short (1h) and long (48h) exposures of cells to drugs were considered. In all experimental conditions used, HMM was found to be inactive, whereas its hydroxylated metabolite hydroxymethylpentamethylmelamine (HMPMM) and one analog N, N 'dihydroxymethyltetramethylmelamine (DHTMM) were found to be cytotoxic. The results further indicated that HMM must be metabolized before it can exert its cytotoxic effect. The activity of HMPMM and DHTMM was found unlikely to be related to extracellular or intracellular release of formaldehyde.

Altretamine↗
PubMedDate not supplied

Comparison of two cytotoxicity assays--tetrazolium derivative reduction (MTT) and tritiated thymidine uptake--on three malignant mouse cell lines using chemotherapeutic agents and investigational drugs.

Two different techniques [reduction of a tetrazolium derivative (MTT) and 3HTdR uptake assays] were compared in order to evaluate the cytotoxic effects of different chemotherapeutic agents in vitro. The cytotoxicities of Melphalan, hexamethylmelamine and seven derivatives, and daunorubicin were measured on P388D1 mouse macrophage-like cell line, RC mouse renal carcinoma cell line, and B16 mouse melanoma cell lines. Growth inhibition was determined after one hour as well as after continuous (48 hours) exposure to drugs. The IC50 was calculated using an appropriate algorithm (FADHA) which allowed within and between run variabilities to be taken into account. Optimal conditions had to be elucidated for culture conditions before assay: number of cells/well and assay duration for each line. The MTT and 3HTdR uptake assays were found to be similar in terms of sensitivity and reproducibility, both for adherent and floating cell lines. However, the MTT assay has the advantages of low cost and time saving. It also avoids problems related to radioactivity manipulation and counting. Both techniques rank the same chemicals as active or inactive. The algorithm Fadha was found to be a very powerful mathematical tool for comparing the IC50 values obtained by both assays.

Animals↗
PubMedDate not supplied

Compared cytotoxicity effects of five anticancer drugs on human (HBL) and mouse (B16) melanoma cells in vitro.

In order to assess the potential interest of replacing the murine cell lines by human cell lines for in vitro cytotoxic assays, the sensitivity and the selectivity of the murine B16 and the human HBL melanomas to five chemotherapeutic drugs were investigated in vitro. The cytotoxicities of Melphalan, Daunorubicin (DNR), Hexamethylmelamine (HMM), Hydroxymethylpentamethylmelamine (HMPMM), and Dihydroxymethyltetramethylmelamine (DHTMM), 2 HMM derivatives, were measured in the two cell lines using two different techniques: reduction of a tetrazolium derivative (MTT) and tritiated thymidine uptake into DNA. The cytotoxicity at inhibitory concentration 50 (IC50) was determined after one hour as well as after 2 days exposure of cell after one hour as well as after 2 days exposure of cells to each drug. The results indicate that the HBL human melanoma was generally more sensitive to Melphalan and DHTMM than the B16 murine melanoma cells as far as the IC50 was concerned. In contrast, no difference of sensitivity was found to DNR and DHTMM. HMM was found to be inactive in both cell lines. The analysis of variance on IC50 values showed that the sensitivity of murine and human melanoma cell lines to drugs was statistically different. Despite the identical selectivity of the two cell lines, two promising observations can be made as far as the comparison of the two cell lines is concerned: 1) the higher sensitivity of HBL human cell line to Melphalan in the in vitro assays and 2) the slightly lower sensitivity of HBL to DNR, a drug without clinical activity against human melanoma.

Analysis of Variance↗
PubMedDate not supplied

Studies on factors influencing human plasma alpha-MSH.

The various physiological effects of alpha-MSH, mainly on the CNS and on pigmentation in animal models, are well documented in the literature. Only a few investigators have confirmed similar properties in the human. However, the possible physiopathological role played by this hormone in human melanoma is still poorly defined. In order to approach this subject in a manner as complete as possible, we have performed, during the past four years, three different series of experiments: 1) alpha-MSH measurements in plasma samples from: a. melanoma and other cancer patients, b. whole body UVA irradiated healthy adults, c. circadian rhythm determinations in melanoma patients and in healthy male adults; 2) alpha-MSH measurements in human melanoma tumours; 3) alpha-MSH receptor expression on human melanoma cells in culture involving: a. alpha-MSH radio-binding assays and b. tyrosinase assay. Our results so far show 1) increased alpha-MSH levels in melanoma patients' plasma, alpha-MSH responsiveness to UVA stimulated skin, large immunoreactive alpha-MSH content in melanoma metastases and an alpha-MSH circadian rhythm in some individuals different from cortisol; 2) alpha-MSH receptor expression in melanoma cells could be increased by various effectors able to stimulate melanogenesis.

Aged↗