IL-1 MODIFIES SYSTEM A TRANSPORT ACTIVITY IN HUMAN RHEUMATOID SYNOVIAL CELLS

Given the importance of interleukin-1 in both rheumatic diseases and the modulation of cell metabolic activities, we studied the action of this cytokine on the neutral amino acid transport A system on rheumatoid synovial cells. In these cells IL-1 (1ng/ml) induced amino transport stimulation from 5min to 5h. This effect was obtained only after a starvation period. No concentration-related effect was found for IL-1-stimulated MeAIB uptake, and the IL-1-mediated MeAIB uptake stimulation is independent of protein synthesis. Neosynthesis or post-translational maturation of protein transport is a prerequisite for obtaining this effect. In conclusion, rheumatoid synovial cells exhibit a higher sensitivity for IL-1 than osteoarthritic ones, probably related to their intense metabolic activity.     

A NEW PCR METHOD OF CHARACTERIZING SEAFISH FRESHNESS

Objective criteria used to assess the fish freshness in the laboratory are currently inadequate. During contamination of muscle tissue, bacteria reduce trimethylamine oxide (TMAO) to trimethylamine (TMA) in the absence of oxygen. Based on this reaction, we envisaged a new approach and have developed and optimized a PCR method which targets the tor A gene sequence that encodes TMAO reductase. We applied this method to two fish species (Whiting (Merlangus merlangus) and Pouting (Gadus luscus)) during monitoring of spoilage, in parallel with assay of TVBN and enumeration of total aerobic flora. The PCR results tally with the chemical and microbiological findings. Used in quantitative PCR, this method could characterize fish freshness.     

Dimeric DOTA-α-Melanocyte-Stimulating Hormone Analogs: Synthesis and In Vivo Characteristics of Radiopeptides with High In Vitro Activity

Dimeric analogs of α-melanocyte-stimulating hormone (α-MSH) labeled with radiometals are potential candidates for diagnosis and therapy of melanoma by receptor-mediated tumor targeting. Both melanotic and amelanotic melanomas (over-)express the melanocortin-1 receptor (MC1-R), the target for α-MSH. In the past, dimerized MSH analogs have been shown to display increased receptor affinity compared to monomeric MSH, offering the possibility of improving the ratio between specific uptake of radiolabeled α-MSH by melanoma and nonspecific uptake by the kidneys. We have designed three linear dimeric analogs containing a slightly modified MSH hexapeptide core sequence (Nle-Asp-His-d-Phe-Arg-Trp) in parallel or antiparallel orientation, a short spacer, and the DOTA chelator for incorporation of the radiometal. In vitro, all three peptides were more potent ligands of the mouse B16-F1 melanoma cell melanocortin-1 receptor (MC1-R) than DOTA-NAPamide, which served as standard. The binding activity of DOTA-diHexa(NC-NC)-amide was 1.75-fold higher, that of diHexa(NC-NC)-Gly-Lys(DOTA)-amide was 3.37-fold higher, and that of DOTA-diHexa(CN-NC)-amide was 2.34-fold higher. Using human HBL melanoma cells, the binding activity of diHexa(NC-NC)-Gly-Lys(DOTA)-amide was sixfold higher than that of DOTA-NAPamide. Uptake by cultured B16-F1 cells was rapid and almost quantitative. In vivo, however, the data were less promising: tumor-to-kidney ratios 4 hr postinjection were 0.11 for [¹¹¹In]DOTA-diHexa(NC-NC)-amide, 0.26 for diHexa(NC-NC)-Gly-Lys([¹¹¹In]DOTA)-amide, and 0.36 for [¹¹¹In]DOTA-diHexa(CN-NC)-amide, compared to 1.67 for [¹¹¹In]DOTA-NAPamide. It appears that despite the higher affinity to the MC1-R of the peptide dimers and their excellent internalization in vitro, the uptake by melanoma tumors in vivo was lower, possibly because of reduced tissue penetration. More striking, however, was the marked increase of kidney uptake of the dimers, explaining the unfavorable ratios. In conclusion, although radiolabeled α-MSH dimer peptides display excellent receptor affinity and internalization, they are no alternative to the monomeric DOTA-NAPamide for in vivo application.     

α-KETOGLUTARATE UPTAKE IN HUMAN FIBROBLASTS

Glutamine requirements are increased during injury, in particular to sustain the needs of rapidly growing cells. This includes fibroblasts involved in wound healing. α-Ketoglutarate (α-KG) has been proved to be a potent precursor of glutamine. However, little is known about the process of its cell uptake. Since this first step could be crucial in α-KG metabolism, we have characterized α-ketoglutarate uptake in fibroblasts. Total uptake of α-ketoglutarate was linear up to 1mmol and temperature independent. Rate of uptake was independent of the presence of Na⁺in the medium. Competition studies with another ketoacid demonstrated the non-specificity of α-ketoglutarate uptake. In addition, 4-hydroxy-α-cyanocinnamate, a known inhibitor of anion transport, was ineffective on α-ketoglutarate uptake. Taken as a whole, these data provide evidence that α-ketoglutarate uptake in fibroblast occurs by an unmediated diffusion process. This suggests that α-ketoglutarate uptake is not the controlling step in fibroblasts, i.e. only the availability of extracellular α-ketoglutarate. This could be an advantage since during injury, cell membrane depolarization and dissipation of Na⁺gradient may limit cellular glutamine uptake.     

Ecology of the biting midge Leptoconops albiventris in French Polynesia. III. Influence of abiotic factors on breeding sites. Towards ecological control?

Abstract. Correspondance Analysis was used to determine the significant abiotic factors influencing the ecology of the immature stages of Leptoconops albiventris (Diptera: Ceratopogonidae). The breeding places required strict environmental conditions: fine and well-sorted sand, with low conductivity and humidity. However, the microdistribution of the immature stages within a breeding site does not depend on such factors. Modifying physical parameters in the larval breeding areas might be an important component in future ecological control programmes against L.albiventris populations.     

Vocal individuality in the roding calls of Woodcock Scolopax rusticola and their use to validate a survey method

The Woodcock Scolopax rusticola is a difficult species to survey in the breeding season because of its cryptic plumage and, with the exception of courtship flights, secretive behaviour. Sparse data from general bird surveys prohibit reliable estimation of population sizes and trends, and a new species-specific method to provide baseline information on population status and to enable reliable future monitoring is required. Counts of displaying, or 'roding', males at dawn or dusk potentially provide such a method but their value is unclear because it is impossible for an observer to distinguish different birds. We examined the vocal individuality of 39 roding males and were able to attribute calls to individuals correctly in 95% of cases on the basis of five parameters measured from spectrograms. Using calls, we determined the number of individual males at 43 sites. Roding activity differed between males at one site, with the two most active birds accounting for, on average, 55 and 27% of passes. There was no evidence of sequential roding by different males. We quantified the relationship between numbers of males and numbers of passes of roding birds during a 1-h period at dusk. This relationship was not affected by region, month, habitat or woodland size class. We conclude that counts of roding males provide a suitable index for monitoring populations of this species.     

Ecology of the biting midge Leptoconops albiventris in French Polynesia. II. Location of breeding sites and larval microdistribution

Abstract. The habitat of the immature stages of Leptoconops albiventris de Meijere (Diptera: Ceratopogonidae) was found to be in beach sand located above the high tide level near creeping vegetation. The immatures were restricted to a narrow strip and most occurred in the upper 6 cm of sand. Within a given breeding site, larvae were aggregated in their distribution. Eggs were layed on the bare sand surface, from which the larvae apparently dispersed to the plant-covered sand and to deeper strata, before returning to the surface for pupation and emergence. The nature of these breeding sites suggests that it is possible to control L.albiventris populations. Recovery of immature stages from sand samples by a flotation method is described.     

Ecology of the biting midge Leptoconops albiventris in French Polynesia. I. Biting cycle and influence of climatic factors

Abstract. The diurnal biting cycle of Leptoconops albiventris de Meijere (Diptera: Ceratopogonidae) is described from beaches of Nuku-Hiva, French Polynesia. Biting activity increased during the morning, diminished during the afternoon and was sufficiently intense to constitute a nuisance throughout the whole day. Correspondence Analysis indicated that climatic factors influenced biting activity. Activity was initiated by and positively associated with sunshine, whereas high temperatures, increased wind speed and rainfall were factors limiting activity. Decreased density of females during the dry season and their low capacity for dispersal were considered potentially advantageous with respect to control.