The luteinising hormone-releasing hormone analogue triptorelin with or without the aromatase inhibitor formestane in premenopausal breast cancer: effects on bone metabolism markers

BACKGROUND: the combination of a luteinising hormone-releasing hormone (LH-RH) analogue and an aromatase inhibitor (AI) induces greater oestrogen suppression than the analogue alone in premenopausal breast cancer. However, very few data on the biological effects of such a combination are currently available. AIM OF THE STUDY: the short-term effects of treatment with the LH-RH analogue triptorelin alone or in association with the AI formestane on bone metabolism were investigated in premenopausal breast cancer. Circulating levels of the bone formation markers carboxy-terminal and amino-terminal propeptides of type I procollagen (PICP and PINP) and the bone resorption marker cross-linked carboxy-terminal telopeptide of type I collagen (ICTP) were assessed. In addition, serum levels of insulin-like growth factor (IGF)-I, IGF binding protein (IGFBP)-3 and interleukin 6 (IL-6) were evaluated. PATIENTS AND METHODS: twenty-one patients with advanced breast cancer were randomly given triptorelin monthly alone (n=10, arm A) or in combination with formestane fortnightly (n=11, arm B). Blood samples were collected over a 3-month period. RESULTS: serum PICP and PINP levels increased significantly over time (P=0.0065 and 0.0197 in arm A and B, respectively); no change in ICTP levels was observed. A rise in IGF-I and IGFBP-3 levels was seen in each treatment group, but only the increase in IGF-I was significant (P=0.0138, always). The on-treatment levels of the bone turnover markers and IGF-system components were inversely correlated with serum oestrogens. Neither treatment modalities significantly affected serum IL-6 levels over time. No difference in the behaviour of any of the assessed biomarkers was observed between patients with or without skeletal metastases. CONCLUSION: it is worth noting that complete oestrogen depletion, at least in our case series, seems to increase only osteoblastic activity markers. The observed modifications appear to be related to oestrogen depletion per se rather than the degree of oestrogen suppression or the different therapeutic regimen administered.     

Impermeability of the GIRK2 weaver channel to divalent cations

Asingle amino acid mutation (G156S) in the putative pore-forming regionof the G protein-sensitive, inwardly rectifying K⁺ channelsubunit, GIRK2, renders the conductance constitutively active andnonselective for monovalent cations. The mutant channel subunit(GIRK2wv) causes the pleiotropic weaver disease inmice, which is characterized by the selective vulnerability ofcerebellar granule cells and Purkinje cells, as well as dopaminergicneurons in the mesencephalon, to cell death. It has beenproposed that divalent cation permeability through constitutivelyactive GIRK2wv channels contributes to a rise in internalcalcium in the GIRK2wv-expressing neurons, eventually leadingto cell death. We carried out comparative studies of recombinantGIRK2wv channels expressed in Xenopus oocytes and COS-7cells to determine the magnitude and relative permeability of theGIRK2wv conductance to Ca²⁺. Data from thesestudies demonstrate that the properties of the expressed current differin the two systems and that when recombinant GIRK2wv isexpressed in mammalian cells it is impermeable to Ca²⁺.

     

L-Propionyl-carnitine as superoxide scavenger, antioxidant, and DNA cleavage protector

L-Propionylcarnitine, a propionyl ester of L-carnitine, increases the intracellular pool of L-carnitine. It exhibits a high affinity for the enzyme carnitine acetyltransferase (CAT) and, thus, is readily converted into propionyl-coenzyme A and free carnitine. It has been reported that L-propionylcarnitine possesses a protective action against heart ischemia–reperfusion injury; however, the antioxidant mechanism is not yet clear. L-Propionylcarnitine might reduce the hydroxyl radical production in the Fenton system, by chelating the iron required for the generation of hydroxyl radicals. To obtain a better insight into the antiradical mechanism of L-propionylcarnitine, the present research analyzed the superoxide scavenging capacity of L-propionylcarnitine and its effect on linoleic acid peroxidation. In addition, the effect of L-propionylcarnitine against DNA cleavage was estimated using pBR322 plasmid. We found that L-propionylcarnitine showed a dose-dependent free-radical scavenging activity. In fact, it was able to scavenge superoxide anion, to inhibit the lipoperoxidation of linoleic acid, and to protect pBR322 DNA from cleavage induced by H₂O₂ UV-photolysis. This revised version was published online in July 2006 with corrections to the Cover Date.     

Determination of boronophenylalanine in biological samples using precolumn o-phthalaldehyde derivatization and reversed-phase high-performance liquid chromatography

A reversed-phase high-performance liquid chromatographic method for the detection of boronophenylalanine is described. Determination was obtained by precolumn reaction of o-phthalaldehyde with a mixture of standard amino acids containing boronophenylalanine and separating the corresponding o-phthalaldehyde derivatives, using a Kromasil C-18, 250 x 4.6 mm, 5-microm particle size column, a step gradient with two buffers, a flow rate of 1.2 ml/min, a column temperature of 23 degrees C, and fluorimetric detection (excitation and emission wavelengths of 330 and 430 nm, respectively). The use of such a method for assaying boronophenylalanine in biological samples was tested in neutralized perchloric acid blood and cerebral tissue extracts of rats treated with intracarotid administration of 300 mg/kg of body weight boronophenylalanine. Results of these experiments showed that the present HPLC method represents a valid alternative to currently available analytical techniques for assaying boronophenylalanine based on boron determination in terms of reproducibility, recovery, or sensitivity. Therefore, it is suggested that the present method may routinely be used in all preclinical and clinical studies in which quantification of circulating and tissue concentrations of boronophenylalanine is critical for the application of boron neutron capture therapy.     

Feeding behaviour and reproductive biology of Colorado potato beetle adults fed transgenic potatoes expressing the Bacillus thuringiensis Cry3B endotoxin

Colorado potato beetle (Leptinotarsa decemlineata Say) adult longevity and fecundity were studied on transgenic potato clones expressing a Cry3B endotoxin of Bacillus thuringiensis (Bt). Adult longevity and fitness were studied for the first 3 weeks after emergence. Beetle reproductive biology on highly resistant clones, intermediary resistant clones and control potato plants was monitored by dissecting females after 7–15 days of feeding and also by analysing haemolymph protein content after 3 days of feeding. Feeding behaviour on transgenic plants expressing high toxin concentrations and on control plants was monitored individually for 36 newly emerged adult beetles feeding on leaf disks during the first two meals. Lethal Time₅₀ for adult beetles feeding on transgenic clones as the sole source of food was not significantly shorter than for beetles on control clones reared in a growth chamber. Differences tended to be larger when the experiment was conducted in a greenhouse with a less optimal temperature range (LT₅₀ = 9.52 and 10.45 days for two transgenic clones and 13.86 for control). In contrast, female egg production on transgenic plants was almost totally inhibited. Dissection studies indicated that adult males living on high-level Bt-expressing transgenic potatoes were still able to mate and produce mobile sperm, but the females were impaired in their reproductive ability since their ovaries were generally not fully developed. An examination of the haemolymph revealed the protein concentration in females living on transgenic plants to be dramatically reduced ( 50%), and electrophoresis showed a reduced content of vitellogenin in these samples.Feeding behaviour of adult Colorado potato beetles was not affected by the different food plants; this indicates that transgenic potato plants were readily accepted as host plants by beetles. The effects of these findings on the use of transgenic plants as a means of L. decemlineata control are discussed.     

Gestational profile of leptin messenger ribonucleic acid (mRNA) content in the placenta and adipose tissue in the rat, and regulation of the mRNA levels of the leptin receptor subtypes in the hypothalamus during pregnancy and lactation

Serum leptin levels were significantly increased during rat gestation. Our data showed that leptin mRNA levels in both the adipose tissue and placenta were higher as pregnancy progressed, suggesting a role for both tissues in the hyperproduction of leptin. This paradoxical increase in leptin concentration during gestation suggests that a physiological state of leptin resistance may exist at the hypothalamic level that may explain the hyperphagia observed in pregnant rats. In order to study this issue further, levels of the mRNA encoding the different leptin receptor isoforms were determined in the hypothalamus of pregnant and nonpregnant rats. We found a specific reduction of the mRNA levels encoding the leptin receptor isoform Ob-Rb in the hypothalamus of pregnant rats compared to nonpregnant animals, suggesting that during pregnancy the hypothalamus shows a physiological resistance to the high levels of leptin due, at least in part, to a decrease in the expression of the long, biologically active form of the leptin receptor (Ob-Rb). During lactation, serum leptin levels returned to values observed in nonpregnant rats. In the hypothalami of these animals, Ob-Rb mRNA content was similar to that observed in nonpregnant rats, but we found an increased expression of some of the short forms of the leptin receptor (Ob-Re and Ob-Rf). This could contribute to induction of the hyperphagia present during lactation. These data provide new insights into the adaptive mechanisms that take place during pregnancy and lactation in order to meet increased metabolic requirements.     

P2 purinergic receptors of human eosinophils: characterization and coupling to oxygen radical production

Extracellular nucleotides elicit multiple responses in eosinophils but no information on expression of purinergic receptors in these cells is available so far. In the present study we show that human eosinophils express the following P2Y and P2X subtypes: P2Y(1), P2Y(2), P2Y(4), P2Y(6), P2Y(11), and P2X(1), P2X(4), P2X(7), whose stimulation results in intracellular Ca(2+) increase and production of large amounts of reactive oxygen intermediates. These events are stimulated or inhibited, respectively, by P2 receptor agonists or antagonists.     

Chemical synthesis and characterization of maurocalcine, a scorpion toxin that activates Ca(2+) release channel/ryanodine receptors

Maurocalcine is a novel toxin isolated from the venom of the chactid scorpion Scorpio maurus palmatus. It is a 33-mer basic peptide cross-linked by three disulfide bridges, which shares 82% sequence identity with imperatoxin A, a scorpion toxin from the venom of Pandinus imperator. Maurocalcine is peculiar in terms of structural properties since it does not possess any consensus motif reported so far in other scorpion toxins. Due to its low concentration in venom (0.5% of the proteins), maurocalcine was chemically synthesized by means of an optimized solid-phase method, and purified after folding/oxidation by using both C18 reversed-phase and ion exchange high-pressure liquid chromatographies. The synthetic product (sMCa) was characterized. The half-cystine pairing pattern of sMCa was identified by enzyme-based cleavage and Edman sequencing. The pairings were Cys3-Cys17, Cys10-Cys21, and Cys16-Cys32. In vivo, the sMCa was lethal to mice following intracerebroventricular inoculation (LD(50), 20 microg/mouse). In vitro, electrophysiological experiments based on recordings of single channels incorporated into planar lipid bilayers showed that sMCa potently and reversibly modifies channel gating behavior of the type 1 ryanodine receptor by inducing prominent subconductance behavior.