High frequency of drill holes in brachiopods from the Pliocene of Algeria and its ecological implications

The fossil record holds a wealth of ecological data, including data on biotic interactions. For example, holes in the skeletons of invertebrates produced by drilling activities of their enemies are widely used for exploring the intensity of such interactions through time because they are common and easily distinguished from non-biotic holes or holes produced by other types of interactions. Such drill holes have been described in numerous studies of Palaeozoic brachiopods but rarely in those focusing on brachiopods of the post-Palaeozoic, a striking pattern given that in the late Mesozoic and Cenozoic drilling gastropods diversified and frequencies of drilled molluscs increased dramatically. During the past several years, however, drilled brachiopods were reported in several studies of the Mesozoic and Cenozoic, suggesting that this phenomenon may be more common than has been previously assumed. Here we report on drilled brachiopods from a Pliocene locality in Algeria where 90 of 261 (34.5%) specimens of Megerlia truncata show evidence of predatory drilling. These data confirm that Cenozoic drilling frequencies of brachiopods may be locally high and, when taken together with other published data, that drilling frequencies are highly heterogeneous in space and time.     

Organogenesis of vegetative shoots from in vitro cultured flower buds of Mammillaria albicoma (Cactaceae)

We tested the organogenetic capacity of floral buds of Mammillaria albicoma Böed. (Cactaceae). Buds were incubated on solid MS medium supplemented with 0.1 mg l^?1 α-naphthaleneacetic acid (NAA) and 5.0 mg l^?1 6-benzylaminopurine (BA). Callus growth was observed from the cut explant base and from within the perianth. These calli during subsequent subcultures to the same medium gave rise to adventitious shoots. Shoots formed also directly from the perianth, as confirmed by observations in the light microscope and scanning electron microscope (SEM). On transfer to a fresh medium, the shoots produced proliferating cultures. This is the first report of regeneration of cactus shoots from floral explants.     

Chromium (III) Propionate and dietary fructans supplementation stimulate erythrocyte glucose uptake and beta-oxidation in lymphocytes of rats

The study describes the effects of 10-wk dietary supplementation with fructans (inulin and oligofructose, 5% and 10%, respectively) as well as the biomimetic Cr(III) propionate complex (0.5 and 5 mg Cr/kg diet) on blood glucose, insulin, glucose transmembrane transport, and β-oxidation of fatty acids in healthy male rats. No significant differences in blood serum glucose concentrations were found. Rats fed diets supplemented with the biomimetic complex (5 mg Cr/kg diet) had markedly decreased serum insulin level by 15%, whereas the red blood cells (RBCs) glucose transmembrane transport and β-oxidation of fatty acids in white blood cells (WBCs) were elevated by 9% and 77%, respectively. These effects were accompanied by a slight decrease of the insulin-resistance index. Oligofructose and the high-fructan diet (10%) were more effective in increasing the RBCs glucose transmembrane transport vs inulin and lowfructan diet (5%). Also, β-oxidation of fatty acids in WBCs was increased by 37.5% in groups fed the high-fructan diet (10%). The results suggest that dietary fructans and the biomimetic Cr(III) complex exerted beneficial effects on glucose and lipid metabolism, increasing the efficiency of their utilization.     

Conformational changes of L-rRNA during elongation of polypeptide

A ribosome undergoes significant conformational changes during elongation of a polypeptide chain, and these are correlated with structural changes of rRNAs. We tested 15 different oligonucleotides complementary to the selected, highly conserved seqences of rRNAs (L-rRNA, 5S rRNA and tRNA) important in protein biosynthesis. We carried out a reaction of binding Phe-tRNA to A site and a polymerization of polypeptide chains on the ribosomes converted either to pre- or to posttranslocational states. The inhibition of polymerization reaction by complementary oligonucleotides was high in all ribosomal states. The efficiency of inhibition of binding reaction was lower and more diverse than was the polypeptide elongation. We conclude that the selected oligonucleotides inhibit polypeptide synthesis with different effectivity, primarily depending on L-rRNA conformation within ribosome architecture.     

Enzymatic degradation studies of endomorphin-2 and its analogs containing N-methylated amino acids

In this paper, we describe the synthesis of novel endomorphin-2 analogs, containing N-methylated amino acids, consecutively in each position. The receptor-binding profile of the new analogs and their stability against enzymatic cleavage by commercially available peptidases, carboxypeptidase Y and aminopeptidase M, and a rat brain homogenate are reported. The best analog of this series, [Sar2]endomorphin-2, was almost equipotent with the parent peptide in the mu-receptor-binding assay and was also highly resistant to enzymatic degradation. This analog may be a suitable candidate for the in vivo antinociceptive studies.     

Peroxynitrite can affect platelet responses by inhibiting energy production

Peroxynitrite (ONOO-) strongly inhibits agonist-induced platelet responses. However, the mechanisms involved are not completely defined. Using porcine platelets, we tested the hypothesis that ONOO- reduces platelet aggregation and dense granule secretion by inhibiting energy production. It was found that ONOO- (25-300 microM) inhibited collagen-induced dense granule secretion (IC50 = 55 +/- 7 microM) more strongly than aggregation (IC(50) = 124 +/- 16 microM). The antiaggregatory and antisecretory effects of ONOO- were only slightly (5-10%) reduced by 1H-[1,2,4]-oxadiazolo-[4,3-alpha]quinoxalin-1-one (ODQ), an inhibitor of soluble guanylate cyclase. In resting platelets ONOO- (50-300 microM) enhanced glycolysis rate and reduced oxygen consumption, in a dose dependent manner. The ONOO- effects on glycolysis rate and oxygen consumption were not abolished by ODQ. The extent of glycolysis stimulation exerted by ONOO- was similar to that produced by respiratory chain inhibitors (cyanide and antimycin A) or an uncoupler (2,4-dinitrophenol). Stimulation of platelets by collagen was associated with a rise in mitochondrial oxygen consumption, accelerated lactate production, and unchanged intracellular ATP content. In contrast to resting cells, in collagen-stimulated platelets, ONOO- (200 microM) distinctly decreased the cellular ATP content. The glycolytic activity and oxygen consumption of resting platelets were not affected by 8-bromoguanosine 3',5'-cyclic monophosphate. Blocking of the mitochondrial ATP production by antimycin A slightly reduced collagen-induced aggregation and strongly inhibited dense granule secretion. Treatment of platelets with ONOO- (50-300 microM) resulted in decreased activities of NADH : ubiquinone oxidoreductase, succinate dehydrogenase and cytochrome oxidase. It is concluded that the inhibitory effect of ONOO- on platelet secretion and to a lesser extent on aggregation may be mediated, at least in part, by the reduction of mitochondrial energy production.     

The electrical potential difference through the foot epithelium of the snail Achatina achatina, Lameere during mechanical and chemical stimulation

An important electrophysiological variable--the transepithelial potential difference reflects the electrogenic transepithelial ion currents, which are produced and modified by ion transport processes in polarized cells of epithelium. These processes result from coordinated function of transporters in apical and basolateral cell membranes and have been observed in all epithelial tissues studied so far. The experiments were performed on isolated specimens of snail foot. In the experiments, the baseline transepithelial electrical potential difference--PD, changes of transepithelial difference during mechanical stimulation--dPD and the transepithelial resistance were measured with an Ussing apparatus. A total of 60 samples of foot ventral surface of 28 snails were studied. The transepithelial electrical potential difference of isolated foot ranged from -6.0 to 10.0 mV under different experimental conditions. Mechanical stimulation of foot ventral surface caused changes of electrogenic ion transport, observed as transient hyperpolarization (electrical potential difference became more positive). When the transepithelial electrical potential difference decreased during stimulation, the reaction was described as depolarization. When amiloride and bumetanide were added to the stimulating fluid so that the sodium and chloride ion transport pathways were inhibited, prolonged depolarization occurred. Under the influence of different stimuli: mechanical (gentle rinsing), chemical (changes of ion concentrations) and pharmacological (application of ion inhibitors), transient changes of potential difference (dPD) were evoked, ranging from about -0.7 to almost 2.0 mV. Changes in transepithelial potential difference of the pedal surface of the snail's foot related to these physiological stimuli are probably involved in the locomotion of the animal and are under control of the part of the nervous system in which tachykinin related peptides (TRP) act as transmitters.     

Evaluation of p53 and soluble Fas ligand (sFasL) serum level concentration as indicators of apoptosis in serum of patients with benign and malignant primary follicular thyroid tumors

INTRODUCTION: Apoptosis (programmed cell death) is the best described mode of physiological cell death. During embryonal development and morphogenesis, apoptosis may be induced by two pathways. The first is external protein signal originating from other cell--also named as "death signal". Another one is specific cell reaction for external stress factors. Blood concentration of proteins regulating both pathways of apoptosis may be useful in early diagnosis and staging of thyroid tumors. The aim of study was evaluation of p53 and sFasL blood concentration in patients with benign follicular adenoma and follicular thyroid cancer. MATERIALS AND METHODS: The study population was composed of 28 patients: 14 with thyroid carcinoma and 14 patients with follicular neoplasm (NF). All patients underwent surgical treatment. P53 and sFasL levels were evaluated before surgery and related to the histopathological diagnosis obtained post-surgery. RESULTS: The analysis revealed high sFasL blood concentration in patients with follicular thyroid cancer in comparison with the group with follicular adenoma. There was no statistically significant difference between levels of p53 in both groups. CONCLUSIONS: Evaluation of sFasL serum level concentration may be useful in preoperative diagnosis of follicular thyroid tumors.     

Antitumor effect of RGD-4C-GG-D(KLAKLAK)2 peptide in mouse B16(F10) melanoma model

Vasculature targeting agents have been tested as cancer therapeutics for the past few years. Such therapy could be accomplished using, for example, bifunctional (two-domain) peptides. RGD-4C-GG-D(KLAKLAK)2, a peptide designed by Ellerby and coworkers (1999) (full sequence: ACDCRGDCFCGGKLAKLAKKLAKLAK), binds selectively to alphaVbeta3 integrin receptors expressed in tumor neovasculature and, after internalization, effectively induces apoptosis of endothelial cells. The aim of this study was to examine if RGD-4C-GG-D(KLAKLAK)2 would efficiently target cells, among them B16(F10), that overexpress alphaVbeta3 receptors, and whether it would be suitable for therapeutic treatment of primary B16(F10) murine melanoma tumors. Thus, the peptide would target two distinct tumor compartments: that formed by endothelium of blood vessels and that made up of neoplastic cells. The therapeutic peptide was recognized and did induce apoptosis in B16(F10) cell line. Tumor growth inhibition was observed following direct intratumoral administration. However, cessation of peptide administration led to rapid tumor growth and death of the animals.     

Distinct genes encode type II Topoisomerases for the nucleus and mitochondrion in the protozoan parasite Trypanosoma brucei

Topoisomerases are essential for orderly nucleic acid metabolism and cell survival and are proven targets for clinically useful antimicrobial and anticancer drugs. Interest in the topologically intricate mitochondrial DNA (kinetoplast or kDNA) of Trypanosoma brucei brucei and related kinetoplastid protozoan parasites has led to many reports of type II topoisomerases that participate in kDNA metabolism (we term the T. brucei brucei gene TbTOP2mt). We have now identified and characterized two new genes for type II topoisomerases in T. brucei brucei, termed TbTOP2alpha and TbTOP2beta. Phylogenetically, they share a common node with other nuclear topoisomerases, clearly distinct from a clade that includes the previously reported kinetoplastid genes, all of which are homologs of TbTOP2mt. Southern blot analysis reveals the new genes are single copy and positioned approximately 1.7 kb apart. Cognate mRNAs are expressed in African trypanosomes, but only a single message is detected in Leishmania or Crithidia. TbTOP2alpha encodes an ATP-dependent topoisomerase that appears as a single approximately 170-kDa band on immunoblots and localizes to the nucleus; RNA interference leads to pleomorphic nuclear (but not kDNA) abnormalities and early growth arrest. The role of TbTOP2beta is unclear. Although transcribed in trypanosomes, TbTOP2beta is not detected by beta-specific antiserum, and RNAi silencing results in no obvious phenotype. These studies indicate that African trypanosomes and related kinetoplastid human pathogens are unusual in having independent topoisomerase II genes to service their nuclear and mitochondrial genomes, and they highlight TbTOP2alpha as a promising target for the development of much-needed new therapies.