Amidine derivatives are highly effective against Trypanosoma evansi trypomastigotes

The in vitro effect of N,N'-diphenyl-4-R-benzamidine (where R = H, CN, Br, Cl, CH3, OCH3 and NO2) in three isolates of Trypanosoma evansi was studied. The compounds were solubilized in dimethysulphoxide (DMSO) and tested in a concentration range of 5 to 160 micrograms/ml. The parasites were isolated from a horse, a dog and a coati. They were maintained in immunosuppressed rats, since they could not be cultured in vitro, and further purified through a diethylaminoethanol (DEAE) column. The trypomastigotes obtained were mixed with different concentrations of the drugs and after incubation at 26 degrees C for 24 h, the remaining parasites were counted in a Neubauer chamber. The percentage of inhibition was evaluated compared with the control, without the drugs. Most of the amidine derivatives showed high activity against the three T. evansi isolates, but different patterns of sensitivity to the tested compounds were observed. At least four compounds with Br, Cl, OCH3 and NO2 as substituents, were much more effective than Berenil [4,4'-(diazoamine)-dibenzamidine aceturate], the reference drug used, which is included in the same chemical class of amidines.     

Parkinsonian tremor and simplification in network dynamics

We explore the behavior of richly connected inhibitory neural networks under parameter changes that correspond to weakening of synaptic efficacies between network units, and show that transitions from irregular to periodic dynamics are common in such systems. The weakening of these connections leads to a reduction in the number of units that effectively drive the dynamics and thus to simpler behavior. We hypothesize that the multiple interconnecting loops of the brain’s motor circuitry, which involve many inhibitory connections, exhibit such transitions. Normal physiological tremor is irregular while other forms of tremor show more regular oscillations. Tremor in Parkinson’s disease, for example, stems from weakened synaptic efficacies of dopaminergic neurons in the nigro-striatal pathway, as in our general model. The multiplicity of structures involved in the production of symptoms in Parkinson’s disease and the reversibility of symptoms by pharmacological and surgical manipulation of connection parameters suggest that such a neural network model is appropriate. Furthermore, fixed points that can occur in the network models are suggestive of akinesia in Parkinson’s disease. This model is consistent with the view that normal physiological systems can be regulated by robust and richly connected feedback networks with complex dynamics, and that loss of complexity in the feedback structure due to disease leads to more orderly behavior.     

International system for standardized avian karyotypes (ISSAK): standardized banded karyotypes of the domestic fowl (Gallus domesticus)

The chicken genetic map is becoming very detailed. The genetic and physical maps need to be integrated in more detail. It is important to have a consensus banded karotype to permit this integration. An international committee met to develop a karyotype for the eight largest chromosomes and the Z and W chromosomes of the domestic fowl (Gallus domesticus). This map is presented in this report.     

Pyridoxal 5'-phosphate inactivates DNA topoisomerase IB by modifying the lysine general acid

The present results demonstrate that pyridoxal, pyridoxal 5′-phosphate (PLP) and pyridoxal 5′-diphospho-5′-adenosine (PLP-AMP) inhibit Candida guilliermondii and human DNA topoisomerases I in forming an aldimine with the ε-amino group of an active site lysine. PLP acts as a competitive inhibitor of C.guilliermondii topoisomerase I (K_i = 40 μM) that blocks the cleavable complex formation. Chemical reduction of PLP-treated enzyme reveals incorporation of 1 mol of PLP per mol of protein. The limited trypsic proteolysis releases a 17 residue peptide bearing a lysine-bound PLP (KPPNTVIFDFLGK^*DSIR). Targeted lysine (K^*) in C.guilliermondii topoisomerase I corresponds to that found in topoisomerase I of Homo sapiens (K₅₃₂), Candida albicans (K₄₆₈), Saccharomyces cerevisiae (K₄₅₈) and Schizosaccharomyces pombe (K₅₀₅). In the human enzyme, K₅₃₂, belonging to the active site acts as a general acid catalyst and is therefore essential for activity. The spatial orientation of K₅₃₂–PLP within the active site was approached by molecular modeling using available crystallographic data. The PLP moiety was found at close proximity of several active residues. PLP could be involved in the cellular control of topoisomerases IB. It constitutes an efficient tool to explore topoisomerase IB dynamics during catalysis and is also a lead for new drugs that trap the lysine general acid.     

Putative GH pulse renewal: periventricular somatostatinergic control of an arcuate-nuclear somatostatin and GH-releasing hormone oscillator

Growth hormone (GH) pulsatility requires periventricular-nuclear somatostatin(SRIF(PeV)), arcuate-nuclear (ArC) GH-releasing hormone (GHRH), and systemic GH autofeedback. However, no current formalism interlinks these regulatory loci in a manner that generates self-renewable GH dynamics. The latter must include in the adult rat 1) infrequent volleys of high-amplitude GH peaks in the male, 2) frequent discrete low-amplitude GH pulses in the female, 3) disruption of the male pattern by severing SRIF(PeV) outflow to ArC, 4) stimulation of GHRH and GH secretion by central nervous system delivery of SRIF, 5) inhibition of GH release by central exposure to GHRH, and 6) a reboundlike burst of GHRH secretion induced by stopping peripheral infusion of SRIF. The present study validates by computer-assisted simulations a simplified ensemble formulation that predicts each of the foregoing six outcomes, wherein 1) blood-borne GH stimulates SRIF(PeV) secretion after a long time latency, 2) SRIF(PeV) inhibits both pituitary GH and ArC GHRH release, 3) ArC GHRH and SRIF(ArC) oscillate reciprocally with brief time delay, and 4) SRIF(PeV) represses and disinhibits the putative GHRH-SRIF(ArC) oscillator. According to the present analytic construction, time-delayed feedforward and feedback signaling among SRIF(PeV), ArC GHRH, and SRIF(ArC) could endow the complex physiological patterns of GH secretion in the male and female.     

Atomic force microscopy measurement of leukocyte-endothelial interaction

Leukocyte adhesion to vascular endothelium is a key initiating step in the pathogenesis of many inflammatory diseases. In this study, we present real-time force measurements of the interaction between monocytic human promyelocytic leukemia cells (HL-60) cells and a monolayer of human umbilical vein endothelial cells (HUVECs) by using atomic force microscopy (AFM). The detachment of HL-60-HUVEC conjugates involved a series of rupture events with force transitions of 40-100 pN. The integrated force of these rupture events provided a quantitative measure of the adhesion strength on a whole cell level. The AFM measurements revealed that HL-60 adhesion is heightened in the borders formed by adjacent HUVECs. The average force and mechanical work required to detach a single HL-60 from the borders of a tumor necrosis factor-alpha-activated HUVEC layer were twice as high as those of the HUVEC bodies. HL-60 adhesion to the monolayer was significantly reduced by a monoclonal antibody against beta1-integrins and partially inhibited by antibodies against selectins ICAM-1 and VCAM-1 but was not affected by anti-alphaVbeta3. Interestingly, adhesion was also inhibited in a dose-dependent manner (IC50 approximately 100 nM) by a cyclic arginine-glycine-aspartic acid (cRGD) peptide. This effect was mediated via interfering with the VLA-4-VCAM-1 binding. In parallel measurements, transmigration of HL-60 cells across a confluent HUVEC monolayer was inhibited by the cRGD peptide and by both anti-beta1 and anti-alphaVbeta3 antibodies. In conclusion, these data demonstrate the role played by beta1-integrins in leukocyte-endothelial adhesion and transmigration and the role played by alphaVbeta3 in transmigration, thus underscoring the high efficacy of cRGD peptide in blocking both the adhesion and transmigration of monocytes.     

The role of shoot-localized processes in the mechanism of Zn efficiency in common bean

Zn efficiency (ZE) is the ability of plants to maintain high yield under Zn-deficiency stress in the soil. Two bean (Phaseolus vulgaris L.) genotypes that differed in ZE, Voyager (Zn-efficient) and Avanti (Zn-inefficient), were used for this investigation. Plants were grown under controlled-environment conditions in chelate-buffered nutrient solution where Zn²⁺ activities were controlled at low (0.1 pM) or sufficient (150 pM) levels. To investigate the relative contribution of the root versus the shoot to ZE, observations of Zn-deficiency symptoms in reciprocal grafts of the two genotypes were made. After growth under low-Zn conditions, plants of nongrafted Avanti, self-grafted Avanti and reciprocal grafts that had the Avanti shoot scion exhibited Zn-deficiency symptoms. However nongrafted and self-grafted Voyager, as well as reciprocal grafts with the Voyager shoot scion, were healthy with no visible Zn-deficiency symptoms under the same growth conditions. More detailed investigations into putative shoot-localized ZE mechanisms involved determinations of leaf biomass production and Zn accumulation, measurements of subcellular Zn compartmentation, activities of two Zn-requiring enzymes, carbonic anhydrase and Cu/Zn-dependent superoxide dismutase (Co/ZnSOD), as well as the non-Zn-requiring enzyme nitrate reductase. There were no differences in shoot tissue Zn concentrations between the Zn-inefficient and Zn-efficient genotypes grown under the low-Zn conditions where differences in ZE were exhibited. Shoot Zn compartmentation was investigated using radiotracer (⁶⁵Zn) efflux analysis and suggested that the Zn-efficient genotype maintains higher cytoplasmic Zn concentrations and less Zn in the leaf-cell vacuole, compared to leaves from the Zn-inefficient genotype under Zn deficiency. Analysis of Zn-requiring enzymes in bean leaves revealed that the Zn-efficient genotype maintains significantly higher levels of carbonic anhydrase and Cu/ZnSOD activity under Zn deficiency. While these data are not sufficient to allow us to determine the specific mechanisms underlying ZE, they certainly point to the shoot as a key site where ZE mechanisms are functioning, and could involve processes associated with Zn compartmentation and biochemical Zn utilization.Abbreviations CA Carbonic anhydrase - NR Nitrate reductase - SOD Superoxide dismutase - ZE Zinc efficiency This research was supported by a graduate fellowship awarded to G.H. by The Republic of Turkey     

Characterization of mesentericin ST99, a bacteriocin produced by <Emphasis Type="Italic">Leuconostoc mesenteroides</Emphasis> subsp. <Emphasis Type="Italic">dextranicum</Emphasis> ST99 isolated from boza

Lactic acid bacteria isolated from Boza, a cereal-fermented beverage from Belogratchik, Bulgaria, were screened for the production of bacteriocins. With the first screening, 13 of the 52 isolates inhibited the growth of Listeria innocua and Lactobacillus plantarum. The cell-free supernatant of one of these strains, classified as Leuconostoc mesenteroides subsp. dextranicum ST99, inhibited the growth of Bacillus subtilis, Enterococcus faecalis, several Lactobacillus spp., Lactococcus lactis subsp. cremoris, Listeria innocua, Listeria monocytogenes, Pediococcus pentosaceus, Staphylococcus aureus and Streptococcus thermophilus. Clostridium spp., Carnobacterium spp., L. mesenteroides and Gram-negative bacteria were not inhibited. Maximum antimicrobial activity, i.e. 6,400 arbitrary units (AU)/ml, was recorded in MRS broth after 24 h at 30°C. Incubation in the presence of protease IV and pronase E resulted in loss of antimicrobial activity, confirming that growth inhibition was caused by a bacteriocin, designated here as mesentericin ST99. No loss in activity was recorded after treatment with -amylase, SDS, Tween 20, Tween 80, urea, Triton X-100, N-laurylsarcosin, EDTA and phenylmethylsulfonylfluoride. Mesentericin ST99 remained active after 30 min at 121°C and after 2 h of incubation at pH 2 to 12. Metabolically active cells of L. innocua treated with mesentericin ST99 did not undergo lysis. Mesentericin ST99 did not adhere to the cell surface of strain ST99. Precipitation with ammonium sulfate (70% saturation), followed by Sep-Pack C₁₈ chromatography and reverse-phase HPLC on a C₁₈ Nucleosil column yielded one antimicrobial peptide.     

Coexisting angiomyolipoma and renal cell carcinoma in a kidney of an elderly woman: case report and review of the literature

Angiomyolipoma is a well described but relatively uncommon benign renal neoplasm composed of varying admixtures of mature adipose tissue, smooth muscle, and thick-walled blood vessels. The incidence of angiomyolipoma is about 0.3% overall. It frequently occurs in patients with tuberous sclerosis. Even more uncommon is the simultaneous occurrence of angiomyolipoma and renal cell cancer in the same kidney in a patient without tuberous sclerosis.