Platelet-activating factor modulates gastric mucosal inflammatory responses to Helicobacter pylori lipopolysaccharide

Platelet-activating factor (PAF) is a phospholipid messenger implicated in mediation of inflammatory events associated with the resolution of inflammation. We applied the animal model of Helicobacter pylori LPS-induced gastritis in conjunction with prophylactic and therapeutic administration of a specific PAF antagonist, BN52020, to investigate the role of PAF in gastric mucosal responses to H. pylori infection. Prophylactic BN52020 administration produced up to 73.6% reduction in the severity of the LPS-induced inflammatory changes, whereas up to 38.4% increase in the severity of mucosal involvement occurred with BN52020 administered therapeutically. The prophylactic effects of BN52020 were accompanied by a drop in apoptosis and the expression of TNF-alpha and NOS-2, while BN52020 administered therapeutically caused a marked upregulation in apoptosis, TNF-alpha, and NOS-2. The untoward therapeutic effects of BN52020, moreover, were potentiated further in the presence of COX-2 inhibitor, whereas NOS-2 inhibitor caused a reduction in the extent of inflammatory changes. Our findings point to PAF as a key mediator of gastric mucosal inflammatory responses to H. pylori and suggest its modulatory role in the expression of COX-2 derived anti-inflammatory prostaglandins that are involved in controlling the extent of NOS-2 induction.     

Segments missing from the draft human genome sequence can be isolated by transformation-associated recombination cloning in yeast

The reported draft human genome sequence includes many contigs that are separated by gaps of unknown sequence. These gaps may be due to chromosomal regions that are not present in the Escherichia coli libraries used for DNA sequencing because they cannot be cloned efficiently, if at all, in bacteria. Using a yeast artificial chromosome (YAC)/ bacterial artificial chromosome (BAC) library generated in yeast, we found that approximately 6% of human DNA sequences tested transformed E. coli cells less efficiently than yeast cells, and were less stable in E. coli than in yeast. When the ends of several YAC/BAC isolates cloned in yeast were sequenced and compared with the reported draft sequence, major inconsistencies were found with the sequences of those YAC/BAC isolates that transformed E. coli cells inefficiently. Two human genomic fragments were re-isolated from human DNA by transformation-associated recombination (TAR) cloning. Re-sequencing of these regions showed that the errors in the draft are the results of both missassembly and loss of specific DNA sequences during cloning in E. coli. These results show that TAR cloning might be a valuable method that could be widely used during the final stages of the Human Genome Project.     

Laboratory diagnosis of invasive aspergillosis

Invasive aspergillosis is major cause of morbility and mortality in immunosuppressed patients, in part due to the inability to identify infected patients at an early stage of the disease. Diagnosis is based on a combination of imaging (high-resolution computed tomography) and a number of laboratory techniques including direct examination, culture and circulating markers (galactomannan and Aspergillus DNA) which can be detected at early stages of the infection.     

Three cases of imported histoplasmosis in our hospital

Since 1999 we have observed three cases of imported histoplasmosis in our hospital. One was an immunocompetent individual and two further patients were immunosuppressed (renal transplantation and HIV infection C3). Two patients were born in endemic areas (Equatorial Guinea and Ecuador) and a third patient had a history of previous travel to the Peruvian Amazonia. The different clinical presentations and diagnostic tools of histoplasmosis are discussed.     

The neo-X neo-Y sex pair in Acrididae,its structure and association

In most of the fifty described cases of neo-X neo-Y sex determining systems in Acrididae the pairing regions during meiosis are limited to distal regions. A comparative study on the structure and pairing mechanisms of Dichroplus silveiraguidoi (2n=8); Dichroplus bergi (2n=22) and Dichroplus vittatus (2n=20) has been undertaken. — The sex bivalents of these three grasshoppers are different: the neo-X centromere is associated with the neo-Y telomere in D. silveiraguidoi; in D. bergi the neo-X is related through the short arm telomere to the centromere of neo-Y and both members of the sex pair are associated by the telomeres in D. vittatus. Centromeric and telomeric C-band positive blocks are present in both members of the pair in the three species. D. silveiraguidoi also presents an interstitial block in the neo-X. These blocks are brightly fluorescent with quinacrine mustard and Hoechst 33258 at low concentration (0.05 g/ml). The region of neo-X corresponding to the primitive X takes an intermediate staining during the early meiotic prophase with C-banding and Hoechst 33258. — The structure of the sex bivalent and the particular staining of the X region are discussed in relation to the available information on the presence of different types of DNA in this segment. The possibility that the neo-X interstitial block of D. silveiraguidoi plays a role in preventing the spreading of heterochromatinization along the chromosome is also discussed. The classical interpretation of the neo-X neo-Y association during meiotic prophase as the result of a terminalized chiasma is considered in the light of optic and electronmicroscopic data. Other possible mechanisms of relationship between both chromosomes are also presented by these three orthopteran species.     

Effects of Calyculin A and Okadaic Acid on Acetylcholine Release and Subcellular Distribution in Rat Hippocampal Formation

Abstract : The mechanisms regulating the compartmentation of acetylcholine (ACh) and the relationship between transmitter release and ACh stores are not fully understood. In the present experiments, we investigated whether the inhibitors of serine/threonine phosphatases 1 and 2A, calyculin A and okadaic acid, alter subcellular distribution and the release of ACh in rat hippocampal slices. Calyculin A and okadaic acid significantly (p < 0.05) depleted the occluded ACh of the vesicular P₃ fraction, but cytoplasmic ACh contained in the S₃ fraction was not significantly affected. The P₃ fraction is known to be heterogeneous ; calyculin A and okadaic acid reduced significantly (p < 0.05) the amount of ACh recovered with a monodispersed fraction (D) of synaptic vesicles, but the other nerve terminal bound pools (E-F and G-H) were not so affected. K⁺-evoked ACh release decreased significantly (p < 0.01) in the presence of calyculin A and okadaic acid, suggesting that fraction D's vesicular store of ACh contributes to transmitter release. The loss of ACh from synaptic vesicle fractions prepared from tissue exposed to phosphatase inhibitors appeared not to result from a reduced ability to take up ACh. Thus, when tissue was allowed to synthesize [³H]ACh from [³H]choline, the ratio of [³H]ACh in the S₃ to P₃ fractions was not much changed by exposure of tissue to calyculin A or okadaic acid ; furthermore, the specific activity of ACh recovered from the D fraction was not reduced disproportionately to that of cytosolic ACh. The changes are considered to reflect reduced synthesis of ACh by tissue treated with the phosphatase inhibitors, rather than an effect on vesicle uptake mechanisms. Thus, exposure of tissue to calyculin A or okadaic acid appears to produce selective depletion of tissue ACh content in a subpopulation of synaptic vesicles, suggesting that phosphatases play a role in ACh compartmentation.