Cytological and morphological studies of the action of lithium on the development of the sea urchin embryo

Summary The effect of lithium ions on cleavage and development of sea urchin larvae was investigated. Lithium was found to interfere with the movements of the chromosomes at mitosis, which is also very delayed in the presence of lithium. The disturbances inflicted by lithium were observed during the course of development up to the pluteus stage.The lithium sensitive period coincides with the period in which the mitotic activity reaches its maximum.The rate of cleavage is reduced by lithium. In the normal untreated larva there is during the early blastula stage an animal trend in which the formation of cells of prospective ectodermal significance preponderates. The mesomeres were found to be relatively more affected by lithium than were the macromeres. This shift in the cleavage pattern influences the numbers of cells of ectodermal and endo-mesodermal significance.Studies were also made of morphological changes following treatment with lithium.     

High surface hydrophobicity of hemagglutinatingVibrio cholerae and other vibrios

Surface hydrophobicity of hemagglutinatingVibrio cholerae, Vibrio parahaemolyticus, and NAG vibrios has been investigated. Most strains caused mannose-sensitive hemagglutination of monkey, guinea pig, chicken, and mannose-resistant hemagglutination of human erythrocytes with different degrees of hemagglutinating activity. Hemagglutinating strains adsorbed to a hydrophobic gel (Octyl Sepharose), whereas nonhemagglutinating strains failed to adsorb.Vibrio cholerae and other vibrios investigated seem to have pronounced surface hydrophobicity as estimated by Octyl Sepharose and they correspondingly autoaggregated into visible cell clumps in ammonium sulfate solution at low molarity (0.2–0.4 M). Nonhemagglutinating strains did not aggregate even at high (2 M) ammonium sulfate concentration. The presence of surface hemagglutinins of vibrios is growth-media-dependent. Strains, grown in four different liquid media, produced hemagglutinins and expressed pronounced surface hydrophobicity. Studies with electron microscopy revealed the presence of fimbriae on the vibrio cells. The number of fimbriae on the cells varied from strain to strain. Some strains possessed more than 300 fimbriae/cell whereas others had less than 10 fimbriae/cell. Vibrio hemagglutinins are easily detached from the cell surface by heating or sonication, and their cell surface hydrophobicity decreased simultaneously.     

Microscale patchiness of plankton within a sharp pycnocline

Microscale distributions of plankton around the pycnocline werestudied over a 24 h period in the southern Kattegat, using agradient sampler which collects 20 samples over a 3 m depthinterval. Moderately elevated concentrations of phyto- and zooplanktonwere observed at the pycnocline. Microscale variance was highestfor adult copepods. Nauplii and copepodites were equally wellrepresented by sampling with ordinary vertical 5 1 water bottlesas with the horizontal 1.5 1 bottles of the gradient sampler.Adult copepods were underestimated by the vertical bottles.No vertical migration of dinoflagellates was observed over the3 m interval covered by the gradient sampler. Microscale correlationsbetween copepods and phytoplankton within the gradient samplerwere weak. Copepodites (mainly Oithona sp.) and the dinoflagellateProrocentrum micans showed the best correlation.     

Gastrointestinal colonisation of BALB/cA mice by Helicobacter pylori monitored by heparin magnetic separation

Abstract Immunocompetent and immunodeficient BALB/cA mice were fed orally with 10⁸ colony forming units of 2-day-old spiral or coccoid (12 days old) Helicobacter pylori strain NCTC 11637. Immunocompetent BALB/cA mice were also fed orally with decreasing numbers of spiral or coccoid forms of H. pylori . The gastrointestinal colonisation process was monitored for 34 days post-infection by heparin magnetic separation and subsequent enzyme immunoassay (EIA) for the detection of the H. pylori cells. Both mice types were colonised with H. pylori . The coccoid form of H. pylori gave higher EIA absorbance values and more efficient colonisation in the mice than the spiral form. Immunocompetent BALB/cA mice fed with the coccoid form of H. pylori exhibited an acute inflammation process in histopathological samples from the stomachs. In conclusion, H. pylori can infect both immunocompetent as well as immunodeficient BALB/cA mice and coccoids (viable but non-culturable) obtained after 12 days of culturing can infect BALB/cA mice.     

Immunochemical properties of a 60 kDa cell surface-associated heat shock-protein (Hsp60) from Helicobacter pylori

Abstract Western blot analysis (immunoblotting) of cell surface-associated proteins from Helicobacter pylori confirmed our previous findings that binding of human IgG is a common property (among H. pylori strains). Purification of the IgG-binding proteins (IGBP) was achieved by two purification steps, affinity chromatography on IgG-Sepharose and nickel chelate affinity chromatography. SDS-PAGE and immunoblotting analysis revealed a 60 kDa protein with affinity for peroxidase labeled human IgG. Solid phase binding assays showed that IgG binds to an immobilized protein (IGBP). The 60 kDa IGBP binds human IgG₁, IgG₃ and IgM. Binding could be inhibited by the kappa chain of the human IgG, but not with its Fc fragment, nor with IgA or IgM. In addition, rabbit polyclonal antibodies raised against the 60 kDa IGBP blocked IgG binding. Monoclonal antibodies, specific to the Hsp60 heat shock protein of H. pylori recognized the 60 kDa IGBP as revealed by immunoblotting analysis, both in crude preparations and in the purified fractions.     

Adhesion ofHelicobacter pylori strains toα-2,3-linked sialic acids

Helicobacter pylori is a human pathogen associated with gastritis and peptic ulcer. Adhesion properties ofH. pylori to various structures have been described in the literature, including evidence for sialic acid-binding. To study the specificity and frequency of sialic acid-binding, fourteenH. pylori strains were investigated using haemagglutination with derivatized erythrocytes carrying sialic acids only on defined glycans and using haemagglutination inhibition assays. From these studiesH. pylori strains can be grouped into sialic acid-dependent and sialic acid-independent classes. The sialic acid-dependent strains require -2,3-linked sialic acid for haemagglutination. The potential roles of sialic acid-dependent adhesions forH. pylori-related infections are discussed.Abbreviations Sia sialic acids - Neu5Ac N-acetyl-neuraminic acid - Neu5Gc N-glycolylneuraminic acid - Neu5Fm N-formylneuraminic acid - Neu5TFA N-trifluoroacetylneuraminic acid - RBC human red blood cells (erythrocytes)     

Zooplankton diversity and the predatory impact by larval and small juvenile fish at the Fisher Banks in the North Sea

The biomass and diversity of the mesozooplankton and fish larvaecommunity were investigated across a frontal zone in the centralNorth Sea in the early summer, to investigate whether larvalfish predation is a regulator of mesozooplankton production.Pronounced changes in the mesozooplankton community were observedacross the front off the Jutlandic coast. The biomass and thediversity of copepods changed across the front as the populationof Calanus finmarchicus became abundant in the deeper water.The crustaceans (Acartia spp. and Evadne spp.) and polychaetelarvae dominated the mesozooplankton in the coastal water. Thebiomass of fish larvae was dominated by gadoid larvae. As inthe copepods, a shift in fish diversity was observed in thefrontal zone. On the coastal side of the front, whiting (Merlangiusmerlangus) dominated the biomass, while offshore from the frontwhiting were absent and cod (Gadus morhua) was the dominantlarval fish species on the deeper stations. The present investigationdemonstrates two different trophic pathways related to hydrographyin the central North Sea. First, in the shallow coastal water,the abundant small neritic copepods are predominately predatedby whiting, while in the offshore region the larger oceaniccopepods are predated by cod larvae. However, the predationpressure by the fish larvae was in general low (<10%) relativeto copepod production per day. Consequently, in the early summer,the copepod production potentially results in a build-up ofcopepod biomass on both sides of the front.     

Significance of size and nucleic acid content heterogeneity as measured by flow cytometry in natural planktonic bacteria.

Total bacterial abundances estimated with different epifluorescence microscopy methods (4',6-diamidino-2-phenylindole [DAPI], SYBR Green, and Live/Dead) and with flow cytometry (Syto13) showed good correspondence throughout two microcosm experiments with coastal Mediterranean water. In the Syto13-stained samples we could differentiate bacteria with apparent high DNA (HDNA) content and bacteria with apparent low DNA (LDNA) content. HDNA bacteria, "live" bacteria (determined as such with the Molecular Probes Live/Dead BacLight bacterial viability kit), and nucleoid-containing bacteria (NuCC) comprised similar fractions of the total bacterial community. Similarly, LDNA bacteria and "dead" bacteria (determined with the kit) comprised a similar fraction of the total bacterial community in one of the experiments. The rates of change of each type of bacteria during the microcosm experiments were also positively correlated between methods. In various experiments where predator pressure on bacteria had been reduced, we detected growth of the HDNA bacteria without concomitant growth of the LDNA bacteria, such that the percentage contribution of HDNA bacteria to total bacterial numbers (%HDNA) increased. This indicates that the HDNA bacteria are the dynamic members of the bacterial assemblage. Given how quickly and easily the numbers of HDNA and LDNA bacteria can be obtained, and given the similarity to the numbers of "live" cells and NuCC, the %HDNA is suggested as a reference value for the percentage of actively growing bacteria in marine planktonic environments.     

Binding of Selected Extracellular Matrix Proteins to Enterococci and Streptococcus bovis of Animal Origin

Thirty-three enterococcal strains and 10 Streptococcus bovis strains were investigated for their protein-binding cell surface components. Seven extracellular matrix (ECM) proteins were immobilized on Difco latex beads to detect these components on the surface of all enterococcal strains and eight non-autoaggregating S. bovis strains by a particle agglutination assay (PAA). Twenty-three selected strains were also examined in microtiter plate assays. According to the absorbance readings (A_570nm), 11 strains were classified as nonadherent (A_570nm < 0.1), 10 strains as weakly adherent (0.1 < A_570nm > 0.3), and 2 strains as strongly adherent (A_570nm > 0.3) in these assays. A direct correlation was found between the values obtained in PAA and A_570nm readings of microtiter plate assays. Binding of ¹²⁵I-labeled bovine lactoferrin to enterococci and streptococci was in the range of 6%–30% and of ¹²⁵I-labeled human vitronectin in the range of 9%–33% to streptococci. The binding of ¹²⁵I-labeled ECM proteins to selected strains was much more effectively inhibited by sulfated carbohydrates than by non-sulfated hyaluronic acid, indicating the importance of the sulfate groups of these inhibitors. An inhibition effect of heparin on bLf binding to four selected strains was higher in comparison with fucoidan in the microtiter plates. Thirty-five out of 44 strains had agglutinated rabbit erythrocytes. However, these strains showed no ability to agglutinate bovine or sheep erythrocytes. Received: 28 April 1999 / Accepted: 26 July 1999     

Protein tyrosine phosphatases and the immune response

Reversible tyrosine phosphorylation of proteins is a key regulatory mechanism for numerous important aspects of eukaryotic physiology and is catalysed by kinases and phosphatases. Together, cells of the immune system express at least half of the 107 protein tyrosine phosphatase (PTP) genes in the human genome, most of which encode multidomain proteins that contain protein- and phospholipid-interaction domains. Here, we discuss the diverse but specific, and important, roles that PTPs have in immune cells, focusing mainly on T and B cells, and we highlight recent evidence that even subtle alterations in PTPs can cause immune dysfunction and human disease.