Ixodes dammini: salivary anaphylatoxin inactivating activity

Saliva of the tick, Ixodes dammini, antagonizes anaphylatoxin, abolishing both the effects of anaphylatoxin on guinea pig ileum preparations regularly stimulated with histamine and the local edema caused by intradermal injection of anaphylatoxin into guinea pigs. Saliva of these ticks, however, did not modify polymorphonuclear leukocyte aggregation induced by anaphylatoxin. Bradykinin and lysil-bradykinin were inactivated, but angiotensin I, angiotensin II, and substance P were not affected. Amino acids were released rapidly following incubation of saliva with bradykinin, but slowly from des-arg-9-bradykinin. These results suggest the presence of a salivary carboxypeptidase with specificity for terminal basic amino acids. Such activity may inactivate anaphylatoxin and bradykinin at the site of tick attachment.     

Characteristics of Garden Dormice That Contribute to Their Capacity as Reservoirs for Lyme Disease Spirochetes

To describe the contribution of garden dormice to the epizootiology of Lyme disease, we compared their reservoir capacity for these pathogens to that of other sympatric hosts. Garden dormice are trapped most abundantly during early spring and again during midsummer, when their offspring forage. They are closely associated with moist forests. Garden dormice serve as hosts to nymphal ticks far more frequently than do other small mammals. Spirochetal infection is most prevalent in dormice, and many more larval ticks acquire infection in the course of feeding on these than on other rodents in the study site. Mature dormice appear to contribute more infections to the vector population than juveniles do. Replete larval ticks generally detach while their dormouse hosts remain within their nests. The population of garden dormice contributes five- to sevenfold more infections to the vector population than the mouse population does. Their competence, nymphal feeding density, and preference for a tick-permissive habitat combine to favor garden dormice over other putative reservoir hosts of Lyme disease spirochetes.     

Bitter taste transduced by PLC-beta(2)-dependent rise in IP(3) and alpha-gustducin-dependent fall in cyclic nucleotides

Current evidence points to the existence of multiple processesfor bitter taste transduction. Previous work demonstrated involvement of the polyphosphoinositide system and an -gustducin(G_gust)-mediated stimulation of phosphodiesterase inbitter taste transduction. Additionally, a taste-enriched G protein-subunit, G₁₃, colocalizes with G_gustand mediates the denatonium-stimulated production of inositol1,4,5-trisphosphate (IP₃). Using quench-flow techniques, weshow here that the bitter stimuli, denatonium and strychnine, inducerapid (50-100 ms) and transient reductions in cAMP and cGMP andincreases in IP₃ in murine taste tissue. This decrease ofcyclic nucleotides is inhibited by G_gust antibodies,whereas the increase in IP₃ is not affected by antibodiesto G_gust. IP₃ production is inhibited byantibodies specific to phospholipase C-₂(PLC-₂), a PLC isoform known to be activated byG-subunits. Antibodies to PLC-₃ or toPLC-₄ were without effect. These data suggest atransduction mechanism for bitter taste involving the rapid andtransient metabolism of dual second messenger systems, both mediatedthrough a taste cell G protein, likely composed ofG_gust//₁₃, with both systems beingsimultaneously activated in the same bitter-sensitive taste receptor cell.

     

Cation Fluxes and Permeability Changes Accompanying Bacteriophage Infection of Escherichia coli

Infection of Escherichia coli by bacteriophage T2 was accompanied by a rapid but transient increase in the rate of loss of small molecules from the bacterial cells. This transient leakage was studied with radioactive labels such as (42)K and (28)Mg. Bacteriophage-induced leakage was dependent on the ratio of phage to bacteria: the higher the multiplicity of infection, the greater the leakage. No leakage occurred at 4 C [when adsorption proceeds but injection of phage deoxyribonucleic acid (DNA) is blocked]. Leakage was caused by heavily irradiated phage as well as by normal phage; therefore, the intracellular functioning of the bacteriophage DNA was not required. This conclusion was supported by experiments which showed phage-induced leakage in the presence of chloramphenicol or sodium cyanide. Leakage could be prevented by infecting the bacteria with phage in the presence of high magnesium concentrations. Phage-induced leakage was terminated by a "sealing" reaction, after which potassium turnover by infected and uninfected cells was very similar. The sealing reaction occurred even in the presence of chloramphenicol, suggesting that the sealing is controlled by bacterial and not bacteriophage genes. We were not able to detect any effect of normal bacteriophage infection on the influx (active transport) of potassium and magnesium into the cells.     

Successive histochemical differentiation steps during postnatal development of the collecting duct in rabbit kidney

Summary Immunohistochemical experiments with monoclonal antibodies (mabs) on the kidney of neonatal rabbits revealed that the primary expression of collecting duct typic structures does not occur in a continuous and parallel, but in a subsequent developmental process. Only mabs RCT-30 A, and CD 4-V revealed immunoreactivity at the ontogenetically oldest parts of the collecting duct, the ampullae, while the other used markers (CD 1–3, CD 5-V, RCT-30 and RMCX) did not. In contrast, all of the tested antibodies showed positive reactions at the medullary and cortical collecting duct of the neonatal kidney as well as of the adult kidney. Additional incubations with wheat-germ agglutinin (WGA) a marker of terminal-differentiated collecting duct cells demonstrated weak-labelled ampulla cells beside intensively labelled ampullary neck and medullary collecting duct cells. With peanut agglutinin (PNA) labelling a 3 step transition could be illuminated: weak-labelled ampulla cells were found beside continuously bright labelled ampullary neck cells and finally a punctuate pattern downwards to the papilla. If the ampullary neck is the zone of proliferation, our findings of WGA- and PNA-co-labelling in this zone indicate, that in early developmental stages characteristic structures of different mature cells, probably principal and intercalated cells, are co-expressed within one single cell type. Thus intercalated cells might derive from principal cells.     

Fluid transport across the ducts of the salivary glands of a mosquito

We compared the volumes of fluid expelled from the salivary stylets of mosquitoes having ducts transected at different levels. An oil-filled apparatus was devised to measure salivary output. About $\text{1}\text{10}$ of normal salivary volume was produced by mosquitoes when ducts were transected and externalized just anterior to the salivary glands. Such mosquitoes ejected more saliva than could be contained within the walls of the ducts. Transection posterior to the pump prevented salivation entirely. Skin reactive antigen was not detected (as a wheal) when mosquitoes with transected ducts fed on man. We conclude that fluid is transported across the walls of the ducts that drain the salivary glands of a mosquito.     

Proliferative phase endosperm promoters from Arabidopsis thaliana

Endosperm accounts for a large proportion of human nutrition and is also a major determinant of seed viability and size, not only in cereals, but also in species with ephemeral endosperms, such as soybean and oilseed rape. The extent of endosperm proliferation early in seed development is a crucial component in setting seed size; therefore, a biotechnological approach for the modification of this trait requires promoters active in early endosperm. To find such promoters, we constructed an array based on cDNAs extracted from developing Arabidopsis seeds enriched for proliferating endosperm. Hybridization with RNA extracted from vegetative and reproductive tissues, including endosperm, and subsequent data filtering yielded sets of endosperm-expressed and endosperm-preferred genes, including many hundreds not previously identified in array experiments designed to detect genes expressed in Arabidopsis seeds. Of eight promoters selected for validation, seven were active in early endosperm, three with no detected activity elsewhere in the plant. Therefore, this strategy has yielded proliferative phase endosperm promoters which should be useful in altering seed size.