Helicobacter pylori is involved in gastritis, gastric and duodenal ulcers, gastric adenocarcinoma, and mucosaassociated lymphoid tissue lymphoma. Earlier studies already suggested a role for autoimmune phenomena in H. pylori-linked disease. We now report that lipopolysaccharides (LPS) of H. pylori express Lewis y, Lewis x, and H type I blood group structures similar to those commonly occurring in gastric mucosa. Immunization of mice and rabbits with H. pylori cells or purified LPS induced an anti-Lewis x or y or anti-H type I response, yielding antibodies that bound human and murine gastric glandular tissue, granulocytes, adenocarcinoma, and mucosa-associated lymphoid tissue lymphoma cells. Experimental oral infections in mice or natural infection in humans yielded anti-Lewis antibodies also. The  chain of gastric H ؉ ,K ؉ -ATPase, the parietal cell proton pump involved in acid secretion, contained Lewis y epitopes; gastric mucin contained Lewis x and y antigenic determinants. Growth in mice of a hybridoma that secretes H. pylori-induced anti-Lewis y monoclonal antibodies resulted in histopathological evidence of gastritis, which indicates a direct pathogenic role for anti-Lewis antibodies. In conclusion, our observations demonstrate that molecular mimicry between H. pylori LPS and the host, based on Lewis antigens, and provide understanding of an autoimmune mechanism for H. pylori-associated type B gastritis.
Pollen is an important vector of gene flow in maize (Zea mays L.). Experiments were conducted to investigate the duration of pollen viability and the effectiveness of isolation distance for controlling gene flow. Pollen longevity was tested by collecting pollen at dehiscence and exposing it in a thin layer in the open air and sunshine for prescribed time periods before assessing pollen viability by measuring seed set after pollination and scoring visual appearance. Isolation distance efficacy was evaluated by growing 12.8‐m2 plot of maize at various distances from a 4000‐m2 pollen source. The pollinator contained either a genetic leaf or seed marker that allowed pollen flow to be measured. Pollen maintained viability for 1 to 2 h after dehiscence depending on atmospheric water potential. The theoretical, maximum distance viable pollen could move was 32 km, assuming pollen was transported linearly at the maximum average afternoon windspeeds for our location, viability was maintained for 2 h, and pollen settling rate was ignored. Cross pollinations occurred at a maximum distance of 200 m from the source planting, and only a limited number of cross pollinations occurred at the shortest distance (100 m). No cross pollinations occurred at 300 m from the source planting. The results are consistent with conclusions that maize pollen is desiccation intolerant and has a high settling rate. The results indicate isolation distance can be a useful tool for controlling gene flow via pollination in research scale plantings.
In addition to the major encapsidated DNA species found in preparations of cassava latent virus (genomic DNAs 1 and 2) there are minor DNA populations of twice (dimeric) and approximately half genome length. Both minor species resemble the genomic DNAs in that they are composed of predominantly circular single-stranded DNA. All of these size groups have a corresponding covalently-closed circular double-stranded DNA form in infected tissue. Infectivity studies using cloned DNAs 1 and 2 show that dimeric DNA routinely appears, suggesting it to be an intermediate in the DNA replicative cycle that can be encapsidated at low efficiency. In contrast, half unit length DNA has not yet been detected after multiple passaging of virus derived from the cloned DNA inoculum. Half unit length DNAs appear to be derived exclusively from DNA 2 and consist of a population of molecules exhibiting a relatively specific deletion. As they have an inhibitory effect on virus multiplication, their encapsidated forms are analogous to defective interfering particles associated with other eukaryotic DNA containing viruses. Small primer molecules associated with the genomic single-stranded DNAs, as reported for another geminivirus, have not been detected in CLV.
The nucleotide sequences of infectious cloned DNAs 1 and 2 of a Kenyan isolate of cassava latent virus (CLV) have been determined. Five virus‐specific polyadenylated transcripts have been identified and mapped either to the viral or complementary sense DNAs of both components of the CLV genome, confirming that transcription is bidirectional on both DNAs. A major mRNA has been translated in vitro to yield a 30 000 mol. wt. product, which is precipitated by antibodies raised against whole virus, and has been mapped by both the S1 nuclease procedure and hybrid‐arrested translation to the long open reading frame (ORF) in the viral sense of DNA 1 which encodes the coat protein. Other transcripts were of sufficient size and appropriate origin to encode at least five potential products.
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