PubMed Health⌕ Search

Biomedical subjects

David Sibley

Publications and source records attributed to David Sibley.

4 recordsLinked to original sources

Intestinal spirochetosis: a poorly understood infection causing chronic diarrhea.

A young man with chronic diarrhea for many years underwent extensive evaluation. Finally, based on multiple colonic mucosal biopsies from near-normal appearing mucosa, the cause was elucidated to be spirochetosis. This is an enigmatic condition where the spirochetes seem to attach to the epithelial lining of the small and large bowel, without significant underlying inflammation. Because of this reason, there is controversy whether it is a true diarrheal pathogen. Suggested treatments are discussed.

Anti-Infective Agents↗

Role of cytokines and major histocompatibility complex restriction in mouse resistance to infection with a natural recombinant strain (type I-III) of Toxoplasma gondii.

Herein we characterized various genetic markers and the biological behavior of a natural recombinant strain of Toxoplasma gondii (P-Br). From nine genetic markers analyzed, three (B1, ROP1, and SAG1) and three (cS10-A6, GRA6, and SAG3) markers belong to parasites from the type I and type III lineages, respectively. The SAG2 and L363 loci were shown to be type I-III chimera alleles. The cB2l-4 microsatellite marker showed a unique haplotype. The P-Br strain presented low virulence in the acute phase of infection and was cystogenic during the chronic infection. The interleukin 12/gamma interferon axis and inducible nitric oxide synthase were main determinants of resistance during the acute infection with the P-Br strain. As opposed to infection with the type II strain of T. gondii (ME-49), peroral infection with the P-Br strain led only to a light inflammatory infiltrate and no major lesions in the intestine of the C57BL/6 mice. In addition, the BALB/c (resistant to ME-49) and C57BL/6 (susceptible to ME-49) mice were shown, respectively, to be more susceptible and more resistant to cyst formation and toxoplasmic encephalitis when infected with the P-Br strain. Further, the C57BL/KsJ and DBA2/J congenic strains containing major histocompatibility complex (MHC) haplotype "d" were more resistant than the parental strains (C57BL/6 and DBA1/J), when infected with the ME-49 but not with the P-Br strain. Together, our results indicate that resistance to cyst formation and toxoplasmic encephalitis induced during infection with P-Br is not primarily controlled by the MHC haplotype d, as previously reported for type II strains of T. gondii.

Animals↗

Spotting patterns on the fly.

Recognizing and anticipating change in industry patterns is a core competence for companies today, allowing managers to capitalize on opportunities before they are apparent to others. Yet despite the growing realization that recognizing patterns is important, companies are far from mastering how to do it, especially at the strategic level, where information is usually less profuse and much less precise. Pattern recognition is not a new skill, though, at least not to people outside the business world. Since antiquity, naturalists have relied on their ability to spot patterns to make sense of their surroundings. And surprisingly, there is much businesspeople can learn from bird-watching--as removed as it may seem from the fast-paced, bruising world of business--in terms of the cognitive demands pattern recognition requires. To learn more, HBR spoke with David Sibley, perhaps the nation's foremost birdwatcher and illustrator, and Julia Yoshida, a birder since 1965 and a physician at the Lahey Clinic in Burlington, Massachusetts. Sibley explains how expert birders draw on a wealth of tacit knowledge built up over the years to make identifications in a matter of seconds: "Once you've mastered common patterns, the real trick is to educate yourself about where discrepancies are most likely to appear--and to concentrate your attention on those areas." Although so fast as to be almost unconscious, the process he describes seems to be as methodical as one of Yoshida's medical diagnoses. "Recognizing a pattern involves knowing what to look for, what the possibilities are, and then sorting out those patterns when you are actually confronted with the patient," Yoshida says. "I don't think it's a eureka moment at all. It's a methodical process."

Administrative Personnel↗