Biomedical subjects

Daniel Long

Publications and source records attributed to Daniel Long.

4 recordsLinked to original sources

PubMed2006

Role of the Yersinia pestis plasminogen activator in the incidence of distinct septicemic and bubonic forms of flea-borne plague.

Yersinia pestis is transmitted by fleas and causes bubonic plague, characterized by severe local lymphadenitis that progresses rapidly to systemic infection and life-threatening septicemia. Here, we show that although flea-borne transmission usually leads to bubonic plague in mice, it can also lead to primary septicemic plague. However, intradermal injection of Y. pestis, commonly used to mimic transmission by fleabite, leads only to bubonic plague. A Y. pestis strain lacking the plasmid-encoded cell-surface plasminogen activator, which is avirulent by intradermal or s.c. injection, was able to cause fatal primary septicemic plague at low incidence, but not bubonic plague, when transmitted by fleas. The results clarify a long-standing uncertainty about the etiology of primary septicemic plague and support an evolutionary scenario in which plague first emerged as a flea-borne septicemic disease of limited transmissibility. Subsequent acquisition of the plasminogen activator gene by horizontal transfer enabled the bubonic form of disease and increased the potential for epidemic spread.

Animals↗

PubMed2006

Yersinia pestis YopJ suppresses tumor necrosis factor alpha induction and contributes to apoptosis of immune cells in the lymph node but is not required for virulence in a rat model of bubonic plague.

The virulence of the pathogenic Yersinia species depends on a plasmid-encoded type III secretion system that transfers six Yop effector proteins into host cells. One of these proteins, YopJ, has been shown to disrupt host cell signaling pathways involved in proinflammatory cytokine production and to induce macrophage apoptosis in vitro. YopJ-dependent apoptosis in mesenteric lymph nodes has also been demonstrated in a mouse model of Yersinia pseudotuberculosis infection. These results suggest that YopJ attenuates the host innate and adaptive immune response during infection, but the role of YopJ during bubonic plague has not been completely established. We evaluated the role of Yersinia pestis YopJ in a rat model of bubonic plague following intradermal infection with a fully virulent Y. pestis strain and an isogenic yopJ mutant. Deletion of yopJ resulted in a twofold decrease in the number of apoptotic immune cells in the bubo and a threefold increase in serum tumor necrosis factor alpha levels but did not result in decreased virulence, systemic spread, or colonization levels in the spleen and blood. Our results indicate that YopJ is not essential for bubonic plague pathogenesis, even after peripheral inoculation of low doses of Y. pestis. Instead, the effects of YopJ appear to overlap and augment the immunomodulatory effects of other Y. pestis virulence factors.

Animals↗

PubMed2005

Kinetics of disease progression and host response in a rat model of bubonic plague.

Plague, caused by the gram-negative bacterium Yersinia pestis, primarily affects rodents but is also an important zoonotic disease of humans. Bubonic plague in humans follows transmission by infected fleas and is characterized by an acute, necrotizing lymphadenitis in the regional lymph nodes that drain the intradermal flea bite site. Septicemia rapidly follows with spread to spleen, liver, and other organs. We developed a model of bubonic plague using the inbred Brown Norway strain of Rattus norvegicus to characterize the progression and kinetics of infection and the host immune response after intradermal inoculation of Y. pestis. The clinical signs and pathology in the rat closely resembled descriptions of human bubonic plague. The bacteriology; histopathology; host cellular response in infected lymph nodes, blood, and spleen; and serum cytokine levels were analyzed at various times after infection to determine the kinetics and route of disease progression and to evaluate hypothesized Y. pestis pathogenic mechanisms. Understanding disease progression in this rat infection model should facilitate further investigations into the molecular pathogenesis of bubonic plague and the immune response to Y. pestis at different stages of the disease.

Animals↗

PubMed2002

Anthropometric differences among occupational groups.

The increasing demands for anthropometric information for the design of machinery and personal protective equipment to prevent occupational injuries has necessitated an understanding of the anthropometric differences to be found among occupations. This study identified differences in various body measurements between occupational groups in the USA, as determined in the third National Health and Nutrition Examination Survey. Approximately 16,000 of its 32,900 subjects were associated with an occupational group. The analysis of the data showed that the body size, or body segment measurements, of some occupational groups differ significantly. For example, agricultural workers were shorter by an average of 2.5 cm in height, and had wider wrist breadths, than other workers. Female agricultural and manufacturing workers had larger waist circumferences than those in the 'other occupations' and 'all occupations' categories. Protective service workers (i.e. firefighters, police and guards) were taller and heavier (7 kg heavier for males and over 10 kg heavier for females) than those in all occupations combined. These differences and other deviations as well as some age-and-ethnicity-adjusted results were tabulated for users' reference. Researchers and designers who use anthropometric databases to evaluate human-machine interfaces and personal protective equipment (PPE) must use caution in selecting databases that are adequate for their occupational applications.

Anthropometry↗