Foraging under the risk of cannibalism leads to divergence in body size among tiger salamander larvae.

Populations of plants and animals are almost always made up of individuals of different sizes. In populations where cannibalism is common, this size variation can influence rates of mortality and growth and affect population regulation. Size variation can be caused by a variety of mechanisms. One of these is due to size-specific responses to the threat of predation by potentially cannibalistic conspecifics. We investigated the role of anti-predator behavior in size structure development within single-aged cohorts of Arizona tiger salamander larvae. In a laboratory experiment, we show that size variation increases over time within groups of salamanders, even if they are fed in isolation. We also show that increasing the size of neighbors decreases the feeding rate of small salamander larvae. However, increasing density of neighbors did not have a significant effect on feeding rate. These results are consistent with the hypothesis that size variation among tiger salamander larvae is, in part, a result of size-specific responses to predation risk. We discuss the potential for feedback between size structure development, predation risk, and rates of cannibalism.

The role of flow cytometry in the diagnosis of lymphoma: a critical analysis.

Flow cytometry, now used routinely to aid in the classification of leukemias, is increasingly being evaluated as a rapid technique for determination of surface antigens on the cells teased from lymph nodes and other masses with suspected lymphoma. The present study reviews biopsy specimens from patients examined during a two year period which were sent for flow cytometry with a diagnosis of suspected lymphoma. Sixteen of 25 samples (64 percent) produced cell suspensions of sufficient quantity and quality to be diagnostically helpful. Results showed that in 9/16 (56 percent) the diagnosis of lymphoma or cancer could be suspected by flow cytometry alone, while 4/16 were consistent with the final tissue diagnosis of normal or reactive hyperplasia. Three samples that came from patients who had morphologic evidence of malignant disease on biopsy (two Hodgkin's disease and one large cell lymphoma) had flow cytometry results that were interpreted as normal. Flow cytometry is rapid and appears to be virtually diagnostic of non-Hodgkin's lymphoma when a majority of cells are B cells with an abnormal kappa/lambda ratio (> 4.0 or < 0.25). Nonhematologic malignancy can be suspected if less than 75 percent of the cells show CD45 (common leukocyte antigen). Hodgkin's disease cannot be detected by flow cytometry as it is currently used, and as many as 15 percent (1/6 in this study) of lymphomas may show normal results. It is extremely helpful when the biopsy sample actually contains the cells of interest in large proportion. Loss of architectural relationships in the course of processing specimens for flow cytometry is a major disadvantage when small foci of lymphoma or tumor cells exist together with large amounts of stroma or normal lymphocytes.

Live vaccine strain of Francisella tularensis: infection and immunity in mice.

The live vaccine strain (LVS) of Francisella tularensis caused lethal disease in several mouse strains. Lethality depended upon the dose and route of inoculation. The lethal dose for 50% of the mice (LD50) in four of six mouse strains (A/J, BALB/cHSD, C3H/HeNHSD, and SWR/J) given an intraperitoneal (i.p.) inoculation was less than 10 CFU. For the other two strains tested, C3H/HeJ and C57BL/6J, the i.p. log LD50 was 1.5 and 2.7, respectively. Similar susceptibility was observed in mice inoculated by intravenous (i.v.) and intranasal (i.n.) routes: in all cases the LD50 was less than 1,000 CFU. Regardless of the inoculation route (i.p., i.v., or i.n.), bacteria were isolated from spleen, liver, and lungs within 3 days of introduction of bacteria; numbers of bacteria increased in these infected organs over 5 days. In contrast to the other routes of inoculation, mice injected with LVS intradermally (i.d.) survived infection: the LD50 of LVS by this route was much greater than 10(5) CFU. This difference in susceptibility was not due solely to local effects at the dermal site of inoculation, since bacteria were isolated from the spleen, liver, and lungs within 3 days by this route as well. The i.d.-infected mice were immune to an otherwise lethal i.p. challenge with as many as 10(4) CFU, and immunity could be transferred with either serum, whole spleen cells, or nonadherent spleen cells (but not Ig+ cells). A variety of infectious agents induce different disease syndromes depending on the route of entry. Francisella LVS infection in mice provides a model system for analysis of locally induced protective effector mechanisms.