ABSTRACT
To demarcate the limits of experimental knowledge, we probe the limits of what might be called an experiment. By appeal to examples of scientific practice from astrophysics and analogue gravity, we demonstrate that the reliability of knowledge regarding certain phenomena gained from an experiment is not circumscribed by the manipulability or accessibility of the target phenomena. Rather, the limits of experimental knowledge are set by the extent to which strategies for what we call 'inductive triangulation' are available: that is, the validation of the mode of inductive reasoning involved in the source-target inference via appeal to one or more distinct and independent modes of inductive reasoning. When such strategies are able to partially mitigate reasonable doubt, we can take a theory regarding the phenomena to be well supported by experiment. When such strategies are able to fully mitigate reasonable doubt, we can take a theory regarding the phenomena to be established by experiment. There are good reasons to expect the next generation of analogue experiments to provide genuine knowledge of unmanipulable and inaccessible phenomena such that the relevant theories can be understood as well supported. This article is part of a discussion meeting issue 'The next generation of analogue gravity experiments'.
ABSTRACT
Splenocytes from prediabetic female NOD mice can transfer diabetes to NOD-SCID mice. Whereas the kinetics of disease transfer was shown to be a function of the age of donor splenocytes, information is scarce as to how the stage of autoimmune disease, as evaluated by pancreatic insulin content, is related to the diabetogenic potency of splenic T-cells. We therefore determined individual diabetes transfer times after an i. v. injection of splenocytes from prediabetic NOD mice of different ages into female NOD-SCID mice in relation to the diabetes incidence in NOD donor mice and their pancreatic insulin contents. Three groups (n = 8) of NOD mice aged 5, 11, and 17 weeks (wk) underwent splenectomy and hemipancreatectomy. After that, 10x10 (6) splenocytes either pooled from all donor NOD mice of the different age groups or individually from single donor mice were transferred to groups of four 6-week-old NOD-SCID mice, respectively, in two sets of experiments. Insulin was extracted from the resected hemipancreas, and the insulin content was determined by a RIA. Diabetes in the NOD-SCID cohort occurred after a mean time of 126 days after transfer of pooled splenocytes from 5-week-old NODs, after 68 days (transfer from 11-week-old NODs), and after a mean time of 43 days (transfer from 17-week-old NODs, 5 vs. 11 wk: p < 0.02, 11 vs. 17 wk: p < 0.001). Individual time to diabetes positively correlated with diabetes transfer times in NOD-SCID recipients (p < 0.0001) in the 17-week-old NOD mice, confirming previous diabetes transfer studies in hemi-pancreatectomized NOD mice. Furthermore, individual insulin concentrations in 17-week-old NOD mice also positively correlated to diabetes transfer times in recipient mice (p < 0.0001). No such correlations for these parameters were seen for the 5 and 11-week-old NOD mice (time to diabetes: 11 wk, p = 0.14, 5 wk, p = 0.75; insulin content: 11 wk, p = 0.81, 5 wk, p = 0.14). These data suggest that destructive T-cell activity increases during the course of islet autoimmunity. The immune response seems to be programmed for beta-cell destruction just before diabetes onset. This is the only time that pancreatic insulin content predicts the impending onset of diabetes.