Load-Bearing

This is a population-based follow-up study of two low birth weight groups and a control group, all born between 1986 and 1988. One group was born preterm with very low birth weight (VLBW, birth weight: ≤ 1500 g) and the other was born small for gestational age (SGA) at term (birth weight < 10th percentile adjusted for gestational age (GA), sex and parity). The controls were born at term (birth weight ≥ 10th percentile, adjusted for GA, sex and parity).
During the enrolment period, all VLBW participants were admitted to the referral neonatal intensive care unit for the counties of North and South Trøndelag at The University Hospital in Trondheim, Norway. In the same period, the SGA and control participants were enrolled as part of a multicenter study comprising participants from Uppsala, Sweden, and Trondheim and Bergen, Norway [28 (link)]. A 10% random sample of women was selected for follow-up during pregnancy. At birth, all children of mothers in the random sample and all children born SGA in the nonrandom sample were included for follow-up. Of these, only SGA and control participants recruited in Trondheim were included in the present study. Data were collected between autumn 2006 and autumn 2008.

Weight-stable, tumor-bearing male KPC mice with tumors of 3-5 mm size and no evidence of obstructive common bowel duct, and their respective weight- and age-matched control counterparts (PC mice) were enrolled in the experiments.
Weight-stable wild-type 9-weeks old male BALB/c mice were inoculated with 2x10⁶ viable C26 colorectal cancer cells subcutaneously (s.c.) and enrolled on study together with their respective controls.
At day of enrolment (day 14 post-injection of C26 cells), mice were stratified in terms of tumor size, body weight and age, singly-housed and randomly allocated into two experimental matched groups fed with different diets: mice were fed with either standard diet (#5053 PicoLab^® Rodent Diet 20; LabDiet) or ketogenic diet (KD) (#F3666; Bio-Serv). Ketogenic diet was given in a Petri dish container that was replaced daily due to potential oxidation of the diet.

The measuring device was inspired by a device proposed by Chuong and Fung^{21 (link)} who used it for radial compression tests. We propose some modifications, however. The biggest change being that we chose a force driven setup instead of a displacement driven one. That allows the thickness at the measuring location to be measured under constant acting force. The experimental stand consists of seven main parts (Fig. 2). (a) A rigid stand ensuring a fixed position in relation to the body of the measuring machine. (b) The body of the measuring machines is designed so that there is no deformation during loading and therefore no measurement distortion. Further, it contains enough space below the measurement area to accommodate a camera. That is useful for checking planarity and parallelism of both surfaces (here performed via photo of a squeezed drop of stained water). (c) Guide pivot ensuring pure axial movement. (d) Laser meter optoNCDT 1420-50 (Micro-Epsilon, Czech Republic) with an accuracy of ± 2 μm. (e) System of weights with total mass (including the base weight) of 2798.78 g. The variance of weights mass $m_i$ is from 46.99 g to 262.4 g. The weights were made of steel sheets with a variance of thicknesses from 0.5 to 5 mm. The weight of the individual weights was determined using an ABS320-4N (range 320 g, Kern & Sohn, Germany) laboratory scale with an accuracy of ± 0.2 mg. The mass of individual weights was written on them to avoid confusion. (f) The base weight lying on a specimen of soft tissue. The base weight consists of an aluminum plate and two linear bearings made of PTFE (colored purple in Fig. 2). Base weight mass including the bearings was 50.31 g ( $m_{\mathit{eff}})$ and its dimensions 80 × 50 mm ensured the specimen was always fully covered by it. Parallelism between base glass and base weight was verified during stand assembling via photo of a squeezed drop of stained water and was below 0.02 mm which is considered fully sufficient. (g) The 4 mm thick base glass. It is important to stress that the direct laser measurement of soft tissue thickness is unreliable^{15 (link)}. Therefore we always measured the position of the top surface of the base weight instead. That is why there are holes in the additional weights (marked green in Fig. 2) so the laser beam always reflects from the top surface of the base weight.Figure 2

The experimental stand used in the study. It has seven major parts. (a) laser holder, (b) measuring device body, (c) guide pivot, (d) laser meter, (e) system of weights, (f) base weight with slide bearings, (g) basic glass. Item (h) is the tissue sample.

Finally, it is noted the used base weight mass is an effective mass which means we compensated for bearings friction forces reducing the forces acting on the specimen. A spring with known stiffness k = 0.62 N/mm (measured on classical tensile test machine with 100 N load cell) was placed between the base glass and base weight. Gross base weight mass of $m=57.88g$ should compress the spring by $w=m·\frac{g}{k}=$ 0.92 mm ( $g$ stands for gravity constant), while we repeatedly (5 times) measured compression of $0.80\mathrm{mm}\pm 0.06\mathrm{mm}$ . This reduced compression was recalculated into the effective base weight mass of $m_{\mathit{eff}}=50.31g\pm 3.94g$ ; this value was used in all the consequent analyses. It is underlined this analysis should be always performed when the stand is assembled to check the parallelism of guiding pivots and the influence of friction.