A Computer Model of Oxygen Dynamics in the Cortex of the Rat Kidney at the Cell-Tissue Level
INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES
Authors: Aubert, Vivien; Kaminski, Jacques; Guillaud, Francois; Hauet, Thierry; Hannaert, Patrick
Abstract
The renal cortex drives renal function. Hypoxia/reoxygenation are primary factors in ischemia-reperfusion (IR) injuries, but renal oxygenation per se is complex and awaits full elucidation. Few mathematical models address this issue: none captures cortical tissue heterogeneity. Using agent-based modeling, we develop the first model of cortical oxygenation at the cell-tissue level (RCM), based on first principles and careful bibliographical analysis. Entirely parameterized with Rat data, RCM is a morphometrically equivalent 2D-slice of cortical tissue, featuring peritubular capillaries (PTC), tubules and interstitium. It implements hemoglobin/O-2 binding-release, oxygen diffusion, and consumption, as well as capillary and tubular flows. Inputs are renal blood flow RBF and PO2 feeds; output is average tissue PO2 (tPO(2)). After verification and sensitivity analysis, RCM was validated at steady-state (tPO(2) 37.7 +/- 2.2 vs. 36.9 +/- 6 mmHg) and under transients (ischemic oxygen half-time: 4.5 +/- 2.5 vs. 2.3 +/- 0.5 s in situ). Simulations confirm that PO2 is largely independent of RBF, except at low values. They suggest that, at least in the proximal tubule, the luminal flow dominantly contributes to oxygen delivery, while the contribution of capillaries increases under partial ischemia. Before addressing IR-induced injuries, upcoming developments include ATP production, adaptation to minutes-hours scale, and segmental and regional specification.
Influence of Smoking on Thyroid Function in Japanese Subjects: Longitudinal Study for One Year of On-Off Smoking
JOURNAL OF THE ENDOCRINE SOCIETY
Authors: Nakajima, Yasuyo; Yamada, Sayaka; Nishikido, Ayaka; Katano-Toki, Akiko; Ishida, Emi; Akuzawa, Masako; Sakamaki, Koji; Yamada, Eijiro; Saito, Tsugumichi; Ozawa, Atsushi; Okada, Shuichi; Shimomura, Yohnosuke; Kobayashi, Isao; Andou, Yoshitaka; Yamada, Masanobu
Abstract
Context: We previously identified factors affecting thyroid status, including sex, age, and smoking. Objective: In the current study, we increased the number of subjects examined and investigated the effects of these factors, particularly smoking and the thyroid peroxidase antibody (TPO-Ab), in Japanese patients with euthyroxinemia and serum free T4 levels within the normal range. Participants: A total of 12,289 subjects who underwent health checkups were analyzed in a cross-sectional and longitudinal study. Results: The mean age of subjects was 50 +/- 10 years (age range: 21 to 88 years). Serum TSH levels and the prevalence of positivity for TPO-Ab increased with age in Japanese subjects with euthyroxinemia. Mean serum TSH levels were significantly lower in the smoking group than in the nonsmoking group except for women older than 50 years. Serum TSH levels were significantly higher in subjects with positivity for TPO-Ab than in those with negativity at all ages and in both sexes; however, smoking did not affect free T4 levels or positivity for TPO-Ab. Among men, the rate of smokers was significantly higher in patients with subclinical hyperthyroidism (25%) than in those with subclinical hypothyroidism (10%; P < 0.05). Furthermore, the results of the longitudinal study revealed a significant decrease in serum TSH levels 1 year after the start of smoking in men (P < 0.05). Conclusion: Because smoking appeared to lower serum TSH levels in Japanese subjects with euthyroxinemia, their smoking status warrants careful consideration when evaluating subclinical thyroid function. Copyright (C) 2019 Endocrine Society