Interaction between cold and altitude exposure on pulmonary circulation of cattle

Circulating Microparticles Are Differentially Increased in Lowlanders and Highlanders with High Altitude Induced Pulmonary Hypertension during the Cold Season

The role of microparticles (MPs) and cold in high altitude pulmonary hypertension (HAPH) remains unexplored. We investigated the impact of long-term cold exposure on the pulmonary circulation in lowlanders and high-altitude natives and the role of MPs. Pulmonary hemodynamics were evaluated using Doppler echocardiography at the end of the colder and warmer seasons. We further examined the miRNA content of MPs isolated from the study participants and studied their effects on human pulmonary artery smooth muscle (hPASMCs) and endothelial cells (hPAECs). Long-term exposure to cold environment was associated with an enhanced pulmonary artery pressure in highlanders. Plasma levels of CD62E-positive and CD68-positive MPs increased in response to cold in lowlanders and HAPH highlanders. The miRNA-210 expression contained in MPs differentially changed in response to cold in lowlanders and highlanders. MPs isolated from lowlanders and highlanders increased proliferation and reduced apoptosis of hPASMCs. Further, MPs isolated from warm-exposed HAPH highlanders and cold-exposed highlanders exerted the most pronounced effects on VEGF expression in hPAECs. We demonstrated that prolonged exposure to cold is associated with elevated pulmonary artery pressures, which are most pronounced in high-altitude residents. Further, the numbers of circulating MPs are differentially increased in lowlanders and HAPH highlanders during the colder season.

An Exaggerated Rise in Pulmonary Artery Pressure in a High-Altitude Dweller during the Cold Season

Chronic hypoxia-induced sustained pulmonary vasoconstriction and vascular remodeling lead to mild-to-moderate elevation of pulmonary artery pressure in high-altitude residents. However, in some of them, severe pulmonary hypertension may develop. Besides hypoxia, high-altitude residents also face other environmental challenges such as low ambient temperatures. We describe a case of a 49-year-old woman of Kyrgyz ethnicity with abnormally increased pulmonary artery pressure, revealed by Doppler echocardiography. Significantly elevated pulmonary artery pressure was detected in late winter and this was not associated with right ventricular hypertrophy or right ventricular dysfunction. Repeat echocardiography performed in late summer disclosed a significant attenuation of pulmonary artery pressure elevation, with no changes in right ventricular performance parameters. This case illustrates that, in susceptible individuals, long-term cold exposure could induce an abnormal pulmonary artery pressure rise, which can be reversed during warm seasons as in our patient. In certain circumstances, however, additional factors could contribute to a sustained pulmonary artery pressure increase and the development of persistent pulmonary hypertension, which often leads to right heart failure and premature death.

Physiological parameter values for physiologically based pharmacokinetic models in food-producing animals. Part I: Cattle and swine

Physiologically based pharmacokinetic (PBPK) models for chemicals in food animals are a useful tool in estimating chemical tissue residues and withdrawal intervals. Physiological parameters such as organ weights and blood flows are an important component of a PBPK model. The objective of this study was to compile PBPK‐related physiological parameter data in food animals, including cattle and swine. Comprehensive literature searches were performed in PubMed, Google Scholar, ScienceDirect, and ProQuest. Relevant literature was reviewed and tables of relevant parameters such as relative organ weights (% of body weight) and relative blood flows (% of cardiac output) were compiled for different production classes of cattle and swine. The mean and standard deviation of each parameter were calculated to characterize their variability and uncertainty and to allow investigators to conduct population PBPK analysis via Monte Carlo simulations. Regression equations using weight or age were created for parameters having sufficient data. These compiled data provide a comprehensive physiological parameter database for developing PBPK models of chemicals in cattle and swine to support animal‐derived food safety assessment. This work also provides a basis to compile data in other food animal species, including goats, sheep, chickens, and turkeys.

Pulmonary Vascular Pressure Response to Acute Cold Exposure in Kyrgyz Highlanders

Background/Aims: Long-term high altitude residence leads to a sustained increase in pulmonary vascular resistance and elevation of pulmonary artery pressure due to chronic alveolar hypoxia. However, living at high altitude is also associated with other environmental factors such as cold. There is still little experimental evidence suggesting detrimental effects of low temperatures on the pulmonary vasculature. Therefore, our objective was to investigate acute effects of cold exposure on the pulmonary circulation in Kyrgyz high altitude natives. Methods: Responses of the pulmonary circulation during acute exposure to controlled cold conditions (4°C-6°C) for 60 minutes were measured in highlanders using Doppler echocardiography. Based on the Doppler echocardiography-derived tricuspid regurgitant systolic pressure gradient (TRG), subjects with TRG ≥40 mmHg were allocated into the pulmonary hypertension (PH) group. Participants from the PH group were compared with volunteer control subjects with TRG <40 mmHg. All baseline measurements were evaluated in a warm room during 60 minutes (22°C-28°C). Following baseline echocardiography, the subjects were assigned to either warm or cold exposure for an additional 60 minutes. Results: Acute cold exposure significantly increased TRG both in the control (ΔTRG, 4.93 mmHg) and in the PH (ΔTRG, 8.15 mmHg) group, compared to the respective warm exposure conditions (ΔTRG, -0.14 and -0.05 mmHg). No changes in cardiac output were observed upon cold exposure. Conclusion: Thus, acute exposure to cold leads to elevation of pulmonary artery pressure in high altitude residents.

The altitude at which a calf is born and raised influences the rate at which mean pulmonary arterial pressure increases with age

Right heart failure secondary to pulmonary hypertension is a leading cause of mortality among suckling beef calves in the Rocky Mountain region. The objective of this study was to track changes in pulmonary arterial pressures (PAP) in healthy calves born and raised at altitudes ranging from 1,470 to 2,730 m. It was hypothesized that calves located at higher altitudes would show a greater increase in mean PAP (mPAP) with age than would be experienced by calves located at lower altitudes. The rationale is that high altitude hypobaric hypoxia causes a greater rate of vascular remodeling and, consequently, greater resistance to blood flow than calves located at lower altitudes. A prospective study was conducted on 5 cohorts of suckling calves from 4 herds located at altitudes of 1,470, 2,010, 2,170, and 2,730 m. In total, 470 PAP measurements were obtained from 258 calves. As hypothesized, calves located at altitudes ≥2,170 m showed a significant increase in mPAP with age ( ≤ 0.002) whereas calves at 1,470 m did not ( = 0.16). Except for calves at 2,170 m ( < 0.001), systolic PAP did not increase with age ( ≥ 0.16). Diastolic PAP increased with age at altitudes ≥ 2,170 m ( ≤ 0.09) but did not change in calves at 1,470 m ( = 0.20). In summary, mPAP and the rate at which mPAP increases with age are positively associated with the altitude at which calves are born and raised.

Time-dependent changes in pulmonary vascular responses to acute hypoxia during and after cold exposure in rats

This study evaluated time-dependent alterations in pulmonary vascular reactivity to acute hypoxia and to the administration of angiotensin II (AT-II) during and after chronic exposure to cold using isolated perfused lung specimens from rats. Animals were exposed to a cold environment (3.5 (mean) +/- 1.0 (SD) degrees C) or to a normal temperature (24.0 +/- 1.0 degrees C) for 7 days. The isolated lungs were taken serially and pulmonary vascular responses to acute hypoxia and AT-II were examined. Both the pulmonary vascular responses to acute hypoxia and to AT-II were significantly reduced 9 h after the exposure to cold. The diminished vascular response to AT-II was restored to the pre-exposure level after 5 days of cold exposure and then sustained. On the other hand, the reduced response to acute hypoxia was sustained for the first 7 days during exposure to cold and then returned to the pre-exposure level during sustained exposure to cold. After removal from the 7 days of cold exposure, the pulmonary vascular response to acute hypoxia was immediately restored. Thus, during exposure to cold, pulmonary vascular response to acute hypoxia was more sustained than the AT-II-induced vasoconstriction. We concluded that cold exposure alters pulmonary vascular responses to acute hypoxia and AT-II in rats, but that the response to acute hypoxia is more sustained than that of AT-II.

Increase of norepinephrine-induced endothelium-dependent relaxation of pulmonary artery in rats after chronic exposure to cold

The present study was designed to determine whether norepinephrine (NE) mediate endothelium-dependent relaxations in arteries of the pulmonary vasculature of cold-acclimated rats. Twenty male Sprague-Dawley rats comprising two groups (Cold-acclimated for 12 weeks at 6°C, CA; Warm-acclimated for 12 weeks at 24 °C, WA) were used. After anesthesia, the pulmonary artery (4 mm long) was isolated. Pulmonary artery with and without endothelium were suspended for isometric force measurements in a buffered salt solution. The doseresponse relations for the vascular responses to the isolated pulmonary artery to norepinephrine (NE), phenylephrine (PE) and acetylcholine (Ach) were determined and compared in the CA group and the WA group. In the CA group, the vascular sensitivities to NE and PE-induced contraction in the pulmonary artery was significantly lowered than that in the WA group. NE and PE-induced contractions were significandy greater in endotheliumdenuded compared with endothelium-intact arteries. These differences of contraction responses to NE and PE between arteries with widiout endothelium were significantly greater in the CA group than in the WA group. There was no significant difference between the pulmonary arterial response to Ach in the CA group and that in the WA group. Our data suggest that chronic exposure to cold show decreased NE and PE-induced contraction responses in isolated pulmonary arteries and may decrease NE-induced contraction responses due to enhancing NE-induced endodielium derived relaxing factor release via up-regulating endothelial α-adrenoceptors.