Hypothermia Improves Oral and Gastric Mucosal Microvascular Oxygenation during Hemorrhagic Shock in Dogs

Hypothermia is known to improve tissue function in different organs during physiological and pathological conditions. The aim of this study was to evaluate the effects of hypothermia on oral and gastric mucosal microvascular oxygenation (μHbO2) and perfusion (μflow) under physiological and hemorrhagic conditions. Five dogs were repeatedly anesthetized. All animals underwent each experimental protocol (randomized cross-over design): hypothermia (34°C), hypothermia during hemorrhage, normothermia, and normothermia during hemorrhage. Microcirculatory and hemodynamic variables were recorded. Systemic (DO2) and oral mucosal (μDO2) oxygen delivery were calculated. Hypothermia increased oral μHbO2 with no effect on gastric μHbO2. Hemorrhage reduced oral and gastric μHbO2 during normothermia (−36 ± 4% and −27 ± 7%); however, this effect was attenuated during additional hypothermia (−15 ± 5% and −11 ± 5%). The improved μHbO2 might be based on an attenuated reduction in μflow during hemorrhage and additional hypothermia (−51 ± 21 aU) compared to hemorrhage and normothermia (−106 ± 19 aU). μDO2 was accordingly attenuated under hypothermia during hemorrhage whereas DO2 did not change. Thus, in this study hypothermia alone improves oral μHbO2 and attenuates the effects of hemorrhage on oral and gastric μHbO2. This effect seems to be mediated by an increased μDO2 on the basis of increased μflow

PTRH2 is Necessary for Purkinje Cell Differentiation and Survival and its Loss Recapitulates Progressive Cerebellar Atrophy and Ataxia Seen in IMNEPD Patients

Hom ozygous variants in the peptidyl-tRNA hydrolase 2 gene (PTRH2) cause infantile-onset multisystem neurologic, endocrine, and pancreatic disease. The objective is to delineate the mechanisms underlying the core cerebellar phenotype in this disease. For this, we generated constitutive (Ptrh2LoxPxhCMVCre, Ptrh2−/− mice) and Purkinje cell (PC) specific (Ptrh2LoxPxPcp2Cre, Ptrh2ΔPCmice) Ptrh2 mutant mouse models and investigated the effect of the loss of Ptrh2 on cerebellar development. We show that Ptrh2−/− knockout mice had severe postnatal runting and lethality by postnatal day 14. Ptrh2ΔPC PC specific knockout mice survived until adult age; however, they showed progressive cerebellar atrophy and functional cerebellar deficits with abnormal gait and ataxia. PCs of Ptrh2ΔPC mice had reduced cell size and density, stunted dendrites, and lower levels of ribosomal protein S6, a readout of the mammalian target of rapamycin pathway. By adulthood, there was a marked loss of PCs. Thus, we identify a cell autonomous requirement for PTRH2 in PC maturation and survival. Loss of PTRH2 in PCs leads to downregulation of the mTOR pathway and PC atrophy. This suggests a molecular mechanism underlying the ataxia and cerebellar atrophy seen in patients with PTRH2 mutations leading to infantile-onset multisystem neurologic, endocrine, and pancreatic disease

Sub-therapeutic vasopressin but not therapeutic vasopressin improves gastrointestinal microcirculation in septic rats: A randomized, placebo-controlled, blinded trial

Introduction Sepsis impairs gastrointestinal microcirculation and it is hypothesized that this might increase patient’s mortality. Sub-therapeutic vasopressin improves gastric microcirculation under physiologic conditions whereas a therapeutic dosing regimen seems to be rather detrimental. However, the effects of sub-therapeutic vasopressin on gastrointestinal microcirculation in sepsis are largely unknown. Therefore, we conducted this trial to investigate the effect of sub-therapeutic as well as therapeutic vasopressin on gastrointestinal microcirculation in sepsis. Methods 40 male Wistar rats were randomized into 4 groups. Colon ascendens stent peritonitis (CASP)-surgery was performed to establish mild or moderate sepsis. 24 hours after surgery, animals received either vasopressin with increasing dosages every 30 min (6.75, 13.5 (sub-therapeutic), 27 mU · kg-1 · h-1 (therapeutic)) or vehicle. Microcirculatory oxygenation (μHBO2) of the colon was recorded for 90 min using tissue reflectance spectrophotometry. Intestinal microcirculatory perfusion (total vessel density (TVD; mm/mm2) and perfused vessel density (PVD; mm/mm2)) were measured using incident dark field-Imaging at baseline and after 60 min. Results In mild as well as in moderate septic animals with vehicle-infusion intestinal μHbO2, TVD and PVD remained constant. In contrast, in moderate sepsis, sub-therapeutic vasopressin with 13.5 mU · kg-1 · h-1 elevated intestinal μHBO2 (+ 6.1 ± 5.3%; p &lt; 0.05 vs. baseline) and TVD (+ 5.2 ± 3.0 mm/mm2; p &lt; 0.05 vs. baseline). μHBO2, TVD and PVD were significantly increased compared to moderate sepsis alone. However, therapeutic vasopressin did not change intestinal microcirculation. In mild septic animals sub-therapeutic as well as therapeutic vasopressin had no relevant effect on gastrointestinal microcirculation. Systemic blood pressure remained constant in all groups. Conclusion Sub-therapeutic vasopressin improves gastrointestinal microcirculatory oxygenation in moderate sepsis without altering systemic blood pressure. This protective effect seems to be mediated by an enhanced microcirculatory perfusion and thereby increased oxygen supply. In contrast, therapeutic vasopressin did not show this beneficial effect. </jats:sec

Vasopressin V1A receptors mediate the increase in gastric mucosal oxygenation during hypercapnia

Hypercapnia (HC) improves systemic oxygen delivery (DO2) and microvascular hemoglobin oxygenation of the mucosa (μHbO2). Simultaneously, HC increases plasma levels of vasopressin. Although vasopressin is generally regarded a potent vasoconstrictor particularly in the splanchnic region, its effects on splanchnic microcirculation during HC is unclear. The aim of this study was to evaluate the role of endogenous vasopressin on gastric mucosal oxygenation and hemodynamic variables during physiological (normocapnia) and hypercapnic conditions. Five dogs were repeatedly anesthetized to study the effect of vasopressin V1A receptor blockade ([Pmp1,Tyr(Me)2]-Arg8-Vasopressin, 35 μg/kg) on hemodynamic variables and μHbO2 during normocapnia or HC (end-tidal CO2 70 mmHg). In a control group, animals were subjected to HC alone. μHbO2 was measured by reflectance spectrophotometry, systemic DO2 was calculated from intermittent blood gas analysis, and cardiac output was measured by transpulmonary thermodilution. Data are presented as mean±s.e.m. for n=5 animals. During HC alone, DO2 increased from 12±1 to 16±1 ml/kg per min and μHbO2 from 70±4 to 80±2%. By contrast, additional vasopressin V1A receptor blockade abolished the increase in μHbO2 (80±2 vs 69±2%) without altering the increase in DO2 (16±1 vs 19±2 ml/kg per min). Vasopressin V1A receptor blockade (VB) during normocapnia neither affected DO2 (13±1 vs 14±1 ml/kg per min) nor μHbO2 (75±3 vs 71±5%). Vasopressin V1A receptor blockade abolished the increase in μHbO2 during HC independent of DO2. Thus, in contrast to its generally vasoconstrictive properties, the vasopressin V1A receptors seem to mediate the increase in gastric microcirculatory mucosal oxygenation induced by acute HC.</jats:p