Presence of procoagulant peripheral blood mononuclear cells in severe COVID-19 patients relate to ventilation perfusion mismatch and precede pulmonary embolism.

PURPOSE: Pulmonary emboli (PE) contribute substantially to coronavirus disease 2019 (COVID-19) related mortality and morbidity. Immune cell-mediated hyperinflammation drives the procoagulant state in COVID-19 patients, resulting in immunothrombosis. To study the role of peripheral blood mononuclear cells (PBMC) in the procoagulant state of COVID-19 patients, we performed a functional bioassay and related outcomes to the occurrence of PE. Secondary aims were to relate this functional assay to plasma D-dimer levels, ventilation perfusion mismatch and TF expression on monocyte subsets. METHODS: PBMC from an ICU biobank were obtained from 20 patients with a computed tomography angiograph (CTA) proven PE and compared to 15 COVID-19 controls without a proven PE. Functional procoagulant properties of PBMC were measured using a modified fibrin generation time (MC-FGT) assay. Tissue factor (TF) expression on monocyte subsets were measured by flow cytometry. Additional clinical data were obtained from patient records including end-tidal to arterial carbon dioxide gradient. RESULTS: MC-FGT levels were highest in the samples taken closest to the PE detection, similar to the end-tidal to arterial carbon dioxide gradient (ETCO2 - PaCO2), a measurement to quantify ventilation-perfusion mismatch. In patients without proven PE, peak MC-FGT relates to an increase in end-tidal to arterial carbon dioxide gradient. We identified non-classical, CD16 positive monocytes as the subset with increased TF expression. CONCLUSION: We show that the procoagulant state of PBMC could aid in early detection of PE in COVID-19 ICU patients. Combined with end-tidal to ETCO2 - PaCO2 gradient, these tests could improve early detection of PE on the ICU.

Animal and translational models of SARS-CoV-2 infection and COVID-19.

COVID-19 is causing a major once-in-a-century global pandemic. The scientific and clinical community is in a race to define and develop effective preventions and treatments. The major features of disease are described but clinical trials have been hampered by competing interests, small scale, lack of defined patient cohorts and defined readouts. What is needed now is head-to-head comparison of existing drugs, testing of safety including in the background of predisposing chronic diseases, and the development of new and targeted preventions and treatments. This is most efficiently achieved using representative animal models of primary infection including in the background of chronic disease with validation of findings in primary human cells and tissues. We explore and discuss the diverse animal, cell and tissue models that are being used and developed and collectively recapitulate many critical aspects of disease manifestation in humans to develop and test new preventions and treatments.

Tissue-specific regulation of mitochondrial and cytoplasmic protein synthesis rates by insulin.

In vivo studies have reported conflicting effects of insulin on mixed tissue protein synthesis rates. To test the hypothesis that insulin has differential effects on synthesis rates of various protein fractions in different organs, we infused miniature swine (n = 8 per group) with saline, insulin alone (at 0.7 mU/kg(-1). min(-1)), or insulin plus an amino acid mixture for 8 h. Fractional synthesis rate (FSR) of mitochondrial and cytoplasmic proteins in liver, heart, and skeletal muscle, as well as myosin heavy chain (MHC) in muscle, were measured using L-[1-(13)C]leucine as a tracer. The FSR of mitochondrial and cytoplasmic proteins were highest in liver, followed by heart and then muscle. Mitochondrial FSR in muscle was higher during insulin and insulin plus amino acid infusions than during saline. Insulin had no significant effect on FSR of MHC in muscle. In contrast, FSR of both mitochondrial and cytoplasmic proteins were not stimulated by insulin in liver. Insulin also did not increase FSR of mitochondrial in heart, whereas insulin and amino acid stimulated FSR of cytoplasmic protein. In conclusion, insulin stimulates the synthesis of muscle mitochondrial proteins, with no significant stimulatory effect on synthesis of sarcoplasmic and MHC. These results demonstrate that insulin has different effects on synthesis rates of specific protein fractions in the liver, heart, and skeletal muscle.

Evaluation of DXA vs. MRI for body composition measures in 1-month olds.

BACKGROUND: Detailed measures of infant body composition are needed for understanding the impact of genes and environment on growth early in life. OBJECTIVE: The purpose of this study was to compare the accuracy and bias of body composition in infants. METHODS: Dual energy X-ray absorptiometry (DXA) and magnetic resonance imaging (MRI) were used to determine body composition and the trunk depot. The depots measured were total fat mass (FM), total fat-free mass (FFM) and trunk FM and FFM using DXA and MRI in 14 infants. RESULTS: None of the regression lines between DXA and MRI significantly deviate from the line of identity for any of the depots studied. However, Bland-Altman analyses revealed bias for trunk FM and trunk FFM. CONCLUSION: Our data showed DXA to be accurate (regression not significantly deviating from the line of identity), with high agreement (indicated by high R(2) ) and without bias (non-significant Bland-Altman) when estimating total FM and FFM. This could not be said for trunk estimates.

Excess postexercise oxygen consumption and recovery rate in trained and untrained subjects.

The purpose of this study was to determine whether aerobic fitness level would influence measurements of excess postexercise oxygen consumption (EPOC) and initial rate of recovery. Twelve trained [Tr; peak oxygen consumption (VO2 peak) = 53.3 +/- 6.4 ml . kg-1 . min-1] and ten untrained (UT; VO2 peak = 37.4 +/- 3.2 ml . kg-1 . min-1) subjects completed two 30-min cycle ergometer tests on separate days in the morning, after a 12-h fast and an abstinence from vigorous activity of 24 h. Baseline metabolic rate was established during the last 10 min of a 30-min seated preexercise rest period. Exercise workloads were manipulated so that they elicited the same relative, 70% VO2 peak (W70%), or the same absolute, 1.5 l/min oxygen uptake (VO2) (W1.5), intensity for all subjects, respectively. Recovery VO2, heart rate (HR), and respiratory exchange ratio (RER) were monitored in a seated position until baseline VO2 was reestablished. Under both exercise conditions, Tr had shorter EPOC duration (W70% = 40 +/- 15 min, W1.5 = 21 +/- 9 min) than UT (W70% = 50 +/- 14 min; W1.5 = 39 +/- 14 min), but EPOC magnitude (Tr: W70% = 3.2 +/- 1.0 liters O2, W1.5 = 1.5 +/- 0.6 liters O2; UT: W70% = 3.5 +/- 0.9 liters O2, W1.5 = 2.4 +/- 0.6 liters O2) was not different between groups. The similarity of Tr and UT EPOC accumulation in the W70% trial is attributed to the parallel decline in absolute VO2 during most of the initial recovery period. Tr subjects had faster relative decline during the fast-recovery phase, however, when a correction for their higher exercise VO2 was taken. Postexercise VO2 was lower for Tr group for nearly all of the W1.5 trial and particularly during the fast phase. Recovery HR kinetics were remarkably similar for both groups in W70%, but recovery was faster for Tr during W1.5. RER values were at or below baseline throughout much of the recovery period in both groups, with UT experiencing larger changes than Tr in both trials. These findings indicate that Tr individuals have faster regulation of postexercise metabolism when exercising at either the same relative or same absolute work rate.

Dopaminergic and cholinergic antagonism in a novel-object detection task with rats.

In a free-choice test, rats display a tendency to interact more with a novel object than a familiar object. In the present report, we assessed the role of the dopaminergic and cholinergic systems in the expression of this novelty detection. Rats were injected with a dopaminergic antagonist (sulpiride, U-99194A, clozapine, or L-745,870) or a cholinergic antagonist (mecamylamine or scopolamine) prior to the free-choice novel-object test. The dopamine antagonists did not block novel-object detection. In contrast, scopolamine, but not mecamylamine, reliably blocked the expression of novelty detection, indicating a role for muscarinic receptors.

Chronic barbiturate treatment increases NMDA receptors but decreases kainate receptors in mouse cortex.

Chronic phenobarbital effects on brain NMDA and kainate receptors were assessed using [3H]MK-801 and [3H]kainate. Mice fed a phenobarbital diet for 7 days had a higher density of MK-801 binding sites (NMDA receptors) but a lower density of kainate receptors in cortex than control mice. No changes in MK-801 or kainate binding were observed in hippocampus. The results suggest brain area specific adaptation of certain glutamate receptors to chronic barbiturate treatment.

Development of three-dimensional form perception.

In three experiments with infants and one with adults we explored the generality, limitations, and informational bases of early form perception. In the infant studies we used a habituation-of-looking-time procedure and the method of Kellman (1984), in which responses to three-dimensional (3-D) form were isolated by habituating 16-week-old subjects to a single object in two different axes of rotation in depth, and testing afterward for dishabituation to the same object and to a different object in a novel axis of rotation. In Experiment 1, continuous optical transformations given by moving 16-week-old observers around a stationary 3-D object specified 3-D form to infants. In Experiment 2 we found no evidence of 3-D form perception from multiple, stationary, binocular views of objects by 16- and 24-week-olds. Experiment 3A indicated that perspective transformations of the bounding contours of an object, apart from surface information, can specify form at 16 weeks. Experiment 3B provided a methodological check, showing that adult subjects could neither perceive 3-D forms from the static views of the objects in Experiment 3A nor match views of either object across different rotations by proximal stimulus similarities. The results identify continuous perspective transformations, given by object or observer movement, as the informational bases of early 3-D form perception. Detecting form in stationary views appears to be a later developmental acquisition.

Thermoregulatory responses to cycling with and without a helmet.

This study examined the effects of wearing a helmet on selected body temperatures and perceived heat sensation of the head and body while cycling in a hot-dry (D) (35 degrees C, 20% relative humidity (RH) and hot-humid (H) (35 degrees C, 70% RH) environment. Ten male and four female cyclists (mean +/- SD: males = age 27 +/- 7 yr, peak O2 uptake (VO2) 4.10 +/- 0.54 L.min-1; females = age 26 +/- 3 yr, peak O2 uptake (VO2) 3.08 +/- 0.49 L.min-1) performed four randomized 90-min cycling trials at 60% of peak VO2 both with (HE) and without (NH) a commercially available cycling helmet in both D and H environments. VO2, core (Te), skin (Tsk), and head skin temperatures, heart rate (HR), rating of perceived exertion (RPE), and perceived thermal sensation of head (TSH) and body (TSB) were measured throughout exercise. For all measured variables, no significant difference was evident between HE and NH. However, Tc, Tsk, and mean head skin temperatures were higher (P < 0.001) in H than D. Likewise, RPE, TSH, TSB (P < 0.001), and sweat rates (H = 1.33 +/- 0.32, D = 1.14 +/- 0.23 L.h-1) (P < 0.01) were higher in H versus D. Results indicate that use of a commercially available cycling helmet while riding in a hot-dry or hot-humid environment does not cause the subjects to become more hyperthermic or increase perceived heat sensation of the head or body.

Effect of inosine supplementation on aerobic and anaerobic cycling performance.

Ten competitive male cyclists completed a Wingate Bike Test (WIN), a 30-min self-paced cycling performance bout (END), and a constant load, supramaximal cycling spring (SPN) to fatigue following 5 d of oral supplementation (5,000 mg.day-1) with inosine and placebo. Blood samples were obtained prior to and following both supplementation periods, and following each cycling test. Uric acid concentration was higher (P < 0.05) following supplementation with inosine versus placebo, but 2,3-DPG concentration was not changed. The data from WIN demonstrate that there were no significant differences in peak power (8.5 +/- 0.3 vs 8.4 +/- 0.3 W.kg body mass-1), end power (7.0 +/- 0.3 vs 6.9 +/- 0.2 W.kg body mass-1), fatigue index (18 +/- 2 vs 18 +/- 2%), total work completed (0.45 +/- 0.02 vs 0.45 +/- 0.02 kJ.kg body mass-1.30-s-1), and post-test lactate (12.2 +/- 0.5 vs 12.9 +/- 0.6 mmol.l-1) between the inosine and placebo trials, respectively. No difference was present in the total amount of work completed (6.1 +/- 0.3 vs 6.0 +/- 0.3 kJ.kg body mass-1) or post-test lactate (8.4 +/- 1.0 vs 9.9 +/- 1.3 mmol.l-1) during END between the inosine and placebo trials, respectively. Time to fatigue was longer (P < 0.05) during SPN for the placebo (109.7 +/- 5.6 s) versus the inosine (99.7 +/- 6.9 s) trial, but post-test lactate (14.8 +/- 0.7 vs 14.6 +/- 0.8 mmol.l-1) was not different between the treatments, respectively. These findings demonstrate that prolonged inosine supplementation does not appear to improve aerobic performance and short-term power production during cycling and may actually have an ergolytic effect under some test conditions.

Effects of precooling on thermoregulation during subsequent exercise.

PURPOSE: The purpose of this study was to examine the effect of a decreased body core temperature before a simulated portion of a triathlon (swim,15 min; bike, 45 min) and examine whether precooling could attenuate thermal strain and increase subjective exercise tolerance in a warm environment (26.6 degrees C/60% relative humidity (rh)). METHODS: Six endurance trained triathletes (28+/-2 yr, 8.2+/-1.7% body fat) completed two randomly assigned trials 1 wk apart. The precooling trial (PC) involved lowering body core temperature (-0.5 degrees C rectal temperature, Tre) in water before swimming. The control trial (CON) was identical except no precooling was performed. Water temperature and environmental conditions were maintained at 25.6 degrees C and 26.6 degrees C/60% rh, respectively, throughout all testing. RESULTS: Mean time to precool was 31+/-8 min and average time to reach baseline Tre during cycling was 9+/-7 min. Oxygen uptake (VO2), HR, skin temperature (Tsk), Tre, RPE, and thermal sensation (TS) were recorded following the swim segment and throughout cycling. No significant differences in mean body (Tb) or Tsk were noted between PC and CON, but a significant difference (P < 0.05) in Tre between treatments was noted through the early phases of cycling. No significant differences were reported in HR, VO2, RPE, TS, or sweat rate (SR) between treatments. Body heat storage (S) was negative following swimming in both PC (-92+/-6 W x m2) and CON (-66+/-9 W x m2). A greater S occurred in PC (109+/-6 W x m2) vs CON (79+/-4 W x m2) during cycling (P < 0.05). CONCLUSIONS: Precooling attenuated the rise in Tre, but this effect was transient. Therefore, precooling is not recommended before a triathlon under similar environmental conditions.

Stressor controllability, social interaction, and benzodiazepine systems.

Effects of benzodiazepine receptor-active compounds on inescapable shock-produced changes in social interaction were studied in the rat. Inescapably shocked animals exhibited less social interaction in a novel situation than did escapably shocked or unshocked rats 24 h after shock. Administration of the selective benzodiazepine receptor antagonist flumazenil at the time of shock prevented the decrease in social interaction. Social interaction was unaffected by the same treatment at the time of measurement. Reduction in social interaction induced by inescapable stress endured for 48-72 h following stressor exposure but was absent 168 h after stress. It was subject to antagonist blockade at all measured time points. Stress-induced decreases in social interaction were also blocked by the benzodiazepine chlordiazepoxide given at the time of shock treatment. The receptor antagonist did not reverse this blockade. An inverse agonist, the beta-carboline FG 7142, administered in place of inescapable shock, produced an identical pattern of social interaction in a dose-dependent manner. The inverse agonist effect was also reversed by the antagonist. The results from antagonist, agonist, and inverse agonist treatments all suggest that an endogenous benzodiazepine receptor inverse agonist is released at the time of inescapable shock and is involved in producing the changes in social interaction subsequently measured.

Diabetes in old age: an emerging epidemic.

Diabetes in the elderly is emerging as one of the most important public health problems of the 21st century. In developing countries, the majority of people with diabetes are in the age range of 45-64 years. A better understanding on the pathogenesis of diabetes in the aging population is required to successfully treat and prevent its devastating complications. Changes in body composition with accumulation of fat in the abdomen is a key factor in the causation of diabetes in the aging population. The size and strength of skeletal muscle, a major tissue involved in glucose metabolism, also declines leading to muscle weakness and a reduction in physical activity. These changes lead to marked reduction in energy expenditure and abdominal fat accumulation causing insulin resistance. Recent evidence suggests that four months of aerobic exercise can improve muscle oxidative capacity similarly in younger and older people, but that insulin sensitivity is less likely to improve in older people. It appears that older people need to exercise more frequently to improve their insulin sensitivity. Diagnosis and management of diabetes in the elderly requires special attention since age, genetics, body composition and lifestyle factors all interact. Increasing evidence suggests that postprandial hyperglycemia is more sensitive to diagnose diabetes in elderly people than in the young. Age related changes in body function and cognition demand special caution in the selection of hypoglycemic drugs in the elderly. Targets of diabetes therapy in the elderly have to be individualized, considering the age of the patient, remaining life-expectancy and severity of co-morbid conditions. Short acting insulin secretogogues are preferred to avoid prolonged and frequent hypoglycemia. Judicious choice of insulin sensitizers, timely introduction of insulin, meticulous control of hypertension and hyperlipidemia are critical to prevent complications.

Mechanisms of sarcopenia of aging.

Age-related sarcopenia is characterized by decreased muscle mass and muscle strength, and increased muscle fatigability. A decrease in synthesis rates of mixed muscle proteins (average of all muscle proteins), myosin heavy chain (responsible for adenosine triphosphatase action) and mitochondrial proteins (site of adenosine triphosphate production) have been described with aging. Most of these changes start by middle age, thus contributing to the progressive decline in muscle size and function. How closely these changes are related to lifestyle and the decline in several hormones, particularly growth hormone, insulin-like growth factor-I, testosterone and dehydroepiandrosterone, remains to be clearly defined. The ability to measure the specific effects of different types of exercise training on muscle protein metabolism has only recently become available. Thus, future investigations will continue to improve our understanding of protein metabolism in aging skeletal muscles. The development and assessment of successful countermeasures to age-related sarcopenia will hopefully follow these discoveries.

The effect of age on protein metabolism.

The mechanisms of senescence remain to be fully defined. This review focuses on recent advances in our understanding of body protein turnover, which is essential for the remodeling of tissues and production of specific proteins in time of need. Recent advances in technology make it possible to measure the synthesis rate of muscle myosin heavy chain, mitochondrial proteins and sarcoplasmic proteins, providing insight into the mechanisms of the sarcopenia of aging. A reduced synthesis rate of myosin heavy chain and mitochondrial protein may explain muscle weakness and fatiguability that occurs with aging. Aging also seems to affect selected liver proteins such as fibrinogen. The potential roles of exercise and hormone replacement in slowing the age-related decline in protein turnover is discussed.

Does aging adversely affect muscle mitochondrial function?

Muscle oxidative function appears to decline with aging, and evidence suggests that this is related to reduced synthesis of mitochondrial and other muscle proteins. Causes for these events may include mtDNA damage or reduced mtDNA copy numbers, reduced oxidative enzyme activities and ATP production, and increased proton leak.

Muscle protein metabolism and the sarcopenia of aging.

Loss of muscle mass, strength, and oxidative capacity accompanies normal aging in humans. The mechanisms responsible for these changes remain to be clearly defined. Muscle protein mass and function depend on protein turnover. Synthesis rate of the major muscle contractile protein, myosin heavy chain (MHC), and transcript levels of fast MHC isoforms decrease in association with strength reductions, while mitochondrial protein synthesis rate declines in parallel with activities of mitochondrial enzymes and maximal oxidative capacity (VO2max). Resistance exercise training increases the synthesis rate of MHC and transcript levels of the slow MHC isoform in older humans, along with increasing muscle strength. The relationship between the synthesis of muscle proteins, and muscle size and function, with aging and exercise training are discussed in this review.

Glycemic and insulinemic responses to multiple preexercise carbohydrate feedings.

This investigation was undertaken to determine whether consuming several small feedings of preexercise carbohydrate (CHO), rather than a single bolus, would affect blood glucose and insulin responses during rest and exercise. Eight trained cyclists ingested 22.5, 45, or 75 total g maltodextrin and dextrose dissolved in 473 ml of water or an equal volume of placebo (PL). Drinks were divided into four portions and consumed at 15-min intervals in the hour before a 120-min ride at 66% VO2max. Serum glucose values were elevated by the CHO feedings at rest and fell significantly below baseline and PL at 15 min of exercise. However, glucose concentrations were similar in each of the CHO trials. Insulin concentrations also increased rapidly during rest, then fell sharply at the onset of exercise. The findings demonstrate that CHO consumed within an hour before exercise, even when taken in several small feedings, can produce transient hypoglycemia near the onset of exercise. Additionally, the magnitude of the response appears to be unrelated to either the amount of CHO ingested or the insulin response.

The effect of upper body exercise intensity and duration on post-exercise oxygen consumption.

This study assessed excess post-exercise oxygen consumption (EPOC) following upper body exercise (UBE) of different intensity and duration. Ten subjects, 5 male and 5 female (age: 26.7 +/- 4.9 yr; peak UBE oxygen uptake [VO2peak]: 1.78 +/- 0.57 l. min-1, 25.6 +/- 5.8 ml.kg-1. min-1) performed three randomized tests on an arm crank ergometer: 1) low intensity, short duration (LS) = 35% VO2peak for 15 min; 2) low intensity, long duration (LL) = 35% VO2peak for 30 min; 3) high intensity, short duration (HS) = 70% VO2peak for 15 min. Subjects reported for all tests in the morning and in a fasted and rested state. Exercise was preceded by a 30 min seated baseline. Recovery VO2 was continuously monitored until baseline was re-established. EPOC duration (p < 0.01) and magnitude (p < 0.01) were significantly greater following HS, while LL and LS did not differ in response (duration and magnitude: HS = 14.0 +/- 6.5 min, 32.5 +/- 24.6 kJ; LL = 5.5 +/- 4.4 min, 12.3 +/- 8.6 kJ; LS = 5.7 +/- 4.9 min, 10.3 +/- 5.3 kJ). HS also had higher HR (73 +/- 10 b.min-1, p < 0.01) at end-EPOC compared to LL (64 +/- 8 b.min-1) and LS (66 +/- 8 b.min-1), and baseline HS values (63 +/- 8 b. min-1). Results from this study indicate that UBE intensity has a greater effect on EPOC than exercise duration under these conditions. UBE appears to have similar EPOC patterns as lower body exercise.

Infant perception of object unity from translatory motion in depth and vertical translation.

Previous research indicated that 4-month-old infants perceive the unity of a center-occluded object when its visible ends share a common lateral translation in space. The present work investigated the class of motion relationships that can specify object unity to infants, specifically, asking whether it includes all rigid translations. 3 experiments tested the informativeness of 2 axes of translation not previously studied: translation in depth and vertical translation. These motions also allowed assessment of certain interpretations of previous results that invoke specific sensory consequences of lateral movement, rather than perceived motion, as underlying perceived unity. Experiment 1 provided evidence that a small extent of translation in depth specified the unity of an object, but only to the subgroup of infants who detected the motion. Experiment 2 used a greater displacement in depth and found clear evidence for perception of object unity. Experiment 3 indicated that vertical translation, in which the 2 visible areas of the partly hidden object undergo dissimilar changes, also specifies object unity to infants. These results suggest that infants' perception of object unity depends on perceived coherence of motion, no matter how specified, and that the class of informative motions includes all rigid translations.