Examination of the Factor Structure and Correlates of the Perceived Military Healthcare Stressors Scale

The current study evaluated the factor structure, reliability estimates, correlates, and predictive utility of the Perceived Military Healthcare Stressor Scale (PMHSS) in a sample of active duty military medical personnel (N = 1,131) deployed to Joint Base Balad in Iraq. The sample was composed of an approximately even split of male (51.2%) and female (48.8%) participants who ranged in age from 18 to 60 years. The PMHSS is a 21‐item measure that was designed to assess the impact of specific medical stressors that military healthcare providers may encounter while deployed. An exploratory factor analysis of the PMHSS revealed the presence of two distinct factors: trainable and futility stressors. Confirmatory factor analysis showed that a bifactor model best represented the data, with all items loading higher on the general factor relative to their specific subscale factors. Evidence of partial scalar invariance by gender was found. The PMHSS was significantly correlated with several convergent measures, including assessments of posttraumatic stress disorder (PTSD), depression severity, distress due to both combat exposure and general deployment‐related concerns, and positive affect, rs = .30–.59. PMHSS scores were more strongly correlated with PTSD and depression in women than in men, and they provided incremental validity in predicting convergent measures over and above other related constructs. Healthcare–specific stressors are an understudied area, and this study provides new insights into how deployment‐related caregiving stress may impact deployed military medical personnel independently of the impact of combat experiences.     

Peroxiredoxin1 prevents excessive endothelial activation and early atherosclerosis

The peroxiredoxin (Prdx) family of antioxidant enzymes uses redox-active cysteines to reduce peroxides, lipid hydroperoxides, and peroxynitrites. Prdx1 is known to be important to protect red blood cells against reactive oxygen species and in tumor prevention. In this study, the role of Prdx1 in inflammation, thrombosis, and atherosclerosis was investigated. Using intravital microscopy, we showed that the number of leukocytes rolling per minute in unstimulated veins was increased by 2.5-fold in Prdx1(-/-) compared to Prdx1(+/+) mice. In Prdx1(-/-) mice, 50% of leukocytes rolled at a velocity <10 mum/sec compared with 10% in Prdx1(+/+) mice, suggesting that adhesion molecule density on the endothelium may have been increased by Prdx1 deficiency. Indeed, endothelial P-selectin, soluble P-selectin, and von Willebrand factor in plasma were increased in Prdx1(-/-) mice compared to Prdx1(+/+) mice, indicating elevated Weibel-Palade body release. In contrast to this excessive endothelial activation, Prdx1(-/-) platelets showed no sign of hyperreactivity, and their aggregation both in vitro and in vivo was normal. We also examined the role of Prdx1 in the apoE(-/-) murine spontaneous model of atherosclerosis. Prdx1(-/-)/apoE(-/-) mice fed normal chow developed larger, more macrophage-rich aortic sinus lesions than Prdx1(+/+)/apoE(-/-) mice, despite similar amounts and size distributions of cholesterol in their plasma lipoproteins. Thus, Prdx1 protects against excessive endothelial activation and atherosclerosis, and the Prdx1(-/-) mice could serve as an animal model susceptible to chronic inflammation.     

Distinct neural ensemble response statistics are associated with recognition and discrimination of natural sound textures

The perception of sound textures, a class of natural sounds defined by statistical sound structure such as fire, wind, and rain, has been proposed to arise through the integration of time-averaged summary statistics. Where and how the auditory system might encode these summary statistics to create internal representations of these stationary sounds, however, is unknown. Here, using natural textures and synthetic variants with reduced statistics, we show that summary statistics modulate the correlations between frequency organized neuron ensembles in the awake rabbit inferior colliculus (IC). These neural ensemble correlation statistics capture high-order sound structure and allow for accurate neural decoding in a single trial recognition task with evidence accumulation times approaching 1 s. In contrast, the average activity across the neural ensemble (neural spectrum) provides a fast (tens of milliseconds) and salient signal that contributes primarily to texture discrimination. Intriguingly, perceptual studies in human listeners reveal analogous trends: the sound spectrum is integrated quickly and serves as a salient discrimination cue while high-order sound statistics are integrated slowly and contribute substantially more toward recognition. The findings suggest statistical sound cues such as the sound spectrum and correlation structure are represented by distinct response statistics in auditory midbrain ensembles, and that these neural response statistics may have dissociable roles and time scales for the recognition and discrimination of natural sounds.

What makes a sound natural, and what are the neural codes that support recognition and discrimination of real-world natural sounds? Although it is known that the early auditory system decomposes sounds along fundamental acoustic dimensions such as intensity and frequency, the higher-level neural computations that mediate natural sound recognition are poorly understood. This general lack of understanding is in part attributed to the structural complexity of natural sounds, which is difficult to study with traditional auditory test stimuli, such as tones, noise, or modulated sequences. Such stimuli can reveal details of the neural representation for relatively low-level acoustic cues, yet they don’t capture the rich and diverse statistical structure of natural sounds. Thus, they cannot reveal many of the computations associated with higher-level sound properties that facilitate auditory tasks such as natural sound recognition or discrimination. A class of stationary natural sounds termed textures, such as the random sounds emanating from a running stream, a crowded restaurant, or a chorus of birds, have been proposed as alternative natural stimuli which allow for manipulating high-level acoustic structure (1). Texture sounds are composed of spatially and temporally distributed acoustic elements that are collectively perceived as a single source and are defined by their statistical features. Identification of these natural sounds has been proposed to be mediated through the integration of time-averaged summary statistics, which account for high-level structures such as the sparsity and time-frequency correlation structure found in many natural sounds (1–3). Using a generative model of the auditory system to measure summary statistics from natural texture sounds, it is possible to synthesize highly realistic synthetic auditory textures (1). This suggests that high-order statistical cues are perceptually salient and that the brain might extract these statistical features to build internal representations of sounds.Although neural activity throughout the auditory pathway is sensitive to a variety of statistical cues such as the sound contrast, modulation power spectrum, and correlation structure (4–12), how sound summary statistics contribute toward basic auditory tasks such as recognition and discrimination of sounds is poorly understood. Furthermore, it is unclear where along the auditory pathway summary statistics are represented and how they are reflected in neural activity. The inferior colliculus (IC) is one candidate midlevel structure for representing such summary statistics. As the principal midbrain auditory nucleus, the IC receives highly convergent brainstem inputs with varied sound selectivities. Neurons in the IC are selective over most of the perceptually relevant range of sound modulations and neural activity is strongly driven by multiple high-order sound statistics (4–7, 10). In previous work, we showed the correlation statistics of natural sounds are highly informative about stimulus identity and they appear to be represented in the correlation statistics of auditory midbrain neuron ensembles (4). Correlations between neurons have also been proposed as mechanisms for pitch identification (13) and sound localization (14). This broadly supports the hypotheses that high-order sound statistics are reflected in the response statistics of neural ensembles and that these neural response statistics could potentially subserve basic auditory tasks.Here using natural and synthetic texture sounds, we test the hypothesis that statistical structure in natural texture sounds modulates the response statistics of neural ensembles in the IC of unanesthetized rabbits, and that distinct neural response statistics have the potential to contribute toward sound recognition and discrimination behaviors. By comparing the performance of neural decoders with human texture perception, we find that place rate representation of sounds (neural spectrum) accumulates evidence about the sounds on relatively fast time scales (tens of milliseconds) exhibiting decoding trends that mirror those seen for human texture discrimination. High-order statistical sound cues, by comparison, are reflected in the correlation statistics of neural ensembles, which require substantially longer evidence accumulation times (>500 ms) and follow trends that mirror those measured for human texture recognition. Collectively, the findings suggest that spectrum cues and accompanying place rate representation (neural spectrum) may contribute surprisingly little toward the recognition of auditory textures. Instead, high-order statistical sound structure is reflected in the distributed patterns of correlated activity across IC neural ensembles and such neural response structure has the potential to contribute toward the recognition of natural auditory textures.     

Impact of Combat Deployment on Psychological and Relationship Health: A Longitudinal Study

Although previous research has indicated an elevated prevalence of posttraumatic stress disorder (PTSD) and other mental health problems among veterans of Operations Iraqi Freedom and Enduring Freedom following deployment, most of this research has been cross‐sectional and has focused on a limited range of military groups and outcome criteria. This investigation was a longitudinal study of U.S. Air Force security forces assigned to a year‐long high‐threat ground mission in Iraq to determine the degree to which airmen's emotional and behavioral health and committed relationships were adversely impacted by an extended deployment to a warzone. Participants were a cohort of 164 security forces airmen tasked to a 365‐day deployment to train Iraqi police. Airmen completed study measures both prior to and 6–9 months following deployment. Rates of deterioration in individual and interpersonal adjustment were both significant and medium to large in magnitude of effect, d = 0.43 to 0.90. Results suggest that the negative effects of deployment are related to levels of traumatic experiences and do not spontaneously remit within the first 6–9 months following return from deployment—particularly among those service members having relatively lower levels of social support.     

Alpha-tocopherol metabolism is abnormal in scavenger receptor class B type I (SR-BI)-deficient mice

Despite the physiologic importance of vitamin E, in particular its alpha-tocopherol (alpha-T) isoform, the molecular mechanisms involved in the cellular uptake of this antioxidant from plasma lipoproteins have not been well-defined. Recent studies have suggested that selective lipid uptake, rather than endocytosis, is important for alpha-T delivery to cells. Here we show that the scavenger receptor class B type I (SR-BI), which mediates cellular selective cholesteryl ester uptake from lipoproteins, facilitates efficient transfer of alpha-T from HDL to cultured cells. In SR-BI-deficient mutant mice, relative to wild-type control animals, there was a significant increase in plasma alpha-T levels (1.1- to 1.4-fold higher) that was mostly due to the elevated alpha-T content of their abnormally large plasma HDL-like particles. This increase in plasma alpha-T in SR-BI knockout mice was accompanied by a significant decrease (65-80%) in the alpha-T concentrations in bile and several tissues including ovary, testis, lung and brain. SR-BI deficiency did not alter the alpha-T concentrations of the liver, spleen, kidney or white fat. These data show that SR-BI plays an important role in transferring alpha-T from plasma lipoproteins to specific tissues. Also, in the case of the liver as was previously shown for SR-BI-dependent hepatic cholesterol transport, SR-BI-mediated uptake of alpha-T was primarily coupled to biliary excretion rather than to tissue accumulation. Defective tissue uptake of lipoprotein alpha-T in SR-BI-deficient mice may contribute to the reproductive and cardiovascular pathologies exhibited by these animals.     

Rôle de l’alimentation dans la prévention des caries

Over the last three decades the condition of the teeth of children has improved tremendously. This has generally been attributed to the increased use of fluoride toothpaste. During this period the total amount of sugars disappearing into the population per capita has hardly changed. This suggests that the relationship between diet and caries has to be reassessed, which provokes different opinions among dental experts.Some suggest a maximum threshold level for the daily amount of sugars to prevent caries. Others propose that in general the amount of sugars eaten is not an important determinant of caries experience. The scientific evidence for the various opinions on the role of diet in caries development will be discussed. It is concluded that the role of diet is not so much related to the diet itself, but to the individual behaviour of people. Where oral hygiene and fluoride supplementation are adequate, the diet has become a lesser factor in caries prevention. However, those diets may cause caries when there is too little fluoride. It is a mistake to classify a diet as cariogenic it may be potentially cariogenic. When one wants to decrease this potency, one should modify those factors that are actually controlling it, which is, in most cases, the topical presence of fluoride and not the composition of the diet.     

The relationship between a pentagastrin-stimulated gastric luminal acid production test (Gastrotest) and enteral feeding-related gastrointestinal complications in critically ill patients

Gastrointestinal feeding-related complications (GICs) are common in critically ill patients. Unfortunately, patients at risk for GICs cannot be easily identified. Therefore, we performed a prospective study of 20 critically ill patients to determine the association between a pentagastrin-stimulated gastric acid production test and GICs. Before feeding, the change in the pH of gastric juice was measured in response to a subcutaneous injection of pentagastrin (Gastrotest). We recorded GICs and the feeding volume ratio during each patient's intensive care unit (ICU) stay. Nineteen patients' data were analyzed and 9 patients (47%) developed > or =1 GIC, including large gastric residuals, 26%; abdominal distension, 26%; and vomiting, 21%. Patients with GICs had a longer length of ICU stay (mean 21.3, range 5-45 versus 10.1, range 3-32; P < 0.05). The 9 patients (47%) who were Gastrotest responders before starting enteral feeding exhibited a significantly larger volume ratio (P = 0.01) and fewer GICs (1 [11%] versus 8 [80%]; P < 0.05). Abdominal distension was seen in only nonresponders. The positive and negative predictive values for this test's ability to predict GICs were 80% and 88.9%, respectively. Responding to a pentagastrin-stimulated gastric luminal acid production test is associated with the administration of larger volumes of enteral feed and fewer GICs.