Purification and properties of 5,6-dihydropyrimidine amidohydrolase from calf liver

5,6-Dihydropyrimidine amidohydrolase was isolated from an acetone powder of calf liver and purified to homogeneity. Purification made use of heat treatment, ammonium sulfate fractionation and chromatography on Chelating Sepharose and DEAE-Sepharose with 44% recovery of total activity. The native enzyme has a molecular mass of 217 kDa consisting of four subunits with a molecular mass of 54 kDa each. The amidohydrolase is a metalloenzyme containing one zinc atom/subunit. The enzyme can slowly be inactivated by chelating agents. The kinetic parameters for substrates, 5,6-dihydrouracil, 5,6-dihydrothymine and glutarimide were determined. From log Vmax/KM data, a pKa of 7.6 could be calculated suggesting the formation of a zinc-bound hydroxyl ion which carries out the nucleophilic attack on the C-4 of dihydrouracil.

Acid-base catalytic mechanism of dihydropyrimidinase from pH studies

The pH dependence of kinetic parameters and solvent deuterium isotope effects have been used to probe the mechanism of the dihydropyrimidinase from the liver of pig and calf. The V/K for 5,6-dihydrouracil (DHU) (or the alternative substrate glutarimide) measured with either the native zinc or cadmium-substituted enzymes decreases at both low and high pH giving pK values of about 7.5-8 and 9-10. The low pK value observed in V is perturbed significantly to lower pH (approximately 6), and the high pK is not observed. The binding of glutarate monoamide is optimum when the group with a pK of 7.7 is protonated, and this same group must be protonated for the reverse reaction, that is, formation of DHU from N-carbamoyl-beta-alanine. These data are consistent with a general base mechanism and in addition suggest that the enzyme is present initially with a water bound to the active site zinc. The enzymic general base with a pK of 7.5-8 is required to activate water for nucleophilic attack on the C-4 of 5,6-dihydrouracil which is directly coordinated to the active site zinc. The second group with a pK of 9-10 likely reflects Zn-water ionization of the free enzyme. The water bound to the active site Zn is displaced by reactant binding, and thus the pK of 9-10 is not observed in the V profile. Solvent deuterium isotope effects are near unity on the V/K for the natural substrate 5,6-dihydrouracil, but a finite effect of 1.6 is observed on V.(ABSTRACT TRUNCATED AT 250 WORDS)

Using magnetic resonance imaging to characterize pedicle asymmetry in both normal patients and patients with adolescent idiopathic scoliosis

STUDY DESIGN

Morphometric analysis of vertebrae from normal patients and patients with adolescent idiopathic scoliosis.

OBJECTIVES

To use magnetic resonance imaging to assess pedicle asymmetry in normal patients and patients with adolescent idiopathic scoliosis in the early stages of scoliosis development and to determine if patients with adolescent idiopathic scoliosis exhibited a consistent vertebral morphology.

SUMMARY OF BACKGROUND DATA

To date, most studies of vertebral morphology in adolescent idiopathic scoliosis have produced conflicting data, especially on pedicle length, and have been conducted on patients in the late stages of scoliosis development, which may affect the patterns of vertebral morphology detected. Magnetic resonance imaging enables in vivo assessment of curves during development and permits improved acquisition of transverse images.

METHODS

Magnetic resonance images of 76 pedicles from 8 normal patients and 80 pedicles from 10 patients with adolescent idiopathic scoliosis were examined retrospectively. Recorded parameters included pedicle lengths, pedicle widths, pedicle areas, pedicle perimeters, and lamina lengths. The extent and direction of asymmetry in vertebrae from normal patients and patients with adolescent idiopathic scoliosis were determined and compared.

RESULTS

Normal patients displayed significant neural arch asymmetry, with the left sided measurements being greater. Patients with adolescent idiopathic scoliosis also displayed significant neural arch asymmetry; however, the longer pedicle was not consistently on the convexity or the concavity.

CONCLUSIONS

The baseline used to assess adolescent idiopathic scoliosis vertebral morphology must take into consideration the extent and direction of normal vertebral asymmetry. The pattern of vertebral asymmetry seen inadolescent idiopathic scoliosis may depend on the specific cause of the disorder, with no consistent pattern evident when data from different causes are pooled together.

The neglected role of collective customer perceptions in shaping collective employee satisfaction, service climate, voluntary turnover, and involuntary turnover: A cautionary note

Although the service-profit chain posits that employees and customers are interrelated at the unit level (Heskett, Sasser, & Schlesinger, 1997), most theory and practice give primary emphasis to the employee. In this study, we sought to draw attention to the relatively neglected influence that customers may collectively have on employees. Specifically, we examined how collective customer perceptions of service quality relate to collective employee job satisfaction, service climate, and collective turnover (voluntary and involuntary). Using a sample of 294 bank branches, 1,975 employees, and 52,920 customers, modeled at the branch level over 2 years, we found that collective customer perceptions of service quality produced a stronger effect on collective employee job satisfaction and service climate than vice versa. We also provided the first tests demonstrating that collective customer perceptions of service quality significantly and independently influence collective voluntary turnover, even while simultaneously modeling collective employee job satisfaction and service climate. Further, we showed that the effects of collective turnover (voluntary and involuntary) are primarily related to collective customer perceptions and service climate, but through different paths. Although the turnover base rates are modest, these empirical findings highlight the role that collective customer perceptions can have in shaping collective employee attitudes, climate, and turnover and, thus, should be considered and replicated in future theory and research. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

The paradoxical decline and growth of trust as a function of borderline personality disorder trait count: Using discontinuous growth modelling to examine trust dynamics in response to violation and repair

Borderline personality disorder (BPD) is associated with paradoxical trust cognitions and behaviours. While BPD is associated with difficulty forming trust and maintaining cooperation in trust-based exchanges, design and analytical methodology best suited to reveal the temporal ebb and flow of trust have been underutilized. We used an economic game to examine the trajectories of trust as it forms, dissolves, and restores in response to trust violation and repair, and to explain how these vary as a function of borderline pathology. Young adults (N = 234) played a 15-round trust game in which partner trustworthiness was varied to create three phases: trust formation, trust violation, and trust restoration. Discontinuous growth modelling was employed to capture the trends in trust over time and their relationship with BPD trait count. BPD trait count was associated with an incongruous pattern of trust behaviour in the form of declining trust when interacting with a new and cooperative partner, and paradoxically, increasing trust following multiple instances of trust violation by that partner. BPD trait count was also associated with trust restoring at a faster rate than it was originally formed. By adopting a methodology that recognizes the dynamic nature of trust, this study illustrated at a micro level how relational disturbances may be produced and maintained in those with a moderate to high BPD trait count. Further investigation of the factors and processes that underlie these incongruous trust dynamics is recommended.

Caring for their own: How firm actions to protect essential workers and CEO benevolence influenced stakeholder sentiment during the COVID-19 pandemic

Whereas many workplaces shut down following the onset of the COVID-19 pandemic, many others in essential industries had to remain operational, thus exposing their employees to COVID-19's inherent dangers. These firms were pressed to take immediate action to protect their employees' safety and financial well-being. However, firms varied considerably in the degree to which they took action, and stakeholders appeared to take notice. Leveraging attribution theory, we build theory around the impact of firm actions to protect employee safety and compensation on stakeholder sentiment toward the firm. We further examined how firm leadership helped shape stakeholder sentiment by theorizing about the joint impact of actions with Chief Executive Officer (CEO) benevolence. We built a unique, multisourced data set and tested our theory on a sample of public firms in the consumer staples sector. Our longitudinal analysis of positive stakeholder sentiment expressed on social media demonstrated the importance of these immediate firm actions on sentiment in the initial months of the pandemic. Specifically, firm compensation actions were associated with a growth in positive sentiment over these months, particularly when made by CEOs with high benevolence, whereas firm safety actions led to growth in positive sentiment but only when made by CEOs with low benevolence. We discuss the implications of these findings for our understanding of firm actions and leadership at the onset of the COVID-19 pandemic. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Reflecting on death amidst COVID-19 and individual creativity: Cross-lagged panel data analysis using four-wave longitudinal data

The current COVID-19 pandemic has claimed millions of lives all across the globe, making death more salient to many who may not have been readily cognizant of their mortality. While employees in certain occupations routinely deal with the idea of death or mortality (e.g., hospital workers, firefighters, and police officers), it is uncommon for the average employee to be within an environment that makes them aware of death. However, death awareness has been found to be negatively related to many important outcomes for the organization, including creativity. In the present study, using four-wave longitudinal data collected weekly-during late-June to late-July, 2020, we examine how employees react during the initial peak of COVID-19 pandemic in the United States in terms of death anxiety and death reflection (two different reactions to death awareness) and whether or not death anxiety and death reflection are related to creativity. Conducting cross-lagged panel modeling on four-wave longitudinal data obtained from 605 full-time employees, we find that positive outcomes can come from such trying times as death reflection is positively related to creativity. We offer timely, valuable implications for theory and practice. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Effects of prior deployments and perceived resilience on anger trajectories of combat-deployed soldiers

BACKGROUND

Problematic anger is frequently reported by soldiers who have deployed to combat zones. However, evidence is lacking with respect to how anger changes over a deployment cycle, and which factors prospectively influence change in anger among combat-deployed soldiers.

METHODS

Reports of problematic anger were obtained from 7298 US Army soldiers who deployed to Afghanistan in 2012. A series of mixed-effects growth models estimated linear trajectories of anger over a period of 1-2 months before deployment to 9 months post-deployment, and evaluated the effects of pre-deployment factors (prior deployments and perceived resilience) on average levels and growth of problematic anger.

RESULTS

A model with random intercepts and slopes provided the best fit, indicating heterogeneity in soldiers' levels and trajectories of anger. First-time deployers reported the lowest anger overall, but the most growth in anger over time. Soldiers with multiple prior deployments displayed the highest anger overall, which remained relatively stable over time. Higher pre-deployment resilience was associated with lower reports of anger, but its protective effect diminished over time. First- and second-time deployers reporting low resilience displayed different anger trajectories (stable v. decreasing, respectively).

CONCLUSIONS

Change in anger from pre- to post-deployment varies based on pre-deployment factors. The observed differences in anger trajectories suggest that efforts to detect and reduce problematic anger should be tailored for first-time v. repeat deployers. Ongoing screening is needed even for soldiers reporting high resilience before deployment, as the protective effect of pre-deployment resilience on anger erodes over time.

Associations of active-duty mental health trajectories with post-military adjustment: Results from the STARRS Longitudinal Study

BACKGROUND

Many servicemembers experience difficulties transitioning from military to civilian life. We examined whether changes in mental health observed during active duty were associated with indices of post-military adjustment.

METHODS

Survey data from the multi-wave Army STARRS Pre/Post Deployment Study (PPDS; conducted 2012-2014) were linked to follow-up data from wave 1 of the STARRS Longitudinal Study (STARRS-LS1; conducted 2016-2018). Empirical Bayes estimates of intercepts and slopes of posttraumatic stress, problematic anger, and depressive symptoms during the PPDS were extracted from mixed-effects growth models and evaluated as predictors of life stress among 1080 participants who had separated or retired from the Army at STARRS-LS1; and of job satisfaction among 586 veterans who were employed at STARRS-LS1.

RESULTS

Higher average levels and larger increases in posttraumatic stress, anger, and depression over the deployment period were each associated with increased stress and (in the case of anger and depression) reduced job satisfaction. Posttraumatic stress and anger slopes were associated with overall stress (b = 5.60, p < 0.01 and b = 15.64, p = 0.04, respectively) and relationship stress (b = 5.50, p = 0.01 and b = 22.86, p = 0.01, respectively) beyond the average levels of those symptoms.

LIMITATIONS

Some transition-related difficulties may have resolved before outcome assessment; some measures were not previously validated.

CONCLUSIONS

Larger increases in posttraumatic stress and anger over a deployment period were associated with increased stress after leaving the Army, even after controlling for average symptom levels during the same period. Monitoring changes in mental health during active duty may help identify personnel who need additional support to facilitate the military-to-civilian transition.

Interactive effects of genetic liability and combat exposure on risk of alcohol use disorder among US service members

BACKGROUND

An improved understanding of pathways to alcohol use disorder (AUD) among service members may inform efforts to reduce the substantial impact of AUD on this population. This study examined whether the relationship between a service-related risk factor (combat exposure) and later AUD varied based on individual differences in genetic liability to AUD.

METHODS

The sample consisted of 1203 US Army soldiers of genetically determined European ancestry who provided survey and genomic data in the Army STARRS Pre/Post Deployment Study (PPDS; 2012-2014) and follow-up survey data in wave 1 of the STARRS Longitudinal Study (2016-2018). Logistic regression was used to estimate the conditional effect of combat exposure level (self-reported in PPDS) on odds of probable AUD diagnosis at follow-up, as a function of a soldier's polygenic risk score (PRS) for AUD.

RESULTS

The direct effect of combat exposure on AUD risk was non-significant (AOR=1.12, 95 % CI=1.00-1.26, p=.051); however, a significant combat exposure x PRS interaction was observed (AOR=1.60, 95 % CI=1.03-2.46, p=.033). Higher combat exposure was more strongly associated with elevated AUD risk among soldiers with heightened genetic liability to AUD.

CONCLUSIONS

The effect of combat exposure on AUD risk appeared to vary based on a service member's level of genetic risk for AUD. Continued investigation is warranted to determine whether PRS can help stratify AUD risk within stress-exposed groups such as combat-deployed soldiers. Such efforts might reveal opportunities to focus prevention efforts on smaller subgroups at the intersection of having both environmental exposures and genetic vulnerability to AUD.

A person-centered approach to behaving badly at work: An examination of workplace deviance patterns

To investigate research questions surrounding workplace deviance, scholars have primarily applied variable-centered approaches, such as overall deviance measures or those that separate interpersonal deviance and organizational deviance. These approaches, however, ignore that individuals might employ more complex combinations of deviance behaviors that do not fit neatly within the existing variable frameworks. The present study explores whether person-centered deviance classes emerge in a comprehensive database of the prior studies. We then investigated whether these classes showed differences in antecedents and correlates in an independent sample of working adults from multiple industries. In Study 1, a multilevel latent class analysis of 20 independent samples and 6,218 individuals revealed five classes of workplace deviance, thus providing preliminary support for a person-centered approach. In Study 2, a time-lagged sample of 553 individuals showed the emergence of five classes that largely reflected the patterns found in Study 1. Study 2 points to meaningful differences between classes of deviance behaviors and antecedents, including abusive supervision, Openness, Conscientiousness, Agreeableness, Emotional Stability, and psychological entitlement; classes are also uniquely associated with correlates such as organizational citizenship behaviors, turnover intentions, job performance, and job satisfaction. Altogether, this work is an important first step toward understanding workplace deviance with a person-centered lens. (PsycInfo Database Record (c) 2024 APA, all rights reserved).