The sequential in utero death of heterokaryotic monozygotic twins. A case report and literature review

A case of monozygotic twins in a 19-year-old primigravida is presented. Ultrasound examination at 15 weeks' gestation showed one twin to have a cystic hygroma and hydrops fetalis. The other twin appeared normal. The twins appeared to occupy the same amniotic cavity. Fluid was taken from the cystic hygroma under ultrasound guidance for karyotyping and this showed 45,XO chromosomes. Conservative management was adopted. Serial ultrasound examination showed deteriorating hydrops and at 26 weeks the first twin died. Intensive monitoring of the remaining twin was undertaken with weekly ultrasound, cardiotocography (CTG), and clotting screens. At 29 weeks' gestation the CTG and clotting were normal, but ultrasound revealed that multicystic encephalomalacia had developed in the second twin. A very thin dividing membrane was seen for the first time between the twins. The parents decided to terminate the pregnancy. Prior to an intracardiac potassium chloride injection, a fetal blood sample was taken which revealed 46,XX chromosomes and a normal clotting screen including natural anticoagulant levels. Labour was then induced. Delivery took place 5 h later and the woman made an uneventful recovery. The mechanism for genetic differences between monozygotic twins is discussed and the literature reviewed. A non-disjunction event around the time of splitting of the twins is proposed as the cause. The prognosis for the remaining twin is also discussed, as is the pathogenesis of the cerebral damage.     

Work characteristics, musculoskeletal disorders, and the mediating role of psychological strain: A study of call center employees.

The demands of the modern office are thought to contribute to the development of musculoskeletal disorders. For upper body and lower back disorders, these effects are hypothesized to be mediated by psychological strain. A study of 936 employees from 22 call centers supports this hypothesis. Using logistic regression and structural equation modeling, the authors found that the relationship of workload to upper body and lower back musculoskeletal disorders was largely accounted for by job-related strain. This mediating effect was less evident for arm disorders. Contrary to expectation, job autonomy had neither a direct nor a moderating effect on any musculoskeletal disorder. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Minimizing strain and maximizing learning: The role of job demands, job control, and proactive personality.

Using a sample of 268 production employees, this study extended research on R. Karasek's (1979) demands-control model of stress in 2 ways. First, results show that Karasek's proposed interaction between demands and control when predicting strain occurred only for more proactive employees. This 3-way interaction helps reconcile previous inconsistent findings about the interaction between demands and control when predicting strain. Second, the study extends research by investigating the demands-control interaction and the moderating influence of proactive personality in relation to learning-oriented outcomes (perceived mastery, role breadth self-efficacy, and production ownership). There were no 3-way interactions among the variables when predicting these learning-oriented outcomes, but all were important predictors. These results show (1) that demands and control can influence learning as proposed in the dynamic version of the demands-control model and (2) that proactive personality plays an important moderating role. (PsycINFO Database Record (c) 2010 APA, all rights reserved)