Mental Health Problems and Their Association With Internet Use in Medical Residents.

Objectives: Mental health problems (MHP) among medical residents are often found in clinical settings and sometimes lead to professional lapses. Evidence suggests that excessive Internet use is associated with MHP. We investigated the MHP of residents (depression, anxiety, and self-esteem) and their association with Internet use using a longitudinal design. Methods: Participants were 208 residents. The General Health Questionnaire (GHQ), Patient Health Questionnaire (PHQ), and the Rosenberg Self-Esteem Scale (RSES) were used to assess anxiety, depression, and self-esteem. The Generalized Problematic Internet Use Scale 2 (GPIUS2) was used to measure Internet use. Data were obtained twice, at baseline and 3 months later when the risk of MHP in residency is highest. Results: Residents with MHP (N = 36) had higher GHQ scores than those without MHP (N = 172) at follow-up. Residents with MHP had more depression and less self-esteem than those without MHP at baseline and follow-up. GPIUS2 total scores, and scores on the subscale preference for online social communication, were higher in residents with MHP. Preference for online social communication at follow-up was positively correlated with depression at baseline and follow-up, and negatively correlated with self-esteem at follow-up. Conclusions: Depression and self-esteem may predict Internet use when the risk of MHP is greatest for residents, indicating potential risks of excessive Internet use or Internet use as a compensatory coping behavior. Together with depression and self-esteem assessment, Internet use may be a useful index of resident mental health.

Rapid Recovery Double Cross-Linking Hydrogel with Stable Mechanical Properties and High Resilience Triggered by Visible Light.

The designed tough hydrogels, depending on energy dissipation mechanism, possess excellent biocompatibility, stimuli-responsiveness, and outstanding mechanical properties. However, the application of hydrogels is greatly limited in actuators and sensors for the lack of instantaneous recovery and resilience. In this work, we synthesized a double cross-linking poly(acrylic acid) hydrogel via a simple, one-pot, visible-light-trigger polymerization, with carboxymethyl cellulose as initiator and the first cross-linker, N,N'-methylene bis(acrylamide) (MBA) as the second cross-linker. The tensile strength and elastic modulus are in the range of 724-352 kPa and 115-307 kPa, respectively, depending on the MBA content. The swelling ratio of hydrogels dramatically decreased with increasing the MBA content. DMA results indicate that the internal friction between molecules within the hydrogel decreases with the increase of MBA content. Cyclic tensile tests show that after the structure stabilizes, the resilience, maximum stress, and residual strain of Gel-2 maintains over 93% (95% for successive cyclic tensile test), 115 kPa and less than 3%, respectively, at a strain of 125%. The values of resilience and residual strain are almost constant in both successive and intermittent cyclic tensile tests. Moreover, the swollen hydrogel has higher resilience and lower residual strain than the same hydrogel in the as-prepared state.

Actin stress fibers are at a tipping point between conventional shortening and rapid disassembly at physiological levels of MgATP.

Stress fibers (SFs) composed of nonmuscle actin and myosin II play critical roles in various cellular functions such as structural remodeling in response to changes in cell stress or strain. Previous studies report that SFs rapidly disassemble upon loss of tension caused by reduced myosin activity or sudden cell shortening, but the mechanism is unclear. Here, we showed that Rho-kinase inhibition with Y-27632 led to detachment of intact actin filaments from the SFs rather than depolymerization. Loss of tension may allow SFs to shorten via MgATP-driven cross-bridge cycling, thus we investigated the effects of MgATP concentration on SF shortening and stability. We performed the experiments using extracted SFs to allow control over MgATP concentration. SF contraction and disassembly rates each increased with increasing MgATP concentration. SFs transitioned from conventional SF shortening to rapid disassembly as MgATP concentration increases from 2 to 5mM, which is within the physiological range of intracellular MgATP concentrations. Thus, we submit that SFs in intact cells are inherently on the verge of disassembly, which is likely due to the small number of actomyosin cross-bridges in SFs compared to those found in relatively stable myofibrils. Given that recent studies have revealed that loss of resistive force against myosin II could lower the fraction of the MgATPase cycle time that the myosin head is attached to actin (i.e., the duty ratio), binding of cytoplasmic levels of MgATP to myosin II may be sufficient to cause the disassembly of unloaded SFs. The present study thus describes a putative mechanism for rapid SF disassembly caused by decreased myosin activity or sudden cell shortening.

Attenuation of store-operated Ca2+ entry and enhanced expression of TRPC channels in caudal artery smooth muscle from Type 2 diabetic Goto-Kakizaki rats.

1. Previously, we found that Ca(2+) entry from the extracellular space via alpha(1)-adrenoceptor-activated, Ca(2+)-permeable channels, but not voltage-gated Ca(2+) channels, is impaired in endothelium-denuded caudal artery smooth muscle from Type 2 diabetic Goto-Kakizaki (GK) rats. In the present study, we investigated the impairment of Ca(2+) entry mechanisms via Ca(2+)-permeable channels from the extracellular space in response to alpha(1)-adrenoceptor stimulation (cirazoline) in endothelium-denuded caudal artery strips isolated from GK rats. 2. The contraction of caudal artery strips from GK rats in response to the sarcoplasmic reticulum Ca(2+)-ATPase inhibitor cyclopiazonic acid (10 micromol/L), which causes depletion of Ca(2+) stores and subsequent store-operated Ca(2+) (SOC) entry, was significantly depressed compared with that of Wistar rats (maximal force 0.023 +/- 0.004 vs 0.058 +/- 0.005 mN/mg tissue wet weight, respectively). These results suggest that receptor-activated Ca(2+) entry through SOC channels is impaired in caudal artery smooth muscle in GK rats. 3. The classic transient receptor potential (TRPC) channels, which constitute SOC and receptor-operated cation channels, play an important role in Ca(2+) regulation. Therefore, we investigated the mRNA and protein expression of TRPC channels in caudal artery smooth muscle from Wistar and GK rats using reverse transcription-polymerase chain reaction and immunoblotting. 4. Expression of TRPC1, TRPC3 and TRPC6 mRNA and protein was found in Wistar rats. However, in GK rats, in addition to the expression of these TRPC channels, mRNA and protein expression of TRPC4 was found. The expression of TRPC1 and TRPC6, but not TRPC3, was increased approximately twofold in GK rats compared with Wistar rats. 5. These results suggest that changes in TRPC channel expression may be responsible, in part, for the dysfunction of receptor-mediated Ca(2+) entry in caudal artery smooth muscle of GK rats.

Impairment of α1-adrenoceptor-mediated contractile activity in caudal arterial smooth muscle from type 2 diabetic Goto-Kakizaki rats.

1. In the present study, we compared the responsiveness of de-endothelialized caudal artery smooth muscle strips, isolated from Type 2 diabetic Goto-Kakizaki (GK) and normal Wistar rats, to alpha(1)-adrenoceptor stimulation (cirazoline) and membrane depolarization (K(+)). 2. The contractile and myosin 20 kDa light chain (LC(20)) phosphorylation responses to 0.3 micromol/L cirazoline of caudal artery strips isolated from 12-week-old GK rats were significantly reduced compared with those of age-matched Wistar rats, whereas the contractile and LC(20) phosphorylation responses to 60 mmol/L K(+) were unaltered. 3. Stimulation of fura 2-AM-loaded strips from GK rats with 0.3 micromol/L cirazoline induced a significantly smaller rise in [Ca(2+)](i) (by approximately 20%) compared with that in strips from Wistar rats, whereas comparable Ca(2+) transients were evoked by K(+) in both. 4. Using quantitative polymerase chain reaction, no significant differences were detected in the mRNA expression of alpha(1A)-, alpha(1B)- and alpha(1D)-adrenoceptor subtypes between GK and Wistar rats. 5. Cirazoline (1 micromol/L)- and caffeine (20 mmol/L)-induced contractions in the absence of extracellular Ca(2+) were unaltered in GK rats, suggesting that the release of Ca(2+) from the sarcoplasmic reticulum in response to cirazoline does not differ between GK and Wistar rats. 6. The results of the present study suggest that Ca(2+) entry from the extracellular space via alpha(1)-adrenoceptor-activated, Ca(2+)-permeable channels, but not via membrane depolarization and voltage-gated L-type Ca(2+) channels, is impaired in caudal artery smooth muscle of GK rats.

Effects of frequency of pulsatile flow on morphology and integrin expression of vascular endothelial cells.

Endothelial cells are known to adapt their morphology and functions in response to different types of fluid flow. In vivo, endothelial cells are exposed to varying frequencies of pulsatile flow. Therefore, in this study, the effects of frequency of pulsatile flow on morphology and alpha v beta 3 integrin expression of bovine aortic endothelial cells (BAEC) were investigated. A newly developed flow-system was used to apply pulsatile flow at frequencies of 0.5, 1.0, and 1.5 Hz to BAEC for 12 h. At 1.0 Hz, the expression of alpha v beta 3 integrin was significantly higher at the central regions of cells than at the upstream regions. In contrast, at 0.5 and 1.5 Hz, the expression of alpha v beta 3 integrin was significantly higher at the upstream regions than at the central regions. Morphological observation revealed that BAEC under pulsatile flow frequencies of 0.5 and 1.0 Hz exhibited elongated morphologies and oriented with the direction of flow. In addition, stress fibers developed parallel to the cell major axis. Similar results were obtained under steady flow conditions. In contrast, BAEC under 1.5 Hz elongated but with a random orientation. These results suggest that BAEC morphology and integrin expression may be modulated by the frequency of pulsatile flow. In particular, BAEC exposed to 1.5 Hz pulsatile flow may not be able to align with the direction of flow, possibly indicating the presence of a critical value for living systems.

Free-floating left atrial ball thrombus without mitral valve disease.

Reports of left atrial ball thrombus without mitral valve disease are few. We experienced a case of free-floating left atrial ball thrombus that developed in a short period in a patient with atrial fibrillation and dilated left atrium but intact mitral valve. Surgical removal of the thrombus was performed. It was presumed that atrial fibrillation and enlarged left atrium were the contributory factors to thrombus development.