Effects of cytochalasin D and latrunculin B on mechanical properties of cells.

Actin microfilaments transmit traction and contraction forces generated within a cell to the extracellular matrix during embryonic development, wound healing and cell motility, and to maintain tissue structure and tone. Therefore, the state of the actin cytoskeleton strongly influences the mechanical properties of cells and tissues. Cytochalasin D and Latrunculin are commonly used reagents that, by different mechanisms, alter the state of actin polymerization or the organization of actin filaments. We have investigated the effect of a wide range of Cytochalasin D and Latrunculin B concentrations (from 40 pM to 10 microM) on the mechanical properties of the cells within fibroblast populated collagen matrices. Contractile force and dynamic stiffness were measured by uniaxial stress-strain testing. The range of effective concentrations of Cytochalasin D (200 pM-2 microM) was broader than that of Latrunculin B (20 nM-200 nM). Activating the cells by serum did not change the effective range of Cytochalasin D concentrations but shifted that of Latrunculin B upward by tenfold. Simple mathematical binding models based on the presumed mechanisms of action of Cytochalasin D and Latrunculin B simulated the concentration-dependent mechanical changes reasonably well. This study shows a strong dependence of the mechanical properties of cells and tissues on the organization and degree of polymerization of actin filaments.

Journal writing as a complementary therapy for reactive depression: a rehabilitation teaching program.

Brief, recurrent, reactive, or situational depression is a common and costly comorbidity that affects chronically ill patients and their family members. This article describes a program that teaches those individuals how to monitor and cope with symptoms of depression by writing daily in a journal. Twenty patients and family members attended teaching sessions at which videotaped scenes of other patients managing symptoms of depression were shown. After viewing the six scenes, participants wrote about their reactions to each scene and listed the emotions they had experienced that were similar to those shown in the tape. They were then asked to record daily for 4 months their emotions and reactions to situations and to also daily self-rate their levels of energy. They were also provided with a list of recommended activities in which to engage when they were depressed. Two psychiatric nurses evaluated the writings and concluded that the program was influential in helping patients and families overcome many emotionally draining reactions to adverse circumstances.

Brief-tone frequency discrimination by children.

This study investigated maturational changes in children's ability to discriminate the frequency of short-duration tone pulses. Frequency difference limens (DLs) were measured for digitally generated 1000-Hz tones with pulse durations of 200, 50, and 20 ms using a two-alternative, two-interval, forced-choice procedure. Participants were 16 5-year-old children; 10 children each in the age categories of 7, 9, and 11 years; and a control group of 10 young adults. Eleven of the 5-year-old children were unable to learn the experimental task. All children in the three older groups and the adults successfully completed the study. The five 5-year-old children who completed the task performed similarly to the 7-year-old children. All groups of participants showed an inverse relationship between duration of the signal and the size of the DL. The DLs at all three tone durations were significantly larger for the 7-year-old children than they were for the older children and adults. There were no significant differences in DL size among the 9-year-old, 11-year-old, and adult subjects at any tone duration. These findings suggest that the sensory and/or cognitive skills required to discriminate the frequency of brief-duration tones may not reach maturity until after age 7 years.

Substance abuse in nursing. Forming policies.

A written policy addressing impaired practice increases the likelihood that all nurses will be treated similarly. It also protects the organization legally. One large Midwestern medical center's approach to policy development, completed after 1 year of task force work, is described.

The impaired nurse. Organizational and professional models of response.

1. Two models of response, organizational and professional, affect the impaired nurse, who is both an employee and a professional. 2. The organizational model of response uses an Employee Assistance Program (EAP) to detect and intervene with impaired employees. 3. The professional model of response involves mechanisms established through the board of nursing, including posttreatment monitoring. 4. When both models are available, linking mechanisms such as coordinators, policies, and reentry practices can combine the strengths of each model.