Strength at the extracellular matrix-muscle interface

Mechanical force is generated within skeletal muscle cells by contraction of specialized myofibrillar proteins. This paper explores how the contractile force generated at the sarcomeres within an individual muscle fiber is transferred through the connective tissue to move the bones. The initial key point for transfer of the contractile force is the muscle cell membrane (sarcolemma) where force is transferred laterally to the basement membrane (specialized extracellular matrix rich in laminins) to be integrated within the connective tissue (rich in collagens) before transmission to the tendons. Connections between (1) key molecules outside the myofiber in the basement membrane to (2) molecules within the sarcolemma of the myofiber and (3) the internal cytoplasmic structures of the cytoskeleton and sarcomeres are evaluated. Disturbances to many components of this complex interactive system adversely affect skeletal muscle strength and integrity, and can result in severe muscle diseases. The mechanical aspects of these crucial linkages are discussed, with particular reference to defects in laminin-alpha2 and integrin-alpha7. Novel interventions to potentially increase muscle strength and reduce myofiber damage are mentioned, and these are also highly relevant to muscle diseases and aging muscle.     

Is abnormal labor associated with shoulder dystocia in nulliparous women?

OBJECTIVE: This study was undertaken to examine the relationship between labor abnormalities and shoulder dystocia in nulliparous women. STUDY DESIGN: Nulliparous women whose delivery was complicated by shoulder dystocia were studied and compared with a control group selected based on the best possible match for race, labor type (spontaneous or induced), and birth weight. The duration of first and second stage of labor, as well as the rates of labor progress, were calculated and compared between groups. RESULTS: During this 4-year study period, there were 8010 nulliparous singleton deliveries of which 65 (0.8%) were complicated by shoulder dystocia. Compared with controls, there was no difference in the rate of cervical dilation in the active phase of the first stage of labor. In the shoulder dystocia group, more patients had a second stage of labor greater than 2 hours (22% vs 3%; P <.05) and had operative vaginal deliveries (26% vs 1.5%; P <.001). In shoulder dystocia cases with birth weight greater than 4000 g, 33% had a second stage of labor greater than 2 hours. CONCLUSION: In our population, the combination of fetal macrosomia, second stage of labor longer than 2 hours and the use of operative vaginal delivery were associated with shoulder dystocia in nulliparous women.     

Prolonged in utero meconium exposure impairs spatial learning in the adult rat : Central Prize Award

Objective

The purpose of this study was to examine the effects of prolonged in utero meconium exposure on adult learning and memory, as measured by the Morris water maze.

Study design

Timed pregnant Long-Evans rats were studied. On gestational day 20 (term, 21 days of gestation), laparotomy was performed, and each maternal animal received an injection of clear amniotic fluid or meconium-stained amniotic fluid into each gestational sac. The laparotomy incision was closed, and the animals received postoperative monitoring through delivery. On postnatal days 145 to 148, the offspring underwent Morris water maze testing. The mean (±SEM) for the latency time was reported for each day's trial and compared between groups.

Results

There were significant differences between meconium-stained amniotic fluid group and clear amniotic fluid group in the mean time to platform on day 1 (82.7 ± 1.8 seconds vs 75.9 ± 3.0 seconds; P = .04), day 2 (60.5 ± 3.5 seconds vs 47. 8 ± 4.6 seconds; P = .03), and day 3 (56.5 ± 4.5 seconds vs 34.7 ± 4.4 seconds; P = .001). However, there were no differences on days 4 and 5. There were also no differences between recall and response learning trials that were done after a 12-day retention period.

Conclusion

In the absence of hypoxia or infection, prolonged in utero meconium exposure is associated with a delay of spatial learning in the adult rat.     

Deletion of laminin-8 results in increased tumor neovascularization and metastasis in mice

Laminin-8 (alpha 4 beta 1 gamma 1) is one of the major laminin isoforms expressed in vascular endothelial basement membranes. Here we show that deletion of laminin-8 in mice affects angiogenesis under pathological conditions. Murine tumor models used in laminin alpha 4-deficient mice results in hyperneovascularization and significant promotion of tumor growth and metastasis. The higher tumor growth rates in mutant mice correlate with decreased tumor cell apoptosis. Depletion of laminin alpha 4 chain may alter the structure of vascular basement membranes, leading to increased angiogenesis. Our data suggest that the laminin-8 plays a critical role in the regulation of pathological angiogenesis.     

Acculturation and cardiovascular disease risk in midlife immigrant women from the former Soviet Union

This study examines relationships among acculturation, depression, and cardiovascular risk factors in midlife women from the former Soviet Union and identifies factors predicting Framingham Risk Scores. Data were collected at baseline and 1 year later from 218 participants in a longitudinal study of postimmigration health. The leading risk factors were obesity, dyslipidemia, and depression. Older women had lower American Behavioral Acculturation subscale scores, higher Russian Behavioral Acculturation subscale scores, and higher depression scores. Length of residence was significantly correlated with American behavioral acculturation but not Russian behavioral acculturation. Baseline body mass index, both acculturation scores, and depression scores predicted Framingham Risk Scores after 1 year, but serum glucose did not. The results suggest that contrary to findings in other immigrant groups, women from the former Soviet Union may decrease their risk for coronary heart disease as they assume a more American lifestyle. Nursing interventions to address the high cardiovascular disease risk in this population are suggested.