PubMed · 3318863
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M Rivera-Echegoyen, J Ramírez-Mayans, P Casaubón-Garcín. 1987. [Constipation in children].. https://pubmed.ncbi.nlm.nih.gov/3318863/
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Schwann cells (SCs) that cap neuromuscular junctions (nmjs) play roles in guiding nerve terminal growth in paralyzed and partially denervated muscles; however, the role of these cells in the day-to-day maintenance of this synapse is obscure. Neuregulins, alternatively spliced ligands for several erbB receptor tyrosine kinases, are thought to play important roles in cell-cell communication at the nmj, affecting synapse-specific gene expression in muscle fibers and the survival of terminal SCs during development. Here we show that application of a soluble neuregulin isoform, glial growth factor II (GGF2), to developing rat muscles alters terminal SCs, nerve terminals, and muscle fibers. SCs extend processes and migrate from the synapse. Nerve terminals retract from acetylcholine receptor-rich synaptic sites, and their axons grow, in association with SCs, to the ends of the muscle. These axons make effective synapses only after withdrawal of GGF2. These synaptic alterations appear to be induced by the actions of neuregulin on SCs, because SC transplants growing into contact with synaptic sites also caused withdrawal of nerve terminal branches. These results show that SCs can alter synaptic structure at the nmj and implicate these cells in the maintenance of this synapse.
Activation of the NMDA subtype of glutamate receptor is required for activity-dependent structural plasticity in many areas of the young brain. Previous work has shown that NMDA receptor currents decline approximately at the time that developmental synaptic plasticity ends, and in situ hybridization studies have suggested that receptor subunit changes may be occurring during the same developmental interval. To establish a system in which the relationship between these properties of developing synapses can be explored, we have combined patch-clamp recordings with mRNA- and protein-level biochemical analyses to study the developmental regulation of NMDA receptors in the superficial layers of the rat superior colliculus. These experiments document an abrupt decrease in the NMDA receptor contribution to synaptic currents that occurs before eye opening and is closely associated with changes in NR1 protein, rapidly rising levels of the NMDA receptor subunit NR2A, and decreasing levels of NR2B. The functional and molecular changes also are correlated with the developmental decline in structural plasticity in these layers. In addition, both physiological and biochemical methods show evidence of GABA-mediated inhibition in the superficial collicular layers beginning after eye opening. This may provide an additional heterosynaptic mechanism for controlling excitation and plasticity in this neuropil by pattern vision. Thus our findings lend support to the idea that high levels of NMDA receptor function are associated with the potential for structural rearrangement in CNS neuropil and that the functional downregulation of this molecule results, at least partially, from changes in its subunit composition.
BACKGROUND: Women with coronary artery disease are treated differently than men. Although mortality has been studied, functional outcomes for women and men have not been prospectively compared. METHODS: The Manitoba Health Reform Impact Study used hospital databases to identify all residents aged 45 years and older in Manitoba who were hospitalized for a myocardial infarction between October 1, 1991, and September 30, 1992. Cohort members were interviewed twice, an average of 16 and 25 months after hospitalization. Baseline and follow-up measures included treatments (eg, physician visits, diagnostic testing, revascularization, and cardiac medications), physical health status (physical component summary [PCS] score derived from the Medical Outcomes Study Short Form 36), reinfarction, and mortality. RESULTS: Of the 820 patients who completed the initial survey, 31 died during the follow-up period, and 734 completed the follow-up survey. Data were complete for the primary outcome (PCS score) and all relevant covariates for the 677 patients who were included in this study Women constituted 34% of this cohort. Although women had more physician visits during follow-up, they were less likely to have undergone treadmill testing or angiography (odds ratio, 0.68; 95% confidence interval, 0.46-0.99). Women were equally likely to report taking beta-adrenergic blocking agents, but were less likely than men to report the use of aspirin (odds ratio, 0.69; 95% confidence interval, 0.48-0.98). After adjusting for baseline differences in PCS scores, age, income, social supports, and the levels of angina and dyspnea, the PCS score for women declined by 1.4 points, while the score for men improved by 0.2 points (P = .03). During the follow-up period, reinfarction and mortality rates were low overall, but were not different in men and women. CONCLUSIONS: In this cohort of patients with known coronary artery disease, we found less aggressive treatment of coronary artery disease and less use of aspirin among women than among men during 1 year of observation. After controlling for baseline differences, women with coronary artery disease experienced a more rapid decline in physical health status than did men during 1 year of follow-up.