Ethnic/racial diversity, maternal stress, lactation and very low birthweight infants.

OBJECTIVE: (1) To compare maternal characteristics and psychological stress profile among African-American, Caucasian and Hispanic mothers who delivered very low birthweight infants. (2) To investigate associations between psychosocial factors, frequency of milk expression, skin-to-skin holding (STS), and lactation performance, defined as maternal drive to express milk and milk volume. STUDY DESIGN: Self-reported psychological questionnaires were given every 2 weeks after delivery over 10 weeks. Milk expression frequency, STS, and socioeconomic variables were collected. RESULT: Infant birthweight, education, and milk expression frequency differed between groups. Trait anxiety, depression and parental stress in a neonatal intensive care unit (PSS:NICU) were similar. African-American and Caucasian mothers reported the lowest scores in state anxiety and social desirability, respectively. Maternal drive to express milk, measured by maintenance of milk expression, correlated negatively with parental role alteration (subset of PSS:NICU) and positively with infant birthweight and STS. Milk volume correlated negatively with depression and positively with milk expression frequency and STS. CONCLUSION: Differences between groups were observed for certain psychosocial factors. The response bias to self-reported questionnaires between groups may not provide an accurate profile of maternal psychosocial profile. With different factors correlating with maintenance of milk expression and milk volume, lactation performance can be best enhanced with a multi-faceted intervention program, incorporating parental involvement in infant care, close awareness and management of maternal mental health, and encouragement for frequent milk expression and STS.

Diversity of neuronal connexins in the mammalian retina

Many neurons in the mammalian retina are electrically coupled by intercellular channels or gap junctions, which are assembled from a family of proteins called connexins. Numerous studies indicate that gap junctions differ in properties such as conductance and tracer permeability. For example, A-type horizontal cell gap junctions are permeable to Lucifer Yellow, but B-type horizontal cell gap junctions are not. This suggests the two cell types express different connexins. My hypothesis is that multiple neuronal connexins are expressed in the mammalian retina in a cell type specific manner. Immunohistochemical techniques and confocal microscopy were used to localize certain connexins within well-defined neuronal circuits. The results of this study can be summarized as follows: AII amacrine cells, which receive direct input from rod bipolar cells, are well-coupled to neighboring AIIs. In addition, AII amacrine cells also form gap junctions with ON cone bipolar cells. This is a complex heterocellular network. In both rabbit and primate retina, connexin36 occurs at dendritic crossings in the AII matrix as well as between AIIs and ON cone bipolar cells. Coupling in the AII network is thought to reduce noise in the rod pathway while AII/bipolar gap junctions are required for the transmission of rod signals to ON ganglion cells. In the outer plexiform layer, connexin36 forms gap junctions between cones and between rods and cones via cone telodendria. Cone to cone coupling is thought to reduce noise and is partly color selective. Rod to cone coupling forms an alternative rod pathway thought to operate at intermediate light intensity. A-type horizontal cells in the rabbit retina are strongly coupled via massive low resistance gap junctions composed from Cx50. Coupling dramatically extends the receptive field of horizontal cells and the modulation of coupling is thought to change the strength of the feedback signal from horizontal cells to cones. Finally, there are other coupled networks, such as B-type horizontal cells and S1/S2 amacrine cells, which do not use either connexin36 or Cx50. These results confirm the hypothesis that multiple neuronal connexins are expressed in the mammalian retina and these connexins are localized to particular retinal circuits. ^