ABSTRACT. Permeability of the blood brain barrier (BBB) for bilirubin and '2SI-albumin was studied in 2-dand 2-wk-old piglets. '251-albumin was given by bolus at the beginning of each study. Hyperbilirubinemia was produced by an initial bolus infusion of bilirubin and sustained at a plasma bi1irubin:albumin molar ratio of approximately 1.0 by continuous infusion of bilirubin for 3 h. During the study period, arterial pH and blood gas tensions, serum osmolarity, and mean arterial blood pressure were within the physiologic range for age in both groups. Serum albumin and serum total and unbound bilirubin concentrations were higher in the 2-wk-old piglets. Brain bilirubin concentrations and permeability ( P . S product) of the BBB for bilirubin were higher in the 2-d-old than in the 2-wk-old piglets, but the values of P . S for albumin were not different between the two groups. In 2-d-old piglets, regional brain bilirubin concentrations and permeability of the BBB were higher in subcortical regions (cerebellum and brainstem) than in the cerebral cortex. Regional brain albumin concentrations and BBB permeability to albumin in 2-d-old piglets were higher only in the cerebellum. In all regions, the bi1irubin:albumin molar ratio was higher in the brain tissues than in the blood. In 2-wk-old piglets, the brain concentrations and P . S products for bilirubin were lower and the regional differences were less marked than for 2-d-old animals. We conclude that in 2-d-old piglets the blood brain barrier is more permeable to bilirubin than to albumin, that brainstem and cerebellum are more permeable to bilirubin than cortical regions, and that by 2 wk the permeability of the BBB to bilirubin decreases while permeability to albumin remains unchanged. (Pediatr Res 25:452-456, 1989) Abbreviations BBB, blood brain barrier P . S, permeability. surface area Hyperbilirubinemia is one of the most common problems in the newborn infant. Although the mechanism of bilirubin toxicity is not fully understood, kernicterus may result from the entry of the unbound fraction of unconjugated bilirubin into the brain (1, 2). Because in sick infants kernicterus can occur at very low levels of total serum bilirubin (1-3), it is also possible that immaturity of the blood-brain barrier or injury to it may allow entry of bilirubin into the brain (3-6). In most species of animals, hyperbilirubinemia alone fails to cause kernicterus (4-6), even at very high serum bilirubin concentrations (4-6). Kernicterus occurs more readily in asphyxiated animals (4) or in Gunn rats treated with sulfisoxazole (7). The free bilirubin theory as the sole explanation of kernicterus in low birth wt infants has also been challenged by recent observations that hyperosmolar opening of the BBB for albumin-bound bilirubin might play a role in the pathogenesis of kernicterus with serum bilirubin levels below the range of a saturated bilirubin capacity (6,8,9).Ehrlich introduced the concept of a blood brain banier when he reported in 1885 that aniline dyes injected into the blo...
The neuropeptide small cardioactive peptide (SCP) plays an integrative role in exciting various motor programs involved in feeding and locomotion in a number of gastropod species. In this study, immunohistochemistry, using monoclonal antibodies against SCPB, was used to localize SCPB-like-immunoreactive neurons in the central nervous system, and map their connections to various tissues, in the nudibranch, Melibe leonina. Approximately 28-36 SCPB-like-immunoreactive neurons were identified in the M. leonina brain, as well as one large neuron in each of the buccal ganglia. The neuropil of the pedal ganglia contained the most SCPB-like-immunoreactive varicosities, although only a small portion of these were due to SCPB-like-immunoreactive neurons in the same ganglion. This suggests that much of the SCPB-like immunoreactivity in the neuropil of the pedal ganglia was from neurons in other ganglia that projected through the pedal-pedal connectives or the connectives from the cerebral and pleural ganglia. We also observed extensive SCPB innervation along the length of the esophagus. Therefore, we investigated the impact of SCPB on locomotion in intact animals, as well as peristaltic contractions of the isolated esophagus. Injection of intact animals with SCPB at night led to a significant increase in crawling and swimming, compared to control animals injected with saline. Furthermore, perfusion of isolated brains with SCPB initiated expression of the swim motor program. Application of SCPB to the isolated quiescent esophagus initiated rhythmic peristaltic contractions, and this occurred in preparations both with and without the buccal ganglia being attached. All these data, taken together, suggest that SCPB could be released at night to arouse animals and enhance the expression of both feeding and swimming motor programs in M. leonina.
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