Use of baclofen for withdrawal in a preterm infant.

Baclofen is a gamma-aminobutyric acid agonist used primarily as a muscle relaxant to treat spasticity in children and adults. Withdrawal of oral baclofen is known to cause a withdrawal syndrome in adults. Only one previous case describes a withdrawal syndrome in a term infant, manifested by seizures, associated with the use of oral baclofen in the mother. This case describes a withdrawal syndrome and the unique use of baclofen for withdrawal in a preterm infant.

Cultures, genes, and neurons in the development of song and singing in brown-headed cowbirds (Molothrus ater).

In brown-headed cowbirds, Molothrus ater, as in many songbird species, vocalizations are fundamental to reproduction. In our studies, experiments utilizing different social housing regimes and geographic comparisons have indicated the social learning of males' vocalizations and associated abilities to use vocalizations effectively during the breeding season. Here, we describe studies indicating roles of cultural and genetic background, and of social influences from females, on male vocal development. These influences can interact with neural regions, including song learning and song control nuclei, but also visual-processing nuclei, in the development of signaling. We argue that a developmental systems approach to the study of vocal behavior provides a structure to organize these different influences and how they may interact with one another over development. A systems approach requires that researchers study the social context in which signals and signalers develop - both the ontogenetic arena in which young animals learn their signals from older animals, and the functional arena in which young and older animals socially interact with one another.

Response to high frequency jet ventilation may predict the need for extracorporeal membrane oxygenation.

The aim of this study was to determine predictors of response whilst using high frequency jet ventilation (HFJV) for infants in intractable respiratory failure, in order to avoid the utilization of extracorporeal membrane oxygenation (ECMO). We reviewed patient demographics, ventilator parameters, blood gas values, length of oxygen therapy and use of surfactant and outcome, in infants given a 4 h trial of HFJV as the minimum to eliminate those infants where HFJV is used as a bridge to ECMO. The study was carried out in the neonatal intensive care nursery at Kosair Children's Hospital in Louisville, Kentucky, which provides high frequency ventilation and ECMO. Thirty infants who were eligible for ECMO and who met the study criteria were divided into two groups based upon response to HFJV. Twenty two infants responded to HFJV and eight nonresponders required ECMO after a trial of HFJV. Infants responding during HFJV demonstrated a significant decrease in oxygenation index without an escalation of mean airway pressure within 4 h after the initiation of HFJV. These infants had lower birth weights and an increased incidence of respiratory distress syndrome. No statistical differences were found in length of ventilation, days of oxygen therapy or duration of HFJV between the groups. Infants in intractable respiratory failure, who are eligible for extracorporeal membrane oxygenation, should receive a trial of high frequency jet ventilation, especially if the cause is respiratory distress syndrome unresponsive to surfactant therapy. During high frequency jet ventilation, the oxygenation index and mean airway pressure should be monitored serially, since they may predict the need for extracorporeal membrane oxygenation.

Intravenous gamma-glutamyl-tyrosine elevates brain tyrosine but not catecholamine concentrations in normal rats.

A number of clinical situations may benefit from intravenous supplements of tyrosine (Tyr). In total parenteral nutrition (TPN), the supply of Tyr is limited by its poor solubility. In both rats and infants maintained on pediatric TPN, plasma Tyr levels are approximately 30% of normal, and in rat brains Tyr concentrations are similarly reduced. We reported previously that supplementing a TPN solution with the soluble peptide, gamma-glutamyl-Tyr [Glu(Tyr)], normalizes plasma Tyr and doubles brain Tyr in rats. To assess more fully the behavior of intravenous Glu(Tyr) in vivo, 20 mmol/L Glu(Tyr) was infused into the inferior vena cava of rats at rates increased every 2 hours over an 8-hour period (300 to 450 mumol Glu(Tyr)/kg body weight/h). The surgical procedure for catheterization is described. At the maximum rate of infusion, plasma Tyr and Glu(Tyr) concentrations reached mean plateau values of 326 and 252 mumol/L, respectively. Brain Tyr concentrations were 71 and 264 nmol/g wet weight in control rats infused with heparinized saline (SAL group) and rats infused with Glu(Tyr) (PEP group) respectively. No differences were found in concentrations of norepinephrine (NE), dopamine (DA), or homovanillic acid (HVA) in prefrontal cortex (PFC), striatum (STR), or remaining brain (RB) tissue in PEP and SAL rats. We did not detect undergraded Glu(Tyr) in the brain, and less than 0.5% of infused Glu(Tyr) appeared in the urine.

Use of the soluble peptide gamma-L-glutamyl-L-tyrosine to provide tyrosine in total parenteral nutrition in rats.

Limited solubility restricts amounts of tyrosine (Tyr) in amino acid solutions used in total parenteral nutrition (TPN). Excess phenylalanine (Phe) is included in TPN for conversion to Tyr by liver Phe hydroxylase. However, this conversion is limited, especially in infants. We have confirmed that infants receiving TPN have low Tyr concentrations and high Phe/Tyr ratios in plasma compared with published values for enterally fed neonates. Tyr is important in the synthesis of proteins and other biomolecules, including catecholamines in the brain. We tested the soluble peptide gamma-glutamyl-tyrosine (Glu(Tyr)) as a possible precursor of Tyr in TPN. Groups of five rats were given infusions of TPN containing an amino acid mixture simulating a commercial formulation (group A), TPN in which Glu(Tyr) was substituted for half the Phe in the group A solution) (group B), or saline (group C). Control animals (group C) were fed rodent chow. Blood was sampled at 0 time and daily for 4 days. Brains were collected at 96 hours, and aromatic amino acids in plasma and brains were measured by high-performance liquid chromatography. Throughout the experiment, plasma of animals in group A had significantly elevated Phe and reduced Tyr concentrations compared with control values; plasma concentrations in groups B and C were similar. In groups A and B, brain Tyr levels were 31% and 63% of control values, respectively. In group B, Glu(Tyr) was not detected in brains. These data suggest that supplementing current TPN mixtures with Glu(Tyr), which is stable in solution, can produce normal plasma Tyr concentrations and Phe/Tyr ratios and improve the supply of Tyr to the brain.

Evolutionary relationships of the salmonid fish genus Salvelinus inferred from DNA sequences of the first internal transcribed spacer (ITS 1) of ribosomal DNA.

DNA sequences of the ribosomal DNA (rDNA) first internal transcribed spacer region (ITS 1) of six species of the salmonid fish genus Salvelinus (alpinus, malma, confluentus, leucomaenis, fontinalis, and namaycush) and the closely related species Hucho perryi were determined. Phylogenetic analysis of the aligned sequences by both phenetic and cladistic methods with H. perryi as an outgroup generated one best topology which pairs S. alpinus with S. malma as the most recently derived species, and pairs S. confluentus with S. leucomaenis. Three other possible topologies favor the pairing of S. namaycush and S. fontinalis, with one tree placing them on separate branches, and vary the branching order of the interior groups. These results agree with previous studies based on comparisons of morphologies, isozymes, karyotypes, and restriction sites showing a close genetic relationship and possible hybridization between the members of this genus.