Keratinocytes as Depository of Ammonium-Inducible Glutamine Synthetase: Age- and Anatomy-Dependent Distribution in Human and Rat Skin

In inner organs, glutamine contributes to proliferation, detoxification and establishment of a mechanical barrier, i.e., functions essential for skin, as well. However, the age-dependent and regional peculiarities of distribution of glutamine synthetase (GS), an enzyme responsible for generation of glutamine, and factors regulating its enzymatic activity in mammalian skin remain undisclosed. To explore this, GS localization was investigated using immunohistochemistry and double-labeling of young and adult human and rat skin sections as well as skin cells in culture. In human and rat skin GS was almost completely co-localized with astrocyte-specific proteins (e.g. GFAP). While GS staining was pronounced in all layers of the epidermis of young human skin, staining was reduced and more differentiated among different layers with age. In stratum basale and in stratum spinosum GS was co-localized with the adherens junction component ß-catenin. Inhibition of, glycogen synthase kinase 3β in cultured keratinocytes and HaCaT cells, however, did not support a direct role of ß-catenin in regulation of GS. Enzymatic and reverse transcriptase polymerase chain reaction studies revealed an unusual mode of regulation of this enzyme in keratinocytes, i.e., GS activity, but not expression, was enhanced about 8–10 fold when the cells were exposed to ammonium ions. Prominent posttranscriptional up-regulation of GS activity in keratinocytes by ammonium ions in conjunction with widespread distribution of GS immunoreactivity throughout the epidermis allows considering the skin as a large reservoir of latent GS. Such a depository of glutamine-generating enzyme seems essential for continuous renewal of epidermal permeability barrier and during pathological processes accompanied by hyperammonemia

Percutaneous insertion of subclavian venous catheters in infants and children.

All attempts at subclavian venous catheterization by the Pediatric Surgery Service done during a one and one-half year period at the Children\u27s Hospital of Los Angeles were prospectively studied. Catheterization was attempted in 107 patients with a mean age of 9.8 years. Cannulation of the vein was successful 89 times (71 per cent) with the major complications being arterial puncture (8.0 per cent), pneumothorax (2.4 per cent) and abnormal position (12.8 per cent). Fluoroscopy was a valuable adjunct when used, resulting in an 86 per cent success rate. The serious complication rate was similar between left and right-sided attempts, but more catheters were abnormally positioned during right-sided attempts (15.7 versus 5.2 per cent). Percutaneous insertion of subclavian venous catheters can be accomplished in infants and children with low morbidity. Cannulation of the left subclavian vein can be accomplished with a similar success rate and a lower malposition rate than the right side. Fluoroscopy is a useful tool to assist in the correct placement of the catheter

Neonatal lipid utilization increases with injury severity: Recombinant human growth hormone versus placebo

Increased lipid oxidation has been observed in injured adult and pediatric patients who receive growth hormone (GH). In infants, whose bodies make fat more readily (de novo lipogenesis), this effect has not been tested. After surgery for necrotizing enterocolitis or gastroschisis, 22 neonates (average gestational age, 35 weeks; average postnatal age, 7 days) were provided basal protein-calorie parenteral repletion, and were prospectively randomized to receive either recombinant human GH (rhGH, 0.2 mg/kg/d) or placebo for 6 days. Injury severity was established by serial serum C- reactive protein (CRP) levels (high v low stress: CRP ≤ 6.0 mg/dL v \u3c 6.0 mg/dL). Indirect calorimetry was used to measure energy expenditure (MEE), respiratory quotient (RQ), net lipid oxidation (Fe), and lipid oxidative O2 consumption (V̇O2f). Among the GH+ group, MEE, Fe, and V̇O2f were significantly higher for the high-stress patients (MEE: 52.87 ± 13.35 v 42.57 ± 9.47 kcal/kg/d; P \u3c .03; Fe: 18.32 ± 27.74 v 0.81 ± 13.47 kcal/kg/d; P \u3c .02; V̇O2f: 7.21 ± 9.86 v 0.01 ± 7.42 L/d, P \u3c .02), and RQnp was significantly lower in the high-stress patients (RQnp: 0.93 ± 0.14 v 1.05 ± 0.11; P \u3c .02). In addition, Fe and RQnp were directly proportional to carbohydrate intake (CHO) in the high-stress patients (CHO to Fe: Pearson r = -.701; CHO to RQnp: Pearson r = .714; P \u3c .05). Lipid oxidation was directly proportional to stress severity, was higher in the GH group (18.32 v 11.91 kcal/kg/d for the placebo group), and was depressed in response to increased CHO intake in all groups. Lipid is an important energy source in acutely injured, especially severely stressed neonates. Lipid substrate utilization is improved with GH supplementation during acute metabolic stress. In addition, excess carbohydrate delivery reduces the amount of lipid utilized for energy metabolism. An appropriately balanced, mixed-fuel formula should be used for caloric repletion in this infant population