Detection of ligands in regions anatomically connected to neurons expressing the Eph receptor Bsk: potential roles in neuron-target interaction

Neuron-target interaction is a key feature in the establishment of neuronal networks. However, the underlying mechanism remains unclear. We have shown that at the time of target innervation, Bsk, an eph family receptor, is expressed at high levels in several brain regions including the hippocampus, olfactory bulb, and retina. To study whether the ligands are expressed in the target tissues, we investigated the expression of Bsk ligands using a ligand-affinity probe, Bsk-AP, which consisted of the extracellular domain of Bsk fused in frame with a human placental alkaline phosphatase. These analyses showed that the ligands were expressed at high levels in the developing septum, hypothalamus, olfactory neural epithelium, and tectum. In situ hybridization studies revealed that at least three different factors were responsible for the Bsk-AP binding. In the septum, Elf-1, Lerk3 (Eff-2), and AL-1/Lerk7 were transcribed. In the hypothalamus, AL-1/Lerk7 was the ligand detected by Bsk-AP. In the olfactory system, high levels of Lerk3 were detected in the sensory neurons. Both Elf-1 and AL-1/Lerk7 were present in the tectum. These ligand-positive areas are known to be anatomically connected to Bsk-expressing regions. These observations strongly suggest that Bsk and the ligands participate in neuron-target interactions in multiple systems and provide support for their involvement in topographic projection.     

Escherichia coli transcytosis in a Caco-2 cell model: implications in neonatal necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a serious gastrointestinal disorder of preterm infants. Other than an association with prematurity and gastrointestinal feeding, no single factor or mechanism has been consistently linked to this disease. We have previously demonstrated that Escherichia coli isolates obtained from the stool of infants with NEC caused NEC-like injury in a weanling rabbit ileal loop model; this injury, in turn, could be blocked by coinfection with selected Gram(+) bacteria (Enterococcus faecium) isolated from asymptomatic controls. Using Caco-2 cells in a trans-well system, we now demonstrate that the same E. coli isolates can cross epithelial cell monolayers in the absence of ultrastructural change or damage. These results with E. coli contrast with those seen with Salmonella typhimurium, which passed through the monolayer at a higher rate and were associated with striking ultrastructural damage. Transcytosis of E. coli was reduced 3-5-fold in the presence of E. faecium previously shown to block NEC-like injury in the loop model. There was a mild increase in the rate of E. coli transcytosis when studies were conducted with younger, undifferentiated cells; these immature cells had no brush border, had decreased production of brush border-specific enzymes, but retained well defined tight junctions, as demonstrated by transepithelial electrical resistance and electron microscopy. A further reduction/ complete blockage of E. coli transcytosis was observed when E. faecium was used as the coinfectant in studies with these undifferentiated cells. We hypothesize that the ability of E. coli to cross epithelial cell layer is a critical initial step in the cascade of events which lead ultimately to NEC; blockage or reduction in E. coli transcytosis in the presence of certain Gram(+) organisms may play a significant role in prevention of NEC.     

A model for the extended studies of hepatic hemodynamics and metabolism in swine

To our knowledge postoperative hepatic hemodynamics and hepatic metabolism have not been fully studied on a long-term basis. Our goal was to develop a large animal model that would permit the measurement of hepatic blood flow (BF), perihepatic pressures (P), and hepatic metabolism in a long-term setting. Catheters were inserted into the jugular vein, carotid artery, pulmonary artery, hepatic vein, and portal vein (PV) of 27 commercially bred pigs; ultrasonic transit time flowmeter probes were placed around the hepatic artery and PV. Daily postoperative measurements of jugular vein P, carotid artery P, pulmonary artery P, hepatic vein P, and PVP, as well as hepatic artery BF and PVBF, were recorded for 20 days. Hepatic carbohydrate metabolism was assessed by arteriovenous difference techniques. Jugular vein P, pulmonary artery P, hepatic vein P, PVP, and heart rate reached steady-state values during the first week, with a mean +/- SEM of 1.0 +/- 0.3 mm Hg for jugular vein P, 21.4 +/- 2.1 mm Hg for pulmonary artery P, 4.3 +/- 0.4 mm Hg for HVP, 7.8 +/- 0.5 mm Hg for PVP, and 116 +/- 4 beats per minute for heart rate. Mean carotid artery P increased from 65 +/- 3 mm Hg during surgery to 94 +/- 2 mm Hg on postoperative day 1 (P < 0.001) and to a mean 101 +/- 2 mm Hg thereafter. Total hepatic BF reached a steady-state value of 1,132 +/- 187 ml/min by postoperative day 7 (P = 0.19). Over week 1 hepatic artery BF measured as a percentage of total hepatic BF decreased from 35.0 +/- 3.0% to 15.5 +/- 2.7%, and PVBF increased from 65.0 +/- 3.0% to 84.5 +/- 2.7% (P < 0.005); both variables were steady thereafter. In the hemodynamic steady state the net hepatic balances of glucose, lactate, glycerol, and alanine in 5 pigs were 9.9 +/- 4.0, -4.2 +/- 0.4, -2.3 +/- 1.1, and -0.68 +/- 0.22 micromol/kg per min respectively. The net gut (portal-drained viscera) balances of glucose, lactate, alanine, and glycerol were -2.0 +/- 2.5, 1.1 +/- 0.5, 0.73 +/- 0.18, and -0.69 +/- 0.19 micromol/kg per min respectively. Thus, a reliable large animal model was developed to study acute and chronic hepatic hemodynamics and metabolism.     

Esophageal mucosal lesions and scleroderma: prevalence, symptoms and risk factors

There is a strong genetic influence on the susceptibility to celiac disease. Although in the vast majority of patients with celiac disease, the HLA-DQ(alpha1*0501, beta1*0201) heterodimer encoded by the alleles HLA-DQA1*0501 and HLA-DQB1*0201 seems to confer the primary disease susceptibility, it cannot be excluded that other genes contribute to disease susceptibility, as indicated by the difference in concordance rates between monozygotic twins and HLA identical siblings (70% vs. 30%). Obviously other genes involved in the genetic control of T cell mediated immune response could potentially influence susceptibility to celiac disease. The density of T cells using the gammadelta T cell receptor (TCR) is considerably increased in the jejunal epithelium of patients with celiac disease, an abnormality considered to be specific for celiac disease. This suggests an involvement of gammadelta T cells in the pathogenesis of the disease. To ascertain whether the TCR delta (TCRD) gene contributes to celiac disease susceptibility we carried out an association study and genetic linkage analysis using a highly polymorphic microsatellite marker at the TCRD locus on chromosome 14q11.2. The association study demonstrated no significant difference in allele frequencies of the TCRD gene marker between celiac disease patients and controls; accordingly, the relative risk estimates did not reach the level of statistical significance. In the linkage analysis, performed in 23 families, the logarithm of the odds (LOD) scores calculated for celiac disease versus the TCRD gene marker excluded linkage, suggesting that there is no determinant contributing to celiac disease status at or 5 cM distant to the analyzed TCRD gene marker. In conclusion, the results of the present study provide no evidence that the analyzed TCRD gene contributes substantially to celiac disease susceptibility.     

Effects of oleic acid-induced pulmonary edema on lung mechanics

In 25 rabbits anesthetized with pentobarbital sodium and paralyzed with succinylcholine chloride, we investigated the contributions of four factors that might cause the decreased static lung compliance found in oleic acid-induced pulmonary edema: 1) foam, 2) accumulation of fluid in the interstitial spaces, 3) loss of ventilatable units secondary to alveolar flooding, and 4) increased surface tension. Pulmonary edema, reflected by a 115% increase in mean post-mortem extravascular bloodless lung water content, decreased compliance 47% and tripled alveolar-arterial PO2 difference. Removing foam by degassing did not affect compliance measurements. Filling the lungs with saline caused similar changes in control and edematous animals. Because the 38% decrease in functional residual capacity was largely attributable to water accumulation, we concluded that loss of ventilatable units accounted for virtually all the decreased static lung compliance. The role of increased surface tension could not be determined directly but was considered relatively less important.     

Intravenous aminophylline in patients with cystic fibrosis. Pharmacokinetics and effect on pulmonary function

Intravenous aminophylline was administered to ten patients with cystic fibrosis (CF) to determine if the medication would improve pulmonary function and to study theophylline pharmacokinetics. Intravenous normal saline was given on another day as a control. Thoracic gas volume and airway resistance, measured in a volume displacement body plethysmograph, and maximal expiratory flow-volume curves were performed before and after each infusion. No significant improvement was noted in pulmonary function after normal saline infusion. Following aminophylline infusion. Following aminophylline infusion, significant improvement in thoracic gas volume, residual volume, specific airway conductance, and maximal expiratory flow at 60% of total lung capacity was noted. The pharmacokinetic analysis revealed a mean half-life of 4.7 hours, a total clearance of 91 mL/hr/kg, and a volume of distribution of 574 mL/kg. Intravenous aminophylline can acutely decrease airway obstruction in children with CF.     

Implant/bone constructs in femoral neck osteotomy. An autopsy study

Previous studies have suggested that three rather than two screws may give better results in the treatment of femoral neck fractures. In the present study, the strength of various screw/bone constructs in femoral neck osteotomy was analyzed. Transverse osteotomies on 65 cadaver femora were fixed with two or three screws of two types: one with a shank diameter of 6 mm and thread diameter of 8 mm, and a prototype screw with equal shank and thread diameter of 7 mm. The femoral heads were subjected to static and cyclic loads in the one-legged stance position. Single-energy quantitative computed tomography measurements were correlated to load. The two experimental models resulted in different patterns of failure of the bone/implant constructs, otherwise the results were similar. Three of the prototype screws gave the strongest construct, while two of the other screw type were stronger than three. The explanations for the diverging properties of the different bone/implant constructs may be that large threads destroy too much of the bone trabeculae, and that screw threads larger than the shank may destroy the drill canal and produce an unstable situation compared with screws with equal shank and thread diameter.