A comparison of scholastic and collegiate longsnapping techniques.

The purpose of this study was to identify the differences that exist between collegiate (CS) and scholastic (SS) longsnappers. Six CS (21.4 +/- 1.37 years) and 7 SS (16.7 +/- 1.11 years) longsnappers were filmed performing 10 longsnaps each. The CS and SS longsnappers had 7.0 +/- 0.89 and 2.7 +/- 0.95 years experience longsnapping, respectively. Each of the 10 longsnaps for all subjects were analyzed for takeoff velocity and accuracy. The snap that most closely approximated the individual snapper's median values for takeoff velocity and accuracy was digitized using a 20-point model. CS were both faster (0.85 +/- 0.10 seconds vs. 1.25 +/- 0.19 seconds) and more accurate in terms of mean radial error (29.36 +/- 8.4 cm vs. 47.2 +/- 8.26 cm) than their SS counterparts. These differences were related to body positioning both before and during the longsnap. CS exhibited more shoulder flexion (135 +/- 6.33 degrees ; vs. 98 +/- 9.01 degrees ) and greater elbow extension (133 +/- 8.1 degrees vs. 95 +/- 6.77 degrees ) in the set position phase, along with greater center of mass movement (0.27 +/- 0.02 m vs. 0.14 +/- 0.04 m) in the anterior-posterior direction and less hip flexion (72 +/- 1.85 degrees vs. 49 +/- 9.42 degrees ) during the preflight phase. Longsnapping experience and accuracy were significantly related (r = -0.82, p < 0.05). These results suggest that body positioning both before and during the longsnap motion significantly influence the velocity and accuracy of the longsnap.

Mechanisms of gastroesophageal reflux in healthy premature infants.

OBJECTIVES: The aim of this study was to characterize the motor events responsible for gastroesophageal reflux (GER) and esophageal acid clearance in a cohort of healthy preterm infants. STUDY DESIGN: Esophageal motility was recorded for 2 to 3 hours after a feeding in 24 preterm infants, 31 to 38 weeks' postmenstrual age, by using a sleeveside hole micromanometric assembly incorporating a pH probe. RESULTS: Sixty acid GER episodes were recorded by pH probe, and 133 non-acid GER episodes were recorded manometrically by the presence of esophageal common cavities. Of the 193 GER episodes, 159 (82%) were associated with transient lower esophageal sphincter relaxation (TLESR). TLESRs were significantly longer in duration than single swallows (15.1 seconds vs 5.6 seconds, P < .001) and had lower nadir pressures (0.8 mm Hg vs 2.3 mm Hg, P < .001). A total of 3216 esophageal body pressure waves were analyzed; 70% of swallow-induced pressure waves were peristaltic in sequence compared with 5% of swallow-unrelated pressure waves. During periods of esophageal acidification (pH below 4), peristaltic esophageal body pressure wave sequences cleared acid refluxate more effectively than nonperistaltic pressure wave sequences. CONCLUSIONS: In healthy preterm infants, TLESRs are the predominant mechanism underlying GER, and esophageal clearance mechanisms are well developed by at least 31 weeks' postmenstrual age.

Somatic hypermutation of immunoglobulin genes in human neonates.

The antibody response in the young infant is limited in several ways; in particular, responses generally are of low affinity and restricted to IgM. This raises the question whether the affinity maturation process, consisting of somatic mutation of immunoglobulin genes coupled with selection of high-affinity variants, is operative in the neonate. Re-arranged V(H)6 genes were amplified by polymerase chain reaction (PCR) from cord blood and from peripheral blood of infants. Heteroduplex analysis detected mutation in only 2/18 cord blood samples, while mutations were seen from about 10 days of age onwards. Cloning and sequencing of mutated neonatal V(H)6 genes showed that mutated sequences contained relatively few mutations (one to three mutations per sequence) compared with published values of about 10 in adult IgM sequences. Selection was not evident in the majority of neonatal samples. Thus mutation can occur in the human neonate, but is minimal and generally not accompanied by selection. The age at which affinity maturation develops effectively is yet to be defined.

Characterisation of relaxation of the lower oesophageal sphincter in healthy premature infants.

BACKGROUND: Gastro-oesophageal reflux disease causes significant morbidity in premature infants, but the role of dysfunction of the lower oesophageal sphincter (LOS) in this condition is unclear. METHODS: Oesophageal manometry was performed after gavage feeding in 13 healthy preterm neonates (postmenstrual age > or = 33 weeks) with a perfused sleeve with side hole assembly. Swallow related (both single and multiple) and transient LOS relaxations (TLOSRs) were identified and the characteristics of these events defined. Reflux was identified with manometric criteria (common cavity episodes). RESULTS: Five hundred and eleven relaxation of the LOS were observed, 55% related to single swallows, 23% related to multiple swallows, and 22% TLOSRs. The time to maximal LOS relaxation was longer for TLOSRs than for single or multiple swallows (mean (SEM) 5.0 (0.3) s v 3.0 (0.1) s and 3.3 (0.1) s, p < 0.0001 and p < 0.005). The durations of multiple swallows and TLOSRs were longer than single swallows (12.2 (0.5) s and 11.2 (0.4) s v 5.3 (0.2) s, p < 0.0001). Most of the oesophageal body common cavity episodes (94%) occurred during TLOSRs. CONCLUSIONS: In healthy preterm infants (postmenstrual age > or = 33 weeks) the motor events associated with LOS relaxation were similar to those seen in healthy adults. TLOSRs may be an important mechanism of reflux in premature infants.

Relationship of hepatocyte growth factor in human umbilical vein serum to gestational age in normal pregnancies.

Hepatocyte growth factor (HGF) is expressed in placental syncitium and fetal organs and acts as a mitogen, motogen, and morphogen in vitro, suggesting a role in fetal growth and development. We aimed to examine the correlates of serum HGF in human cord blood. HGF was measured by ELISA using recombinant human HGF and mouse MAb to recombinant human HGF (Immunology Institute, Tokyo). Umbilical vein blood was collected prospectively at 148 deliveries including 94 normal pregnancies and 54 pregnancies complicated by medical conditions, primarily diabetes mellitus and pregnancy-induced hypertension. Growth parameters, gestation, pregnancy history, and perinatal events were recorded. Sera from 54 adolescents and 32 adult controls were also analyzed. Cord HGF [0.97 (0.66-1.33) ng/mL] [median (25-75 percentile)] was higher than HGF levels in adolescent sera [0.28 (0.21-0.35) ng/mL, p < 0.0001] and adult control sera [0.23 (0.14-0.31) ng/mL, p < 0.0001]. Cord HGF correlated with gestational age (r = 0.42, p = 0.0001) in normal pregnancies, with term babies (n = 69) having higher cord HGF than babies less than 37 wk of gestation (n = 25) [1.11 (0.78-1.45), 0.78 (0.46-1.03) ng/mL, p = 0.0007]. However, there was no relationship between gestation and cord HGF in complicated pregnancies. Cord HGF did not differ at term between appropriate for gestational age babies and small for gestational age babies. There were no independent correlations between cord HGF and birth weight, birth length and placental weight. We provide evidence for the first time that cord HGF levels are high and relate to gestation in normal pregnancies. HGF may have a significant role in fetal development during pregnancy.

Esophageal body and lower esophageal sphincter function in healthy premature infants.

BACKGROUND & AIMS: Gastroesophageal reflux is a common problem in premature infants. The aim of this study was to use a novel manometric technique to measure esophageal body and lower esophageal sphincter pressures in premature infants. METHODS: Micromanometric feeding assemblies (OD, < or = 2 mm) incorporating 4-9 manometric channels were used in 49 studies of 27 premature neonates. Esophageal body motility was recorded at three sites for 20 minutes after feeding. Twenty attempts (one per minute) were made to stimulate swallowing via facial stimulation (Santmyer reflex). In 32 studies lower esophageal sphincter pressures were recorded (sleeve) for 15 minutes before and after feeding. RESULTS: Peristaltic motor patterns were less common than non-peristaltic motor patterns (26.6% vs. 73.4%; P < 0.0001) that comprised 31.1% synchronous, 34.6% incomplete, and 6.3% retrograde pressure waves. Reflex swallowing was elicited more frequently in neonates older than 34 weeks postconceptional age than in younger infants (33.4% vs. 20.4%; P < 0.05). Mean lower esophageal sphincter pressure was 20.5 +/- 1.7 mm Hg before and 13.7 +/- 1.3 mm Hg after feeding (P < 0.0005). CONCLUSIONS: Premature infants show nonperistaltic esophageal motility that may contribute to poor clearance of refluxed material. In contrast, the lower esophageal sphincter mechanisms seem well developed.

Interference from digoxin-like immunoreactive substance(s) in commercial digoxin kit assay methods.

We have examined the current state of interference by digoxin-like immunoreactive substance(s) (DLIS) in 10 commercially available digoxin assay methods, ie 5 radioimmunoassays (RIA) and 5 non-radioactive immunoassays. Fifty-five specimens of maternal venous blood (30 from third trimester pregnancy and 25 at delivery) and 32 cord samples from their offspring were tested (none of the subjects being medicated with digoxin). The results demonstrated a wide range of DLIS interference with values up to 1.1 micrograms.l-1 being obtained in the cord blood specimens. Of the methods tested the "Coat-a Count" RIA (Diagnostic Products Corporation) and the EMIT column method (Syva) run on the Cobas MIRA (Roche) consistently showed the least interference with respect to all 3 sources of specimens. The Delfia Method (LKB/Wallac) consistently showed the greatest crossreactivity with DLIS. The present study thus demonstrates that DLIS interference persists in several commercial digoxin methods and suggests that the use of data obtained from such methods may compromise patient management.