Biomedical subjects
Publications and source records attributed to L C Allen.
The ultrasonic appearance of the normal and abnormal fetal spine before 20 weeks' gestation was reviewed in 121 pregnances. A model was constructed to establish the mechanism of production in the various configurations seen. The relative roles of ultrasonography, alpha fetoprotein assay, and fetoscopy in the diagnosis of spina bifida are discussed.
The finding of an elevated level of alpha fetoprotein (AFP) in amniotic fluid is of value in the prenatal diagnosis of open neural tube defects. The present study was done to determine the amount of fetal blood required in amniotic fluid to produce a significant and misleading increase in AFP. Fetal blood was obtained at hysterotomy, and measured volumes were added to amniotic fluid samples. Bethe-Kleihauer tests, red cell counts, and AFP determinations were done. On the average, at 16 weeks' gestation, contamination of 5 ml. of amniotic fluid with 22 mul of fetal blood will results in an increase in AFP of 1.6 mg. per deciliter. Fetal cells in a much lower concentration can readily be detected by the Bethe-Kleihauer technique. A Bethe-Kleihauer test and red cell count should be done on all blood-stained amniotic fluid samples to determine the amount of fetal blood present. The contribution of the fetal blood AFP can then be estimated and must be considered in the interpretation of the total amniotic fluid AFP result.
The effects were studied of 10 days' exposure to daily repetitive, specific vestibular stimulation on motor performance of children with Down's syndrome and normal children. A quantitative assessment of vestibular function was made in these children including the habituation response of postrotatory nystagmus. Control groups were included. Both the children with Down's syndrome and the normal children who received vestibular therapy demonstrated positive effects when evaluated using a quantitative motor skills assessment test. Control and treatment children showed vestibular habituation, with treatment children evidencing the greater change. This change may reflect the acquisition of an increased level of central nervous system inhibitory control.
A MODEL OF THE LINEAR HYDROGEN BOND HAS BEEN DEVISED WHICH IS CHARACTERIZED BY THREE PHYSICAL PARAMETERS OF THE ISOLATED ELECTRON DONOR AND PROTON DONOR MOLECULES: mu(A-H), the bond dipole moment; DeltaI, the difference in ionization potential between that of the electron donor and the corresponding noble gas atom; and l, the length of the electron donor lone-pair of electrons. The model is able to explain dimerization energy, charge transfer, internuclear separation, directionality, stretching force constants, dimer dipole moment, and infrared intensity enhancement.
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