Light scattering from water droplets in the geometrical optics approximation

The geometrical optics approach is used to derive i(1)(theta) = |S(1)(theta)|(2) and i(2)(theta) = |S(2)(theta)|(2), the angular intensity functions for light scattered by a spherical water droplet of a radius comparable with or larger than the wavelength of light. In contrast to previously published results, these functions are obtained in closed form and as functions of the scattering angle theta, which greatly enhance their usefulness in numerical work and in the reduction of large sphere scattering data. The range of validity of these expressions is investigated by graphical comparison of calculated angular intensity patterns with those obtained from rigorous Mie theory. Our main objective is to study the feasibility of using the geometrical optics expressions as a basis for practical laser water droplet sizing work. A criterion is established for the range of applicability of the relationship I(theta,R) = K(theta)R(2), which relates the scattering intensity at a particular angle theta to the radius R of the droplet. Accuracy of the laser water droplet sizing technique is thus quantitatively established.

Use of genetic markers to certify fetal origin of cultured amniotic fluid cells

Phenotypes of five polymorphic enzymes: red cell acid phosphatase, phosphoglucomutase, esterase D, adenosine deaminase, and 6-phosphogluconate dehydrogenase were determined in extracts of 24 amniotic fluid cell cultures and in the corresponding maternal red cells. Twenty-one of the 24 fetus/mother pairs can be distinguished by at least one of the markers. Thus, polymorphic enzyme markers may be useful in affirmation of fetal origin of cultured cells and to avoid possible diagnostic errors.

Use of cultured lymphoblastoid cells for the study of abnormal enzymes: molecular abnormality of a phosphoglycerate kinase variant associated with hemolytic anemia

A phosphoglycerate kinase (PGKase: ATP:3-phosphoglycerate 1-phosphotransferase, EC 2.7.2.3; X chromosome-linked) variant, PGKase-Tokyo, is associated with enzyme deficiency, nonspherocytic hemolytic anemia, and neurological disturbances. Because a sufficient amount of the patient's erythrocytes was not available, the variant enzyme was purified to homogeneity from the cultured lymphoblastoid cells of the patient. The enzyme activity of the variant lymphoblastoid cells was about 16% of that of the normal lymphoblastoid cells. PGKase-Tokyo, compared to the normal enzyme, had a lower specific activity (31% of normal in the backward reaction and 15% of normal in the forward reaction), higher than normal Michaelis constants for ATP and 3-phosphoglycerate, a more acidic pH optimum, and increased thermal instability. Microscale peptide mapping analysis revealed that the structural abnormality of PGKase-Tokyo is a single amino acid substitution from valine to methionine at position 266. Thus, the use of the cultured lymphoblastoid cells is proven to be useful for the study of structural and functional abnormalities of mutant enzymes.

Simple low-cost digital events analyzer

We present the design and applications of a simple and very low-cost digital events analyzer, suitable for use in a student laboratory as well as in research applications. The pulse analyzer can perform five functions: sampling measurement; pulse interval distribution measurement; simple triggered multichannel scaling; scaled triggered multichannel scaling; and auto- and cross-correlation function measurement. The memory capacity is limited to 100 channels with 11 bits or more word length. The basic cycle time of the analyzer is 500 ns as limited by the speed of MOS circuit used. We demonstrate the utility of it with counting statistics experiments of radiations from radioactive decay, neutron time of flight analysis, and also the photon correlations measurements of light scattered from particles in fluids.

Evidences suggestive of no intestinal nitrogen fixation for improving protein nutrition status in sweet potato eaters

Total of seven teenagers and two adults were given sweet potato diets that supplied slightly below requirement levels of protein for 32 (experiment 1) or 53 days (experiment 2) in two separate experiments. In experiment 1 and during the first 36 days of experiment 2, nitrogen (N) balance studies with the teenagers were conducted with 0.67 and 0.71 g of protein per kilogram of body weight, respectively. Results of the N balances including skin N loss were -0.5 mg N/kg per day in experiment 1 and -3.2 mg N/kg per day in experiment 2. Two adults were given 0.63 g/kg of protein and gave average N balance of +6.0 mg N/kg per day (experiment 2), however, one of them had a slightly negative cumulative N balance if miscellaneous N losses were included in calculation. Plasma urea N of both teenagers and adults decreased significantly from 8 to 11 to 2 to 3 mg/100 ml in experiment 2. After 32 or 53 days on the sweet potato diets, the plasma free amino acid pattern of the teenager subjects showed abnormality. Furthermore, the subjects were easier to get fatigue by physical exercise, and took longer nap due to sleepiness during the latter days of the experiments. Thus, although the mean hemoglobin, hematocrit, plasma total protein, and plasma albumin levels were within the normal ranges, the protein nutrition status of the teenagers and one of the two adults was considered to be not normal. The results suggested that intestinal N-fixation that was proposed by several investigators to occur in sweet potato eaters probably did not occur. The subjects' feces were examined in vitro for the ability of N-fixation with negative results. During the last 17 days of experiment 2 the effect of excess calorie on N balance was examined.

Accuracy of RGD approximation for computing light scattering properties of diffusing and motile bacteria

The quasi-elastic light scattering has become an established technique for a rapid and quantitative characterization of an average motility pattern of motile bacteria in suspensions. Essentially all interpretations of the measured light scattering intensities and spectra so far are based on the Rayleigh-Gans-Debye (RGD) approximation. Since the range of sizes of bacteria of interest is generally larger than the wavelength of light used in the measurement, one is not certain of the justification for the use of the RGD approximation. In this paper we formulate a method by which both the scattering intensity and the quasi-elastic light scattering spectra can be calculated from a rigorous scattering theory. For a specific application we study the case of bacteria Escherichia coli (about 1 microm in size) by using numerical solutions of the scattering field amplitudes from a prolate spheroid, which is known to simulate optical properties of the bacteria well. We have computed (1) polarized scattered light intensity vs scattering angle for a randomly oriented bacteria population; (2) polarized scattered field correlation functions for both a freely diffusing bacterium and for a bacterium undergoing a straight line motion in random directions and with a Maxwellian speed distribution; and (3) the corresponding depolarized scattered intensity and field correlation functions. In each case sensitivity of the result to variations of the index of refraction and size of the bacterium is investigated. The conclusion is that within a reasonable range of parameters applicable to E. coli, the accuracy of the RGD is good to within 10% at all angles for the properties (1) and (2), and the depolarized contributions in (3) are generally very small.

Spatio-temporal structure of migrating chemotactic band of Escherichia coli. I. Traveling band profile

We developed a rapid-scanning, light-scattering densitometer by which extensive measurements of band migration speeds and band profiles of chemotactic bands of Escherichia coli in motility buffer both with and without serine have been made. The purpose is to test the applicability of the phenomenological model proposed by Keller and Segel (J. Theor. Biol. 1971. 30:235) and to determine the motility (mu) and chemotactic (delta) coefficients of the bacteria. We extend the previous analytical solution of the simplified Keller-Segel model by taking into account the substrate diffusion which turns out to be significant in the case of oxygen. We demonstrate that unique sets of values of mu and delta can be obtained for various samples at different stages of migration by comparing the numerical solution of the model equation and the experimental data. The rapid-scanning technique also reveals a hitherto unobserved time-dependent fine structure in the bacterial band. We give a qualitative argument to show that the fine structure is an example of the dissipative structure that arises from a nonlinear coupling between the bacterial density and the oxygen concentration gradient. Implications for a further study of the dissipative structure in testing the Keller-Segel model of chemotaxis are briefly discussed.

Partial trisomy 20 confirmed by gene dosage studies

We describe a female infant with multiple congenital anomalies and mental retardation, pre- and postnatal growth failure, microcephaly, unusual facial appearance, and minor skeletal anomalies, all very suggestive of the partial trisomy 20(p) syndrome. Although she was born to karyotypically normal parents, she had an extra small metacentric chromosome. Analysis of metaphase and prometaphase chromosomes by GTG banding and Giemsa 11 staining showed that the extra chromosome was a number 20 with a deletion of the distal end of the long arm. Gene dose studies of adenosine deaminase (ADA) and inosine triphosphatase (ITP) supported the cytogenetic interpretation.

Adenosine deaminase deficiency: disappearance of adenine deoxynucleotides from a patient's erythrocytes after successful marrow transplantation

Accumulation of adenine deoxynucleotides (dATP and dADP) in the erythrocytes of a patient with adenosine deaminase (ADA) deficiency was confirmed. The patient, now 18 mo old, was treated with a bone marrow transplantation from his HLA identical sister at 7 mo of age. Before and after the transplant, his erythrocyte and lymphocyte ADA activities, as well as his erythrocyte nucleotide profiles, were measured. 10 wk after the marrow transplant, no ADA activity could be detected in his erythrocytes, whereas there was a mixture of donor and patient lymphocytes as measured by ADA assays and karyotyping. At the same time, both dATP and dADP had disappeared from his erythrocytes, which were entirely of patient origin. These findings indicate that partial engraftment of donor lymphocytes into an ADA-deficient patient is capable of "correcting" alterations of deoxynucleotide concentrations in the patient's ADA-deficient erythrocytes.

Rotational-translational models for interpretation of quasi-elastic light scattering spectra of motile bacteria

Quasi-elastic light scattering is a powerful tool for studying dynamic behavior of motile bacteria in liquid suspension. Previously we proposed an ellipsoidal structural model to account for the straight line motion of E. coli bacteria. We have in this article extended our structural model to include rotational motions superimposed on the translational motion of the center of mass. A general formulation is given by which the light scattering spectrum of any rotational-translational motion of a structured particle can be calculated. Specific calculations are carried out for three types of rotational motions, namely, planar wiggling motion, pure rotation, and helical rotation, around the average direction of motion. Further narrowing of the scattered field correlation function as compared with that of the straight line motion is observed in all three cases. We finally compare the helical rotation model with our previous experimental results for E. coli and find a substantial improvement over that of the straight line motion model.

Quasi-elastic light scattering from migrating chemotactic bands of Escherichia coli

We report the observation of migrating chemotactic bands of Escherichia coli in a buffer solution. The temporal development of the bacterial density profile is observed by the scattered light intensity as the band migrates through a stationary laser beam. We have made a preliminary analysis of the observed band profile with help of the Keller-Segel theory. The model accounts for only some aspects of the observed time evolution of the density profile. The microscopic motility characteristics of the E. coli in the band are simultaneously studied by photon correlation. The measured correlation functions are analyzed to obtain the spatial dependence of the half-width within the band. A simple analytical model is proposed to account for the contribution of the twiddle motion to the correlation function. By analyzing the correlation function as a superposition of straight-line and twiddle motions, we obtain a satisfactory agreement between the theory and the measured angular dependence of the line shape. As a consequence we are able to extract a parameter beta, which measures the average fraction of twiddling bacteria in the center of the band at a given time.

Structural effects in quasi-elastic light scattering from motile bacteria of E. coli

An extensive study has been made of the angular dependence of the intensity as well as the quasi-elastic intensity correlation function of light scattered from a dilute suspension of E. Coli K(12) bacteria in solution using the photon correlation technique. We have demonstrated that it is essential to consider the shape as well as the internal structure of bacteria in order to account fully for both the scattered intensity and the field self-correlation function as reduced from the intensity correlation function. The simple structure model previously proposed accounts well for both the intensity and diffusion data with a reasonable set of parameters. For the case of motile bacteria the observed field correlation function at small scattering angles is well represented by assuming a mixture of diffusive and straight line swimming motions of the bacteria. At larger scattering angles contributions of rotational motions become significant.

Tracking bacterial movements using a one-dimensional fringe system

Movements of individual E. coli bacteria in solution are detected by a one-dimensional fringe system formed in the focal region of two crossed laser beams. The time modulation of the scattered light intensity is used to deduce the instantaneous speed of the bacterial motion as it enters into the focal region. A method is described as being capable of testing the isotropic speed distribution function without the complications associated with the finite size and structural effects that influence the interpretation of the conventional light-scattering spectra.

Use of the integrated steady state rate equation to investigate product inhibition of human red cell adenosine deaminase and its relevance to immune dysfunction

The analysis of progress curves using the integrated rate equation was applied to the adenosine deaminase-catalyzed conversion of adenosine to inosine. Adenosine deaminase was purified from human red blood cells of phenotypes ADA 1, ADA 2, and ADA 2-1. For all three types, no measurable product inhibition by inosine was observed. These results do not confirm the hypothesis that inosine accumulation in purine nucleoside phosphorylase deficiency causes adenosine deaminase inhibition, resulting in a common mechanism for the immune defects related to these two enzyme deficiencies.