Tool-making and tool-using in the northern blue jay.

Laboratory-raised Northeirn blue jays (Cyanocitta cristata) have been observed tearing pieces from pages of newspaper and utilizing them as tools to rake in food pellets which were otherwise out of reach. The frequency of this behavior was dependenit upon the motivational state of the jay and the presence of food pellets.

Dielectric siphons.

The normally weak polarization force density, exerted on insulating dielectric liquids by a nonuniform electric field, is enhanced if high pressures are used. The result is a new class of orientation and guiding structures for liquids: electric "walls" contain the liquid. The dielectric siphon is an example of such a system. A simple laminar flow model for the device successfully describes the operation of the siphon.

Higher-order dielectrophoretic effects: levitation at a field null.

Experiments with certain new micro-electrode structures used to achieve passive dielectrophoretic levitation of small particles and biological cells reveal a pronounced size-dependent effect not anticipated by the conventional dipole-based model. The conventional theory fails to predict this size effect because it neglects higher-order moments such as the quadrupole, hexapole, and octupole. These higher-order moments are in fact responsible for the levitation force achieved by azimuthally periodic electrode structures because, in such geometries, the electric field is zero along the axis so that the induced dipole moment must be zero. For example, the planar quadrupole levitates particles passively along the central axis through the interaction of its field with the induced quadrupolar moment of the particle. The size effect reported with this structure is readily explained in terms of this quadrupolar component of the ponderomotive force exerted on the particle.

Inflammatory-mediated injury and repair in the traumatically injured spinal cord.

Spinal cord trauma activates the immune system and elicits leukocyte recruitment to the site of injury. This increase in immunological activity contributes to acute lesion expansion over a period of days to weeks following the initial trauma. At the same time, inflammatory cells and mediators facilitate endogenous repair processes such as axonal sprouting and remyelination. Thus, to be effective, therapies that target the immune system must limit the destructive effects of neutrophil, macrophage and lymphocyte activation, while simultaneously preserving their reparative functions.

Determination of left-ventricular volume from first-pass kinetics of labeled red cells.

A mathematical model is presented for the dynamics of a bolus of technetium-99m-labeled red blood cells through the left ventricle. It is used to correct for attenuation the count rate observed over the left ventricle during a conventional gated blood-pool study. The left-ventricular volumes are calculated from the corrected count rates and expressed as a percentage of total blood volume, or in absolute terms if a blood sample is obtained. The procedure is applied to a number of patients with nonvalvular cardiac disease. Cardiac volumes determined by the method are found to correlate well (r = 0.98) with those determined by contrast left ventriculography. The method is simple, requires no special equipment, and can be applied with existing computer software.

Genetic analysis reveals ongoing HIV type 1 evolution in infected human placental trophoblast.

To provide a better understanding of the role of placenta in vertical human immunodeficiency virus (HIV) transmission, we have studied the infection of placental trophoblast in a group of 15 mother-neonate pairs. By nested PCR amplification of the C2V3 env gene region, HIV-1 has been found to infect the placenta in five cases (33%). Phylogenetic analysis of the cloned sequences showed that all recovered maternal variants were of the B subtype. Further investigation into the ancestral relationships at the nucleotide level revealed that the trophoblast sequences evolved into a quasispecies population clearly distant from that observed in the mother. As expected, the populations transmitted to the trophoblast were also found to be more homogeneous than those in the mothers when characterized on the basis of pairwise nucleotide sequence distances. With regard to the predicted biological properties, the primary amino acid structure of the V3 loop domain was consistent, with a macrophage-tropic, non-syncytium-inducing phenotype in all patients. We also attempted to determine if any of a number of selected maternal or viral factors was associated with trophoblast infection. However, none of the followed parameters, including maternal age, disease stage, antiretroviral therapy, CCR5delta32 deletion status of the infant, and viral genotype, could be associated with viral transmission. Moreover, in one pair with proven trophoblast infection, HIV was also detected in the cord blood. Taken together, our data suggest that the productive trophoblast infection by HIV-1 in vivo is a relatively frequent event that may bear direct implications for a further transplacental propagation of the virus.

Volumetric determination of placental and uterine growth relationships from B-mode ultrasound by serial area-volume determinations.

Serial area-volume determinations may be made from B-mode ultrasonography. Multiple sonographic sections are taken through a structure of interest. The area of the structure of interest is determined on each sonographic section by a form of planimetry and multiplied by the step-interval to obtain the volume of the structure of interest between sonographic sections. The total volume of the structure of interest is the sum of the individual volumes. The volume is computed from both transverse and longitudinal images and an average obtained for improved accuracy. Total intrauterine volume and placental volume were determined by the serial area-volume method in 63 normal patients and the results were analyzed. Placental and total intrauterine volumes were also determined for five cases of intrauterine growth retardation. Although there is some error in the serial area-volume method, the initial evaluation of five cases with intrauterine growth retardation suggests a greater precision and accuracy than volume estimates based on prolate ellipsoid geometry. Placental volume may provide an acceptable parameter to screen for intrauterine growth retardation.

FL/AC ratio: poor predictor of intrauterine growth retardation.

Early antenatal detection of intrauterine growth retardation (IUGR) may decrease the associated perinatal morbidity and mortality. A parameter based on sonographically measured femur length (FL) and abdominal circumference (AC), expressed as FL/AC X 100 and termed the FL/AC ratio, has recently been proposed by Hadlock et al as an age-independent predictor of IUGR. We studied 285 normal and 37 IUGR fetuses to verify that the FL/AC ratio is independent of gestational age (GA) and to assess its value as a predictor of IUGR. Our results confirm that the FL/AC ratio is age-independent above 20 weeks and that its mean value differs in normal (22.4 +/- 1.7) and IUGR (23.7 +/- 1.4) fetuses (P less than .01, t-test). Because of considerable overlap between these two groups, however, there is no cutoff value for the FL/AC ratio that yields both a high sensitivity and a high specificity, or that leads to a high positive predictive value. With a cutoff of 23.5, for example, the sensitivity is 56% and the specificity 74%, and, even assuming an IUGR prevalence rate of 10%, the likelihood of IUGR in a fetus with an FL/AC ratio above the cutoff is only 19%. We conclude that the FL/AC ratio, though an age-independent measure whose mean value differs in normal and IUGR fetuses, is not clinically useful as a predictor of IUGR.

A thrombogenic uterine pack for postpartum hemorrhage.

BACKGROUND: A low-lying placenta or placenta previa is frequently associated with postpartum hemorrhage from a low implantation site. We describe the successful use of a thrombin-soaked uterine pack for this condition. CASE: A 30-year-old woman, gravida 3, para 0-0-2-0, had placenta previa diagnosed by ultrasound at 26 weeks' gestation. A repeat examination at 35 weeks demonstrated a low-lying placenta. The patient had an uncomplicated intrapartum course and was delivered by vacuum extraction, but excessive vaginal bleeding was noted 3 hours after spontaneous delivery of the placenta. Oxytocin, prostaglandin, and uterine curettage failed to control the hemorrhage. In an attempt to avoid laparotomy, we placed a thrombin-soaked uterine pack over the bleeding site. There was minimal vaginal bleeding during the following 8 hours, so the pack was removed. The patient had no further complications and was released 3 days after delivery. CONCLUSION: A thrombin-soaked uterine pack may successfully control lower uterine segment bleeding following delivery of a patient with a low-lying placenta. This technique offers the obstetrician another treatment option in selected cases of postpartum hemorrhage.

Modulation of NK cell cytolytic activity by macrophages in chronically exercise-stressed mice.

This study was designed to investigate the effects of moderate-intensity endurance training on basal natural killer (NK) cell cytolytic activity in murine splenocytes that were enriched for 1) NK1.1+ cells or 2) macrophages and NK1.1+ cells. Mice were assigned to sedentary (Sed), treadmill control (TM), or treadmill-trained (Trn) groups. Splenocyte number, the percentages of NK1.1+, large granular lymphocytes (NK1.1+, LGL-1+), and other subpopulations did not change in Trn mice. Approximately 70% of cells enriched for NK1.1+ expressed this surface antigen. Lytic units (LU) expressed per LGL-1+ cell were significantly lower in Trn [83.9 +/- 3.2 (SE)] compared with Sed (109.5 +/- 7.5) and TM (101.3 +/- 6.4) groups. When macrophages remained in the in vitro assay, LU per LGL-1(+) cell did not differ across groups. The results indicate that highly enriched NK1.1+ cells from Trn mice had lower NK cell activity compared with Sed mice. No differences in NK cell activity were observed when cells were enriched for NK1.1+ cells and macrophages. These findings support the hypothesis that macrophage modulation of NK cells may be one mechanism contributing to augmented basal NK cell activity in endurance-trained individuals.

Fetal hemoglobin quantitations using the Hemocue system are rapid and accurate.

OBJECTIVES: To determine whether hemoglobin quantitations using the Hemocue system, a rapid and portable hemoglobin photometer, on fetal blood obtained via funipuncture were accurate compared to the Coulter S-Plus IV. We also examined whether gestational age or extremes in hemoglobin levels significantly affected the accuracy of the Hemocue system. METHODS: We performed fetal hemoglobin quantitations using both systems on 58 specimens obtained between 18-38 weeks' gestation. Correlation between values by both systems was determined by linear regression analysis. The effects of gestational age and hemoglobin extremes on the accuracy of the Hemocue system were evaluated by stepwise regression. RESULTS: The mean Hemocue value was 12.0 +/- 2.4 g/dL (range 3.3-16.4); the mean Coulter value was 11.7 +/- 2.3 g/dL (range 3.6-16.2). The regression equation for Hemocue (y) versus Coulter (x) values was y = 0.72 + 0.97x; r = 0.94 (P < .0001). Neither gestational age nor hemoglobin extremes significantly affected the accuracy of the Hemocue system. CONCLUSION: The Hemocue system is rapid and accurate for fetal hemoglobin quantitation between 18-38 weeks' gestation regardless of extremes in gestational age or hemoglobin levels.

Preconceptional planning.

Preconceptional counseling has become an important part of obstetrical care. The concept of preconceptional planning is discussed in detail, with an emphasis on particular high-risk groups. The role of genetics and fetal diagnosis is also examined.

Ultrasound guidance for selected dilatation and evacuation procedures.

Intraoperative ultrasound was used as an adjunct in difficult dilatation and evacuation (D&E) procedures for first-trimester abortions. This technique was useful in eight technically difficult D&Es in the presence of acute retroflexion, acute anteflexion, cervical stenosis and lower uterine segment fibroids.

Electrowetting dynamics of microfluidic actuation.

When voltage is suddenly applied to vertical, parallel dielectric-coated electrodes dipped into a liquid with finite conductivity, the liquid responds by rising up to reach a new hydrostatic equilibrium height. On the microfluidic scale, the dominating mechanism impeding this electromechanically induced actuation appears to be a dynamic friction force that is directly proportional to the velocity of the contact line moving along the solid surface. This mechanism has its origin in the molecular dynamics of the liquid coming into contact with the solid surface. A simple reduced-order model for the rising column of liquid is used to quantify the magnitude of this frictional effect by providing estimates for the contact line friction coefficient. Above some critical threshold of voltage, the electromechanical force is clamped, presumably by the same mechanism responsible for contact angle saturation and previously reported static height-of-rise limits. The important distinction for the dynamic case is that the onset of the saturation effect is delayed in time until the column has risen more than about halfway to its static equilibrium height.

Influence of scale on electrostatic forces and torques in AC particulate electrokinetics.

Dielectrophoretic forces and torques move and manipulate biological cells, typically of the order of 10 mum ( approximately 10(-5) m) in diameter and ordinarily suspended in aqueous liquids, using electrodes with dimensions around 100 mum ( approximately 10(-4) m). The ability to exploit these same electromechanical effects for particles below 1 mum, that is, <10(-6) m, creates opportunities for remote manipulation and handling of subcellular components, biological macromolecules, and DNA. In this paper, Trimmer's bracket notation is adapted for systematic examination of the scaling laws governing electrokinetic behaviour. The purpose is to shed light on how critical performance measures relevant to the laboratory on a chip are affected by reducing particle sizes and electrode dimensions into the nanometre range. The scaling methodology facilitates consideration of the effect of electrode structure and particle size reduction on voltage, electric field, heating, and response time. Particles with induced moments, dipolar and quadrupolar, as well as permanent dipoles are examined. Separate consideration is given to electrical torque and its application in electrorotation and particle alignment. An eventual goal of these scaling studies is to identify the lower limit on the size of particles that can be manipulated effectively using electrokinetic phenomena.

Dielectrophoretic spectra of single cells determined by feedback-controlled levitation.

In this paper we have utilized the principle of dielectrophoresis (DEP) to develop an apparatus to stably levitate single biological cells using a digital feedback control scheme. Using this apparatus, the positive DEP spectra of both Canola plant protoplast and ligament fibroblast cells have been measured over a wide range of frequencies (1 kHz to 50 MHz) and suspending medium conductivities (11-800 muS/cm). The experimental data thus obtained have been interpreted in terms of a simple spherical cell model. Furthermore, utilizing such a model, we have shown that various cellular parameters of interest can be readily obtained from the measured DEP levitation spectrum. Specifically, the effective membrane capacitance of single cells has been determined. Values of 0.47 +/- 0.03 muF/cm2 for Canola protoplasts and 1.52 +/- 0.26 muF/cm2 for ligament fibroblasts thus obtained are consistent with those determined by other existing electrical methods.

Electro-orientation of ellipsoidal erythrocytes. Theory and experiment.

The frequency-dependent orientation of human and llama erythrocytes suspended in isotonic solutions and subjected to linearly polarized electric fields is examined. Human erythrocytes may be represented as oblate spheroids (3.9:3.9:1.1 microns) with two distinguishable orientations, while the llama cells are approximated as ellipsoids with three distinct axes (4.0:2.0:1.1 microns). Under appropriate experimental conditions, both orientations of the human cells and all three orientations of the llama cells are observed. A theoretical cell model which accounts for the membrane as a thin confocal layer of ideal capacitance is used to predict the orientational spectra. The predicted spectra compare favorably in frequency range and orientational sequence with experimental data. Estimates for cell internal conductivity and permittivity are obtained by adjusting the values of these important parameters to achieve the closet fit of the theoretical curves to the data. By the use of this method, the internal conductivity of llama erythrocytes is estimated to be 0.26 S/m (+/- 20%), while the effective internal dielectric constant and conductivity of Euglena gracilis are estimated to be 120 (+/- 10%) and 0.43 S/m (+/- 20%), respectively.

Immunologic tolerance to HGG in mice. I. Suppression of the HGG response in normal mice with spleen cells or a spleen cell lysate from tolerant mice.

Adoptive transfer of spleen cells or spleen cell lysates from mice tolerant to human-gamma-globulin (HGG) specifically suppressed the response of normal syngeneic recipients to HGG. The suppressive activity could be transferred for over 100 days after tolerance induction. The suppression induced by both spleen cells and spleen cell lysate was found to be specific as evidenced by a normal response to a challenge with turkey-gamma-globulin or goat erythrocytes. The activity of the suppressive lysate could be removed by passing the material through an HGG immunoadsorbent column but not by passing it through an anti-HGG column or a BSA column. These results indicated that the factor had antigen specificity and was probably not antigen-antibody complexes. That this suppression was not due to a shifting of the kinetics of the antibody response has also been demonstrated. The antigen-specific suppressor factor in the tolerant spleen cell lysates was a protein with a m.w. of approximately 45,000 daltons. The kinetics of the appearance of both suppressor cells and suppressor factor were consistent with a mechanism of active suppression functioning in the maintenance of tolerance to HGG.