Abstract: Ligand-aminodextran-(phycobiliprotein or tandem dye) conjugates useful for detection of a desired target biological material by providing an enhanced fluorescent signal are described. Also described is a method for a single-measurement quantification of multiple populations of cells based upon the labeling of different pairs of cell populations, each pair containing mutually exclusive cell receptors which are expressed at substantially similar receptor densities with labeled ligands for each receptor. One cell population is labeled with a ligand capable of binding to a first cell surface receptor which ligand is directly conjugated to a fluorescent phycobiliprotein or tandem dye; and a second cell population is labeled with a ligand capable of binding to a second cell surface receptor, which ligand is cross-linked to an aminodextran to a fluorescent phycobiliprotein or tandem dye.

Abstract: A dye compound having the formula I: wherein, n is 0, 1, 2, or 3; R1 is H, alkyl, or an alkoxy group; R2 is CH2(CH2)mOH, wherein m is 0, 1, 2, or 3; X is O, S, or C(CH3)2; R is CH3, CH(CH3)2, CH2CH2OH, alkyl, alkylsulfonate, or hydroxyalkyl and B− is a counteranion. Red- and blue-excitable dyes based on the above chemical structure are described, and reagents containing them are described for use in staining nucleic acid, more particularly for staining reticulocytes. Also described are methods for detecting reticulocytes using such compositions.

Abstract: Apparatus for precisely aspirating small volumes of liquid, e.g., a blood sample, contained in a vessel, e.g., a test tube or vial, includes a mechanism for sensing that the tip of an aspirating probe is contacting the bottom of the vessel during the aspiration process. Such a bottom-sensing mechanism is adapted to sense a predetermined forcible interaction between the probe tip and the vessel bottom. In a preferred embodiment, such forcible interaction is sensed by detecting movement of a movably mounted platform that supports the vessel during aspiration. In a second embodiment, the forcible interaction is sensed by detecting the back-emf in a motor winding used to advance the aspiration probe.

Abstract: A specimen carrier comprises a unitary structure for receiving and retaining a specimen container in an upright orientation. Such unitary structure is defined by a pedestal having upper and lower platforms connected by a stem. Extending upwardly from the upper platform is a plurality of rigid members which support a plurality of opposing flexible fingers adapted to engage and press upon the side wall of a specimen container received by the carrier. Preferably, the specimen carrier of the invention has a chamber formed therein for housing a pre-programmed, programmable or otherwise radio-frequency (RF) identification tag in the form of an RF transponder. Upon being energized by a suitable RF field provided by an RF reader antenna or sensor positioned adjacent the carrier's intended path of movement, the tag transmits a unique identification code, such code being received by the antenna or sensor and decoded by the reader.

Abstract: A method and apparatus for aspirating and dispensing precise volumes of liquid, e.g. whole blood, comprises an aspiration probe or needle having an internal volume precisely equal to a desired volume to be dispensed, and a computer-controlled shear valve for trapping aspirated liquid inside the probe for subsequent dispensing. A liquid sensor positioned downstream of the shear valve cooperates with a liquid level sensor on the probe tip to assure that the probe lumen is filled with the aspirated liquid.

Abstract: A junction field effect transistor (JFET) RF oscillator-detector circuit generates an RF signal for an apparatus for conducting electrical measurements of particles contained in a carrier fluid passing through an aperture in a cytometer flow cell. The JFET oscillator includes a plurality of parallel-coupled JFETs having respectively different VDS vs. IDS characteristics, that are biased to operate at square law detection regions of their respective VDS vs. IDS characteristics. One JFET operates in Class C mode, while the other operates in Class AB mode. An RF resonant circuit is electrically coupled to the JFETs and to the measurement cell, and is operative to establish the frequency of an RF field applied to the measurement cell. An RF load change detection circuit is coupled to the RF resonator circuit and is operative to detect an RF load change associated with a modification of the RF field as a result of a particle within the measurement cell aperture.

Abstract: A particulate sample mixing and delivery apparatus externally sonically mixes respective samples of particulate stored in storage containers that are sequentially indexed by a carousel prior to being dispensed into an analyzer reservoir. Each container is compliant to acoustic energy emitted by a sonicator unit that is placed against an external surface of a respective container to which preferably a carrier fluid and surfactant are controllably supplied. After sonication, the container is indexed to a sample dispensing location adjacent to the analyzer reservoir. A tiltable cradle then rotates the container to rapidly dispense its mixed contents into the reservoir, and then discards the empty container.

Abstract: The present invention provides an improved a-Si:H photoreceptor comprising a-Si:H photoconductors and conductive substrates, such as metallic members or plastic members provided with a metallic or an ohmic layer, in which degrading effects of the ambient environment on the electrophotographic properties of the a-Si:H photoconductor is minimized. The present invention also provides a cost-effective method of forming the improved a-Si:H photoreceptors. The method comprises stabilizing an a-Si:H photoreceptor member against environmental degradation of its photoconductive properties, by modifying the working surface of the photoconductor through treatment with a silanol solution. The clean annealed photoreceptor is preferably exposed to a freshly prepared aqueous mixture of an organosilane hydrolyzable to yield a silanol solution. The photoreceptor is then rinsed with water to remove vagrant oligomers formed during condensation of the silanol prepolymers but unattached to surface sites on the photoconductor.

Abstract: A flow cytometer sorting mechanism is operative to controllably sort successively generated fluid droplets in accordance with the contents of a plurality of contiguous precursor regions of the carrier fluid which are contained within a target droplet of interest and precursor regions for droplets on either side of the target droplet. This multi-region sorting window scheme is particularly useful in reducing the time required to harvest a highly purified quantity of a particular type of cell, as not only are droplets containing only desired cells sorted to a highly purified collection store, but should an undesired cell be detected within a predefined proximity of a desired cell, rather than being simply aborted, the droplet is sorted into an auxiliary enrichment container, whose contents may then be reclaimed for resorting. Since all droplets are sorted to one of a plurality of droplet reclamation containers, substantially no detected/target cells are lost.

Abstract: A rapid fluorescence staining method for facilitating flow cytometry analysis of reticulocytes is described. The method comprises contacting cells with a cocktail containing a detergent, sphering agent, and a cell impermeable dye, such as TO-PRO-3, for about one minute. Advantageously, the inventors have found that the cocktail permits the dye to penetrate the cell membrane rapidly.

Abstract: Apparatus for sensing and characterizing particles suspended in a liquid medium includes a particle-sensing structure having a continuous wall defining a hydrodynamically smooth conduit through which the liquid suspension of particles is caused to pass simultaneously with an electrical current. Particles passing through the conduit are sensed and characterized by monitoring changes in the electrical current through the conduit. According to the invention, the continuous, conduit-defining wall is made entirely of a material having an electrical resistivity less than or equal to that of the liquid medium. Thus, the apparatus of the invention is similar to the conventional Coulter aperture (conduit) except that the aperture is formed from an electrically conductive material instead of a dielectric material.

Abstract: A semiconductor nanoparticle for use in analysis of biological samples is described. This semiconductor nanoparticle is composed of an aminodextran which is bound to at least one nanoparticle of the formula (X Y)n wherein X is selected from the group comprising Cd2+, Hg2+, and Zn2+ and combinations thereof; and Y is selected from the group comprising S2−, Se2− and Te2− and combinations thereof; and n=approximately 50 to 1000. Also provided are methods of making these semiconductor nanoparticles and methods of making conjugates composed of these semiconductor nanoparticles linked to ligands. Also described are uses for the conjugates in a variety of biological assays.

Abstract: A method and apparatus for differentiating and enumerating the five major sub-populations of leukocytes in a blood sample (i.e., lymphocytes, monocytes, eosinophils, neutrophils and basophils) uses multiangle light scatter and DC (Coulter) volume measurements. Light scattering characteristics of the leukocytes are determined within five different angular ranges, all being lower than 40 degrees. The invention is particularly useful in differentiating and enumerating the basophil sub-population which has heretofore required more complex apparatus and/or chemical processing.

Abstract: A blood analyzing instrument includes a single transducer for simultaneously measuring the DC volume, RF conductivity, light scattering and fluorescence characteristics of blood cells passing through a cell-interrogation zone. Preferably, the transducer includes an electro-optical flow cell which defines a cell-interrogation zone having a square transverse cross-section measuring approximately 50×50 microns, and having a length, measured in the direction of cell flow, of approximately 65 microns.

Abstract: This invention relates to lytic reagents and methods of using the lytic reagents for automatically determining leukocyte subpopulations in blood. More specifically, the new lytic reagents selectively lyse red blood cells and certain leukocyte subpopulations, which enables the differentiation of at least one subpopulation of leukocytes. The lytic reagents contain an ethoxylated long chain amine, a quaternary ammonium salt and an acid. When used in combination with a second lytic reagent system, one is able to obtain at least a five part differential of leukocytes by impedance and light scatter measurements, by impedance and radio frequency measurements, or by radio frequency and light scatter measurements.

Abstract: This invention relates to lytic reagents and methods of using the lytic reagents for automatically determining leukocyte subpopulations in blood. More specifically, the new lytic reagents selectively lyse red blood cells and certain leukocyte subpopulations, which enables the differentiation of at least one subpopulation of leukocytes. The lytic reagents contain a polyoxyethylene based surfactant, a quatemary ammonium salt and an acid. When used in combination with a second lytic reagent system, one is able to obtain at least a five part differential of leukocytes by impedance and light scatter measurements, by impedance and radio frequency measurements, or by radio frequency and light scatter measurements.

Abstract: A differential DC/RF bridge-configured flowcell particle detector includes a flowcell and an adjustable circuit model of the flowcell, which are differentially coupled through output amplifier circuits and galvanically isolated from sources of signal degradation. The output of the difference amplifier is coupled to a DC/RF discriminator and associated downstream processing circuitry. Respective amplitude and phase outputs of the DC/RF discriminator are used to control amplitude and phase adjustment circuits of the adjustable circuit model, so as to automatically track amplitude and phase variations in the non-linear behavior of the flowcell, to mirror the characteristic impedance of the flowcell, thereby making the bridge insensitive to variations in the flowcell.

Abstract: A method for enumerating and distinguishing between blood cell populations in a biological sample includes the steps of contacting a biological sample with a cell membrane-permeant, red-excited, nucleic acid binding dye, without significantly disrupting the integrity of the cells; exciting this sample with light in one red wavelength; and measuring fluorescence emitted from different cell populations in the sample. This method is particularly desirable for enumerating different WBC subpopulations using flow cytometry. This method is also useful for enumerating reticulocytes or NRBC or mature RBC. This method is enhanced by pretreating the sample with a nucleic acid-specific blocking agent. Dyes useful in this method include, without limitation, SYTO®17 dye, SYTO®159 dye, SYTO®60 dye, SYTO®61 dye, SYTO®62 dye, SYTO®63 dye, and SYTO®64 dye.

Abstract: A new photoreceptor is provided which comprises a conductive substrate and a photoconductive layer of 5 micra or less in thickness on the substrate. The photoreceptor has a dark decay greater than 20 seconds and contains less than 5% total hydrogen. The substrate is selected from the group consisting of alloys of aluminum, chromium, iron, molybdenum, nickel or tungsten. In addition, the substrate can be a nonconductive material, such as plastic, provided with an electrically conductive layer. A new method for making the improved photoreceptor comprises providing a conductive substrate and forming a photoconductive layer of 5 micra or less in thickness on said substrate by depositing an amorphous material containing silicon and hydrogen atoms wherein said substrate has a negative potential between −40 and −100 volts during the forming of said layer.

Abstract: A Coulter apparatus comprises a volumeter assembly containing a conduit through which a particle suspension is caused to pass simultaneously with an electrical current. In preferred embodiments the volumeter assembly comprises at least one traditional Coulter conduit wafer, i.e., a dielectric wafer containing a central circular conduit, and at least two electrically conductive collars. The conductive collars approximate the conduit diameter in thickness, are uninsulated, and are attached to opposite sides of the conduit wafer, the openings being congruent with the Coulter conduit. The Coulter conduit in the dielectric wafer and the openings in the conductive collars collectively form a hydrodynamically smooth conduit, in which the electric and hydrodynamic fields of the Coulter conduit are amended. The electric field is shaped to confine the particle-sensitive zone of the novel volumeter conduit within the conduit's physical boundaries, thereby decreasing the zone's coincidence volume.