Abnormalities of factor VIII and platelet aggregation--use of ristocetin in diagnosing the von Willebrand syndrome.
(49/1409)
Ristocetin was used to study platelet aggregation in platelet-rich plasma and to assay the von Willebrand factor activity of factor VIII (VIII-VWF). Ristocetin-induced platelet aggregation (RIPA) was decreased in 13 of 18 patients with von Willebrand's disease (VWD) who had decreased plasma levels of VIII-VWF. The five patients with normal RIPA appeared to have mild VWD but did not constitute a separate subclass. RIPA was also abnormal in some patients with intrinsic platelet defects, but in no case was the defect corrected by normal plasma. The latter type of correction appears to be specific for VWD. Aspirin ingestion inhibited the second phase of RIPA (at low concentrations of ristocetin only) but did not affect the initial phase of aggregation or the level of VIII-VWF. We also studied a group of patients who had both abnormalities of the factor VIII complex and intrinsic platelet defects, such as impaired collagen-induced aggregation, as well. The findings in these patients and in those with typical von Willebrand's disease appear to comprise a spectrum of disorders (the von Willebrand syndrome) in which some abnormality of the factor VIII complex is associated with impaired platelet function. At present, ristocetin would appear to be a useful reagent for evaluating patients with bleeding disorders and for studying patients with the von Willebrand syndrome. (+info)
Heavy metal poisoning in glass worker characterised by severe.
(50/1409)
The paper presents the clinical description of the masticatory organ and biochemical assessment of dental tissue in a patient employed in a glassworks for 20 years. During 12 years the patient has suffered baldness ("Alopecia areata") and atypical extensive and non-healing cutaneous lesions. Dental examination revealed changes typical of chronic poisoning by cadmium and bismuth compounds. (+info)
Measurement of the force produced by an intact bull sperm flagellum in isometric arrest and estimation of the dynein stall force.
(51/1409)
The force generated by a detergent-extracted reactivated bull sperm flagellum during an isometric stall was measured with a force-calibrated glass microprobe. The average isometric stall force from 48 individual measurements was 2.5 +/- 0.7 x 10(-5) dyne (2.5 +/- 0.7 x 10(-10) N). The force measurements were obtained by positioning a calibrated microprobe in the beat path of sperm cells that were stuck by their heads to a glass microscope slide. The average position of the contact point of the flagellum with the probe was 15 microm from the head-tail junction. This average lever arm length multiplied by the measured force yields an estimate of the active bending moment (torque) of 3.9 x 10(-8) dyne x cm (3.9 x 10(-15) N x m). The force was sustained and was for the most part uniform, despite the fact that the flagellum beyond the point of contact with the probe usually continued beating. It appears that the dynein motors in the basal portion of the flagellum continue to pull in an isometric stall for as long as the motion of the flagellum is blocked. If dynein motors in the flagellum distal to the contact point with the probe were contributing force to the displacement of the probe, then the flagellar segment immediately past the point of contact would have to show a net curvature in the direction of the probe displacement. No such curvature bias was observed in the R-bend arrests, and only a small positive curvature bias was measured in the P-bend arrests. Our analysis of the data suggests that more than 90% of the sustained force component is generated by the part of the flagellum between the probe and the flagellar base. Based on this premise, the isometric stall force per dynein head is estimated to be 5.0 x 10(-7) dyne (5 pN). This equals approximately 1.0 x 10(-6) dyne (10 pN) per intact dynein arm. These values are close to the isometric stall force of isolated dynein. This suggests that all of the dynein heads between the base and the probe, on the active side of the axoneme, are contributing to the force exerted against the probe. (+info)
Preparation of DNA and protein micro arrays on glass slides coated with an agarose film.
(52/1409)
A thin layered agarose film on microscope slides provides a versatile support for the preparation of arrayed molecular libraries. An activation step leading to the formation of aldehyde groups in the agarose creates reactive sites that allow covalent immobilization of molecules containing amino groups. Arrays of oligonucleotides and PCR products were prepared by tip printing. After hybridization with complementary fluorescence labeled nucleic acid probes strong fluorescence signals of sequence-specific binding to the immobilized probes were detected. The intensity of the fluorescence signals was proportional to the relative amount of immobilized oligonucleotides and to the concentration of the fluorescence labeled probe. We also used the agarose film-coated slides for the preparation of protein arrays. In combination with specific fluorescence labeled antibodies these protein arrays can be used for fluorescence linked immune assays. With this approach different protein tests can be performed in parallel in a single reaction with minimal amounts of the binding reagents. (+info)
Microrobots for micrometer-size objects in aqueous media: potential tools for single-cell manipulation.
(53/1409)
Conducting polymers are excellent materials for actuators that are operated in aqueous media. Microactuators based on polypyrrole-gold bilayers enable large movement of structures attached to these actuators and are of particular interest for the manipulation of biological objects, such as single cells. A fabrication method for creating individually addressable and controllable polypyrrole-gold microactuators was developed. With these individually controlled microactuators, a micrometer-size manipulator, or microrobotic arm, was fabricated. This microrobotic arm can pick up, lift, move, and place micrometer-size objects within an area of about 250 micrometers by 100 micrometers, making the microrobot an excellent tool for single-cell manipulation. (+info)
Silanized nucleic acids: a general platform for DNA immobilization.
(54/1409)
We have developed a method for simultaneous deposition and covalent cross-linking of oligonucleotide or PCR products on unmodified glass surfaces. By covalently conjugating an active silyl moiety onto oligonucleotides or cDNA in solutions we have generated a new class of modified nucleic acids, namely silanized nucleic acids. Such silanized molecules can be immobilized instantly onto glass surfaces after manual or automated deposition. This method provides a simple and rapid, yet very efficient, solution to the immobilization of prefabricated oligonucleotides and DNA for chip production. (+info)
Laminin binding to beta1-integrins selectively alters beta1- and beta2-adrenoceptor signalling in cat atrial myocytes.
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1. Perforated patch recordings were used to determine how plating atrial cells on laminin alters beta-adrenergic receptor (beta-AR) regulation of L-type Ca2+ current (ICa,L). 2. Isoproterenol (isoprenaline; ISO; 0.01 microM), a non-selective beta-AR agonist, elicited a greater stimulation of ICa,L in cells plated on laminin (+79 +/- 16 %; n = 17) than on glass (+33 +/- 5 %; n = 23). Also, desensitization to ISO was greater in cells on laminin (-16 +/- 2 %) than on glass (-3 +/- 1 %). Atenolol (0.1 microM), a selective beta1-AR antagonist, inhibited the effects of ISO in cells on glass but not laminin. Conversely, 0.1 microM ICI 118,551, a selective beta2-AR antagonist, inhibited the effects of ISO in cells on laminin but not glass. With beta2-ARs blocked, ISO-induced stimulation of ICa,L was greater in cells on glass than laminin. 3. Zinterol (0.01-0.1 microM), a selective beta2-AR agonist, elicited a greater stimulation of ICa,L in cells on laminin than on glass. The effects of zinterol were blocked by ICI 118,551. 4. ISO-induced stimulation of ICa,L was greater in cells plated on an alphabeta1-integrin antibody than on glass. Also, addition of 20 microM cytochalasin D to cells on laminin prevented the enhanced effects of ISO typically elicited in cells on laminin alone. 5. We conclude that laminin binding to alphabeta1-integrins, in conjunction with the actin cytoskeleton, reduces beta1-AR and enhances beta2-AR signalling which regulates ICa,L. This novel mechanism may contribute to remodelling of beta-AR signalling in the failing heart. (+info)
Splenic mediated erythrocyte cytotoxicity in malaria.
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Cell-mediated cytotoxicity in virulent rodent malaria has been demonstrated in vitro, whereby splenic cells effected specific lysis of 51Cr-labelled erythrocytes from parasitized animals. More than one cellular cytolytic effector system appeared to be operative in the mouse. One effector system involved splenic macrophages, from normal or immune animals, which were increasingly cytotoxic to target cells in the presence of antibody. A second effector system involved nylonpurified immune spleen cells which were significantly more cytotoxic than similary prepared normal spleen cells in the presence of immune serum. Although antibody alone was not cytolytic, the data strengthen the concept that immune spleen cells and antibody can interact in a co-operative fashion to mediate cytotoxic reactions in malaria. (+info)