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Biomedical subjects

J C Fratantoni

Publications and source records attributed to J C Fratantoni.

At least 37 records · Page 2Linked to original sources
PubMed1992

Effects of two viral inactivation methods on platelets: laser-UV radiation and merocyanine 540-mediated photoinactivation.

Two viral inactivation methods suggested for use with cellular blood products have been evaluated as to their effects on platelets. In the first study, it was proposed that pulsed laser-ultraviolet radiation (UVB) at 308 nm could favor photodamage to UVB-sensitive viral nucleic acid with minimal effects on blood platelets. A "window of efficacy" was observed with UVB doses of 10.5-21.5 J/cm2 at which 4-6 log10 poliovirus were inactivated while platelets were relatively tolerant. However, this "window" occurred only with low-intensity UVB radiation (less than or equal to 0.25 MW/cm2). Damage to platelet proteins, evident at high laser intensities, was probably due to multiple photon excitation of amino acids. In the second study, platelets and viruses were treated with the photosensitizer, merocyanine 540 (MC 540) (less than or equal to 24 micrograms/ml), and visible light (450-600 nm) (less than or equal to J/cm2). Activation of washed platelets by dye/light treatment resulted in a spontaneous release of serotonin, spontaneous aggregation, and marked morphological changes. Increasing concentrations of albumin in the suspension medium protected against dye-mediated photodamage to platelets, but also significantly reduced the antiviral activity of MC 540 and light. These results illustrate the relative sensitivities of platelets and viruses to two inactivation methods and the difficulty in optimizing inactivation of viruses and preservation of platelet function in a protein-rich medium.

Blood↗
PubMed1991

Inhibition by albumin of merocyanine 540-mediated photosensitization of platelets and viruses.

The effect of the photosensitizer merocyanine 540 (MC 540) on platelets and on three marker viruses was examined to assess its potential in reducing virus transmission by blood products. The results demonstrated several deleterious effects of MC 540 (4-24 micrograms/mL) on platelet morphology and function in both the absence and presence of light (450-600 nm). Treatment of washed platelets with MC 540 in the dark resulted in a significant release of serotonin in the absence of added agonist, as well as a diminished response to thrombin as measured in vitro. In addition, photosensitization caused spontaneous platelet aggregation and release of 92 percent of the releasable serotonin without the addition of an agonist. Because photo-treatment of blood products is likely to be performed in a protein-rich medium, the influence of albumin on the phototoxic effects on platelets was assessed. Albumin added to the suspension medium at concentrations greater than or equal to 1.0 percent protected the platelets against the effects of MC 540 in the dark, whereas 5-percent albumin was required for protection against the phototoxic effects of MC 540 on the platelet response to thrombin. The antiviral activity of MC 540 and light was examined by using the lipid-containing viruses herpes simplex virus (HSV) and bacteriophages phi 6 and PM2. Of the lipid-enveloped viruses, HSV was 25 times more photosensitive to MC 540 than was phi 6 (15 micrograms/mL). PM2, which has an internal lipid layer, was almost 300 times less sensitive to MC 540 and light than was HSV.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacteriophages↗
PubMed1990

Measuring platelet aggregation with microplate reader. A new technical approach to platelet aggregation studies.

Platelet aggregation measurements were done with the use of a commercially available microtiter plate reader with specific modification of the mode of agitation of the samples. Satisfactory aggregation curves were obtained with use of an external horizontal agitator, with an amplitude of 1.3 mm and minimum frequency of 1,360 cycles/minute. With the use of the 96 available wells in the microtiter plates, all test and control platelet samples, with replicates, were observed simultaneously and the output data obtained within 10-15 minutes. The technique was validated by demonstrating the similarity of dose-response curves, obtained with a standard aggregometer and with the microtiter technique, of platelets stimulated by adenosine diphosphate, thrombin, and arachidonic acid.

Humans↗
PubMed1987

Ouabain affects platelet reactivity as measured in vitro.

Ouabain, a digitalis glycoside and an inhibitor of the Mg2+-dependent Na+-K+ ATPase, was used to probe the role of intracellular Na+ levels in the regulation of platelet reactivity. Platelets preincubated with 10 to 150 microM ouabain exhibited a potentiated aggregation response to collagen (14.4 to 180 micrograms/mL), ADP (4 to 12 microM) and thrombin (0.03 to 0.10 unit/mL). Ouabain markedly decreased the time interval between addition of collagen and the onset of shape change. At submaximal concentrations of collagen, thrombin and ADP, preincubation with ouabain increased the rate and amplitude of the aggregation response. Irreversible aggregation was achieved in ouabain-treated platelets by using concentrations of ADP which induced only reversible aggregation in the absence of ouabain. In addition, chelation of extracellular calcium with EGTA or EDTA (2 mM) failed to block reactivity to collagen, ADP or thrombin in ouabain-treated platelets. These results suggest that ouabain induces a "preactivation state" in platelets, perhaps via modulation of intracellular Na+ levels.

Adenosine Diphosphate↗
PubMed1987

Use of laser-UV for inactivation of virus in blood products.

Inactivation of virus by UV radiation was examined as a potential method for sterilization of blood products. Samples of attenuated poliovirus, platelets and plasma were uniformly irradiated with a XeCl excimer laser that delivered 40 nsec pulses of UV at 308 nm (UVB308). Intensities and exposure does were varied from 0.11 to 1.40 MW/cm2 and 0.51 to 56.0 J/cm2, respectively. In studies conducted with low intensity UVB308 (less than or equal to 0.17 MW/cm2), using exposure doses greater than or equal to 10.8 J/cm2, it was possible to inactivate poliovirus by 4 to 6 log10. Platelets irradiated with doses less than or equal to 21.5 J/cm2 exhibited minimal damage as assessed by aggregation activity and spontaneous release of serotonin. Examination of the coagulation activity of irradiated plasma indicated that exposure doses less than or equal to 21.5 J/cm2 resulted in less than 20% increase in prothrombin and partial thromboplastin times. The use of UVB308 at a higher intensity (1.4 MW/cm2) over a similar range of exposure doses did not enhance viral inactivation but did result in increased damage to platelet and plasma proteins. These results demonstrate that at 308 nm there exists a "window of efficacy" for exposure doses between 10.8 and 21.5 J/cm2 and peak intensities less than or equal to 0.17 MW/cm2 in which a hardy virus is significantly inactivated and platelets and plasma proteins are, by functional criteria, minimally affected. Increased viral inactivation cannot be accomplished with higher UV intensities and will require additional or alternate measures.

Blood↗
PubMed1984

Aberrant morphology of platelets stored in five day containers.

Platelets for transfusion, stored in either of two new types of container (PL-732 and CLX), demonstrated unusual morphological alterations after 2 or 3 days of storage. The atypical forms observed included crescents, elongated tubular forms and rings. Development of these forms was not seen if the permeability of the container was inhibited and the pH kept below 6.7. The variables which differentiate these new containers from those previously used, and which appear to be related to the changes described, are pH, pO2 and presence of a leachable plasticizer. The functional behaviour of these platelets, as assessed by serotonin uptake and resistance to hypotonic shock, was not different from that of control platelets.

Blood Platelets↗
PubMed1984

Quantitative assessment of platelet morphology by light scattering: a potential method for the evaluation of platelets for transfusion.

Normal fresh platelets are discoid, and platelets that have been stored become spherical. Discoid morphology correlates with normal viability and imparts to a platelet suspension a "streaming" appearance when agitated. We developed a device that quantitates the percent of discoid cells in a suspension by means of laser light scattering at low angles. It performs this assay within 3 minutes on platelets contained in a plastic blood bag. The ability of the device to quantitate discoid platelets was demonstrated in the following ways: (1) comparison of percentage discs calculated from light-scattering data with visually observed optical streaming; (2) correlation of percentage discs from light scattering with the percentage determined by phase microscopy; and (3) observation of changes during room temperature storage. Platelet suspensions containing extreme (dendritic and balloon) forms were examined, and we conclude that these forms do not significantly affect the light-scattering assay. The optical measurements were also used to accurately approximate the total platelet counts of the suspensions. This device may have a role in the evaluation of platelets for transfusion.

Blood Platelets↗
PubMed1977

Thrombolytic therapy.

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Arterial Occlusive Diseases↗
PubMed1975

Heparin-induced thrombocytopenia: confirmation of diagnosis with in vitro methods.

Profound thrombocytopenia developed in a patient during treatment with heparin for venous thrombosis. The platelet count increased toward normal when heparin administration was stopped, but fell abruptly when the drug was again given. Platelet aggregation occurred when heparin was added to the patient's platelet-rich plasma, or to normal platelets plus the patient's serum. This serum also effected release of 3H-serotonin from normal platelets. This pattern of aggregation was clearly different from that occasionally caused by heparin in a control population. The data is consistent with an effect of heparin on platelets, possibly mediated by on immune mechanism.

Adenoma, Chromophobe↗