Median Filtration Research Articles

Clotting time by free oscillation rheometry and visual inspection and a viscoelastic description of the clotting phenomenon

An automated procedure for determination of clotting time in whole blood was validated by direct comparison with the reference method, visual clotting time determination. The procedure was based on a 10 Hz free oscillation rheometer (FOR) of our design, the ReoRox®4. Recalcified citrated blood samples (n=30), clotting in the range 4 to 20 min, were used in the validation. Every 30 s of the analysis, as the change in stiffness (ΔG*) of the sample was monitored by FOR, the sample cup was shortly removed from the FOR and its contents inspected for first signs of clotting, i.e. visual clotting time determination. Various FOR clotting criteria were attempted. Best correlation to visual clotting time was found when ΔG* reached 0.01 Pa, which yielded linear regression slope, intercept and r2 of 0.98, 0.09 min and 0.98, respectively. For comparison, six plasma samples were analyzed in the same way and gave almost the same results. The accuracy of the FOR determinations was checked by also analyzing, in parallel, portions of the sample with a conventional oscillation rheometer, a Bohlin VOR. The rationale is given for preferring ΔG* over G* as a FOR monitoring function in coagulation tests and for including median filtration of the primary FOR data. An extension of the FOR theory to include ΔG* and evidence in support of inhomogeneous blood clotting are also given.

Optimal conditions for white cell reduction in red cells by filtration at the patient's bedside.

A quality control program of white cell (WBC) reduction in red cells at the bedside was implemented, based on postfiltration counting in a Nageotte chamber of the residual WBCs from samples taken from a segment of the transfusion set, after 1-in-10 sample dilution with Türks's solution. During a 1-year quality control program, 5.1 percent of counted units had apparent filtration failures, that is, WBC counts exceeding 5 x 10(6) per unit. The cause(s) for these apparent failures were investigated. In Study 1, residual WBCs from 150 buffy coat-free red cells filtered through one type of filter at 4 degrees C, 20 to 24 degrees C, or 27 degrees C in 5 to 10 minutes, 50 to 100 minutes, or 100 to 200 minutes were counted as described above. In Study 2, residual WBCs in samples collected from segments of the transfusion set and from the postfiltration bags were counted in parallel by a new, more sensitive counting method. In this method, 5 mL of filtered red cells was diluted with 20 mL of 3-percent paraformaldehyde and centrifuged, the pellet was resuspended to 500 microL with a lysis solution, and the WBCs were counted in a Nageotte chamber. In Study 3, residual WBCs were counted by the 3-percent paraformaldehyde method in samples from postfiltration bags of 1- to 2-day-old buffy coat-rich red cell units filtered through a second type of filter. Filtration was started within 30 minutes of the removal of the unit from the refrigerator, ambient temperature was 20 to 24 degrees C, and the median filtration time was 90 minutes per unit. Study 1: Median WBC counts per unit increased progressively from 51,000 at 4 degrees C to 934,000 at 27 degrees C, with intermediate values at 20 to 24 degrees C. In no unit did the WBC count exceed 5 x 10(6) if filtration at 20 to 24 degrees C was completed within 100 minutes, while counts in excess of 50 x 10(6) were found at 20 to 24 degrees C and at 27 degrees C with filtration times of 100 to 200 minutes, and 50 to 100 minutes, respectively. Study 2: The relation between segment and postfiltration bag WBC counts obtained by the 3-percent paraformaldehyde method was poor, with the latter being almost always lower than the former. Study 3: None of the 120 units filtered through the second type of filter at 20 to 24 degrees C in 50 to 100 minutes contained more than 3.2 x 10(6) WBCs; the median value was 147,000 WBCs per unit. On the basis of the results with the 3-percent paraformaldehyde method, which showed the unreliability of segment counts, a new policy was adopted for quality control of bedside WBC reduction, based on controlling the time of and temperature at transfusion. Bedside WBC reduction in 1- to 2-day-old red cells performed with the second type of filter at 20 to 24 degrees C in less than 100 minutes per unit allowed the preparation of units that meet the standard of fewer than 5 x 10(6) WBCs in all tested cases. Bedside WBC reduction with the second type of filter and under the controlled conditions reported seems effective.

Computer-assisted three-dimensional reconstruction of the hippocampal region based on serial sections

A large series of rabbit hippocampal Neo-Timm stained sections were manually aligned, digitized, and by a modified median filtration noise reduced and reconstructed into a three-dimensional object. From the presented simulated grey tone cuts of this object, the reader may assemble a rabbit hippocampal model, that spatially illustrates its anatomy.

In situ filtering and ingestion rates of deep-sea benthic boundary-layer zooplankton in the Santa Catalina Basin

In situ rates of filtration, particulate ingestion, and carbon ingestion of deep-sea benthic boundary-layer zooplankton were determined in December 1984 in the Santa Catalina Basin, at 1 300 m depth in the California Borderland, by a short-term radioisotope-incorporation technique. Zooplankton were collected at 1 or 50 m above the bottom with an opening-closing net system on a submersible, and incubated at depth with labelled amino acids in special cod-end chambers. Concentrations of particulate material and particulate organic carbon in the ambient water were also measured. The zooplankton had a median weight-specific filtration rate of 12.4 ml (mg dr. wt)-1 h-1 and a median carbon ingestion rate of 5.4 μg C (mg dr. wt)-1 h-1. Filtration rates were not significantly different from those in similar experiments in the north Atlantic at 2 175 m depth or Narragansett Bay in the winter, although the medians of the deep-sea experiments were lower than for the Bay. In the Santa Catalina Basin, rates from experiments at 1 m above the bottom in more turbid water were not significantly different from those at 50 m above the bottom in clearer water. These deep-sea benthic boundary-layer zooplankton may have the potential to respond to food pulses, and their relatively high ingestion rates suggest that they could have significant effects on particulate, chemical, and bacterial processes in the near-bottom water column.

Nephrotoxicity of cis-diamminedichloride platinum (CDDP) during remission-induction and maintenance chemotherapy of testicular carcinoma

We studied renal function in nine patients with disseminated testicular carcinoma before and after remission-induction and maintenance therapy with a drug combination containing cis-platinum. The median glomerular filtration rate (GFR) decreased during remission-induction therapy from 146 to 118 ml/min. No effect of cumulative toxicity on the median GFR was found during maintenance therapy, nor did the median GFR improve. The median effective renal plasma flow (ERPF) decreased during the total period from 705 to 514 ml/min. No significant changes in median filtration fraction (FF) and serum creatinine were observed. It is suggested that intrarenal hemodynamic effects are important in the nephrotoxicity of cis-diamminedichloride platinum (CDDP).