Reversible temperature-controlled gelation in mixtures of pNIPAM microgels and non-ionic polymer surfactant.

We investigate the reversible gelation of poly(N-isopropylacrylamide) (pNIPAM) microgels in the presence of triblock-copolymer (PEO-PPO-PEO type) surfactant. We demonstrate that the association of these polymers with the microgel particles at elevated temperature is responsible for the gelation, due to the temperature responsive nature of the components. This is highlighted by an increase in the apparent hydrodynamic diameter of the particles in dynamic light scattering experiments, which only occurs above the volume phase transition temperature of pNIPAM. The gels that result shrink over a time period much larger than that of the collapse of pNIPAM microgels, and retain the shape of the container they form in. We investigate the mechanism that leads to this gelation and the structure of the gels that result. Confocal microscopy experiments show that both polymers are present in the gel network, indicating that an associative mechanism is responsible for the gelation. We vary the pNIPAM particle architecture to further investigate the gelation process, and find that the cross-link distribution plays a key role in the gelation mechanism, where for uniformly cross-linked particles the gelation is not observed. This shows that the fuzzy corona of the pNIPAM microgels is involved in the association of the polymers, allowing the triblock-copolymer to penetrate the outer corona of the microgels and bridge the particles. The phase transition observed is close to physiological conditions, so these gels have the potential for use in biomedical applications, including tissue engineering.

Detecting fetomaternal hemorrhage: a comparison of five methods.

Appropriate postpartum administration of Rh immune globulin relies on sensitive detection and accurate quantitation of fetomaternal hemorrhage (FMH). Recently, the microscopic Du test (micro Du) enhanced with polyethylene glycol (PEG Du) and flow cytometry (FC) have been advocated for this purpose. Three qualitative methods (micro Du, rosette test, and PEG Du) and two quantitative methods (acid elution and FC) for assessing FMH were evaluated with particular attention given to PEG Du and FC. In vitro studies comprised 10 series of dilutions of D+ cord cells in D- adult cells to yield D+ cell concentrations of 0.06, 0.12, 0.25, 0.50, 0.75, 1.0, and 2.0 percent. Additionally, 26 postpartum samples were tested. Of the qualitative techniques, the micro Du test was the least sensitive with 20 percent false-negative results occurring at 0.5 percent fetal cells. The PEG Du test was only slightly more sensitive and offered no clinical advantage. The rosette test was the most sensitive, consistently detecting fetal cells at concentrations of 0.25 percent or greater. FC and acid elution showed similar results, with good correlation obtained between measured and expected quantities of fetal cells (r = 0.99 and 0.96, respectively). One of 26 postpartum samples was positive by all screening techniques; acid elution and FC detected 0.3-percent concentrations of fetal cells and 0.17-percent concentrations of D+ cells, respectively. Although acid elution is a more commonly used method for quantitating FMH, FC offers an acceptable alternative that is capable of analyzing large numbers of cells with objectivity and reproducibility.

Richter's syndrome presenting as primary central nervous system lymphoma. Transformation of an identical clone.

The development of a central nervous system (CNS) large cell lymphoma in a patient simultaneously diagnosed with chronic lymphocytic leukemia (CLL) is reported. Although differences in phenotypic expression were demonstrated in study of the peripheral blood and CNS disease, identical immunoglobulin gene rearrangements were identified, providing evidence for evolution of two morphologically distinct neoplasms from the same clone. Beyond histologic transformation, acquisition of an aneuploid cell population in the CNS tumor was demonstrated by analysis of DNA content. Isolated parenchymal involvement of the CNS by large cell transformation of CLL has not been previously described; its relationship to CNS lymphoma and Richter's syndrome are reviewed.

Glycohemoglobin quantitation by alkaline gel electrophoresis. A reliable technique with practical clinical advantages.

The Beckman Paragon alkaline gel electrophoresis system was evaluated for utility in identification and quantitation of glycosylated hemoglobin in the clinical laboratory setting. In contrast to other alkaline hemoglobin electrophoresis systems, this system provides adequate separation of HbA0 from its glycosylated form. A band anodal to HbA0 was identified as glycohemoglobin; in vitro synthesis of glycohemoglobin confirmed the migration pattern of the glycohemoglobin band. In both in vitro synthesis studies and in a series of 48 patients, quantitation of the glycohemoglobin band by densitometry showed good correlation (r = 0.99 and r = 0.96, respectively) with values obtained by a standard column chromatographic technique. Beyond reliable quantitation of glycohemoglobin, this system offers two advantages. First, it discriminates hemoglobin F and hemoglobins with low isoelectric points that may coincidentally be measured as glycohemoglobin by other techniques. Second, it provides simultaneous detection of common hemoglobinopathies, a necessity for accurate reporting of glycohemoglobin in the diabetic patient with a concomitant hemoglobinopathy.

Primary lymph node presentation of angiocentric lymphoma associated with features of a hemophagocytic syndrome.

The spectrum of post-thymic T-cell neoplasia includes the angiocentric immunoproliferative lesions, a group of disorders histologically exhibiting vascular infiltration and destruction; included among these disorders is angiocentric lymphoma. In contrast to the typical extranodal presentation seen in the angiocentric immunoproliferative lesions, this report describes a case of angiocentric lymphoma presenting as primary lymph node disease with clinicopathologic findings mimicking a hemophagocytic syndrome. Rearrangement of the T-cell receptor beta chain documents this case to be a clonal T-cell neoplasm. The association of this distinct histologic type of T-cell malignancy with hemophagocytic syndromes is reviewed.