Evidence for an alternative mechanism of human platelet secretion involving peripheralization of secretory granules and formation of membrane-associated multivesicular structures

Stimulated platelets release the content of their granules to the environment by a process known as platelet secretion. The precise mechanism of platelet secretion is poorly understood. The most widely-held theory suggests that, during platelet activation, secretory granules centralize and their content is released into the surface-connected canalicular system. Using fixation techniques directed at preserving membrane structures, morphological evidence is provided that human platelet activation is associated with secretory granules migrating to the periphery of platelets, where they undergo transition to participate in the formation of membrane-associated multivesicular structures. These multivesicular structures then undergo dissolution resulting in granule content secretion to the environment. The formation of the membrane-associated multivesicular structures occurs in platelets in which some of the secretory granules have also become centralized. This suggests that during the activation of human platelets, membrane-associated multivesicular structure release may occur concurrently with other mechanisms of secretory granule content release. The present observations are consistent, however, with the hypothesis that during human platelet activation the formation of membrane-associated multivesicular structures by platelet secretory granules contributes importantly to the mechanism of platelet secretion.     

Assessment methods for physical activity and physical fitness in population studies: report of a NHLBI workshop

This report summarizes the proceedings and recommendations of a National Heart, Lung, and Blood Institute conference on assessment methods for physical activity and physical fitness in population studies held in Bethesda, Maryland, in May, 1984. Synopses of each contributor's presentation are given, as well as specific recommendations for further research. Key areas for investigation were noted as validation and standardization of questionnaires, increased use of activity monitors in exercise research, development of simpler fitness tests, and research into possible surrogate measures for fitness evaluation.     

Air Kerma Rate estimation by means of in-situ gamma spectrometry: A Bayesian approach

Bayesian inference is used to determine the Air Kerma Rate based on in-situ gamma spectrum measurement performed with an NaI(Tl) scintillation detector. The procedure accounts for uncertainties in the measurement and in the mass energy transfer coefficients needed for the calculation. The WinBUGS program (Spiegelhalter et al., 1999) was used. The results show that the relative uncertainties in the Air Kerma estimate are of about 1%, and that the choice of unfolding procedure may lead to an estimate systematic error of 3%.     

Isomers of bilirubin glucuronide in serum and bile before and after relief of common duct obstruction

Isomers of bilirubin glucuronide with the bilirubin acyl group attached to the C1-, C2-, C3- and C4-positions of the glucuronyl residue are present in bile of patients with extrahepatic cholestasis, whereas in normal bile only C1-isomers are found. In the present study, these bilirubin glucuronide isomers, and the fractions of unconjugated bilirubin, and bilirubin mono- and diconjugates were determined in serum and bile of 8 patients before and after relief of common duct obstruction by endoscopic papillotomy. Before papillotomy we found 39.6% C1-isomers (median value), 22.2% C2-isomers, 19.3% C3-isomers and 11.4% C4-isomers in the bile. The values in serum before papillotomy were comparable. Twenty-four hours after papillotomy, the level of C1-isomers in bile increased significantly to 56.3% (P less than 0.05) with a concomitant decrease of the non-C1-isomers. In contrast, in serum the isomers of bilirubin glucuronide did not change significantly at 24 h after papillotomy. Before papillotomy, the fraction of unconjugated bilirubin in bile was 3.6% of the total, with 15.8% bilirubin monoconjugates and 75.5% bilirubin disconjugates. After papillotomy, unconjugated bilirubin decreased to 1.6% (n.s.) and bilirubin monoconjugates to 11.9% (n.s.), while bilirubin diconjugates increased to 86.1% (P less than 0.05). In serum, the elevated fractions of bilirubin diconjugates and monoconjugates decreased from 38.4 to 32.2% (P less than 0.05) and from 29.6 to 23.4% (n.s.), respectively. In parallel, the fraction of unconjugated bilirubin in serum increased from 24.1 to 37.0% (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Chemical-composition distribution of a diblock copolymer

The experimentally determined distribution of the chemical composition of styrene/butadiene block copolymers reported by Kuhn is compared with the results of a model calculation assuming that the constituent blocks have a gamma (Schulz-Zimm) distribution of molecular weights and the ratios of weight- to number-average molecular weights are M?_w/M?_n = 1,025 or M?_w/M?_n = 1,05. A good agreement is found between experimental and calculated distributions.     

Prognosis of children with mixed phenotype acute leukemia treated on the basis of consistent immunophenotypic criteria

Background

Mixed phenotype acute leukemia (MPAL) represents a diagnostic and therapeutic dilemma. The European Group for the Immunological Classification of Leukemias (EGIL) scoring system unambiguously defines MPAL expressing aberrant lineage markers. Discussions surrounding it have focused on scoring details, and information is limited regarding its biological, clinical and prognostic significance. The recent World Health Organization classification is simpler and could replace the EGIL scoring system after transformation into unambiguous guidelines.

Design and Methods

Simple immunophenotypic criteria were used to classify all cases of childhood acute leukemia in order to provide therapy directed against acute lymphoblastic leukemia or acute myeloid leukemia. Prognosis, genotype and immunoglobulin/T-cell receptor gene rearrangement status were analyzed.

Results

The incidences of MPAL were 28/582 and 4/107 for children treated with acute lymphoblastic leukemia and acute myeloid leukemia regimens, respectively. In immunophenotypic principal component analysis, MPAL treated as T-cell acute lymphoblastic leukemia clustered between cases of non-mixed T-cell acute lymphoblastic leukemia and acute myeloid leukemia, while other MPAL cases were included in the respective non-mixed B-cell progenitor acute lymphoblastic leukemia or acute myeloid leukemia clusters. Analogously, immunoglobulin/T-cell receptor gene rearrangements followed the expected pattern in patients treated as having acute myeloid leukemia (non-rearranged, 4/4) or as having B-cell progenitor acute lymphoblastic leukemia (rearranged, 20/20), but were missing in 3/5 analyzed cases of MPAL treated as having T-cell acute lymphobastic leukemia. In patients who received acute lymphoblastic leukemia treatment, the 5-year event-free survival of the MPAL cases was worse than that of the non-mixed cases (53±10% and 76±2% at 5 years, respectively, P=0.0075), with a more pronounced difference among B lineage cases. The small numbers of MPAL cases treated as T-cell acute lymphoblastic leukemia or as acute myeloid leukemia hampered separate statistics. We compared prognosis of all subsets with the prognosis of previously published cohorts.

Conclusions

Simple immunophenotypic criteria are useful for therapy decisions in MPAL. In B lineage leukemia, MPAL confers poorer prognosis. However, our data do not justify a preferential use of current acute myeloid leukemia-based therapy in MPAL.     

Drug-excipient compatibility testing-Identification and characterization of degradation products of phenylephrine in several pharmaceutical formulations against the common cold

Different pharmaceutical preparations against the common cold containing phenylephrine (PHE) and saccharose were studied. New impurities were discovered in these preparations after exposure using isocratic ion-pair chromatography separation on a C18 column. LC-MS and NMR techniques were employed to identify and to fully characterize these new compounds. The products were identified as 1-[5-(hydroxymethyl)-2-furyl]-2-methyl-1,2,3,4-tetrahydroisochinolin-4,8-diol and 1-[5-(hydroxymethyl)-2-furyl]-2-methyl-1,2,3,4-tetrahydroisochinolin-4,6-diol. Identification of these degradation products allowed to understand and to confirm their formation mechanism. The developed HPLC method separates of all known impurities and impurities originated from PHE as well.