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The diagnosis of the myeloproliferative neoplasms (MPN)‒ essential thrombocythaemia (ET) and primary myelofibrosis (PMF) ‒ in patients lacking a molecular marker is challenging. Recently, mutations in exon 9 of the calreticulin gene (CALR) have been described in around one-third of ET and MF patients (Klampfl et al, 2013a; Nangalia et al, 2013). Notably, these mutations are almost always seen in JAK2 V617F-negative and MPL-non-mutated patients and account for the majority of these cases. Such is the prevalence of these mutations we suggest that they are added to the British Committee for Standards in Haematology criteria for the diagnosis of ET and also PMF (Harrison et al, 2010; Reilly et al, 2012) (evidence grade 1A). The modified diagnostic criteria and algorithms are shown in

Clostridium perfringens sialidase was purified by affinity chromatography. Kinetic properties of the enzyme were examined with sialyllactose and with mixed sialoglycolipids (gangliosides) as substrates. With the latter substrate in 0.01 M Tris-acete in the absence of strong electrolyte, the pH optimum for enzymatic activity was 6.8. Addition of strong electrolyte (0.01 to 0.10 M Nac1) to the reaction medium caused an acidic shift and a broadening of the pH optimum, Enzymatic activity at pH 5.8 rose approximately 2.5-fold; a concomitant loss of activity at pH 6.8 was also observed. The alteration of enzymatic activity caused by strong electrolyte were dependent upon changes in Vmax. Km remained nearly invariant. Thus, a reversible transition of the enzyme from a relatively inactive to a highly active form occurred as a function of strong electrolyte concentration. Determination of the pK values of the active functional groups of C. perfringens sialidase revealed that the effects of strong electrolyte were exerted upon the pKa group of the enzyme. Strong electrolyte appeared to shield unfavorable electrostatic interactions between polyanionic sialoglycolipid micelles and the enzyme molecule, thus protecting the pKa group from inactivation. In comparision with the effects of strong electrolyte upon enzymatic activity toward the sialoglycolipid substrate, those observed with the monovalent substrate, sialyllacthose, were minor. Collectively, these findings indicate that ionic environment may effectively control the activity and relative substrate specificity of C. perfringens sialidase at a given pH. Furthermore, they explain the low pH optima and skewed pH profiles previously reported for enzymatic activity toward high molecular weight substrates.