The role of automated urine particle flow cytometry in clinical practice.

Urine particle flow cytometers (UFC) have improved count precision and accuracy compared to visual microscopy and offer significant labor saving. The absence of an internationally recognized reference measurement procedure, however, is a serious drawback to their validation. Chamber counting by phase contrast microscopy of supravitally-stained uncentrifuged urine is considered the best candidate for reference. The UF-100 (Sysmex Corporation, Japan) identifies RBC, WBC, squamous epithelial cells, transitional epithelial and renal tubular cells (SRC), bacteria, hyaline and inclusional casts, yeast-like cells, crystals and spermatozoa, using argon laser flow cytometry. Evaluations have established acceptable linearity over useful working ranges, with an imprecision that is consistently and significantly less than microscopy, and with negligible carry-over. Comparisons of UFC with chamber counts, quantitative urine microscopy, sediment counts, test strips, bacterial culture and urine density are reviewed. Clinical studies include diagnosis and monitoring of urinary tract infection; localization of the sites of hematuria; and diagnosis, monitoring and exclusion of renal disease. The most popular approach is to combine test strips with UFC for primary screening either always by both methods or by using test strips for analytes unrelated to particles analyzed by UFC. Expert systems now exist combining both test modalities based on user definable decision rules. The implementation of such a strategy significantly reduces microscopy review and saves time and expense without diminishing clinical utility.

Conversion of the maltogenic alpha-amylase Novamyl into a CGTase.

Novamyl is a thermostable five-domain maltogenic alpha-amylase that shows sequence and structural homology with the cyclodextrin glycosyltransferases (CGTases). Comparing X-ray crystal structures of Novamyl and CGTases, two major differences in the active site cleft were observed: Novamyl contains a loop insertion consisting of five residues (residues 191-195) and the location of an aromatic residue known to be essential to obtain an efficient cyclization reaction. To convert Novamyl into a cyclodextrin (CD)-producing enzyme, the loop was deleted and two substitutions, F188L and T189Y, were introduced. Unlike the parent Novamyl, the obtained variant is able to produce beta-CD and showed an overall conversion of starch to CD of 9%, compared with CGTases which are able to convert up to 40%. The lower conversion compared with the CGTase is probably due to additional differences in the active site cleft and in the starch-binding E domain. A variant with only the five-residue loop deleted was not able to form beta-CD.

Electrostatics in the active site of an alpha-amylase.

The importance of electrostatics in catalysis has been emphasized in the literature for a large number of enzymes. We examined this hypothesis for the Bacillus licheniformis alpha-amylase by constructing site-directed mutants that were predicted to change the pKa values of the catalytic residues and thus change the pH-activity profile of the enzyme. To change the pKa of the catalytic residues in the active site, we constructed mutations that altered the hydrogen bonding network, mutations that changed the solvent accessibility, and mutations that altered the net charge of the molecule. The results show that changing the hydrogen bonding network near an active site residue or changing the solvent accessibility of an active site residue will very likely result in an enzyme with drastically reduced activity. The differences in the pH-activity profiles for these mutants were modest. pH-activity profiles of mutants which change the net charge on the molecule were significantly different from the wild-type pH-activity profile. The differences were, however, difficult to correlate with the electrostatic field changes calculated. In several cases we observed that pH-activity profiles shifted in the opposite direction compared to the shift predicted from electrostatic calculations. This strongly suggests that electrostatic effects cannot be solely responsible for the pH-activity profile of the B. licheniformis alpha-amylase.

Comparison of the tumor associated proteases cathepsin D (CATH D) and urokinase-type plasminogen activator (uPA) in cytosols of human breast cancer patients.

As a matter of routine, prepared cytosols of human primary breast cancer specimens (n = 230) are analysed for both CATH D and hormone receptor status (ER,PR). Retrospectively, uPA was determined in the samples. The selection criterion for the retrospective analysis was the possibility of a longitudinal follow-up of the patients. All tumor stages were included, but the main emphasis was on lower tumor stages (T1, and T2) as well as nodal negative stages (N0). The results of the hormone receptor status (ER,PR) were: ER+PR+ 66.37%; ER+PR- 10.18%, ER-PR+ 10.18%, ER-PR- 13.27%. The CATH D results ranged from 5 to 246 pmol/mg protein. 30.97% of these results rose above 50 pmol/mg protein (positive), 42.48% were below 35 pmol/mg protein (negative). The uPA results ranged from 0.05 to 3.74 ng/mg protein. 27.43% of the uPA results rose above 0.71 ng/mg protein (positive), 58.85% were below 0.53 ng/mg protein (negative). Raised results of uPA are distinct in the higher tumor stages (T1N0 > T2N0 > T2N1 > T4Nx). Although the CATH D and uPA measurements showed similar results (positive/negative distribution) in the general survey, the confirmity of both factors is rather limited if it is focused to single cases. Between CATH D and uPA there was a confirmity of 50% (T1N0) of 45.5% (T2N0) respectively in the range of positive results, and there was a confirmity of 60.3% (T1N0) and 65.8% (T2N0), respectively, in the range of negative results. Differences were seen in 19.2% (T1N0) and 22.7% (T2N0), respectively, in the range of positive results, and in 20.6% (T1N0) in 1508% (T2N0), respectively, in the range of negative results. The prospectively diagnostic value of these is still under observation.

X-ray structure of Novamyl, the five-domain "maltogenic" alpha-amylase from Bacillus stearothermophilus: maltose and acarbose complexes at 1.7A resolution.

The three-dimensional structure of the Bacillus stearothermophilus "maltogenic" alpha-amylase, Novamyl, has been determined by X-ray crystallography at a resolution of 1.7 A. Unlike conventional alpha-amylases from glycoside hydrolase family 13, Novamyl exhibits the five-domain structure more usually associated with cyclodextrin glycosyltransferase. Complexes of the enzyme with both maltose and the inhibitor acarbose have been characterized. In the maltose complex, two molecules of maltose are found in the -1 to -2 and +2 to +3 subsites of the active site, with two more on the C and E domains. The C-domain maltose occupies a position identical to one previously observed in the Bacillus circulans CGTase structure [Lawson, C. L., et al. (1994) J. Mol. Biol. 236, 590-600], suggesting that the C-domain plays a genuine biological role in saccharide binding. In the acarbose-maltose complex, the tetrasaccharide inhibitor acarbose is found as an extended hexasaccharide species, bound in the -3 to +3 subsites. The transition state mimicking pseudosaccharide is bound in the -1 subsite of the enzyme in a 2H3 half-chair conformation, as expected. The active site of Novamyl lies in an open gully, fully consistent with its ability to perform internal cleavage via an endo as opposed to an exo activity.

Performance of the SE-9000 automated haematology analyser in a laboratory serving a haematological oncology unit.

The performance of the SE-9000 automated haematology analyser in a laboratory receiving a high number of abnormal specimens from haematological oncology patients was assessed according to formal protocols for the evaluation of blood cell counters. Linearity over a useful working range, precision in clinically important ranges and negligible carry-over were demonstrated in this group of patient samples confirming the results of previous investigators. The comparability of instrument derived differential leucocyte counts from both normal and distributionally abnormal samples with those obtained by visual microscopy using the NCCLS H-20 A protocol was very good. The sensitivity of flags for the detection of immature granulocytes and myeloid blast cells was high and this can be attributed to the incorporation of a new measuring channel (Immature Myeloid Information or IMI channel). The number of unrecognized abnormalities was low and when compared with the poor sensitivity of the routine 100-cell visual differential leucocyte count, the analyser was judged suitable for monitoring patients with haematological malignancies. The performance of flags such as 'left shift' and 'atypical lymphocytes' can be improved by taking into consideration distributional abnormalities such as neutrophilia and lymphocytosis. The trigger level for these flags should be adapted to the clinical need particularly in cases of neutropenia following chemotherapy, and in lymphoproliferative disorders and infection.

[A staged plan for laboratory diagnosis of hereditary metabolic diseases]. / Stufenplan zur Labordiagnostik hereditärer Stoffwechselerkrankungen.

When clinical evidence provides grounds for suspecting inborn errors of metabolism it is urgent to perform the necessary, relevant, specific laboratory investigations in good time and with a view to quality. Normally, the realization depends on individual initiatives and the use of laboratories mainly designed for pediatrics and human genetics. Consequently the results are equally a matter of chance. Nothing in this situation can be changed in principle by using the catalogue of services of the Society for Human Genetics of the GDR. Central administrative provisions are necessary to improve the present unsatisfactory situation. Proposals for regulations, division of responsibility and a graduated programme of parameters are discussed here with a view to establishing uniform procedures.