The abundance of additional N-acetyllactosamine units in N-linked tetraantennary oligosaccharides of human Tamm-Horsfall glycoprotein is a donor-specific feature

Previously, treatment of Tamm-Horsfall glycoprotein (THp) from different donors with endo-beta-galactosidase has been shown to liberate a tetra- and a Sd(a)-active pentasaccharide, concluding the presence of N-linked carbohydrate chains containing additional N - acetyllactosamine units. These type of oligosaccharides were not found in a detailed structure elucidation of the carbohydrate moiety of THp of one male donor, suggesting a donor-specific feature for these type of structures. Therefore, THp was isolated from four healthy male donors and each subjected to endo-beta-galactosidase treatment in order to release these tetra- and Sd(a)-active pentasaccharide. Differences were observed in the total amount of released tetra- and Sda-active pentasaccharide of the used donors (42, 470, 478, 718 microg/100 mg THp), indicating that the presence of repeating N-acetyllactosamine units incorporated into the N-glycan moiety of THp is donor specific. Furthermore, a higher expression of the Sd(a) determinant on antennae which display N-acetyllactosamine elongation was observed, suggesting a better accessibility for the beta-N-acetylgalactosaminyltransferase. In order to characterize the N-glycans containing repeating N- acetyllactosamine units, carbohydrate chains were enzymatically released from THp and isolated. The tetraantennary fraction, which accounts for more than 33% of the total carbohydrate moiety of THp, was used to isolate oligosaccharides containing additional N - acetyllactosamine units. Five N-linked tetraantennary oligosaccharides containing a repeating N-acetyllactosamine unit were identified, varying from structures bearing four Sd(a) determinants to structures containing no Sd(a) determinant (see below). One compound was used in order to specify the branch location of the additional N- acetyllactosamine unit, and it appeared that only the Gal-6' and Gal-8' residues were occupied by a repeating N -acetyllactosamine unit.      

Insulin dependent diabetes in children under 5: incidence and ascertainment validation for 1992.

OBJECTIVE--To establish the incidence of insulin dependent diabetes diagnosed in children under 5 years of age in the British Isles during 1992, comparing the national and regional results with those of our 1988 national study, and estimating the 1992 study''s level of case ascertainment. DESIGN--Active monthly reporting of cases by consultant paediatricians through the framework of the British Paediatric Surveillance Unit, with additional reports from specialist diabetes nurses and regional health authorities. SUBJECTS--All children diagnosed under the age of 5 years with primary insulin dependent diabetes from 1 January to 31 December 1992 (inclusive) and resident in the British Isles at diagnosis. RESULTS--387 children (208 boys and 179 girls) were confirmed to have insulin dependent diabetes, giving a national incidence of 9.3/100,000/year. This is similar to the 9.9/100,000/year found in 1988. Three sample capture-recapture analysis, which could only be applied across the 12 (out of 18) regions supplying regional information to the study, suggested ascertainment rates of 78% for the British Paediatric Surveillance Unit, 67% for specialist nurses, 69% for regional health authorities, and 99% for the aggregated registry. CONCLUSIONS--The national incidence of diabetes in the under 5s in the British Isles did not differ between 1988 and 1992. Nearly complete (99%) ascertainment of cases was possible only for regions for which three data sources were available. Capture-recapture analysis highlighted both the need for more than one data source and for each data source to be complete for the whole study area.     

The sensitivity of rapid (partial) review of cervical smears

SHIELD P. W. AND COX N. C. (1998) Cytopathology 9, 84–92 The sensitivity of rapid (partial) review of cervical smears Rapid review involves a daily rapid (e.g. 30 s) review of all smears not normally double-screened. It has been suggested that the method may increase the sensitivity of cervical cytology by identifying abnormalities not reported on initial screening, true false negatives (TFN). Rapid screening is reported to have high sensitivity for cervical neoplasia when used as a preview tool. To be effective, however, in a review mode it must be able to detect TFN. Several studies have found that many TFN result from factors such as low numbers of abnormal cells or subtle expression of diagnostic criteria. Studies on the sensitivity of rapid screening for detecting TFN would therefore provide a more reliable estimate of its value as a review tool. The sensitivity of rapid re-screening was evaluated using a test set of 200 cases. Each of 15 screeners rapidly reviewed (30 s partial screen) the set over a 2-week period. The set consisted of 129 normal, 28 low-grade squamous lesions (CIN I), 37 high-grade lesions (CIN II, III and adenocarcinoma in situ (AIS)) and six invasive carcinomas. The abnormals included 20 TFN cases. The median sensitivity for abnormalities was 62%. Rapid review was more sensitive for CIN II and CIN III (67%) and invasive carcinoma (66.7%) than for CIN I (53%). Great variation was apparent in the sensitivity for individual screeners, with a range of 41–86% for all abnormalities. The sensitivity for TFN cases varied even more (10–75%, median 35%) and for most screeners was significantly (P < 0.05) lower than for cases which were detected on initial screen (53–90%, median 70.6%). Following this trial rapid review was used routinely for a period of 3 months. In this time 11 413 cases were rapidly reviewed. This led to the full review of 415 slides (3.5%) and the identification of 16 cases of undetected CIN (12 CIN I, three CIN II, one CIN III). Based on current estimates of our laboratory false-negative rate this represents between a quarter and half of the TFN cases of CIN that probably occurred in this period. In conclusion, rapid screening is likely to be significantly less sensitive when used in a review rather than a preview mode. In routine practice the method requires a daily commitment of screener time, but does provide a higher yield of TFN smears than does random review, and allows amendment of these results prior to reporting.     

A maternal hypomethylation syndrome presenting as transient neonatal diabetes mellitus

The expression of imprinted genes is mediated by allele-specific epigenetic modification of genomic DNA and chromatin, including parent of origin-specific DNA methylation. Dysregulation of these genes causes a range of disorders affecting pre- and post-natal growth and neurological function. We investigated a cohort of 12 patients with transient neonatal diabetes whose disease was caused by loss of maternal methylation at the TNDM locus. We found that six of these patients showed a spectrum of methylation loss, mosaic with respect to the extent of the methylation loss, the tissues affected and the genetic loci involved. Five maternally methylated loci were affected, while one maternally methylated and two paternally methylated loci were spared. These patients had higher birth weight and were more phenotypically diverse than other TNDM patients with different aetiologies, presumably reflecting the influence of dysregulation of multiple imprinted genes. We propose the existence of a maternal hypomethylation syndrome, and therefore suggest that any patient with methylation loss at one maternally-methylated locus may also manifest methylation loss at other loci, potentially complicating or even confounding the clinical presentation.Electronic Supplementary Material Supplementary material is available to authorised users in the online version of this article at .