Distribution of mutations in the PEX gene in families with X-linked hypophosphataemic rickets (HYP)

Mutations in the PEX gene at Xp22.1 (phosphate-regulating gene with homologies to endopeptidases, on the X-chromosome), are responsible for X-linked hypophosphataemic rickets (HYP). Homology of PEX to the M13 family of Zn2+ metallopeptidases which include neprilysin (NEP) as prototype, has raised important questions regarding PEX function at the molecular level. The aim of this study was to analyse 99 HYP families for PEX gene mutations, and to correlate predicted changes in the protein structure with Zn2+ metallopeptidase gene function. Primers flanking 22 characterised exons were used to amplify DNA by PCR, and SSCP was then used to screen for mutations. Deletions, insertions, nonsense mutations, stop codons and splice mutations occurred in 83% of families screened for in all 22 exons, and 51% of a separate set of families screened in 17 PEX gene exons. Missense mutations in four regions of the gene were informative regarding function, with one mutation in the Zn2+-binding site predicted to alter substrate enzyme interaction and catalysis. Computer analysis of the remaining mutations predicted changes in secondary structure, N-glycosylation, protein phosphorylation and catalytic site molecular structure. The wide range of mutations that align with regions required for protease activity in NEP suggests that PEX also functions as a protease, and may act by processing factor(s) involved in bone mineral metabolism.      

Doctors'' characteristics do not predict long-term glycaemic control in type 2 diabetic patients.

Glycaemic control in type 2 diabetic patients varies widely between general practitioners (GPs). To increase our understanding of this variation, linear random effects models were used to examine the predictive value of GP characteristics on the course of annual HbA1c measurements, in 688 newly diagnosed type 2 diabetic patients between one and five years after diabetes diagnosis. We found that characteristics of centrally supported GPs, such as interest in diabetes, experience, practice type, list size, and weekly working hours, did not predict their patients' glycaemic control.     

Coxsackievirus-mediated hyperglycemia is enhanced by reinfection and this occurs independent of T cells

The induction of autoimmunity by viruses has been hypothesized to occur by a number of mechanisms. Coxsackievirus B4 (CB4) induces hyperglycemia in SJL mice resembling diabetes in humans. While virus is effectively cleared within 2 weeks, hyperglycemia does not appear until about 8-12 weeks postinfection at a time when replicative virus is no longer detectable. In SJL mice, reinfection with CB4 enhanced the development of hyperglycemia. As predicted, the immune system responded more rapidly to the second infection and virus was cleared more swiftly. However, while infiltrating T cells were found within the pancreas, depletion of the CD4 T cell population prior to secondary infection or use of CD8 knock-out mice had no effect on the development of virus-mediated hyperglycemia. In conclusion, enhanced hyperglycemia induced by CB4 occurs independent of the T cell response.     

Telomerase activity and proliferation index in aggressive mature B-cell lymphoma: comparison to germinal center phenotypic markers

Cell proliferation may be evaluated by various methods, including Ki-67 immunohistochemistry and measures of telomerase activity. Both methods would theoretically show comparable increases in a given case. To evaluate the relationship between these 2 markers of proliferation in aggressive mature B-cell lymphomas, 48 cases were studied. The study group included 5 cases of mantle cell lymphoma (MCL); 6 cases of Burkitt's/Burkitt's-like lymphoma (BL); 9 cases of follicular lymphoma, grade 3 (FLC); and 28 cases of diffuse large B-cell lymphoma (DLC). Telomerase activity was measured as total product generated (TPG) units, and TPG results for the aforementioned cases were compared to the TPG results for 10 cases of reactive follicular hyperplasia. An overlap in TPG scores between reactive cases and lymphoma cases was found. Significant differences in both log TPG (P = 0.0443) and Ki-67 (P = 0.0006) were seen in the different lymphoma types. A positive correlation between Ki-67 percentage and TPG score was identified in FLC (r = 0.9281; P = 0.0003), but a poor correlation between these 2 indicators was seen in the other lymphoma types. Cluster analysis identified distinct patterns for MCL, FLC, and BL, but heterogeneous patterns for DLC. Because increases in both Ki-67 proliferation and telomerase activity are reported in normal germinal centers (GCs), these tests were also evaluated for usefulness as markers of a GC cell phenotype. Among the FLC and DLC cases, features of a GC phenotype significantly correlated with increased Ki-67 percentage (P = 0.0152), but not with increased log TPG. An elevated log TPG correlated with CD10 expression, and elevated Ki-67 percentage correlated with both CD10 and BCL-6 expression. TPG level and Ki-67 percentage did not correlate with the presence of t(14;18) or BCL-2 protein expression. Although the proliferation patterns were fairly distinctive for MCL, FLC, and BL, these studies show that markers of cell proliferation do not by themselves,identify distinct subtypes of large cell lymphomas. With the exception of FLC, the tumors exhibited poor correlation between telomerase activity and Ki-67 proliferation index. These tests did show some correlation with expression of GC cell phenotypic markers, however.     

Alternative splicing of exon 14 determines nuclear or cytoplasmic localisation of fmr1 protein isoforms

Impaired expression of the FMR1 gene is responsible for the fragile X mental retardation syndrome. The FMR1 gene encodes a cytoplasmic protein with RNA-binding properties. Its complex alternative splicing leads to several isoforms, whose abundance and specific functions in the cell are not known. We have cloned in expression vectors, cDNAs corresponding to several isoforms. Western blot comparison of the pattern of endogenous FMR1 proteins with these transfected isoforms allowed the tentative identification of the major endogenous isoform as ISO 7 and of a minor band as an isoform lacking exon 14 sequences (ISO 6 or ISO 12), while some other isoforms (ISO 4, ISO 5) were not expressed at detectable levels. Surprisingly, in immunofluorescence studies, the transfected splice variants that exclude exon 14 sequences (and have alternate C-terminal regions) were shown to be nuclear. Such differential localisation was however not seen in subcellular fractionation studies. Analysis of various deletion mutants suggests the presence of a cytoplasmic retention domain encoded in exon 14 and of a nuclear association domain encoded within the first eight exons that appear however to lack a typical nuclear localisation signal.      

Colonic histopathology in untreated celiac sprue or refractory sprue: Is it lymphocytic colitis or colonic lymphocytosis?

Colonic histopathology in some patients with untreated celiac sprue and refractory sprue has been said to be indistinguishable from lymphocytic colitis, but there have been no objective comparisons on which this is based. The purpose of this study was to determine the prevalence and to characterize the nature of colonic histopathology at the time of diagnosis in patients with celiac or refractory sprue. Colonoscopic biopsy specimens obtained at the time of diagnosis from 16 patients with celiac sprue, six patients with refractory sprue, nine patients with lymphocytic colitis, and five normal controls were analyzed blindly by histological and morphometric methods, quantitating the number and specific subtypes of inflammatory cells within the lamina propria and epithelium. Immunoperoxidase staining of intraepithelial lymphocytes with a monoclonal antibody to CD8 also was performed. Three of 16 patients with untreated celiac sprue (19%) were thought to have colonic histological abnormalities, which by morphometry consisted of slightly increased numbers of lymphocytes in the surface epithelium and lamina propria, many of which were CD8-positive. These abnormalities were distinguishable from lymphocytic colitis by the lack of increased overall lamina propria cellularity and surface epithelial abnormalities, and by fewer intraepithelial lymphocytes. In refractory sprue, colonic histological abnormalities were more frequent than in celiac sprue, occurring in four of six patients (67%), more pronounced, and identical to those in the lymphocytic colitis syndrome. However, colonic intraepithelial lymphocytes in lymphocytic colitis were mostly CD8-positive, whereas those in the colitis of refractory sprue rarely were. Mild colonic lymphocytosis in patients with untreated celiac sprue should be distinguished from lymphocytic colitis by the lack of surface epithelial abnormalities, the lack of increased cellularity of the lamina propria, and the lack of ongoing watery diarrhea after treatment with a gluten-free diet. In contrast, colonic histopathology in refractory sprue is indistinguishable from lymphocytic colitis, although immunohistochemical differences do exist.     

Eccentric visual acuity in patients with macular disease

A series of cards each containing a two dimensional array of identical Snellen "E's" was used to determine best eccentric visual acuity in patients with macular disease having Snellen visual acuity of 20/70 or worse. Each "full field E" card simultaneously presents the same letter to foveal and parafoveal areas. This test can therefore determine quickly if potentially useful vision is present in any area of the central visual field. In our study of 37 eyes, 70% demonstrated potential visual acuity at least two times better than visual acuity measured by conventional methods, and 20% demonstrated at least a fourfold improvement. This suggests that most patients with macular disease do not spontaneously employ their best remaining area of retina for fixation.     

Phase I and pharmacokinetic study of tiazofurin (TCAR,NSC 286193) administered by continuous infusion

Summary Tiazofurin (2--D-ribofuranosylthiazole-4-carboxamide, TCAR) is a synthetic C-nucleoside that demonstrated significant in vivo activity against a variety of animal tumors as well as in vitro activity against human tumor-derived cell lines. Thirteen patients were treated with TCAR administered as a 5-day continuous infusion in this Phase I trial. Seventeen complete cycles were administered in three dose levels ranging from 550 to 1450 mg/M². Dose-limiting toxicities were myelosuppression and neurotoxicity including severe lethargy. Other toxicities including superficial skin peeling, myalgias, and tearing were seen at all doses. One patient had chest pain on day 4 resulting in stopping the drug, however, there was no evidence of cardiac or pericardial disease. Uric acid levels rose within one day in the absence of allopurinol treatment. There were no treatment related deaths. HPLC measurement of drug levels demonstrated steady-state plasma levels during the infusion, and a half-life following the infusion of 7.7 ± 0.6 hours. Minor abnormalities in renal function were associated with dramatic changes in pharmacokinetics and toxicity. No clinical responses were observed in this trial.Abbreviations TCAR Tiazofurin - HPLC High performance liquid chromatography - IMPD Inosine monophosphate dehydrogenase - WBC white blood cell - CPK creatine phosphokinase - C_ss steady-state concentration     

"High-dose" calcitriol for control of renal osteodystrophy in children on CAPD

High doses of calcitriol were used prospectively for 11 to 29 months to raise serum calcium levels in an effort to control renal osteodystrophy in 16 children undergoing CAPD. Serum Ca, P, iPTH and alkaline phosphatase were measured monthly; hand radiographs were obtained every six months, and a semiquantitative score of bone abnormalities was evaluated by two independent observers. During the study, serum Ca increased from 9.9 +/- 0.9 to 11.0 +/- 0.6 mg/dl (P less than 0.001); serum iPTH decreased by 113 +/- 131 microliter Eq/ml (P less than 0.005); serum P was unchanged; and serum alkaline phosphatase fell by 33 +/- 46% (P less than 0.02), 530 +/- 397 to 204 +/- 551 IU/liter. The radiographic score fell from 4.8 +/- 4.6 to 0.9 +/- 1.2 (P less than 0.005). The average and maximal doses of calcitriol were 0.61 +/- 0.37 and 0.95 +/- 0.56 microgram/day or 28 +/- 18 and 46 +/- 28 ng/kg body wt/day, respectively. Transient and asymptomatic hypercalcemia occurred in nine patients and two patients had reversible conjunctivitis in association with the hypercalcemia. Thus, "high dose" calcitriol prevented or controlled progression of hyperparathyroid bone disease in most pediatric CAPD patients. The failure to suppress PTH or reverse secondary hyperparathyroidism until the serum Ca rose to 10.5 to 11.0 mg/dl could reflect an increase in the "set point" for PTH suppression by serum calcium in many uremic children.     

Parathyroid imaging: Its current status and future role

The management of autonomous (primary or tertiary) hyperparathyroidism is controversial for two important reasons: (1) Diagnosis of primary or tertiary hyperparathyroidism (as distinct from reactive or secondary hyperparathyroidism) has been revolutionized in the past 20 years as a result of routine inclusion of serum calcium concentration assays in serum multiautomated analysis, now obtained routinely for both hospitalized as well as ambulatory patients. The prevalence of primary hyperparathyroidism in the general population has appeared to rise as a consequence of this assay and the enhanced detection of this disease. This situation has confused the management of hyperparathyroidism since most patients now present with asymptomatic disease, and the need for surgical treatment is controversial in asymptomatic individuals. (2) Primary hyperparathyroidism usually is caused by hypersecretion of parathyroid hormone by an autonomously functioning parathyroid adenoma. In a small percentage of cases, multigland hyperplasia is present. In experienced hands, surgical removal of an adenoma within the thyroid bed cures the hyperparathyroidism 90% to 95% of the time, without performance of a preoperative procedure to localize the adenoma. Approximately 10% of parathyroid tissue is ectopic in location, however. Furthermore, approximately two thirds of "missed" adenomas are within the thyroid bed. Reexploration in the event of a failed operation therefore is not an uncommon occurrence. Parathyroid localization procedures clearly are indicated in patients with primary hyperparathyroidism who have evidence of persistent disease after a failed attempt at surgical cure. In patients first presenting with primary hyperparathyroidism, the need for a localization procedure is less clear, since surgery appears to be successful much of the time without it. Regardless of the nature of the above controversies, surgery for autonomous hyperparathyroidism continues, and localization procedures become more popular. Preoperative localization procedures such as angiography and venography with venous sampling for parathormone are cumbersome and invasive. Noninvasive tests to localize the parathyroid glands have emerged in the past 10 years, including dual tracer radionuclide scintigraphy with 201-thallous chloride and 99m-technetium pertechnetate, high-resolution computer tomography, and fine parts ultrasonography. Dual tracer scintigraphy with thallium and technetium is reported to have a localization sensitivity of 70%-90%. False-negative studies occur primarily in patients with small adenomatous or hyperplastic glands.(ABSTRACT TRUNCATED AT 400 WORDS)