The C-terminal domain of the Bloom syndrome DNA helicase is essential for genomic stability.

BACKGROUND: Bloom syndrome is a rare cancer-prone disorder in which the cells of affected persons have a high frequency of somatic mutation and genomic instability. Bloom syndrome cells have a distinctive high frequency of sister chromatid exchange and quadriradial formation. BLM, the protein altered in BS, is a member of the RecQ DNA helicase family, whose members share an average of 40% identity in the helicase domain and have divergent N-terminal and C-terminal flanking regions of variable lengths. The BLM DNA helicase has been shown to localize to the ND10 (nuclear domain 10) or PML (promyelocytic leukemia) nuclear bodies, where it associates with TOPIIIalpha, and to the nucleolus. RESULTS: This report demonstrates that the N-terminal domain of BLM is responsible for localization of the protein to the nuclear bodies, while the C-terminal domain directs the protein to the nucleolus. Deletions of the N-terminal domain of BLM have little effect on sister chromatid exchange frequency and chromosome stability as compared to helicase and C-terminal mutations which can increase SCE frequency and chromosome abnormalities. CONCLUSION: The helicase activity and the C-terminal domain of BLM are critical for maintaining genomic stability as measured by the sister chromatid exchange assay. The localization of BLM into the nucleolus by the C-terminal domain appears to be more important to genomic stability than localization in the nuclear bodies.

Comparative DNA sequence analysis of mouse and human protocadherin gene clusters.

The genomic organization of the human protocadherin alpha, beta, and gamma gene clusters (designated Pcdh alpha [gene symbol PCDHA], Pcdh beta [PCDHB], and Pcdh gamma [PCDHG]) is remarkably similar to that of immunoglobulin and T-cell receptor genes. The extracellular and transmembrane domains of each protocadherin protein are encoded by an unusually large "variable" region exon, while the intracellular domains are encoded by three small "constant" region exons located downstream from a tandem array of variable region exons. Here we report the results of a comparative DNA sequence analysis of the orthologous human (750 kb) and mouse (900 kb) protocadherin gene clusters. The organization of Pcdh alpha and Pcdh gamma gene clusters in the two species is virtually identical, whereas the mouse Pcdh beta gene cluster is larger and contains more genes than the human Pcdh beta gene cluster. We identified conserved DNA sequences upstream of the variable region exons, and found that these sequences are more conserved between orthologs than between paralogs. Within this region, there is a highly conserved DNA sequence motif located at about the same position upstream of the translation start codon of each variable region exon. In addition, the variable region of each gene cluster contains a rich array of CpG islands, whose location corresponds to the position of each variable region exon. These observations are consistent with the proposal that the expression of each variable region exon is regulated by a distinct promoter, which is highly conserved between orthologous variable region exons in mouse and human.

The appropriateness of oral fluoroquinolone-prescribing in the long-term care setting.

OBJECTIVE: To evaluate the appropriateness of ciprofloxacin-prescribing in the long-term care setting. DESIGN: Retrospective chart review. SETTING: A large academically oriented long-term care facility. PATIENTS: Institutionalized elderly patients with a mean age of 88 years. METHODS: One hundred orders were randomly selected for review from all ciprofloxacin orders initiated over a 3-year period. Criteria for appropriateness of ciprofloxacin-prescribing were developed based on a comprehensive review of the medical literature. Evaluation of appropriateness of prescribing was based on the indication for therapy and the availability of more effective and/or less expensive alternative antibiotic regimens. Only information available to the physician at the time of the order was used to judge appropriateness. Abstracted medical records were evaluated independently by a geriatrician and an infectious diseases specialist. RESULTS: With respect to site of infection, the urinary tract accounted for 43% of all ciprofloxacin orders; the lower respiratory tract, 28%; and skin and soft-tissue infections, 17%. Only 25% of orders were judged appropriate. Twenty-three percent of orders were judged less than appropriate based on indication, and 49% due to the availability of a more effective and/or less expensive alternative antibiotic choice. There was insufficient information in the medical record to judge 3% of the orders. CONCLUSION: These results indicate less than optimal prescribing of oral fluoroquinolones in the long-term care setting, with potential consequences including the development of resistant bacterial strains and increased health care costs.

Reducing the use of H2-receptor antagonists in the long-term-care setting.

OBJECTIVES: To examine the patterns of H2 blocker use in the long-term-care setting and to assess the effect of educational interventions designed to improve H2 blocker utilization patterns. DESIGN: Time-series quasi-experimental study and retrospective chart review. SETTING: A large academically-oriented long-term-care facility. PATIENTS: Institutionalized elderly patients with a mean age of 88 years receiving H2 blocker therapy. INTERVENTIONS: Two interventions involving group discussions with the medical staff, supporting educational materials, and physician-specific listings of patients receiving H2 blockers were employed sequentially over a 32-month period. RESULTS: Each intervention resulted in substantial reductions in medication use (59.6% and 32.1%, respectively). Indications for H2 blocker use were determined retrospectively for patients identified as receiving therapy prior to the interventions (n = 110). Forty-one percent were found to be receiving therapy for reasons unsubstantiated by the medical literature. These patients were more likely to be discontinued from therapy than those receiving therapy for substantiated indications (P less than 0.01), consistent with the primary focus of the educational interventions. CONCLUSIONS: These results suggest that the excessive use of H2 blocker therapy in the long-term care setting responds to educational interventions with therapeutically appropriate reductions in utilization. Repeated interventions are necessary to maintain such reductions over time although there may be some reduction in the effectiveness of the intervention with repetition.

Barium enemas in the frail elderly.

PURPOSE: The objective of this investigation was to determine the frequency of and predictors for inadequate barium enemas in the frail elderly. PATIENTS AND METHODS: The medical and radiologic records of 171 elderly institutionalized patients (mean age = 85.3 years), who underwent barium enema examinations, were retrospectively reviewed. The study outcome of primary interest was the radiologist's report of the adequacy of examination as indicated in the written summary of the results of the barium enema procedure. RESULTS: Eighty-eight (51.5%) of the 171 studies were deemed inadequate, with poor bowel preparation a primary or contributing factor in 89.7% of the inadequate studies. Among a variety of demographic and clinical factors, only long-term laxative and/or cathartic use was associated with an inadequate study (odds ratio = 7.0; 95% confidence interval 2.7 to 18.0). CONCLUSION: These results demonstrate a very high frequency of inadequate barium enema examinations in the very old and suggest a need for improved methods of bowel preparation in this patient population, especially in those who are long-term users of laxatives and cathartics.

Adaptive detection and removal of non-gaussian spikes from gaussian data.

A nonlinear adaptive method is presented for filtering a signal which is corrupted by spikes which take discrete values Mi with probability Pi at random points in time. An unsupervised learning technique is used to estimate the unknown parameters Mi, Pi, and oi. The spikes are then removed using a Bayes classifier. A theoretical and experimental comparison with the MMSE linear filter is presented.

Amantadine in drug-induced extrapyramidal signs: a comparative study.

In our non-blind comparative study, amantadine was as effective as the standard medications, benztropine and ethopropazine, in controlling drug-induced extrapyramidal signs. However, statistically significant improvement was noted a week after all the three medications. In addition, extrapyramidal signs were not completely controlled in most patients even after weeks, even though substantial improvement was noted. This indicates the limitations of the currently available antiparkinsonian medications. Amantadine produced least side effects. Therefore, it may be particulary useful in patients who may not tolerate antiparkinsonian medication with anticholinergic properties. Our clinical finding that two patients with depression improved was rather interesting and needs further exploration. In summary, anamtadine is a valuable addition to our armamentarium of antiparkinsonian drugs. The drug compared favourably with other standard medications. The problem of dissipation of the therapeutic effects over time was not studied in our trial.