Thermal modelling of Ohmic heating microreactors

This paper describes the static and transient thermal modelling of an Ohmic heating microreactor for biological sample processing for the purpose of genetic analysis. Precise thermal management can be used for the effective preparation of analyte DNA molecules prior to detection. Due to the small dimensions of the microreactor, the direct measurement and monitoring of the temperature distribution presents a challenge. To overcome this, thermal modelling has been used to accurately predict the thermal behaviour of the microreactor and sample component. It is further possible to calculate the required input power levels and provide design criteria to optimise the design of the microreactor.     

Prognostic significance of fluorescence intensity of surface marker expression in childhood B-precursor acute lymphoblastic leukemia. A Pediatric Oncology Group Study

This report describes the prognostic significance of the intensity of surface membrane antigen expression in a series of 1,231 children older than 1 year with newly diagnosed B-precursor acute lymphoblastic leukemia (ALL) treated on Pediatric Oncology Group (POG) treatment protocols. All patients had dual-color flow cytometric immunophenotyping performed at a central reference laboratory with a standard panel of monoclonal antibodies. The flow cytometers used in the study were calibrated with a standard fluorescence microparticle that permitted conversion of relative fluorescence channels to standard units of mean equivalents of soluble fluorochrome (MESF). In univariate analysis, fluorescence intensity of CD45 and CD20 was significantly associated with event-free survival (EFS), whereas other markers showed no significant correlation with outcome. Patients whose blasts were greater than the 75th percentile of intensity for CD45 (corresponding to 18,000 MESF units with CD45-FITC, or about 8% of the intensity of normal lymphocytes) fared significantly worse than those with lower-density CD45, and those whose blasts were greater than the 25th percentile of intensity for CD20 (corresponding to 17,900 MESF units with CD20-PE) had a poorer EFS. The intensity of both CD45 and CD20 was independently correlated with outcome. There was no significant correlation between intensity of expression of either antigen and traditional clinical risk factors, ploidy, or t(9;22) or t(1;19). All patients with t(4;11) had CD45 intensity greater than the 75th percentile, but CD45 intensity retained its prognostic significance after adjusting for t(4;11). In multivariate analysis, both CD45 intensity greater than the 75th percentile and CD20 intensity greater than the 25th percentile were significantly correlated with poor outcome independently of previously reported poor prognostic factors including National Cancer Institute (NCI) risk group, ploidy, trisomies of 4 and 10, and adverse translocations including t(1;19), t(9;22), and t(4;11). We conclude that in childhood B-precursor ALL, the intensity of expression of CD20 and CD45 provides prognostic information not available from simple consideration of antigen expression as positive or negative, and adds to that obtained from traditional clinical and biologic risk factors.     

Selective block in erythropoietin-induced differentiation of growth factor-independent retrovirally-infected TF-1 cells

The erythroleukaemic cell line TF-1, infected with either the pBabe neo retrovirus or the retrovirus bearing the human erythropoietin (hEpo) gene, developed three growth factor-independent clones. Erythropoietin (Epo), interleukin-3 (IL-3) and granulocyte-macrophage colony stimulating factor (GM-CSF) accelerated the proliferation of these clones. Autonomous growth of the clones was independent of Epo because it was not altered by Epo anti-sense oligonucleotides, nor was Epo detectable in culture supernatants. Cells from the mutant clones could not be induced by Epo to express glycophorin A and haemoglobin synthesis was markedly reduced. Haemin reversed the block in Epo-induced haemoglobin synthesis. Acquisition of growth factor-independence appears to be linked with the selective loss of differentiation capacity. These cells may provide a useful model for the study of the mechanisms involved in leukaemic transformation.     

Clostridium difficile-associated diarrhea: epidemiology, risk factors, and infection control

OBJECTIVES: To evaluate the effectiveness of specific infection control measures on the incidence of Clostridium difficile-associated diarrhea (CDAD) and to identify risk factors for its development. SETTING: 370-bed, tertiary-care teaching hospital with approximately 12,000 to 15,000 admissions per year. METHODS: Several infection control measures were implemented in 1991 and 1992, and the attack rates of CDAD were calculated quarterly. Antibiotic use for 1988 through 1993 was analyzed. A case-control study was conducted from January 1992 to December 1992 to identify risk factors for acquisition of CDAD. RESULTS: From 1989 to 1992, the attack rate of CDAD increased from 0.49% to 2.25%. An increase in antibiotic use preceded the rise in the incidence of CDAD in 1991. Despite implementation of various infection control measures, the attack rate decreased to 1.32% in 1993, but did not return to baseline. Ninety-two cases and 78 controls (patients with diarrhea but with negative toxin assay) were studied. By univariate analysis, history of prior respiratory tract infections (odds ratio [OR], 3.6; 95% confidence interval [CI95], 1.2-10.4), the number of antibiotics, and the duration of exposure to second-generation cephalosporins (OR, 3.55; CI95, 1.47-9.41) and to ciprofloxacin (OR, 7.27; CI95, 1.13-166.0) were related significantly to the development of CDAD. By stepwise logistic regression analysis, only exposure to antibiotics and prior respiratory tract infections (P = .0001 and .0203, respectively) were found to be significant. CONCLUSION: Antibiotic pressure might have contributed to failure of infection control measures to reduce the incidence of CDAD to baseline.     

Prognostic significance of tumor markers in colorectal cancer patients: DNA index, S-phase fraction, p53 expression, and Ki-67 index

Risk of colorectal cancer recurrence has traditionally been determined by use of pathologic staging. However, it is apparent that subgroups of patients exist within tumor stages whose clinical behavior differs. This study was undertaken to identify tumor-associated factors that might be predictive of outcome in patients with intermediate stages who will benefit the most from postsurgical adjuvant therapy. Seventy patients with stage II and III colorectal cancer were assessed for DNA index, S-phase fraction, p53 expression, and Ki-67 index. Tumor recurrence was analyzed by means of nonparametric tests and Cox proportional hazard models incorporating standard clinical and pathologic criteria. Of the four prognostic markers evaluated, Ki-67 index was significantly associated with disease recurrence (P = 0.02), whereas DNA index, S-phase fraction, and p53 expression were not. After stratification by tumor stage, significant associations between Ki-67 index and disease recurrence were retained in stage II tumors (P = 0.01) but not in stage III tumors (P = 0.23). Cox proportional hazard regression analysis indicated that among stage II patients, those with a Ki-67 index >45% were associated with 6.5 times greater risk for disease recurrence than those with a Ki-67 index >/=45%. It was concluded that an elevated Ki- 67 index is associated with an increased risk of tumor recurrence in stage II colorectal cancer.     

Thioredoxin domain non-equivalence and anti-chaperone activity of protein disulfide isomerase mutants in vivo

Coexpression of the enzyme, protein disulfide isomerase (PDI), has been shown to increase soluble and secreted IgG levels from baculovirus-infected insect cells (Hsu, T.-A., Watson, S., Eiden, J. J., and Betenbaugh, M. J. (1996) Protein Expression Purif. 7, 281-288). PDI is known to include catalytic active sites in two separate thioredoxin-like domains, one near the amino terminus and another near the carboxyl terminus. To examine the role of these catalytic active sites in enhancing immunoglobulin solubility, baculovirus constructs were utilized with cysteine to serine mutations at the first cysteine of one or both of the CGHC active site sequences. Trichoplusia ni insect cells were coinfected with a baculovirus vector coding for IgG in concert with either the wild-type human PDI virus, amino-terminal mutant (PDI-N), carboxyl-terminal mutant (PDI-C), or mutant with both active sites altered (PDI-NC). Western blot analysis revealed that both immunoglobulins and PDI protein were expressed in the coinfected cells. To evaluate the effect of the PDI variants on immunoglobulin solubility and secretion, the infected cells were labeled with 35S-amino-acids for different periods, and the soluble immunoglobulins were immunoprecipitated from clarified cell lysates and culture medium using anti-IgG antibodies. Only coinfections with the wild-type PDI and PDI-N mutant led to increased immunoglobulin solubility and higher IgG secretion. In contrast, infection with the PDI-C and PDI-NC variants actually lowered immunoglobulin solubility levels below those achieved with a negative control virus. Immunoprecipitation with anti-PDI antibody revealed that heterologous PDI-C and PDI-NC were insoluble, even though PDI-N and wild-type PDI protein were detected in soluble form. The capacity for PDI-N to increase immunoglobulin solubility whereas the PDI-C mutant lowered solubility indicates that the amino- and carboxyl-terminal thioredoxin domains of PDI are functionally distinct in vivo following mutations to the active site. Furthermore, mutations at the active site of the carboxyl-terminal thioredoxin domain result in PDI variants that can act as anti-chaperones of immunoglobulin solubility in vivo as has been observed in vitro for lysozyme aggregation by wild-type PDI and PDI mutants (Puig, A., and Gilbert, H. F. (1994) J. Biol. Chem. 269, 7764-7771).     

A 21st century computerized injection system for local pain control

This article describes a new computerized local anesthetic injection system for pain control. The core technology of this system is the microprocessor-controlled delivery of anesthetic solution at a constant pressure and controlled volume, regardless of encountered variations in tissue resistance. This fine-tuned, high suffusion flow rate of anesthetic provides a rapid onset of anesthesia for most patients. Traditional block injections and infiltrations as well as palatal injections and periodontal ligament injections are administered with precision, ease, and patient comfort.     

Hierarchical polytomous regression models with applications to health services research

The analysis of variations is an important area of interest in health services and outcomes research and has two main goals: to identify and quantify variability across units, such as geographic regions or health care providers, in terms of procedure utilization and outcomes, and to explore the links between process, such as regional or hospital practice patterns, and outcomes, such as patient mortality and functional status. Hierarchical regression models are well suited for this type of analysis. In this paper we formulate a hierarchical polytomous regression model and apply it to the analysis of variations in the utilization of alternative cardiac procedures in a national cohort of elderly Medicare patients who had an acute myocardial infarction during 1987. The model is designed to accommodate clustered multinomial data with covariate vectors available on individual cases and on clusters. We present a Bayesian approach to fitting and checking the model using simulated values from the posterior distribution of the parameters. The simulation algorithms are based on Gibbs sampling in combination with Metropolis steps. Using the hierarchical polytomous regression model, we examine how the rates of cardiac procedures depend on patient-level characteristics, including age, gender and race, and whether there exist interstate differences and regional patterns in the use of these procedures.     

Limiting amino acids in meat and bone and poultry by-product meals

In situ, digestion, and growth studies were conducted to evaluate four meat and bone meals and six poultry by-product meals as sources of escape protein and to predict the first-limiting amino acid for growing calves. Escape protein values, determined by 12-h in situ incubation, ranged from 41.7 to 51.0% of CP for meat and bone meals; poultry by-product meals ranged from 32.0 to 39.8%. True protein digestion in the gastrointestinal tract of lambs differed among protein sources (P < .05), ranging from 79 to 95%. In each of three growth trials, 60 steers (258 +/- 24, 241 +/- 23, and 230 +/- 16 kg for Trials 1, 2, and 3, respectively) were supplemented with 4 of the 10 protein sources along with a urea supplement. Protein sources were fed at 30, 40, 50, and 60% of the supplemental CP, with urea supplying the remainder. Protein efficiency differed among treatments ( P < .10), ranging from .61 to 1.55. Amino acid composition was determined for each protein source, and the individual metabolizable amino acids were regressed on the protein efficiency values. Escape protein values were correlated (R2 = .75) with protein efficiency but had a negative slope. Metabolizable methionine was the only amino acid moderately correlated (R2 = .40, slope = 1.9) to protein efficiency, whereas other amino acids either correlated poorly or had negative slopes. These data indicate that the protein value of meat and bone meal and poultry by-product meal is limited by the amount of metabolizable methionine they contain.