Assessment of Optimal Selected Prognostic Factors

The identification and assessment of prognostic factors is one of the major tasks in clinical research. The assessment of one single prognostic factor can be done by recently established methods for using optimal cutpoints. Here, we suggest a method to consider an optimal selected prognostic factor from a set of prognostic factors of interest. This can be viewed as a variable selection method and is the underlying decision problem at each node of various tree building algorithms. We propose to use maximally selected statistics where the selection is defined over the set of prognostic factors and over all cutpoints in each prognostic factor. We demonstrate that it is feasible to compute the approximate null distribution. We illustrate the new variable selection test with data of the German Breast Cancer Study Group and of a small study on patients with diffuse large B‐cell lymphoma. Using the null distribution for a p‐value adjusted regression trees algorithm, we adjust for the number of variables analysed at each node as well. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Tracheostomy Tube Failure in Obstructive Sleep Apnea

In our institutions we routinely do posttracheostomy sleep studies on patients being treated for obstructive sleep apnea. We have identified several patients who failed to show objective evidence of improvement after tracheostomy. From our studies we have found that both mechanical obstruction and concomitant respiratory control dysfunction caused this failure. A unique tracheostomy tube was constructed to treat the subset of patients with internal collapse of the tracheostomy tube.     

Transport and phosphorylation of disaccharides by the ruminal bacterium Streptococcus bovis

Toluene-treated cells of Streptococcus bovis JB1 phosphorylated cellobiose, glucose, maltose, and sucrose by the phosphoenolpyruvate-dependent phosphotransferase system. Glucose phosphorylation was constitutive, while all three disaccharide systems were inducible. Competition experiments indicated that separate phosphotransferase systems (enzymes II) existed for glucose, maltose, and sucrose. [14C]maltose transport was inhibited by excess (10 mM) glucose and to a lesser extent by sucrose (90 and 46%, respectively). [14C]glucose and [14C]sucrose transports were not inhibited by an excess of maltose. Since [14C]maltose phosphorylation in triethanolamine buffer was increased 160-fold as the concentration of Pi was increased from 0 to 100 mM, a maltose phosphorylase (Km for Pi, 9.5 mM) was present, and this activity was inducible. Maltose was also hydrolyzed by an inducible maltase. Glucose 1-phosphate arising from the maltose phosphorylase was metabolized by a constitutive phosphoglucomutase that was specific for alpha-glucose 1-phosphate (Km, 0.8 mM). Only sucrose-grown cells possessed sucrose hydrolase activity (Km, 3.1 mM), and this activity was much lower than the sucrose phosphotransferase system and sucrose-phosphate hydrolase activities.     

Lysostaphin lysis procedure for detection of Staphylococcus aureus by the firefly bioluminescent ATP method

The objective of this study was to examine the use of lysostaphin as an ATP-extracting agent for the estimation of Staphylococcus aureus cell number by a rapid bioluminescent ATP method. The results of the study showed that lysostaphin (22 U/ml) was able to lyse most of the S. aureus cells (greater than 99.9%) at room temperature in 1 min; ATP of S. aureus cells extracted by the lysostaphin lysis procedure was stable for 24 h in the presence of EDTA; there was a linear relationship between the ATP content and the number of S. aureus cells (ranging from 10(4) to 10(6) CFU/ml); and the lysis of S. aureus cells by lysostaphin allowed estimation of the number of S. aureus cells in mixed cultures and in meat samples.     

Biologic and molecular characterization of two newly isolated ras-containing murine leukemia viruses.

A murine sarcoma virus (MSV) was recovered from an (NFS X NS.C58v-1) F1 mouse which developed splenic sarcoma and erythroleukemia 6 months after inoculation with a mink cell focus-inducing murine leukemia virus (MuLV) isolated from an NFS mouse infected with a wild mouse ecotropic MuLV. The MSV, designated NS.C58 MSV-1, induced foci of transformation in mouse and rat fibroblasts, and inoculation of mice of various strains 2 weeks of age or younger resulted in erythroleukemia and sarcomatous lesions in spleen, lymph node, and brain. The MSV provirus was molecularly cloned from a genomic library prepared from transformed non-producer rat cells. The 8.8-kilobase proviral DNA contained a 1.0-kilobase p21 ras coding segment which replaced most of the gp70-encoding portion of an MuLV, most likely the endogenous C58v-1 ecotropic virus. The ras oncogene is closely related to v-Ha-ras by hybridization, expression of p21 protein, and nucleotide sequence. It is nearly identical in sequence to v-bas, the only previously described transduced, activated mouse c-ras. At position 12 in the p21 coding region, arginine is substituted for the naturally occurring glycine present in c-ras. A second MSV isolate is described which is similar to NS.C58 MSV-1 except for a 100- to 200-base-pair deletion in the noncoding region of the ras-containing insert.     

Comparison of genetic behaviour of the transposable element Tam3 at two unlinked pigment loci in Antirrhinum majus

Summary In Antirrhinum majus the transposable element Tam3 has been described at two unlinked loci pallida and nivea, both of which are required for the production of anthocyanin pigment in flowers. In each case the element is inserted in the promoter region and gives a variegated phenotype. We show that the rate of Tam3 excision at both loci is greatly affected by temperature, being approximately 1000-fold higher at 15°C compared with 25°C. Tam3 is also controlled by an unlinked gene Stabiliser, which considerably reduces excision rate. We show that the high degree of sensitivity to temperature and Stabiliser is an intrinsic property of Tam3 which is not shared by an unrelated element, Tam1. The Tam3 insertion at nivea gives rise to a series of alleles which confer reduced pigmentation, novel spatial patterns and changed instability. These are probably a result of imprecise excision and rearrangements of the Tam3 element.     

Natal philopatry and recruitment of willow ptarmigan in north central and northwestern Canada

Summary Natal philopatry and recruitment were measured in two populations of willow ptarmigan; one near Churchill, Manitoba and the other in northwestern British Columbia. We examined the return of tagged offspring in subsequent years with respect to geographical area, annual variation, their age when tagged, their sex, their body weight, age and number of their parents, and time of hatch (first nest or renest). Most chicks were tagged before they fledged, but chicks tagged after that had the highest rate of return. We also observed a strong positive relationship between fledging success of broods and offspring return in following years.Patterns of offspring return were similar in both populations except that male offspring in Manitoba settled closer to their natal sites than those in British Columbia and more yearling captured in Manitoba had been tagged as chicks. Return of offspring did not vary with year, their body weights shortly after hatch, or with the age or number of parents raising them. However, a significantly higher proportion of offspring hatched from first nests (first-initiated clutches) returned compared to those hatched from renests (replacement clutches). The low return of chicks hatched from renests may due to low survival, low philopatry, or both. We observed no differences in the mating status (recruitment) of returning offspring with respect to the time they hatched or the number of parents that raised them.     

Differences among human immunodeficiency virus strains in their capacities to induce cytolysis or persistent infection of a lymphoblastoid cell line immortalized by Epstein-Barr virus.

Four strains of human immunodeficiency virus (HIV) manifest consistent differences in biologic behavior after infection of the X50-7 line of human umbilical cord lymphocytes immortalized by Epstein-Barr virus (EBV). Some dilutions of the first strain examined, human T-cell lymphotropic virus type III B, which is derived from a pool of patient isolates propagated in H9 cells, caused transient cytopathic effects (CPE) followed by recovery of a subpopulation of X50-7 cells which became virus carrier cultures. Other dilutions of the same virus stock completely lysed X50-7 cells. Two other strains, RF2 and YW, both from individual patients with acquired immune deficiency syndrome, always induced complete cytolysis of X50-7 cells at all dilutions which infected the cells. However, RF2 did establish persistent infection of H9 cells. A fourth strain, PH1-MN, from a child with acquired immune deficiency syndrome-related complex, induced only transient CPE in X50-7 and H9 cells, which thereafter always recovered to form carrier cultures. For all four strains, the dilutions of HIV stocks which caused CPE corresponded to dilutions which resulted in the detection of HIV polypeptides by immunoblot. Cytolysis in HIV-infected X50-7 cells was accompanied by a decrease in the amount of EBV nuclear antigen; however, HIV infection did not induce EBV replication. Thus CPE in X50-7 cells is due to replication of HIV per se and not to activation of EBV. The observations indicate that there are differences in the cytolytic properties of HIVs and that these differences are influenced by the target cell.     

A method for the separation and partial purification of the three forms of nitrate reductase present in wild-type soybean leaves

A rapid and simple purification method was used to separate and purify nitrate reductases (NR) from Williams soybean leaves. Blue Sepharose columns were sequentially eluted with 50 millimolar NADPH and 50 millimolar NADH, thus separating NAD(P)H:NR from NADH:NRs. Subsequent purification of the collected peaks on a fast protein liquid chromatography-Mono Q column enabled separation of two NADH:NRs. Sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed that the subunit relative molecular mass for all three NR forms (constitutive NAD(P)H:NR [pH 6.5], EC 1.6.6.2; constitutive NADH:NR [pH 6.5], EC not assigned; and inducible NADH:NR [pH 7.5], EC 1.6.6.1) was approximately 107 to 109 kilodaltons. All three NRs showed similar spectra with absorption maxima at 413 and 273 nanometers in the oxidized state, and with the characteristics of a cytochrome b type heme upon reduction with NADH (absorption maxima at 556, 527, and 424 nanometers). The technique developed provides an improved separation of the three NR forms from soybean leaves. The similarity of the NRs with regard to their cytochrome b₅₅₆ type heme content and in relative molecular mass indicated that other differences must exist to account for the different kinetic and physical properties previously reported.