Subunit interactions influence the biochemical and biological properties of Hsp104

Point mutations in either of the two nucleotide-binding domains (NBD) of Hsp104 (NBD1 and NBD2) eliminate its thermotolerance function in vivo. In vitro, NBD1 mutations virtually eliminate ATP hydrolysis with little effect on hexamerization; analogous NBD2 mutations reduce ATPase activity and severely impair hexamerization. We report that high protein concentrations overcome the assembly defects of NBD2 mutants and increase ATP hydrolysis severalfold, changing V(max) with little effect on K(m). In a complementary fashion, the detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate inhibits hexamerization of wild-type (WT) Hsp104, lowering V(max) with little effect on K(m). ATP hydrolysis exhibits a Hill coefficient between 1.5 and 2, indicating that it is influenced by cooperative subunit interactions. To further analyze the effects of subunit interactions on Hsp104, we assessed the effects of mutant Hsp104 proteins on WT Hsp104 activities. An NBD1 mutant that hexamerizes but does not hydrolyze ATP reduces the ATPase activity of WT Hsp104 in vitro. In vivo, this mutant is not toxic but specifically inhibits the thermotolerance function of WT Hsp104. Thus, interactions between subunits influence the ATPase activity of Hsp104, play a vital role in its biological functions, and provide a mechanism for conditionally inactivating Hsp104 function in vivo.     

Reliability and validity of the sideways step test and its correlation with motor function after stroke

[Purpose] This study investigated the intra-rater, inter-rater and test-retest reliability of the sideways step test (SST), its correlation with other indicators of stroke-specific impairment, and the cut-off count best discriminating subjects with stroke from their healthy counterparts. [Subjects and Methods] Forty-three subjects with chronic stroke and 41 healthy subjects older than 50 years participated in this study. The SST was administered along with the Fugl-Meyer motor assessment for the lower extremities (FMA-LE), the five-times sit to stand (5TSTS) test, the Berg Balance Scale (BBS), the movement velocity (MVL) by the limits of stability (LOS) test, the ten-metre walk (10mW) test, the timed “Up and Go” (TUG) test and the Activities-specific Balance Confidence (ABC) scale. [Results] The SST showed good to excellent intra-rater, inter-rater and test-retest reliability. The SST counts correlated with 5TSTS times, 10mW times, TUG times, and the FMA-LE and BBS scores. SST counts of 11 for the paretic leg and 14 for the non-paretic leg were found to distinguish the healthy adults from subjects with stroke. [Conclusion] The sideways step test is a reliable clinical test, which correlates with the functional strength, gait speed, and functional balance of people with chronic stroke.Key words: Balance, Stroke, Rehabilitation     

Observer variability in the pulmonary examination

Observer variability in the pulmonary examination was assessed by having four blindfolded observers (two medical students and two pulmonary physicians) twice examine 31 patients with abnormal pulmonary findings. Examiners were consistent in the repetitive detection of pulmonary abnormalities in 74–89% of the examinations; conversely, 11–26% of the time they disagreed with themselves. Although pulmonary specialists recorded fewer (55% of observations) abnormal findings than did medical students (74%), they were significantly (p=0.008) less self-consistent than were the students. There was no clear trend in agreement between examiners (kappa=0.20−0.49). Each examiner’s findings were compared with those of physicians specially trained in pulmonary examination. Dichotomous variables (wheezes, crackles, rubs) were more reliably detected (kappa=0.30−0.70) than graded variables (tympany, dullness, breath sound intensity), where kappa=0.16−0.43. The authors suggest that dichotomous variables deserve greatest clinical reliance; that time in training, alone, does not improve clinical performance; and that there is a disconcertingly large amount of inter- and intraobserver disagreement in this fundamental clinical task. Received from the Division of General Internal Medicine, Department of Medicine; the Division of Biometry, Department of Community and Family Medicine, Duke University Medical Center, Durham, North Carolina; and the Ambulatory Care Service and Health Services Research Field Program, Durham V.A. Medical Center, Durham, North Carolina.     

Assessment of aldehyde dehydrogenase in viable cells

Cytosolic aldehyde dehydrogenase (ALDH), an enzyme responsible for oxidizing intracellular aldehydes, has an important role in ethanol, vitamin A, and cyclophosphamide metabolism. High expression of this enzyme in primitive stem cells from multiple tissues, including bone marrow and intestine, appears to be an important mechanism by which these cells are resistant to cyclophosphamide. However, although hematopoietic stem cells (HSC) express high levels of cytosolic ALDH, isolating viable HSC by their ALDH expression has not been possible because ALDH is an intracellular protein. We found that a fluorescent aldehyde, dansyl aminoacetaldehyde (DAAA), could be used in flow cytometry experiments to isolate viable mouse and human cells based on their ALDH content. The level of dansyl fluorescence exhibited by cells after incubation with DAAA paralleled cytosolic ALDH levels determined by Western blotting and the sensitivity of the cells to cyclophosphamide. Moreover, DAAA appeared to be a more sensitive means of assessing cytosolic ALDH levels than Western blotting. Bone marrow progenitors treated with DAAA proliferated normally. Furthermore, marrow cells expressing high levels of dansyl fluorescence after incubation with DAAA were enriched for hematopoietic progenitors. The ability to isolate viable cells that express high levels of cytosolic ALDH could be an important component of methodology for identifying and purifying HSC and for studying cyclophosphamide-resistant tumor cell populations.     

Protection of murine bone marrow by dexamethasone during cytotoxic chemotherapy

Corticosteroids have the ability to suppress the production of growth factors and cytokines and are thus implicated in the negative regulation of hematopoiesis. We have shown that the corticosteroids, prednisolone and dexamethasone, were able to effectively protect progenitor cells in four strains of mice against cell-cycle-specific antimetabolic chemotherapy agents. The highest levels of protection against 5-fluorouracil (FU; 200 mg/kg) were achieved when two or three intraperitoneal injections of dexamethasone were administered between - 7 and +3 hours at a dose of 7.5 mg/kg/injection (optimal dose) or by continuous infusion between -4 and +20 hours. This protective effect is manifested as an increase in the number of high proliferative potential colony-forming cells that survive in the bone marrow 3 days after treatment with FU from between 0.5% and 11% to between 10% and 34% of normal. The bone marrow progenitors and blood cell numbers return to normal from 3 to 5 days and 1 to 2 days earlier, respectively. Less dexamethasone than prednisolone is required to give an equivalent protective effect, which is consistent with their anti-inflammatory potency. These findings are further evidence of the negative regulatory role played by corticosteroids, and indicate that the treatment schedules of corticosteroids during cancer therapy need to be reexamined to obtain the maximum benefit from their use.     

Monoclonal IgM radioimmunoassay for hepatitis B surface antigen: high binding activity in serum that is unreactive with conventional antibodies.

Using a monoclonal IgM antibody (anti-HBs) to hepatitis B surface antigen (HBsAg) in a radioimmunoassay for hepatitis B, we have detected high binding activity in human serum that was unreactive in assays employing conventional anti-HBs reagents. The binding material was isolated from serum by affinity chromatography on monoclonal IgM anti-HBs, and comparison of the material with HBsAg (by sodium dodecyl sulfate/polyacrylamide gel electrophoresis) demonstrated that the two shared several similar polypeptides. Furthermore, comparison of the binding properties of HBsAg and concentrated monoclonal immunoreactive material with conventional and monoclonal anti-HBs reagents demonstrated some antigenic crossreactivity. The molecular weight of the monoclonal immunoreactive material was approximately 2 X 10(6). Immunoprecipitation of the material with monoclonal IgM antibodies and examination by electron microscopy revealed clumped and "spiculated" particles that resembled 22-nm hepatitis B particles coated with the same antibody. Thus, this study suggests that the high-binding-activity material, detected in serum only by the monoclonal radioimmunoassay, is not identical with HBsAg, but it shares some common properties.     

Bacterial colonization dynamics associated with respiratory syncytial virus during early childhood

Respiratory syncytial virus (RSV) is an important cause of early life acute respiratory infections. Potentially pathogenic respiratory bacteria, including Streptococcus pneumoniae, Moraxella catarrhalis, and Haemophilus influenzae are frequently detected during RSV infections and associated with increased illness severity. However, the temporal dynamics of bacterial colonization associated with RSV infection remain unclear. We used weekly nasal swab data from a prospective longitudinal birth cohort in Brisbane, Australia, to investigate bacterial colonization patterns within children aged less than 2 years in the 4‐week period before and after an RSV infection. During 54 RSV infection episodes recorded in 47 children, both S. pneumoniae and M. catarrhalis were detected frequently (in 33 [61.1%] and 26 [48.1%] RSV infections, respectively). In most cases, S. pneumoniae and M. catarrhalis colonization preceded the viral infection, with the nasal load of each increasing during RSV infection. Generally, the dominant serotype of S. pneumoniae remained consistent in the 1 to 2 weeks immediately before and after RSV infection. Little evidence was found to indicate that prior colonization with either bacteria predisposed participants to developing RSV infection during the annual seasonal epidemic. Possible coacquisition events, where the bacteria species was first detected with RSV and not in the preceding 4 weeks, were observed in approximately 20% of RSV/S. pneumoniae and RSV/M. catarrhalis codetections. Taken together our results indicate that RSV generally triggered an outgrowth, rather than a new acquisition, of S. pneumoniae and M. catarrhalis from the resident microbial community.