Chemical denaturation and modification of ovalbumin alters its dependence on ubiquitin conjugation for class I antigen presentation

Class I presentation of microinjected native OVA by a temperature-sensitive ubiquitin conjugation mutant, ts85, but not wild-type murine cells, was markedly inhibited following incubation at a nonpermissive temperature. In contrast, the nonpermissive temperature did not affect class I presentation of a minimal OVA peptide expressed in the cytosol. Therefore, these results provide a second example in which a temperature sensitive mutation in the ubiquitin conjugation pathway inhibits MHC class I presentation of native OVA. Surprisingly, incubation at the nonpermissive temperature did not inhibit class I presentation of chemically denatured and alkylated OVA microinjected into the cytosol of mutant cells. Similarly, the presentation of endogenously synthesized OVA (which is expressed from a recombinant vaccinia virus and, presumably, is misfolded in the cytosol) was also not inhibited in both mutant cell lines. Methylation of the lysine groups in denatured OVA, which blocks ubiquitin conjugation, reduced but did not eliminate the presentation of denatured OVA, providing evidence for both ubiquitin-dependent and ubiquitin-independent pathways for class I presentation. In contrast, a proteasome inhibitor blocked class I presentation of all forms of OVA, while a control peptide aldehyde was not inhibitory. These results indicate that modification of the structure of a protein can influence its requirements for ubiquitin conjugation for efficient class I presentation, with the key alteration possibly being the loss of proper conformation. However, regardless of the form of the Ag, the proteasome appears to be required for generating peptides from both endogenously synthesized and microinjected OVA for class I presentation.     

如何调整家庭影院系统--嗽叭摆位篇

现在家庭影院红透半片天,很多人都想在自己的家居环境里搭建属于自己的影院,不过,家庭影院的设置包了含了视频与音频两个项目,其中以音频的调整最为繁复,家庭影院兼具音乐欣赏与看大片,很多发烧老手尚且玩的满身大汗还只能发挥几成不到的效果,广大的一般消费者就只能仰赖店家的安装与自己摸索来尽量让自己的家庭影院能达到出声的效果.     

Inducible amp C beta-lactamase producing gram-negative bacilli from blood stream infections: frequency, antimicrobial susceptibility, and molecular epidemiology in a national surveillance program (SCOPE)

A surveillance study of nosocomial blood stream infections [Surveillance and Control of Pathogens of Epidemiologic Importance (SCOPE)] was conducted during a 14-month period in 1995 to 1996 in approximately 50 American medical centers. Among the 4725 blood stream infections, the etiologic agent was Enterobacter spp. in 230, Citrobacter freundii in 24, and Serratia marcescens in 65. The vast majority of these isolates (89%) had been sent to the University of Iowa including 198 Enterobacter spp. (46 Enterobacter aerogenes, 141 Enterobacter cloacae, 11 other Enterobacter spp.), 23 C. freundii, and 62 S. marcescens. Because these species are capable of producing Amp C beta-lactamase, we examined their susceptibility to 12 broad-spectrum antimicrobial agents. The frequency of resistance to ceftazidime and the molecular epidemiology of ceftazidime-resistant strains was also examined. Among the Enterobacter spp. and C. freundii isolates, resistance to third generation cephalosporins (ceftazidime, ceftriaxone) and broad-spectrum semisynthetic penicillins (piperacillin), with or without an enzyme inhibitor (piperacillin/tazobactam), was high, e.g., 35 to 50%. The S. marcescens isolates were quite susceptible to all agents tested. Both imipenem and cefepime were active against virtually all isolates tested including 84 stably derepressed Amp C-producing ceftazidime-resistant strains of Enterobacter spp. and C. freundii. The overall rank order of activity for the six best agents against these Amp C-producing strains was: imipenem (100% susceptible) > amikacin = cefepime (98.6%) > ciprofloxacin = gentamicin = ofloxacin (93.6 to 94.0%). Molecular typing studies of ceftazidime-resistant E. cloacae using an automated ribotyping system, as well as pulsed-field gel electrophoresis, indicated that although clonal spread of a single strain occurred in some of the medical centers, most of the episodes of bacteremia were caused by patient-unique strains. Control of these resistant organisms will require attention to microbiologic recognition of phenotypes, to infection control practices, and to limiting the overuse of certain extended spectrum beta-lactams.     

Do young children reverse ambiguous figures?

Most adult observers tend not to reverse ambiguous figures if they are not informed about the ambiguity of the figure. The question was asked whether very young children who have rarely, if ever, seen any kinds of ambiguous figures will reverse if uninformed, and also how they will behave if they are informed. It was found that 3 and 4 year olds never reverse when presented with two different kinds of ambiguous figures when uninformed, and only some do even when informed; further, those that do reverse do so only once or twice over a 60 s inspection period. These results are interpreted as further confirmation of an earlier finding with adults--that reversal is not simply a matter of prolonged inspection of an ambiguous figure leading automatically to neural satiation. Instead, cognitive factors such as utilization of memory and intention are implicated.     

The effects of varying conceptualizations of job performance on adverse impact, minority hiring, and predicted performance.

The present research explored the effects of various strategies of weighting criterion dimensions on adverse impact, minority hiring, and job performance. In particular, this research compared strategies that vary the weight of task and contextual performance dimensions in calculating a composite criterion measure, in terms of their effects on regression weights assigned to predictors and effects on adverse impact, percentage of minorities hired, and predicted performance. With a Monte Carlo simulation based on meta-analytic evidence of multiple predictor and criterion relationships, the authors illustrate how organizations might think through the consequences of varying conceptualizations of job performance in selection contexts. Approaches that simultaneously increase aggregate predicted job performance and reduce adverse impact are described and illustrated. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Appropriate method for the least squares analysis of categorical data.

Attempts to clarify some issues that have stemmed from J. E. Overall and D. K. Spiegel's (see record 1970-01534-001) article on least squares analysis, as well as from a number of subsequent articles. C. E. Werts and R. L. Linn (1971) provided a logical basis for selecting Method 3 from the Overall and Spiegel article. The present article outlines statistical as well as substantive arguments for the choice of Method 3. A variation of Method 3 is also suggested. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Responsiveness of homocysteine concentrations to food and supplemental folate intakes in smokers and never-smokers enrolled in a diet intervention trial.

We investigated circulating homocysteine concentrations in relation to smoking, folate intake (from food and supplements), serum folate concentrations, and other dietary variables. The present study is part of a parent trial assessing the effects of increasing vegetable, fruit, and fiber intakes and reducing the percentage of energy obtained from fat on breast cancer recurrence in 3,088 women previously diagnosed with breast cancer. Of the 121 smokers enrolled in the parent trial, 85 were available at baseline for the present study and were randomly matched to 85 never-smokers on baseline folate intake, age, and intervention status. Follow-up data were available on 53 smokers (22 intervention and 31 comparison) and 56 never-smokers (24 intervention and 32 comparison). No significant differences in circulating homocysteine and folate concentrations were observed between smokers and never-smokers at baseline. For smokers, significant decreases in circulating homocysteine and significant increases in folate concentrations (p < .05) from baseline to 12 months were observed in the comparison group. For never-smokers, significant decreases in circulating homocysteine and significant increases in folate concentrations were observed in the intervention and comparison groups (p < .05). In the multivariate analysis, changes in serum folate concentration and supplemental folic acid were significantly associated with change in plasma homocysteine concentrations (p < .05). These findings show that increasing supplemental folic acid can reduce homocysteine concentrations, which may have implications for lowering cardiovascular disease risk for smokers and never-smokers.     

Fertility following bilateral ovarian wedge resection: a critical analysis of 90 consecutive cases of the polycystic ovary syndrome

Fertility following bilateral ovarian wedge resection (BOWR) was evaluated in a retrospective cohort study of 90 consecutive cases of the polycystic ovary syndrome. Post-BOWR follow-up was available for varying time spans of up to 10 years. BOWR resulted in the resumption of menstrual cyclicity in 91.1% (82/90) of the cases. However, within this ovulatory group, 26 patients were characterized by oligo-ovulation and a significantly reduced conception rate (29.2%), as compared with that of 56 normo-ovulatory counterparts (60.3%). Although the crude overall conception rate for this series was 47.8%, the overall cumulative probability of conception at the end of follow-up as determined by life table analysis was 73%. The likelihood of conception at any given point in time was estimated by a monthly fecundability rate of 1.34%. Our findings also indicate that the probability of post-BOWR conception was unaffected by age, race, ward status, or duration of infertility. In contrast, persistent post-BOWR oligo- or anovulation and the presence of concurrent tuboperitoneal disease were reaffirmed as the most important determinants of the likelihood of post-BOWR conception. A minimum incidence of 7.8% was documented for acquired post-BOWR pelvic disease.     

Factors affecting the rate of deterioration in the frying qualities of fats. 1 i. exposure to air

The effect of heating fats in air and the effect of heating fats in an inert atmosphere were compared, and the relationship of air to changes in the frying characteristics of fat studied. The frying characteristics of a fat did not change to an extent that is commercially significant even after 48 hr heating at 375F in the absence of air; fats heated under identical conditions but in the presence of air, changed radically. It was found, also, that fat which had changed appreciably in frying characteristics when heated in air did not continue to change significantly when heated further under nitrogen. Hence, presence of oxygen was shown to be a necessary condition for the deterioration of the frying qualities of fat at frying temp. Rate of change of the frying characteristics was found to be directly proportional to the degree of exposure of fat surface to the oxygen.