Overnight Delay Research Articles

Cueing in a perceptual task causes long-lasting interference that generalizes across context to affect only late perceptual learning and is remediated by the passage of time

AbstractPerceptual learning, the improvement in sensory discriminations with practise, is also subject to stimulus-specific interference from temporal jitter in a learning session or manipulations applied between or immediately after sessions. We demonstrate a novel form of perceptual interference where even a brief cueing exposure to a complex speech-in-noise task produces a forward interference on subsequent speech-in-noise learning. This potent interference generalizes across cueing context but specifically affects only late learning in the subsequent task, is resistant to the remediating effects of sleep and persists across an overnight delay involving sleep, and can be evoked by a single exposure 1 day before the learning. Learning in the speech-in-noise task is due to generalized improvements in discriminating and extracting signals (speech) from noise and we hypothesize that the forward interference represents interference with improvements in access to higher-level representations in rapid perception of ecologically-familiar complex signals such as speech from background noise.

Influence of delayed CSF storage on concentrations of phospho-tau protein (181), total tau protein and beta-amyloid (1–42)

It is generally accepted that cerebrospinal fluid (CSF) biomarkers such as tau protein, phosphorylated tau protein (threonine 181) and beta-amyloid (1–42) can facilitate early and differential diagnosis of Alzheimer's disease (AD). Since the respective concentrations can only be measured in a number of specialized centers, time to CSF specimen work-up has been considered as crucial for the stability of the respective biomarkers. When shipping of CSF samples is needed for biomarker measurement and immediate freezing of samples is not available, an overnight delay of up to 24 h frequently occurs. Therefore, we investigated the potential impact of a 24 h delayed freezing on CSF biomarker concentrations and compared it to 2 h storage (room temperature, 20 °C) and an immediate freezing. First, storage at room temperature for 2 h had only marginal, non-significant effects on the concentrations of CSF total tau protein and phospho-tau protein (181) compared to immediate freezing. Second, storage at room temperature for 24 h did not significantly affect total tau protein or phospho-tau protein but beta-amyloid (1–42) concentrations which increased significantly compared to the samples frozen immediately. These results indicate that CSF samples for the evaluation of total tau and phospho-tau protein may be kept at room temperature for up to 24 h whereas CSF samples for beta-amyloid (1–42) need to be frozen immediately.

Embryo Biopsy for Stem Cells: Trading Old Problems for New

Embryo Biopsy for Stem Cells:Trading Old Problems for New Kathy L. Hudson The team of scientists at Advanced Cell Technology led by Robert Lanza has announced that it has developed a method to create stem cells from a single cell extracted from a human embryo without destroying the embryo. Heralded by some as the perfect solution to the political stalemate over funding stem cell research, Lanza's work—at the moment—raises as many questions as it answers. Currently, scientists harvest stem cells from early-stage embryos, usually excess embryos from IVF that would otherwise be discarded. The embryo is destroyed in the process. Lanza asserts that scientists could remove one cell from an early-stage human embryo to create a new stem cell line, preserving the remaining embryo for transfer to a woman's womb to initiate a pregnancy. A similar technique—under the name preimplantation genetic diagnosis—is used rather routinely in IVF clinics. In PGD, the cell undergoes genetic analysis in order to test embryos for genetic diseases or conditions. Lanza also suggests—although he did not test the claim experimentally—that a single cell removed from the [End Page 50] embryo could be used simultaneously for dual purposes: Let it grow and divide overnight, he says, and use the resulting multiple cells both to perform PGD and to grow stem cell lines. If PGD shows the embryo to be unaffected it can be transferred to a woman's womb. Theoretically, he points out, if the stem cell lines develop successfully, the new baby will have his or her very own stem cell line from which matched tissue or other therapies can be grown. So what's wrong with this picture? First, taking a cell from an embryo brings risk—how much risk is unknown. It's a touchy time for a young embryo—intercellular communication networks are being set up and a host of other critical functions are being initialized. Moreover, removing a single cell from a tiny embryo requires "good hands" on the part of a lab technician—and even with the best of hands, some embryos don't survive. Biopsied embryos survive freezing much less well than intact embryos, and some evidence suggests embryos that survive the biopsy are not as good at implanting in the womb. It is thus almost certainly a nonstarter to ask couples going through IVF to contribute a cell for stem cell research. The risks of embryo biopsy could reduce the likelihood that IVF would succeed. The prospective parents already have only about a one-in-three chance of having a baby from any given IVF cycle. The odds are reduced if the embryo's viability is impaired, and reduced even more if a biopsied embryo is frozen for later transfer. These doubts led Lanza and his colleagues to suggest that this approach to stem cell research be used only in the context of PGD. Lanza's logic is that if prospective parents contemplating PGD can still get the benefit of genetic analysis, they would not object if the blastomere removed for genetic analysis also gives rise to stem cells, and especially not if it gives their future offspring the chance to have matched stem cell lines for potential future therapeutic use. Two for the price of one. The problem is that Lanza and his colleagues only suggest this "two-fer"—they have not actually done it. Nor have they analyzed the additional risk it brings to families seeking PGD. Presumably, under Lanza's scenario, couples contemplating PGD would be told that they can contribute to stem cell research by permitting two changes to the way PGD is typically performed: an overnight delay, and genetic analysis on the cells that have grown overnight rather than on the original cell removed from the embryo. There is no way to know how the additional time and cell division would affect the chance of genetic "glitches" being introduced. PGD accuracy could plummet as a result. Worse, more than 40 percent of the individual blastomeres failed to divide in culture in Lanza's study, and half of those, or about a third of the starting cells, divided only once. Thus, the families...

Liposome-encapsulated hemoglobin modulates lipopolysaccharide-induced tumor necrosis factor-alpha production in mice.

To investigate the effect of liposome-encapsulated hemoglobin, an experimental blood substitute, on the function of the mononuclear phagocytic system in normovolemic mic, in ex vivo murine splenocytes and in a transformed murine monocytic cell line, RAW 264.7. Prospective, randomized trial. Center for Biomolecular Science and Engineering, Naval Research Laboratory, and the Thomas Jefferson University. Female Balb/c mice (n = 27). Mice were injected into the tail vein with liposome-encapsulated hemoglobin or liposome vehicle and were killed at varying time points for blood sampling and splenocyte isolation and culture. Injection of liposome-encapsulated hemoglobin in mice (2.2 of lipid/kg and 0.56 g of hemoglobin/kg, n = 9) did not increase serum tumor necrosis factor (TNF)-alpha concentrations at 2, 8, 15, and 24 hrs after administration. In the ex vivo procedure, lipopolysaccharide (1 microgram/mL)-induced TNF-alpha production by splenocytes from mice injected with liposome-encapsulated hemoglobin was attenuated at 2 and 4 hrs (73%, p = .002 at 2 hrs), compared with TNF-alpha production by splenocytes from sham animals challenged with the same concentration of lipopolysaccharide. In the in vitro procedure, simultaneous exposure of liposome-encapsulated hemoglobin (0.88 to 8.8 mg/mL) and lipopolysaccharide (0.125 to 1 microgram/mL) to the murine-derived, peritoneal monocytic RAW 264.7 cell line showed significantly reduced TNF-alpha peptide, but not messenger RNA, 1 to 4 hrs after exposure as compared with cells challenged with lipopolysaccharide alone. This effect correlated with the rapid phagocytosis (1 hr to 4 hrs) of liposome-encapsulated hemoglobin by RAW 264.7 cells. Phagocytic activity in RAW 264.7 cells exposed to both liposome-encapsulated hemoglobin and lipopolysaccharide showed reduced uptake compared with uptake of liposome-encapsulated hemoglobin. The liposome-induced reduction in TNF-alpha peptide production elicited by lipopolysaccharide was countered by extending the time period to an overnight delay between liposome-encapsulated hemoglobin exposure and lipopolysaccharide challenge. Liposome-encapsulated hemoglobin incubated with lipopolysaccharide in vitro, and subsequently washed to remove free lipopolysaccharide, stimulated TNF-alpha expressed by RAW 264.7 cells. Incubation with liposome-encapsulated hemoglobin alone did not evoke TNF-alpha production in these cells. These data suggest that liposome-encapsulated hemoglobin modulates the response of the mononuclear phagocyte system to endotoxin, possibly through binding of lipopolysaccharide, presentation to macrophages with subsequent phagocytosis, and modulation of cytokine response by a posttranscriptional mechanism. This effect is attenuated by extending the period between exposure to liposome-encapsulated hemoglobin and endotoxin. The clinical relevance of these findings awaits further investigation.

Bacteriological hazards of contaminated enteral feeds

Enteral feeds are increasingly prescribed for hospital patients requiring nutritional support, yet there is little to suggest (Lee, 1979; Drugs and Therapeutics Bulletin, 1980; Brown, 1981) that the infection hazard of bacterial contamination of these feeds is commanding the attention that it deserves. More than ten years ago it was shown that items of food prepared in hospital kitchens, including milk feeds and pureed food, were frequently contaminated with Gram-negative bacilli such as Escherichia coli, Pseudomonas aeruginosa and Klebsiella aerogenes (Shooter et al., 1969, 1971; Cooke et al., 1970; Montgomerie et al., 1970). In a later study it was found that as many as 68 per cent of enteral feeds, which were prepared in a hospital diet kitchen and destined for intensive care patients, were contaminated with up to lo4 klebsiellae per ml (Casewell & Phillips, 1978). But bacterial counts in excess of 106 per ml have been recorded (Montgomerie et al., 1970; Bastow, Greaves & Allison, 1982). The range of organisms reported is also extending and includes Enterobacter cloacae (Casewell, Cooper & Webster, 1981), Proteus spp., Streptococcus faecalis, Staphylococcus epidermidis and, more threateningly, Bacillus cereus and Staph. aureus (Bastow et al., 1982). Even with sterile ingredients, mixing in the diet kitchen may result in counts of up to 10s per ml (Bastow et aZ., 1982). The reservoirs of Gram-negative bacilli that have been demonstrated in diet kitchens include mixers, homogenizers, dish cloths, work surfaces, metal sieves, propylene jugs and a detergent dispenser (Montgomerie et al., 1970; Casewell & Phillips, 1978; Casewell et al., 1981). The elimination of all these reservoirs is probably impossible. Inoculated feeds may not reach the patient until an overnight delay, and the change from bolus to continuous-drip nasogastric feeding over a further 12-24 h provides ample opportunity for multiplication of organisms in this very adequate culture medium (Simmons, 1981). What, then, are the theoretical and actual consequences of ingesting these contaminated feeds? Firstly, there seems to be no reason why, sooner or later, enteric pathogens will not be involved with obvious consequences. Indeed, hospital-prepared feeds have already been suspected, although not proven, as the cause of hospital-acquired gastroenteritis caused by Salmonella enteritidis of obscure origin (Gill & Gill, 1981), and Staph. aweus and B. cereus have also been found in feeds (Bastow et al., 1982). Secondly, even in the absence of contamination with more aggressive pathogens, it is clear that the number of organisms ingested often exceeds the number,