Energy transfer to acceptors in solids with dynamically changingeffective concentrations

Consideration is given to energy transfer in solids between donors and acceptors under conditions in which the number and position of available acceptors change with time. Theoretical expressions and a simulation model are developed and shown to agree with one another. The application of this model to cerium-doped yttrium-aluminum-garnet is discussed     

Responses of auditory-cortex neurons to structural features of natural sounds

Sound-processing strategies that use the highly non-random structure of natural sounds may confer evolutionary advantage to many species. Auditory processing of natural sounds has been studied almost exclusively in the context of species-specific vocalizations, although these form only a small part of the acoustic biotope. To study the relationships between properties of natural soundscapes and neuronal processing mechanisms in the auditory system, we analysed sound from a range of different environments. Here we show that for many non-animal sounds and background mixtures of animal sounds, energy in different frequency bands is coherently modulated. Co-modulation of different frequency bands in background noise facilitates the detection of tones in noise by humans, a phenomenon known as co-modulation masking release (CMR). We show that co-modulation also improves the ability of auditory-cortex neurons to detect tones in noise, and we propose that this property of auditory neurons may underlie behavioural CMR. This correspondence may represent an adaptation of the auditory system for the use of an attribute of natural sounds to facilitate real-world processing tasks.     

Response of primary colon cancer cells in hybrid spheroids to 5-fluorouracil

The specific role of sulfhydryl groups in cell-mediated cytotoxicity (CMC) is still unknown. Here we demonstrate that natural killer cells and lymphokine-activated killer cells, when incubated with phenylarsine oxide (PAO), an organoarsenic compound showed a dose- and time-dependent inhibition of CMC and antibody-dependent cellular cytotoxicity (ADCC). PAO interacted directly with the effector cells (EC) without affecting the target cells (TC) or EC:TC conjugate formation. The loss of cytotoxicity was not due to lack of degranulation or to inhibition of serine esterases in PAO-treated cells. However, PAO inhibited the target-induced down regulation of phosphatidylinositol (PI) level in NK cells indicating that PAO blocked the cytolytic cascade at an early stage, upstream of PI. In addition, PAO also did not affect the disulfide link of the zeta-chain dimers, implicated in signal transduction in cytotoxic lymphocytes but did cause the rapid phosphorylation of the zeta chain. Finally, the effect of PAO on CMC was competitively blocked by dithiothreitol, a dithiol, but not by beta-mercaptoethanol, a mono-thiol. Taken together, these results indicate for the first time how sulfyhydryl groups may regulate CMC and ADCC.     

Energy Transfer Between Multi-Sites in Chromium-Thulium-Doped Yttrium Aluminum Garnet

We consider the energy transfer between different sites in chromium-thulium-doped yttrium aluminum garnet. Subtle changes in the spectroscopic levels allow us to selectively excite different sites, with considerably different dynamic and spectral behavior. A new analytical model is developed to account for the complicated energy transfer mechanisms in this crystal.     

Paired STSs amplified from radiation hybrids, and from associated YACs, identify highly polymorphic loci flanking the ataxia telangiectasia locus on chromosome 11q22-23

The high resolution mapping of the ataxia telangiectasia (A-T) locus on chromosome 11q22-23 requires the generation of new polymorphic markers specifically within the segment of 11q22-23 to which the locus has been assigned. We have made use of a library of Alu-PCR clones, amplified from a radiation reduced somatic cell hybrid containing the relevant chromosome 11 segment, to generate sequence tagged sites (STS) within the 11q22-23 region and have used YAC clones to extend the loci identified by these STSs. The identification of paired polymorphisms (from Alu-PCR and the associated YAC derived clone), which are physically linked, but which show minimal linkage disequilibrium, provides a highly informative haplotype for use in genetic linkage analysis in A-T families. We describe the characterisation of 2 such polymorphic loci, D11S535 and D11S611, which map between existing flanking markers, and which provide additional information on the location of the major A-T locus.     

The recipient splenic artery for arterialization in orthotopic liver transplantation

Adequate hepatic arterial reconstruction is essential for successful liver transplantation. In the case of insufficient recipient hepatic arterial flow, most surgeons recommend the use of the aorta for arterialization of the graft. We report here on a technique in which the recipient splenic artery is used in such a setting. The splenic artery is dissected from its origin on a 3-to-4 cm segment and divided. The proximal segment is flipped to the right and anastomosed to the graft's celiac axis in an end-to-end fashion. This technique was used in 7 of 79 orthotopic liver transplantations (9%) because the native hepatic artery was deemed to be inadequate for anastomosis. There were no complications related to the use of this technique and no arterial thromboses. Arterialization of hepatic grafts using the recipient proximal splenic artery is a simple, safe, and efficient technique that can be recommended in the presence of an inadequate recipient hepatic arterial flow.     

Fc receptors are not required for antibody-mediated protection against lethal malaria challenge in a mouse model

The mechanisms by which Abs mediate protection during blood-stage malaria infections is controversial, with some evidence pointing to the direct effect of Abs on parasite invasion and growth, while other studies suggest that Abs act in cooperation with monocytes to achieve parasite inhibition. To determine whether the effector phase of protection in vivo to the rodent parasite Plasmodium yoelii yoelii requires Fc receptor bearing cells, we passively transferred immune sera into FcR gamma-chain knockout mice. Inflammatory macrophages from these knockout mice were unable to mediate phagocytosis or Ab-dependent cell-mediated cytotoxicity (ADCC) through Fc gamma RI, Fc gamma RII, or Fc gamma RIII. Passive transfer of either P. y. yoelii hyperimmune sera or anti-GST-PYC2 sera directed to the major merozoite surface protein (MSP-1) of this parasite enabled both BALB/cByJ mice and FcR gamma-chain-deficient mice to resist lethal P. y. yoelii 17XL (Py17XL) challenge. mAb302, a protective IgG3 Ab, also passively protected both strains of mice. Most of these samples contain Ab isotypes that would not be able to protect mice if their protective effects required Ab-dependent cell-mediated cytotoxicity. These results establish that, in this infection, protection is directly mediated by Abs and does not require the participation of Fc receptors.