Experimental Evidence for Millisecond-Timescale Structural Evolution Following the Microsecond-Timescale Folding of a Small Protein

Prior work has shown that small proteins can fold (i.e., convert from unstructured to structured states) within 10  μs. Here we use time-resolved solid state nuclear magnetic resonance (ssNMR) methods to show that full folding of the 35-residue villin headpiece subdomain (HP35) requires a slow annealing process that has not been previously detected. ^{13}C ssNMR spectra of frozen HP35 solutions, acquired with a variable time τ_{e} at 30 °C after rapid cooling from 95 °C and before rapid freezing, show changes on the 3-10 ms timescale, attributable to slow rearrangements of protein sidechains during τ_{e}.

Gadolinium Spin Decoherence Mechanisms at High Magnetic Fields

Favorable relaxation processes, high-field spectral properties, and biological compatibility have made spin-7/2 Gd3+-based spin labels an increasingly popular choice for protein structure studies using high-field electron paramagnetic resonance. However, high-field relaxation and decoherence in ensembles of half-integer high-spin systems, such as Gd3+, remain poorly understood. We report spin-lattice (T1) and phase memory (TM) relaxation times at 8.6 T (240 GHz), and we present the first comprehensive model of high-field, high-spin decoherence accounting for both the electron spin concentration and temperature. The model includes four principal mechanisms driving decoherence: energy-conserving electron spin flip-flops, direct "T1" spin-lattice relaxation-driven electron spin flip processes, indirect T1-driven flips of nearby electron spins, and nuclear spin flip-flops. Mechanistic insight into decoherence can inform the design of experiments making use of Gd3+ as spin probes or relaxivity agents and can be used to measure local average interspin distances as long as 17 nm.

Spectroscopically Orthogonal Spin Labels in Structural Biology at Physiological Temperatures

Electron paramagnetic resonance spectroscopy (EPR) is mostly used in structural biology in conjunction with pulsed dipolar spectroscopy (PDS) methods to monitor interspin distances in biomacromolecules at cryogenic temperatures both in vitro and in cells. In this context, spectroscopically orthogonal spin labels were shown to increase the information content that can be gained per sample. Here, we exploit the characteristic properties of gadolinium and nitroxide spin labels at physiological temperatures to study side chain dynamics via continuous wave (cw) EPR at X band, surface water dynamics via Overhauser dynamic nuclear polarization at X band and short-range distances via cw EPR at high fields. The presented approaches further increase the accessible information content on biomolecules tagged with orthogonal labels providing insights into molecular interactions and dynamic equilibria that are only revealed under physiological conditions.

Triggered Functional Dynamics of AsLOV2 by Time-Resolved Electron Paramagnetic Resonance at High Magnetic Fields

We present time-resolved Gd-Gd electron paramagnetic resonance (TiGGER) at 240 GHz for tracking inter-residue distances during a protein's mechanical cycle in the solution state. TiGGER makes use of Gd-sTPATCN spin labels, whose favorable qualities include a spin-7/2 EPR-active center, short linker, narrow intrinsic linewidth, and virtually no anisotropy at high fields (8.6 T) when compared to nitroxide spin labels. Using TiGGER, we determined that upon light activation, the C-terminus and N-terminus of AsLOV2 separate in less than 1 s and relax back to equilibrium with a time constant of approximately 60 s. TiGGER revealed that the light-activated long-range mechanical motion is slowed in the Q513A variant of AsLOV2 and is correlated to the similarly slowed relaxation of the optically excited chromophore as described in recent literature. TiGGER has the potential to valuably complement existing methods for the study of triggered functional dynamics in proteins.

Time-resolved solid state NMR of biomolecular processes with millisecond time resolution

We review recent efforts to develop and apply an experimental approach to the structural characterization of transient intermediate states in biomolecular processes that involve large changes in molecular conformation or assembly state. This approach depends on solid state nuclear magnetic resonance (ssNMR) measurements that are performed at very low temperatures, typically 25-30 K, with signal enhancements from dynamic nuclear polarization (DNP). This approach also involves novel technology for initiating the process of interest, either by rapid mixing of two solutions or by a rapid inverse temperature jump, and for rapid freezing to trap intermediate states. Initiation by rapid mixing or an inverse temperature jump can be accomplished in approximately-one millisecond. Freezing can be accomplished in approximately 100 microseconds. Thus, millisecond time resolution can be achieved. Recent applications to the process by which the biologically essential calcium sensor protein calmodulin forms a complex with one of its target proteins and the process by which the bee venom peptide melittin converts from an unstructured monomeric state to a helical, tetrameric state after a rapid change in pH or temperature are described briefly. Future applications of millisecond time-resolved ssNMR are also discussed briefly.

Nitroxide-based triradical dopants for efficient low-temperature dynamic nuclear polarization in aqueous solutions over a broad pH range

Dynamic nuclear polarization (DNP) can provide substantial sensitivity enhancements in solid state nuclear magnetic resonance (ssNMR) measurements on frozen solutions, thereby enabling experiments that would otherwise be impractical. Previous work has shown that nitroxide-based triradical compounds are particularly effective as dopants in DNP-enhanced measurements at moderate magic-angle spinning frequencies and moderate magnetic field strengths, generally leading to a more rapid build-up of nuclear spin polarizations under microwave irradiation than the more common biradical dopants at the same electron spin concentrations. Here we report the synthesis and DNP performance at 25 K and 9.41 T for two new triradical compounds, sulfoacetyl-DOTOPA and PEG12-DOTOPA. Under our experimental conditions, these compounds exhibit ssNMR signal enhancements and DNP build-up times that are nearly identical to those of previously described triradical dopants. Moreover, these compounds have high solubility in aqueous buffers and water/glycerol mixtures at both acidic and basic pH values, making them useful in a wide variety of experiments on biomolecular systems.

Millisecond Time-Resolved Solid-State NMR Initiated by Rapid Inverse Temperature Jumps

Elucidation of the detailed mechanisms by which biological macromolecules undergo major structural conversions, such as folding, complex formation, and self-assembly, is a central concern of biophysical chemistry that will benefit from new experimental methods. We describe a simple technique for initiating a structural conversion process by a rapid decrease in the temperature of a solution, i.e., a rapid inverse temperature jump. By pumping solutions through copper capillary tubes that are thermally anchored to heated and cooled blocks, solution temperatures can be switched from 95 to 30 °C (or lower) in about 0.8 ms. For time-resolved solid-state nuclear magnetic resonance (ssNMR), solutions can then be frozen rapidly by spraying into cold isopentane after a variable structural evolution time τ_e. As an initial demonstration, we use this "inverse T-jump" technique to characterize the kinetics and mechanism by which the 26-residue peptide melittin converts from its primarily disordered, monomeric state at 95 °C to its α-helical, tetrameric state at 30 °C. One- and two-dimensional ssNMR spectra of frozen solutions with various values of τ_e, recorded at 25 K with signal enhancements from dynamic nuclear polarization, show that both helical secondary structure and intermolecular contacts develop on the same time scale of about 6 ms. The dependences on τ_e of both intraresidue crosspeak patterns and inter-residue crosspeak volumes in two-dimensional spectra can be fit with a unidirectional dimerization model, consistent with dimerization being the rate-limiting step for melittin tetramer formation.

Trigonal Bipyramidal V3+ Complex as an Optically Addressable Molecular Qubit Candidate

Synthetic chemistry enables a bottom-up approach to quantum information science, where atoms can be deterministically positioned in a quantum bit or qubit. Two key requirements to realize quantum technologies are qubit initialization and read-out. By imbuing molecular spins with optical initialization and readout mechanisms, analogous to solid-state defects, molecules could be integrated into existing quantum infrastructure. To mimic the electronic structure of optically addressable defect sites, we designed the spin-triplet, V3+ complex, (C6F5)3trenVCNtBu (1). We measured the static spin properties as well as the spin coherence time of 1 demonstrating coherent control of this spin qubit with a 240 GHz electron paramagnetic resonance spectrometer powered by a free electron laser. We found that 1 exhibited narrow, near-infrared photoluminescence (PL) from a spin-singlet excited state. Using variable magnetic field PL spectroscopy, we resolved emission into each of the ground-state spin sublevels, a crucial component for spin-selective optical initialization and readout. This work demonstrates that trigonally symmetric, heteroleptic V3+ complexes are candidates for optical spin addressability.

Dressed Rabi Oscillation in a Crystalline Organic Radical

Free electron laser-powered pulsed electron paramagnetic resonance experiments performed at 240  GHz/8.56  T on the crystalline organic radical 1,3-bisdiphenylene-2-phenylallyl reveal a tip-angle dependent resonant frequency. Frequency shifts as large as 11 MHz (45 ppm) are observed during a single Rabi oscillation. We attribute the frequency shifts to a "dressing" of the nutation by spin-spin interactions. A nonlinear semiclassical model which includes a temperature- and sample-geometry-dependent demagnetizing field reproduces experimental results. Because experiments are performed without a cavity, radiation damping, the most common nonlinear interaction in magnetic resonance, is negligible in our experiments.

Multi-step phase-cycling in a free-electron laser-powered pulsed electron paramagnetic resonance spectrometer

Electron paramagnetic resonance (EPR) is a powerful tool for research in chemistry, biology, physics and materials science, which can benefit significantly from moving to frequencies above 100 GHz. In pulsed EPR spectrometers driven by powerful sub-THz oscillators, such as the free electron laser (FEL)-powered EPR spectrometer at UCSB, control of the duration, power and relative phases of the pulses in a sequence must be performed at the frequency and power level of the oscillator. Here we report on the implementation of an all-quasioptical four-step phase cycling procedure carried out directly at the kW power level of the 240 GHz pulses used in the FEL-powered EPR spectrometer. Phase shifts are introduced by modifying the optical path length of a 240 GHz pulse with precision-machined dielectric plates in a procedure we call phase cycling with optomechanical phase shifters (POPS), while numerical receiver phase cycling is implemented in post-processing. The POPS scheme was successfully used to reduce experimental dead times, enabling pulsed EPR of fast-relaxing spin systems such as gadolinium complexes at temperatures above 190 K. Coherence transfer pathway selection with POPS was used to perform spin echo relaxation experiments to measure the phase memory time of P1 centers in diamond in the presence of a strong unwanted FID signal in the background. The large excitation bandwidth of FEL-EPR, together with phase cycling, enabled the quantitative measurement of instantaneous electron spectral diffusion, from which the P1 center concentration was estimated to within 10%. Finally, phase cycling enabled saturation-recovery measurements of T1 in a trityl-water solution at room temperature - the first FEL-EPR measurement of electron T1.

The value of image-guided intensity-modulated radiotherapy in challenging clinical settings

OBJECTIVE

To illustrate the wider potential scope of image-guided intensity-modulated radiotherapy (IG-IMRT), outside of the "standard" indications for IMRT.

METHODS

Nine challenging clinical cases were selected. All were treated with radical intent, although it was accepted that in several of the cases the probability of cure was low. IMRT alone was not adequate owing to the close proximity of the target to organs at risk, the risk of geographical miss, or the need to tighten planning margins, making image-guided radiotherapy an essential integral part of the treatment. Discrepancies between the initial planning scan and the daily on-treatment megavoltage CT were recorded for each case. The three-dimensional displacement was compared with the margin used to create the planning target volume (PTV).

RESULTS

All but one patient achieved local control. Three patients developed metastatic disease but benefited from good local palliation; two have since died. A further patient died of an unrelated condition. Four patients are alive and well. Toxicity was low in all cases. Without daily image guidance, the PTV margin would have been insufficient to ensure complete coverage in 49% of fractions. It was inadequate by >3 mm in 19% of fractions, and by >5 mm in 9%.

CONCLUSION

IG-IMRT ensures accurate dose delivery to treat the target and avoid critical structures, acting as daily quality assurance for the delivery of complex IMRT plans. These patients could not have been adequately treated without image guidance.

ADVANCES IN KNOWLEDGE

IG-IMRT can offer improved outcomes in less common clinical situations, where conventional techniques would provide suboptimal treatment.

A randomised study evaluating the use of pyridoxine to avoid capecitabine dose modifications

BACKGROUND

Pyridoxine is frequently used to treat capecitabine-induced hand-foot syndrome (HFS), although the evidence of benefit is lacking. We performed a randomised placebo-controlled trial to determine whether pyridoxine could avoid the need for capecitabine dose modifications and improve outcomes.

METHODS

A total of 106 patients planned for palliative single-agent capecitabine (53 in each arm, 65%/35% colorectal/breast cancer) were randomised to receive either concomitant pyridoxine (50 mg po) or matching placebo three times daily.

RESULTS

Compared with placebo, pyridoxine use was associated with an increased rate of avoiding capecitabine dose modifications (37% vs 23%, relative risk 0.59, 95% CI 0.29, 1.20, P=0.15) and fewer grade 3/4 HFS-related adverse events (9% vs 17%, odds ratio 0.51, 95% CI 0.15-1.6, P=0.26). Use of pyridoxine did not improve response rate or progression-free survival.

CONCLUSION

Pyridoxine may reduce the need for capecitabine dose modifications and the incidence of severe HFS, but does not impact on antitumour effect.

Selective internal radiation therapy with 90Y-SIR-Spheres microspheres for non-resectable colorectal metastases in the liver

Almost half the patients with colorectal cancer will develop liver metastasis at some stage during their disease. Potentially curative surgical resection is possible in some of these patients. In those patients unsuitable for surgery, treatment with systemic chemotherapy and external radiation therapy is relatively ineffective. Many studies have described the successful use of selective internal radiation therapy (SIRT) with 90Y-SIR-Spheres microspheres in patients with inoperable liver metastasis. The authors report on a patient who has been in complete remission for 1 year after treatment with SIRT.

A radiotherapy technique to improve dose homogeneity around bone prostheses

Purpose. Following limb conserving surgery for bone or soft tissue sarcoma, patients may require post-operative radiotherapy to minimise the risk of local recurrence. In such circumstances the metal prosthesis reduces the dose in its shadow by approximately 10% when using opposed fields. We describe a technique to boost the underdosed area to overcome this problem.Patients or subjects. Seven sequential patients presenting between 1995 and 2001 had their treatment individualised because they had metal prosthesis in the treatment volume.Methods. To improve the target dose homogeneity we used a custom-made keyhole cutout to boost the area in the shadow of the prosthesis. The degree of attenuation caused by the metal prosthesis was estimated and a boost dose calculated. Exit thermoluminescent dosimetry (TLD) was used to confirm the estimates made.Results and discussion. Variation between patients was seen, demonstrating the need for exit TLD to individualise the treatment plan. The use of a boost field provides a method to overcome under-dosage in the shadow of a metal prosthesis. It improves dose homogeneity throughout the target volume and ensures adequate dose intensity around the prosthesis, the site most at risk of local recurrence.

Anti-perforin antibody treatment ameliorates experimental crescentic glomerulonephritis in WKY rats

The depletion of CD8+ cells has been shown to prevent the initiation and progression of antiglomerular basement membrane (GBM) crescentic glomerulonephritis (GN) in Wistar-Kyoto (WKY) rats. In this study, we asked whether CD8+ cells produce their effects by perforin/granzyme-mediated or by Fas ligand (FasL)-mediated pathways. The glomerular mRNA expression of perforin and granzyme B corresponded with the number of CD8+ cells, whereas that of granzyme A, Fas, and FasL did not. The enhanced mRNA level of perforin and granzyme B was not evident in CD8+-depleted rats. The number of apoptotic cells in the glomeruli was significantly increased at day 3. Perforin mRNA was found in cells infiltrating the glomerulus by in situ hybridization and by using dual-staining immunohistochemistry perforin protein was found in glomerular CD8+ cells. We found that perforin was readily visualized at the inner surface of the glomerular capillaries by immunoelectron microscopy. Based on these results, we treated animals with a perforin antibody in vivo and found that it significantly reduced the amount of proteinuria, frequency of crescentic glomeruli, and the number of glomerular monocytes and macrophages, although the number of glomerular CD8+ cells was not changed. Our results suggest that CD8+ cells play a role in glomerular injury as effector cells in part through a perforin/granzyme-mediated pathway in the anti-GBM WKY rat model of crescentic GN.

Effects of grazing residues or feeding corn from a corn rootworm-protected hybrid (MON 863) compared with reference hybrids on animal performance and carcass characteristics

One grazing and two feeding experiments were conducted to compare the feeding value of corn residue or corn grain from a genetically enhanced corn hybrid (corn rootworm-protected; event MON 863) with nontransgenic, commercially available, reference hybrids. In Exp. 1, two 13.7-ha fields, containing corn residues from either a genetically enhanced corn root-worm-protected hybrid (MON 863), or a near-isogenic, nontransgenic control hybrid (CON) were divided into four equal-sized paddocks. Sixty-four steer calves (262 +/- 15 kg) were stratified by BW and assigned randomly to paddock to achieve a stocking rate of 0.43 ha/steer for 60 d, with eight steers per paddock and 32 steers per hybrid. A protein supplement was fed at 0.45 kg/steer daily (DM basis) to ensure protein intake did not limit performance. Steer ADG did not differ (P = 0.30) between steers grazing the MON 863 (0.39 kg/d) and CON (0.34 kg/d) corn residues for 60 d. The four treatments for the feeding experiments (Exp. 2 and 3) included two separate reference hybrids, the near-isogenic control hybrid (CON), and the genetically enhanced hybrid (MON 863) resulting in two preplanned comparisons of CON vs. MON 863, and MON 863 vs. the average of the reference hybrids (REF). In Exp. 2, 200 crossbred yearling steers (365 +/- 19 kg) were fed in 20 pens, with five pens per corn hybrid. In Exp. 3, 196 crossbred yearling steers (457 +/- 33 kg) were fed in 28 pens, with seven pens per corn hybrid. In Exp. 2, DMI and G:F did not differ (P > 0.10) between MON 863 and CON; however, steers fed MON 863 had a greater (P = 0.04) ADG than steers fed CON. Gain efficiency was greater (P = 0.05) for MON 863 cattle than for REF cattle in Exp. 2, but other performance measurements (DMI and ADG) did not differ (P > 0.10) between MON 863 and REF. No differences (P > 0.10) were observed for performance (DMI, ADG, and G:F) between MON 863 and CON or MON 863 and REF in Exp. 3. In terms of carcass characteristics, no differences (P > 0.10) were observed between MON 863 and CON, as well as MON 863 and REF, for marbling score, LM area, or 12th rib fat thickness in both Exp. 2 and 3. Overall, performance was not negatively affected in the corn residue grazing or feedlot experiments, suggesting the corn rootworm-protected hybrid (event MON 863) is similar to conventional, nontransgenic corn grain and residues when utilized by beef cattle.

Reduction of radiotherapy-induced late complications in early breast cancer: the role of intensity-modulated radiation therapy and partial breast irradiation

Radiotherapy after conservation surgery has been proven to decrease local relapse and death from breast cancer, and is now firmly established in the management of early breast carcinoma. Currently, the challenge is to optimise the therapeutic ratio by minimising treatment-related morbidity, while maintaining or improving local control and survival. The second part of this review examines the role of two approaches: intensity-modulated radiation therapy (IMRT) and partial breast irradiation, as means of improving the therapeutic ratio. Discussion of IMRT includes both inverse- and forward-planned methods: the breast usually requires minimal modulation to improve dose homogeneity, and therefore lends itself to simpler forward-planned IMRT techniques; whereas inverse-planned IMRT may be useful in selected cases. There are many dosimetry studies reporting the superiority of IMRT over conventional breast radiotherapy, but there is still a paucity of clinical data regarding patient benefit from these techniques. A critical literature review of clinical partial breast radiotherapy studies focuses on the influence of irradiated breast volume, dose and fractionation, and patient selection on normal tissue side-effects and local control. Clinical reports of partial breast irradiation show several encouraging, but some concerning results about local recurrence rates. Therefore, mature results from randomised trials comparing partial breast irradiation with whole-breast radiotherapy are required. Accurate localisation of the tumour bed and application of appropriate clinical target volumes and planning target volumes are discussed in detail, as these concepts are fundamental for partial breast irradiation.

Effect of organic matter addition to the pen surface and pen cleaning frequency on nitrogen mass balance in open feedlots

Three finishing trials were conducted to determine the effects of dietary manipulation and management on N losses from open feedlots. In each experiment, 96 steers were assigned randomly to 12 nutrient balance pens. In Trial 1, calves were fed for 180 d during the winter/spring months; in Trial 2, yearlings were fed for 132 d in the summer. In Trials 1 and 2, N losses from pens were compared directly by adding OM to the pen surface or indirectly by feeding digestible ingredients designed to increase OM excretion. The dietary treatment (BRAN) included 30% corn bran (DM basis) replacing dry-rolled corn. Pens where OM was directly added received sawdust applications (SAWDUST) at a rate to match OM excretion from the BRAN diet. These two treatments were compared with a conventional, 75% dry-rolled corn diet (CON). Because CON and SAWDUST diets were identical, performance for both treatments was similar during Trials 1 and 2. The BRAN diet decreased (P < 0.10) gain efficiency during Trials 1 and 2 by 9.5% relative to CON. Fecal N excretion was greater (P < 0.01) for calves and yearlings when BRAN was fed compared with CON. Adding OM to the pen surface increased (P < 0.01) the amount of N in manure removed from pens and reduced (P < 0.10) N losses in Trial 1. Nitrogen losses were not significantly different among treatments in Trial 2. In Trial 3, calves were fed for 166 d during the winter/spring months. A 2 x 2 factorial design was used to evaluate pen cleaning frequency and diets similar to CON and BRAN. Pens were either cleaned monthly or once at the end of the feeding period. Daily DMI was greater (P = 0.01) and ADG was lower (P < 0.01) when cattle were fed BRAN compared with CON. Responses from all three trials indicate a negative effect of BRAN on gain efficiency. Dietary treatment and cleaning frequency interacted for N balance in the feedlot. Nitrogen losses decreased and manure N increased (P < 0.10) for cattle fed BRAN compared with CON when pens were cleaned monthly. Feeding BRAN did not affect total manure N, but resulted in higher N losses when pens were cleaned only once. For all trials, BRAN increased the amount of N remaining in composted manure. Adding OM to pen surfaces and/or cleaning pens more frequently may decrease N losses from open feedlot pens and from compost, although responses seem influenced by ambient temperature or season.

Reduction of radiotherapy-induced late complications in early breast cancer: the role of intensity-modulated radiation therapy and partial breast irradiation

Radiotherapy after conservation surgery has been proven to decrease local relapse and death from breast cancer, and is now firmly established in the management of early breast carcinoma. Currently, the challenge is to minimise the morbidity caused by this treatment without losing its efficacy. This review will be divided into two parts, with Part I focusing on the radiation factors contributing to late normal tissue complications after radiotherapy for early breast cancer. Three major normal tissue side-effects will be discussed: cosmetic outcome, cardiac complications and pulmonary side-effects.

A novel continuous infusional 5-fluorouracil-based chemotherapy regimen compared with conventional chemotherapy in theneo-adjuvant treatment of early breast cancer: 5 year results of the TOPIC trial

BACKGROUND

To compare the efficacy of continuous infusional 5-fluorouracil (5-FU)-based chemotherapy against conventional bolus chemotherapy in the preoperative treatment of patients with large operable early breast cancer.

PATIENTS AND METHODS

Four hundred and twenty-six women with histologically proven 3 cm invasive early breast cancer were randomised to receive pre-operative infusional 5-FU 200 mg/m(2) by daily 24 h continuous infusion via a Hickman line for 18 weeks with epirubicin 60 mg/m(2) intravenous (i.v.) bolus on day 1 and cisplatin 60 mg/m(2) i.v. bolus on day 1, both repeating 3-weekly (infusional ECisF), or conventional bolus doxorubicin 60 mg/m(2) i.v. on day 1 and cyclophosphamide 600 mg/m(2) i.v. on day 1, both repeating 3-weekly (AC), both schedules for six courses. Patients subsequently had local therapy (surgery or radiotherapy or both) and tamoxifen 20 mg orally daily as appropriate.

RESULTS

The 5 year results for AC and infusional ECisF, respectively, were as follows: overall response, 75% and 77%; complete clinical remission, 31% and 34%; pathological complete remission (pathCR), 16% for both; and pathCR with residual ductal carcinoma in situ (DCIS), 25% and 24%. Mastectomy rates were 37% and 34%, respectively. Five-year overall survival was 74% for AC and 82% for infusional ECisF (hazard ratio 0.76, 95% confidence interval 0.51-1.13; P = 0.18). Both treatments were well tolerated. Grade III/IV lethargy, vomiting, alopecia and plantar-palmar erythema were significantly greater for infusional ECisF; grade III/IV leucopenia was significantly greater for AC.

CONCLUSIONS

Preoperative continuous infusional 5-FU-based chemotherapy is no more active than conventional AC for early breast cancer; with a median 5 year follow-up, the infusion-based schedule shows a non-significant trend towards improved survival.

Undegradable intake protein supplementation of compensating spring-born steers and summer-born steers during summer grazing

Three trials were conducted to determine the effects of previous winter gain (Trials 1 and 3) and age of calf (Trials 1 and 2) on response to undegradable intake protein (UIP) supplementation during summer grazing. In Trial 1, 48 spring-born steers (243 kg) were used in a 4 x 2 factorial arrangement. Steers were wintered at four rates of gain: 0.65 (FAST), 0.24 (SLOW), 0.38 (S/F), and 0.38 (F/S) kg/d. The intermediate rates of gain (S/F and F/S) were created by switching steers from slow to fast or fast to slow midway through the wintering period. Following winter treatments, steers were assigned to one of two summer treatments: supplemented (S) or nonsupplemented (NS). In Trial 2, 32 summer-born steers were wintered at an ADG of 0.25 kg/d and allotted to the same summer treatments as Trial 1. The supplement was formulated to supply 200 g/d of UIP. Steers from both trials grazed upland Sandhills range from May to September 1998. In Trial 3, 49 spring-born steers (228 kg) were used in a 2 x 7 factorial arrangement of treatments. Steers were wintered at two rates of gain, 0.71 (FAST) and 0.24 kg/d (SLOW) and then assigned randomly to one of six levels of UIP supplementation or an energy control. Protein supplements were formulated to deliver 75, 112.5, 150, 187.5, 225, or 262.5 g/d of UIP. Sources of UIP for all trials were treated soybean meal and feather meal. In Trial 1, there were no (P > 0.05) winter by summer treatment interactions, and UIP supplementation increased (P = 0.0001) pasture gains over NS steers. In Trial 2, supplementation increased (P = 0.001) pasture ADG of summer-born steers by 0.15 kg/d compared with NS steers. In Trial 3, a winter gain by UIP supplementation interaction was observed (P = 0.09). Gain of FAST steers responded quadratically (P = 0.09) across UIP levels, with the maximum gain occurring at the 150 g/d UIP level. The SLOW steers responded linearly (P = 0.02) to increasing UIP levels; however, the response was negative. Levels of UIP above 150 g/d reduced steers gains; therefore, the data were reanalyzed excluding these levels. These new analyses showed that FAST steers responded linearly (P = 0.08; 0.2 kg/d) to increasing UIP, whereas the SLOW steers had no response to UIP. In Trials 1 and 3, SLOW steers experienced compensatory gain and had higher gains overall. We concluded that previous winter gain affected the response to UIP supplementation with the FAST winter gain group having a greater response.

Relationship between psychological well-being and lung health status in patients with bronchiectasis

Patients with bronchiectasis often complain of abnormal tiredness, difficulty in concentrating or low spirits. This study was carried out to examine levels of anxiety and depression in bronchiectasis and their relationship with other measures of lung health. One hundred and eleven patients with bronchiectasis determined by high-resolution computed tomography (CT) scan were studied using a range of physiological and psychological outcome measures. Patients completed anxiety and depression, health status (quality of life), fatigue and dypnoea questionnaires. Lung function was measured and exercise capacity was assessed using a shuttle walk test. Anxiety and depression scores formed a continuum. Moderate-severe anxiety was more frequent than equivalent levels of depression (17 vs 9% of patients). Anxiety and depression scores were associated with perceived health status (r=0.33 and 0.55). Neither anxiety nor depression was associated with the extent of bronchiectasis on CT scan. Depression was correlated with breathlessness and exercise performance (r=0.33 and 0.40), but anxiety was not. The correlation between depression and exercise performance was not simply due to the influence of somatic items in the depression questionnaire. We conclude that anxiety and depression are quite common in bronchiectasis in that 34% of patients had elevated scores for anxiety depression or both. The non-somatic components of depression were linked to dyspnoea and exercise performance, but anxiety was only related to perceived health. Therefore, treatment aimed at reducing symptoms and improving exercise capacity will not reduce levels of anxiety which need alternative therapy.

Effect of corn processing on starch digestion and bacterial crude protein flow in finishing cattle

Six ruminally and duodenally cannulated yearling steers (523 kg) were used in a replicated 3 x 3 Latin square design experiment to study the effects of corn processing on nutrient digestion, bacterial CP production, and ruminal fermentation. Dietary treatments consisted of 90% concentrate diets that were based on dry-rolled (DRC), high-moisture (HMC), or steam-flaked (SFC) corn. Each diet contained 2.0% urea (DM basis) as the sole source of supplemental nitrogen. Each period lasted 17 d, with d 1 through 14 for diet adaptation and d 15 through 17 for fecal, duodenal, and ruminal sampling. Dry matter and OM intakes were similar for DRC and SFC but were approximately 15% higher (P < 0.05) for HMC. True ruminal OM digestibilities were 18 and 10% greater (P < 0.05) for HMC than for DRC or SFC, respectively. Ruminal starch digestibilities were similar between HMC and SFC and were approximately 19% greater (P < 0.05) than DRC. Postruminal OM digestibility was similar among treatments; however, postruminal starch digestibility was 15% greater (P < 0.05) for SFC than for DRC or HMC, which were similar. Total-tract DM and OM digestibilities were similar between HMC and SFC and were 4% greater (P < 0.05) than DRC. Likewise, total-tract starch digestibilities were similar between HMC and SFC and were 3% greater (P < 0.05) than DRC. Bacterial CP flow to the duodenum was 29% greater (P < 0.05) for HMC than for DRC or SFC, which were similar. Bacterial N efficiencies were similar among treatments. Based on bacterial CP flow from the rumen, we estimate that dietary DIP requirements are approximately 12% higher for HMC-based diets than for DRC or SFC-based diets, which were similar.

Complete resolution of metastatic breast cancer by withdrawal of hormone replacement therapy

We report the case history of a patient with a known history of locally recurrent breast cancer, who developed metastatic disease while taking hormone replacement therapy (HRT). She underwent complete radiographic resolution of disease with no treatment other than cessation of the HRT.

A holistic approach to promoting success on NCLEX-RN

The nursing faculty at the State University of West Georgia views individuals as an integration of body-mind-spirit. Our program's commitment complements efforts to teach students to honor the body, mind, and spirit of patients. Within this framework, faculty recognize that factors other than nursing knowledge impact students' ability to pass NCLEX-RN. An intervention program was designed that incorporated these factors. "Preparation for Licensure" was implemented as a holistic nursing course to intervene with students' learning and testing needs. The purpose was to increase self-awareness, promote a positive attitude toward passing the NCLEX-RN, and provide specific strategies for test taking and stress reduction. Posttest raw scores and percent correct on the Mosby Assess Test were significantly higher (p < .05) than pretest scores. Qualitative analysis of journal data exploring the students' experience of participating in the course revealed three themes: Perfectionism, Self-Worth, and Consequences and Meaning of Failure.

Age and radiation response in glioblastoma multiforme

OBJECTIVE

Advanced age is a strong predictor of shorter survival in patients with glioblastoma multiforme (GM), especially for those who receive multimodality treatment. Radiographically assessed tumor response to external beam radiation therapy is an important prognostic factor in GM. We hypothesized that older GM patients might have more radioresistant tumors.

METHODS

We studied radiographically assessed response to external beam radiation treatment (five-level scale) in relation to age and other prognostic factors in a cohort of 301 GM patients treated on two prospective clinical protocols. A total of 223 patients (74%) were assessable for radiographically assessed radiation response. A proportional odds ordinal regression model was used for univariate and multivariate analysis.

RESULTS

Younger age (P = 0.006), higher Karnofsky Performance Scale score before radiotherapy (P = 0.027), and more extensive surgical resection (P = 0.028) predicted better radiation response in univariate analyses. Results were similar when clinical criteria were used to classify an additional 61 patients without radiographically assessed radiation response (stable versus progressive disease). In multivariate analyses, age and extent of resection were significant independent predictors of radiation response (P < 0.05); Karnofsky Performance Scale score was of borderline significance (P = 0.07).

CONCLUSION

Older GM patients are less likely to have good responses to postoperative external beam radiation therapy. Karnofsky Performance Scale score before radiation treatment and extent of surgical resection are additional predictors of radiographically assessed radiation response in GM.

A critical role for Dnmt1 and DNA methylation in T cell development, function, and survival

The role of DNA methylation and of the maintenance DNA methyltransferase Dnmt1 in the epigenetic regulation of developmental stage- and cell lineage-specific gene expression in vivo is uncertain. This is addressed here through the generation of mice in which Dnmt1 was inactivated by Cre/loxP-mediated deletion at sequential stages of T cell development. Deletion of Dnmt1 in early double-negative thymocytes led to impaired survival of TCRalphabeta(+) cells and the generation of atypical CD8(+)TCRgammadelta(+) cells. Deletion of Dnmt1 in double-positive thymocytes impaired activation-induced proliferation but differentially enhanced cytokine mRNA expression by naive peripheral T cells. We conclude that Dnmt1 and DNA methylation are required for the proper expression of certain genes that define fate and determine function in T cells.

Early pulmonary infection, inflammation, and clinical outcomes in infants with cystic fibrosis

A thorough understanding of the early natural history of cystic fibrosis (CF) lung disease is critical for the development of effective interventions in the youngest patients. We assessed the evolution of pulmonary infection, inflammation, and clinical course among 40 infants over a 2-year period through annual bronchoalveolar lavage (BAL) for culture and measurements of pro- and anti-inflammatory cytokines, semiannual infant pulmonary function testing, and quarterly clinical evaluations. Both the prevalence of CF pathogens and their density in BAL fluid increased with age. Infants had neutrophilic lower airway inflammation and elevated IL-8 concentrations independent of whether CF pathogens were recovered. Total leukocyte and neutrophil densities and IL-8 concentrations increased with density of CF pathogens in BAL fluid, whether the isolated organism was P. aeruginosa or another pathogen. IL-10 concentrations were similar in CF subjects and non-CF historical controls. Infants generally had suboptimal growth (low weight and height percentiles) and obstructive lung disease (decreased expiratory flows and air trapping). Subjects from whom CF pathogens were isolated at > 10(5) cfu/mL had the worst air trapping and lowest Brasfield chest X-ray scores. Our findings provide a foundation for future studies of early intervention in CF lung disease, including antimicrobial and anti-inflammatory therapy.

Vaccine safety--vaccine benefits: science and the public's perception

The development of cowpox vaccination by Jenner led to the development of immunology as a scientific discipline. The subsequent eradication of smallpox and the remarkable effects of other vaccines are among the most important contributions of biomedical science to human health. Today, the need for new vaccines has never been greater. However, in developed countries, the public's fear of vaccine-preventable diseases has waned, and awareness of potential adverse effects has increased, which is threatening vaccine acceptance. To further the control of disease by vaccination, we must develop safe and effective new vaccines to combat infectious diseases, and address the public's concerns.

Role of cyclin kinase inhibitor p21 in systemic autoimmunity

The cyclin kinase inhibitor protein p21 affects multiple processes relevant to the immune system, including cell cycle progression, replicative senescence, hemopoietic stem cell quiescence, and apoptosis. Therefore, malfunction of this protein may be a contributor to the pathogenesis of systemic autoimmunity. Here, we report that mixed background p21-deficient 129/Sv x C57BL/6 mice showed increased in vitro and in vivo T cell cycling and activation, moderate hypergammaglobulinemia and, at low penetrance, anti-chromatin autoantibodies. Homeostatic anti-self MHC/peptide ligand-induced proliferation of p21-deficient T cells was also enhanced. However, lymphoid organ enlargement was very mild, presumably due to increased apoptosis of the rapidly dividing cells. Moreover, the older p21-deficient mice had kidney pathology representing a similar, but slightly more advanced, state than that seen in the control mice. The timing and severity of the above serologic, cellular, and histologic manifestations in p21-deficient mice were unaffected by gender. Thus, p21 deficiency significantly enhances T cell activation and homeostatic proliferation, and can induce mild autoimmune manifestations at a low incidence without gender bias, but does not in itself generate the full spectrum of lupus-like disease.

Carrier-mediated enhancement of cognate T cell help: the basis for enhanced immunogenicity of meningococcal outer membrane protein polysaccharide conjugate vaccine

Haemophilus influenzae type b capsular polysaccharide (PRP) conjugate vaccines, which are thought to induce T cell-dependent antibody production, induce protective responses after a single dose in individuals under 15 months of age. However, multiple doses of these vaccines are required to induce protective antibody responses in infants, with the exception of PRP conjugated to meningococcal outer membrane proteins (OMPC), which does so after a single dose. The basis for this difference is not fully understood, although others have proposed that OMPC and porins, the major protein component of OMPC, act as adjuvants or mitogens. In this report OMPC is shown to enhance CD40 ligand-mediated, T cell-dependent antibody production in mice. This paralleled the induction by OMPC of CD86, CD80 and CD40 costimulatory molecules on human neonatal and murine B cells and of Th1 cytokines. Neither porins nor lipopolysaccharide fully reproduced the effects of OMPC. These studies indicate that OMPC acts both as carrier and adjuvant, and thereby enhances T cell-dependent antibody responses in human infants.

Diagnosis and management of pituitary abscess: a review of twenty-four cases

OBJECT

Pituitary abscess is a rare but serious intrasellar infection. To better determine the salient signs and symptoms that help in making the diagnosis, and to determine the most appropriate treatment, the authors reviewed their experience in a series of 24 patients treated at the University of California at San Francisco.

METHODS

Nine of the patients were female and 15 were male, and their mean age was 41.2 years (range 12-71 years). Surprisingly, most patients in our series presented with complaints and physical findings consistent with a pituitary mass, but rarely with evidence of a serious infection. Headache, endocrine abnormalities, and visual changes were the most common clinical indicators; fever, peripheral leukocytosis, and meningismus were present in 33% or fewer of the patients. Imaging tests demonstrated a pituitary mass in all patients, but the features evident on computerized tomography and magnetic resonance studies did not distinguish pituitary abscesses from other, more common intrasellar lesions. Because of the ambiguous clinical features and imaging findings, most abscesses were not diagnosed before treatment; rather, the diagnosis was made during surgical exploration of the sella turcica, when the surgeon encountered a cystic mass containing pus. There were only two deaths in this series (8.3%). Patients presenting with headache and visual changes noted improvement in almost all cases; patients with endocrine dysfunction generally did not recover normal pituitary function, but were easily treated with hormone replacement therapy.

CONCLUSIONS

Antibiotic therapy is suggested for patients who have symptoms of sepsis, or for patients in whom specific organisms are identified from cultures obtained during surgery. The transsphenoidal approach is recommended over open craniotomy for surgical drainage.

Current multimodality management of infectious intracranial aneurysms

OBJECTIVE

To implement an algorithm for and assess multimodality (medical, endovascular, and microsurgical) treatment of patients with infectious intracranial aneurysms.

METHODS

Twenty patients with 27 infectious aneurysms were treated during a 10-year period. Bacterial endocarditis was the most common cause (65%). Most aneurysms presented with rupture (75%), and the middle cerebral artery was the most common location (70%).

RESULTS

Five patients were treated endovascularly, with direct coiling for three patients and parent artery occlusion for two patients. Ten patients (15 aneurysms) were treated surgically, with 6 aneurysms being trapped/resected, 2 trapped/bypassed, 4 clipped, and 3 wrapped. Five patients were treated medically. Treatment-associated neurological morbidity was observed for two patients (10%), and two patients died (10%). Good outcomes were observed for 16 patients (80%).

CONCLUSION

Factors that guide management decisions for these patients include aneurysm rupture, hematomas with increased intracranial pressure, and the eloquence of brain tissue supplied by the parent artery. Patients with unruptured infectious aneurysms are initially treated medically, with antibiotics and serial angiography. Patients with ruptured aneurysms that are not associated with hematomas and that do not involve eloquent vascular territory are treated endovascularly. Patients with ruptured aneurysms are treated surgically when there is a hematoma or the risk of ischemic complications in eloquent territory. Therefore, endovascular therapy is the first option for patients in stable condition with ruptured aneurysms; surgical therapy is the first option for patients in unstable condition with ruptured aneurysms and the second option for patients in stable condition who experience failure of endovascular therapy. Medically treated patients with enlarging or dynamic unruptured aneurysms also require direct surgical or endovascular intervention. Favorable patient outcomes can be achieved with this multimodality management.

They took the time ... they started to care: stories of African-American nursing students in intercultural caring groups

Socially responsible nurse educators articulate the need to explore opportunities for nursing students to participate in experiences that promote caring and respect for diversity. This research illuminates the experiences of 10 African-American nursing students who participated in caring groups while enrolled in a predominantly White nursing education program. Although the meanings embedded in the African-American students' stories revealed commonalities with those of European-American and international students, there were also some differences. The authors maintained a critical social consciousness to analyze and describe these commonalities and differences. This article discusses the constitutive patterns and themes that emerged from the data and addresses implications for nursing education and practice.

Inactivation of Notch 1 in immature thymocytes does not perturb CD4 or CD8T cell development

Notch proteins influence cell-fate decisions in many developing systems. Several gain-of-function studies have suggested a critical role for Notch 1 signaling in CD4-CD8 lineage commitment, maturation and survival in the thymus. However, we show here that tissue-specific inactivation of the gene encoding Notch 1 in immature (CD25+CD44-)T cell precursors does not affect subsequent thymocyte development. Neither steady-state numbers nor the rate of production of CD4+ and CD8+ mature thymocytes is perturbed in the absence of Notch 1. In addition, Notch 1-deficient thymocytes are normally sensitive to spontaneous or glucocorticoid-induced apoptosis. In contrast to earlier reports, these data formally exclude an essential role for Notch 1 in CD4-CD8 lineage commitment, maturation or survival.

Intrasellar cavernous hemangioma. Case report

The authors present a rare entity, an intrasellar cavernous hemangioma that on neuroimages mimicked a nonfunctioning pituitary macroadenoma in a patient with a known orbital hemangioma. Such lesions can grow extraaxially within the dural sinuses, particularly the cavernous sinus, and present like tumors. A better understanding of the neuroimaging. clinical, and anatomical features of these lesions may prevent difficulties in management.

DNA hypomethylation perturbs the function and survival of CNS neurons in postnatal animals

DNA methyltransferase I (Dnmt1), the maintenance enzyme for DNA cytosine methylation, is expressed at high levels in the CNS during embryogenesis and after birth. Because embryos deficient for Dnmt1 die at gastrulation, the role of Dnmt1 in the development and function of the nervous system could not be studied by using this mutation. We therefore used the cre/loxP system to produce conditional mutants that lack Dnmt1 in neuroblasts of embryonic day 12 embryos or in postmitotic neurons of the postnatal animal. Conditional deletion of the Dnmt1 gene resulted in rapid depletion of Dnmt1 proteins, indicating that the enzyme in postmitotic neurons turns over quickly. Dnmt1 deficiency in postmitotic neurons neither affected levels of global DNA methylation nor influenced cell survival during postnatal life. In contrast, Dnmt1 deficiency in mitotic CNS precursor cells resulted in DNA hypomethylation in daughter cells. Whereas mutant embryos carrying 95% hypomethylated cells in the brain died immediately after birth because of respiratory distress, mosaic animals with 30% hypomethylated CNS cells were viable into adulthood. However, these mutant cells were eliminated quickly from the brain within 3 weeks of postnatal life. Thus, hypomethylated CNS neurons were impaired functionally and were selected against at postnatal stages.

Safer handling practice for nurses: a review of the literature

The lifting and handling of people is an integral part of nursing care and has been blamed for a high incidence of back injuries to nurses. Changes to nursing practice have been dictated by this level of injury following the passing of health and safety legislation in 1992. This review seeks to evaluate the growing body of research from a range of disciplines in order to establish an evidence base for the moving and handling of patients. It identifies that studies considering the impact of changes in practice on patient outcomes are lacking. The term 'safer handling practice' has been used by the author to indicate a new way of thinking in relation to moving and handling people in health and care settings. A definition of safer handling practice has been derived from the literature with concomitant implications for training. Using this body of knowledge alongside studies investigating mobility of older people, the literature was used deductively to ascertain that safer handling practice has the potential to influence positively the mobility of older people. The author suggests further research to be conducted in the field of safer handling practice.

Cutting edge: functional interactions between toll-like receptor (TLR) 2 and TLR1 or TLR6 in response to phenol-soluble modulin

Toll-like receptor (TLR) 2 and TLR4 play important roles in the early, innate immune response to microbial challenge. TLR2 is preferentially involved in the inflammatory response to lipoteichoic acid, lipopeptides, and glycans from a variety of microbes, whereas TLR4 is essential for a complete response to LPSs. We report here that TLR2 transduces the response to phenol-soluble modulin, a factor secreted by Staphylococcus epidermidis. The TLR2-mediated response to this modulin was enhanced by TLR6 but inhibited by TLR1, indicating a functional interaction between these receptors. We also demonstrate that a response to phenol-soluble modulin mediated by TLR2 and TLR6 was more refractory to inhibition by TLR1 than one mediated by TLR2 alone.

Phase III trial of accelerated hyperfractionation with or without difluromethylornithine (DFMO) versus standard fractionated radiotherapy with or without DFMO for newly diagnosed patients with glioblastoma multiforme

PURPOSE

To report the results of a prospective Phase III trial for patients with newly diagnosed glioblastoma multiforme (GBM), treated with either accelerated hyperfractionated irradiation with or without difluromethylornithine (DFMO) or standard fractionated irradiation with or without DFMO.

METHODS AND MATERIALS

Adult patients with newly diagnosed GBM were registered and randomized following surgery to one of 4 treatment arms: Arm A, accelerated hyperfractionation alone using 2 fractions a day of 1.6 Gy to a total dose of 70.4 Gy in 44 fractions; Arm B, accelerated hyperfractionation as above plus DFMO 1.8 gm/m2 by mouth every 8 h beginning one week before radiation until the last fraction was given; Arm C, single-fraction irradiation of 1.8 Gy/day to 59.4 Gy; Arm D, single-fraction irradiation as in Arm C plus DFMO given as in Arm B. Patients were followed for progression-free survival (PFS) and overall survival (OS), as well as for toxicity. Eligibility required histologically proven GBM, age > or =18, Karnofsky performance status (KPS) > or =60, and no prior chemotherapy or radiotherapy. Adjuvant chemotherapy was not used in this protocol.

RESULTS

A total of 231 eligible patients were enrolled. There were 95 men and 136 women with a median age of 57 years, and median KPS of 90. Extent of resection was total in 23, subtotal in 152, and biopsy only in 56 patients. The 4 arms were balanced with respect to age, KPS, and extent of resection. Times to event measurements are from date of diagnosis. Median OS and PFS were 40 and 19 weeks for Arm A; 42 and 22 weeks for Arm B; 37 and 16 weeks for Arm C; and 44 and 19 weeks for Arm D (p = 0.48 for survival; p = 0.32 for PFS). Comparison of the 2 arms treated with DFMO to the 2 arms without DFMO revealed no difference in OS (37 weeks vs. 42 weeks, p = 0.12) or PFS and thus no benefit to the use of DFMO. Comparison of the 2 standard fractionation arms to the 2 accelerated hyperfractionation arms also resulted in no difference in OS (42 weeks vs. 41 weeks, p = 0.75) or PFS, showing no benefit to accelerated hyperfractionated irradiation.

CONCLUSION

In this prospective Phase III study, no survival or PFS benefit was seen with accelerated hyperfractionated irradiation to 70.4 Gy, nor was any benefit seen with DFMO as a radiosensitizer. Standard fractionated irradiation to 59.4 Gy remains the treatment of choice for newly diagnosed patients with glioblastoma multiforme.

Role of CD28/CD80-86 and CD40/CD154 costimulatory interactions in host defense to primary herpes simplex virus infection

Dependence of the primary antiviral immune response on costimulatory interactions between CD28/CD80-86 and between CD40/CD154 (CD40 ligand) has been correlated with the extent of viral replication in two models of systemic infection, lymphocytic choriomeningitis virus and vesicular stomatitis virus. To determine the role of these costimulatory interactions in the context of an acute cytolytic, but locally replicating viral infection, herpes simplex virus (HSV) infection was assessed in mice that had the CD28/CD80-86 or CD40/CD154 interactions disrupted either genetically or with blocking reagents (CTLA4Ig and MR1, respectively). CTLA4Ig treatment greatly reduced paralysis-free survival during primary acute HSV infection. This reflected an almost total ablation of the anti-HSV CD4(+) and CD8(+) T-cell responses due to anergy and reduced cell numbers, respectively. Disruption of CD40/CD154 interactions impaired survival, but the effect was less severe than that observed in CTLA4Ig-treated mice, with reductions observed in the CD4(+) T-cell but not CD8(+) T-cell responses. These two costimulatory pathways functioned in part independently, since disruption of both further impaired survival. The dependence on these costimulatory interactions for the control of primary HSV infection may represent a more widespread paradigm for nonsystemic viruses, which have restricted sites of replication and which employ immunoevasive measures.

T cell expression cloning of a Mycobacterium tuberculosis gene encoding a protective antigen associated with the early control of infection

Infection of C57BL/6 mice with Mycobacterium tuberculosis results in the development of a progressive disease during the first 2 wk after challenge. Thereafter, the disease is controlled by the emergence of protective T cells. We have used this infection model in conjunction with direct T cell expression cloning to identify Ags involved with the early control of the disease. A protective M. tuberculosis-specific CD4 T cell line derived from mice at 3 wk postchallenge was used to directly screen an M. tuberculosis genomic expression library. This screen resulted in the identification of a genomic clone comprising two putative adjacent genes with predicted open reading frames of 10 and 41 kDa, MTB10 and MTB41, respectively (the products of Rv0916c and Rv0915c, respectively, in the TubercuList H37Rv database). MTB10 and MTB41 belong to the PE and PPE family of proteins recently identified to comprise 10% of the M. tuberculosis genome. Evaluation of the recombinant proteins revealed that MTB41, but not MTB10, is the Ag recognized by the cell line and by M. tuberculosis-sensitized human PBMC. Moreover, C57BL/6 mice immunized with MTB41 DNA developed both CD4- (predominantly Th1) and CD8-specific T cell responses to rMTB41 protein. More importantly, immunization of C57BL/6 mice with MTB41 DNA induced protection against infection with M. tuberculosis comparable to that induced by bacillus Calmette-Guérin. Thus, the use of a proven protective T cell line in conjunction with the T cell expression cloning approach resulted in the identification of a candidate Ag for a subunit vaccine against tuberculosis.

The repertoire for pattern recognition of pathogens by the innate immune system is defined by cooperation between toll-like receptors

Toll-like receptors (TLRs) have been shown to participate in the recognition of pathogens by the innate immune system, but it is not clear how a restricted family of receptors has the capacity to recognize the wide spectrum of TLR stimuli known to exist. We report here that two members of the TLR family, TLR2 and TLR6, together coordinate macrophage activation by Gram-positive bacteria and the yeast cell-wall particle, zymosan. TLR6 and TLR2 both are recruited to the macrophage phagosome, where they recognize peptidoglycan, a Gram-positive pathogen component. By contrast, TLR2 recognizes another component, bacterial lipopeptide, without TLR6. The requirement for TLR cooperation is supported by the finding that TLR2 needs a partner to activate tumor necrosis factor-alpha production in macrophages. Dimerization of the cytoplasmic domain of TLR2 does not induce tumor necrosis factor-alpha production in macrophages, whereas similar dimerization of the TLR4 cytoplasmic domain does. We show that the cytoplasmic domain of TLR2 can form functional pairs with TLR6 or TLR1, and this interaction leads to cytokine induction. Thus, the cytoplasmic tails of TLRs are not functionally equivalent, with certain TLRs requiring assembly into heteromeric complexes, whereas others are active as homomeric complexes. Finally, we show that TLR6, TLR2, and TLR1 are recruited to macrophage phagosomes that contain IgG-coated erythrocytes that do not display microbial components. The data suggest that TLRs sample the contents of the phagosome independent of the nature of the contents, and can establish a combinatorial repertoire to discriminate among the large number of pathogen-associated molecular patterns found in nature.

Membrane targeting properties of a herpesvirus tegument protein-retrovirus Gag chimera

The retroviral Gag protein is capable of directing the production and release of virus-like particles in the absence of all other viral components. Budding normally occurs after Gag is transported to the plasma membrane by its membrane-targeting and -binding (M) domain. In the Rous sarcoma virus (RSV) Gag protein, the M domain is contained within the first 86 amino acids. When M is deleted, membrane association and budding fail to occur. Budding is restored when M is replaced with foreign membrane-binding sequences, such as that of the Src oncoprotein. Moreover, the RSV M domain is capable of targeting heterologous proteins to the plasma membrane. Although the solution structure of the RSV M domain has been determined, the mechanism by which M specifically targets Gag to the plasma membrane rather than to one or more of the large number of internal membrane surfaces (e.g., the Golgi apparatus, endoplasmic reticulum, and nuclear, mitochondrial, or lysosomal membranes) is unknown. To further investigate the requirements for targeting proteins to discrete cellular locations, we have replaced the M domain of RSV with the product of the unique long region 11 (U(L)11) gene of herpes simplex virus type 1. This 96-amino-acid myristylated protein is thought to be involved in virion transport and envelopment at internal membrane sites. When the first 100 amino acids of RSV Gag (including the M domain) were replaced by the entire UL11 sequence, the chimeric protein localized at and budded into the Golgi apparatus rather than being targeted to the plasma membrane. Myristate was found to be required for this specific targeting, as were the first 49 amino acids of UL11, which contain an acidic cluster motif. In addition to shedding new light on UL11, these experiments demonstrate that RSV Gag can be directed to internal cellular membranes and suggest that regions outside of the M domain do not contain a dominant plasma membrane-targeting motif.