Active unfolding of precursor proteins during mitochondrial protein import

Precursor proteins made in the cytoplasm must be in an unfolded conformation during import into mitochondria. Some precursor proteins have tightly folded domains but are imported faster than they unfold spontaneously, implying that mitochondria can unfold proteins. We measured the import rates of artificial precursors containing presequences of varying length fused to either mouse dihydrofolate reductase or bacterial barnase, and found that unfolding of a precursor at the mitochondrial surface is dramatically accelerated when its presequence is long enough to span both membranes and to interact with mhsp70 in the mitochondrial matrix. If the presequence is too short, import is slow but can be strongly accelerated by urea-induced unfolding, suggesting that import of these 'short' precursors is limited by spontaneous unfolding at the mitochondrial surface. With precursors that have sufficiently long presequences, unfolding by the inner membrane import machinery can be orders of magnitude faster than spontaneous unfolding, suggesting that mhsp70 can act as an ATP-driven force-generating motor during protein import.     

Determination of synthetic phenolic antioxidants in food items using reversed-phase HPLC

A HPLC with gradient elution method for the determination of the synthetic phenolic antioxidants (SPAs) propyl gallate (PG), tertiary butyl hydroquinone (TBHQ), butylated hydroxyanisole (BHA), and butylated hydroxytoluene (BHT) in food items is described. A C18 column served as the stationary phase; the gradient elution was formed by acetonitrile and water:acetic acid (1%). The UV detector was set at 280 nm. Under the recommended conditions, separation of the four SPAs was achieved in less than 8 min. Analytical characteristics of the HPLC method such as limit of detection, linear range, and reproducibility were evaluated. Extraction parameters were optimized for the recoveries of the SPAs in different types of food items (cooking oil, margarine and butter, and cheese). Before the HPLC separation, the SPAs were extracted with methanol/acetonitrile (1:1, v/v) and were subjected to vortex/ultrasonic treatment. The extracts were next kept in a freezer (∼2 h) to precipitate co-extracted components. Recoveries of the SPAs when spiked to cooking oil, margarine, butter and cheese at 50 and 200 mg l⁻¹ were in the ranges 93.3–108.3% for PG, 85.3–108.3% for TBHQ, 96.7–101.2% for BHA and 73.9–94.6% for BHT. The method was applied to the determination of SPAs in 38 food items (16 cooking oils, ten margarine, six butter and six cheese samples). The levels of SPAs in positive samples are all below the legal limits of Malaysia.     

Determination of aflatoxins in animal feeds by HPLC with multifunctional column clean-up

A reversed-phase HPLC method with fluorescence detection for the determination of the aflatoxins B1, B2, G1 and G2 in 42 animal feeds, comprising corn (16), soya bean meal (8), mixed meal (13), sunflower, wheat, canola, palm kernel, copra meals (1 each) was carried out. The samples were first extracted using acetonitrile:water (9:1), and was further cleaned-up using a multifunctional column. Optimum conditions for the extraction and chromatographic separation were investigated. By adopting an isocratic chromatographic system using a mobile phase comprising acetonitrile:methanol:water (8:27:65, v/v/v), the separation of the four aflatoxins was possible within 30 min. Recoveries for aflatoxins B1, B2, G1 and G2 were 98 ± 0.7%, 95 ± 1.0%, 94 ± 3.6% and 97 ± 4.3%, respectively. The results show that eight samples (19%) were contaminated with aflatoxins, ranging from 6.5 to 101.9 ng g^?1. Total aflatoxin levels in three samples exceed the legal limits of many countries of 20 ng g^?1.     

High levels of anticardiolipin antibodies in patients with abnormal embryo morphology who attended an in vitro fertilization program

Although it is unlikely that the legislative endeavors of 1996 and 1997 relating to the health care industry will be matched in 1998, implementing regulations of the Balanced Budget Act and the Health Insurance Portability and Accountability Act will predicate the successes or shortcomings of these new laws in 1998. It is important that NPs stay in close contact with their state legislators and Medicaid officers responsible for implementing the SCHIP. NPs should also closely track efforts at the Federal level to ensure inclusion of non-physician providers in legislation that is important to NPs, such as bans on "gag" clauses--a protection that should include all health care providers.     

Effect of human recombinant erythropoietin therapy on panel reactive antibodies in chronic dialysis patients

To examine whether recombinant human erythropoietin (rhEPO) therapy results in decreased presensitization to foreign HLA antigens, we retrospectively analyzed data from 64 of 200 patients treated in a university hospital dialysis center between 1985 and 1995 who had undergone routine panel reactive antibody (PRA%) screening. Though a significant decrease in the annual frequency of highly sensitized patients over the years was noted, 16 patients followed for 27.1 +/- 3.7 months after initiation of rhEPO therapy until transplantation or blood transfusion showed no significant overall decrease in PRA%. Six highly presensitized patients had moderate but significant overall decrease in PRA%. However, in three of these patients the PRA% was unchanged and in the other three patients the PRA% remained over 50%. Thus rhEPO therapy reduced the incidence of highly presensitized patients, but previously presensitized patients remained presensitized. We conclude that removal of transfusional stimulation of lymphocytotoxic antibody production does not appear to benefit previously presensitized patients, possibly due to the maintenance of B-lymphocyte clonal expansion by unknown factors, or even by rhEPO itself.     

Effects of dietary amylase and sucrose on productivity of cows fed low-starch diets

Recent studies have observed positive effects of both sucrose and exogenous amylase on the productivity of dairy cattle. Our objective was to evaluate direct effects and interactions of amylase and sucrose on dry matter intake (DMI), milk production, and milk components. Forty-eight multiparous Holstein cows between 70 and 130 d in milk were randomly assigned to each of 4 pens (12 cows/pen). Pens were randomly assigned to treatment sequence in a 4 × 4 Latin square design, balanced for carryover effects. Treatment periods were 28 d, with 24 d for diet adaptation and 4 d for sample and data collection. The treatments were a control diet (36% NDF and 21% starch), the control diet with amylase [0.5 g/kg of DM; Ronozyme RumiStar 600 (CT); DSM Nutritional Products Ltd., Basel, Switzerland], a diet with sucrose replacing corn grain at 2% of DM, and the sucrose diet with amylase (0.5 g/kg of DM). All data were analyzed with mixed models, including the fixed effects of sugar, amylase, and their interaction, and the random effects of period and pen. Milk data included the random effects of cow nested within pen and pen × period to provide the error term for the pen-level analysis. Dry matter intake was not affected by treatments. Milk yield and milk composition were not altered by the inclusion of sucrose or amylase; however, a tendency for an amylase × sucrose interaction was observed for milk protein content, reflecting slightly lower milk protein concentrations for amylase and sucrose treatments (3.00 and 2.99 ± 0.03%) compared with the control and amylase + sucrose treatments (3.02 and 3.03 ± 0.03%). Solids-corrected and fat-corrected milk yields were not significantly altered by treatment, although the direct effect of amylase approached significance for both variables, suggesting possible small increases with amylase supplementation (~0.5 kg/d). Feed efficiency (energy-corrected milk divided by dry matter intake) numerically increased with either amylase (1.57 ± 0.12) or sucrose (1.60 ± 0.12) treatment, but the combination of the 2 resulted in feed efficiency similar to the control treatment (both 1.50 ± 0.12). The inclusion of amylase or sucrose did not affect DMI, productivity, or feed efficiency in mid-lactation cows fed low-starch, high-fiber diets.     

Influence of the combination of 25-hydroxyvitamin D3 and a diet negative in cation-anion difference on peripartal calcium homeostasis of dairy cows

Around parturition, many dairy cows experience varying degrees of hypocalcemia, which increases the incidence of several diseases in early lactation. In the current study, an established concept of feeding a diet negative in cation-anion difference (DCAD) was combined with oral supplementation of 25-hydroxyvitamin D(3) (25-OHD(3)) from d 270 of gestation until parturition. Fifty-six dairy cows were divided into 2 feeding groups (low DCAD and control). Fourteen animals of each group received a daily dosage of 3mg of 25-OHD(3). From the beginning of the treatment to d 10 after parturition, plasma samples for analysis of 25-OHD(3), 1,25-dihydroxyvitamin D(3), parathyroid hormone (PTH), Ca(2+), phosphate, the bone resorption marker CrossLaps, and osteocalcin were collected every other day, at calving, and at 6, 12, and 24h after calving. Urine samples for determination of macrominerals and measures of acid-base status were collected on d 6 of treatment and on d 6 after calving. The induction of a compensated metabolic acidosis by the animals on the DCAD diet could be demonstrated by decreased urinary pH. A linear correlation between treatment duration and the plasma concentration of 25-OHD(3) indicated effective absorption of 25-OHD(3) in supplemented animals. The mean plasma concentrations of Ca(2+) from d -4 prepartum to d 4 postpartum were significantly higher in animals treated with the combination of the low DCAD diet and 25-OHD(3) supplementation (1.24±0.02 mmol/mL) compared with the 3 other groups (low DCAD: 1.17±0.02 mmol/mL; control diet plus 25-OHD(3): 1.16±0.02 mmol/mL; control diet: 1.18±0.02 mmol/mL). We postulate that the increased tissue responsiveness to parathyroid hormone induced by the low DCAD is crucial for the observed positive effects of the 25-OHD(3) treatment.     

Development of copper matrix composite reinforced with FeAl particles produced by combustion synthesis

This work focuses on the synthesis of FeAl intermetallic compound by combustion synthesis (SHS process) and its inclusion as dispersoids in a copper matrix to develop a metal matrix composite (MMC) by sintering. In the first step, FeAl compound was produced by the sintering of Fe-50 at.%Al at 1100 °C. Then, after grinding and mixing with copper powder, it was sintered in solid phase and liquid phase to obtain a metal matrix composite. The Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy (SEM and EDS-X) analysis showed that copper diffuses in the microporosity of the FeAl particles and leaves porosity in the matrix. FeAl was milled by high energy to reduce the size of particles. It was then co-milled with copper to coat its particles in order to achieve higher density. The results showed that copper coats the FeAl particles which become finer and less porous. However, a low porosity persists in the matrix after sintering.     

Ni‐Coated SiC Particles: Synthesis and Densification

The mechanofusion process, a dry particle coating route, has been successfully applied to coat micrometric SiC particles with submicrometric Ni filaments. In a first step, the mechanofusion parameters were optimized to form a continuous Ni coating onto SiC particles. In a second step, the Ni‐coated SiC particles were sintered by hot isostatic pressing. The temperature and pressure cycles were determined to ensure a good densification of the material. Such a densification process leads to the formation of a δ‐Ni₂Si bilayer at the SiC/Ni interface; the inner δ‐Ni₂Si layer in contact with SiC being more rich in carbon than the one in contact with the matrix. From X‐ray diffraction, wavelength‐dispersive X‐ray spectrometry and scanning electron microscopy characterizations, a mechanism is proposed to explain the microstructure of the end‐product.     

A review on biomass‐based hydrogen production and potential applications

In this paper, a detailed review is presented to discuss biomass‐based hydrogen production systems and their applications. Some optimum hydrogen production and operating conditions are studied through a comprehensive sensitivity analysis on the hydrogen yield from steam biomass gasification. In addition, a hybrid system, which combines a biomass‐based hydrogen production system and a solid oxide fuel cell unit is considered for performance assessment. A comparative thermodynamic study also is undertaken to investigate various operational aspects through energy and exergy efficiencies. The results of this study show that there are various key parameters affecting the hydrogen production process and system performance. They also indicate that it is possible to increase the hydrogen yield from 70 to 107 g H₂ per kg of sawdust wood. By studying the energy and exergy efficiencies, the performance assessment shows the potential to produce hydrogen from steam biomass gasification. The study further reveals a strong potential of this system as it utilizes steam biomass gasification for hydrogen production. To evaluate the system performance, the efficiencies are calculated at particular pressures, temperatures, current densities, and fuel utilization factors. It is found that there is a strong potential in the gasification temperature range 1023–1423 K to increase energy efficiency with a hydrogen yield from 45 to 55% and the exergy efficiency with hydrogen yield from 22 to 32%, respectively, whereas the exergy efficiency of electricity production decreases from 56 to 49.4%. Hydrogen production by steam sawdust gasification appears to be an ultimate option for hydrogen production based on the parametric studies and performance assessments that were carried out through energy and exergy efficiencies. Finally, the system integration is an attractive option for better performance. Copyright © 2012 John Wiley & Sons, Ltd.