Extraction of the ^{235}U and ^{239}Pu Antineutrino Spectra at Daya Bay

This Letter reports the first extraction of individual antineutrino spectra from ^{235}U and ^{239}Pu fission and an improved measurement of the prompt energy spectrum of reactor antineutrinos at Daya Bay. The analysis uses 3.5×10^{6} inverse beta-decay candidates in four near antineutrino detectors in 1958 days. The individual antineutrino spectra of the two dominant isotopes, ^{235}U and ^{239}Pu, are extracted using the evolution of the prompt spectrum as a function of the isotope fission fractions. In the energy window of 4-6 MeV, a 7% (9%) excess of events is observed for the ^{235}U (^{239}Pu) spectrum compared with the normalized Huber-Mueller model prediction. The significance of discrepancy is 4.0σ for ^{235}U spectral shape compared with the Huber-Mueller model prediction. The shape of the measured inverse beta-decay prompt energy spectrum disagrees with the prediction of the Huber-Mueller model at 5.3σ. In the energy range of 4-6 MeV, a maximal local discrepancy of 6.3σ is observed.

Measurement of the Electron Antineutrino Oscillation with 1958 Days of Operation at Daya Bay

We report a measurement of electron antineutrino oscillation from the Daya Bay Reactor Neutrino Experiment with nearly 4 million reactor ν[over ¯]_{e} inverse β decay candidates observed over 1958 days of data collection. The installation of a flash analog-to-digital converter readout system and a special calibration campaign using different source enclosures reduce uncertainties in the absolute energy calibration to less than 0.5% for visible energies larger than 2 MeV. The uncertainty in the cosmogenic ^{9}Li and ^{8}He background is reduced from 45% to 30% in the near detectors. A detailed investigation of the spent nuclear fuel history improves its uncertainty from 100% to 30%. Analysis of the relative ν[over ¯]_{e} rates and energy spectra among detectors yields sin^{2}2θ_{13}=0.0856±0.0029 and Δm_{32}^{2}=(2.471_{-0.070}^{+0.068})×10^{-3}  eV^{2} assuming the normal hierarchy, and Δm_{32}^{2}=-(2.575_{-0.070}^{+0.068})×10^{-3}  eV^{2} assuming the inverted hierarchy.

Alterations in skeletal muscle structure are minimized with steroid withdrawal after renal transplantation

BACKGROUND

Limitations in exercise capacity in kidney transplant recipients are thought to result in part from changes in muscle structure and function associated with immunosuppression therapy.

METHODS

We compared the percent distribution of skeletal muscle fiber types, cross-sectional areas, and ultrastructural morphologies in kidney transplant recipients treated with standard prednisone maintenance therapy (n=21) to those undergoing rapid withdrawal of prednisone using Simulect (interleukin 2 receptor inhibitor) (n=13). Skeletal muscle biopsy specimens from the vastus lateralis were analyzed at 3 and 12 months after transplantation and compared with sedentary controls (n=15).

RESULTS

Compared with the control group, the group receiving prednisone maintenance therapy had a significantly lower percentage of type I fibers and a higher percentage of type IIB/x fibers, evident at 3 and 12 months. Fiber type distribution in patients withdrawn from prednisone did not differ from controls. In patients withdrawn from prednisone, the cross-sectional areas of type I and IIA fibers were lower and the area of type IIB/x fibers was higher compared with controls. Likewise, ultrastructural studies revealed reduced volume densities of myofibrils and higher densities of interfibrillar and subsarcolemmal mitochondria. At 12 months there were no ultrastructural differences between the patients withdrawn from prednisone and controls.

CONCLUSIONS

We conclude that prednisone maintenance therapy contributes to the lower exercise capacity by altering the ratio of type I to type IIB/x fibers and by reducing myofilament density. The increase in mitochondria in patients receiving prednisone may reflect a switch from carbohydrate to lipid metabolism resulting from the glucocorticoid therapy.

Health-related fitness and quality of life following steroid withdrawal in renal transplant recipients

BACKGROUND

Exercise capacity increases significantly soon after transplantation; however, over time it does not further improve and patients remain low compared to normal levels. The limitations to exercise following transplantation have not been identified, but may be related to immunosuppression therapy regimens that include prednisone.

METHODS

We studied health-related fitness measures (cardiorespiratory fitness, muscle strength, and body composition) and quality of life in renal transplant recipients randomized into two groups: those using standard maintenance immunosuppression, including prednisone therapy (N = 14); and those undergoing rapid withdrawal of steroids using Simulect[interleukin-2 (IL-2) receptor inhibitor] (N = 9). Testing was done at 3 and 12 months following transplant and the 12-month data were compared to 15 normal sedentary controls.

RESULTS

Compared to those maintained on steroids, the steroid withdrawal group showed greater gains in VO2peak (P = 0.05) and quadriceps peak torque (P = 0.05) and greater gains in the vitality score and the Physical Composite Scale on the SF-36 questionnaire (P < 0.05). At 1 year, all patients had significantly lower exercise capacity compared to the sedentary controls (P = 0.01). No differences were observed in body composition, with both patient groups increasing in body weight (primarily body fat) over time. At 12 months, all patients were not different in body fat percentage compared to the sedentary controls.

CONCLUSION

We conclude that prednisone is not the cause for increased body fat following transplantation; however, it may contribute to lower spontaneous improvements in exercise capacity possibly by limiting increases in muscle strength. The low exercise capacity in all transplant recipients studied at 1 year suggests a need for exercise training to optimize physical functioning following transplant.

Age effect on transcript levels and synthesis rate of muscle MHC and response to resistance exercise

Experimental evidence indicates that a lower synthesis rate of muscle contractile protein myosin heavy chain (MHC) occurs in age-related muscle wasting and weakness. To determine the molecular mechanism of this lower synthesis of MHC, we measured transcript levels of isoforms of MHC (MHCI, MHCIIa, and MHCIIx) in muscle biopsy samples of 7 young (20-27 yr), 12 middle-aged (47-60 yr), and 14 older (>65 yr) people. We further determined the effect of 3 mo of resistance exercise training (exercise) vs. nonintervention (control) on transcript levels of MHC isoforms on these subjects and the fractional synthesis rate (FSR) of MHC in 39 people aged 46-79 yr. MHCI mRNA levels did not significantly change with age, but MHCIIa decreased 38% (P < 0.05) from young to middle age and further decreased 50% (P < 0.05) from middle to old age. MHCIIx decreased 84% (P < 0.05) from young to middle age and 48% from middle to old age (P < 0.05). Exercise increased FSR of MHC by 47% (P < 0.01) and mixed muscle protein by 56% (P < 0.05). Exercise training results in an increase (85%) in transcript levels of MHCI and a decrease in the transcript levels of MHCIIa and MHCIIx. In conclusion, an age-related lowering of the transcript levels of MHCIIa and MHCIIx is not reversed by exercise, whereas exercise results in a higher synthesis rate of MHC in association with an increase in MHCI isoform transcript levels.

Reduced synthesis of muscle proteins in chronic renal failure

Muscle wasting and weakness occur frequently in patients with chronic renal failure. The mechanism(s) by which these abnormalities occur is unclear. We hypothesized that such findings were due to defective muscle protein synthesis. We measured synthetic rates of mixed muscle proteins, myosin heavy chain, and mitochondrial proteins in serial muscle biopsy samples during a continuous infusion of L[1-(13)C]leucine from 12 patients with chronic renal failure and 10 healthy control subjects under identical study conditions. Patients with chronic renal failure have significantly lower synthetic rates of mixed muscle proteins and myosin heavy chain (27 and 37% reductions, respectively, P < 0.05 and P < 0.02). Significant declines in the synthetic rates of muscle mitochondrial protein (27%) (P < 0.05), muscle cytochrome c-oxidase activity (42%) (P < 0.007), and citrate synthase (27%) (P < 0.007) were also observed in patients with chronic renal failure. The synthetic rates of muscle proteins and activity of mitochondrial enzymes were negatively correlated to the severity of renal failure. These results indicate that in chronic renal failure there is a decrease in the synthesis of muscle contractile and mitochondrial proteins and a decrease in muscle mitochondrial oxidative enzymes. Reduced synthetic rate of several muscle proteins is the likely biochemical basis of muscle loss and muscle weakness in people with chronic renal failure.

Cardiopulmonary arrest in pregnancy: successful resuscitation of mother and infant following immediate caesarean section in labour ward

Our patient experienced cardiopulmonary arrest secondary to profound hypotension and was unable to be resuscitated with external cardiac massage and assisted ventilation. This case demonstrates the need for continued vigilance by medical and nursing staff when epidural anaesthesia is being established. Resuscitation equipment should be available in the labour ward as cardiopulmonary resuscitation and immediate Caesarean section can be lifesaving in the event of a cardiopulmonary arrest.

Smoking in pregnancy: relevance of maternal screening tests on fetal outcome

A number of laboratory parameters were estimated in 54 pregnant women in order to assess whether changes induced by smoking could reflect weight gain in the fetus. There was a significant correlation between maternal weight gain index, oestriol levels, antithrombin III levels and reticulocyte synthesis with infant and placental weight gain. One or more of these tests was found abnormal in 27% of normal pregnant patients, 72% of light smokers, and 89% of heavy smokers. Several other parameters were found to be significantly altered in smoking compared to non-smoking pregnant patients; however, these bore no relationship to infant and placental parameters. These studies indicate that laboratory assessment of a number of maternal parameters could be of some value in determining the likelihood of depressed weight gain by infants of smoking mothers.

Contraception in the puerperium

Choice of contraception in the puerperium is complicated by the normal factors of lactation, involuting uterus and emotional lability. The individual's previous contraceptive experience is important, and new agents and techniques change current practices. In the puerperium, failure for IUDs is increased, and tubal ligation has more hazards. During lactation the standard combined oral contraceptives are not advised, but the microdose progestagen-only pill may be a most satisfactory agent-changing to more routine methods when menstruation starts. In a population of normal women, progestagen-only therapy may show about a 25 per cent dropout because of an unacceptable bleeding pattern, but there is a small group of women who appear to be well suited by this form of oral contraception.