蚕氨基酸代谢的研究——家蚕与蓖麻蚕的氨基酸和形成甘氨酸、丙氨酸的酶系比较及酮丙二酸的脱羧作用

家蚕(Bombyx mori L.)与蓖麻蚕(Samia,ricini B)的丝蛋白氨基酸含量差异甚为显著;家蚕丝含量最多的为甘氨酸(42.8％),其次为丙氨酸(32.4％);而蓖麻蚕丝则以两氨酸含量为最高(50.5％),其次为甘氨酸(27.8％)(Kirimuru等,1962)。为了阐明丝蛋白主要氨基酸的形成机制,我们曾报道了这两种蚕丝腺中,自L-天门冬氨酸与α-酮戊二酸形成丙氨酸的机制(许延森等,1964a);体液乙醛酸及丙酮酸与丝蛋白相应氨基酸的含量之     

Clinical Impact of Speed Variability to Identify Ultramarathon Runners at Risk for Acute Kidney Injury

BackgroundUltramarathon is a high endurance exercise associated with a wide range of exercise-related problems, such as acute kidney injury (AKI). Early recognition of individuals at risk of AKI during ultramarathon event is critical for implementing preventative strategies.ObjectivesTo investigate the impact of speed variability to identify the exercise-related acute kidney injury anticipatively in ultramarathon event.MethodsThis is a prospective, observational study using data from a 100 km ultramarathon in Taipei, Taiwan. The distance of entire ultramarathon race was divided into 10 splits. The mean and variability of speed, which was determined by the coefficient of variation (CV) in each 10 km-split (25 laps of 400 m oval track) were calculated for enrolled runners. Baseline characteristics and biochemical data were collected completely 1 week before, immediately post-race, and one day after race. The main outcome was the development of AKI, defined as Stage II or III according to the Acute Kidney Injury Network (AKIN) criteria. Multivariate analysis was performed to determine the independent association between variables and AKI development.Results26 ultramarathon runners were analyzed in the study. The overall incidence of AKI (in all Stages) was 84.6% (22 in 26 runners). Among these 22 runners, 18 runners were determined as Stage I, 4 runners (15.4%) were determined as Stage II, and none was in Stage III. The covariates of BMI (25.22 ± 2.02 vs. 22.55 ± 1.96, p = 0.02), uric acid (6.88 ± 1.47 vs. 5.62 ± 0.86, p = 0.024), and CV of speed in specific 10-km splits (from secondary 10 km-split (10^th – 20^th km-split) to 60^th – 70^th km-split) were significantly different between runners with or without AKI (Stage II) in univariate analysis and showed discrimination ability in ROC curve. In the following multivariate analysis, only CV of speed in 40^th – 50^th km-split continued to show a significant association to the development of AKI (Stage II) (p = 0.032).ConclusionsThe development of exercise-related AKI was not infrequent in the ultramarathon runners. Because not all runners can routinely receive laboratory studies after race, variability of running speed (CV of speed) may offer a timely and efficient tool to identify AKI early during the competition, and used as a surrogate screening tool, at-risk runners can be identified and enrolled into prevention trials, such as adequate fluid management and avoidance of further NSAID use.     

Impact of HIV-1 Subtype on the Time to CD4+ T-Cell Recovery in Combination Antiretroviral Therapy (cART)-Experienced Patients

Human immunodeficiency virus type 1 (HIV-1) subtypes have been shown to differ in the rate of clinical progression. We studied the association between HIV-1 subtypes and the rate of CD4+ T-cell recovery in a longitudinal cohort of patients on combination antiretroviral therapy (cART). We studied 103 patients infected with CRF01_AE (69%) and subtype B (31%) who initiated cART between 2006 and 2013. Demographic data, CD4+ T-cell counts and HIV-1 viral load were abstracted from patient medical charts. Kaplan-Meier was used to estimate the time to CD4+ T-cell count increase to ≥350 between subtypes and effects of covariates were analysed using Cox proportional hazards. An 87% of the study population were male adults (mean age of 38.7 years old). Baseline CD4+ T-cell counts and viral loads, age at cART initiation, sex, ethnicity and co-infection did not differ significantly between subtypes. A shorter median time for CD4+ T-cell count increase to ≥350 cells/μL was observed for CRF01_AE (546 days; 95% confidence interval [CI], 186–906 days; P = .502) compared to subtype B (987 days; 95% CI, 894–1079 days). In multivariate analysis, female sex was significantly associated with a 2.7 times higher chance of achieving CD4+ T-cell recovery (adjusted hazard ratio [HR], 2.75; 95% CI, 1.21–6.22; P = .025) and both baseline CD4+ T-cell count (P = .001) and viral load (P = .001) were important predictors for CD4+ T-cell recovery. Immunological recovery correlated significantly with female sex, baseline CD4+ T-cell counts and viral load but not subtype.     

Glucose and insulin improve cardiac efficiency and postischemic functional recovery in perfused hearts from type 2 diabetic (db/db) mice

Hearts from type 2 diabetic (db/db) mice demonstrate altered substrate utilization with high rates of fatty acid oxidation, decreased functional recovery following ischemia, and reduced cardiac efficiency. Although db/db mice show overall insulin resistance in vivo, we recently reported that insulin induces a marked shift toward glucose oxidation in isolated perfused db/db hearts. We hypothesize that such a shift in metabolism should improve cardiac efficiency and consequently increase functional recovery following low-flow ischemia. Hearts from db/db and nondiabetic (db/+) mice were perfused with 0.7 mM palmitate plus either 5 mM glucose (G), 5 mM glucose and 300 microU/ml insulin (GI), or 33 mM glucose and 900 microU/ml insulin (HGHI). Substrate oxidation and postischemic recovery were only moderately affected by GI and HGHI in db/+ hearts. In contrast, GI and particularly HGHI markedly increased glucose oxidation and improved postischemic functional recovery in db/db hearts. Cardiac efficiency was significantly improved in db/db, but not in db/+ hearts, in the presence of HGHI. In conclusion, insulin and glucose normalize cardiac metabolism, restore efficiency, and improve postischemic recovery in type 2 diabetic mouse hearts. These findings may in part explain the beneficial effect of glucose-insulin-potassium therapy in diabetic patients with cardiac complications.     

Rosiglitazone treatment improves cardiac efficiency in hearts from diabetic mice

Isolated perfused hearts from type 2 diabetic (db/db) mice show impaired ventricular function, as well as altered cardiac metabolism. Assessment of the relationship between myocardial oxygen consumption (MVO(2)) and ventricular pressure-volume area (PVA) has also demonstrated reduced cardiac efficiency in db/db hearts. We hypothesized that lowering the plasma fatty acid supply and subsequent normalization of altered cardiac metabolism by chronic treatment with a peroxisome proliferator-activated receptor-gamma (PPARgamma) agonist will improve cardiac efficiency in db/db hearts. Rosiglitazone (23 mg/kg body weight/day) was administered as a food admixture to db/db mice for five weeks. Ventricular function and PVA were assessed using a miniaturized (1.4 Fr) pressure-volume catheter; MVO(2) was measured using a fibre-optic oxygen sensor. Chronic rosiglitazone treatment of db/db mice normalized plasma glucose and lipid concentrations, restored rates of cardiac glucose and fatty acid oxidation, and improved cardiac efficiency. The improved cardiac efficiency was due to a significant decrease in unloaded MVO(2), while contractile efficiency was unchanged. Rosiglitazone treatment also improved functional recovery after low-flow ischemia. In conclusion, the present study demonstrates that in vivo PPARgamma-treatment restores cardiac efficiency and improves ventricular function in perfused hearts from type 2 diabetic mice.     

A comparison of membranes and enrichment strategies for microbial fuel cells

The external resistance is perhaps the easiest way to influence the operation of a microbial fuel cell (MFC). In this paper, three enrichment strategies, whereby the external resistance was fixed at: (1) a high value in order to maximize the cell voltage (U strategy); (2) a low value in order to maximize the current (I strategy); and (3) a value equal to the internal resistance of the MFC to maximize the power output (P strategy), were investigated. The I strategy resulted in increased maximum power generation and the likely reason is that electron transfer was facilitated under low external resistance, which in turn, favored the development of an electrochemically active biofilm. This experiment was conducted in a single-chamber MFC system equipped with a membrane electrode assembly, and a comparison of the performance achieved by five different membranes is also provided. Selemion was found to be a suitable alternative to Nafion.     

Influence of substrate supply on cardiac efficiency, as measured by pressure-volume analysis in ex vivo mouse hearts

In the present study, we tested the reliability of measurements of pressure-volume area (PVA) and oxygen consumption (MVo(2)) in ex vivo mouse hearts, combining the use of a miniaturized conductance catheter and a fiber-optic oxygen sensor. Second, we tested whether we could reproduce the influence of increased myocardial fatty acid (FA) metabolism on cardiac efficiency in the isolated working mouse heart model, which has already been documented in large animal models. The hearts were perfused with crystalloid buffer containing 11 mM glucose and two different concentrations of FA bound to 3% BSA. The initial concentration was 0.3 +/- 0.1 mM, which was subsequently raised to 0.9 +/- 0.1 mM. End-systolic and end-diastolic pressure-volume relationships were assessed by temporarily occluding the preload line. Different steady-state PVA-MVo(2) relationships were obtained by changing the loading conditions (pre- and afterload) of the heart. There were no apparent changes in baseline cardiac performance or contractile efficiency (slope of the PVA-MVo(2) regression line) in response to the elevation of the perfusate FA concentration. However, all hearts (n = 8) showed an increase in the y-intercept of the PVA-MVo(2) regression line after elevation of the palmitate concentration, indicating an FA-induced increase in the unloaded MVo(2). Therefore, in the present model, unloaded MVo(2) is not independent of metabolic substrate. This is, to our knowledge, the first report of a PVA-MVo(2) relationship in ex vivo perfused murine hearts, using a pressure-volume catheter. The methodology can be an important tool for phenotypic assessment of the relationship among metabolism, contractile performance, and cardiac efficiency in various mouse models.     

Some of the properties of flame retardant medium density fiberboard made from rubberwood and recycled containers containing aluminum trihydroxide

The flame retardancy of medium density fiberboard (MDF) made from mixture of rubberwood fibers and recycled old corrugated containers was studied. Aluminum trihydroxide (ATH) was used as a fire retardant additive and mixed with the fibers to manufacture experimental MDF panels using wet process. Phenol formaldehyde (PF) resin in liquid, 2% based on oven dry weight of fibers, was used along with 0%, 10%, 15% and 20% of ATH. The flame retardant test was done using the limiting oxygen index (LOI) test. The other properties investigated include internal bond strength, thickness swelling and water absorption. The results showed that ATH loading increased as the LOI of MDF increased. This demonstrated that ATH could improved the fire retardant property of MDF at sufficient loading. An increase in concentration of ATH showed an increase in the IB values of MDF made without resin. MDF panels made without resin showed a progressive increase in internal bond as the composition of recycled old corrugated containers fiber increased. Addition of resin improved internal bond strength and reduced thickness swelling, and water absorption. Thickness swelling of panel increased as the composition of recycled old corrugated containers fiber increased. Scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX) showed that there is indication of ATH and resin filling the void space in between fibers.