Pregnancy alters diurnal variation of plasma glucose concentration

Human pregnancy introduces a diurnal variation of fasting plasma glucose concentrations, with significantly lower values found after a daytime fast of eight hours compared with a night-time fast of the same duration. The diurnal variation of plasma glucose clearance, found in nonpregnant subjects, is not demonstrable during pregnancy. Insulin tolerance does not exhibit a circadian valuation but is substantially decreased during pregnancy.     

Effects of Dietary D-Psicose on Diurnal Variation in Plasma Glucose and Insulin Concentrations of Rats

The effects of supplemental D-psicose in the diet on diurnal variation in plasma glucose and insulin concentrations were investigated in rats. Forty-eight male Wistar rats were divided into four groups. Each group except for the control group was fed a diet of 5% D-fructose, D-psicose, or psico-rare sugar (3:1 mixture of D-fructose and D-psicose) for 8 weeks. Plasma glucose levels were lower and plasma insulin levels were higher at all times of day in the psicose and psico-rare sugar groups than in the control and fructose groups. Weight gain was significantly lower in the psicose group than in the control and fructose groups. Liver glycogen content, both before and after meals was higher in the psicose group than in the control and fructose groups. These results suggest that supplemental D-psicose can lower plasma glucose levels and reduce body fat accumulation. Hence, D-psicose might be useful in preventing postprandial hyperglycemia in diabetic patients.     

C_3植物光合效率的日变化

多种田间C_3植物在晴天的光合效率常有明显的日变化,中午前后光合效率降低。C_3植物大豆叶片光合效率中午降低的主要原因,不是空气CO_2浓度和气孔导度及光呼吸的变化,而可能是光抑制。因为:1.在饱和CO_2中测定仍可观测到这种中午降低;2.光合作用的饱和光强远低于晴天中午的太阳光强;3.用纱布预遮阴可以提高叶片的光合效率;4.阴天时叶片光合效率不发生中午降低。     

Diurnal Variation in the Symptoms of Colds and Influenza

The present research examined diurnal variation in the severity of symptoms of experimentally-induced colds and influenza. Nasal secretion was greatest in the morning, decreased over the day, and then showed a slight increase in the late evening. Colds did not change the average temperature, nor did they alter the temperature rhythm. Similar, negative results were found with alertness ratings.

Influenza B illnesses produced an increase in nasal secretion and systemic effects. The average temperature increased during this illness and subjects reported that they felt more drowsy. Diurnal variation in the severity of local and central symptoms was observed, with nasal secretion and the temperature increase being greatest in the early morning. These results have important implications for the assessment and treatment of the illnesses.     

C_4植物玉米叶片光合效率的日变化

在没有水分、温度和营养等环境胁迫的田间条件下,晴天C_4植物玉米叶片光合效率的日变化方式明显地不同于许多C_3植物,即中午光合效率不降低,而是略有提高。日间玉米叶片的光合效率大体上随着光量子通量密度的变化而变化。从上午8时至下午14时用纱布遮荫6h,叶片的光合效率下降。用强光预照光可以提高在温度、水分和CO_2浓度恒定条件下离体叶片的光合效率。另外,即使在全日光强下玉米叶片的净光合速率也不饱和。这些表明,晴天中午玉米叶片光合效率的提高依赖于强光。用强光预照光引起玉米叶片叶绿素荧光参数F_v/F_m的轻微下降,表明强光引起的光合效率提高不是由于光系统Ⅱ光化学效率的改善。     

报春石斛花香气成分及其日变化规律

采用静态顶空气相色谱-质谱(GC-MS)联用技术研究报春石斛(Dendrobium primulinum)花香气成分及香气释放的日变化规律,检测并分析一天内六个时间点(6:00、9:00、12:00、15:00、18:00、21:00)报春石斛花的香气成分。各时间点占总香气释放量排序为：6时(35.26%)>9时(22.78%)>12时(19.35%)>21时(7.86%)>15时(7.59%)>18时(7.17%)。共检测出202种香气物质,包括酯类、烯萜类、醇类、醛类、烷类等,其中6:00有93种,9:00有87种,12:00有68种,15:00有61种,18:00有63种,21:00有65种。各个时间点共有的化合物21种。报春石斛花香气释放量6:00最高,18:00最低,主要香气成分是醋酸辛酯。     

Diurnal Variation in the Symptoms of Colds and Influenza

The present research examined diurnal variation in the severity of symptoms of experimentally-induced colds and influenza. Nasal secretion was greatest in the morning, decreased over the day, and then showed a slight increase in the late evening. Colds did not change the average temperature, nor did they alter the temperature rhythm. Similar, negative results were found with alertness ratings.

Influenza B illnesses produced an increase in nasal secretion and systemic effects. The average temperature increased during this illness and subjects reported that they felt more drowsy. Diurnal variation in the severity of local and central symptoms was observed, with nasal secretion and the temperature increase being greatest in the early morning. These results have important implications for the assessment and treatment of the illnesses.     

不同品种美国山核桃叶绿素荧光参数日变化的研究

以湖南省永州市冷水滩采穗圃中的美国山核桃为试材,研究了叶绿素荧光参数的日变化规律。结果表明:初始荧光(Fo)、最大荧光(Fm)、PSII原初光能转化效率(Fv/Fm)、光合量子产额(Yield)、光化学猝灭系数(qP)、非光化学猝灭系数(qN)和表观电子传递速率(ETR)均存在着明显的日变化。其中Fv/Fm、Fm、Yield、qP均呈先下降后上升的趋势,在中午强光下降低到最低值;qN则呈先上升后下降的趋势,在中午时分达到峰值;Fo呈下降趋势,部分品种傍晚稍有回升,但仍比早晨低;ETR日变化呈双峰曲线。不同品种间Fv/Fm、Yield、ETR、qP、qN对光强和温度的响应也存在着明显差异,可作为鉴定品种耐光抑制能力大小的指标。     

Effect of Glucose Tolerance Status on PAI‐1 Plasma Levels in Overweight and Obese Subjects

Objective: The aim of our study was to examine whether plasminogen activator inhibitor‐1 (PAI‐1) plasma levels varied as a function of differences in glucose tolerance status independently of body fatness, body‐fat distribution, and insulin sensitivity. Research Methods and Procedures: Plasma PAI‐1 antigen levels, along with insulin resistance [measured by homeostatic model assessment (HOMA_IR)], central fat accumulation, body composition, blood pressure, and fasting concentrations of glucose, insulin, and lipids, were measured in 229 overweight and obese [body mass index (BMI) ≥25 kg/m²) subjects with normal glucose tolerance (NGT) and in 44 age‐ and BMI‐matched subjects with impaired glucose tolerance (IGT). Results: Plasma PAI‐1 antigen levels were significantly higher in IGT than in NGT subjects. Log PAI‐1 was positively correlated with BMI, HOMA_IR, and log insulin, and inversely associated with high‐density lipoprotein‐cholesterol both in IGT and in NGT individuals. On the other hand, log PAI‐1 was positively correlated with waist circumference, fat mass (FM), fat‐free mass, systolic and diastolic blood pressure, and log triglycerides only in the NGT group. After multivariate analyses, the strongest determinants of PAI‐1 levels were BMI, FM, waist circumference, and high‐density lipoprotein cholesterol in the NGT group and only HOMA_IR in the IGT cohort. Discussion: This study demonstrates that PAI‐1 concentrations are higher in IGT than in NGT subjects. Furthermore, we suggest that the influences of total adiposity, central fat, and insulin resistance, main determinants of PAI‐1 concentrations, are different according to the degree of glucose tolerance.     

妊娠期糖代谢异常对新生儿出生结局的影响

目的：探讨妊娠期不同程度的糖代谢异常对胎儿发育及结局的影响。方法：前瞻性收集我院2009年1月至2010年1月分娩的糖代谢异常的331例单胎妊娠孕妇,分为糖筛查异常组69例、糖耐量异常组126例、妊娠期糖尿病（Gestaional DiabetesMellitus,GDM）组136例,并选择同期糖代谢正常的751例单胎孕妇为对照组,比较四组新生儿出生的最终结局。结果：糖筛查异常组与对照组新生儿结局差异无显著性意义（P〉0.05）;糖耐量异常组中巨大儿及新生儿窒息、早产儿的发生率与对照组差异有显著性意义（P〈0.05）;GDM组与对照组差异有显著性意义（P〈0.05）。结论：母亲妊娠期不同程度的糖代谢异常对新生儿影响不同。口服葡萄糖耐量试验（Oral Glucose Tolerance Test,OGTT）异常与GDM一样对新生儿发育及结局均有影响,可使巨大儿、新生儿窒息、早产儿的发生率增高。     

妊娠期糖代谢异常对新生儿出生结局的影响

目的:探讨妊娠期不同程度的糖代谢异常对胎儿发育及结局的影响。方法:前瞻性收集我院2009年1月至2010年1月分娩的糖代谢异常的331例单胎妊娠孕妇,分为糖筛查异常组69例、糖耐量异常组126例、妊娠期糖尿病(Gestaional DiabetesMellitus,GDM)组136例,并选择同期糖代谢正常的751例单胎孕妇为对照组,比较四组新生儿出生的最终结局。结果:糖筛查异常组与对照组新生儿结局差异无显著性意义(P>0.05);糖耐量异常组中巨大儿及新生儿窒息、早产儿的发生率与对照组差异有显著性意义(P<0.05);GDM组与对照组差异有显著性意义(P<0.05)。结论:母亲妊娠期不同程度的糖代谢异常对新生儿影响不同。口服葡萄糖耐量试验(Oral Glucose Tolerance Test,OGTT)异常与GDM一样对新生儿发育及结局均有影响,可使巨大儿、新生儿窒息、早产儿的发生率增高。     

不同光照强度下辣木光合作用及与其相关生理指标的日变化

测定不同光照强度下生长的辣木光合作用及与其相关生理指标日变化的结果表明,在高温和高光强的夏季,辣木的净光合速率总体趋势是：遮光35％〉自然光〉遮光65％。适当的遮光（遮光35％）后,光合速率的峰值出现晚,高光合速率的时间维持的比较长。但遮光不能过甚,当遮光达到65％时,净光合速率除在中午11：00前后外,其他时间内均处于较低水平。据此认为,在南方高温和高光强的季节里,辣木适当遮光可以提高辣木的光合速率。     

温州蜜柑（Citrus unshiu Marc．）叶片光合效率的日变化

在５～１０月的晴天,以最大表观量子产量Φｉ表示的温州蜜柑光合效率上午从测定开始时起持续下降,下午逐渐回升,与光强和叶温的日变化大致是镜象反相关。这与净光合速率峰谷交替的日变化明显不同。自然条件下遮荫或控制测定时的叶温得到的Φｉ的日变化主要取决于测定时的对温,叶温高则Φｉ低。不同时间在相近叶温下测得的Φｉ;没有显著差异。测定前叶片的光照强度对Φｉ不起决定作用。低Ｏ２可以消除升温的不利影响。光呼吸相对于光合的增强是升温导致Φｉ下降的主要原因。光合效率日变化的生理原因也部分地提供了对净光合日变化的解释。     

八倍体小偃麦和普通小麦旗叶及叶鞘光合日变化比较研究

以温室大棚中栽培的普通小麦'中国春'(对照)及八倍体小偃麦'小偃7430'(染色体组为ABDE_1)、'小偃693'(染色体组为ABDF_1)为材料,采用TPS-1光合作用测定系统及FMS-2荧光仪测定了开花期旗叶和叶鞘的净光合速率、气孔导度和叶绿素荧光参数的日变化,以揭示普通小麦与八倍体小偃麦旗叶及其叶鞘的光合作用差异.结果表明:八倍体小偃麦与普通小麦'中国春'的旗叶和叶鞘光合作用均有午休现象,净光合速率于上午11:00左右出现高峰,午间下降,下午又呈现上升趋势,且'小偃693'叶片在上午时上升较快;气孔导度和荧光参数F_v/F_m、Fv/F_o、 Φ_(PS)Ⅱ、ETR的变化趋势与净光合速率相似,而NPQ的变化趋势则相反.各光合作用和叶绿素荧光参数在材料间表现为八倍体小偃麦高于普通小麦'中国春',器官间表现为旗叶高于相应叶鞘,而'小偃693'的叶鞘和'中国春'叶片的相似.研究发现,八倍体小偃麦旗叶和叶鞘的光合效率优于普通小麦'中国春';'小偃693'的光合效率因其较高的光反应活性表现得尤为突出,其叶鞘的光合能力也不容忽视.     

Glucose regulation in captive Pongo pygmaeus abeli,P. p. pygmaeus,andP. p. abeli x P. p. pygmaeus orangutans

Intravenous glucose tolerance tests (IVGTT) were performed on 30 anesthetized, captive Sumatran (Pongo pygmaeus abeli), Bornean (P. p. pygmaeus), and hybrid (P. p. ablie x P. p. pygmaeus) orangutans, and fasted blood samples were taken from two additional juvenile orangutans in 11 U.S. zoos from 1989 to 1997. The age range of animals was 3.5 to 40.5 years. Plasma and serum samples were assayed for glucose and insulin concentrations. Glucose disappearance rate (K_G), an index of glucose tolerance, was calculated, as were the early (acute) and second phase insulin responses to administered glucose. The mean ± SE (and median) fasting glucose and insulin concentrations were 113 ± 16 mg/dL (90 mg/dL) and 45 ± 7 μU/mL (27 μU/mL), respectively. Two animals previously suspected to be diabetic were easily identified by their markedly elevated fasting glucose concentrations (380 and 562 mg/dL) and relatively low fasted insulin concentrations (21 and 14 μU/mL); their insulin responses during the IVGTTs were also low or non‐detectable. Without these diabetics, the mean ± SE (median) fasting glucose concentration was 92 ± 18 mg/dL (89 mg/dL). Two animals, ages 18 and 40, were identified as potentially pre‐diabetic based on age, adiposity, elevated fasted glucose (116 and 137 mg/dL, respectively), and elevated fasted insulin concentrations (114 and 217 μU/mL, respectively). In addition, nearly half of the animals of varying ages, all sub‐species and both sexes exhibited delayed or attenuated acute insulin responses during the IVGTTs, resulting in lower K_G (P < 0.04) and suggesting propensity for glucose intolerance in captive orangutans. Glucose and insulin concentrations and insulin responses to glucose did not differ between females on hormonal contraception regimes and those not receiving treatment. Zoo Biol 19:193–208, 2000. © 2000 Wiley‐Liss, Inc.     

羌活光合作用日变化及其与生理生态因子的关系

以大田引种栽培的羌活植株为材料,用Li-6400便携式光合作用测定系统原位测定自然条件下生长的羌活孕蕾期叶片的光合速率光响应、净光合速率及生理生态因子日变化,并通过相关分析、通径分析和逐步回归分析探讨净光合速率与生理生态因子的关系.结果表明:(1)羌活净光合速率(P_n)、 蒸腾速率(T_r)、气孔导度(G_s)日变化均呈双峰曲线,其净光合速率具有典型的"午休"现象,并主要由非气孔限制因素造成;(2)影响羌活叶片Pn日变化的主要决定生理因子是G_s,主要限制因子是胞间CO_2浓度(C_i);主要决定生态因子是空气相对湿度(RH),限制因子是气温(T_a); G_s是影响净光合速率最重要的生理生态因子.研究发现,羌活有较强的适应弱光环境的能力,属于阳性耐荫植物,宜选择海拔和荫蔽度均较高的环境进行引种驯化栽培,以利于其生长和存活.     

Effect of One Morning Meal and a Bolus of Dexamethasone on 24‐Hour Variation of Serum Leptin Levels in Humans

Objective: We have previously shown that morning administration of dexamethasone in combination with food induces a doubling of serum leptin levels starting at 7 hours after dexamethasone administration, with a maximum effect at 10 hours, the latest time point that we have studied. However, dexamethasone given in the absence of food had no effect on serum leptin at 10 hours. The present experiment was undertaken to determine the duration of the effect of dexamethasone on 24‐hour serum leptin under fasted and fed conditions in humans. Research Methods and Procedures: Six healthy non‐obese male volunteers were studied under the following four conditions: 1) dexamethasone (2 mg intravenously, given at 0900 hours) with fasting; 2) dexamethasone with food (1700 kcal, 55% carbohydrate, 15% protein, and 30% fat, given in one meal 2 hours after dexamethasone administration at 1100 hours); 3) saline with food (same meal); 4) saline with fasting. Serum leptin, glucose, insulin, and cortisol were monitored every 30 minutes for 24 hours. Results: 1) Under the fasting condition, dexamethasone increased leptin nocturnal secretion between 2100 and 2400 hours. 2) A single meal (1700 kcal) at 1100 hours increased nocturnal leptin secretion when compared with the fasting condition. The peak increase of leptin was 123% over baseline between 2100 and 2400 hours, 10 to 14 hours after the meal. 3) In the fed + dexamethasone condition, leptin levels increased from baseline starting 8 hours after dexamethasone injection, reached a maximum increase of 260% between 2100 and 2400 hours, then decreased thereafter, remaining elevated compared to baseline for 16 hours. There was a correlation between 24‐hour leptin secretion and insulin secretion after a single morning meal. Discussion: A single bolus of dexamethasone, given before a single large meal, produces a delayed (6‐hour) but long‐lasting increase in serum leptin (over 16 hours). Under fasted conditions, dexamethasone does not increase daytime leptin but does increase leptin during the night.     

高海拔地区烟草光合作用的日变化

在高海拔地区(昆明)对5个品种(系)烟草光合作用日变化的研究结果表明,所有供试材料的净光合速率表现为不显著的"双峰型"曲线。其主要原因可能是较高的空气湿度、相对适宜的温度和强光的综合影响;一定范围内的温度和CO₂浓度变化对光合作用的日变化未能产生明显的影响。     

The Effect of Glucose Concentration on Insulin-Induced 3T3-L1 Adipose Cell Differentiation

We examined the effect of glucose concentration on insulin-induced 3T3-L1 adipose cell differentiation. Oil Red O staining of neutral lipid, cellular triglyceride mass, and glycerol phosphate dehydrogenase (GPDH) activity, were greater in 3T3-L1 cells cultured at 5 mM vs. 25 mM glucose. GPDH activity was 2- to 4-fold higher at 5 mM vs. 25 mM glucose over a range of insulin concentrations (0. 1 to 100 nM). Insulin-stimulated tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1) was 1. 7-fold greater, and insulinstimulated phosphoinositide 3-kinase association with IRS-1 was 2. 3-fold higher, at 5 mM vs. 25 mM glucose. These effects of glucose were not caused by alterations in IRS-1 mass or cell-surface insulin binding. In preadipose cells at 5 mM glucose, expression of the leukocyte antigen-related (LAR) protein tyrosine phosphatase (negative regulator of insulin signaling) was 63% of the level at 25 mM glucose. Our data demonstrate that glucose concentration affects insulin-induced 3T3-L1 adipose cell differentiation as well as differentiation-directed insulin signaling pathways. Alterations in LAR expression potentially may be involved in modulating these responses.     

Comparison of Freeze-Blowing and Funnel-Freezing of Rat Brain for the Measurement of Cerebral Glucose Concentration In Vivo

The efficacy of funnel-freezing of rat brain to inactivate metabolic processes and preserve in vivo tissue glucose concentration was validated by comparing the results obtained by funnel-freezing with those obtained with freeze-blowing of brain. The arterial plasma glucose level was clamped at 9 mM in halothane-anesthetized rats to produce identical glucose levels in brain tissue prior to freeze fixation. In funnel-frozen and freeze-blown brains, tissue glucose concentrations were 2.47 +/- 0.05 and 2.47 +/- 0.06 mumol/g (means +/- SEM), respectively. Lactate levels in funnel-frozen brains were slightly but significantly higher than those in freeze-blown brains, i.e., 1.56 +/- 0.05 mumol/g versus 1.30 +/- 0.05 mumol/g (means +/- SEM; p less than 0.05). Regional analysis in funnel-frozen brains revealed that glucose concentrations in superficial and basal brain areas remained approximately equal at 2.30 +/- 0.1 mumol/g and 2.31 +/- 0.09 mumol/g (means +/- SEM), respectively. Our findings indicate that in the anesthetized rat, funnel-freezing of brain is suitable for the measurement of regional in vivo glucose concentrations.