What the hen can tell about her eggs: egg development on the basis of energy budgets

By a simple model involving the state variables size and storage, it is possible to describe a wide variety of observations on the feeding, growth, energy storage and reproduction of animals. The model is based on the assumption that reproduction, growth as well as maintenance depend on the stored energy only and not directly on feeding. If an egg is thought of as a non-feeding animal, the model predicts the respiration ontogeny and growth of the embryo inside the egg. These predictions seem to hold well for published data on the development of eggs of fish and ratite, precocial and altricial birds. The latter two are known to follow different respiration ontogenies, but both are described well, differing only in one (compound) parameter value. The model explains why the incubation times of eggs of different species tend to increase linearly with egg size to the power 1/4, and why kiwis and petrels, which lay relatively large eggs, have to brood them much longer than larger birds with eggs of the same size. Conversely, it explains why the small eggs of the (parasitic) European cuckoo, hatch earlier than the still smaller eggs of their tiny hosts.Furthermore, it has been shown how the maintenance rate constant, which frequently appears in the microbial literature, can be obtained from measurements on the respiration and weight ontogeny in embryos, so linking independent lines of research. Application of the model shows an increase of the maintenance rate constant from bacteria, crustaceans, up to fish and birds, and a decrease from bacteria to green algae, suggesting lines of evolutionary development.     

Eubacteria have 3 growth modes keyed to nutrient flow

Aerobic growth of Escherichia coli and Paracoccus denitrificans has been studied in chemostat, fed batch, and recycling fermentor modes under carbon and energy limitation. Two abrupt drops or discontinuities in molar growth yield, Y, have been found that occur over relatively short ranges in the value of specific growth rate.Before the first discontinuity, Y is constant and maximal. After the first discontinuity, at a doubling time of 33 h, Y becomes constant again and independent of until the second discontinuity appears at a doubling time of about 50 h, corresponding to a of about 0.014. At this point, Y drops to a lower value that is constant at doubling times longer than 100 h, corresponding to a of about 0.007.The second discontinuity is associated in Paracoccus with elevated levels of guanosine tetraphosphate (ppGpp) that impose stringent regulation as has been found previously with Bacillus and Escherichia species. It is thus likely that the stringent response generally occurs in bacteria in vivo at a doubling time of about 50 h. The cause of the first discontinuity is unknown. All experiments indicate that Pirt-type calculations relating , Y, and maintenance energy demand are no longer valid. In chemostat experiments, the intercept of the relationship between specific substrate utilization and specific growth rate is defined as maintenance. However, this intercept most probably is caused by stringent regulation at low dilution rates. Three regions of bacterial growth rates are defined by this study, corresponding to doubling times of 0.5 to 15 h, 33 to 50 h, and >100 h. Some growth behavior in each region is unique to that region.Abbreviations ppGpp guanosine 5 diP 3 diP - pppGpp guanosine 5 triP 3 diP - SPR substrate provision rate (mol/l h)     

Maintenance energy: a general model for energy-limited and energy-sufficient growth

The new model proposed to account for the energy requirement for growth includes both a constant maintenance energy term (m) independent of the specific growth rate and a term (m′) which decreases linearly with increase in specific growth rate and becomes zero at the maximum specific growth rate. The available data for testing the model do not deviate significantly from the relations predicted. Consistent values of the maximum growth yield (Y _G) can be derived, irrespective of whether the cultures are energy limited or energy sufficient. Attention is drawn to the possibility that the constant maintenance energy term may be estimated from the maximum specific growth rate.     

糖尿病肾病维持性血液透析患者低血糖发生情况及其影响因素的Logistic回归分析

摘要 目的：探讨糖尿病肾病（DN）维持性血液透析患者低血糖发生情况,并分析其影响因素。方法：选择2018年7月~2021年2月期间收治的100例DN维持性血液透析患者,记录低血糖发生情况,按照是否发生低血糖将患者分为低血糖组（n=47）和无低血糖组（n=53）。收集两组患者的临床资料,采用多因素Logistic回归分析DN维持性血液透析患者低血糖发生的影响因素。结果：100例患者1个月内共检测血糖 1200次,其中有47例出现低血糖症状,低血糖发生率为47.00%（47/100）,53例患者未发生低血糖。DN维持性血液透析患者低血糖发生与性别、婚姻状况、工作状况、医保类型、维持性血液透析方式、收缩压、空腹血糖（FBG）、内生肌酐清除率（Ccr）、低密度脂蛋白胆固醇（LDL-C）、三酰甘油（TG）无关（P>0.05）,而与年龄、DN病程、体质量指数、文化程度、尿微量蛋白尿排泄率（UAER）、用药依从性、自我管理能力、照护能力有关（P<0.05）。多因素logistic回归性分析结果显示：年龄偏大、DN病程偏长、体质量指数偏低、UAER偏高是DN维持性血液透析患者低血糖发生的危险因素,而用药依从性、照护能力良好则是DN维持性血液透析患者低血糖发生的保护因素（P<0.05）。结论：DN维持性血液透析患者低血糖发生率较高,其中年龄偏大、DN病程偏长、体质量指数偏低、UAER偏高是DN维持性血液透析患者低血糖发生的危险因素,而用药依从性、照护能力良好则是其保护因素。     

维持性腹膜透析患者血管钙化评估及血清sclerostin、FGF-23测定对血管钙化发生风险的预测价值研究

摘要 目的：评估维持性腹膜透析（PD）患者血管钙化（VC）情况,分析血清骨硬化蛋白（sclerostin）、成纤维生长因子-23（FGF-23）测定对VC发生风险的预测价值。方法：选择2018年5月~2021年6月期间我院收治的维持性PD患者103例为研究对象。收集所有患者的临床资料进行分析,观察VC情况,多因素Logistic回归分析维持性PD患者VC的危险因素。受试者工作特征曲线（ROC）分析血清sclerostin、FGF-23单独及联合测定对VC的预测价值。结果：103例维持性PD患者中有69例（66.99%）存在不同部位、不同程度的VC。根据是否出现VC进行分组,其中VC患者69例（VC组）,未出现VC患者34例（无VC组）。与无VC组患者相比,VC组年龄、合并糖尿病人数占比、血清sclerostin、FGF-23、血钙（Ca）水平明显更高,透析时间明显更长,全段甲状旁腺激素水平明显更低（P<0.05）。透析时间≥32月、年龄≥55岁、合并糖尿病、血清FGF-23≥80 pg/mL、Ca≥1.3 mmol/L、血清sclerostin≥7 ng/mL是维持性PD患者并发VC的危险因素（P＜0.05）。血清sclerostin、FGF-23的曲线下面积（AUC）（0.95CI）分别为0.783（0.691～0.858）、0.793（0.702～0.866）,有一定的预测效能,而两指标联合应用时：AUC（0.95CI）为0.867（0.786～0.926）,预测效能更高。结论：维持性PD患者VC的发生与透析时间、年龄、合并糖尿病、FGF-23、Ca、sclerostin有关,sclerostin、FGF-23联合测定对VC发生风险的预测价值较高,对于此类患者VC的评估具有辅助作用。     

溃疡性结肠炎缓解期服用益生菌制剂维持治疗的Meta分析

目的系统评价益生菌制剂用于溃疡性结肠炎(ulcerative colitis,UC)缓解期维持治疗的疗效。方法采用计算机检索和手工检索两种方法,以益生菌及其近义词、溃疡性结肠炎等主题词检索Cochrane国际协作网随机对照试验(RCT)注册数据库、PubMed、Embase数据库和中国期刊网等数据库(1978-2009),所选文献符合缓解期UC的诊断标准,以美沙拉嗪为对照的随机对照试验。采用Cochrane系统评价员手册4.2.2推荐的方法纳入文献,并对其进行Meta分析。结果共纳入6个RCT,包括629名患者,Meta分析结果显示:临床复发率益生菌组与美沙拉嗪差异无显著性(OR=0.84,95%CI:0.59~1.19,P=0.33)。结论益生菌制剂与美沙拉嗪对于UC缓解期维持治疗的疗效相近,益生菌制剂是有效的溃疡性结肠炎缓解期维持治疗药物。     

长白山地区红松树干呼吸的研究

采用土壤呼吸气室于2003年5～10月测定了长白山阔叶红松林主要树种红松不同径阶不同方位的树干呼吸,同时监测了树干温度和林内温度.结果表明,树干呼吸速率具有明显的季节变化趋势,呈单峰曲线,8月出现最大值,2月呼吸速率最低.树干呼吸速率与树干温度具有显著幂指数关系,同时表现出大径阶树干呼吸速率与温度因子间曲线拟合效果好于小径阶红松.不同径阶树干呼吸速率均呈南面高于北面,并随树干径阶的减小南北面呼吸速率差异降低.不同径阶红松树干平均维持呼吸占总树干呼吸63.63%,红松树干径阶越大维持呼吸所占比例越大.依树干径阶大小顺序分别为66.76%、73.29%和50.84%.不同径阶红松树干呼吸Q₁₀值在2.56～3.32之间,利用呼吸Q₁₀值分别获得不同径阶树干R_t和R_m的季节变化趋势.因此,当估算生态系统呼吸时应考虑树干不同部位和不同径阶之间的差异.     

Growth parameters (K s, μmax,Y s) of Methanobacterium thermoautotrophicum

Methanobacterium thermoautotrophicum was grown on a mineral salts medium in a fermenter gassed with H₂ and CO₂, which were the sole carbon and energy sources. Under the conditions used the bacterium grew exponentially. The dependence of the growth rate () on the concentration of H₂ and CO₂ in the incoming gas and the dependence of the growth yield ( ) on the growth rate were determined at pH 7 (the pH optimum) and 65° C (the temperature optimum).The curves relating growth rate to the H₂ and CO₂ concentration were hyperbolic. From reciprocal plots apparent K _s values for H₂ and CO₂ and _max were obtained: app. = 20%; app. = 11%; = 0.69 h^-1; t (max)=1 h. was 1.6 g mol^-1 and almost independent of the growth rate, when the rate of methane formation was not limited by the supply of either H₂ or CO₂. The yield increased to near 3 g mol^-1 when H₂ or CO₂ were limiting. These findings indicate that methane formation and growth are less tightly coupled at high concentrations of H₂ or CO₂ in the medium than at low concentrations. The physiological significance of these findings is discussed. K _s: H₂ and CO₂ concentration supporting 0.5 _max; _max: specific growth rate at infinite substrate concentration; Y _s:growth yield (g dry weight/mol substrate); t : doubling time     

血清锌-α2-糖蛋白、骨硬化蛋白、胎球蛋白A水平与维持性血液透析患者冠状动脉钙化的关系及其诊断价值研究

目的:研究血清锌-α2-糖蛋白(ZAG)、骨硬化蛋白(SOST)及胎球蛋白A(FA)水平与维持性血液透析(MHD)患者冠状动脉钙化的关系及其诊断价值。方法:将2018年1月~2021年4月于我院接受MHD的203例患者纳入研究。将其按照冠状动脉钙化积分分作钙化组133例以及无钙化组70例。分析两组各项基线资料以及实验室指标水平的差异,并以多因素Logistic回归分析明确MHD患者冠状动脉钙化的影响因素。另外,通过受试者工作特征(ROC)曲线分析明确血清ZAG、SOST及FA诊断MHD患者冠状动脉钙化的效能。结果:钙化组年龄及血磷、SOST水平均高于无钙化组,而血清ZAG、FA水平均低于无钙化组(P<0.05)。经多因素Logistic回归分析可得:年龄、血磷以及血清SOST、ZAG、FA均是MHD患者冠状动脉钙化的影响因素(P<0.05)。经ROC曲线分析发现:血清ZAG、SOST及FA联合诊断MHD患者冠状动脉钙化的曲线下面积、灵敏度、特异度以及约登指数均高于上述三项指标单独诊断。结论:血清ZAG、SOST及FA均和MHD患者冠状动脉钙化密切相关,可作为辅助诊断MHD患者冠状动脉钙化的生物学标志物。