Variation in eggshell characteristics and gas exchange of montane and lowland coot eggs

Summary This study determined how structural features of the eggshells of coots (Fulica americana) laid at 4150 m in the Peruvian Andes differed from those at sea level in Peru and California and how these features affected exchange of water vapor, O₂, and CO₂. While barometric pressure at 4150 m was reduced to 60% of that at sea level, the conductance to water vapor, corrected to 760 torr, of montane eggs was 107% of the corresponding lowland value. When the effect of low barometric pressure on the diffusion coefficient of gases was considered, the effective conductance of the montane eggs at altitude was 177% of that at sea level. As a result, daily water loss from the montane eggs was substantially greater than that from lowland ones. The oxygen consumption of montane embryos was lower than that of lowland embryos of all sizes, particularly at larger embryonic masses. Just before pipping, the oxygen consumption of montane embryos was about 60% of the corresponding value for lowland individuals. Air cell oxygen tensions in montane eggs varied between about 65 and 38 torr; these values were about 60–70 torr below those in lowland eggs at equivalent embryonic masses. Just before pipping, the air cell CO₂ tension of montane eggs was about 20 torr below levels in sea level eggs. The eggshell conductance to gases of montane eggs appears to have been selected to promote oxygen delivery at the cost of increased losses of water vapor and CO₂.     

新生儿首次呼吸前后脐带动静脉血液氧和二氧化碳变化探索呼吸调控机制的初步报告I—血液氧和二氧化碳分压脐带动静脉差值的组间分析*

目的: 胎儿没有实际上的呼吸,新生儿出生后才开始呼吸,我们假设人的第一次呼吸主要是由于低氧而触发。本研究对流经主动脉体外周化学感受器后的脐带动脉血液氧分压（PuaO₂）变化规律和下限进行分析以探讨新生儿自主呼吸产生机制。方法: 选择签署知情同意书的正常分娩产妇数十例,仅14例新生儿在自主呼吸开始前成功完成脐带动脉或静脉置管。分别进行逐搏取血及顺序血气分析,计算血气指标的平均值、最高值和最低值,统计比较脐带动静脉的异同。结果: 在14例新生儿自主呼吸开始前完成采集脐带动脉（Pua）样本9例,脐带静脉（Puv）样本8例。就PO₂而言,所有9例PuaO₂随时间（心跳次数）呈逐渐降低倾向,直至在自主呼吸产生大约8~10次心跳后Pua挛缩、基本上无法取得足够的血样。PuaO₂平均值是（25.94±6.79,18.04~37.51）mmHg,最高值是（29.11±6.46,23.00~45.90）mmHg,最低值是（21.34±5.54,14.00~33.60）mmHg;但PuaCO₂变化趋势和规律则不够稳定,PuaCO₂平均值是（47.26 ±7.71） mmHg。PuvO₂随时间（心跳次数）虽也呈逐渐降低趋势,但多数还呈现随母亲呼吸节律的规律性交替升降的倾向,特别是母亲吸氧时。所有8例PuvO₂平均值是（53.35±21.35,32.56~100.73）mmHg,最高值是（90.38±48.44,43.40~153.00）mmHg,最低值是（36.96±14.90,24.80~73.80）mmHg;PuvCO₂平均值是（41.04±6.44)mmHg。虽然有着较大的个体差异,但 PuvO₂平均值、最高值和最低值均显著较PuaO₂高（P<0.05）;PuvCO₂虽略低于PuaCO₂,但无显著差异（P>0.05）。结论: 胎儿娩出为新生儿后自主呼吸前PuaO₂随时间（心跳次数）逐渐降低,在达到触发呼吸的阈值时诱发第一次吸气,从而开始自主呼吸。     

新生儿首次呼吸前后脐带动静脉血液氧和二氧化碳变化探索呼吸调控机制的初步报告II—同一个新生儿同一时间的脐带动静脉血液氧和二氧化碳分压差值个体化分析*

目的: 为探讨新生儿自主呼吸产生机制,前文已对新生儿出生后自主呼吸开始前脐带动静脉氧气和二氧化碳差值进行了人群组间分析;而本部分则对相关信息进行个体化分析。方法: 在产前经所有胎儿父母签署知情同意书,新生儿出生后还没有呼吸之前在脐带动脉和脐带静脉分别连续逐搏取血,仅有3例同时采集到Pua和Puv血液样本进行血气分析测定,计算分析脐带静脉和脐带动脉的异同和动态变化。结果: 虽然准备了数十产妇,但仅有3例同时采集到Pua和Puv血液样本,同一时间的PuvO₂显著高于PuaO₂（P均<0.01）,平均相差（24.17±7.09） mmHg;而PuvCO₂显著低于PuaCO₂（P均<0.01）,平均相差（-7.67±3.70） mmHg。在同一时间的Puv-uaO₂显著高于Puv-uaCO₂（P<0.05）。结论: 新生儿出生后自主呼吸前,全部氧气供应由脐带静脉运输,只要胎盘开始剥离则新生儿的PuaO₂随时间（心跳次数）逐渐降低,当PuaO₂达到触发呼吸阈值（最低值）诱发第一次吸气开始其自主呼吸。     

Association between ABCB1 gene polymorphisms and fentanyl's adverse effects in Turkish patients undergoing spinal anesthesia

The ATP-binding cassette transporter (ABCB1) gene product, P-glycoprotein plays an important role in the prevention of intracellular accumulation of potentially toxic substances and metabolites in various tissues. Single nucleotide polymorphisms in this gene are claimed to be correlated with changes in the function of P-glycoprotein. There is evidence that fentanyl, may be a substrate for P-glycoprotein. The aim of the study was to assess whether an association exists between ABCB1 gene polymorphism and early respiratory and sedative adverse effects of intravenous fentanyl in Turkish patients who underwent spinal anesthesiaIn all 83 unrelated Turkish patients were enrolled in this study. In this study, spinal anesthesia was provided and a single dose of intravenous fentanyl (2.5 μg.kg⁻¹) at the beginning of surgery was used as a sedative agent. Bispectral index, respiration rate and peripheral oxygen saturation were measured continuously and recorded throughout the study.The allele and genotype frequencies were similar to previous data from Turkish population.Respiratory rate (RR) and SpO₂ parameters of the patients did not show any significant difference according to the genotype distribution for C1236T and C3435T SNPs. Fentanyl-induced decrease in respiration rate was most remarkable at 15 min (23%) in CC genotype of C1236T, whereas in TT genotype of C3435T (18%) polymorphism. SpO₂ parameters in allele distribution were also not significant among the groups (p = 0.374, p = 0.985, respectively). For the C1236T polymorphism, patients carrying T allele showed a significant decrease in pH, and a significant increase in pCO₂ (p < 0.001).ABCB1 polymorphisms did not seem to have a significant effect on sedation and respiratory depression caused by intravenous fentanyl in spinal anesthesia in Turkish patients.