磁处理水对家兔血脂影响的实验研究

目的:探讨饮用磁处理水时间的长短与降低家兔血脂的关系。方法:72只家兔平均分四组A组基础饲料组,饮自来水;B、C、D高脂饲料组,B组对照组饮自来水;C组治疗1组,30天后饮磁处理水,治疗30天后采耳血,分别测血清TC、TG、HDL-c、LDL-c水平。D组治疗2组,30天后饮磁处理水,治疗100天后采耳血,分别测血清TC、TG、HDL-c、LDL-c水平。结果:B组家兔血清TC、TG、HDL-c、LDL-c水平显著高于A组,(P<0.01);C组家兔TC、LDL-c水平显著低与B组(P<0.01);,但也显著高于A组(P<0.01);TG、HDL-c水平与B组相比无显著差异(P>0.05)。D组家兔血清TC、TG、LDL-c水平与B组相比均有明显下降(P<0.01),与A组比较差异无显著性(P>0.05),而HDL-c水平与A组比较明显上升(P<0.01)。结论:长期饮用磁处理水可以显著降低家兔血清高胆固醇含量,并恢复到正常状态。     

低密度脂蛋白胆固醇升高在家兔动脉粥样硬化发生发展中的意义

目的：观察低密度脂蛋白胆固醇（LDL-c）对家兔动脉粥样硬化（AS）形成的影响,探讨AS的发生机制.方法：以高脂饲料复制家兔实验性AS模型,分阶段检测家兔血清胆固醇（TC）、甘油三脂（TG）、高密度脂蛋白胆固醇（HDL-c）和低密度脂蛋白胆固醇（LDL-c）含量;观察主动脉内膜病理学变化;分析主动脉内膜增生程度及AS斑块面积与血浆脂蛋白水平的相关性.结果：高脂组家兔主动脉粥样硬化面积和内膜增生程度明显较对照组增加（P〈0.01）,血浆LDL-c水平明显较对照组升高（P〈0.01）;动脉内膜增生程度及AS斑块面积均与血浆LDL-c水平呈非常显著正相关（r=0.837,P〈0.001）.结论：提示血浆LDL-c水平升高,是致AS发生发展的重要原因.     

2型糖尿病患者颈动脉粥样硬化与血尿酸水平的相关性研究

目的：探讨2型糖尿病（T2DM）患者颈动脉粥样硬化与血尿酸水平的相关性。方法：测定214例T2DM患者血清尿酸、血脂、糖化血红蛋白水平及颈动脉中层内膜厚度（IMT）,按颈动脉IMT分为4组：A组：无动脉粥样硬化组;B组：动脉粥样硬化组,C组：斑块形成组,D组：管腔狭窄组。比较各组生化指标,并分析颈动脉粥样硬化与血清尿酸水平的相关性。结果：各组性别、年龄、TC、HDL、LDL无显著差异;C组血清TG水平较A组低（P=0.02）,D组血清HbA1c水平较A组（P=0.038）及B组（P=0.015）显著降低。D组血清尿酸水平与A组相比显著升高（P=0.001）,但D组与B、C组及A组与B、C组间差异均无统计学意义;相关分析显示颈动脉粥样硬化程度与血清尿酸水平呈显著正相关（P=0.002）,相关系数为0.201。结论：高血清尿酸水平可能是导致T2DM患者颈动脉粥样硬化的危险因素之一,需慎重处理T2DM患者高尿酸血症问题。     

脂负荷性饵食对家兔脂代谢的影响

目的探讨建立兔饵食性高脂血症模型的方法,观察高脂饮食对兔体重、死亡率及血脂变化情况。方法取普通级雄性新西兰大耳白兔,其中随机抽取10只作为普通饮食组,喂以普通饮食;其他动物给予高脂饮食,4周后,根据血清TC水平分为高脂饮食敏感组和高脂饮食非敏感组,继续喂养9周,观察三组间兔血清总胆固醇（TC）、甘油三脂（TG）、高密度脂蛋白胆固醇（HDL-C）和低密度脂蛋白胆固醇（LDL-C）的变化。结果与普通饮食组相比,高脂饮食敏感组在第4～13周时血清TC、TG、HDL-C、LDL-C水平显著升高（P〈0.01）,高脂饮食非敏感组在第7～13周时,动物血清TC、HDL-C、LDL-C水平显著升高（P〈0.01）,而高脂饮食非敏感组血清TG水平的改变无统计学意义（P〉0.05）。与高脂饮食敏感组相比,高脂饮食非敏感组家兔血清TC、TG、HDL-C和LDL-C水平的上升程度均显著低于高脂饮食敏感组动物（P〈0.01）。结论首次发现兔对高脂饮食敏感性存在差异,高脂饮食非敏感组家兔抗病能力、对环境的适应能力和耐受性均高于高脂饮食敏感组兔。与高脂饮食敏感组家兔相比,高脂饮食非敏感组家兔对高脂饮食耐受性强。     

不同脂肪高脂日粮诱发胰岛素抵抗综合征大鼠模型的比较

目的分析猪油、豆油、氢化椰子油、乳脂四种不同脂肪的高脂日粮分别诱发胰岛素抵抗综合征（IRS）大鼠的血液生化指标差异,为此类模型的建立及实验研究提供参考。方法雄性SD大鼠随机分为5组,对照组给予普通日粮,高脂组给予脂肪热量比相同的高脂日粮。喂养6周,每两周测定空腹血糖、甘油三酯（TG）、高密度脂蛋白胆固醇（HDL-c）、总胆固醇（TC）、胰岛素,根据胰岛素敏感性指数（ISI）=ln1/（FPG×FINS）评定大鼠的胰岛素敏感性。结果6周后,猪油组、乳脂组、豆油组血清胰岛素均显著高于对照组（P〈0.05）;乳脂组血清TG显著高于其它高脂组（P〈0.05）;高脂组血清HDL-c均显著低于对照组（P〈0.05）并以豆油组下降幅度最大;猪油组、乳脂组ISI显著低于对照组（P〈0.05）;而各组间血清总胆固醇、血糖及体重无明显差异（P〉0.05）。结论4种高脂日粮诱发IRS大鼠模型的综合效果依次为乳脂、猪油、豆油、氢化椰子油。     

低密度脂蛋白胆固醇升高在家兔动脉粥样硬化发生发展中的意义

目的观察低密度脂蛋白胆固醇(LDL-c)对家兔动脉粥样硬化(AS)形成的影响,探讨AS的发生机制。方法以高脂饲料复制家兔实验性AS模型,分阶段检测家兔血清胆固醇(TC)、甘油三脂(TG)、高密度脂蛋白胆固醇(HDL-c)和低密度脂蛋白胆固醇(LDL-c)含量;观察主动脉内膜病理学变化;分析主动脉内膜增生程度及AS斑块面积与血浆脂蛋白水平的相关性。结果高脂组家兔主动脉粥样硬化面积和内膜增生程度明显较对照组增加(P<0.01),血浆LDL-c水平明显较对照组升高(P<0.01);动脉内膜增生程度及AS斑块面积均与血浆LDL-c水平呈非常显著正相关(r=0.837,P<0.001)。结论提示血浆LDL-c水平升高,是致AS发生发展的重要原因。     

非酒精性脂肪性肝病与MTP关系的实验研究

目的：探讨非酒精性脂肪性肝病( Non-alcoholic fatty liver disease, NAFLD)与微粒体甘油三酯转运蛋白(microsomal triglyceridetransfer protein,MTP）的关系。方法：将雄性Wistar 大鼠60只随机分为正常对照组（A 组）、高脂组（B 组）和MTP 抑制剂组（C 组）,每组各20 只。B 组、C组给予高脂饲料喂养,8 周后确认非酒精性脂肪肝建模成功,C组大鼠给予混有特异性小肠MTP抑制 剂JTT-130 的高脂饲料喂养,B 组大鼠建模过程始终喂养高脂饲料,A 组大鼠喂养普通饲料。于第12周,分别测定大鼠血清甘油 三酯(triglyceride,TG)、总胆固醇(total cholesterol,TC)、高密度脂蛋白胆固醇(high density lipoprotein-cholesterol,HDL-c)含量,以及 肝脏TC、TG、磷脂含量。同时测定肝脏中微粒体甘油三酯转运蛋白(MTP) 的活性与mRNA 表达量。结果：与正常对照组（A组）相 比,高脂组（B组）大鼠血清TC、TG、HDL-c 浓度和肝脏TC、TG含量明显提高（P＜0.05）,MTP 活性及mRNA 水平明显下调（P＜ 0.05）。与高脂组（B 组）比较,MTP 抑制剂组（C 组）大鼠血清TC、TG、HDL-c 浓度和肝脏TC、TG 含量明显下降（P＜0.05）,而 MTP 活性及mRNA 表达量比较无明显差别（P＞0.05）。结论：非酒精性脂肪性肝病存在MTP表达下调,特异性小肠MTP 抑制剂 JTT-130 可以有效抑制肠道对TG的转运,不影响肝脏TG分泌,并在降低高脂大鼠血浆TG和胆固醇水平的同时也降低肝脏TG 含量。     

肝康Ⅳ号对脂肪肝大鼠肝组织脂质含量及形态学的影响

目的探讨肝康Ⅳ号（Gankang Ⅳ,GKⅣ）对脂肪肝（FL）组织胆固醇（TC）、甘油三脂（TG）、超氧化物歧化酶（SOD）、丙二醛（MDA）及形态学的影响。方法64只SPF级Wistar大鼠,随机分为A组、B1组、B2组、B3组、C组、D组。A组、B1组、B2组、B3组、C组给予高脂饲料（84.4%标准饲料＋10%猪油＋0.5%胆固醇＋0.1%胆盐＋5%蛋黄粉）和白酒复合复制大鼠FL模型,B1组、B2组、B3组、C组分别给予肝康Ⅳ号低、中、高剂量和东宝肝泰灌胃干预,设空白对照D组。第6周末处死动物取肝脏制备10%的肝匀浆检测TC、TG、SOD、MDA。检测肝脏病理学。结果（1）TC、TG：B1组、B2组、B3组、C组与A组比较,TC、TG含量明显下降（P〈0.05～0.01）,B2组、B3组与C组比较差异有显著（P〈0.05）。（2）SOD、MDA：B1组、B2组、B3组、C组与A组比较,MDA含量明显下降（P〈0.05～0.01）,SOD水平明显升高（P〈0.05～0.01）;在SOD方面,B1组与C组比较差异有非常显著性（P〈0.01）,B2组与C组比较差异有显著（P〈0.05）;在MDA方面,B1组、B2组、B3组与C组比较差异有非常显著性（P〈0.01）。（3）肝脏病理学：A组为重度脂肪肝,C组、B1组为中度脂肪肝,B2组、B3组脂肪肝程度轻于C组、B1组。结论GKIV能有效降低肝脏组织脂质沉积,防止MDA的升高,SOD的下降;减轻FL程度,呈现量效关系。     

有氧运动对饮食性高脂血症小鼠血脂改善效果的观察

目的：观察以高脂膳食诱导C57BL／6J小鼠血脂水平的变化以及有氧运动对其的改善作用。方法：以高脂膳食诱导的高脂血症小鼠为模型,分析有氧运动20周后血清TC,TG,HDL-c,LDL-c和VLDL-c水平的变化。结果: 高脂膳食组(H组)血清TC、TG、LDL-c显著高于正常组(N组)、恢复正常膳食组(RS组)和恢复正常膳食结合运动组(RE组)而VLDL-c显著降低;恢复正常膳食结合运动组血清TG、TC、LDL-c的水平显著降低,且与正常对照组没有显著性差异。单纯恢复正常膳食组TG、TC、LDL-C也有所下降。但显著高于正常对照组。结论：研究提示,有氧运动对高脂血症有明显的治疗作用。     

脑梗塞患者血清hs—CRP、TNF-α、血脂水平的变化及其临床意义

目的：观察脑梗塞患者血清超敏C反应蛋白（hs—CRP）、肿瘤坏死因子（TNF-α）及血脂水平的变化。并探讨其临床意义。方法：选择我院2010年6月-2012年6月收治的86例急性脑梗塞患者（轻型脑梗塞组27例、中型脑梗塞组34例、重型脑梗塞组25例）为实验组和同期40例健康体检者为对照组,检测和比较两组血清超敏C反应蛋白（hs-CRP）、肿瘤坏死因子（TNF—α）、甘油三酯（TG）、总胆固醇（TC）、低密度脂蛋白（LDL-C）和高密度脂蛋白（HDL-c）的水平,并进行相关性分析。结果：与健康对照组比较,实验纽血清hs—CRP、TNF-α及TC、TG、LDL—C水平显著升高,而血清HDL-C水平显著降低,差异均具有统计学意义（P〈0．05）。与轻型脑梗塞组比较,中、重型脑梗塞组血清hs-CRP、TNF-α及TC、TG、LDL-C等血脂水平均显著升高,而血清HDL-C水平显著降低,其异均具有统计学意义（P〈0．05）;与中型脑梗塞组比较,重型脑梗塞组血清TC、TG、LDL-C等血脂水平均显著升高,血清HDL—C水平显著降低,其差异亦均具有统计学意义（P〈0．05）。脑梗塞患者血清hs—CRP与TNF-α水平呈显著正相关（P〈0．05）,与TC、TG、LDL—C等血脂水平均亦呈显著正相关（P〈0．05）,与血清HDL—C水平呈显著负相关（P〈O．05）。脑梗塞患者血清hs．CRP、TNF-α水平与病情严重程度呈显著正相关（P〈0．05）。结论：检测血清hs-CRP、TNF-α及血脂指标水平对评估脑梗塞患者病情具有重要的临床意义。     

不同功率的激光刺激对小鼠C2C12成肌细胞耗氧率水平的影响及机制

目的：探讨不同功率的低强度650 nm激光刺激对C₂C₁₂成肌细胞耗氧率水平和相关蛋白的影响及其机制。方法：以体外培养的C₂C₁₂小鼠成肌细胞作为实验对象,以4×10⁵个/孔接种于牵张6孔板中,采用输出功率5 mW,波长650 nm的二极管激光进行单次刺激,激光照射剂量分别0 J/cm²（0 min）、0.4 J/cm²（12.8 min）、0.8 J/cm²（25.6 min）。实验结束后,采用耗氧率试剂盒（Luxcel Biosciences）检测细胞耗氧率;提取细胞总蛋白,采用Western blot技术检测成肌调节因子（MyoD）、过氧化物酶体增殖活化受体γ共激活因子1α（PGC-1α）、雷帕霉素靶蛋白和磷酸化蛋白（p-mTOR/mTOR）表达。结果：与对照组相比,低剂量组细胞氧化耗氧率结果、MyoD、PGC-1α蛋白表达显著增加（P<0.05）,高剂量组MyoD、PGC-1α蛋白表达显著增加（P<0.05）,p-mTOR/mTOR蛋白显著降低（P<0.05）。结论：较低剂量（0.4 J/cm²）的650 nm低强度激光增强了细胞氧化功能水平,并对细胞分化相关蛋白有一定影响。其机制可能与适宜的激光刺激影响PGC-1α蛋白的表达,进而影响线粒体氧化呼吸有关。     

Myosin binding protein C positioned to play a key role in regulation of muscle contraction: structure and interactions of domain C1

Myosin binding protein C (MyBP-C) is a thick filament protein involved in the regulation of muscle contraction. Mutations in the gene for MyBP-C are the second most frequent cause of hypertrophic cardiomyopathy. MyBP-C binds to myosin with two binding sites, one at its C-terminus and another at its N-terminus. The N-terminal binding site, consisting of immunoglobulin domains C1 and C2 connected by a flexible linker, interacts with the S2 segment of myosin in a phosphorylation-regulated manner. It is assumed that the function of MyBP-C is to act as a tether that fixes the S1 heads in a resting position and that phosphorylation releases the S1 heads into an active state. Here, we report the structure and binding properties of domain C1. Using a combination of site-directed mutagenesis and NMR interaction experiments, we identified the binding site of domain C1 in the immediate vicinity of the S1-S2 hinge, very close to the light chains. In addition, we identified a zinc binding site on domain C1 in close proximity to the S2 binding site. Its zinc binding affinity (K_d of approximately 10-20 μM) might not be sufficient for a physiological effect. However, the familial hypertrophic cardiomyopathy-related mutation of one of the zinc ligands, glutamine 210 to histidine, will significantly increase the binding affinity, suggesting that this mutation may affect S2 binding. The close proximity of the C1 binding site to the hinge, the light chains and the S1 heads also provides an explanation for recent observations that (a) shorter fragments of MyBP-C unable to act as a tether still have an effect on the actomyosin ATPase and (b) as to why the myosin head positions in phosphorylated wild-type mice and MyBP-C knockout mice are so different: Domain C1 bound to the S1-S2 hinge is able to manipulate S1 head positions, thus influencing force generation without tether. The potentially extensive extra interactions of C1 are expected to keep it in place, while phosphorylation dislodges the C1-C2 linker and domain C2. As a result, the myosin heads would always be attached to a tether that has phosphorylation-dependent length regulation.     

The C-terminal 26-residue peptide of serpin A1 stimulates proliferation of breast and liver cancer cells: role of protein kinase C and CD47

C26, the C-terminal 26 residue peptide of serpin A1, significantly increased cell proliferation in cultures of hepatoma cells, but not in porcine kidney epithelial cells, human skin fibroblasts or keratinocytes. The mitogenic activity of C26 was preferentially inhibited with a protein kinase C (PKC) inhibitor, an antibody against CD47 and CD47 short interfering RNA. The mutant C26-K19R,N22M, imitating a thrombospondin-like cell adhesion motif, increased the mitogenic activity in both Hep G2 cells and MCF-7 breast cancer cells. Phosphorylation of C26 at T24 (a putative PKC phosphorylation site) resulted in a 1.9-2.5 increase in mitogenic activity over C26 in MCF-7 cells.     

The effect of hydroxyurea and mitomycin C on sperm motility in mice

The mutagen, mitomycin C, and the teratogen, hydroxyurea, were found to decrease sperm motility in mice in a dose-dependent manner. Positive results with these compounds suggest that sperm motility may have been decreased through either mutations or developmental disturbances. Sperm motility can be determined quickly and may be done in conjunction with a sperm-morphology assay.     

Butanolides from Methanolic Extract of Litsea glutinosa

Phytochemical investigations of a MeOH extract obtained from the heartwoods of the Litsea glutinosa (Lauraceae) led to the isolation and characterization of four new butenolides, (3R,4S,5S)‐2‐hexadecyl‐3‐hydroxy‐4‐methylbutanolide 1 , litsealactone C ( 2 ), and litsealactone D ( 4 ), litsealactone G ( 5 ), and a new benzoic acid derivative named eusmoside C ( 3 ). The structures of these compounds were elucidated on the basis of spectral studies.     

Non-linear dynamics of the complement system activation

The complement system (CS) plays a prominent role in the immune defense. The goal of this work is to study the dynamics of activation of the classic and alternative CS pathways based on the method of mathematical modeling. The principal difficulty that hinders modeling effort is the absence of the measured values of kinetic constants of many biochemical reactions forming the CS. To surmount this difficulty, an optimization procedure consisting of constrained minimization of the total protein consumption by the CS was designed. The constraints made use of published data on the in vitro kinetics of elimination of the Borrelia burgdorferi bacteria by the CS. Special features of the problem at hand called for a significant modification of the general constrained optimization procedure to include a mathematical model of the bactericidal effect of the CS in the iterative setting. Determination of the unknown kinetic constants of biochemical reactions forming the CS led to a fully specified mathematical model of the dynamics of cell killing induced by the CS. On the basis of the model, effects of the initial concentrations of complements and their inhibitors on the bactericidal action of the CS were studied. Proteins playing a critical role in the regulation of the bactericidal action of the CS were identified. Results obtained in this work serve as an important stepping stone for the study of functioning of the CS as a whole as well as for developing methods for control of pathogenic processes.     

Origin and evolution of C4 photosynthesis in the tribe Salsoleae (Chenopodiaceae) based on anatomical and biochemical types in leaves and cotyledons

 The Chenopodiaceae genus Salsola contains a large number of species with C₄ photosynthesis. Along with derivative genera they have a prominent position among the desert vegetation of Asia and Africa. About 130 species from Asia and Africa were investigated to determine the occurrence of C₃ versus C₄ syndrome in leaves and cotyledons, and to study specific anatomical and biochemical features of photosynthesis in both photosynthetic organs. The species studied belong to all six previously identified sections of the tribe Salsoleae based on morphological characters. Types of photosynthesis were identified using carbon ¹³C/¹²C isotope fractionation. The representatives of all systematic groups were investigated for mesophyll anatomy and biochemical subtypes by determination of enzyme activity (RUBPC, PEPC, NAD- and NADP-ME and AAT) and primary photosynthetic products. Two photosynthetic types (C₃ and C₄) and two biochemical subtypes (NAD- and NADP-ME) were identified in both leaves and cotyledons. Both Kranz and non-Kranz type anatomy were found in leaves and cotyledons, but cotyledons had more diversity in anatomical structure. Strong relationships between anatomical types and biochemical subtypes in leaves and cotyledons were shown. We found convincing evidence for a similar pattern of structural and biochemical features of photosynthesis in leaves and cotyledons within systematic groups, and evaluated their relevance at the evolutionary level. We identified six groups in tribe Salsoleae with respect to photosynthetic types and mesophyll structure in leaves and cotyledons. Two separate lineages of biochemical and anatomical evolution within Salsoleae were demonstrated based on studies of leaves and cotyledons. The sections Caroxylon, Malpighipila, Cardiandra and Belanthera have no C₃ species and only the NAD-ME C₄ subtype has been found in leaves. We suggest the C₄ species in the NADP-ME lineage evolved in Coccosalsola and Salsola sections, and originated in the subsection Arbuscula. Coccosalsola contains many species with C₃ and/or C₃-C₄ intermediate photosynthesis. Within these main evolutionary lineages, species of different taxonomic groups (sections and subsections) had differences in anatomical or/and biochemical features in leaves and cotyledons. We conclude that structural and biochemical changes in the photosynthetic apparatus in species of the tribe Salsoleae were a key factor in their evolution and broad distribution in extreme desert environments. Received January 25, 2001 Accepted July 17, 2001     

Identification of a novel bifunctional delta12/delta15 fatty acid desaturase from a basidiomycete, Coprinus cinereus TD#822-2

A new gene encoding a delta12 fatty acid desaturase-related protein was cloned from a multicellular basidiomycete Coprinus cinereus TD#822-2. The 1326 bp full-length gene, designated as Cop-odeA, codes for a putative protein of 442 amino acids with a MW of 49224. The Cop-odeA yeast transformant accumulated four new fatty acids identified as 9,12-hexadecadienoic acid, 9,12,15-hexadecatrienoic acid, linoleic acid, and alpha-linolenic acid, which comprised 8.8%, 1.0%, 29.0%, and 0.6% of the total fatty acids, respectively. The Cop-odeA protein was confirmed to be a novel bifunctional fatty acid desaturase with both high delta12 desaturase activity and unusual delta15 desaturase activity.     

Schistosoma mansoni: Role in vivo of complement in primary infection of mice

The role of complement in the control of the primary Schistosoma mansoni infection in mice was investigated in vivo. The number of recovered adult schistosomes 6–7 weeks postinfection was used as a parasitological criterion of immunity. No significant difference in the worm burden was observed between C5-sufficient and C5-deficient mice. In contrast, when cobra venom factor (CVF) was injected into normal or C5-deficient mice 24 hr before challenge, a significant increase of the worm burden was noticed in comparison to the untreated mice. These results indicated that, although C5 and probably the late complement components are not essential for the control of the primary infection, the alternative pathway and some of its components are involved. In fact, the injection of C3 2 hr before infection of CVF-treated mice completely restored the immunity. A role for C3, in association with effector cells, in the nonspecific immunity occurring in the first hours after a primary S. mansoni infection is suggested.     

Photon requirement for O2-Revolution in red (λ= 680 nm) light for some C3 and C4 plants and a C3–C4 intermediate species*

Photon requirements for O₂-evolution in red (λ=680nm) light (Ф_r) were measured for six C₃ species, one C₃-like, C₃–C₄ intermediate species, and three C₄ species, including examples of NADP-malic enzyme and PEP-carboxykinase C₄ sub-groups. Variation in Ф_r within the C₃ species was small with a mean value of 7.96 ±0.12 mol photon mol⁻¹ O₂, whereas the mean value for the C₄ species was 12.27± 1.53 mol photon mol⁻¹ O₂, with the lowest value, 9.24 ±0.13 mol photon mol⁻¹ O₂, for the PEP-carboxykinase C₄ species Spartina townsendii. The C₃–C₄ intermediate species Panicum milioides had a value of 9.05 ±0.29 mol photon mol⁻¹ O₂, approximately 1 mol photon mol⁻¹ O₂ greater than the C₃ species. The possibility that this extra cost is due to PEP-carboxylase-dependent recycling of CO₂ is discussed. No correlation was found between Ф_r and chlorophyll content or leaf absorptance. Based on white (Ф_W) and red light measurements of the photon requirement, values in red light were approximately 20% higher than white-light estimates. These results are discussed with reference to accepted mechanisms of energy transduction in thylakoid membranes (Z-scheme), expected inefficiencies and losses during light-harvesting and electron transport reactions, and the influence of respiratory processes.