进食淡水鱼对洞庭湖区人群血脂的影响

目的 :探讨淡水鱼在预防高脂血症中的价值。方法 :以长年生活在渔船上的渔民为试验组 ,当地农民为对照组。采空腹 12 h晨血检测血清胆固醇 (TC) ,甘油三酯 (TG) ,高密度脂蛋白 (HDL) ,载脂蛋白 A(apo A)和载脂蛋白 B(apo B)含量 ,然后对上述各项指标进行 t检验。结果 :试验组 TC、TG、apo B水平较对照组低 (P<0 .0 1) ,而 HDL、apo A及 apo A/ apo B比值较对照组明显升高 (P<0 .0 1)。结论 :长期进食淡水鱼能有效地调节血脂水平 ,这可能不失为一种有待开发的有效的冠心病一级预防措施。     

重症监护室患者血脂与血清内毒素及炎性因子水平的关系

目的:探讨重症监护室(ICU)患者脂质代谢特点及其与血清内毒素(LPS)、炎性因子水平及预后的关系。方法:选取ICU非脓毒症患者90例为观察组,45例同龄健康体检者作为对照组,2组均剔除原发性高脂血症及近期服用过对血脂代谢有影响的药物患者。观察组在入ICU后24 h内采静脉血检测血脂指标及血清LPS、C反应蛋白(CRP)、白介素-6(IL-6)及肿瘤坏死因子-α(TNF-α)水平,并进行急性生理与慢性健康状况评估(APACHEⅡ)评分。根据观察组患者血脂水平将其分为血脂异常组(63例)及血脂正常组(27例),比较2组患者血清LPS及炎性因子水平。分析观察组患者感染情况、住院天数及病死率。结果:观察组患者血清总胆固醇(TC)、低密度脂蛋白(LDL)、高密度脂蛋白(HDL)水平较对照组明显降低,而血清甘油三酯(TG)水平较对照组明显升高(均P 0. 01)。与血脂正常组比较,血脂异常组患者APACHEⅡ评分、血清白细胞计数(WBC)、CRP、IL-6及TNF-α水平明显升高(P 0. 05或P 0. 01);患者感染率(74. 60%)及ICU住院天数[(19. 41±14. 82) d]明显升高(均P 0. 05)。观察组患者血清TC、LDL及HDL水平与APACHEⅡ评分呈负相关(r=-0. 75,-0. 462,-0. 357,均P 0. 01),血清TG水平与WBC、CRP、IL-6及TNF-α呈正相关(r=0. 493,0. 590,0. 357,0. 224,P 0. 05或P 0. 01)。结论:ICU大部分非脓毒症患者存在明显的脂质代谢紊乱并伴有机体炎性水平的升高,血脂代谢异常与APACHEⅡ评分及炎性因子有一定的相关性并影响患者的预后。     

辛伐他汀对高脂血症性脂肪肝治疗的实验研究

目的　探讨调脂药辛伐他汀对高脂血症性脂肪肝的作用。方法　通过高脂食饵饲养制备大鼠高脂血症性脂肪肝模型 ,分别检测模型组 (n =10 )和对照组 (n =10 )的肝指数 (肝重 /体重 )、肝功能、血脂、肝脂、血清、肝组织丙二醛 (MDA)含量及肝组织学改变。模型组剩余 2 0只大鼠随机分为两组 ,治疗组给予辛伐他汀 4mg/kg灌胃 ,每日 1次 ,4周后检测上述指标 ,并与未治疗组比较分析。 结果　高脂血症性脂肪肝模型肝指数、血脂、肝脂、血清及肝组织MDA含量显著升高 (P均 <0 .0 1) ,血脂与血清MDA含量呈正相关 (P <0 .0 1)。肝组织学呈轻、中度脂肪变 ,以小泡性脂滴为主 ;辛伐他汀治疗组血脂、肝脂、血清MDA含量显著降低 (P均 <0 .0 1) ,肝组织MDA含量降低 (P <0 .0 5 ) ,肝组织学接近正常。未治疗组肝脂有所降低 ,肝组织学有改善 ,但血脂增高持续存在。结论　辛伐他汀可安全、有效地用于高脂血症性脂肪肝的治疗。     

不同类型高脂血症小而密低密度脂蛋白的水平及调血脂治疗对其影响

目的 :研究不同类型高脂血症患者血清小而密低密度脂蛋白胆固醇 (LDL C)水平的变化 ,观察血脂康调血脂治疗对高脂血症患者小而密LDL C的影响。方法 :采用非变型梯度凝胶电泳法分别测定 37例冠状动脉 (冠脉 )正常的高脂血症患者 (A组 ) ,131例冠脉造影证实有冠心病的高脂血症患者 (B组 )及 40例冠脉及血脂均正常的受检者 (对照组 )和 80例血脂正常的冠心病患者 (C组 )血清小而密LDL C的水平 ,比较A、B和C组间小而密LDL C水平的差异 ;将B组分为 3个亚组即 40例高胆固醇血症患者 (B1组 )、49例混合型高脂血症患者 (B2组 )、42例高甘油三酯血症患者 (B3组 ) ,给予调血脂治疗 8周 ,分别测定治疗前后该 3个亚组血清小而密LDL C的水平 ,并与对照组对比。结果 :与对照组相比 ,A组患者血清小而密LDL C占总LDL C含量的百分比仅有轻度升高 [(45 5± 5 5 ) %比(40 6± 6 3) % ,P >0 0 5 ] ,B组和C组患者血清小而密LDL C的含量明显升高 [(65 8± 8 2 ) %和 (68 3± 13 8) % ,P <0 0 1]。B组中以B 2组 [(65 7± 7 8) % ,P <0 0 1]和B3组 [(69 3± 7 8) % ,P <0 0 1]患者升高最为明显。调血脂治疗后血清小而密LDL C实际含量均较治疗前显著下降。结论 :合并有冠心病的高脂血症患者小而密LDL C的升高更为明显 ,     

药物干预对大鼠急性心肌梗死组织肾素-血管紧张素系统的影响

目的 :观察氯沙坦、培多普利对大鼠急性心肌梗死 (AMI)后组织肾素 血管紧张素系统 (RAS)的影响。方法 :结扎左冠状动脉制作AMI模型 ,随机分为对照组 (C组 ) ,氯沙坦组 (L组 ) ,培多普利组 (P组 ) ,氯沙坦加培多普利组 (LP组 ) ,假手术组 (S组 )。 3d、1和 6周后观察心脏组织血管紧张素Ⅱ (AngⅡ )、血管紧张素转化酶 (ACE)、左心室梗死区和非梗死区AngⅡ 1型受体 (AT1R)和AT2 RmRNA表达的变化。结果 :①C组和L组非梗死区心肌组织AngⅡ含量均显著高于S组 (均P <0 .0 1) ,P组和LP组非梗死区心肌组织AngⅡ含量和ACE水平均显著低于C组和L组 (P <0 .0 1)。②AT1RmRNA表达率 :术后 3d ,4个MI组梗死区均明显增高 (P <0 .0 1) ,1周时 ,非梗死区C和P组显著高于S组 (均 P <0 .0 1) ,梗死区C和P组 (P<0 .0 1)及L和LP组 (P<0 .0 1)显著增高。 6周时 ,非梗死区和梗死区C和P组显著增高 (P <0 .0 1)。③AT2 RmRNA表达率 :3d时 ,梗死区 4个MI组显著增高 (P <0 .0 5 ) ;1周和 6周 ,4个MI组非梗死区 (C组和P组 :P <0 .0 5 ;L组和LP组 :P<0 .0 1)和梗死区 (P <0 .0 1)均显著增高 ;1周时L组梗死区和非梗死区显著高于C组和P组 (P <0 .0 5 ) ;6周时L组和P组在梗死区和非梗死区显著高于C组和P组 (P <0 .0 5 )。结论 :氯沙坦、培     

人体甲状腺激素与血清瘦素含量的关系

目的　探讨人体甲状腺激素与血清瘦素含量的关系。方法　将 5 3例甲状腺机能障碍初诊患者按照病情分为甲状腺机能亢进组 (甲亢组 )和甲状腺机能减退组 (甲减组 ) ,测定血清瘦素含量及其它有关指标 ,并与 44例健康者 (对照组 )进行比较 ;在瘦素与甲状腺激素、血脂、体重指数 (BMI)和腰 /臀比值 (WHR)之间分别作直线相关分析和多因素回归分析。结果　正常组男性瘦素含量高于甲亢组男性但低于甲减组男性 (P <0 .0 5 ) ,甲亢组男性瘦素含量低于甲减组男性 (P <0 .0 0 1) ;正常组女性瘦素含量与甲亢组女性无显著性差异 (P >0 .0 5 )但低于甲减组女性 (P <0 .0 1) ,甲亢组女性血清瘦素含量与甲减组女性相比较明显降低 (P <0 .0 1) ,直线相关分析结果显示 :男性患者瘦素含量与BMI、WHR、甘油三酯 (TG)呈正相关 (P <0 .0 5～ 0 .0 1) ,女性患者瘦素含量与BMI、WHR、胆固醇 (Ch)、TG呈正相关 (P <0 .0 5～ 0 .0 1) ;多因素回归分析结果显示 ,BMI、WHR与甲状腺机能障碍男、女性患者血清瘦素含量独立相关 (P <0 .0 5～ 0 .0 1)。结论　甲状腺机能障碍患者存在血清瘦素含量的变化 ,但未发现与甲状腺激素含量变化有直接关系     

肺炎衣原体感染与冠心病相互关系的研究

目的 :探讨肺炎衣原体 ( CP)感染与冠心病 ( CHD)的相互关系及其对脂质代谢的影响。方法 :用多聚酶链反应 ( PCR)技术测定 5 4例 CHD患者 ( CHD组 )及 2 0例健康体检者 (对照组 )血清 CP,同时用全自动生化分析仪测定血清总胆固醇 ( TC)、甘油三酯 ( TG)、载脂蛋白 A、载脂蛋白 B浓度。结果 :CHD组 CP阳性率为 74 % ,与对照组 2 5 %相比差异有非常显著性意义 ( P <0 .0 1) ;CP阳性的 CHD患者血清 TC、TG浓度明显高于 CP阴性患者 ( P <0 .0 1)。结论 :CHD患者 CP感染率明显增高 ,CP可能通过引起脂质代谢异常而增加 CHD的危险性。     

阿藿烯对老年大鼠血脂及脂质过氧化作用的影响

目的研究阿藿烯对老年大鼠血脂及其脂质过氧化的影响。方法将12月龄雄性大鼠随机分为正常对照组、高阿藿烯组、中阿藿烯组和低阿藿烯组,分别灌胃加入50、25和12.5mg/kg的阿藿烯,4w末处死动物,检测血清TG、TC、LDL-C及HDL-C水平,测定SOD活性和MDA含量。结果高阿藿烯组、中阿藿烯组和低阿藿烯组血清TC水平下降,血清SOD活性增高(P0.01或P0.05);高阿藿烯组和中阿藿烯组LDL-C和MDA水平显著降低,HDL-C含量明显升高(P0.01或P0.05)。结论阿藿烯能够降低老年大鼠血脂水平,并减轻脂质过氧化作用。     

血脂康对高脂血症患者血小板活性及纤溶活性的影响

目的　探讨高脂血症患者血小板活性及纤溶活性的改变 ,观察血脂康对血小板活性和纤溶活性的影响。方法　选择 30例混合型高脂血症患者和 2 0例健康者 ,测定其血浆血小板 α-颗粒膜蛋白 14 0 (GMP- 14 0 )含量、血浆组织型纤溶酶原激活物 (t- PA)、t- PA抑制物 (PAI)活性及血脂指标。患者口服血脂康 8周后 ,比较治疗前后血浆 GMP- 14 0含量、t- PA、PAI活性及血清血脂的变化。结果　与对照组比较 ,患者组治疗前血清 TC、TG、低密度脂蛋白胆固醇 (L DL- C)明显增高 (P均 <0 .0 1) ,高密度脂蛋白胆固醇 (HDL- C)降低 (P <0 .0 1)。血浆GMP- 14 0含量、PAI活性明显升高 (P均 <0 .0 1) ,t- PA活性降低 (P <0 .0 1)。经血脂康治疗 8周后 ,患者组血清TC、TG、L DL - C明显降低 (P均 <0 .0 1) ,HDL - C升高 (P <0 .0 5 ) ,血浆 GMP- 14 0含量明显下降 (P <0 .0 1) ,t-PA及 PAI活性无显著改善 (P >0 .0 5 )。PAI活性与血清 TG呈正相关 (r=0 .4 6 ,P <0 .0 5 )。结论　高脂血症患者血小板活性明显增加 ,GMP- 14 0含量升高 ,纤溶活性明显降低。血脂康通过降低血清 TC、TG及 L DL - C,抑制血小板活化 ,减少血小板标志物 GMP- 14 0的表达 ,但对纤溶活性无明显影响     

原发性高血压患者血管紧张素Ⅱ和一氧化氮含量变化及与动态血压节律的关系

目的 :探讨原发性高血压 (EH)患者血浆血管紧张素Ⅱ (AngⅡ )、血清一氧化氮 (NO)含量变化及其与血压昼夜节律的相关性。方法 :EH组 5 0例 ,对照组 38例 ,以特异性放射免疫分析法测定血浆AngⅡ水平 ,用硝酸还原酶法经比色法测定血清NO水平 ,采用无创性携带式动态血压监测仪监测动态血压 ,超声心动图测定左室结构。将EH患者按动态血压监测结果分为杓型和非杓型者。比较两者的血压变化规律。结果 :①EH患者血浆AngⅡ含量明显高于对照组 (P <0 .0 1) ,NO含量明显低于对照组 (P <0 .0 1) ,且与病情严重程度相平行。②EH患者血浆AngⅡ与NO负相关 (r =- 0 .4 999,P <0 .0 1)。③非杓型者夜间收缩压均值、夜间舒张压均值增高 ,AngⅡ明显增加 ,NO明显降低 ,左室重量明显增加 ;夜间血压下降与AngⅡ负相关 (r =- 0 4 2 1,P <0 .0 5 ) ,与NO正相关 (r =0 .30 5 ,P <0 .0 5 )。结论 :AngⅡ、NO分泌失衡共同参与EH的发生、发展以及血压昼夜节律的调节。     

Three layer functional model and energy exchange concept of aging process

Relying on a certain degree of abstraction, we can propose that no particular distinction exists between animate or living matter and inanimate matter. While focusing attention on some specifics, the dividing line between the two can be drawn. The most apparent distinction is in the level of structural and functional organization with the dissimilar streams of ‘energy flow’ between the observed entity and the surrounding environment. In essence, living matter is created from inanimate matter which is organized to contain internal intense energy processes and maintain lower intensity energy exchange processes with the environment. Taking internal and external energy processes into account, we contend in this paper that living matter can be referred to as matter of dissipative structure, with this structure assumed to be a common quality of all living creatures and living matter in general. Interruption of internal energy conversion processes and terminating the controlled energy exchange with the environment leads to degeneration of dissipative structure and reduction of the same to inanimate matter, (gas, liquid and/or solid inanimate substances), and ultimately what can be called ‘death.’ This concept of what we call dissipative nature can be extended from living organisms to social groups of animals, to mankind. An analogy based on the organization of matter provides a basis for a functional model of living entities. The models relies on the parallels among the three central structures of any cell (nucleus, cytoplasm and outer membrane) and the human body (central organs, body fluids along with the connective tissues, and external skin integument). This three-part structural organization may be observed almost universally in nature. It can be observed from the atomic structure to the planetary and intergalactic organizations. This similarity is corroborated by the membrane theory applied to living organisms. According to the energy nature of living matter and the proposed functional model, the decreased integrity of a human body's external envelope membrane is a first cause of the structural degradation and aging of the entire organism. The aging process than progresses externally to internally, as in single cell organisms, suggesting that much of the efforts towards the restoration and maintenance of the mechanisms responsible for structural development should be focused accordingly, on the membrane, i.e., the skin. Numerous reports indicate that all parts of the human body, like: bones, blood with blood vessels, muscles, skin, and so on, have some ability for restoration. Therefore, actual revival of not only aging tissue of the human body's membrane, but the entire human body enclosed within, with all internal organs, might be expected. We assess several aging theories within the context of our model and provide suggestions on how to activate the body's own anti-aging mechanisms and increase longevity. This paper presents some analogies and some distinctions that exist between the living dissipative structure matter and inanimate matter, discusses the aging process and proposes certain aging reversal solutions.     

Unusual responses of nocturnal pineal melatonin synthesis and secretion to swimming: Attempts to define mechanisms

Abstract: The effect of swimming at night on rat pineal melatonin synthesis was compared with that of light exposure at night. Rats were forced to swim at 0030 hr (lights out at 2000 hr) and sacrificed by decapitation 15 and 30 min later, immediately after swimming. Other groups of animals were exposed to white light (650μW/cm²) for 15 and 30 min at same time. Swimming caused a rapid and highly significant drop in the melatonin content in the pineal gland; however, the activity of N-acetyltransferase (NAT), the supposed rate limiting enzyme in the melatonin production, was not changed. Despite the drop in pineal melatonin levels, serum concentrations of the indole remained elevated in the rats that swam. In contrast, melatonin levels in the pineal and serum of light exposed rats fell precipitously, accompanied by a significant suppression of NAT activity. Since we anticipated that the strenuous exercise associated with swimming may induce release of artrial natriuretic peptide (ANP) from the heart, which in turn could cause the release of pineal melatonin, in a second study we injected physiological saline intravenously to stretch the cardiac muscle and release ANP. Three milliliters of normal saline was injected during the day into the jugular vein of anesthetized rats that were pretreated with isoproterenol to stimulate pineal melatonin production. Animals were killed 15 min after the saline injection, and pineal NAT activity and pineal melatonin levels were measured. The saline injections caused no alteration in the elevated levels of either NAT or melatonin. These data suggest that the disparity in pineal NAT activity (which was high) and pineal melatonin (which was low), in animals swum at night, may not be caused by ANP which is released during strenuous exercise such as swimming.     

Melatonin and photoperiodic time measurement: Seasonal breeding in the sheep

Abstract: Well-established circadian physiology supports the view that photoperiodic time measurement utilizes the coincidence between the presence of light and a photosensitive phase of a 'biological clock' to alter reproductive status—the so-called external coincidence model of seasonal breeding. In this review, we examine the mechanism whereby photoperiod interacts with presumed suprachiasmatic nuclei activity to allow endogenous melatonin to normally synchronize reproductive activity to the optimal time of year. The Romney Marsh sheep is particularly explored as an experimental model. It is suggested that the on/off activity of seasonal reproduction may be a robust mechanism able to be predictably manipulated by the judicious use of the light/dark cycle and exogenous melatonin, but firmly based on circadian principles.     

Serological survey of HIV and syphilis in pregnant women in Madagascar

Objectives Peripartal transmission of human immunodeficiency virus (HIV) and Treponema pallidum, the causative agent of syphilis, leads to severe consequences for newborns. Preventive measures require awareness of the maternal infection. Although HIV and syphilis testing in Madagascar could be theoretically carried out within the framework of the national pregnancy follow‐up scheme, the required test kits are rarely available at peripheral health centres. In this study, we screened blood samples of pregnant Madagascan women for HIV and syphilis seroprevalence to estimate the demand for systemic screening in pregnancy. Methods Retrospective anonymous serological analysis for HIV and syphilis was performed in plasma samples from 1232 pregnant women that were taken between May and July 2010 in Ambositra, Ifanadiana, Manakara, Mananjary, Moramanga and Tsiroanomandidy (Madagascar) during pregnancy follow‐up. Screening was based on Treponema pallidum haemagglutination tests for syphilis and rapid tests for HIV, with confirmation of positive screening results on line assays. Results Out of 1232 pregnant women, none were seropositive for HIV and 37 (3%) were seropositive for Treponema pallidum. Conclusions Our findings are in line with previous studies that describe considerable syphilis prevalence in the rural Madagascan population. The results suggest a need for screening to prevent peripartal Treponema pallidum transmission, while HIV is still rare. If they are known, Treponema pallidum infections can be easily, safely and inexpensively treated even in pregnancy to reduce the risk of transmission.     

Variabilité des concentrations plasmatiques de l’angiotensinogène et risque d’hypertension artérielle chez le rat transgénique

Aim

Genetic polymorphisms of the human angiotensinogen gene are frequent and may induce up to 30% increase of plasma angiotensinogen concentrations with a blood pressure increase of up to 5 mmHg. Their role for the pathogenesis of human arterial hypertension remains unclear. High plasma angiotensinogen levels could increase the sensitivity to other blood pressure stressors.

Methods

Male transgenic rats with a 9-fold increase of plasma angiotensinogen concentrations and male non-transgenic rats aged 10 weeks were treated or not with NG-Nitro-L-arginine-methyl ester for 3 weeks in their drinking water (n = 3/group). Systolic blood pressure and body weight were measured at baseline and at the end of the study when left ventricular weight and ventricular expression of angiotensin I-converting enzyme and procollagen Iα1 were determined (polymerase chain reaction).

Results

At baseline, transgenic rats had +18 mmHg higher bood pressure and –8% lower body weight compared to non-transgenic rats (P < 0.05) without significant changes for the vehicle groups throughout the study (P > 0.05). NG-Nitro-L-arginine-methyl ester increased blood pressure, left ventricular weight and left ventricular weight indexed for body weight by +41%, +17.6% and +18.6% (P < 0.05) in transgenic and +25%, +5.3% and +6.7% (P > 0.05) in non-transgenic rats compared to untreated animals, respectively. Cardiac gene expression showed no differences between groups (P > 0.05).

Conclusion

Increased plasma angiotensinogen levels may sensitize to additional blood pressure stressors. Our preliminary results point towards an independent role of angiotensinogen in the pathogenesis of human hypertension and associated end-organ damage.     

Morphological and immunocytochemical heterogeneity of cultured pinealocytes from one-week-and two-month-old rats: Planimetric and densitometric investigations

Abstract: In vitro preparations of rat pinealocytes are widely used for biochemical analyses of signal transduction processes. This paper deals with morphological and immunocytochemical features of such preparations. Special attention was paid to the problems of whether pinealocytes represent a heterogeneous cell population and how such heterogeneity may develop during ontogeny. The investigations were performed with cells which were obtained from the pineal organ of one-week-and two-month-old rats, attached to synthetic peptide-coated coverslips or tissue culture chamber slides, and maintained under in vitro conditions overnight. The attached cells were then fixed with paraformaldehyde. These preparations yielded monolayers of spherical cells of different sizes; most cells were isolated, but some of them were aggregated and formed small clusters. On the average, the cells from the one-week-old animals were smaller than the cells from the two-month-old animals. Immunocytochemical demonstration of S-antigen, a pinealocyte-specific marker, showed that the majority of the cells from two-month-old animals were intensely or moderately labelled. Pinealocytes from one-week-old animals were less S-antigen immunoreactive. Only very few cells (less than 1% displayed glial fibrillary acidic protein (GFAP)-immunoreactivity. Planimetric investigations of the cell size and semiquantitative densitometric investigations of the intensity of the S-antigen immunoreaction revealed that (i) pinealocytes kept in vitro form a heterogeneous cell population, and that (ii) this heterogeneity increases during postnatal development from one-week-old to two-month-old animals. Two groups of pinealocytes can be distinguished based on their developmental fate: pinealocytes of one group grow dramatically, but show only a moderate increase in S-antigen immunoreactivity, and pinealocytes of the other group retain their size, but display a distinct increment in S-antigen immunoreacti vitv.     

Effects of pinealectomy and melatonin administration on certain indices of ovarian hyperplasia and/or hypertrophy in rats with both ovaries intact or after unilateral ovariectomy

Abstract: In earlier studies from other laboratories it was shown that melatonin decreased ovarian weight in rats and inhibited compensatory hypertrophy of the remaining ovary after unilateral ovariectomy. This study was designed to examine the influence of melatonin on certain indices of ovarian hyperplasia and/or hypertrophy in adult female rats with both ovaries preserved and with either an intact pineal gland or with the pineal gland removed (pinealectomy, PX) or, finally, in sham-PX animals. Similar studies were conducted on rats after unilateral ovariectomy, referring the examined parameters to the remaining intact ovary. The studies included mitotic activity of granulosa layer cells and corpus luteum cells, ovarian weight, ovarian cross-sectional area, cross-sectional area of the granulosa layer of all the Graafian follicles and the cross-sectional areas of the corpora lutea, visible on the ovarian cross-section. On the basis of results, we conclude that: 1) the effect of PX on the processes of ovarian hyperplasia and hypertrophy may vary; analogously, exogenous melatonin administration may influence ovarian hyperplasia and hypertrophy in different ways; 2) PX and exogenous melatonin may, under certain conditions, exert similar biological effects, even synergistic effects; 3) melatonin inhibits ovarian growth processes, while the effects of PX are variable; 4) the results indicate that in experiments performed on rats, with the use of two control groups, i.e., intact and sham-PX, melatonin effects on these two groups may differ.