Varying susceptibility to myocardial infarction among C57BL/6 mice of different genetic background

Genetically manipulated mouse lines are invaluable to investigate the effects of a single gene on sensitivity to ischemia. When choosing appropriate controls, we were concerned that intrinsic, strain-independent but colony-dependent differences may influence the susceptibility to ischemia. We, therefore, compared the infarct:risk volume ratio (I:R%) after 30-min global ischemia in Langendorff-perfused hearts from outbred C57BL/6 mice with that in wild-type mice derived from heterozygote x heterozygote crosses of two different in-house C57BL/6 mouse lines with targeted disruption of an MKK3 or MAPKAPK2 allele. Despite similar hemodynamic characteristics, I:R% in outbred C57BL/6 hearts was significantlysmaller (40.8 +/- 2.8%) than in C57BL/6 MAPKAPK2 wild types (65.8 +/- 4.5%, P = 0.0003) and significantly larger than in C57BL/6 MKK3 wild types (23.7 +/- 2.9%, P = 0.002). Therefore, inherent colony substrain-dependent differences appear to influence the susceptibility to infarction in response to global ischemia, underscoring the importance of using colony-matched wild-type controls in murine studies of myocardial ischemia.     

Factors affecting the infection of the D variant of encephalomyocarditis virus in the B cells of C57BL/6J mice

Summary The D variant of encephalomyocarditis viras is capable of infecting most inbred strains of mice. However, only certain strains are susceptible to the diabetogenic effect of this viras. In order to understand why some inbred strains do not become diabetic, the pathogenesis of infection was studied in diabetes-resistant C57BL/6J mice. It was the purpose of the investigation to ascertain whether specific host defense factors might play a crucial role in the mechanism of resistance. To determine whether perturbations of the immune response would alter the resistance of these animals, mice were treated with a high dose (1.15 mmol/kg body weight) of the T- and B-cell toxin cyclophosphamide prior to infection with the D variant. This treatment did not induce overt diabetes or glucose intolerance in the mice tested 7 days after infection. Based on this finding, it appeared likely that resistance to the D variant is conveyed by some factor other than cell-mediated immunity. A likely candidate to control this viral infection is the interferon system. To investigate this possibility, C57BL/6J mice were infected with the D variant and the concentrations of serum interferon titred at various intervals thereafter. In contrast to previous reports with diabetes susceptible mice, C57BL/6J mice were found to generate a substantial interferon response against this variant, with peak levels found in the serum at 24 h following infection. Additional studies were performed in which mice were treated with antibody to mouse interferon alpha/beta at the time of infection and again 3 days after infection with the D variant. Sixty percent of the animals treated in this manner became glucose intolerant. The results of these studies indicate that the interferon system is a critical determinant of resistance to the diabetogenic effect of the D variant in C57BL/6J mice.     

旋毛虫抗C57BL/6小鼠体内Hepa1-6肝癌细胞作用的研究

目的观察旋毛虫对C57BL/6小鼠体内Hepa1-6肝癌细胞生长的抑制作用。方法将C57BL/6小鼠随机分成8组,每组10只。第1和5、2和6、3和7组分别感染未处理旋毛虫、^60Co处理和紫外线处理旋毛虫,4和8组为不感染旋毛虫对照组,1～4组和5～8组分别于接种旋毛虫前7 d和接种后11 d接种Hepa1-6肝癌细胞。荷瘤后25 d后处死小鼠,测量肿瘤体积、重量及脾脏CD3^＋、CD4^＋、CD8^＋淋巴细胞数量。结果未处理旋毛虫组、^60Co处理组和紫外线处理组小鼠肿瘤体积和重量均显著低于对照组（P〈0.05）;脾脏CD3^＋、CD4^＋百分率和CD4^＋/CD8^＋、CD4^＋/CD3^＋的比值显著高于对照组（P〈0.01或P〈0.05）。结论未处理的旋毛虫、经^60Co和紫外线处理的旋毛虫对C57BL/6小鼠体的Hepa1-6肝癌细胞的生长均有抑制作用,未处理旋毛虫的抑瘤效果最好。     

AMPK基因在C57BL／6J小鼠糖脂代谢中的作用

目的研究腺苷酸活化蛋白激酶（AMPK）基因在C57BL／6J小鼠糖脂代谢中的作用。方法分别取5周龄AMPK基因敲除（AMPK-KO）小鼠和C57BL／6J对照小鼠各24只,分为正常饲料（ND）喂养和高脂高糖饲料（HFD）喂养两组。喂养12周,每两周测定小鼠禁食4h血糖（FBG）,实验结束前行口服糖耐量实验（OGTT）,解剖取样,检测血生化指标、脂酶活性及相关蛋白的表达。结果AMPK-KO小鼠血糖、TC、LDL-C、HbA1c、6-磷酸葡萄糖脱氢酶（G6PD）活性、糖原合成酶激酶（GSK）活性、肝脏PPAR7蛋白表达量明显高于对照小鼠（P〈0．05）;其胰岛素含量、肝糖原含量、肌糖原含量、肝脂酶（HL）活性、脂蛋白酯酶（LPL）活性、总脂酶活性、葡萄糖激酶（GK）活性、肝组织P-AMPK蛋白、葡萄糖转运蛋白4（GluT-4）蛋白的表达量低于对照组（P〈0．05）。结论AMPK基因通过调节C57BL／6J小鼠糖脂代谢,在T2DM的发病中起重要作用。     

链脲菌素剂量对C57BL/6J小鼠糖尿病诱导效应的影响

目的 观察不同剂量链脲菌素(STZ)对C57BL/6J小鼠糖尿病诱导效应的影响,探讨其量效关系及最佳剂量范围.方法 将C57BL/6J小鼠按数字随机法分为9个STZ剂量组(A～I组,STZ分别为30、60、80、100、120、150、180、210、240 ms/kg体重),每组15只,腹腔注射;1个对照组,10只,腹腔注射等体积缓冲液.观察各组血糖、体重、血胰岛素和45 d生存率的变化,分析其与STZ剂量的关系.同时取A、C、G及对照组小鼠胰腺、肾脏组织做病理学检杏,并行免疫组化观察胰腺胰岛素及肾脏CD<,68>的表达.结果 C～G组较对照组血糖增高、体重及血胰岛素含量较对照组下降非常显著(P<0.05),且STZ剂量与血糖呈正相关(r=0.984,P<0.05),与血胰岛素含量呈负相关(r=-0.994,P<0.05).C～G组成模率达86.7%～100%,显著高于A、B组的0和40%(P<0.05);45 d生存率为46.7%～73.3%,显著高于H、I组的13.3%和0(P<0.05).A组胰腺、肾脏组织未见明显破坏;C组及G组出现典型的胰岛萎缩变形,胰岛素分泌颗粒减少,肾小球系膜外基质沉着及球周臣噬细胞浸润.结论 C57BL/6J小鼠腹腔注射STZ以80～180 mg/kg体重的剂量制模率高、生存率高,且靶器官损伤典型;该剂量与血糖呈正相关,与血胰岛素含量呈负相关.     

Cyclooxygenase-2 promotes early atherosclerotic lesion formation in ApoE-deficient and C57BL/6 mice

Cyclooxygenase (COX) 2 is expressed in atherosclerotic lesions. We have previously reported that selective inhibition of COX-2 reduces early atherosclerosis in LDLR deficient mice. To examine the role of COX-2 in atherosclerosis in other mouse models, we studied the effects of selective COX-2 inhibition (by rofecoxib and NS-398) and nonselective COX inhibition (by indomethacin) on early atherosclerotic lesion formation in apolipoprotein E-deficient (apoE(-/-)) mice. Selective COX-2 and nonselective COX inhibition reduced atherosclerosis in female apoE(-/-) mice by 35-38% and 38-51% in the proximal and en face aortas, respectively. Next we investigated the role of macrophage COX-2 by transplanting COX-2(-/-) fetal liver cells into C57BL/6 mice and challenging the mice with an atherogenic diet. Genetic deletion of COX-2 from hematopoietic cells reduced atherosclerosis by 51%. In addition, LPS activated COX-2(-/-) macrophages had decreased expression of monocyte chemoattractant protein-1 (MCP-1) and tumor necrosis factor-alpha (TNFalpha). The results demonstrate that selective inhibition of COX-2 and elimination of COX-2 from macrophages significantly reduces early atherosclerotic lesion formation in apoE-deficient and C57BL/6 mice. These results are compatible with COX-2 expression by macrophages having a proatherogenic role, and support the potential of anti-inflammatory therapeutic approaches for atherosclerosis.     

Characteristics of cardiac aging in C57BL/6 mice

The specific processes that cause aging of the cardiac tissue remain elusive. C57BL/6 (B6) mice are commonly used for investigating age-related diseases in mammals. We thus sought to evaluate the cardiac aging process in B6 mice. Cardiac tissues from the newborn (B6 NB), 2 month-old (B6 2M) and 21–27 month-old B6 mice (B6 aged) were used for the investigation. Several age-related cellular processes were evaluated, including telomere shortening, changes in p53 and p16 expression, changes in mitochondria DNA expression and DNA deletion, and alteration of mitochondria. We found that the aging of the B6 mice cardiac tissue is associated with the maintenance of telomere length, increased expression of p53 and p16, mild changes in mitochondrial DNA expression but widespread DNA deletion, and significant alterations of the mitochondrial ultrastructure within the cardiac tissue. The results of our studies suggest that mitochondrial DNA deletions, which affect the mitochondrial ultrastructure, cytochrome C oxidase activity, and p53 expression, are significantly associated with cardiac aging and may be a source of age-related heart failure.     

UV致弱日本血吸虫尾蚴诱导C57BL/6小鼠免疫保护作用的研究

目的 研究紫外线（UV）致弱日本血吸虫尾蚴诱导C57BL／6小鼠的免疫保护作用。方法分别观察不同UV强度（300、400和500μW／cm。照射的日本血吸虫尾蚴经腹部皮肤免疫）、不同免疫剂量（8、24和300条uV致弱尾蚴经腹部皮肤免疫）、不同免疫位点（300条UV致弱尾蚴经腹部和耳廓皮肤免疫）和不同免疫次数（100条UV致弱尾蚴经腹部皮肤免疫3次）诱导C57BL／6小鼠抗血吸虫攻击感染（40条正常尾蚴经腹部皮肤感染）的保护力。同时观察免疫后小鼠的体液免疫应答变化。结果 300、400和500μW／cm。UV照射的日本血吸虫尾蚴免疫C57BI。／6小鼠诱导产生的减虫率分别为2．72％、11．37％和10．38％；8、24和300条致弱尾蚴免疫小鼠诱导产生的减虫率分别为38．67％、7．54％和16．36oA；300条致弱尾蚴经腹部和耳廓皮肤免疫诱导小鼠产生的减虫率分别为16．36％和16．14％；100条致弱尾蚴免疫3次，诱导小鼠产生减虫率为4．88％。对300条uV照射尾蚴免疫后小鼠的体液免疫应答动态观察显示，与感染对照组相比，免疫组血清中可溶性成虫抗原（SWA）和可溶性虫卵抗原（SEA）特异的IgG于免疫后2周开始升高，正常尾蚴抗原（SCA）特异的IgG于免疫1周后开始升高，SWA和SCA特异的IgG随免疫次数的增加而升高。结论 UV致弱日本血吸虫尾蚴免疫C57BL／6小鼠能诱导其产生高水平的体液免疫应答，但保护力水平较低，提示C57BL／6小鼠为对UV致弱日本血吸虫尾蚴的低应答品系。     

Ciglitazone,a new hypoglycaemic agent. 4. Effect on pancreatic islets of C57BL/6J-ob/ob and C57BL/KsJ-db/db mice

Summary Pancreases of treated and control male C57BL/6J-ob/ob and C57BL/KsJ-db/db mice were evaluated by qualitative and morphometric microscopic techniques to determine the effects of chronic ciglitazone treatment on the morphology of cells and surface area and number of pancreatic islets. The cells of treated ob/ob and db/db mice displayed moderate to heavy granulation whereas most cells of untreated obese and diabetic mice were extensively degranulated. Although moderate proliferation of the rough endoplasmic reticulum and Golgi apparatus was evident in some cells of treated db/db mice, both groups of treated ob/ob and db/db mice displayed an improved pattern of insulin synthesis and storage. In contrast, the cells of untreated ob/ob and db/db mice were in a severe state of stress which was indicated by extensive hypertrophy of the rough endoplasmic reticulum, Golgi apparatus and mitochondria. Some cells of untreated db/ db mice also displayed lysosome aggregates indicative of early stages of necrosis. Morphometric analysis revealed that the surface area of islets of treated ob/ob mice was significantly smaller in comparison with that of untreated ob/ob mice. Since the surface area of islets of treated C57BL/6J-+/? mice (lean littermates of ob/ob mice) was less than that of treated ob/ob mice, the progression of islet hypertrophy in the obese mice was probably arrested or attenuated but not to the level of the treated +/? mice. The number of pancreatic islets was significantly greater in treated than in untreated db/ db mice. A majority of the islets of untreated db/db mice were atrophie and consisted of acinar and endocrine cells whereas most of the islets of treated db/db mice appeared to be intact and unremarkable. The results of this study suggest that ciglitazone is an effective hypoglycaemic agent which may directly or indirectly promote -cell regranulation and an improved pattern of insulin synthesis and storage in ob/ob and db/db mice. However, in treated db/db mice, there still was some evidence of stress in the cells. Overall, the prolonged treatment with ciglitazone also seemed to inhibit the hypertrophy of islets in ob/ob mice and protect the structural integrity and viability of islets in db/db mice.     

HIV-1 Env-Specific Memory and Germinal Center B Cells in C57BL/6 Mice

Continued efforts to define the immunogenic properties of the HIV-1 envelope glycoproteins (Env) are needed to elicit effective antibody (Ab) responses by vaccination. HIV-1 is a highly neutralization-resistant virus due to conformational and glycan shielding of conserved Ab determinants on the virus spike. Elicitation of broadly neutralizing Abs that bind poorly accessible epitope regions on Env is therefore extremely challenging and will likely require selective targeting of specific sub-determinants. To evaluate such approaches there is a pressing need for in vivo studies in both large and small animals, including mice. Currently, most mouse immunization studies are performed in the BALB/c strain; however, the C57BL/6 strain offers improved possibilities for mechanistic studies due to the availability of numerous knock-out strains on this genetic background. Here, we compared Env immunogenicity in BALB/c and C57BL/6 mice and found that the magnitude of the antigen-specific response was somewhat lower in C57BL/6 than in BALB/c mice by ELISA but not significantly different by B cell ELISpot measurements. We then established protocols for the isolation of single Env-specific memory B cells and germinal center (GC) B cells from immunized C57BL/6 mice to facilitate future studies of the elicited response at the monoclonal Ab level. We propose that these protocols can be used to gain an improved understanding of the early recruitment of Env-specific B cells to the GC as well as the archiving of such responses in the memory B cell pool following immunization.     

Genetic control of endogenous C-type virus production in pancreatic acinar cells of C57BL/He and C57BL/6J mice.

Electron microscopy revealed very active production of C-type virus particles in the pancreatic acinar cells of untreated normal adult mice of the C57BL/He strain. In C57BL/6J mice, a similar picture was observed after a single intraperitoneal injection of dexamethasone. No viruses were observed in the pancreas of untreated or dexamethasone-treated BALB/c and C3Hf mice. F1 hybrids of both C57BL strains with C3Hf mice produced viruses in the same manner and quantity as the C57BL parents, whereas hybrids with BALB/c mice were entirely negative. Approximately 50% of mice of the first backcross generation of (BALB/c times C57BL/He)F1 hybrids with C57BL/He mice were active producers of C-type particles, while the other 50% were negative. It is suggested that a regulator gene that controls C-type virus production does not function in the pancreatic cells of either C57BL strain, and that BALB/c mice can provide hybrids with an active regulator.     

性别因素对CC57BL/6小鼠日本血吸虫感染所致肝脏病理及抗体免疫的影响

目的探讨性别因素对日本血吸虫感染所致C57BL/6小鼠肝脏病理及抗体免疫的影响。方法雌、雄C57BL/6小鼠分别感染日本血吸虫8周,应用HE染色、天狼星红染色观察小鼠肝脏病理变化。采用酶联免疫吸附试验(ELISA)检测雌、雄C57BL/6小鼠血清抗可溶性成虫抗原(SWA)和可溶性虫卵抗原(SEA)特异性Ig G抗体水平,采用流式细胞术检测雌、雄C57BL/6小鼠脾脏、淋巴结中滤泡辅助性T(Tfh)细胞和调节性T(Treg)细胞水平。结果感染日本血吸虫8周后,雌[(28.050±3.576)×10^4μm^2]、雄小鼠肝组织中平均单个虫卵肉芽肿面积[(26.740±4.093)×10^4μm^2]差异无统计学意义(t=0.241,P=0.821);天狼星红染色结果显示,感染日本血吸虫雌、雄小鼠肝纤维化程度差异亦无统计学意义[天狼星红染色阳性区域平均比例:(7.667±1.856)%vs.(7.667±1.764)%;t=0,P=1;平均光密度:(0.023±0.003)vs.(0.027±0.007);t=0.447,P=0.678]。ELISA检测结果显示,雌、雄小鼠感染日本血吸虫8周后血清抗SWA[(2.098±0.037)vs.(1.970±0.071);t=1.595,P=0.162]和SEA特异性Ig G抗体水平[(3.738±0.039)vs.(3.708±0.043);t=0.512,P=0.623]差异均无统计学意义。流式细胞术检测结果表明,感染日本血吸虫8周后雌、雄小鼠脾脏[雌鼠:(8.645±1.356)%vs.(1.730±0.181)%,t=5.055,P=0.002;雄鼠:(8.470±1.161)%vs.(1.583±0.218)%,t=5.829,P=0.001]、淋巴结[雌鼠:(3.218±0.153)%vs.(1.095±0.116)%,t=11.040,P <0.001;雄鼠:(3.673±0.347)%vs.(0.935±0.075)%,t=8.994,P <0.001]中Tfh细胞比例均显著高于未感染小鼠,但雌、雄小鼠脾脏[(8.645±1.356)%vs.(8.470±1.161)%;t=0.098,P=0.925]和淋巴结[(3.218±0.153)%vs.(3.673±0.347)%;t=1.332,P=0.241]中Tfh细胞比例差异均无统计学意义。感染日本血吸虫8周雄鼠脾脏中Treg细胞比例与未感染小鼠无显著差异[(10.060±0.361)%vs.(10.130±0.142)%;t=0.174,P=0.867],而日本血吸虫感染雌鼠脾脏中Treg细胞比例显著高于未感染小鼠[(10.530±0.242)%vs.(9.450±0.263)%;t=3.021,P=0.023],但感染日本血吸虫雌、雄小鼠脾脏中Treg细胞比例差异无统计学意义[(10.530±0.242)%vs.(10.060±0.361)%;t=1.077,P=0.323];日本血吸虫感染8周后,雌[(17.150±0.805)%vs.(13.100±0.265)%;t=4.781,P=0.003]、雄鼠淋巴结中Treg细胞比例均较未感染小鼠显著增加[(18.550±0.732)%vs.(12.630±0.566)%;t=6.402,P <0.001],但感染日本血吸虫雌、雄小鼠淋巴结中Treg细胞比例差异无统计学意义[(17.150±0.805)%vs.(18.550±0.732)%;t=1.287,P=0.246]。结论利用C57BL/6小鼠研究日本血吸虫感染所致肝脏病理及抗体产生机制时,不需要考虑性别因素。     

The effects of tetrahydrocurcumin and green tea polyphenol on the survival of male C57BL/6 mice

The effect of feeding of two different antioxidants, tetrahydrocurcumin (TC) and green tea polyphenols (PPs) on the survival of male C57BL/6 mice was examined. Mice that started to receive diets containing TC (0.2%) at the age of 13 months had significantly longer average life spans (days, mean ± SD) than control mice (797.6 ± 151.2 vs.882 ± 154.6, both n = 50, controls vs. TC treated, plus 11.7%, P < 0.01). The 10% longest survival was also significantly greater in TC-treated mice (plus 6.5%, P < 0.01). In contrast, in mice that started to receive TC in their 19th month of life, no significant difference from the control mice was found for either the average life span or the 10% longest survival. In mice that received water containing PPs (80 mg/l), the average life span was also significantly longer than in the control mice (801 ± 121.5 vs. 852.7 ± 88.2, plus 6.4%, P < 0.05), although the 10% longest survival was not significantly different from that in the control mice (P > 0.05). The body weights of the TC (but not PP) fed mice, were slightly (2–4%) but significantly (P < 0.05) lower than the values for the corresponding ages in the control mice in the first six months of treatment. Thereafter, the difference in average body weight between the control and the TC-fed animals was totally lost. Although an additional contribution of an unintended slight decrease in food intake due to TC feeding (suspected due to the difference in body weight) is not excluded, we suggest that the feeding of nutritional antioxidants such as TC and PPs may have the potential to beneficially modify the life spans of animals.     

Signalling pathways leading to IFN‐α production in human plasmacytoid dendritic cell and the possible use of agonists or antagonists of TLR7 and TLR9 in clinical indications

Plasmacytoid dendritic cells (PDC) are highly specialized immune cells capable of producing large amounts of type I and III IFN in response to viral infection. This response is mediated through TLR7 and TLR9 signalling pathways. In addition, PDC can differentiate into fully mature dendritic cells able to efficiently crosspresent viral antigens, thus playing an important role in adaptive immunity. This dual property of PDC is being used in clinical settings where synthetic TLR7 and TLR9 ligands are currently evaluated in clinical trials for the treatment of viral infections, allergies and cancers. Interestingly, there is evidence suggesting that chronic activation of PDC by endogenous RNA and DNA containing immune complexes maybe an important mechanism of driving autoimmunity and significant efforts to develop bi‐functional antagonists of TLR7 and TLR9 are currently underway.     

Naltrexone effects on ethanol reward and discrimination in C57BL/6 mice

The effects of the opioid antagonist, naltrexone, on operant responding for oral ethanol reward delivered on a fixed-ratio schedule, and on the discriminative stimulus properties of intraperitoneally injected ethanol, was examined in two separate experiments. The ages, food/water motivational conditions, and naltrexone doses for the two experiments were similar to allow a direct comparison of naltrexone effects on the two measures. Male food-deprived C57BL/6 mice responded for ethanol during either preprandial (low thirst, high hunger motivation) or postprandial (high thirst, low hunger motivation tests). The reinforcing value of ethanol relative to water was greater during the preprandial tests; however, the amounts of ethanol consumed was greater during the postprandial tests, with some mice becoming unconscious during the 15-min test session. Naltrexone produced dose-responsive reductions in responding for ethanol under either testing condition. During postprandial tests, naltrexone reduced responding for ethanol reward at a dose (1.25 mg/kg) that had little effect on responding for water reward, suggesting some selectivity for ethanol reward. In addition, doses of naltrexone that reduced responding for ethanol rewards did not alter the discrimination of ethanol (g/kg) in an operant discrimination task, but did reduce the total number of responses made during these tests. Thus, under similar motivational and dosing conditions, the opiate antagonist attenuated the reinforcing, but not the discriminative properties of ethanol, suggesting that the latter is mediated by either different or additional neural mechanisms in C57BL/6 mice.     

Evidence of immune system melatonin production by two pineal melatonin deficient mice, C57BL/6 and Swiss strains

Abstract:  We evaluated two pineal melatonin deficient mice described in the literature, i.e., C57BL/6 and Swiss mice, as animal models for studying the immunomodulatory action of melatonin. Plasma melatonin levels in C57BL/6 and Swiss strains were detectable, but lower than levels in control C3H/HENHSD mice. Since these strains are suppose to be pineal melatonin deficient an extrapineal melatonin synthesis may contribute to plasma levels. Regarding cells and tissues from the immune system, all of them were found to synthesize melatonin although at low levels. N-acetyltransferase (AANAT) mRNA was also amplified in order to analyze the alternative splicing between exons 3–4 described for pineal C57BL/6 mice which generates an inclusion of a pseudoexon of 102 bp. For the pineal gland, both the wild type and the mutant isoforms were present in all mice strains although in different proportions. We observed a predominant wild type AANAT mature RNA in thymus, spleen and bone marrow cells. Peripheral blood mononuclear cells (PBMC) culture shown an evident AANAT amplification in all strains studied. Although the bands detected were less intense in melatonin deficient mice, the amplification almost reached the control cell intensity after stimulation with phytohemaglutinin (PHA). In summary, melatonin detection and AANAT mRNA expression in inbred and outbred mice clearly indicate that different cells and tissues from the immune system are able to synthesize melatonin. Thus, the pineal defect seems not to be generalized to all tissues, suggesting that other cells may compensate the low pineal melatonin production contributing to the measurable plasma melatonin level.     

Effects of exogenous melatonin and circadian synchronization on tumor progression in melanoma-bearing C57BL6 mice

Circadian rhythmicity impairment reportedly becomes significant as a tumor progresses, while the incidence of cancer can be affected by disruption of the circadian system. Melatonin has oncostatic effects on several types of cancer (breast, prostate, and colorectal cancers), while it can be self-defeating in others, such as lymphoma. Melanoma is one of the most aggressive cancers in humans; however, it seems to respond positively to melatonin in vitro. The present work tested whether body temperature (BT) rhythms are impaired by tumor progression, and whether exogenous melatonin restricts tumor growth and restores circadian rhythmicity; therefore, enhancing survival. To this end, C57 mice were intraperitoneal implanted with a temperature data logger and subcutaneously inoculated with melanoma cells. Animals were then submitted to light-dark (LD) 12:12 cycles or continuous light (LL), with or without melatonin administration. Under LD light conditions, the BT rhythm exhibited a marked reduction in the first circadian harmonic amplitude, and increased phase instability (Rayleigh vector) as the tumor progressed. Melatonin administration (2 mg/kg BW/day), on the other hand, increased the BT rhythm amplitude and phase stability, reduced tumor weight and prevented intraperitoneal dissemination. Exposure to LL induced a free-running rhythm (1500 min), significantly increasing tumor malignity, and therefore reducing survival. Surprisingly, the highest tumor weights and morbidity by metastasis were seen in the LL group treated with melatonin probably because this indoleamine was being administered at different subjective hours to free-running animals. Circadian rhythmicity can thus be used as a marker rhythm for tumor progression, as rhythm impairment increases along with tumor malignancy. While melatonin administration improves rhythmicity and enhances survival under LD conditions, the results are self-defeating when they coexist with circadian disruption as it occurs under LL. This emphasizes the importance of taking into account endogenous rhythmicity and limiting melatonin administration to the subjective night in order to restrict melanoma progression.     

Antigenic determinants on lymphocytes from young and old C57BL/6 mice

Antigenic differences between lymphocytes from young and old female C57BL/6 mice were studied using 3 techniques. In one-way mixed lymphocyte reactions significant responses were obtained in 7.7% of the young leads to young combinations, 13.5% of the young leads to old, 18.2% of the old leads to young and 23.7% of the old leads to old. Polyethylene glycol enhanced the weak syngeneic MLR responses in all groups. Young anti-old antiserum was raised in young animals by injecting with lymphoid cells from old mice. The serum was cytotoxic to spleen cells from 5 of 6 old mice aged in animal facilities at University of Alabama in Birmingham and from 2 of 12 mice aged at Charles River. Lymphocytes from young mice were sensitized to old lymphocytes in a mixed lymphocyte culture and their cytotoxicity toward old cells measured in a chromium-release assay. No cytotoxicity was observed with sensitized lymphocytes from 5 young mice under various conditions. These results do not support the hypothesis that altered anti-genic determinants are always or even usually present on the lymphocytes of old mice.