Hyperthermia

热疗
  • 文章类型: Journal Article
    以前的研究报告说,一个温和的,非蛋白质变性,发热样温度升高可诱导哺乳动物细胞的未折叠蛋白反应(UPR)。我们的dSTORM超分辨率显微镜实验表明,UPR的主调节器,IRE1(需要肌醇的酶1)蛋白,在轻度热应激下,由于人骨肉瘤细胞系(U2OS)中的UPR激活而成簇。使用ER热黄色,针对内质网(ER)的温度敏感荧光探针,我们在小鼠胚胎成纤维细胞(MEF)细胞中检测到显着的细胞内产热。温度至少比外部环境(40°C)高8°C,导致与先前描述的线粒体相似的异常高的ER温度。MEF细胞ER中轻度热诱导的产热可能是由于Ca2/ATPase(SERCA)泵的解偶联。高ER温度在MEF细胞中引发了明显的胞浆热休克反应,在不存在ER产热和SERCA泵解偶联的U2OS细胞中,这一比例显着降低。我们的结果表明,根据固有的细胞特性,轻度高热诱导的细胞内产热定义了细胞反应机制并决定了高热应激的结果。
    Previous studies reported that a mild, non-protein-denaturing, fever-like temperature increase induced the unfolded protein response (UPR) in mammalian cells. Our dSTORM super-resolution microscopy experiments revealed that the master regulator of the UPR, the IRE1 (inositol-requiring enzyme 1) protein, is clustered as a result of UPR activation in a human osteosarcoma cell line (U2OS) upon mild heat stress. Using ER thermo yellow, a temperature-sensitive fluorescent probe targeted to the endoplasmic reticulum (ER), we detected significant intracellular thermogenesis in mouse embryonic fibroblast (MEF) cells. Temperatures reached at least 8 °C higher than the external environment (40 °C), resulting in exceptionally high ER temperatures similar to those previously described for mitochondria. Mild heat-induced thermogenesis in the ER of MEF cells was likely due to the uncoupling of the Ca2+/ATPase (SERCA) pump. The high ER temperatures initiated a pronounced cytosolic heat-shock response in MEF cells, which was significantly lower in U2OS cells in which both the ER thermogenesis and SERCA pump uncoupling were absent. Our results suggest that depending on intrinsic cellular properties, mild hyperthermia-induced intracellular thermogenesis defines the cellular response mechanism and determines the outcome of hyperthermic stress.
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  • 文章类型: Case Reports
    Brugada综合征(BrS)的特征是右心前导联ST段抬高,V1-V3,并在年轻时发现室性心律失常和心源性猝死(SCD)的家族史(FH)。这里,我们描述了一个高热的案例,通过适当的热疗管理,揭示Brugada心电图(EKG)模式和EKG结果的分辨率。重要的是将BrugadaEKG模式与ST段抬高的其他原因区分开来,并进行适当的治疗以防止患者发生心室纤颤和SCD。识别具有BrugadaEKG模式的患者的环境触发因素并密切监测心室纤颤是关键。在发热事件期间,对患者进行及时的退烧药治疗以及避免使用钠通道阻滞剂等药物,对于对抗发生室颤的患者至关重要。这对这些患者的密切随访也至关重要,为他们提供BrS的基因检测和BrS患者的家庭筛查。
    Brugada syndrome (BrS) is characterized by ST segment elevations in the right precordial leads, V1 - V3, with additional findings of ventricular arrhythmias and family history (FH) of sudden cardiac death (SCD) at a young age. Here, we describe a case of hyperthermia, unveiling the Brugada electrocardiography (EKG) pattern and the resolution of EKG findings with appropriate hyperthermia management. It is important to distinguish the Brugada EKG pattern from other causes of ST elevations and treat appropriately to prevent patients from developing ventricular fibrillation and SCD. It is key to identify environmental triggers in patients presenting with Brugada EKG pattern and closely monitor for ventricular fibrillation. Educating patients on prompt fever treatment with antipyretics and avoiding medications like sodium channel blockers during the febrile event is paramount to counter patients going into ventricular fibrillation. It is also crucial for close follow-up of these patients, offering them genetic testing for BrS and screening families of patients with BrS.
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  • 文章类型: Journal Article
    背景:增加膀胱内化疗剂渗透度的装置正在成为经典卡介苗(BCG)治疗的替代品。
    目的:比较丝裂霉素C与电动给药装置(MMC-EMDA)和卡介苗在无原位癌(CIS)的中高危非肌层浸润性膀胱癌(NMIBC)患者中的疗效。
    方法:前瞻性非随机研究,其中47例患者接受MMC-EMDA(40mgMMC在50mg蒸馏水中稀释,20mA,30分钟。每周6次,然后每月6次滴注),48例患者接受BCG(50mgOncoCITE®在50ml生理盐水中稀释60分钟。每周滴注6次,然后在第3、6和12个月滴注3次)。主要终点是24个月时的无复发率(RFR)。次要终点是24个月随访时的复发时间和无进展率(PFR)。
    结果:两组患者的基线评估和平均随访时间相似(MMC-EMDA组:26.4个月;BCG组:28.4个月(p=0.44))。24个月时,MMC-EMDA组的RFR为80.9%,BCG组为77.1%(p=0.969)。MMC-EMDA组的平均复发时间为12.5个月,BCG组为14个月(p=0.681)。24个月时,MMC-EMDA组的PFR为97.9%,卡介苗组为93.8%(p=0.419)。
    结论:在没有CIS的高危和中危NMIBC患者中,MMC-EMDA和BCG治疗没有差异。
    BACKGROUND: Devices that increase the penetrance of intravesical chemotherapeutics are emerging as alternatives to classical Bacillus Calmette Guérin (BCG) treatment.
    OBJECTIVE: To compare the efficacy of mitomycin C applied with the electromotive drug delivery device (MMC-EMDA) versus BCG in patients with intermediate and high-risk non-muscle-invasive bladder cancer (NMIBC) without carcinoma in situ (CIS).
    METHODS: Prospective non-randomized study in which 47 patients received MMC-EMDA (40 mg of MMC diluted in 50 mg of distilled water at 20 mA for 30 min. Regimen of 6 weekly and then 6 monthly instillations) and 48 patients received BCG (50 mg of OncoCITE® diluted in 50 ml of normal saline for 60 min. Regimen of 6 weekly instillations and then 3 weekly instillations at months 3, 6 and 12). The primary endpoint was the recurrence-free rate (RFR) at 24 months. Secondary endpoints were time to recurrence and progression-free rate (PFR) at 24 months follow-up.
    RESULTS: Baseline patient assessment and mean follow-up time were similar in both groups (MMC-EMDA group: 26.4 months; BCG group: 28.4 months (p = 0.44)). The RFR at 24 months was 80.9% for the MMC-EMDA group and 77.1% for the BCG group (p = 0.969). The mean time to recurrence was 12.5 months in the MMC-EMDA group and 14 months in the BCG group (p = 0.681). At 24 months, PFR was 97.9% in the MMC-EMDA group and 93.8% in the BCG group (p = 0.419).
    CONCLUSIONS: No differences were found between MMC-EMDA and BCG treatments in patients with high-risk and intermediate-risk NMIBC without CIS.
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  • 文章类型: Journal Article
    基于热应激暴露后的急性小鼠模型,研究被动热疗如何影响静息状态的功能性脑活动。
    收集体重约24~29g、年龄12~16周龄的C57BL/6J雄性小鼠28只rs-fMRI数据。热疗组的小鼠(HT,40°C±0.5°C,40分钟)在麻醉准备扫描之前进行被动热疗。正常对照组(NC)处于常温状态(NC,20°C±2°C,40分钟)。数据预处理后,我们对HT(n=13)和NC(n=15)的数据进行了独立成分分析(ICA)和感兴趣区域(ROI)-ROI功能连接(FC)分析.
    组ICA分析表明,HT和NC均包含11个固有连接网络(ICN),可以分为四种类型的网络:皮层网络(CN),皮层下网络(SN),默认模式网络(DMN),和小脑网络。CN和SN属于感觉运动网络。与NC相比,HT中ICNs的功能网络组织发生改变,总体功能强度降低.此外,在CN中选择了13个ROI,SN,和DMN用于进一步的ROI-ROIFC分析。ROI-ROIFC分析显示被动热疗显著降低了以CN为代表的全脑的FC强度,SN,小鼠的DMN。
    长时间暴露于高温对小鼠的整体感知和认知水平的影响更大,这可能有助于理解神经元活动与生理热感觉和调节以及行为变化之间的关系。
    UNASSIGNED: To investigate how passive hyperthermia affect the resting-state functional brain activity based on an acute mouse model after heat stress exposure.
    UNASSIGNED: Twenty-eight rs-fMRI data of C57BL/6J male mice which weighing about 24 ∼ 29 g and aged 12 ∼ 16 weeks were collected. The mice in the hyperthermia group (HT, 40 °C ± 0.5 °C, 40 min) were subjected to passive hyperthermia before the anesthesia preparation for scanning. While the normal control group (NC) was subjected to normothermia condition (NC, 20 °C ± 2 °C, 40 min). After data preprocessing, we performed independent component analysis (ICA) and region of interested (ROI)-ROI functional connectivity (FC) analyses on the data of both HT (n = 13) and NC (n = 15).
    UNASSIGNED: The group ICA analysis showed that the HT and the NC both included 11 intrinsic connectivity networks (ICNs), and can be divided into four types of networks: the cortical network (CN), the subcortical network (SN), the default mode network (DMN), and cerebellar networks. CN and SN belongs to sensorimotor network. Compared with NC, the functional network organization of ICNs in the HT was altered and the overall functional intensity was decreased. Furthermore, 13 ROIs were selected in CN, SN, and DMN for further ROI-ROI FC analysis. The ROI-ROI FC analysis showed that passive hyperthermia exposure significantly reduced the FC strength in the overall brain represented by CN, SN, DMN of mice.
    UNASSIGNED: Prolonged exposure to high temperature has a greater impact on the overall perception and cognitive level of mice, which might help understand the relationship between neuronal activities and physiological thermal sensation and regulation as well as behavioral changes.
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  • 文章类型: Journal Article
    磁共振测温法(MRT)可以实时且无创地测量体内3D温度变化。然而,对于口咽区域和整个头部和颈部,运动可能会引入大的伪影。考虑到60-90分钟的长处理时间,本研究旨在评估口咽周围的MRT在热疗治疗中是否具有临床可行性,并量化呼吸和吞咽对MRT表现的影响.3D-ME-FGRE序列用于在约75分钟内冷却五名志愿者的口咽周围的幻影。成像协议包括加速成像(ARC=2),图像平均数(NEX=1、2和3)。对于志愿者来说,这些采集包括屏气扫描和故意吞咽扫描。对颈部肌肉的MRT性能进行了量化,脊髓和咬肌,使用平均平均误差(MAE),平均误差(ME)和空间标准偏差(SD)。在幻影中,NEX的增加导致SD的显着降低,但MAE和我没有改变。在不同扫描之间的志愿者中没有发现显著差异。评估的区域之间存在显着差异:颈部肌肉具有最佳的MAE(=1.96°C)和SD(=0.82°C),其次是脊髓(MAE=3.17°C,SD=0.92°C)和咬肌(MAE=4.53°C,SD=1.16°C)。关于我,脊髓做得最好,然后是颈部肌肉和咬肌,值为-0.64°C,分别为1.15°C和-3.05°C。呼吸,吞咽,和不同的成像方式(加速度和NEX)不会显着影响口咽区域的MRT性能。然而,选择的ROI,导致显著差异。
    Magnetic resonance thermometry (MRT) can measure in-vivo 3D-temperature changes in real-time and noninvasively. However, for the oropharynx region and the entire head and neck, motion potentially introduces large artifacts. Considering long treatment times of 60-90 min, this study aims to evaluate whether MRT around the oropharynx is clinically feasible for hyperthermia treatments and quantify the effects of breathing and swallowing on MRT performance. A 3D-ME-FGRE sequence was used in a phantom cooling down and around the oropharynx of five volunteers over ∼75 min. The imaging protocol consisted of imaging with acceleration (ARC = 2), number of image averages (NEX = 1,2 and 3). For volunteers, the acquisitions included a breath-hold scan and scans with deliberate swallowing. MRT performance was quantified in neck muscle, spinal cord and masseter muscle, using mean average error (MAE), mean error (ME) and spatial standard deviation (SD). In phantom, an increase in NEX leads to a significant decrease in SD, but MAE and ME were unchanged. No significant difference was found in volunteers between the different scans. There was a significant difference between the regions evaluated: neck muscle had the best MAE (=1.96 °C) and SD (=0.82 °C), followed by spinal cord (MAE = 3.17 °C, SD = 0.92 °C) and masseter muscle (MAE = 4.53 °C, SD = 1.16 °C). Concerning the ME, spinal cord did best, then neck muscle and masseter muscle, with values of -0.64 °C, 1.15 °C and -3.05 °C respectively. Breathing, swallowing, and different ways of imaging (acceleration and NEX) do not significantly influence the MRT performance in the oropharynx region. The ROI selected however, leads to significant differences.
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  • 文章类型: Journal Article
    已经开发了癌症药物多柔比星的脂质体制剂以解决在常规制剂中施用该药物导致的严重副作用。其中,热敏脂质体多柔比星与局部肿瘤部位的轻度热疗结合时,可增强肿瘤靶向性和有效的药物释放。利用局部热疗的放射增敏益处,放射治疗与热激活脂质体系统的整合被认为可以增强抗肿瘤功效。本研究探索了一种联合热敏脂质体阿霉素的协同治疗策略,轻度高热,和放射治疗,使用原位小鼠乳腺癌模型。序贯多模式治疗方案,结合低剂量化疗和放疗,与以升高的剂量应用单药治疗相比,实质上推迟了原发性肿瘤生长的进展。还观察到未加热的远处病变的改善。此外,联合治疗的毒性与热敏脂质体治疗或低剂量单独放疗的毒性相当.这些结果强调了多模式治疗策略在改善治疗效果同时减少乳腺癌治疗中的不良反应的潜力。为热敏脂质体阿霉素应用的未来改进提供有价值的见解。
    Liposome formulations of the cancer drug doxorubicin have been developed to address the severe side effects that result from administration of this drug in a conventional formulation. Among them, thermosensitive liposomal doxorubicin presents enhanced tumor targeting and efficient drug release when combined with mild hyperthermia localized to the tumor site. Exploiting the radiosensitizing benefits of localized thermal therapy, the integration of radiation therapy with the thermally activated liposomal system is posited to amplify the anti-tumor efficacy. This study explored a synergistic therapeutic strategy that combines thermosensitive liposomal doxorubicin, mild hyperthermia, and radiotherapy, using an orthotopic murine model of breast cancer. The protocol of sequential multi-modal treatment, incorporating low-dose chemotherapy and radiotherapy, substantially postponed the progression of primary tumor growth in comparison to the application of monotherapy at elevated dosages. Improvements in unheated distant lesions were also observed. Furthermore, the toxicity associated with the combination treatment was comparable to that of either thermosensitive liposome treatment or radiation alone at low doses. These outcomes underscore the potential of multi-modal therapeutic strategies to refine treatment efficacy while concurrently diminishing adverse effects in the management of breast cancer, providing valuable insight for the future refinement of thermosensitive liposomal doxorubicin applications.
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  • 文章类型: Journal Article
    全球癌症发病率持续上升,构成重大公共卫生问题。尽管存在许多癌症疗法,每个都有局限性和并发症。本研究探讨了替代癌症治疗方法,结合热疗和光动力疗法(PDT)。磁性纳米颗粒(MNPs)和胺官能化碳量子点(A-CQDs)分别合成,然后共价缀合以形成用于组合治疗的单个纳米系统(M-CQDs)。使用ζ电位证实了成功的缀合,傅里叶变换红外光谱(FT-IR),和紫外可见光谱。透射电子显微镜(TEM)中的形态学检查进一步证实了CQD与MNP的缀合。能量色散X射线光谱(EDX)揭示M-CQD含有约12重量百分比的碳。热疗研究表明,MNP和M-CQDs在较低频率(260.84kHz)下保持恒定的治疗温度,具有118.11和95.04W/g的高比吸收率(SAR),分别。体外研究表明,MNPs,A-CQDs,M-CQDs是无毒的,与单独治疗相比,联合治疗(PDT+热疗)导致显著更低的细胞活力(~4%)。用Hoechst和碘化丙啶(PI)染色测定获得类似的结果。因此,PDT和热疗的联合疗法有望成为传统疗法的潜在替代品,可以结合现有的常规治疗方法进一步探索。
    The global incidence of cancer continues to rise, posing a significant public health concern. Although numerous cancer therapies exist, each has limitations and complications. The present study explores alternative cancer treatment approaches, combining hyperthermia and photodynamic therapy (PDT). Magnetic nanoparticles (MNPs) and amine-functionalized carbon quantum dots (A-CQDs) were synthesized separately and then covalently conjugated to form a single nanosystem for combinational therapy (M-CQDs). The successful conjugation was confirmed using zeta potential, Fourier transform infrared spectroscopy (FT-IR), and UV-visible spectroscopy. Morphological examination in transmission electron microscopy (TEM) further verified the conjugation of CQDs with MNPs. Energy dispersive X-ray spectroscopy (EDX) revealed that M-CQDs contain approximately 12 weight percentages of carbon. Hyperthermia studies showed that both MNP and M-CQDs maintain a constant therapeutic temperature at lower frequencies (260.84 kHz) with high specific absorption rates (SAR) of 118.11 and 95.04 W/g, respectively. In vitro studies demonstrated that MNPs, A-CQDs, and M-CQDs are non-toxic, and combinational therapy (PDT + hyperthermia) resulted in significantly lower cell viability (~4%) compared to individual therapies. Similar results were obtained with Hoechst and propidium iodide (PI) staining assays. Hence, the combination therapy of PDT and hyperthermia shows promise as a potential alternative to conventional therapies, and it could be further explored in combination with existing conventional treatments.
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  • 文章类型: Journal Article
    目的:腹膜癌病(PC)在治疗晚期,实体瘤,传统疗法受药物渗透性差的限制。我们使用人腹腔模型评估了一种新型的高温加压腹膜内气溶胶化疗(HPIPAC)系统对AGS胃癌细胞的疗效。
    方法:使用模拟人腹腔和AGS胃癌细胞系培养皿的模型来评估HPIPAC系统的功效。测量细胞活力以评估HPIPAC在6种不同条件下的影响:仅加热,PIPAC与紫杉醇(PTX),仅PTX,单独使用生理盐水(NS),用NS加热,以及带有PTX的HPIPAC。
    结果:结果显示HPIPAC与PTX联用时细胞活力显著降低,表明增强的细胞毒性作用。治疗后立即,平均细胞活力为66.6%,48小时后下降到49.2%,120小时后下降到19.6%,证明了治疗的持续疗效。相比之下,对照组显示细胞活力恢复;仅加热显示细胞活力从90.8%增加到94.4%,PIPAC与PTX从82.7%到89.7%,PTX仅从73.3%到74.8%,NS仅从90.9%到98.3%,和加热NS从74.4%到84.7%。
    结论:使用PTX的HPIPAC系统在治疗胃癌PC中显示出一种有希望的方法,显著降低细胞活力。尽管有一定的局限性,这项研究强调了该系统提高治疗效果的潜力。未来的努力应集中在完善HPIPAC并验证其在临床环境中的有效性。
    OBJECTIVE: Peritoneal carcinomatosis (PC) presents a major challenge in the treatment of late-stage, solid tumors, with traditional therapies limited by poor drug penetration. We evaluated a novel hyperthermic pressurized intraperitoneal aerosol chemotherapy (HPIPAC) system using a human abdominal cavity model for its efficacy against AGS gastric cancer cells.
    METHODS: A model simulating the human abdominal cavity and AGS gastric cancer cell line cultured dishes were used to assess the efficacy of the HPIPAC system. Cell viability was measured to evaluate the impact of HPIPAC under 6 different conditions: heat alone, PIPAC with paclitaxel (PTX), PTX alone, normal saline (NS) alone, heat with NS, and HPIPAC with PTX.
    RESULTS: Results showed a significant reduction in cell viability with HPIPAC combined with PTX, indicating enhanced cytotoxic effects. Immediately after treatment, the average cell viability was 66.6%, which decreased to 49.2% after 48 hours and to a further 19.6% after 120 hours of incubation, demonstrating the sustained efficacy of the treatment. In contrast, control groups exhibited a recovery in cell viability; heat alone showed cell viability increasing from 90.8% to 94.4%, PIPAC with PTX from 82.7% to 89.7%, PTX only from 73.3% to 74.8%, NS only from 90.9% to 98.3%, and heat with NS from 74.4% to 84.7%.
    CONCLUSIONS: The HPIPAC system with PTX exhibits a promising approach in the treatment of PC in gastric cancer, significantly reducing cell viability. Despite certain limitations, this study highlights the system\'s potential to enhance treatment outcomes. Future efforts should focus on refining HPIPAC and validating its effectiveness in clinical settings.
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  • 文章类型: Journal Article
    这项研究旨在评估无法补偿的热应力(0.03°C增加/分钟)后立即评估上身和消防员个人防护设备(PPE)的热区。我们假设通过红外热成像法测得,头部的前部和消防员头盔的内部将是最热的。这一假设是由于以前的研究表明,头部占体表面积的8%-10%,但在适度运动时,它占全身散热量的20%。20名参与者在环境室(35°C,50%湿度)在消防员PPE中。分析的身体区域是头部的额叶区域,胸部,腹部,手臂,脖子,上背部,下背部。被分析的PPE的区域是头盔和夹克的内部。运动后身体最热的区域是头部的额叶区域(平均值:37.3±0.4°C),胸部(平均:37.5±0.3°C),和上背部(平均值:37.3±0.4°C)。上身最冷的区域是腹部(平均值:36.1±0.4°C)。头盔内部的峰值温度增加了9.8°C(p<0.001),从27.7±1.6°C增加到37.4±0.7°C,夹套的内部增加了7.3°C(p<0.001),从29.2±1.7°C增加到36.5±0.4°C。这项研究的结果与消防员的冷却策略有关。
    This research sought to evaluate the thermal zones of the upper body and firefighter personal protective equipment (PPE) immediately following uncompensable heat stress (0.03 °C increase/min). We hypothesized that the frontal portion of the head and the inside of the firefighter helmet would be the hottest as measured by infrared thermography. This hypothesis was due to previous research demonstrating that the head accounts for ∼8-10% of the body surface area, but it accounts for ∼20% of the overall body heat dissipation during moderate exercise. Twenty participants performed a 21-min graded treadmill exercise protocol (Altered Modified Naughton) in an environmental chamber (35 °C, 50 % humidity) in firefighter PPE. The body areas analyzed were the frontal area of the head, chest, abdomen, arm, neck, upper back, and lower back. The areas of the PPE that were analyzed were the inside of the helmet and the jacket. The hottest areas of the body post-exercise were the frontal area of the head (mean: 37.3 ± 0.4 °C), chest (mean: 37.5 ± 0.3 °C), and upper back (mean: 37.3 ± 0.4 °C). The coldest area of the upper body was the abdomen (mean: 36.1 ± 0.4 °C). The peak temperature of the inside of the helmet increased (p < 0.001) by 9.8 °C from 27.7 ± 1.6 °C to 37.4 ± 0.7 °C, and the inside of the jacket increased (p < 0.001) by 7.3 °C from 29.2 ± 1.7 °C to 36.5 ± 0.4 °C. The results of this study are relevant for cooling strategies for firefighters.
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  • 文章类型: Journal Article
    鸟类在吸热动物中保持一些最高的体温。通常被认为是耐热性的选择性优势,高体温也限制了鸟类在达到致命水平之前的热安全范围。最近的模型表明,在温和的气温下,北极鸟类的持续努力可能会受到限制,这可能需要减少活动以避免过热,对生殖性能有预期的负面影响。我们测量了平静鸟类体内体温的变化,然后测量了北极户外圈养种群活动的实验性增加,冷专用雪束(Plectrophenaxnivalis),暴露于自然变化的空气温度(-15至36°C)。平静的束表现出的模态温度范围为39.9至42.6°C。然而,我们发现,在将平静的鸟类转移到主动飞行的几分钟内,体温显着升高,有强有力的证据表明空气温度对体温有积极影响(斜率=0.04°C/°C)。重要的是,环境温度为9°C,飞行束带已经产生≥45°C的体温,接近有机体性能的热上限(45-47°C)。已知这些鸟类的蒸发散热能力有限,我们的结果支持了最近的预测,即以最大可持续的速度运行的自由生活束带将越来越需要依靠行为体温调节策略来调节体温,不利于雏鸟的生长和生存。
    Birds maintain some of the highest body temperatures among endothermic animals. Often deemed a selective advantage for heat tolerance, high body temperatures also limits birds\' thermal safety margin before reaching lethal levels. Recent modelling suggests that sustained effort in Arctic birds might be restricted at mild air temperatures, which may require reductions in activity to avoid overheating, with expected negative impacts on reproductive performance. We measured within-individual changes in body temperature in calm birds and then in response to an experimental increase in activity in an outdoor captive population of Arctic, cold-specialised snow buntings (Plectrophenax nivalis), exposed to naturally varying air temperatures (- 15 to 36 °C). Calm buntings exhibited a modal body temperature range from 39.9 to 42.6 °C. However, we detected a significant increase in body temperature within minutes of shifting calm birds to active flight, with strong evidence for a positive effect of air temperature on body temperature (slope = 0.04 °C/ °C). Importantly, by an ambient temperature of 9 °C, flying buntings were already generating body temperatures ≥ 45 °C, approaching the upper thermal limits of organismal performance (45-47 °C). With known limited evaporative heat dissipation capacities in these birds, our results support the recent prediction that free-living buntings operating at maximal sustainable rates will increasingly need to rely on behavioural thermoregulatory strategies to regulate body temperature, to the detriment of nestling growth and survival.
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