药用植物肿节枫诱导前噬菌体有效组分的分析

在11种溶原性细菌系统中,以双层琼脂平板-纸片法检测药用植物肿节枫对前噬菌体的诱导作用,表明温和性噬菌体φ52 Ⅰ溶原化的金黄色葡萄球菌2009,对肿节枫的诱导反应最为敏感。其它溶原性菌株,包括曾用以筛选抗肿瘤药物的大肠杆菌K_(12)(λ)-K_(12)S系统都呈阴性反应。化学成分的进一步分析说明,仅肿节枫黄酮糖苷组分Ⅰ具有诱导活性。并与丝裂霉素C作了比较。     

Peripheral administration of oxytocin increases social affiliation in the naked mole-rat (Heterocephalus glaber)

The neuropeptide oxytocin regulates a wide variety of social behaviors across diverse species. However, the types of behaviors that are influenced by this hormone are constrained by the species in question and the social organization that a particular species exhibits. Therefore, the present experiments investigated behaviors regulated by oxytocin in a eusocial mammalian species by using the naked mole-rat (Heterocephalus glaber). In Experiment 1, adult non-breeding mole-rats were given intraperitoneal injections of either oxytocin (1 mg/kg or 10 mg/kg) or saline on alternate days. Animals were then returned to their colony and behavior was recorded for minutes 15–30 post-injection. Both doses of oxytocin increased huddling behavior during this time period. In Experiment 2, animals received intraperitoneal injections of either oxytocin (1 mg/kg), an oxytocin-receptor antagonist (0.1 mg/kg), a cocktail of oxytocin and the antagonist, or saline across 4 testing days in a counterbalanced design. Animals were placed in either a 2-chamber arena with a familiar conspecific or in a small chamber with 1 week old pups from their home colony and behaviors were recorded for minutes 15–30 post-injection. Oxytocin increased investigation of, and time spent in close proximity to, a familiar conspecific; these effects were blocked by the oxytocin antagonist. No effects were seen on pup-directed behavior. These data suggest that oxytocin is capable of modulating affiliative-like behavior in this eusocial species.     

Comparative forelimb morphology of scratch-digging and chisel-tooth digging African mole-rat species

Bathyergus suillus (Cape dune mole-rat) and Heterocephalus glaber (naked mole-rat) are two species of subterranean burrowing rodents. Bathyergus suillus occurs in soft sandy soils and is regarded as a scratch-digger, while H. glaber is found in hard, compact soils and is a chisel-tooth digging species. The present study aimed to determine musculoskeletal differences in the forelimb of these two species. The muscles of the forelimb, back and neck were dissected to the points of origin and insertion in the left and right forelimbs, B. suillus (n = 7) and H. glaber (n = 5). Dissected muscles were photographed before maceration to demonstrate muscle attachments. The scapular spine, acromion process and clavicle were relatively straight in B. suillus. In comparison a curved scapular spine, acromion process and clavicle were observed in H. glaber. In both species, the clavicle rested on the greater tuberosity of the humerus. In B. suillus, the deltoid tuberosity was prominent and situated more distally on the humeral shaft compared to the indistinct, more proximally situated deltoid tuberosity in H. glaber. A prominent bony structure underlying the thenar pad as well as a cartilaginous protrusion beneath the hypothenar pad were observed on the palmar surface of the manus in B. suillus. Prominent claws were observed in B. suillus. A robust m. sternohyoideus was observed in H. glaber while mm. tensor fasciae antebrachii and coracobrachialis were absent. The flexors of the antebrachium of B. suillus had additional and enlarged attachment sites. The forelimb of B. suillus may be morphologically adapted for scratch-digging with relatively large and additional forelimb muscles and robust bones. In comparison, H. glaber had a reduction in the relative size, amount of muscles as well as number of attachment sites in the forelimb muscles, while the well-developed ventral neck muscles may facilitate neck and head stabilisation during chisel-tooth digging.     

Dispersal and new colony formation in wild naked mole-rats: evidence against inbreeding as the system of mating

Early field work on naked mole-rats, Heterocephalus glaber, suggestedthat small colonies are rare and that colonies can only formby fissioning of existing colonies. Many researchers expectedthat this would result in extreme inbreeding and high relatednesswithin colonies and would thus explain the evolution of eusocialityin naked mole-rats. Here I report evidence of dispersers andoutbreeding in colonies of wild naked mole-rats that suggeststhat inbreeding is not the system of mating for this speciesand that outbreeding is probably frequent. Wild dispersers havethe same morphology as was reported for dispersers in laboratorycolonies. Low levels of genetic variation in previous moleculargenetic studies of naked mole-rats probably result from theviscous population structure typical of fossorial rodents.     

The microenvironment of naked mole‐rat burrows in East Africa

Naked mole‐rats (Heterocephalus glaber) can be extremely long‐lived and are resistant to cancer. Hence, they have been proposed as a model organism for delayed ageing. Adaptation to a constant hypoxic and hypercapnic environment has been suggested as reason for their apparent ability to tolerate oxidative stress. Nevertheless, little is known about the natural habitat to which the species evolved. Naked mole‐rat burrow environments were assessed in Ethiopia and Kenya. Despite reported thermolability of naked mole‐rats, skin temperature upon capture varied (23.7–35.4°C), mostly within the species’ thermoneutral zone, demonstrating their ability to maintain homoiothermy even under wide fluctuations of burrow temperature (24.6–48.8°C) and humidity (31.2%–92.8%), which are far greater than previously reported. Burrow temperature regularly alternates during the daytime and night‐time, driving convective currents that circulate air in the tunnels. Consequently, concentrations of CO₂ and O₂ in burrows only slightly deviated from surface atmosphere. This contradicts the assumption of constant hypoxia/hypercapnia in subterranean burrows. In addition to diffusion, animal movement and occasional wind‐driven ventilation, our data support the temperature‐driven convective model of circulation. The naked mole‐rat burrow is a relatively normoxic subterranean microenvironment with considerable fluctuations in temperature and humidity.     

长寿型啮齿类动物的抗肿瘤机制

啮齿类动物是广泛应用于生物医学的重要模式动物,包括先天性胸腺缺陷型的裸鼠、不患癌的裸鼹鼠(Heterocephalus glaber)和盲鼹鼠(Spalax galili)等。哺乳动物的衰老过程与癌症发生率有关,衰老的程度与患癌机率呈正相关。由于啮齿类动物约占哺乳动物的40%,因此研究长寿型啮齿类动物抗肿瘤机制对于抗癌机制的研究具有十分重要的作用。复制性衰老是啮齿类动物中普遍存在的抗肿瘤机制,但在裸鼹鼠和盲鼹鼠体内发现了独特的抗肿瘤机制：盲鼹鼠主要的抗肿瘤机制是由细胞释放IFN-β,激活p53和Rb信号通路,进而导致细胞集中性死亡;裸鼹鼠的抗肿瘤机制是由高分子量透明质酸引起的早期接触性抑制介导。此外,裸鼹鼠和盲鼹鼠的基因组中还含有高表达与调节细胞死亡和抗炎机制相关的基因。本文对裸鼹鼠和盲鼹鼠的独特抗肿瘤机制进行了综述,以期为该领域的相关研究提供参考。     

Cumulative effects of fire on a tussock pampa grassland

Abstract. In order to test for cumulative effects of fire on Paspalum quadrifarium‐dominated grasslands (‘pajonal’), we analysed the impact of single and repeated fires on the community structure and post‐fire recovery of canopy after a final, simultaneous fire event. Nine plots were defined within a homogeneous pajonal stand, and treatments of low (LF), medium (MF) and high frequency (HF) of fire were defined by the application of one, two or four cold‐season burns, respectively, along a 6‐yr period. Both burned and unburned plots were exposed to grazing by cattle during the summer following the first and the third years of that period. High cattle preference for burned sites conditioned fire temperature and vegetation responses to the following burning events. Cumulative effects between successive burning events were observed for the cover of basal area of the dominant and other sprouting species, the cover and thickness of the litter layer, the seed bank size of the principal recruiter species, and the floristic composition. While light interception by the canopy was positively related to fire frequency during the early growth season, further growth of P. quadrifarium determined a greater light interception in LF than in MF and HF. These patterns of light interception were associated with a faster occupation of the inter‐tussock areas by opportunistic species in plots subjected to frequent fires (HF and MF) than in plots with low fire frequency (LF), and a more lasting regrowth of P. quadrifarium in the LF plot than in the HF ones. High fire frequencies reduced the dominance of P. quadrifarium. Percent of species classified as subordinated graminoids or forbs did not vary among treatments. However, the abundance of different forb species was differentially favoured by contrasting frequencies of fire, describing some coarse relationships between their specific responses and their dispersal strategies.     

Caecal function provides the energy of fermentation without liberating heat in the poikilothermic mammal,Heterocephalus glaber

Summary This paper presents the first report of a mammalian internal organ with a lower temperature than its abdominal surrounds. Heterocephalus glaber, the naked mole-rat, is a poikilothermic mammal that leads a strictly subterranean existence and consumes a high proportion of fibre in its diet. The fermentation chamber in these animals appears to absorb rather than generate heat and the temperature in it was consistently 1.2±0.5°C (n=17) lower than rectal temperature. A caecum with a lower temperature than its abdominal surrounds provides an internal heat sink which could be advantageous for metabolic heat dissipation in the plugged humid burrows in which the naked mole-rat permanently resides.Abbreviations RH relative humidity - T _b body temperature - T _c caecal temperature - T _i intraperitoneal temperature - T _r rectal temperature     

黄曲霉素对裸鼹鼠肺泡上皮Ⅱ型细胞基因表达的影响

目的:观察不同浓度黄曲霉素对裸鼹鼠肺泡上皮Ⅱ型细胞(AEC II)相关因子m RNA表达的影响,探讨裸鼹鼠抵御肺癌的分子机制。方法:通过酶消化法分离裸鼹鼠肺组织细胞并用免疫黏附法进行纯化得到裸鼹鼠肺泡上皮Ⅱ型细胞进行原代培养,40小时后,实验组分别给予不同浓度(0.25、0.5、1.0、2.0和4.0 mg/L)的黄曲霉素处理,溶剂对照组给予DMSO(0.4 m L/L)处理。黄曲霉素作用48小时后收集细胞,用实时定量PCR技术检测裸鼹鼠AECII细胞中的SP-C基因及TNF-α、IL-1、IL-6、IL-8、IL-12等炎症因子的m RNA表达变化。结果:原代分离的裸鼹鼠AEC II细胞纯度70%,活性90%,可用于体外实验。定量PCR结果显示黄曲霉素使裸鼹鼠AEC II细胞SP-C表达水平显著下降,TNF-α、IL-1、IL-6、IL-8、IL-12等炎症因子的表达水平在黄曲霉低于2 mg/L浓度的条件下没有显著变化。结论:裸鼹鼠AEC II细胞在黄曲霉素导致细胞受损的情况下,仍然保持较低水平的炎症因子表达,这可能是其抵抗肺癌的机制之一。