Rewarming rates of two large hibernators: Comparison of a monotreme and a eutherian

We measured body temperatures in two large hibernating mammals, the eutherian alpine marmot (Marmota marmota) and the egg-laying echidna (Tachyglossus aculeatus) from unrestrained animals in their natural environment. In both species hibernation is broken every 13 days on average by rewarming to euthermic temperatures. We found that the time course of a rewarming could be closely fitted with a sigmoid curve, allowing calculation of peak rewarming rate and corresponding body temperature. Maximum rewarming rates were twice as high in marmots as in echidnas (12.1±1.3 °C h⁻¹, n=10 cf. 6.2±1.2 °C h⁻¹, n=10). Peak rewarming rates were positively correlated with body temperature in echidnas, but negatively correlated in marmots.     

COMPARISON OF GROWTH AND SINKING RATES OF NON-COCCOLITH- AND COCCOLITH-FORMING STRAINS OF EMILIANIA HUXLEYI(PRYMNESIOPHYCEAE) GROWN UNDER DIFFERENT IRRADIANCES AND NITROGEN SOURCES1

We examined the effect of the presence or absence of coccoliths on the growth and sinking rates of an oceanic isolate of the coccolithophore Emiliania huxleyi (Lohmann) Hay et Mohler isolated from the northeastern subarctic Pacific. Coccolith-forming and non-coccolith-forming (i.e. naked, nonmotile) strains were obtained from the same isolate and grown under both saturating and limiting irradiance levels with either nitrate or ammonium as the primary nitrogen source. Sinking rate, growth rate, and cell volume (excluding coccoliths) were measured for each culture. Under saturating irradiance, coccolith-forming cells grew significantly slower than naked cells, had significantly higher sinking rates, and had larger cell volumes than naked cells. Under limiting irradiance levels, growth rates of the two strains were identical, sinking rates were higher for coccolith-forming cells in stationary-phase cultures only, and cell volumes remained greater for coccolith-forming cells. The sinking rates achieved for this ubiquitous coccolithophore ranged from <0.1 to 0.5 m · d^?1. Sinking rates were not statistically different between coccolith-forming and naked strains of E. huxleyi under limiting irradiance conditions for log-phase cultures, but sinking rates were greater for coccolith-forming cells under some of the other conditions tested. However, the average sinking rate was never more than twice as great as for coccolith-forming cells, with the exception of nitrate-grown, senescent cells under limiting irradiance (3.4 times greater). Cell volumes (excluding coccoliths) were consistently ca. 1.5 times greater for coccolith-forming cells than for naked cells. Nitrogen source had an effect on growth rate and cell volume, with ammonium-grown cultures growing faster and having larger cell volumes than nitrate-grown cultures of both strains. However, despite the difference in growth rate and cell volume, nitrogen source had little if any effect on sinking rate.     

Nutritional assessment of somatolactin function in gilthead sea bream (Sparus aurata): concurrent changes in somatotropic axis and pancreatic hormones

The role of somatolactin (SL) in the regulation of energy homeostasis in gilthead sea bream (Sparus aurata) has been analysed. First, a down-regulation of plasma SL levels in response to gross shifts in dietary amino acid profile and the graded replacement of fish meal by plant protein sources (50%, 75% and 100%) has been observed. Thus, the impaired growth performance with changes in dietary amino acid profile and dietary protein source was accompanied by a decrease in plasma SL levels, which also decreased over the course of the post-prandial period irrespective of dietary nitrogen source. Secondly, we examined the effect of SL and growth hormone (GH) administration on voluntary feed intake. A single intraperitoneal injection of recombinant gilthead sea bream SL (0.1 microg/g fish) evoked a short-term inhibition of feed intake, whereas the same dose of GH exerted a marked enhancement of feed intake that still persisted 1 week later. Further, we addressed the effect of arginine (Arg) injection upon SL and related metabolic hormones (GH, insulin-like growth factor-I (IGF-I), insulin and glucagon) in fish fed diets with different nitrogen sources. A consistent effect of Arg injection (6.6 micromol/g fish) on plasma GH and IGF-I levels was not found regardless of dietary treatment. In contrast, the insulinotropic effect of Arg was found irrespective of dietary treatment, although the up-regulation of plasma glucagon and glucose levels was more persistent in fish fed a fish meal based diet (diet FM) than in those fed a plant protein diet with a 75% replacement (diet PP75). In the same way, a persistent and two-fold increase in plasma SL levels was observed in fish fed diet FM, whereas no effect was found in fish fed diet PP75. Taken together, these findings provide additional evidence for a role of SL as a marker of energy status, which may be perceived by fish as a daily and seasonal signal of abundant energy at a precise calendar time.     

Effect of light supply and carbon source on cell growth and cellular composition of a newly isolated microalga Chlorella vulgaris ESP‐31

Light supply is one of the most important factors affecting autotrophic growth of microalgae. This study investigated the effect of the type and light intensity of artificial light sources on the cell growth of an indigenous microalga Chlorella vulgaris ESP‐31 obtained from southern Taiwan. In addition, a dissolved inorganic carbon source (i.e. sodium bicarbonate) was used to improve the biomass production of strain ESP‐31. The results show that a new fluorescent light source (TL5) was effective in indoor cultivation of microalgae. Better overall productivity of 0.029 g dry cell weight/L‐d was obtained when using TL5 lamps as the light source with a light intensity of 9 W/m². A carbon source (sodium bicarbonate) concentration of 1000 mg/L was found to be optimal for the growth of strain ESP‐31 in terms of both biomass production and carbon source utilization. Under the optimal growth conditions, the resulting microalgal biomass consisted of 25–30% protein, 6–10% carbohydrate, and 30–40% lipid.     

腹泻仔猪源致病性大肠杆菌生物膜与耐药性及毒力的相关性

【目的】探讨腹泻仔猪源致病性大肠杆菌生物膜形成能力及其与耐药性、毒力之间的相关性。【方法】收集临床分离鉴定的129株致病性大肠杆菌,采用96孔微量板法、K-B法、微量稀释法、寇氏改良法分别测定体外生物膜形成能力、耐药表型、生物膜菌与浮游菌的最小抑菌浓度(MIC)、对小鼠的半数致死量(LD_(50))。【结果】129株致病性大肠杆菌生物膜阳性率为96.1%,以弱阳性(1+)为主;分离株对四环素、氨苄青霉素、阿莫西林的耐药率分别为92.2%、92.2%、93%,对亚胺培南的耐药率最低为1.6%,共呈现94种多重耐药谱,其中以阿莫西林-氨苄青霉素-四环素-强力霉素-复方新诺明-甲氧苄啶构成比最大,为86.0%,且其与环丙沙星、氟苯尼考、左氧氟沙星、诺氧沙星、头孢拉定及头孢哌酮的耐药性有相关性(P0.05),环丙沙星和氟苯尼考对生物膜形成菌的MIC较对应浮游菌分别提高2-16倍和8-16倍;生物膜形成能力3+的菌株LD_(50)最大。【结论】腹泻仔猪源致病性大肠杆菌普遍具有生物膜形成能力,呈现多重耐药,生物膜形成菌对环丙沙星及氟苯尼考的耐药性与生物膜形成能力呈正相关,但随着生物膜形成能力的增强,LD_(50)值则相应增大。     

长江中游稻区夏季飞机航捕迁入褐飞虱的轨迹分析

根据1977～1979年3年的7月份飞机航捕褐飞虱Nilaparvata lugens的资料, 应用轨迹分析模型,得出了长江中游稻区夏季迁入褐飞虱的中尺度虫源地及迁入路径。1）湘东北-鄂东南稻区虫源来自桂中至湘中稻区（24°～ 28°N,109°～114°E）,褐飞虱的迁入路径有两条：①柳州→桂林→衡阳→该区;②柳州→桂林→邵阳→该区。2）赣北-鄂东稻区虫源来自桂中至赣西稻区（24°～29°N,110°～115°E）,褐飞虱的迁入路径有一条：蒙山→倏县→宜春→该区。3）湘中、东部稻区虫源来自桂南至湘南稻区 （23°～27°N,109°～113°E）,褐飞虱的迁入路径有一条：南宁→柳州→桂林→该区。     

Effect of genotype,explant type and growth regulators on organogenesis in Morus alba

Plantlets of the mulberry (Morus alba L. vars. Chinese White, and Kokuso-27) were produced from callus cultures. For callus induction, leaf, internodal segments, and petiole explants of Chinese White, Kokuso-27 and Ichinose varieties were grown on MS basal medium fortified with 2,4-D and 6-benzylaminopurine (BA). Callogenesis was dependent on the nature of explant used, the genotype and growth regulators supplemented in the medium. Leaves were the best explant type used for callus induction. Best callogenesis was obtained on MS medium containing a combination of 1 mg l⁻¹ 2,4-D and 0.5 mg l⁻¹ BA (95-100%). Calluses formed shoots on MS medium supplemented with 1 mg l⁻¹ BA. Supplementation with 0.1 mg l⁻¹ 2,3,5-triiodobenzoic acid (TIBA) in this medium enhanced shooting response. Presence of TIBA in the medium also improved the long-term organogenic potential of the callus. Regenerated shoots produced roots on Murashige & Skoog (MS) medium containing either 0.5 mg l⁻¹ indole-3-butyric acid (IBA) or α-naphthaleneacetic acid (NAA). Seventy percent of the rooted plants were established in the field where they are performing well. This revised version was published online in June 2006 with corrections to the Cover Date.     

Reproduction in Wild Populations of the Threatened Tree Macadamia tetraphylla: Interpopulation Pollen Enriches Fecundity in a Declining Species

Macadamia tetraphyll a is a subtropical rain forest tree from fragmented lowlands in eastern Australia. Owing to habitat loss and fragmentation, this commercially important species is vulnerable to extinction. Breeding system and fecundity were investigated in nine populations incorporating three habitat types (moderately disturbed, highly disturbed, and intact) to determine if seed set, seed weight, and genetic diversity are compromised by disturbance. Breeding success was also tested using pollen donors from distant (30–100 km), local (2–3 km), neighbor (10–20 m), and near-neighbor (< 10 m) sources. Macadamia tetraphylla is weakly self-compatible but incapable of automatic self-pollination. Across populations, seed to flower ratios were always < 0.1 percent in open-pollinated trees and trees from moderately disturbed habitats had the highest fruit production. Outcross pollen produced more seed per raceme than open-pollinated or self-pollination treatments. Seed set and seed weights were positively influenced by pollen source with local pollen and distant pollen effecting more or heavier seeds. Germination rates and genetic diversity did not vary significantly in seedlings from different pollen sources. Results suggest a pollen source from at least a 2 km distance is an optimal outbreeding distance; however, many wild populations do not have conspecifics at optimal distances owing to habitat fragmentation. Highly disturbed populations are producing seed but the longevity of these sites is threatened by weed invasions. We conclude that small populations in degraded habitats that are at risk of being overlooked should not be ignored but should be a focus for restoration efforts as they are a valuable asset for the conservation of M. tetraphylla .     

荒漠化与气候变化间反馈机制研究进展

荒漠化和气候变化是全球关注的重大环境问题,两者间的反馈机制是目前科学研究的热点之一。从荒漠化与气候变化间的反馈机制和荒漠化及其防治对碳源／汇的影响两方面对其研究进展进行了评述。以往的研究表明,荒漠化对区域乃至全球气候变化的影响主要通过荒漠化过程中植被覆盖降低一地表反射率提高和(或)土壤含水量降低-降雨量降低-植被覆盖降低这样一个正反馈机制(荒漠化生物地球物理模型“Charney假说”及其衍生理论)来实现的,此外大气中悬浮的沙尘具有明显抑制降雨的作用,土地荒漠化所导致的沙尘暴频发及其影响范围之大也将对全球气候变化产生显著影响。气候变化对荒漠化的影响则表现在对荒漠化的范围、发展速度和强度以及潜在危险性及干旱生态系统的结构、功能及生产力的影响上。同时作为全球重要的碳贮存地,干旱区的变化从一定程度上影响到大气中CO2的收支．据估算全球荒漠化所导致的碳损失总量为18～28Pg C,其中中国近40a来因土地沙质荒漠化导致的CO2净释放量为91Mt C,如果UNEP建议的退化土地治理措施得以实施,每年可固定37Pg的碳,约占CO2年排放量的15％．其投入低于一些限制CO2排放的措施,因此具有很大的吸引力。从目前的研究进展来看,大多数研究尚处于定性描述阶段,虽然有一些量化的尝试,但多停留在低精度的外推或估算上,因此今后有关荒漠化与气候变化间反馈机制研究的重点应放在：(1)量化气候变化过程对干旱生态系统弹性、生物多样性、生物生产力和总体健康的影响。(2)模拟荒漠化发生发展对区域和全球的气候变化影响,(3)评价荒漠化防治对气候变化的可能影响及其程度,特别是一些大范围的生态建设工程在防治土地荒漠化方面的作用及其对气候变化的可能影响。简言之,从科学和政策的角度来看弄清荒漠化与气候变化间的反馈机制不仅有利于区域和全球尺度荒漠化防治的开展,而且也将为国际气候变化框架条约中相关部分的协商及谈判提供依据。     

Growth and development of Citrus pistils and fruit explants in vitro

Pistils and various fruit explants of Citrus limon L. Burm. f. and Citrus sinensis L. Osbeck were cultivated in vitro . Basal medium as well as medium supplemented with IAA, GA₃ or benzylaminopurine, supported growth of all explants for more than one year. Pistils did not enlarge considerably, but gave rise to active callus growth; callus proliferation and viability was enhanced by all hormones. Culture of fruit slice explants resulted, in addition to peel hypertrophy and callus proliferation, in a marked growth of two distinct types of juice vesicles. The growth of juice vesicle explants was promoted by all three growth hormones. – It is suggested that the successfully prolonged in vitro culture of various fruit explants, and especially of juice vesicles, may aid in studies of fruit development and physiology.