Fire and competition in Australian heath: a conceptual model and field investigations

Abstract. We describe a model of heath vegetation, in which species were classified into five functional groups based on characteristics of their propagule pools, post-fire growth, timing and mode of reproduction and competitive status. The model assumes no recruitment without fire and a simple competitive hierarchy based on vertical stature. A critical feature of the model is an initial post-fire window of 5–6 yr in which competition from overstorey species on understorey species is reduced. Understorey functional groups differ in their ability to exploit this window. In the field, we tested five predictions derived from the model: (a) overall species richness of understorey varies inversely with overstorey density as a result of a trend in richness of woody species, but not in herbaceous species; (b) where an overstorey was present in the previous fire interval, post-fire population density is reduced in a functional group of understorey serotinous resprouting shrubs, but not in a group of understorey obligate-seeding shrubs with soil seed banks; (c) in understorey serotinous resprouting shrubs, post-fire regrowth in resprouting individuals is adversely affected by the presence of an overstorey in the preceding fire interval; (d) in understorey serotinous resprouting shrubs, levels of pre-fire propagules are lower in the presence of an overstorey, reducing the density of post-fire recruits; and (e) in understorey serotinous resprouting shrubs, recruitment relative to the pre-fire population is unaffected by overstorey species within the window of reduced competition. Of these, three tests (a,b,d) supported the model, one (e) may support the model, but the results were inconclusive and one (c) did not support the model. Limitations and further applications of the model are discussed. Our results suggest that maintenance of high densities of overstorey populations is in conflict with conservation of some understorey species. Models of the type we propose will help identify and resolve such conflicts and promote the judicious use of fire to maintain full species diversity of plant communities.     

PEAK SHIFTS AND POLYMORPHISM DURING PHASE THREE OF WRIGHT'S SHIFTING-BALANCE PROCESS

The third phase of Wright's shifting-balance theory involves the export of adaptive gene combinations from one subpopulation to another. Previous results have demonstrated that this can occur at very low migration rates, but it has been argued that this simply reflects the ability of migration to overcome selection and fix any (even deleterious) alleles. Here, previous analyses are extended by concentrating on the critical balance between forward and reverse migration rates that still allows phase III to proceed. It is shown that selective advantage, dominance, recombination rate, and the number of loci all affect the ability of a genotype to invade and become fixed in a new subpopulation, but it is unlikely that phase III will occur in the absence of differential migration unless the invading genotype consists of a few dominant loci with a large selection advantage, spreading into a few populations of lower fitness. Therefore, as was envisioned by Wright, differential migration from more to less fit populations will be necessary for phase III to occur under most circumstances.     

Evaluation of five strategies for obtaining a core subset from a large genetic resource collection of durum wheat

The use of plant genetic resources contained in a large collection may be enhanced by specifying subsamples, called core samples. Five strategies for selecting a core sample from a collection of 3000 durum wheat accessions were applied and evaluated using four qualitative and eight quantitative spike characters. Each of the following strategies generated about 500 accessions for the core sample: random, random-systematic according to chronology of entry of the accessions into the collection, stratified by countryof-origin, stratified by log frequency by country-of-origin, and stratified by canonical variables. The first three strategies produced samples representative of the whole collection, but the remaining two produced the desired effect of increasing frequencies from less-represented countries-of-origin for several characters. The stratified canonical sample increased phenotypic variances. The quality of core samples is dependent upon good passport and evaluation data to partition the collection. The multivariate approach is extremely useful, but requires considerable data from the whole collection. Ecogeographic origin may be used in the absence of evaluation data on several characters to select useful core samples.     

Influence of liposome charge and composition on their interaction with human blood serum proteins

The roles of sulfhydryl and disulfide groups in the specific binding of synthetic cannabinoid CP-55,940 to the cannabinoid receptor in membrane preparations from the rat cerebral cortex have been examined. Various sulfhydryl blocking reagents including p-chloromercuribenzoic acid (p-CMB), N-ethylmaleimide (NEM), o-iodosobenzoic acid (o-ISB), and methyl methanethiosulfonate (MMTS) inhibited the specific binding of [³H]CP-55,940 to the cannabinoid receptor in a dose-dependent manner. About 80–95% inhibition was obtained at a 0.1 mM concentration of these reagents. Scatchard analysis of saturation experiments indicates that most of these sulfhydryl modifying reagents reduce both the binding affinity (K_d) and capacity (B_max). On the other hand, DL-dithiothreitol (DTT), a disulfide reducing agent, also irreversibly inhibited the specific binding of [³H]CP-55,940 to the receptor and about 50% inhibition was obtained at a 5 mM concentration. Furthermore, 5mM DTT was abelt to dissociate 50% of the bound ligand from the ligand-receptor complex. The marked inhibition of [³H]CP-55,940 binding by sulfhydryl reagents suggests that at least one free sulfhydryl group is essential to the binding of the ligand to the receptor. In addition, the inhibition of the binding by DTT implies that besides free sulfhydryl group(s), the integrity of a disulfide bridge is also important for [³H]CP-55,940 binding to the cannabinoid receptor.     

Immunocytochemical approach to the structure of human blood group B and H glycoconjugate antigens in the three days old rat cochlea

The possible structure of human blood-group antigens, as found in cochlear hair cells of 3-day-old rats, is suggested. Data were obtained from immunocytochemical studies using 77 antibodies against the major human blood group antigens of the ABO, H, I and Lewis genetic systems. Neither the anti-A-related nor the anti-Lewis-related antibodies showed any positive immunoreaction on hair cells. In contrast, anti-B, anti-AB and anti-H antibodies displayed specific positive immunoreactive patterns on the hair cells. The results suggest that, in immature hair cells, two main glycoconjugate structures of the lactoseries are present: H type 2 antigen, which is the precursor of the B type 2 antigen, and the B type 2 antigen itself. Similar H and B carbohydrate structures have been reported in rat olfactory receptors. The type 2 glycoconjugates carrying these H and B antigens of auditive and olfactory receptors are resistant to fixation and paraffin embedding, suggesting that they might be glycoproteins. These auditive and olfactory H and B antigens must be different from the B-related antigens that are expressed by pseudo-unipolar neurons of rat posterior root ganglia, that are built from type 4 core chains, and that are destroyed by routine paraffin embedding procedures.     

Differentiation of Rickettsia japonica by Restriction Endonuclease Fragment Length Polymorphism Using Products of Polymerase Chain Reaction Amplification with Rickettsia rickettsii 190-Kilodalton Surface Antigen Gene Primers

Restriction fragment length polymorphism of polymerase chain reaction (PCR) amplification products differentiated Rickettsia japonica, a causative agent of Oriental spotted fever, from other spotted fever group (SFG) rickettsiae. Primer pair Rr190. 70p and Rr190. 602n of R. rickettsii 190-kDa antigen gene sequence primed genomic DNAs obtained from R. japonica, type strain YH and strains NT, NK, YKI, and TKN. The products were cleaved by PstI but not by AfaI restriction endonuclease. The PstI digestion pattern of PCR-products amplified from all strains of R. japonica was identical and easily differentiated from that of other SFG rickettsiae. The present study demonstrated a genotypic difference between R. japonica and other pathogenic SFG rickettsiae.     

羟自由基对人红细胞磷脂酰乙醇胺脂质体相变性质的影响

研究了过氧化氢与亚铁离子体系产生的羟自由基对人红细胞膜磷脂酸乙醇胺(PE)脂质体相变性质的影响.结果表明,羟自由基导致脂质体不饱和脂肪酸链的含量明显降低和丙二醛(MDA)含量显著升高,同时其膜流动性随之下降.在室温下,羟自由基诱使PF脂质体冰冻断裂面出现脂质颗粒,说明羟自由基通过脂质过氧化作用可促进PE脂质体从脂双层转变为非双层结构.     

中国菌物分类学和多样性研究的历史与现状概况

我国菌物分类学研究始于20世纪初,经过百余年的不断探索和发展,取得了丰硕的成果,并逐渐走进世界前列。本研究通过对世界菌物名称信息库Fungal Names进行数据统计,对发现自中国的菌物新物种和中国学者发表菌物新分类单元等数据开展分析,从中揭示中国菌物分类学的历史和发展趋势。过去,一共有2 214位中国学者参与发表了15 626个菌物新分类单元,包括 3个新纲、27个新目及亚目、117个新科及亚科、769个新属及亚属、11 100个新种、322个新种下单元和3 288个新组合。在全球已知的菌物物种中,自中国发现的新物种有10 233种,隶属于 3界13门44纲174目572科2 379属,占全球已知物种多样性的6.84%,居世界第二位。地理分布上,我国西南地区(云南、四川、贵州、西藏)和低纬度的热带、亚热带地区(中国台湾、广东)发现的新物种最多。根据每年发现的新分类单元数量趋势和命名作者的构成,可将中国菌物分类学的发展历史分为五个阶段：外人在华采菌及研究(1750s-1929)、中国菌物分类学起步(1930-1949)、新中国菌物分类学早期发展(1950-1977)、全国性菌物标本采集与研究(1978-2010)、走进世界前列(2011至今)。本研究对每个发展时期的分类学概况和重要历史事件进行了总结和回顾,通过上述综述性研究,有助于系统地了解中国菌物分类学不同阶段的发展趋势和研究概况,为学科当下和未来的发展提供参考。     

血清CEA、G-17、MK、ProGRP与胃癌根治术患者术后复发风险的关系研究

摘要 目的：探讨血清癌胚抗原（CEA）、胃泌素17（G-17）、中期因子（MK）、胃泌素释放肽前体（ProGRP）与胃癌根治术（RG）患者术后复发风险的关系。方法：选取2018年1月～2020年8月新疆医科大学第一附属医院普外科收治的156例胃癌患者为胃癌组,根据RG后是否复发分为复发组和无复发组,另选取同期我院52名健康体检志愿者为对照组。收集胃癌患者临床资料,采用酶联免疫吸附法检测血清CEA、G-17、MK、ProGRP水平。通过单因素和多因素Logistic回归分析RG患者术后复发的影响因素,受试者工作特征（ROC）曲线分析血清CEA、G-17、MK、ProGRP水平对RG患者术后复发的预测价值。结果：与对照组比较,胃癌组血清CEA、G-17、MK、ProGRP水平升高（P＜0.05）。随访2年,失访2例,154例RG患者术后复发率为28.57%（44/154）。多因素Logistic回归分析显示,CEA、G-17、MK、ProGRP升高、TNM分期Ⅲ期、分化程度为低分化、淋巴结转移为RG患者术后复发的独立危险因素（P＜0.05）。ROC曲线分析显示,血清CEA、G-17、MK、ProGRP水平联合预测RG患者术后复发的曲线下面积（AUC）大于CEA、G-17、MK、ProGRP单独预测。结论：血清CEA、G-17、MK、ProGRP水平升高与RG患者术后复发密切相关,可能成为RG患者术后复发的辅助预测指标,且血清CEA、G-17、MK、ProGRP联合预测RG患者术后复发的价值较高。     

乳腺癌根治术患者术前焦虑的影响因素分析及其对术后恢复、细胞免疫功能和生命质量的影响

摘要 目的：分析乳腺癌根治术患者术前焦虑的影响因素,并探讨术前焦虑对患者术后恢复、细胞免疫功能和生命质量的影响。方法：选择我院2020年3月~2021年12月期间收治的拟行乳腺癌根治术的120例患者作为研究对象,术前1 d采用焦虑自评量表（SAS）评估所有患者的焦虑状况,根据是否存在焦虑分为焦虑组和无焦虑组,乳腺癌根治术患者术前焦虑的影响因素采用多因素Logistic回归分析。对比焦虑组和无焦虑组的术后恢复、细胞免疫功能和生命质量情况。结果：120例乳腺癌根治术患者中,有31例患者无术前焦虑,89例患者存在焦虑症状,根据是否存在术前焦虑分为焦虑组（n=89）和无焦虑组（n=31）。乳腺癌根治术患者术前焦虑与年龄、文化程度、家庭人均月收入、付费方式、婚姻状况、家庭支持、既往有无全麻史、术前住院时长、定期体检有关（P<0.05）。多因素Logistic回归分析结果表明：年龄＜60岁、文化程度为小学及其以下、家庭人均月收入＜3000元、婚姻状况为未婚、无家庭支持、既往无全麻史、术前住院时长>1 d是乳腺癌根治术患者术前焦虑的危险因素（P<0.05）。焦虑组的术后首次肛门排气时间、首次下床活动时间、术后住院时间均长于无焦虑组（P<0.05）。两组术后1个月CD3⁺、CD4⁺、CD4⁺/CD8⁺水平升高,且无焦虑组高于焦虑组（P<0.05）,两组术后1个月CD8⁺水平下降,且无焦虑组低于焦虑组（P<0.05）。两组术后1个月生理状况、情感状况、社会/家庭状况、功能状况、附加关注评分和总分下降,且无焦虑组低于焦虑组（P<0.05）。结论：乳腺癌根治术患者术前焦虑发生率较高,其发生受到年龄、文化程度、家庭人均月收入、婚姻状况、家庭支持、既往有无全麻史、术前住院时长等多种因素的影响,可导致患者术后恢复时间延长,细胞免疫功能和生命质量降低。