Ontogenesis of the pyramidal cell of the mammalian neocortex and developmental cytoarchitectonics: a unifying theory.

The prenatal development of the mammalian neocortex has been analyzed, with the rapid Golgi method, in a variety of experimental animals (hamster, mouse, rat, and cat) and in humans. A new developmental conception of the structural organization of the mammalian neocortex is discussed. Neocortical development begins with the establishment of the primordial plexiform layer (PPL) which precedes and is a prerequisite for the subsequent formation of the cortical plate (CP). The formation of the CP occurs, in its entirety, within the PPL. During its development, three fundamental neuronal events occur: migration, early differentiation, and late maturation. All migrating neurons, travelling on radial glial fibers, reach layer I, develop an apical dendrite, and establish contacts with its elements. These newly differentiated neurons assume similar morphology resembling embryonic pyramidal cells. As such, an early differentiation stage common to all neurons of the CP is established. During the late maturation stage, all CP neurons acquire their specific phenotypic structural and functional features. Only pyramidal neurons retain and expand their original connections with layer I while other neuronal types lose these connections. The pyramidal cell is redefined in developmental terms: the neocortex's pyramidal cell is both structurally and functionally locked into position between layer I and the cortical depth of its soma. During mammalian evolution pyramidal cells are forced to structurally and functionally elongate their apical dendrite outwardly to accommodate an increasing amount of information without losing either their original anchorage to layer I or their cortical depth. This unique property of pyramidal neurons is considered to be a mammalian innovation. Based on these observations, a unifying developmental cytoarchitectonic theory applicable to all mammals is proposed. The theory considers the CP to be a mammalian innovation and to represent a single, stratified, and expanding telencephalic nucleus. The theory envisions the mammalian neocortex as an open biological system capable of progressive expansion by the recruitment and transformation of primitive neurons from upper layer II into pyramidal cells. Hence, the number of pyramidal cell strata increases over the course of mammalian phylogeny. The developmental roles of layer I in the migration of neurons, formation of the CP, unique morphology of pyramidal cells, and overall structural organization of the mammalian neocortex are emphasized.     

人白细胞介素12在哺乳动物细胞中的稳定表达及其生物活性的研究

目的采用遗传基因工程方法获得具有生物活性的人白细胞介素12,探索其治疗肿瘤和慢性肝炎的可行性。方法采用已克隆的国人IL-12基因序列,利用内部核糖体切入位点(IRES)完成IL-12P35、P40双亚基共表达载体的构建,通过转染CHODHFR缺陷细胞,双抗夹心ELISA法筛选阳性克隆,MTX加压扩增,PCR检测其基因整合,T淋巴细胞增殖和诱生γ干扰素实验检测其生物活性。结果获得了稳定高效表达人IL-12的工程细胞系,表达产物为70×103左右的糖蛋白。结论本研究得到的基因重组人IL-12具有良好的生物活性,有强的诱导产生γ干扰素的能力和诱导活化T淋巴细胞增殖能力。     

Reconstruction of the ancestral karyotype of eutherian mammals

Applying the parsimony principle, i.e. that chromosomes identical in species belonging to different taxa were likely to be present in their common ancestor, the ancestral karyotype of eutherian mammals (about 100 million years old) was tentatively reconstructed. Comparing chromosome banding with all ZOO-FISH data from literature or studied by us, this reconstruction can be proposed with only limited uncertainties. This karyotype comprised 50 chromosomes of which 40–42 were acrocentrics. Ten ancestral pairs of chromosomes were homologous to a single human chromosome: 5, 6, 9, 11, 13, 17, 18, 20, X and Y (human nomenclature). Nine others were homologous to a part of a human chromosome: 1p+q (proximal), 1q, 2p+q (proximal), 2q, part of 7, 8q, 10p, 10q and 19p (human nomenclature). Finally, seven pairs of chromosomes, homologs to human chromosomes 3 + 21, 4 + 8p, part of 7 + 16p, part of 12 + part of 22 (twice), 14+15, 16q+19q, formed syntenies disrupted in man. This revised version was published online in July 2006 with corrections to the Cover Date.     

云南省大理小型哺乳动物种类的调查

目的　调查云南省大理小型哺乳动物的种类。方法　 2 0 0 0～ 2 0 0 3年对云南省大理小型哺乳动物种类和分布进行了调查。结果　捕获小型哺乳动物 2 2 68只 ,初步查明的种类有 2 4种 ,隶属 3目 6科 13属 ,以啮齿动物为主。结论　大理小型哺乳动物种类丰富 ,至少 17种小兽与多种动物源性疾病的传播有关     

Light-induced phase-shifts in the circadian expression rhythm of mammalian period genes in the mouse heart

To investigate the molecular mechanism that regulates circadian rhythms in mammalian peripheral tissues, we examined the phase shifts evoked by light exposure in the circadian mRNA expression rhythms of mammalian Period genes (mPer1, mPer2 and mPer3) and a clock-controlled gene Dbp, in the mouse heart, by Northern blot analysis. The light pulse did not induce any acute mRNA expression of mPer in the heart, but the pulse gave rise to phase shifts in the circadian mRNA rhythms. On the first day after the exposure, only mPer1 mRNA showed a phase shift, whereas obvious phase shifts were not observed in the rhythms of mPer2, mPer3 and Dbp mRNAs. On the second day, phase shifts occurred to a similar extent in the mRNA rhythms of all four genes examined. The rhythm of mPer1 mRNA shifted fastest among those of the three mPers. Therefore mPer1 seems to play an important role in phase resetting of mammalian peripheral oscillators. Immediate responses to light pulses in mRNA expression of mPers may not be required for phase shifting of peripheral circadian oscillators. Our findings suggest that mammals require more than one day to have peripheral oscillators entrained to a new daily schedule.     

Adaptive suckling

The process of “adaptive suckling” has evolved appropriate to the needs of different mammal species. It is related to the maturity of the newborn, nutritional requirements, the number of offspring, the need for sensory stimulation, etc. Examples are given of the following species—the echidna, the kangaroo, the blue whale and.the seal. Its relevance to modern man is discussed.     

Multiple Strains of Coxiella burnetii are Present in the Environment of St. Paul Island,Alaska

In 2010, Coxiella burnetii was identified at a high prevalence in the placentas of Northern fur seals (Callorhinus ursinus) collected at a single rookery on St. Paul Island Alaska; an area of the United States where the agent was not known to be present. As contamination was hypothesized as a potential cause of false positives, but nothing was known about environmental C. burnetii in the region, an environmental survey was conducted to look for the prevalence and distribution of the organism on the island. While environmental prevalence was low, two strains of the organism were identified using PCR targeting the COM1 and IS1111 genes. The two strains are consistent with the organism that has been increasingly identified in marine mammals as well as a strain type more commonly found in terrestrial environments and associated with disease in humans and terrestrial animals. Further work is needed to elucidate information regarding the ecology of this organism in this region, particularly in association with the coastal environment.     

内蒙古小型兽类巴尔通体感染情况调查

目的 了解我国内蒙古部分地区小型兽类的巴尔通体(Bartonella)感染情况,为该地区人群巴尔通体感染的预防控制提供科学依据.方法 2012、2013年用夹夜法在内蒙古不同地区捕获小型兽类,无菌操作取鼠肝和脾,用聚合酶链反应(PCR)检测巴尔通体,对阳性产物测序,将所测核酸序列提交到GenBank,做相似性比较及序列分析.同时分别用肝和脾各30份样品分离培养巴尔通体,疑似菌株提取DNA,对gltA基因测序并根据序列进行系统发育分析,确定巴尔通体属种,并分析不同脏器、不同鼠种的阳性率.结果 2012年在内蒙古锡林郭勒盟二连浩特市共捕鼠8种117只,各鼠种均培养出巴尔通体菌,培养阳性率为56.41％(66/117),肝脏DNA直接PCR阳性率为57.26％(67/117),二者差异无统计学意义(P=0.945).30份肝样品培养阳性21份,30份脾样品培养阳性13份,二者差异亦无统计学意义(P=0.331).2013年捕获并培养分离小型兽类13种86只,有8种检出巴尔通体,培养阳性率为38.37％(33/86),其中达乌尔黄鼠最高(75.00％),其次为五趾跳鼠(71.43％)和布氏田鼠(64.29％).经分析达乌尔黄鼠、五趾跳鼠与布氏田鼠的巴尔通体阳性率差异无统计学意义(P=0.883).序列分析表明内蒙古部分地区小型兽类中共检出4个巴尔通体种群:B.jaculi、B.grahamii、B.washoensis和B.vinsonii,有明显的宿主特异性.结论 巴尔通体在内蒙古部分地区小型兽类中广泛存在,存在对人群致病的风险,序列分析显示出巴尔通体基因型别的多样性,为内蒙古及我国北方其他地区巴尔通体的研究奠定了基础.     

A new scenario of the evolutionary derivation of the mammalian diaphragm from shoulder muscles

The evolutionary origin of the diaphragm remains unclear, due to the lack of a comparable structure in other extant taxa. However, recent researches into the developmental mechanism of this structure have yielded new insights into its origin. Here we summarize current understanding regarding the development of the diaphragm, and present a possible scenario for the evolutionary acquisition of this uniquely mammalian structure. Recent developmental analyses indicate that the diaphragm and forelimb muscles are derived from a shared cell population during embryonic development. Therefore, the embryonic positions of forelimb muscle progenitors, which correspond to the position of the brachial plexus, likely played an important role in the evolution of the diaphragm. We surveyed the literature to reexamine the position of the brachial plexus among living amniotes and confirmed that the cervico‐thoracic transition in ribs reflects the brachial plexus position. Using this osteological correlate, we concluded that the anterior borders of the brachial plexuses in the stem synapsids were positioned at the level of the fourth spinal nerve, suggesting that the forelimb buds were laid in close proximity of the infrahyoid muscles. The topology of the phrenic and suprascapular nerves of mammals is similar to that of subscapular and supracoracoid nerves, respectively, of the other amniotes, suggesting that the diaphragm evolved from a muscle positioned medial to the pectoral girdle (cf. subscapular muscle). We hypothesize that the diaphragm was acquired in two steps: first, forelimb muscle cells were incorporated into tissues to form a primitive diaphragm in the stem synapsid grade, and second, the diaphragm in cynodonts became entrapped in the region controlled by pulmonary development.     

Cultural adaptation, compounding vulnerabilities and conjunctures in Norse Greenland

Norse Greenland has been seen as a classic case of maladaptation by an inflexible temperate zone society extending into the arctic and collapse driven by climate change. This paper, however, recognizes the successful arctic adaptation achieved in Norse Greenland and argues that, although climate change had impacts, the end of Norse settlement can only be truly understood as a complex socioenvironmental system that includes local and interregional interactions operating at different geographic and temporal scales and recognizes the cultural limits to adaptation of traditional ecological knowledge. This paper is not focused on a single discovery and its implications, an approach that can encourage monocausal and environmentally deterministic emphasis to explanation, but it is the product of sustained international interdisciplinary investigations in Greenland and the rest of the North Atlantic. It is based on data acquisitions, reinterpretation of established knowledge, and a somewhat different philosophical approach to the question of collapse. We argue that the Norse Greenlanders created a flexible and successful subsistence system that responded effectively to major environmental challenges but probably fell victim to a combination of conjunctures of large-scale historic processes and vulnerabilities created by their successful prior response to climate change. Their failure was an inability to anticipate an unknowable future, an inability to broaden their traditional ecological knowledge base, and a case of being too specialized, too small, and too isolated to be able to capitalize on and compete in the new protoworld system extending into the North Atlantic in the early 15th century.