Independent origins of middle ear bones in monotremes and therians

A dentary of the oldest known monotreme, the Early Cretaceous Teinolophos trusleri, has an internal mandibular trough, which in outgroups to mammals houses accessory jaw bones, and probable contact facets for angular, coronoid, and splenial bones. Certain of these accessory bones were detached from the mandible to become middle ear bones in mammals. Evidence that the angular (homologous with the mammalian ectotympanic) and the articular and prearticular (homologous with the mammalian malleus) bones retained attachment to the lower jaw in a basal monotreme indicates that the definitive mammalian middle ear evolved independently in living monotremes and therians (marsupials and placentals).     

A new mammaliaform from the early Jurassic and evolution of mammalian characteristics

A fossil from the Early Jurassic (Sinemurian, approximately 195 million years ago) represents a new lineage of mammaliaforms, the extinct groups more closely related to the living mammals than to nonmammaliaform cynodonts. It has an enlarged cranial cavity, but no postdentary trough on the mandible, indicating separation of the middle ear bones from the mandible. This extends the earliest record of these crucial mammalian features by some 45 million years and suggests that separation of the middle ear bones from the mandible and the expanded brain vault could be correlated. It shows that several key mammalian evolutionary innovations in the ear region, the temporomandibular joint, and the brain vault evolved incrementally through mammaliaform evolution and long before the differentiation of the living mammal groups. With an estimated body weight of only 2 grams, its coexistence with other larger mammaliaforms with similar "triconodont-like" teeth for insectivory within the same fauna suggests a great trophic diversity within the mammaliaform insectivore feeding guild, as inferred from the range of body sizes.     

An ossified Meckel's cartilage in two Cretaceous mammals and origin of the mammalian middle ear

An ossified Meckel's cartilage has been recovered from two early Cretaceous mammals from China. This element is similar to Meckel's cartilage in prenatal and some postnatal extant mammals and indicates the relationship of Meckel's cartilage with the middle ear in early mammals. The evidence shows that brain expansion may not be the initial factor that caused the separation of postdentary bones from the dentary as middle ear ossicles during mammalian evolution. The failure of the dentary to seize reduced postdentary elements during ontogeny of early mammals is postulated as an alternative mechanism for the separation. Modifications of both feeding and hearing apparatuses in early mammals may have led to the development of the definitive mammalian middle ear.     

Blastocyst axis is specified independently of early cell lineage but aligns with the ZP shape

The mechanisms controlling the establishment of the embryonic-abembryonic (E-Ab) axis of the mammalian blastocyst are controversial. We used in vitro time-lapse imaging and in vivo lineage labeling to provide evidence that the E-Ab axis of the mouse blastocyst is generated independently of early cell lineage. Rather, both the boundary between two-cell blastomeres and the E-Ab axis of the blastocyst align relative to the ellipsoidal shape of the zona pellucida (ZP), an extraembryonic structure. Lack of correlation between cell lineage and the E-Ab axis can be explained by the rotation of the embryo within the ZP.     

甲骨文披露的薏苡文化——作物产量构成公式三因素之密度、株数判定及证考Ⅰ

薏苡(Coix)作为我国最早栽培的作物品种,这一事实可从许多证据得到证考;甲骨文作为最早记载人类活动的文字之一,不仅推动了人类文明的进程,也最早记载了作物产量株的构成。文章通过大量文献资料对这一事实进行了判定及证考,推定出了甲骨文记载的作物产量公式的要素,即密度(穗数)、穗粒数、籽粒重(千粒重),是最早记载作物产量构成公式的三要素,鉴于篇幅所限,本文只讨论密度(株、穗数)之内容。     

Fate-restricted neural progenitors in the mammalian cerebral cortex

During development of the mammalian cerebral cortex, radial glial cells (RGCs) generate layer-specific subtypes of excitatory neurons in a defined temporal sequence, in which lower-layer neurons are formed before upper-layer neurons. It has been proposed that neuronal subtype fate is determined by birthdate through progressive restriction of the neurogenic potential of a common RGC progenitor. Here, we demonstrate that the murine cerebral cortex contains RGC sublineages with distinct fate potentials. Using in vivo genetic fate mapping and in vitro clonal analysis, we identified an RGC lineage that is intrinsically specified to generate only upper-layer neurons, independently of niche and birthdate. Because upper cortical layers were expanded during primate evolution, amplification of this RGC pool may have facilitated human brain evolution.     

不同类型玉米耐密性分析及对主要性状的影响

通过对不同穗型品种耐密性及密度对主要农艺性状影响的研究表明,密度对株高、倒伏的影响为大穗型品种中穗型品种小穗型品种;穗长、穗行数受密度影响最大的为大穗型品种,其次为中穗型品种;行粒数对密度的响应表现为中穗型品种小穗型品种大穗型品种;先玉335的适宜密度9.00万~9.75万hm-2,正大12为7.50万~8.25万hm-2,宁玉12为6.00万~6.75万hm-2。     

Spontaneous middle ear muscle activity in man: a rapid eye movement sleep phenomenon

Changes in compliance of the tympanic membrane have been detected in normal human sleep, presumably due to spontaneous contraction of the stapedius and tensor tympani muscles of the middle ear. In the waking state, these muscles generally respond to loud sound (middle ear reflex). Middle ear muscle activity typically erupts before or at the onset of rapid eye movement (REM) sleep and persists throughout the REM period in a discontinuous pattern resembling that exhibited by rapid eye movements. Approximately 80 percent of all nocturnal middle ear muscle activity is contained in REM sleep. Half of the remaining 20 percent occurs in the 10-minute intervals just prior to the onset of REM sleep. Middle ear muscle activity is often associated with other phasic events such as momentary enhancement of electromyogram inhibition, apnea, and K complexes. Rapid eye movements and middle ear muscle activity, though significantly correlated in REM sleep, are not always simultaneous.     

大麦不同粒位粒重和蛋白质含量及发芽整齐度研究

测定了大麦不同穗数株及5个品种（系）不同粒位（顶部、中部和底部）籽粒的粒重、蛋白质含量和发芽率。结果表明：不同穗数株及品种（系）各粒位间籽粒千粒重的差异表现相同的趋势，即中部最大，顶部和底部较小。不同穗数株主茎穗各粒位籽粒蛋白质含量的最大值，1穗株为顶部，2穗株为中部，3穗株则为底部；各品种（系）主茎穗和分蘖穗不同粒位蛋白含量加权平均值均以秀麦3号为最大，97－33最小，且主茎穗各粒位蛋白含量以顶部为最高，不同穗数株各粒位籽粒发芽速度均以顶部最快，中部和底部相对较慢；品系99－18的发芽整齐度最好，吕系92－11发芽最慢且发芽率最低。     

Temperature measurements from oxygen isotope ratios of fish otoliths

Measurements have shown that the temperature of a fish's habitat can be deduced from the Oxygen isotope ratio of its otoliths (ear bones). Isotope ratios Obtained from fossil otoliths indicate a water temperature which agrees wiht that found by isotope measurements on associated benthonic foraminifera.     

Pressure regulation in the middle ear cavity of sea lions: a possible mechanism

The mucosa lining the cavity of the middle ear of sea lions contains a complex network of venous channels and sinuses. During dives the pressure within the middle ear may be equalized with that in the external auditory meatus either by the distention or depression of the mucosa due to the presence or absence of blood in the sinuses.     

不同播期播量对不同类型超级小麦产量构成因子的影响

以大穗型(01-35、8355)、中间型(62008、4133-2)和多穗型(988044、02-48)超级小麦品种(系)为试材,研究其适宜播期和播量。结果表明,大穗型品种最佳播期10月15日,中间型、多穗型品种最佳播期10月5日,播期对单位面积穗数的影响差别最高可达15%以上,对穗粒数、千粒重和产量的影响差别均在13%以下;播量对其各项指标的影响差别均在5%以下,3种类型的品种均以中、高密度产量较高。播期对超级小麦产量各构成因素的影响大于播量。     

计算玉米产量方法的探讨

1984至1986年对垦区参加全省联合区域试验的早熟、中早熟、中熟三个熟期组39个组合,进行“湿果穗称重取样法”和“实收法”计算产量数据进行差异显著性测定、变量分析、回归系数显著性测定、相关系数显著性测定。两种计算产量方法精确度基本相同,在玉米产量试验中可用“湿果穗称重取样法”代替“实收法”计算产量。     

黑龙江省玉米品种农艺性状与单株粒重的灰色关联分析

选取黑龙江省中、晚熟玉米对照品种及杂交组合共160份,采用灰色关联分析方法,对影响玉米产量(单株粒重)的主要农艺性状进行研究。结果表明,与玉米单株粒重相关的农艺性状中,穗粗、百粒重和穗长最为重要,整体关联度排序为:穗粗>百粒重>穗长>生育期>行粒数>吐丝期>散粉期>穗位>株高>穗行数>出苗期>出籽率,这说明目前玉米新品种选育应以果穗粗、长,百粒重大且穗行数多为主,以其他农艺性状适中为目标,协调各相关因素,提高产量。本试验利用大量品种(组合)明确玉米主要农艺性状对产量的贡献,为选育高产玉米新品种提供了理论参考依据。     

Cynodont reptile with incipient mammalian jaw articulation

A diagnostic mammalian character is jaw articulation between squamosal and dentary bones, replacing the quadrate-articular joint of reptiles. A newly discovered Argentinian Middle Triassic form shows, for the first time in an ancestral reptile, definite evidence of a squamosal-dentary articulation supplementary to the persistent primitive connection.     

晚霜冻害对不同类型小麦产量性状的影响

采用人工智能霜箱模拟自然界晚霜冻害过程,对大穗(s9538、兰考906)、中穗(豫麦21号、陕225)、多穗(临汾7203、鲁资0885299)类型的小麦品种在经历低温处理后产量因素的变化进行了研究.结果表明,多穗型小麦(临汾7203、鲁资0885299)在经历晚霜冻害后比另外两类小麦表现增产,其中单株穗数较对照增加幅...     

小麦超高产基因型的株型结构问题

 从小麦的株型结构、目前超高产小麦基因型的株型结构和超高产基因型株型结构改良的策略3个方面,对小麦超高产基因型的株型结构问题进行了讨论。通过对小叶矮秆中大穗高密度松散型、中叶中高秆大穗中密度型和大叶中矮秆大穗紧凑低密度型3种不同类型超高产基因型株型结构的主要性状特征及生产能力分析认为,上述3种类型都具备超高产的产量能力,但小叶矮秆中大穗高密度松散型产量潜力最高。     

Temporal bone preservation in a 2600-year-old Egyptian mummy

Perforated eardrums in the preserved temporal bones of a mummified Egyptian male in otherwise normal middle ears offer new evidence of acute otitis media and probable defective hearing among ancient Egyptians.     

Age of bed v, olduvai gorge, Tanzania

Various finds of hominid remains in the Olduvai Gorge, Tanzania, have focused interest upon the age of the deposits in the sequence of six beds. After bed I was dated by the potassium-argon decay method, an absolute date of 10,400 years has now been obtained with the radiocarbon method from a sample of mammalian bones for bed V.     

影响家畜耳型变异遗传位点的研究进展

作为家畜的一个重要性状,耳型是家畜品种鉴定的重要指标,家畜小耳畸形还可作为人耳疾病研究的动物模型.目前,利用全基因组连锁分析、关联研究和基因表达数据,在家畜上鉴定到影响耳朵大小、外耳直立性的候选基因主要包括MSRB3和PPARD;特别是PPARD基因内的一个错义突变(G＞A,G32E)被认为是影响家猪耳朵大小的因果突变...