Age of sex-determining mechanisms in vertebrates

Certain characteristic patterns of physiologic sex determination are not causally linked with types of genic and chromosomal constitution (XX-XY or ZW-ZZ). The observed widespread but not universal parallelism in the distribution of genetic and physiologic patterns among vertebrate groups expresses genealogic relationship. On the basis of this interpretation one may estimate the approximate evolutionary age of the mechanism of genetic sex determination. It is concluded that in all tetrapod vertebrates these mechanisms originated during the Jurassic period. Environmental conditions seem to affect the progress of this evolution.     

A devonian tetrapod from north america

An early tetrapod fossil from the Upper Devonian of Pennsylvania (Catskill Formation) extends the temporal range of tetrapods in North America and suggests that they attained a virtually global equatorial distribution by the end of the Devonian. Derived features of the shoulder girdle indicate that appendicular mechanisms of support and propulsion were well developed even in the earliest phases of tetrapod history. The specialized morphology of the pectoral skeleton implies that the diversity of early tetrapods was great and is suggestive of innovative locomotor patterns in the first tetrapods.     

New arrangement of interrenal and chromaffin tissues of teleost fishes

An unusual morphologic arrangement of interrenal and chromaffin tissues has been observed in two families of teleost fishes. In most teleosts in which these cell types occur together in association with the postcardinal veins and their branches, the chromaffin cells are located between the lumen of the vein and the interrenal cells. This typical relationship is reversed in some of the Labridae and Scaridae.     

New fossil evidence on the sister-group of mammals and early mesozoic faunal distributions

Newly discovered remains of highly advanced mammal-like reptiles (Cynodontia: Tritheledontidae) from the Early Jurassic of Nova Scotia, Canada, have revealed that aspects of the characteristic mammalian occlusal pattern are primitive. Mammals and tritheledontids share an homologous pattern of occlusion that is not seen in other cynodonts. The new tritheledontids represent the first definite record of this family from North America. The extreme similarity of North American and African tritheledontids supports the hypothesis that the global distribution of terrestrial tetrapods was homogeneous in the Early Jurassic. This Early Jurassic cosmopolitanism represents the continuation of a trend toward increased global homogeneity among terrestrial tetrapod communities that began in the late Paleozoic.     

肾上腺皮质肿瘤良恶性鉴别方法探究

肾上腺皮质肿瘤（Adrenocortical Tumor,ACT）是一种常见的肿瘤,存在于人体的内分泌系统中,并且是引发肾上腺皮质癌（Adrcnocortical Carcinoma,ACC）进而导致死亡的主要原因.经典的＂Weiss系统＂在诊断明确性上存在种种无法解决的问题,但随着科技水平的发展,人们开始探索新的途径来鉴别ACT的良恶性,于是开始有了影像学和分子生物学技术等特异性的检查方法,从而进一步增强了诊断的明确性.现通过对比的方式,探究肾上腺皮质肿瘤（Adrenocortical Tumor,ACT）影像学检查和分子生物学技术检查的结果,从而能更准确地鉴别其良恶性.     

Insect diversity in the fossil record

Insects possess a surprisingly extensive fossil record. Compilation of the geochronologic ranges of insect families demonstrates that their diversity exceeds that of preserved vertebrate tetrapods through 91 percent of their evolutionary history. The great diversity of insects was achieved not by high origination rates but rather by low extinction rates comparable to the low rates of slowly evolving marine invertebrate groups. The great radiation of modern insects began 245 million years ago and was not accelerated by the expansion of angiosperms during the Cretaceous period. The basic trophic machinery of insects was in place nearly 100 million years before angiosperms appeared in the fossil record.     

Triassic vertebrates of gondwanan aspect from the richmond basin of virginia

A new locality of early Late Triassic age in the Richmond basin of east-central Virginia has yielded abundant remains of a diversified assemblage of small to medium-sized tetrapods that closely resembles Southern Hemisphere (Gondwanan) assemblages in the predominance of certain synapsids. Associated palynomorphs indicate an early middle Carnian age for the fossiliferous strata. The discovery suggests that previously recognized differences between tetrapod assemblages of early Late Triassic age from Gondwana and Laurasia at least in part reflect differences in stratigraphic age, rather than geographic separation.     

Origin of the Tetrapod Limb

The paired fins of fishes were first used as props and supports for resting on the bottom; these were later used in a clumsy, walking manner, and this behavior perforce began first in the water, because the weak props could not support the animals without the water bouyancy; increased perfection of the mechanics of walking took place in the shallows; which was a refuge from the chief predators; the land was also attractive as a haven and as a source of food; the first vertebrate invaders of land probably had fins, and these became legs by enlargement of the fin base and loss of fin rays; these original limbs and girdles were weak and probably underwent a considerable period of evolution in swampy country; later they were perfected by further selection when it became necessary for early amphibians to move across dry land because of a failing local water supply. This syllogism conforms to the known behavior and capabilities of fishes and amphibians and to the general facts of zoology and paleontology. It suggests that common, continuous activities and stresses-escape from enemies and food getting-led to the origin of the tetrapod limb. This obviates the necessity for explaining how discontinuous and somewhat catastrophic events, such as the drying up of water bodies, could have led to the origin of limbs, which at the very outset had to be fairly strong. The general theory stated here is fairly clearly implied by Berry (8), who said, "Those fishy pioneers with air-bladders -and paired fins-which, after ages of using their fins for pushing and paddling themselves over mud flats, gradually ventured onto drier and drier ground-where they avoided the competition for food-and the dangers of swarming hordes of ganoid pirates of the waters, were the ancestors of the amphibians."     

无脊椎动物促性腺激素释放激素研究进展

促性腺激素释放激素（gonadotropin-releasing hormone,_GnRH）是下丘脑-垂体-性腺（hypothalamic-pituitary-go-nad,_HPG）轴的关键信息分子,在脊椎动物的性腺发育、性成熟和繁殖功能的维持中起着重要作用。用免疫组织化学、酶联免疫吸附测定以及高效液相色谱等方法在多种无脊椎动物中也检测到了其存在,主要分布于中枢神经以及生殖系统。可见,GnRH在无脊椎动物中具有普遍存在性。目前已至少发现28种类型的GnRH,15种来自脊椎动物,13种来自无脊椎动物。目前,无脊椎动物中除被囊动物外,仅有真蛸、海兔和商乌贼已经获得了GnRH的mRNA序列,其肽链分子结构与脊椎动物的类似。GnRH在无脊椎动物中具有广阔的研究空间,将为无脊椎动物的生殖调控的研究提供参考。     

Brain peptides: what, where, and why?

Within the past decade, a large number of peptides have been described within the vertebrate central nervous system. Some of these peptides were previously known to be present in nonneural vertebrate tissues, as well as in lower species, in which they may serve as primitive elements of intercellular communication prior to the development of neuronal or endocrine systems. In vertebrates, these peptides are thought to have neurotransmitter or neuromodulatory roles and appear to be involved in the regulation of a number of homeostatic systems, although the mechanisms of their actions are still unclear.     

Nuclear and mitochondrial DNA comparisons reveal extreme rate variation in the molecular clock

The discovery that the rate of evolution of vertebrate mitochondrial DNA is rapid, compared to the rate for vertebrate nuclear DNA, has resulted in its widespread use in evolutionary studies. Comparison of mitochondrial and nuclear DNA divergences among echinoid and vertebrate taxa of similar ages indicates that the rapid rate of vertebrate mitochondrial DNA evolution is, in part, an artifact of a widely divergent rate of nuclear DNA evolution. This disparity in relative rates of mitochondrial and nuclear DNA divergence suggests that the controls and constraints under which the mitochondrial and nuclear genomes operate are evolving independently, and provides evidence that is independent of fossil dating for a robust rejection of a generalized molecular clock hypothesis of DNA evolution.     

血红蛋白α链·γ链在脊椎动物不同进化阶段进化速率的计算

利用进化速率较快且较恒定的血纤蛋白肽及假基因来确定类群分歧时间的方法,通过计算脊椎动物（包括鸟类和哺乳类）血红蛋白α链、γ链的进化速率得出,脊椎动物血红蛋白α链、γ链的进化速率并不是恒定的,而是在不同时期具有不同的进化速率;在进化早期进化速率较快,在进化晚期较慢。     

New early Jurassic tetrapod assemblages constrain Triassic-Jurassic tetrapod extinction event

The discovery of the first definitively correlated earliest Jurassic (200 million years before present) tetrapod assemblage (Fundy basin, Newark Supergroup, Nova Scotia) allows reevaluation of the duration of the Triassic-Jurassic tetrapod extinction event. Present are tritheledont and mammal-like reptiles, prosauropod, theropod, and ornithischian dinosaurs, protosuchian and sphenosuchian crocodylomorphs, sphenodontids, and hybodont, semionotid, and palaeonisciform fishes. All of the families are known from Late Triassic and Jurassic strata from elsewhere; however, pollen and spore, radiometric, and geochemical correlation indicate an early Hettangian age for these assemblages. Because all "typical Triassic" forms are absent from these assemblages, most Triassic-Jurassic tetrapod extinctions occurred before this time and without the introduction of new families. As was previously suggested by studies of marine invertebrates, this pattern is consistent with a global extinction event at the Triassic-Jurassic boundary. The Manicouagan impact structure of Quebec provides dates broadly compatible with the Triassic-Jurassic boundary and, following the impact theory of mass extinctions, may be implicated in the cause.     

Genomic organization and deduced amino acid sequence of a putative sodium channel gene in Drosophila

The deduced amino acid sequence of a Drosophila gene isolated with a vertebrate sodium channel complementary DNA probe revealed an organization virtually identical to the vertebrate sodium channel protein; four homologous domains containing all putative membrane-spanning regions are repeated in tandem with connecting linkers of various sizes. All areas of the protein presumed to be critical for channel function show high evolutionary conservation. These include those proposed to function in voltage-sensitive gating, inactivation, and ion selectivity. All 24 putative gating charges of the vertebrate protein are in identical positions in the Drosophila gene. Ten introns interrupt the coding regions of the four homology units; introns with positions conserved among homology units bracket a region hypothesized to be the selectivity filter for the channel. The Drosophila gene maps to the right arm of the second chromosome in region 60D-E. This position does not coincide with any known mutations that confer behavioral phenotypes, but is close to the seizure locus (60A-B), which has been hypothesized to code for a voltage-sensitive sodium channel.     

Evolutionary origins for social vocalization in a vertebrate hindbrain-spinal compartment

The macroevolutionary events leading to neural innovations for social communication, such as vocalization, are essentially unexplored. Many fish vocalize during female courtship and territorial defense, as do amphibians, birds, and mammals. Here, we map the neural circuitry for vocalization in larval fish and show that the vocal network develops in a segment-like region across the most caudal hindbrain and rostral spinal cord. Taxonomic analysis demonstrates a highly conserved pattern between fish and all major lineages of vocal tetrapods. We propose that the vocal basis for acoustic communication among vertebrates evolved from an ancestrally shared developmental compartment already present in the early fishes.     

The genome of the sea urchin Strongylocentrotus purpuratus

We report the sequence and analysis of the 814-megabase genome of the sea urchin Strongylocentrotus purpuratus, a model for developmental and systems biology. The sequencing strategy combined whole-genome shotgun and bacterial artificial chromosome (BAC) sequences. This use of BAC clones, aided by a pooling strategy, overcame difficulties associated with high heterozygosity of the genome. The genome encodes about 23,300 genes, including many previously thought to be vertebrate innovations or known only outside the deuterostomes. This echinoderm genome provides an evolutionary outgroup for the chordates and yields insights into the evolution of deuterostomes.     

Major steps in vertebrate evolution

We have come to the end of our story-a long one, covering some half a billion years, it appears. A modern man or other higher vertebrate has traveled far from the simply built insensate type of creature seen in his ultimate metazoan ancestor among the pterobranchs. The course of this evolutionary progression is far from direct and simple, as some might believe to be the case; it is a trail with many twists and turns. Nor is there the slightest reason to attempt a teleological interpretation; there is no trace of design and direction toward an obvious goal. Quite in contrast, it seems clear in many stages of the series that the changes which have taken place are immediately beneficial ones, strongly subject to selection. Obvious, too, is the fact that special environmental factors, biological and physical, have added unexpected quirks to the story. The development of a motile "tadpole" larva at an early chordate stage led to a sharp shift in an evolutionary sequence which otherwise might have simply ended in a sedate filtering form of tunicate type. The development of plant life on the continents opened up to motile chordates a new environment into which few invertebrates could enter and in which the chordates flourished to progress to the vertebrate level. The need for armor as defense against eurypterid enemies appears to have initiated the development of bony skeletal structures, without which the higher vertebrates could never have developed. The widespread late Paleozoic condition of seasonal drought favored progressive developments which, with the attainment of a reptilian stage, had the happy accidental result of the vertebrate conquest of the land, a conquest aided by the emergence of the insects as a basic food supply. The long period of dinosaur dominance seems to have been responsible for the sharpened wits which made the mammalian descendants of the therapsids competent for terrestrial dominance when the reign of the ruling reptiles ended. The arboreal life of primates was finally abandoned by man, but tree-dwelling had endowed his ancestors with advances in brain, eyes, and hands that were highly advantageous when this relatively feeble creature descended to the ground. It has been a long and tortuous journey; but every stage of it shows its effects in the structures and functions of such an end product as ourselves (Fig. 4).     

Epigenetic transgenerational actions of endocrine disruptors and male fertility

Transgenerational effects of environmental toxins require either a chromosomal or epigenetic alteration in the germ line. Transient exposure of a gestating female rat during the period of gonadal sex determination to the endocrine disruptors vinclozolin (an antiandrogenic compound) or methoxychlor (an estrogenic compound) induced an adult phenotype in the F1 generation of decreased spermatogenic capacity (cell number and viability) and increased incidence of male infertility. These effects were transferred through the male germ line to nearly all males of all subsequent generations examined (that is, F1 to F4). The effects on reproduction correlate with altered DNA methylation patterns in the germ line. The ability of an environmental factor (for example, endocrine disruptor) to reprogram the germ line and to promote a transgenerational disease state has significant implications for evolutionary biology and disease etiology.     

血红蛋白α链、β链在脊椎动物不同进化阶段进化速率的计算

利用进化速率较快且较恒定的血纤蛋白肽及假基因来确定类群分歧时间的方法,通过计算脊椎动物（包括鸟类和哺乳类）血红蛋白α链、γ链的进化速率得出,脊椎动物血红蛋白α链、γ链的进化速率并不是恒定的,而是在不同时期具有不同的进化速率;在进化早期进化速率较快,进化晚期较慢。     

太湖沿岸区几种肉食性鱼类蛋白酶活性的研究

本文对太湖沿岸区几种常见肉食性鱼类的胃蛋白酶和胰蛋白酶活性进行了比较研究，发现它们的胃蛋白酶比活力有显著差异（Ｐ〈０．０１），其中，尤以底栖无脊椎动物食性的黄颡鱼最高，沙塘鳢次之，而以鱼、虾为食的乌鳢、鳜鱼的较低。但它们的胰蛋白酶比活力并无显著性差异（Ｐ〉０．１０）。作者认为，肉食性鱼类９特别是胃发达的）食物的消化主要集中在胃中，胃蛋白酶活性的高低与食物的硬度（钙质的含量）成正相关，而在小肠中，只