MICROSAURS AND THE ORIGIN OF CAPTORHINOMORPH REPTILES

Microsaurs are Paleozoic lepospondylous Amphibia with slenderbodies and weak limbs. Their solidly roofed skulls lack oticnotches, have large supratemporals widely separating the squamosalfrom parietal, and double occipital condyles. The stapes consistsof a large footplate and extremely short columella. Vertebraelack intercentra. Originally based on a reptile, Hylonomus lyelli,by Dawson in 1863, the Order Microsauria has long been restrictedto these small amphibians (Romer, 1950). Repeated confusionbetween primitive captorhinomorph reptiles and microsaurs steinsfrom superficial similarities between both skulls and vertebrae.This confusion and occasional microsaur-like vertebrae in earlyCarboniferous deposits have led to suggestions that microsaursare reptilian ancestors (cf. Vaughn, 1962). Captorhinomorphs differ from microsaurs in their small supratemporalbone, single occipital condyle, stapes with long columella reachinga pit in the quadrate and bearing a dorsal process, and dorsalintercentra. Captorhinomorph ancestors were probably not labyrinthodonts,as Vaughn (1960) has pointed out, but they could not have hadthe characteristic specializations of microsaurs. Their sourcemust be sought in forms much closer to crossopterygian fish. Microsaurs resemble both urodeles and gymnophionans in theirdouble occipital joint and otic region. They differ from Lissamphibiain the absence of a non-calcified zone in the teeth. At present,no criteria indicate decisively which structures developed convergently.Microsaurs are possibly but not demonstrably related to theancestry of modern salamanders and caecilians.     

The skull and jaw musculature as guides to the ancestry of salamanders

The fossil record provides no evidence supporting a unique common ancestry for frogs, salamanders and apodans. The ancestors of the modern orders may have diverged from one another as recently as 250 million years ago, or as long ago as 400 million years according to current theories of various authors. In order to evaluate the evolutionary patterns of the modern orders it is necessary to determine whether their last common ancestor was a rhipidistian fish, a very primitive amphibian, a labyrimhodom or a ‘lissamphibian’. The broad cranial similarities of frogs and salamanders, especially the dominance of the braincase as a supporting element, can be associated with the small size of the skull in their immediate ancestors. Hynobiids show the most primitive cranial pattern known among the living salamander families and “provide a model for determining the nature of the ancestors of the entire order. Features expected in ancestral salamanders include: (1) Emargination of the cheek; (2) Movable suspensorium formed by the quadrate, squamosal and pterygoid; (3) Occipital condyle posterior to jaw articulation; (4) Distinct prootic and opisthotic; (5) Absence ol otic notch; (6) Stapes forming a structural link between braincase and cheek. In the otic region, cheek and jaw suspension, the primitive salamander pattern (resembles most closely the microsaurs among known Paleozoic amphibians, and shows no significant features in common with either ancestral frogs or the majority of labyrinth odonts. The basic pattern of the adductor jaw musculature is consistent within both frogs and salamanders, but major differences are evident between the two groups. The dominance of the adductor mandibulae externus in salamanders can be associated with the open cheek in all members of that order, and the small size of this muscle in frogs can be associated with the large otic notch. The spread of different muscles over the otic capsule, the longus head ol the adductor mandibulae posterior in frogs and the superficial head of the adductor mandibulae internus in salamanders, indicates that fenestration of the skull posterodorsal to the orbit occurred separately in the ancestors of the two groups. Reconstruction of the probable pattern of the jaw musculature in Paleozoic amphibians indicates that frogs and salamanders might have evolved from a condition hypothesized for primitive labyrinthodonts, but the presence of a large otic notch in dissorophids suggests specialization toward the anuran, not the urodele condition. The presence of either an einarginated cheek or an embayment of the lateral surface of the dentary and the absence of an otic notch in microsaurs indicate a salamander-like distribution of die adductor jaw muscles. The ancestors of frogs and salamanders probably diverged from one another in the early Carboniferous, Frogs later evolved from small labyrinthodonts and salamanders from microsaurs. Features considered typical of lissamphibians evolved separately in the two groups in the late Permian andTriassic.     

The cranial morphology of Greererpeton burkemorani Romer (Amphibia: Temnospondyli)

The skull of Greererpeton burkemorani Romer, a temnospondyl amphibian from the Upper Mississippian at Greer, West Virginia is described. A detailed account of the stapes of a Mississippian amphibian is given for the first time and its function is discussed. It is suggested that the stapes formed the principal element of support for the back of the braincase and resisted potential dislocation of the otico-occipital region from the skull roof during contraction of the hypaxial musculature.
Greererpeton is included in the Colosteidae and an amended diagnosis of the family is given. Erpetosaurus differs from Colosteus, Greererpeton and Pholidogaster in the pattern of bones in the skull roof and palate, the dentition and the otic region and, consequently, it is removed from the Colosteidae. The Temnospondyli are considered to be a monophyletic group characterized by the development of a connection between the dorsal portion of the occipital arch, the exoccipital bones, and the skull roof. The loxommatids are removed from the Temnospondyli as they retain the plesiomorphic condition of braincase attachment which relies exclusively on derivatives of the auditory capsules.
On the basis of similarities in the structure of the braincase, palate and manus it is suggested that microsaurs are the collateral descendants (sister group) of temnospondyls. This relationship may account for the large number of similarities in the three living groups of Amphibia: Anura are generally believed to have descended from temnospondyls, while the Urodela and Apoda are often considered to have descended from microsaurs. These systematic conclusions endorse the recent suggestions that neither the Lepospondyli nor the Labyrinthodontia are natural groups, and both terms should be abandoned.     

Electron microscopy of rotary shadowed vinculin and vinculin complexes

Chicken gizzard smooth muscle vinculin, purified according to the method of Feramisco & Burridge (1980), was examined by rotary shadowing and electron microscopy. Individual vinculin molecules have two domains: a globular head with a diameter of 8.0 nm, and a tail 20 nm long. In high salt, vinculin self-associates into multimers containing two to six individual molecules. These molecules associate head to head and tail to tail, but the tail to tail association appears to be favored. Electron microscopy of the approximately 100,000 Mr major fragment of vinculin was performed. The tail region appeared to be cleaved off, making the head region less compact.     

Properties of pyruvate kinase in the lobster

Pyruvate kinase from the tail muscle and claw muscle of a lobster (H. vulgaris) has been purified by ammonium sulfate precipitation, chromatography on DEAE-cellulose and Sephadex G-200 gel filtration. The overall procedure results in a 200-fold purification with a yield of 70%. The molecular weights of the enzymes were found to be 254 000 ± 10% (tail muscle) and 266 000 ± 10% (claw muscle). Moreover both enzymes have a tetrameric structure with a molecular mass of 65 000 ± 10% for the subunit. Kinetic properties of the enzymes are such that a regulation of anaerobic glycolysis through allosteric modulation of pyruvate kinase activity appears to be non-functional for the two tissues investigated.     

鼠尾胶原蛋白提取、分离、纯化方法的建立及鉴定

目的建立一种高效提取、分离、纯化鼠尾胶原蛋白的方法。方法通过对鼠尾进行剥离获得鼠尾腱,用Tris-HCl缓冲液、胃蛋白酶处理获得鼠尾胶原蛋白原液、反复使用氯化钠溶液进行分级盐析、醋酸溶液复溶进行鼠尾胶原蛋白的纯化。超纯水透析除去无机盐类获得纯化的鼠尾胶原蛋白。通过SDS-PAGE蛋白质电泳、氨基酸含量分析等技术手段鉴定。结果本研究建立的方法可以获得高纯度的鼠尾胶原蛋白,纯度达到电泳纯。与国外进口的商业化鼠尾胶原蛋白产品相比无差异。研究了提取、分离、纯化参数对得率、纯度的影响,建立了最优的鼠尾胶原蛋白提取条件,胃蛋白酶用量：1∶500,酶解时间：72 h,盐析浓度：2 mol/L,提取所用酸溶液：0.05mol/L醋酸溶液。结论为鼠尾胶原蛋白的扩大化生产提供了合适的工艺参数,为大量获得鼠尾胶原蛋白并进行更深层次的功效方面研究提供了理论支持和实践基础。     

Gnathostome vertebrae and the classification of the Amphibia

Four pairs of arcualia were primitively present in each segment of gnathostomes. The individual vertebral ossifications of early temnospondyls are most economically interpreted as the endochondral ossifications of these cartilaginous arcualia. Centra have formed independently on at least two occasions within the tetrapods and arcualia play little or no part in the formation of true centra in any living form. The so called pleuro- and intercentra of the temnospondyls can in no way be homologized with the centra of either lissamphibians or amniotes. The Nectridea are considered to be the sister group of the Lissamphibia and the Aistopoda the sister group of these two. The anthracosaurs, seymourians and microsaurs are regarded as amniotes. There is no evidence for resegmentation in the vertebral column.     

Crocodylian Tracks from Lower Oligocene Flysch deposits of the Barail Group,Manipur, India

A marine tidal delta siltstone from Gelmon locality in Northeast India preserved three crocodylian footprints and an elongate depression that appears to be a tail drag mark. Similar drag marks occur in nearby bedding surfaces. The discovery of crocodylian tracks from the basal part of Laisong Formation, Barail Group (Late Eocene–Early Oligocene age) of Manipur, India is noteworthy because of the age and the geographic location. Crocodylian tracks are rare in Cenozoic formations and they have not previously been reported from Asia. The footprints are herein named as a new ichnogenus and ichnospecies, Indosuchipes manipurensis.     

Bacteriophage T4 baseplate components. III. Location and properties of the bacteriophage structural thymidylate synthetase.

Two T4D thymidylate synthetase (td) temperature-sensitive mutants have been isolated and characterized. Both mutants produce heat-labile phage particles. This observation supports the view that this viral-induced protein is a phage structural component. Further, antiserum to td has been shown to block a specific step in tail plate morphogenesis. The results indicated that the td protein is largely covered by the T4D tail plate gene 11 protein. Since the phageinduced dihydrofolate reductase (dfr) also is partially covered by the gene 11 protein, it appears that td was adjacent to the tail plate dfr. This location has been confirmed by constructing a T4D mutant which is dfrtstdts and showing that these two tail plate constituents interact and give altered physical properties to the phage particles produced. A structural relationship for the tail plate folate, dfr, and td has been reported.     

Unique mid‐tract loss of a primary remex in male broadbills of the Southeast Asian genus Calyptomena: timing and possible implications

Female Calyptomena broadbills have 10 large primaries, whereas adult males have nine. At or before the main post‐juvenile moult, males abort what appears to be juvenile P5. This creation of row space is accompanied by a shortening of the wing tip, a development (together with tail shortening) that, as in some Neotropical suboscines, may relate to performance of exaggerated displays. Calyptomena has been linked taxonomically with Afrotropical Smithornis, the one genus of broadbills with proven display‐related modification of flight‐feathers.     

Adaptive problems and possibilities in the temporal fenestration of tetrapod skulls

Adaptive explanations for the temporal fenestration in reptiles are briefly reviewed. With few possible exceptions, fenestrate appeared first in the reptiles, and have seemingly evolved independently in several different phyletic lines. The several explanations for fenestration offered by previous authors include speculations that open spaces in the skull permitted bulging of the jaw-closing muscles, and that fenestrae formed in areas of reduced stress where the presence of bone would be functionally useless. The first of these does not readily apply to initial evolutionary stages; the second is more satisfactory. Certain features of muscular attachments to bones are dealt with, and their implications applied to the fenestration problem to add another possible explanation (which need not contradict previously published suggestions). Considerations of cranial strength in tetrapod skulls led to speculations on the lack of fenestration in temnospondyls, anthracosaurs, microsaurs and cotylosaurs. Emargination of the skull roof in turtles is also discussed.     

Influence of Social Factors on Seasonal Variations in Plasma Testosterone Levels of Microcebus murinus

Blue tail coloration in hatchling skinks (Eumeces fasciatus and E. laticeps) appears to be an antipredatory adaptation that distracts attention away from the body to the tail. The tail itself serves as a decoy that may be autotomized as a final defense against capture. The effectiveness of intact tails in deflecting attacks from the body was 50% against scarlet kingsnakes in the experimental conditions used. Brightness rather than hue presumably accounts for the higher attack frequency on blue than black tails in this study, but the blue color may have evolved in response to avian predation. Repeated predation without ill effects by several predators allows rejection of the hypothesis that the blue tail is aposematic for the predators tested. The hypothesis that blue tails provide stimuli inhibiting aggression or predation by adult male conspecifics is untenable for E. laticeps because adult males readily eat intact hatchlings. Although this study provides no statistical evidence that blue tail coloration inhibits attack by female E. laticeps on hatchlings, the trend of predation rates on blue- and black-tailed hatchlings is in the direction predicted for inhibition.     

Structural studies on the second Mycobacterium smegmatis Dps: invariant and variable features of structure, assembly and function

A second DNA binding protein from stationary-phase cells of Mycobacterium smegmatis (MsDps2) has been identified from the bacterial genome. It was cloned, expressed and characterised and its crystal structure was determined. The core dodecameric structure of MsDps2 is the same as that of the Dps from the organism described earlier (MsDps1). However, MsDps2 possesses a long N-terminal tail instead of the C-terminal tail in MsDps1. This tail appears to be involved in DNA binding. It is also intimately involved in stabilizing the dodecamer. Partly on account of this factor, MsDps2 assembles straightway into the dodecamer, while MsDps1 does so on incubation after going through an intermediate trimeric stage. The ferroxidation centre is similar in the two proteins, while the pores leading to it exhibit some difference. The mode of sequestration of DNA in the crystalline array of molecules, as evidenced by the crystal structures, appears to be different in MsDps1 and MsDps2, highlighting the variability in the mode of Dps-DNA complexation. A sequence search led to the identification of 300 Dps molecules in bacteria with known genome sequences. Fifty bacteria contain two or more types of Dps molecules each, while 195 contain only one type. Some bacteria, notably some pathogenic ones, do not contain Dps. A sequence signature for Dps could also be derived from the analysis.     

Genetic map of the Staphylococcal bacteriophage phi11.

Ten sus mutants of the staphylococcal bacteriophage phi 11, each a representative from a different complementation group, have been used in three-factor cross experiments. The results of these crosses indicate a circular genetic map for phi 11. Functional studies of the mutants have been limited to electron microscopic examinations of lysates after prophage induction (or infection). One gene is an early gene, five genes are concerned with tail formation, and three are concerned with head formation. The tenth gene is possibly a head gene. The contribution by phi 11 to the genomic content of the plasmid-phage hybrid phi 11 de has been investigated. Phi 11 de contains most of the late genes and appears to be missing a continuous phi 11 segment that includes the early gene flanked by two late genes.     

Thy-1: a lymphoid cell subset marker capable of delivering an activation signal to mouse T lymphocytes

Monoclonal anti-Thy-1 antibodies are capable of activating mouse T cells in the absence of an antigen-specific signal. Therefore, Thy-1 appears to be connected to an alternative signal transduction pathway, operative in thymocytes as well as in neuronal cells, since this molecule is also present on brain. Biochemical data have shown that this molecule is differentially glycosylated with respect to its cellular distribution. Structure and sequence comparisons revealed a strong homology with the immunoglobulin primordial domain. In addition, the Thy-1 glycoprotein has the particularity of being anchored to the membrane via a glycophospholipid tail. Gene transfer experiments in different cell types have been performed to analyze the mechanism of the Thy-1 pathway of activation.     

Mitotic Phosphorylation of Histone H3: Spatio-Temporal Regulation by Mammalian Aurora Kinases

Phosphorylation at a highly conserved serine residue (Ser-10) in the histone H3 tail is considered to be a crucial event for the onset of mitosis. This modification appears early in the G(2) phase within pericentromeric heterochromatin and spreads in an ordered fashion coincident with mitotic chromosome condensation. Mutation of Ser-10 is essential in Tetrahymena, since it results in abnormal chromosome segregation and extensive chromosome loss during mitosis and meiosis, establishing a strong link between signaling and chromosome dynamics. Although mitotic H3 phosphorylation has been long recognized, the transduction routes and the identity of the protein kinases involved have been elusive. Here we show that the expression of Aurora-A and Aurora-B, two kinases of the Aurora/AIK family, is tightly coordinated with H3 phosphorylation during the G(2)/M transition. During the G(2) phase, the Aurora-A kinase is coexpressed while the Aurora-B kinase colocalizes with phosphorylated histone H3. At prophase and metaphase, Aurora-A is highly localized in the centrosomic region and in the spindle poles while Aurora-B is present in the centromeric region concurrent with H3 phosphorylation, to then translocate by cytokinesis to the midbody region. Both Aurora-A and Aurora-B proteins physically interact with the H3 tail and efficiently phosphorylate Ser10 both in vitro and in vivo, even if Aurora-A appears to be a better H3 kinase than Aurora-B. Since Aurora-A and Aurora-B are known to be overexpressed in a variety of human cancers, our findings provide an attractive link between cell transformation, chromatin modifications and a specific kinase system.