Phylogeny of gas exchange systems

Several systems of gas transport have developed during evolution, all of which are able to sufficiently supply oxygen to the tissues and eliminate the CO2 produced by the metabolism, in spite of great distances between the environment and the individual cells of the tissues. Almost all these systems utilize a combination of convection and diffusion steps. Convection achieves an efficient transport of gas over large distances, but requires energy and cannot occur across tissue barriers. Diffusion, on the other hand, achieves gas transport across barriers, but requires optimization of diffusion paths and diffusion areas. When two convectional gas flows are linked via a diffusional barrier (gas/fluid in the case of the avian lung, fluid/fluid in the case of gills), the directions in which the respective convectional movements pass each other are important determinants of gas exchange efficiency (concurrent, countercurrent and cross-current systems). The tracheal respiration found in insects has the advantage of circumventing the convective gas transport step in the blood, thereby avoiding the high energy expenditure of circulatory systems. This is made possible by a system of tracheae, ending in tracheoles, that reaches from the body surface to every cell within the body. The last step of gas transfer in these animals occurs by diffusion from the tracheoles ("air capillaries") to the mitochondria of cells. The disadvantage is that the tracheal system occupies a substantial fraction of body volume and that, due to limited mechanical stability of tracheal walls, this system would not be able to operate under conditions of high hydrostatic pressures, i. e. in large animals. Respiration in an "open" system, i. e. direct exposure of the diffusional barrier to the environmental air, eliminates the problem of bringing the oxygen to the barrier by convection, as is necessary in the avian and mammalian lung, in the insects' tracheal system and in the gills. An open system is found in the respiration via the skin, which is of significance in some amphibians, but is limited by the thickness of the skin that constitutes a substantial diffusion path for O2 and CO2. The thick skin, on the other hand, provides mechanical protection as well as flexibility for the animals' body and helps avoid massive water loss via the body surface. The gills of fishes, in contrast, exhibit rather short diffusion distances, are located in a mechanically protected space, and the problem of water loss does not exist. The flows of blood and water occur in opposite direction (countercurrent flow) and this situation makes an arterial PO2 approaching the environmental PO2 possible. A major disadvantage is constituted by the environmental medium since water contains little O2 compared to air and, to compensate this, much energy is expended to maintain a high flow rate of water through the gills. In the mammalian lung ("pool system"), the presence of a dead space and the rhythmic ventilation that replaces only a small fraction of the gas volume of the lung per breath, are responsible for an arterial PO2 (2/3 of the atmospheric PO2) that cannot reach the expiratory PO2. However, an advantage of this feature is the constantly high alveolar and arterial PCO2, which provides a highly effective H(+) buffer system in the entire body. The apparent disadvantage of the mammalian lung is avoided by the avian lung, which uses an extended system of airways to establish continuous equilibration of a part of the capillary blood with fresh air (cross current system), during inspiration as well as during expiration. In this system, arterial PO2 can significantly exceed expiratory PO2. A disadvantage here is the enormous amount of space taken up by the avian lung, in animals of 1 kg body weight three times as much as taken up by the mammalian lung. All respiratory exchange systems considered here exhibit high degrees of optimization - yet follow highly diverse construction principles. There is no such thing as an ideal gas exchange system. The system that has evolved in each species depends to an impressive extent on environmental conditions, on body build and size, on the animal's patterns of movement and on its energy consumption.     

Phylogeny and evolution of hormone systems

Classically hormones are defined as molecules that are secreted by endocrine glandular or neurosecretory cells into the blood stream and transported to their target tissue where they induce physiological processes at very low concentrations. Studies on the potential origin and the evolution of cell-to-cell communication systems suggest that exocrine pheromones (food signals and toxins) might have been the primitive bioregulatory molecules of unicellular organisms for chemical communication with each other and with the biosphere. The broad distribution and the structural diversity of pheromones suggests that these molecules and their receptors were predecessor modules of cell communication systems in metazoa. Neurosecretory cells, as we find them in Cnidarians, possibly served as basic modules for the evolution of neurohormonal systems of higher animals. Studies on genetic model organisms, such as Drosophila or the mouse, have demonstrated that chemical communication between neighbouring or more distant cells does not just involve endocrine and neurosecretory cells, but also unexpectedly tissues and organs such as the heart or the adipose tissue (e. g. the leptin signalling pathway). Comparative endocrinology could show that molecular components of hormonal systems represent signalling networks that are generally used during cellular communication processes and the differentiation of cell types during ontogenesis. Some of their functions are evolutionarily conserved, others not, as disscussion on steroid hormones and the prolactin signalling pathway will demonstrate.     

Phylogeny and taxonomy of the Inonotus linteus complex

The Inonotus linteus complex comprises several closely related species characterized by pileate basidiomes, a heterogeneous hyphal system with a monomitic context and a dimitic hymenophoral trama. Setae are hymenial and basidiospores are broadly ellipsoid to subglobose, yellowish and thick-walled. Research to understand this complex have been particularly noticeable in East Asia. In the present paper, the complex was studied at a larger scale, including samples from Mesoamerica. Inonotus linteus, an epitype of this species being designated here, is circumscribed as a narrow sense based on morphological and phylogenetic data, and this has lead to delimiting a new species from Mesoamerica, viz. I. cubensis, and provides evidence for two additional species, I. alpinus and I. zonatus, from East Asia. Phylogenetic analyses of ITS sequences also confirmed the status of I. baumii, I. linteus, I. lonicericola, I. lonicerinus, I. vaninii, I. sanghuang, I. weigelae and I. weirianus as distinct taxa, while I. tenuicontextus is considered to be a synonym of I. weigelae. A key to 11 species in the complex is provided.     

Expression of Mammalian P1 Protamine Gene

Expression of Mammalian P1 Protamine Gene     

Mammalian response to subdermal implantation of textured microimplants

The development of small, textured implant particles suspended in a hydrogel has allowed for subdermal injection therapy to fill tissue defects. The microimplant particles were placed subdermally into the ears of white New Zealand rabbits in order to characterize the foreign body response and the permanence of the implant. Serial micrometer readings were performed on the implant sites to determine any change in thickness of the augmentation following baseline measurement. An initial increase in the thickness was noted approximately 20–30 days postimplantation, as expected. A stable thickness was noted for the remainder of the experiment. Serial histological sections were performed at irregular intervals from one week to one year. Histology demonstrated a mild foreign body response with collagen surrounding each individual microimplant particle. The response was stable after 30–40 days and has remained stable for over one year. It was determined that the histology demonstrated a Boros IA type, or nonimmunogenic, low-turnover foreign body reaction.     

Comparative analysis of layer-specific genes in Mammalian neocortex

We examined the expression patterns of 4 layer-specific genes in monkey and mouse cortices by fluorescence double in situ hybridization. Based on their coexpression profiles, we were able to distinguish several subpopulations of deep layer neurons. One group was characterized by the expression of ER81 and the lack of Nurr1 mRNAs and mainly localized to layer 5. In monkeys, this neuronal group was further subdivided by 5-HT2C receptor mRNA expression. The 5-HT2C(+)/ER81(+) neurons were located in layer 5B in most cortical areas, but they intruded layer 6 in the primary visual area (V1). Another group of neurons, in monkey layer 6, was characterized by Nurr1 mRNA expression and was further subdivided as Nurr1(+)/connective tissue growth factor (CTGF)(-) and Nurr1(+)/CTGF(+) neurons in layers 6A and 6B, respectively. The Nurr1(+)/CTGF(+) neurons coexpressed ER81 mRNA in monkeys but not in mice. On the basis of tracer injections in 3 monkeys, we found that the Nurr1(+) neurons in layer 6A send some corticocortical, but not corticopulvinar, projections. Although the Nurr1(+)/CTGF(-) neurons were restricted to lateral regions in the mouse cortex, they were present throughout the monkey cortex. Thus, an architectonic heterogeneity across areas and species was revealed for the neuronal subpopulations with distinct gene expression profiles.     

Sex Determination and Differentiation of the Mammalian Gonad

There is growing evidence to suggest that the presence of a single gene on the Y chromosome, which also codes for the expression of the H-Y antigen, causes the primordial gonad to develop structurally as a testis: in the absence of this gene, an ovary is formed. Whether the gonad subsequently becomes capable of producing viable gametes depends on the sex chromosome makeup of the germ cells that migrate into it; XY or XO germ cells seem to be capable of developing into either oocytes or spermatocytes, depending on the environment, whereas germ cells with two X chromosomes can only develop as oocytes, and will not survive in a testicular environment. The H-Y antigen probably plays no role in the sexual differentiation of the germ cell.
There is another gene on the Y chromosome that determines testis size, and testes: body weight ratios vary widely in different mammals. Amongst the higher primates the gorilla has the lowest ratio (0.018%), man is intermediate (0.079%) and the chimpanzes have the highest (0.269%). Testis size is predominantly determined by the amount of tubular tissue, and appears to be closely related to copulatory frequency, and hence to the mating behaviour of the species. It is important to take these marked species differences in testis size into account when using primate models for human male contraceptive research and development.     

Inhibition of Mammalian Gq Protein Function by Local Anesthetics

Background: Local anesthetics have been shown to selectively inhibit functioning of Xenopus laevis Gq proteins. It is not known whether a similar interaction exists with mammalian G proteins. The goal of this study was to determine whether mammalian Gq protein is inhibited by local anesthetics.

Methods: In Xenopus oocytes, the authors replaced endogenous Gq protein with mouse Gq (expressed in Sf9 cells using baculovirus vectors). Cells endogenously expressing lysophosphatidic acid or recombinantly expressing muscarinic m3 receptors were injected with phosphorothioate DNA antisense (or sense as control) oligonucleotides against Xenopus Gq. Forty-eight hours later, oocytes were injected with purified mouse Gq (5 x 10-8 m) or solvent as control. Two hours later, the authors injected either lidocaine, its permanently charged analog QX314 (at IC50, 50 nl), or solvent (KCl 150 mm) as control and measured Ca-activated Cl currents in response to lysophosphatidic acid or methylcholine (one tenth of EC50).

Results: Injection of anti-Gq reduced the mean response size elicited by lysophosphatidic acid to 33 +/- 7% of the corresponding control response. In contrast, responses were unchanged (131 +/- 29% of control) in cells in addition injected with mouse Gq protein. Injection of mouse Gq protein "rescued" the inhibitory effect of intracellularly injected QX314: whereas QX314 was without effect on Gq-depleted oocytes, responses to lysophosphatidic acid after QX314 injection were inhibited to 44 +/- 10% of control response in cells in addition injected with mouse Gq protein (5 x 10-8 m). Similar results were obtained for m3 signaling and intracellularly injected lidocaine.     

Phylogeny,taxonomy and diversification events in the Caliciaceae

Although the high degree of non-monophyly and parallel evolution has long been acknowledged within the mazaediate Caliciaceae (Lecanoromycetes, Ascomycota), a natural re-classification of the group has not yet been accomplished. Here we constructed a multigene phylogeny of the Caliciaceae-Physciaceae clade in order to resolve the detailed relationships within the group, to propose a revised classification, and to perform a dating study. The few characters present in the available fossil and the complex character evolution of the group affects the interpretation of morphological traits and thus influences the assignment of the fossil to specific nodes in the phylogeny, when divergence time analyses are carried out. Alternative fossil assignments resulted in very different time estimates and the comparison with the analysis based on a secondary calibration demonstrates that the most likely placement of the fossil is close to a terminal node rather than a basal placement in the Calicium clade. Our dating analysis show two successive events giving rise to main clades of mazaediate taxa within the Caliciaceae, in the Upper-Lower Cretaceous boundary and in the Paleocene. As a result of this study, Cyphelium is synonymized with Calicium, Acolium is resurrected, and the new genera Allocalicium and Pseudothelomma are described. Twelve new combinations are proposed: Acolium karelicum, Acolium marcianum, Allocalicium adaequatum, Calicium carolinianum, Calicium lecideinum, Calicium lucidum, Calicium notarisii, Calicium pinicola, Calicium trachyliodes, Pseudothelomma occidentale, Pseudothelomma ocellatum and Thelomma brunneum. A key for the mazaedium-producing Caliciaceae is included.     

哺乳动物睾丸细胞株的建立及应用

哺乳动物生精过程是一个精细的调节过程 ,人们对于这个过程还了解甚少。这主要是由于维持生殖细胞体外培养的必需条件尚未建立 ,睾丸生精细胞可原代培养的时间太短。因此 ,有必要建立能在体外长期传代的睾丸生精细胞株。Hofmann等人用磷酸钙法将猴病毒 40大T抗原 (sv40lt)基因掺入小鼠睾丸细胞建立了永生的睾丸细胞株 ,并利用这些细胞株研究了睾丸特异基因的表达。随后 ,又通过对小鼠睾丸生精细胞共转染sv40lt基因和编码温度敏感p5 3蛋白基因 ,建立了两个能在体外继续分化的生精细胞株。这些睾丸细胞株的建立为精子发生研究提供了一个有用的实验模型。     

Phylogeny of the industrial relevant, thermophilic genera Myceliophthora and Corynascus

Species of the genus Myceliophthora and its teleomorph Corynascus have attracted increasing interest due to their potential to produce thermostable enzymes. This study re-assessed the phylogenetic relationship of 49 isolates of nine species belonging to Myceliophthora and Corynascus. One species, M. vellerea, was shown not to belong to the genus Myceliophthora and should be placed in the genus Ctenomyces. The other species belonged to two phylogenetic clusters: mesophilic fungi with the type species M. lutea and C. sepedonium, and thermophilic fungi with M. thermophila, M. hinnulea and C. thermophilus. The phylogenetic data provides no clear separation of the two genera Corynascus and Myceliophthora. To avoid confusion in future taxonomic studies, it is proposed that all existing Corynascus species be renamed to Myceliophthora, which is the old name and the one more frequently used. Furthermore, this study identified two groups within the isolates listed as M. thermophila and assigned one group (five isolates) to M. heterothallica based on AFLP analysis and mating behavior. This study provides new insights into the genetic differences within the genus Myceliophthora and will therefore be essential for the interpretation of future genomic and physiological studies of these species.