The cytoskeletal proteins in the contractile tissues of the testis and its excurrent ducts of the passerine bird, Masked Weaver (Ploceus velatus)

The cellular composition of the testicular capsule, seminiferous peritubular tissue, the epithelia as well as periductal muscle cell layers of the excurrent ducts was studied, in sexually mature and active Masked Weaver (Ploceus velatus) birds of the passerine family, Ploceidae. Ultrastructure of the contractile cells in the testicular capsule, peritubular and periductal tissues showed that these cells were smooth muscles of typical morphological characteristics. Variability in the immunohistochemical co-expression of microfilaments and intermediate filaments in the different tissues was evident. Actin and desmin proteins were co-expressed immunohistochemically in the testicular capsule and seminiferous peritubular smooth muscle layer. Actin was singly and very weakly expressed in the rete testis epithelium while cytokeratins and desmin were co-expressed in the epithelium of the excurrent ducts. The periductal muscle layer of all ducts of the epididymis, the ductus deferens as well as the seminal glomus, strongly co-expressed actin and desmin. Vimentin was absent in all cells and tissue types studied. There is clear evidence that the tissues of the male gonad and its excurrent ducts in the Masked Weaver, as has been reported for members of the Galloanserae and Ratitae, contain well-formed contractile tissues whose function would include the transportation of luminal through-flow from the testis into, and through, its excurrent ducts. The microtubule helix in the head and of the mid-piece, of elongating spermatids, as well as of the mature spermatozoa in the various excurrent ducts, including some spermatozoa in the seminal glomus, also co-expressed these three proteins.     

Photoperiodic regulation of seasonal responses in Indian weaver bird (Ploceus philippinus)

Photoperiod (=day length) is the vital factor for the regulation of behavioral and physiological activities in many avian species. This study investigated the seasonal cycles of testicular growth and secondary sexual characteristics of Indian weaver bird under natural day length (NDL) and the effects of duration and intensity of light on photoperiodic induction. In the first experiment, groups of birds (n = 7 each) were exposed to under NDL in April 2008 and May 2009 for 8 and 12 months, respectively. In second and third experiment, birds (n = 6 each group) were exposed to different photoperiods (11.5L:12.5D, 12L:12D, 13L:11D, and 15L:9D) at the same (500 lux) light intensity, and to 13L:11D at different light intensities (10-, 50-, 500-, and 800-lux). Observations on testis size, molt, and plumage score were recorded 2-week (molt and plumage) or at 4-week intervals (testes). Both the NDL groups showed similar seasonal cycles of testicular growth-regression and secondary sexual characteristics. Second and third experiments suggest that the photoperiodic induction was depending upon duration and intensity of the light. Birds showed testicular growth-regression cycle followed by molt and plumage color change only under 13L:11D and 15L:9D and only 500- and 800-lux under 13L:11D photoperiod but not under 11.5L:12.5D and 12L:12D and 10- and 50-lux light intensities. Pre- and post-nuptial molting on body feathers were progressed with gonadal stimulation–maturation and regression cycle under 13L:11D and 15L:9D. Results under different light–dark cycles suggest that day length of about 12 h or more and above the threshold level of light intensity are essential for the induction of photoperiodic responses.     

Acrosome formation and the centriolar complex in the spermatozoa of Sabella penicillum (Polychaeta)

Summary The acrosomal vesicle of Sabella penicillum spermatids consists of an electrondense core and a more transparent surrounding zone. During subsequent differentiation the vesicle membrane forms several invaginations in the juxtanuclear area. These invaginations later establish contact with the core. In the mature spermatozoon the spaces between the invaginations appear as electron-dense tubules; this is probably due to a shift of material from core to periphery. The ultrastructure of the centriolar complex is described in detail.Work supported by the Norwegian Research Council for Science and Humanities (NAVF; Grant Nr. D 61.44) and The Austrian Fonds zur Förderung der wissenschaftlichen Forschung Projekt 2183 and N 39.     

The progression of the intra-erythrocytic cell cycle of Plasmodium falciparum and the role of the centriolar plaques in asynchronous mitotic division during schizogony

The cell division cycle and mitosis of intra-erythrocytic (IE) Plasmodium falciparum are poorly understood aspects of parasite development which affect malaria molecular pathogenesis. Specifically, the timing of the multiple gap (G), DNA synthesis (S) and chromosome separation (M) phases of parasite mitosis are not well defined, nor whether genome divisions are immediately followed by cleavage of the nuclear envelope. Curiously, daughter merozoite numbers do not follow the geometric expansion expected from equal numbers of binary divisions, an outcome difficult to explain using the standard model of cell cycle regulation. Using controlled synchronisation techniques, confocal microscopy to visualise key organelles and fluorescence in situ hybridization (FISH) to follow the movements and replication of genes and telomeres, we have re-analysed the timing and progression of mitotic events. The asynchronous duplications of the P. falciparum centrosome equivalents, the centriolar plaques, are established and these are correlated with chromosome and nuclear divisions in a new model of P. falciparum schizogony. Our results improve the resolution of the cell cycle and its phases during P. falciparum IE development, showing that asynchronous, independent nuclear division occurs during schizogony, with the centriolar plaques playing a major role in regulating mitotic progression.     

Major histocompatibility complex variation and mate choice in a lekking bird, the great snipe (Gallinago media)

Genes of the major histocompatibility complex (MHC) play a major part in the activation of the vertebrate immune system. In addition, they also appear to function as cues for mate choice. In mammals especially, several kinds of MHC-dependent mate choice have been hypothesized and observed. These include choice of mates that share no or few alleles with the choosing individual, choice of mates with alleles that differ as much as possible from the choosing individual, choice of heterozygous mates, choice of certain genotypes and choice of rare alleles. We investigated these different aspects of mate choice in relation to MHC in a lekking bird species, the great snipe (Gallinago media). We found no evidence for MHC disassortative mating, no preference for males with many MHC alleles and no preference for rare alleles. However, we did find that some allelic lineages were more often found in males with mating success than in males without mating success. Females do not seem to use themselves as references for the MHC-dependent mate choice, rather they seem to prefer males with certain allele types. We speculate that these alleles may be linked to resistance to common parasites.     

Duplicated growth hormone genes in a passerine bird, the jungle crow (Corvus macrorhynchos)

Molecular cloning, molecular phylogeny, gene structure and expression analyses of growth hormone (GH) were performed in a passerine bird, the jungle crow (Corvus macrorhynchos). Unexpectedly, duplicated GH cDNA and genes were identified and designated as GH1A and GH1B. In silico analyses identified the zebra finch orthologs. Both GH genes encode 217 amino acid residues and consist of five exons and four introns, spanning 5.2 kbp in GH1A and 4.2 kbp in GH1B. Predicted GH proteins of the jungle crow and zebra finch contain four conserved cysteine residues, suggesting duplicated GH genes are functional. Molecular phylogenetic analysis revealed that duplication of GH genes occur after divergence of the passerine lineage from the other avian orders as has been suggested from partial genomic DNA sequences of passerine GH genes. RT-PCR analyses confirmed expression of GH1A and GH1B in the pituitary gland. In addition, GH1A gene is expressed in all the tissues examined. However, expression of GH1B is confined to several brain areas and blood cells. These results indicate that the regulatory mechanisms of duplicated GH genes are different and that duplicated GH genes exert both endocrine and autocrine/paracrine functions.     

Fine structure of spermatozoa in the blackspot sea bream Pagellus bogaraveo (Brünnich, 1768) with some considerations about the centriolar complex

Scanning and transmission electron microscopy were used to investigate the fine structure of the sperm of the sparid fish Pagellus bogaraveo.The spermatozoon of P. bogaraveo belongs, like that of the other sparid fish, to the teleostean “type I” spermatozoon with the flagellar axis insert perpendicular to the nuclear fossa. It has an ovoidal head, a short, cylindrically shaped midpiece and a long tail region. The nucleus reveals a deep invagination (nuclear fossa), in which the centriolar complex is located, and a satellite nuclear notch shaped like a golf club. The two centrioles are perpendicular to each other and show a conventional “9+0” pattern. The distal centriole is attached to the nuclear envelope by means of basal feet and radial fibers made of electron-dense material. Below the basal plate, plasma membrane pinches in, and the necklace, a specialized connection joining axonemal doublets to the plasma membrane, is visible. The short midpiece houses one mitochondrion. The flagellum is perpendicularly and eccentrically with respect to the nucleus and contains the conventional “9+2” axoneme.     

Evidence for a circadian oscillation in the gonadal response of the tropical weaver bird (Ploceus philippinus) to programmed photoperiod.

The effect of an asymmetrical skeleton photoperiod scheduleee was studied on the gonadal development in a tropical finch, the weaver bird (Ploceus philippinus). The schedul comprised a short nonstimulatory primary photoperiod of 6 hrs and a secondary much shorter lightperiod given as a 15-min light pulse at different times in the dark period. The light pulse 11 hrs after the basic period resulted in gonadal stimulation, while light pulse in contimuation with the basic period or 8, 14 or 21 hrs after the basicperiod was not stimulatory. The "photoinducible phase" was much more precisely outlined by shifting the birds from an 8-h to a 10-h pulse, and from an 11-h to 12-h pulse and was found to be very short, lasting about an hour falling between 11 and 12 hrs after the primary light period. The short photoinducible phase may be of an adaptive value since in the tropics the difference between the shortest and the longest daylength is also rather small (3 hrs and 15 min at Varanasi, 25degrees N). Clearly the weaver bird possesses a fine time-measuring device involving an endogenous circadian rhythm in photosensitivity. In nature, spermatogenesis in this bird also begins in March when the daylength exceeds 11 hrs (thus perhaps coinciding with the photoinducible phase). In rather small, photoperiod may not serve as a cue to trigger seasonal reproductive periodicity, it seems that photoperiod can act as a Zeitgeber for the initiation of spermatogenesis in the weaver bird at least.     

The origin of bird pollination in Macaronesian Lotus (Loteae, Leguminosae)

The four red-flowered, apparently bird-pollinated Lotus species from the Canary Islands have previously been classified in their own genus, Rhyncholotus. Currently, they are considered as a separate section within genus Lotus, distinct from other herbaceous Canarian congeners which are yellow-flowered and bee-pollinated. A combined analysis of four nuclear regions (including ITS and three homologues of CYCLOIDEA) and three plastid regions (CYB6, matK and trnH-psbA) nests the four bird-pollinated species within a single extant species of bee-pollinated Lotus (L. sessilifolius), in a very extreme example of species paraphyly. Therefore, our data compellingly support the hypothesis that the Macaronesian Lotus species with a bird pollination syndrome are recently derived from entomophilous ancestors. Calibration of the phylogenetic trees using geological age estimates of the most recent islands (La Palma and El Hierro) together with oldest ages of Fuerteventura indicates that bird pollination evolved ca. 1.7 Ma in the Canarian Lotus. These four bird-pollinated species share a most recent common ancestor (MRCA) with L. sessilifolius that dates to about 2.2 Ma. Our analyses further suggest that the evolution of the bird pollination syndrome was likely triggered by the availability of new niches in La Palma and Tenerife as a result of recent volcanic activity.     

Metalloprobes: synthesis, characterization, and potency of a novel gallium(III) complex in human epidermal carcinoma cells

Multidrug resistance (MDR) mediated by overexpression of the MDR1 gene product, P-glycoprotein (Pgp), represents one of the best characterized barriers to chemotherapeutic treatment in cancer and may be a pivotal factor in progression of Alzheimer's disease (AD). Thus, agents capable of probing Pgp-mediated transport could be beneficial in biomedical imaging. Herein, we synthesized and structurally characterized a gallium(III) complex (5) of the naphthol-Schiff base ligand. The crystal structure revealed octahedral geometry for the metallodrug. Cytotoxicity profiles of 5 were evaluated in KB-3-1 (Pgp-) and KB-8-5 (Pgp+) human epidermal carcinoma cell lines. Compared with an LC(50) (the half-maximal cytotoxic concentration) value of 1.93 microM in drug-sensitive (Pgp-) cells, the gallium(III) complex 5 demonstrated an LC(50) value>100 microM in drug-resistant (Pgp+) cells, thus indicating that 5 was recognized by the Pgp as its substrate, thereby extruded from the cells and sequestered away from their cytotoxic targets. Radiolabeled analogues of 5 could be beneficial in noninvasive imaging of Pgp-mediated transport in vivo.     

Role of melatonin in photoperiodic time measurement in the migratory redheaded bunting (Emberiza bruniceps) and the nonmigratory Indian weaver bird (Ploceus philippinus)

In the present study, we asked the question whether physiological responses to day length of migratory redheaded bunting (Emberiza bruniceps) and nonmigratory Indian weaver bird (Ploceus philippinus) are mediated by the daily rhythm of melatonin. Melatonin was given either by injection at certain times of the day or as an implant. In series I experiments on the redheaded bunting, melatonin was administered by subcutaneous injections daily at zeitgeber time (ZT) 4 (morning) or ZT10 (evening) and by silastic capsules in photosensitive unstimulated buntings that were held in natural day lengths (NDL) at 27 degrees N beginning from mid February, and in artificial day lengths (ADL, 12L:12D and 14L:10D). Melatonin did not affect the photoperiod-induced cycles of gain and loss in body mass and testicular growth-involution, but there was an effect on temporal phasing of the growth-involution cycle of testes in some groups. For example, the rate of testicular growth and development was faster in birds that received melatonin injection at ZT4 in NDL, and was slower in birds that carried melatonin implants both in NDL and ADL. In series II experiments on Indian weaver birds, melatonin was given in silastic capsules in the first week of September when they still had large gonads. Birds were exposed for 12 weeks to short day length (8L:16D; group 1), to long day length (eight weeks of 16L:8D and four weeks of 18L:6D; group 2), or to both short and long day lengths (four weeks each of 8L:16D, 16L:8D, and 18L:6D; groups 3 and 4). Whereas groups 1 to 3 carried melatonin or empty implant from the beginning, group 4 received one after four weeks. All birds underwent testicular regression during the first four weeks irrespective of the photoperiod they were exposed to or the implant they carried in, and there was a slight re-initiation of testis growth in some birds during the next eight weeks of long day lengths. However, with the exception of group 2, there was no difference in mean testis volume during the period of experiment between the melatonin- and empty-implant birds. The data on androgen-dependent beak color also supported the observations on testes. Together, these results do not support the idea that the daily rhythm of melatonin is involved in the photoperiodic time measurement in birds. However, there may still be a role of melatonin in temporal phasing of the annual reproductive cycle in birds.     

The Swi/Snf chromatin remodeling complex is essential for hyphal development in Candida albicans

The ability of dimorphic transition between yeast and hyphal forms in Candida albicans is one of the vital determinants for its pathogenicity and virulence. We isolated C. albicans SWI1 as a suppressor of the invasive growth defect in a Saccharomyces cerevisiae mutant. Expression of C. albicans SWI1 in S. cerevisiae partially complemented the growth defect of a swi1 mutant in the utilization of glycerol. Swi1 is in a complex with Snf2 in C. albicans, and both proteins are localized in the nucleus independent of the growth form. Deleting SWI1 or SNF2 in C. albicans prevented true hyphal formation and resulted in constitutive pseudohypha-like growth in all media examined. Furthermore, swi1/swi1 mutant was defective in hypha-specific gene expression and avirulent in a mouse model of systemic infection. These data strongly suggest the conserved Swi/Snf complex in C. albicans is required for hyphal development and pathogenicity.     

Life history,sexual dimorphism and ‘ornamental’ feathers in the mesozoic bird Confuciusornis sanctus

The life history of Confuciusornis sanctus is controversial. Recently, the species’ body size spectrum was claimed to contradict osteohistological evidence for a rapid, bird-like development. Moreover, sexual size dimorphism was rejected as an explanation for the observed bimodal size distribution since the presence of elongated rectrices, an assumed ‘male’ trait, was uncorrelated with size. However, this interpretation (i) fails to explain the size spectrum of C. sanctus which is trimodal rather than bimodal, (ii) requires implausible neonate masses and (iii) is not supported by analogy with sexual dimorphisms in modern birds, in which elongated central rectrices are mostly sex-independent. Available information on C. sanctus is readily reconciled if we assume a bird-like life history, as well as a pronounced sexual size dimorphism and sexually isomorphic extravagant feathers as frequently observed in extant species.     

En1 and Wnt7a interact with Dkk1 during limb development in the mouse

Wnt signaling plays an essential role in induction and development of the limb. Missing digits are one consequence of the reduced Wnt signaling in Wnt7a null mice, while extra digits result from excess Wnt signaling in mice null for the Wnt antagonist Dkk1. The extra digits and expanded apical ectodermal ridge (AER) of Dkk1-deficient mice closely resemble En1 null mice. To evaluate the in vivo interaction between En1 and the canonical Wnt signaling pathway, we generated double and triple mutants combining the hypomorphic doubleridge allele of Dkk1 with null alleles of En1 and Wnt7a. Reducing Dkk1 expression in Dkk1d/+Wnt7a-/- double mutants prevented digit loss, indicating that Wnt7a acts through the canonical pathway during limb development. Reducing Dkk1 levels in Dkk1d/dEn1-/- double mutants resulted in severe phenotypes not seen in either single mutant, including fused bones in the autopod, extensive defects of the zeugopod, and loss of the ischial bone. The subsequent elimination of Wnt7a in Dkk1d/dEn1-/-Wnt7a-/- triple mutants resulted in correction of most, but not all, of these defects. The failure of Wnt7a inactivation to completely correct the limb defects of Dkk1d/dEn1-/- double mutants indicates that Wnt7a is not the only gene regulated by En1 during development of the mouse limb.     

Ultrastructure of spermiogenesis and spermatozoa in Mesocastrada fuhrmanni Voltz, 1898 (Platyhelminthes, Rhabdocoela, Typhloplanoida)

Electron microscopy of the testes of the free-living flatworm Mesocastrada fuhrmanni collected from temporary freshwater ponds shows stages of spermiogenesis that are like other species of the Typhloplanidae. Spermiogenesis in Mesocastrada fuhrmanni is characterized by the presence, in the spermatid, of a differentiation zone underlain by peripheral microtubules and centered on two centrioles with an intercentriolar body. Two flagella of the 9+“1” pattern of the Trepaxonemata grow out in opposite directions from the centrioles. The flagella undergo a latero-ventral rotation, and a subsequent disto-proximal rotation of centrioles occurs in the spermatid. The former rotation involves the compression and the detachment of a row of cortical microtubules, and allows us to recognize a ventral from a dorsal side. Two features are of special interest at the end of differentiation: peripheral cortical microtubules lie parallel to the sperm axis near the anterior tip, but microtubules become twisted (about 40° with reference to the gamete axis) near the posterior extremity; in the same way, the posterior tip of the nucleus is spiralled. As far as we know, these features are observed for the first time in the Typhloplanidae. The pattern of spermiogenesis and the ultrastructural organization of the spermatozoon are compared with the available data on Typhloplanoida and in particular, species of the Typhloplanidae family.