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At least 415 records · Page 23Linked to original sources

PubMed2003

Expression of the lacZ reporter gene in sporophytes of the seaweed Laminaria japonica (Phaeophyceae) by gametophyte-targeted transformation.

The seaweed Laminaria japonica (Phaeophyceae) has a two-generation life cycle consisting of haploid gametophytes and diploid sporophytes. Female and/or male gametophytes were transformed using particle bombardment and the histological LacZ assay was performed on sporophytes generated by either parthenogenesis or inbreeding. Female gametophyte-targeted transformation resulted in similar lower efficiencies in both parthenogenetic and zygotic sporophytes, and only a chimeric expression pattern was observed. Male gametophyte-targeted transformation led to a higher efficiency, with 3.5% of the zygotic sporophytes stained completely blue (all-blue), implying the integration of lacZ at the one-cell stage. Polymerase chain reaction analysis using primers specific for a lacZ-vector juncture fragment and subsequent blotting indicated the presence of the introduced gene in the sporophytes. The method reported here has a potential for seaweed transformation using spore-based bombardment followed by the developmental process.

Genes, Reporter↗

PubMed2004

Biology, ecology and control of the Penthaleus species complex (Acari: Penthaleidae).

Blue oat mites, Penthaleus spp. (Acari: Penthaleidae), are major agricultural pests in southern Australia and other parts of the world, attacking various pasture, vegetable and crop plants. Management of these mites has been complicated by the recent discovery of three cryptic pest species of Penthaleus, whereas prior research had assumed a single species. The taxonomy, population genetics, ecology, biology and control of the Penthaleus spp. complex are reviewed. Adult Penthaleus have a dark blue-black body approximately 1 mm in length, and eight red-orange legs. Within Australia, they are winter pests completing two or three generations a season, depending on conditions. The summer is passed as diapausing eggs, when long-distance dispersal is thought to occur. The Penthaleus spp. reproduce by thelytokous parthenogenesis, with populations comprising clones that differ ecologically. The three pest Penthaleus spp. differ markedly in their distributions, plant hosts, timing of diapause egg production and response to pesticides, highlighting the need to develop control strategies that consider each species separately. Chemicals are the main weapons used in current control programs, however research continues into alternative more sustainable management options. Host plant resistance, crop rotations, conservation of natural enemies, and improved timing of pesticide application would improve the management of these pests. The most cost-effective and environmentally acceptable means of control will result from the integration of these practices combined with the development of a simple field-based kit to distinguish the different mite species.

Agriculture↗

PubMed1981

Calmodulin activates NAD kinase of sea urchin eggs: an early event of fertilization.

NAD kinase, one of the first enzymes activated after fertilization of sea urchin eggs, is regulated by Ca2+ and calmodulin in vitro. The evidence is the requirement for low amounts of Ca2+ (Kd for Ca2+ of 4 x 10(-7) M) and the dissociation of a heat-stable activator from the enzyme which is similar to calmodulin on the basis of radioimmunoassay, activation of bovine brain phosphodiesterase and coelectrophoresis of a major protein of the activator fraction with bovine calmodulin. Also, the calcium stimulation of the enzyme is prevented by trifluoperazine, an inhibitor of calmodulin-associated reactions. In vivo studies show that the enzyme is activated by artificial parthenogenesis regimes that increase cytosolic Ca2+, but not by ammonia activation which only partially activates eggs and bypasses the Ca2+-rise step. These in vitro and in vivo studies indicate that calmodulin is part of the linkage between the rise in Ca2+ at fertilization and the turning on of egg metabolism.

Animals↗

PubMed1987

Parental legacy determines methylation and expression of an autosomal transgene: a molecular mechanism for parental imprinting.

We have created a transgenic mouse strain in which an autosomal transgene bearing elements of the RSV LTR and a translocated c-myc gene obeys very unusual rules. If the transgene is inherited from the male parent, it is expressed in the heart and no other tissue. If it is inherited from the female parent, it is not expressed at all. This pattern of expression correlates precisely with a parentally imprinted methylation state evident in all tissues. Methylation of the transgene is acquired by its passage through the female parent and eliminated during gametogenesis in the male. These observations provide direct molecular evidence that autosomal gene expression can depend upon the sex of the parent from which the gene is inherited. They also provide a plausible mechanism for understanding parental imprinting that may be relevant to the failure of parthenogenesis in mammals, the apparent non-Mendelian behavior of some autosomal genes, and the role of methylation in gene regulation.

Animals↗

PubMed1993

Effect of epidermal growth factor (EGF) and defined simple media on in vitro bovine oocyte maturation and early embryonic development.

The purpose of this study is to evaluate the effect of EGF and defined simple media on in vitro bovine oocyte maturation and early embryonic development. Bovine follicular oocytes were matured in vitro and co-cultured with frozen-thawed bull sperm, which was capacitated with Hepes buffered saline (HBS) solution. After incubation of oocyte-sperm complexes for 4 days, the cleavage rate was evaluated. The results obtained were as follows: 1) When bovine oocytes were matured and embryos were developed in Park-Lin medium 1 (PL(1)) containing fetal calf serum (FCS) or EGF + bovine serum albumin (BSA), the latter treatment was more effective in inducing embryonic cleavage (18%) than FCS alone (10%). 2) When bovine oocytes were matured in Park-Lin medium 2 (PL(2)) without EGF and the subsequent embryos were developed in PL(2) medium with EGF, the cleavage rate was 22.6%. 3) When bovine oocytes were matured in PL(2) medium with EGF and then the embryos were developed in PL(2) medium with EGF, the cleavage rate was 35.8%. 4) When bovine oocytes were matured in Park-Lin medium 3 (PL(3)) without EGF and then the embryos were developed in PL(3) medium, the cleavage rate was 50%. 5) When bovine oocytes and resulting embryos were matured in PL(3) medium with EGF, the cleavage rate was 53%. 6) The parthenogenesis rate induced by PL(3) medium in our current study was comparable to the findings reported by other laboratories. These results suggest that EGF stimulates in vitro bovine oocyte maturation and subsequently affects embryonic development. It is suggested that PL(3) medium is a better defined simple medium than the other media currently used by other laboratories for in vitro bovine oocyte maturation.

Journal Article↗

PubMed1987

An idea on the genesis of the first cancer cell.

The first malignant cell could be the result of a type of fertilization or parthenogenesis between somatic cells that have undergone a meiotic or meiotic-like process initiated by carcinogens and viruses or occurring as a result of genetic errors.

Cell Transformation, Neoplastic↗

PubMed1995

Phylogenetic analysis of the genus Rickettsia by 16S rDNA sequencing.

Rickettsiae are Gram-negative bacteria which multiply only inside host cells and need arthropods either as reservoirs or as vectors. Using the polymerase chain reaction and an automated laser fluorescent DNA sequencer, we amplified and sequenced the 16S rRNA (rDNA) of all available bacteria of the genus Rickettsia. R. tsutsugamushi remained close to the other bacteria of the genus Rickettsia using this technique, contrary to previous conclusions based on the study of the Sta-58 protein antigen. We found that R. canada was not included in the typhus group, as is currently recognized, but was grouped with the rickettsiae of the spotted fever group (SFG). All the SFG rickettsiae tested were grouped in the same cluster (R. conorii, Indian tick typhus rickettsia, Astrakhan fever rickettsia, Israeli tick typhus rickettsia, HA-91, R. sibirica, R. parkeri, "R. africae", "R. slovaca", R. rickettsii, Thai tick typhus rickettsia, R. japonica, R. massiliae, R. rhipicephali, R. montana, two recent isolates GS and Bar 29, R. australis, R. akari, R. bellii and R. helvetica). The recently described ELB bacterium, the agent of the Californian murine typhus, and AB bacterium, a bacterium associated with male killing in the ladybird beetle, were found in this cluster. The sequences of R. conorii Moroccan strain/Indian tick typhus rickettsia, R. massiliae/GS and R. sibirica/HA-91 were identical. All the rickettsiae had a unique ancestor with bacteria also isolated in arthropods (Ehrlichia, Cowdria, Anaplasma, Wolbachia pipientis), eventually pathogenic for mammals and implicated in parthenogenesis and cytoplasmic incompatibility. We conclude that a unique bacterium started a stable association with arthropod ancestors and generated the observed diversity of the currently isolated members of the Rickettsiales.

Base Sequence↗

PubMed2006

In vitro maturation and intracytoplasmic sperm injection of oocytes collected from hormonally stimulated common wombats, Vombatus ursinus.

Porcine FSH/LH stimulation successfully induced development of multiple large (>or=4mm) antral follicles in 10 of 11 common wombats. A mean of 5.5 metaphase II (MII) oocytes were aspirated from wombats that were stimulated during the follicular phase of the oestrous cycle (n=3) or after pouch young removal (n=3). Three subadults (n=3) and two anoestrus adults did not produce MII oocytes despite pFSH/pLH administration. In vitro maturation of immature oocytes at the time of aspiration doubled the number of MII oocytes that could be collected from pFSH/pLH stimulated wombats. Immature oocytes with cumulus attached, matured more readily to the MII stage than immature oocytes without cumulus. Following intracytoplasmic sperm injection (ICSI), approximately 5% of the oocytes that were MII at the time of collection cleaved. Approximately 5% of those that were matured by in vitro maturation (IVM) formed two polar bodies following ICSI, although they not cleave. Parthenogenesis cannot be excluded. This demonstrates that assisted reproductive technologies may be applicable to the common wombat.

Animals↗

PubMed2006

Effect of ambient temperature on in vitro fertilization of Bubaline oocyte.

The present study was used to examine the effect of ambient temperature on the day of slaughter of buffaloes on oocyte cleavage and subsequent embryo development following in vitro fertilization (IVF)/chemical activation (parthenogenesis). A total of 601 oocytes were collected from buffaloes, which were sacrificed when the ambient temperature was >40 or < or =40 degrees C and the collected oocytes were matured in vitro. During each experiment about half of the matured oocytes were used for IVF whereas the remaining oocytes were subjected to one of the three chemical activation protocols viz. (i) 7% ethanol (ET) and 6-di methyl amino purine (6-DMAP), (ii) ET and cycloheximide (CHX) and (iii) ET followed by a combined treatment of 6-DMAP and CHX. Cleaved oocytes were cultured in mSOF supplemented with BSA, essential amino acids, non-essential amino acids, ITS (insulin transferrin and selenium) and L-glutamine. Low cleavage and subsequent embryo development was observed in those oocytes which were collected from buffaloes slaughtered at ambient temperature >40 degrees C than at < or =40 degrees C. There was no significant difference in cleavage rate following different chemical activations in oocytes collected from buffaloes slaughtered on the day when the maximum ambient temperature was >40 degrees C or < or =40 degrees C. These results suggest that high ambient temperature influences competence of oocytes to cleave and develop to blastocyst stage following natural activation with sperm and/or process of fertilization and subsequent embryo development.

Adenine↗

PubMed2005

Production of male neonates in four cladoceran species exposed to a juvenile hormone analog, fenoxycarb.

Previous studies have found that exposure of a cyclic parthenogen, the water flea Daphnia magna (Cladocera, Crustacea), to juvenile hormones and their analogs results in the production of neonates of male sex at concentration-dependent rates. We conducted reproduction experiments in four different species (Moina macrocopa, M. micrura, Ceriodaphnia dubia and C. reticulata) of cladoceran to test for the first time whether the occurrence of this phenomenon after exposure of the parent to such hormones is a generalized phenomenon. In the presence of a juvenile hormone analog, fenoxycarb, all four species produced male neonates and showed reduced rates of reproduction. The estimated median effective concentration (EC50) for the production of male neonates varied with species, ranging from 0.60 x 10(3) to 9.3 x 10(3) ng/l. Although there was a wide range of sensitivity to fenoxycarb, the production of male neonates in all four species demonstrates that this phenomenon is a common response to juvenile hormone analogs and further suggests that these hormones are capable of initiating sexual reproduction in cladocerans, most of which exhibit cyclic parthenogenesis.

Animals↗

PubMed2005

Production of male neonates in Daphnia magna (Cladocera, Crustacea) exposed to juvenile hormones and their analogs.

We exposed the water flea Daphnia magna (Cladocera, Crustacea) to either juvenile hormone I (JH I), juvenile hormone II (JH II), or the juvenile hormone-mimicking insecticides kinoprene, hydroprene, epofenonane, or fenoxycarb. By 21-day reproduction tests, we investigated the effects on the number of neonates born per female and the offspring sex ratio. All six chemicals induced D. magna to produce male neonates; the male sex ratio of the offspring increased as the chemical concentration increased. EC50 values for production of male neonates were estimated as 400 (JH I), 410 (JH II), 190 (kinoprene), 2.9 (hydroprene), 64 (epofenonane), and 0.92 (fenoxycarb) microg/l. The number of neonates produced was reduced with all chemicals at the concentrations investigated. At the EC50 for male production, five of the six chemicals reduced the reproductive rate to less than 50%; the exception was epofenonane, which caused only a slight reduction in reproductive rate. These results were similar to those obtained for five juvenoids studied previously, one of which was studied here again. There are now 10 chemical substances--all juvenile hormones or their analogs-that are known to induce D. magna to produce male neonates. This suggests that juvenile hormone is involved in initiating male production followed by sexual reproduction in D. magna, and probably in most cladocerans that exhibit cyclic parthenogenesis.

Animals↗

PubMed2006

The evolutionary biology of sex.

In 1861, Charles Darwin wrote "We do not even in the least know the final cause of sexuality; why new beings should be produced by the union of the two sexual elements, instead of by a process of parthenogenesis". It was hardly possible to begin to answer this question at that time, in view of the contemporary lack of knowledge of genetics and cell biology. Since then, research into the cellular basis of reproduction has shown that sexual reproduction is the norm for the majority of eukaryotes, with huge consequences for their biology. The evolution of sex and some of its consequences are the subject of the series of reviews, and a Primer, in this special issue of Current Biology.

Animals↗

PubMed2004

Wolbachia pipientis: intracellular infection and pathogenesis in Drosophila.

Wolbachia pipientis is a vertically transmitted, obligate intracellular symbiont of arthropods. The bacterium is best known for its ability to manipulate host reproductive biology where it can induce cytoplasmic incompatibility, parthenogenesis, feminization and male-killing. In addition to the various reproductive phenotypes it generates through interaction with host reproductive tissue it is also known to infect somatic tissues. However, relatively little is known about the consequences of infection of these tissues with the exception that in some hosts Wolbachia acts as a classical mutualist and in others a pathogen, dramatically shortening adult insect lifespan. Manipulation experiments have demonstrated that the severity of Wolbachia-induced effects on the host is determined by a combination of host genotype, Wolbachia strain, host tissue localization, and interaction with the environment. The recent completion of the whole genome sequence of Wolbachia pipientis wMel strain indicates that it is likely to use a type IV secretion system to establish and maintain infection in its host. Moreover, an unusual abundance of genes encoding proteins with eukaryotic-like ankyrin repeat domains suggest a function in the various described phenotypic effects in hosts.

Animals↗

PubMed2006

Mitochondrial distribution and microtubule organization in fertilized and cloned porcine embryos: implications for developmental potential.

Mitochondrial distribution and microtubule organization were examined in porcine oocytes after parthenogenesis, fertilization and somatic cell nuclear transfer (SCNT). Our results revealed that mitochondria are translocated from the oocyte's cortex to the perinuclear area by microtubules that either constitute the sperm aster in in vitro-fertilized (IVF) oocytes or originate from the donor cell centrosomes in SCNT oocytes. The ability to translocate mitochondria to the perinuclear area was lower in SCNT oocytes than in IVF oocytes. Sperm-induced activation rather than electrical activation of SCNT oocytes as well as the presence of the oocyte spindle enhanced perinuclear mitochondrial association with reconstructed nuclei, while removal of the oocyte spindle prior to sperm penetration decreased mitochondrial association with male pronuclei without having an apparent effect on microtubules. We conclude that factors derived from spermatozoa and oocyte spindles may affect the ability of zygotic microtubules to translocate mitochondria after IVF and SCNT in porcine oocytes. Mitochondrial association with pronuclei was positively related with embryo development after IVF. The reduced mitochondrial association with nuclei in SCNT oocytes may be one of the reasons for the low cloning efficiency which could be corrected by adding yet to be identified, sperm-derived factors that are normally present during physiological fertilization.

Animals↗

PubMed1987

The molecular basis of the evolution of sex.

Traditionally, sexual reproduction has been explained as an adaptation for producing genetic variation through allelic recombination. Serious difficulties with this explanation have led many workers to conclude that the benefit of sex is a major unsolved problem in evolutionary biology. A recent informational approach to this problem has led to the view that the two fundamental aspects of sex, recombination and outcrossing, are adaptive responses to the two major sources of noise in transmitting genetic information, DNA damage and replication errors. We refer to this view as the repair hypothesis, to distinguish it from the traditional variation hypothesis. On the repair hypothesis, recombination is a process for repairing damaged DNA. In dealing with damage, recombination produces a form of informational noise, allelic recombination, as a by-product. Recombinational repair is the only repair process known which can overcome double-strand damages in DNA, and such damages are common in nature. Recombinational repair is prevalent from the simplest to the most complex organisms. It is effective against many different types of DNA-damaging agents, and, in particular, is highly efficient in overcoming double-strand damages. Current understanding of the mechanisms of recombination during meiosis suggests that meiosis is designed for repairing DNA. These considerations form the basis for the first part of the repair hypothesis, that recombination is an adaptation for dealing with DNA damage. The evolution of sex can be viewed as a continuum on the repair hypothesis. Sex is presumed to have arisen in primitive RNA-containing protocells whose sexual process was similar to that of recombinational repair in extent segmented, single-stranded RNA viruses, which are among the simplest known organisms. Although this early form of repair occurred by nonenzymatic reassortment of replicas of undamaged RNA segments, it evolved into enzyme-mediated breakage and exchange between long DNA molecules. As some lines of descent became more complex, their genome information increased, leading to increased vulnerability to mutation. The diploid stage of the sexual cycle, which was at first transient, became the predominant stage in some lines of descent because it allowed complementation, the masking of deleterious recessive mutations. Out-crossing, the second fundamental aspect of sex, is also maintained by the advantage of masking mutations. However, outcrossing can be abandoned in favor of parthenogenesis or selfing under conditions in which the costs of mating are very high.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1998

Cleavage, development and competence of sheep embryos fertilized by intracytoplasmic sperm injection and in vitro fertilization.

More abnormal fertilization has been found in sheep oocytes after intracytoplasmic sperm injection (ICSI) than after in vitro fertilization (IVF). Although the birth of a normal lamb has been reported, the efficiency of blastocyst production is low. We therefore evaluated the cleavage, development and viability of sheep embryos obtained from ICSI, IVF and sham injection. In vitro matured oocytes either injected or inseminated with spermatozoa were assessed for cleavage 1 and 4 d after injection or insemination, and for development to blastocyst after 7 d of culture. A total of 699 oocytes was injected (ICSI); 198 (30.6%) were activated and 55 (8.5%) developed to the blastocyst stage. Of the 17 recipient ewes with 1, 2, 3 or 4 embryos, 15 (88.2%) were pregnant on Day 18; of these 17 recipients, 7 (41.1%) and 6 (35.2%) ewes remained pregnant on Days 45 and 110, respectively. Two normal lambs were born, one ewe died on Day 110 with 2 normal male fetuses, another ewe aborted on Day 90 and 4 pregnancies were maintained. A total of 517 oocytes was inseminated (IVF); 296 (62%) were activated and 90 (18.8%) reached the blastocyst stage. A total of 19 ewes received 1, 2, 3 or 4 embryos; of these, 13 (68.4%) were pregnant on Day 18, 8 (42.1%) ewes remained pregnant on each of Days 45 and 110. Three ewes delivered 5 lambs. Five pregnancies were maintained. A total of 156 oocytes was sham injected, 38 (24.3%) were activated and no blatocysts were obtained after culture. The results of this study showed that blastocysts obtained after ICSI are potentially viable and are not a result of parthenogenesis.

Animals↗

PubMed2001

Oral mature teratoma containing epididymal tissue in a female neonate.

We describe a female neonate with an oral teratoma showing bone, teeth, and epidermis, but also epididymal (male) tissue. PCR amplification of Y-chromosomal DNA clearly showed male DNA from paraffin-embedded tumour tissue. The girl had a normal female karyotype without abnormalities of the genital organs. There are at least three hypotheses for the origin of teratomas: parthenogenesis, incomplete twinning, and totipotent somatic-cell origin. This case supports the hypothesis of an included dizygotic twin, and might contribute to the elucidation of the pathogenesis of extragonadal teratomas.

DNA↗

PubMed2002

Development of a multispecies system for testing reproductive effects on aquatic invertebrates. Experience with Daphnia magna, Chironomus prasinus and Lymnaea peregra.

A cost /effective innovative approach combining three freshwater invertebrates: the cladoceran Daphnia magna, the insect Chironomus prasinus and the basommatophoran snail Lymnaea peregra, in a single system is presented. The selection combines different reproductive strategies: parthenogenesis, sexual reproduction and hermaphroditism, respectively, and covers water column, sediment, food and contact exposure. Results confirm the system's capacity. In 46 days, multi-generation, whole-life-cycle, and chronic reproduction assays can be achieved for D. magna, C. prasinus and L. peregra, respectively. The 21-day D. magna test is commonly used to assess the effects of chemicals on aquatic invertebrates. Wide concerns on its suitability for testing endocrine disrupting chemicals have been raised, particularly for substances with estrogenic activities. The combination of three species with different reproductive strategies offer a suitable approach for assessing ecologically relevant effects related to any mechanism of action, including endocrine disruption.

Animals↗