Timing Of Developmental Stages Research Articles

Morphological variation in first-formed shells of the Ordovician Paucicrura–Diceromyonia brachiopod lineage of North America

Abstract First-formed shells of several species of Dalmanellidae (Brachiopoda) from the Ordovician (Katian) of North America were measured and compared: Cincinnetina multisecta, Diceromyonia tersa, Diceromyonia storeya, Paucicrura corpulenta, Paucicrura rogata, and Paucicrura sillimani. Sizes and structures of the first-formed shells suggest that members of this family had planktotrophic subadults, with some species showing indications of only an unshelled larval stage and others showing both a larval stage and a shelled juvenile stage. This differs from modern rhynchonelliformean brachiopods, which all possess only a lecithotrophic larval stage. The range of sizes of first-formed shells of most studied species are similar, but P. sillimani of Baffin Island, Canada (middle Katian), has a significantly larger first-formed shell that formed during an extended juvenile stage. This may have enabled the species to colonize newly exploitable habitats during an interval of rapid sea level rise in Laurentia during the Katian. This plasticity of developmental modes in the Dalmanellidae shows not only that using distantly related modern brachiopods as an analog for extinct Paleozoic lineages may be misleading, but also that development can vary within a single lineage and that timing of developmental stages should not be considered a reliable character for use in phylogenetic studies of brachiopods.

Characterizing oogenesis and programmed cell death in the eastern tree hole mosquito Aedes (Protomacleaya) triseriatus.

Oogenesis in flies manifests as a carefully orchestrated cascade of developmental gates and growth events, punctuated by programmed cell death (PCD) and follicular resorption events. In anautogenous mosquitoes, a blood meal stimulates growth of primary follicles, but the timing of developmental stages is species-specific, and few species have been characterized. Here, we characterize the first gonotrophic cycle of oogenesis in Aedes triseriatus (Diptera: Culicidae), the principal vector of La Crosse Virus (LACV), a major cause of pediatric encephalitis in North America. We note significant differences in the timing and appearance of developmental stages from previous studies of other mosquito species, particularly Aedes aegypti. We also describe the appearance and timing of PCD events including atresia, nurse cell death, and follicular epithelium death and show that the majority of follicular epithelium cells do not undergo apoptosis during oogenesis but persist in the ovariole at least until the second gonotrophic cycle. This thorough characterization of oogenesis and PCD in Ae. triseriatus, through which LACV must persist in order to achieve filial infection, also serves as a baseline to study host-pathogen interactions during transovarial transmission.

Why and How Imprinted Genes Drive Fetal Programming.

Imprinted genes mediate fetal and childhood growth and development, and early growth patterns drive fetal programming effects. However, predictions and evidence from the kinship theory of imprinting have yet to be directly integrated with data on fetal programming and risks of metabolic disease. I first define paternal-gene and maternal-gene optima with regard to early human growth and development. Next, I review salient evidence with regard to imprinted gene effects on birth weight, body composition, trajectories of feeding and growth, and timing of developmental stages, to evaluate why and how imprinted gene expression influences risks of metabolic disease in later life. I find that metabolic disease risks derive primarily from maternal gene biases that lead to reduced placental efficacy, low birth weight, low relative muscle mass, high relative white fat, increased abdominal adiposity, reduced pancreatic β-cell mass that promotes insulin resistance, reduced appetite and infant sucking efficacy, catch-up fat deposition from family foods after weaning, and early puberty. Paternal gene biases, by contrast, may contribute to metabolic disease via lower rates of brown fat thermiogenesis, and through favoring more rapid postnatal catch-up growth after intrauterine growth restriction from environmental causes. These disease risks can be alleviated through dietary and pharmacological alterations that selectively target imprinted gene expression and relevant metabolic pathways. The kinship theory of imprinting, and mother-offspring conflict more generally, provide a clear predictive framework for guiding future research on fetal programming and metabolic disease.

Effects of Fluoxetine on Human Embryo Development.

The use of antidepressant treatment during pregnancy is increasing, and selective serotonin reuptake inhibitors (SSRIs) are the most widely prescribed antidepressants in pregnant women. Serotonin plays a role in embryogenesis, and serotonin transporters are expressed in two-cell mouse embryos. Thus, the aim of the present study was to evaluate whether fluoxetine, one of the most prescribed SSRI antidepressant world-wide, exposure influences the timing of different embryo developmental stages, and furthermore, to analyze what protein, and protein networks, are affected by fluoxetine in the early embryo development. Human embryos (n = 48) were randomly assigned to treatment with 0.25 or 0.5 μM fluoxetine in culture medium. Embryo development was evaluated by time-lapse monitoring. The fluoxetine-induced human embryo proteome was analyzed by shotgun mass spectrometry. Protein secretion from fluoxetine-exposed human embryos was analyzed by use of high-multiplex immunoassay. The lower dose of fluoxetine had no influence on embryo development. A trend toward reduced time between thawing and start of cavitation was noted in embryos treated with 0.5 μM fluoxetine (p = 0.065). Protein analysis by shotgun mass spectrometry detected 45 proteins that were uniquely expressed in fluoxetine-treated embryos. These proteins are involved in cell growth, survival, proliferation, and inflammatory response. Culturing with 0.5 μM, but not 0.25 μM fluoxetine, caused a significant increase in urokinase-type plasminogen activator (uPA) in the culture medium. In conclusion, fluoxetine has marginal effects on the timing of developmental stages in embryos, but induces expression and secretion of several proteins in a manner that depends on dose. For these reasons, and in line with current guidelines, the lowest possible dose of SSRI should be used in pregnant women who need to continue treatment.

Type of rheoreaction in the early ontogenesis of roach Rutilus rutilus (L.) as a factor determining its biotopic distribution

The specific features of rheoreaction in roach Rutilus rutilus (L.) larvae from open and protected shallows of the Rybinsk Reservoir have been studied. Data on length and weight of roach sampled at various habitats at B–E developmental stages are presented. It has been revealed that the type of roach larvae rheoreaction is a behavioral mechanism of their distribution over different types of habitats, not only in rivers but also in the waterbodies with slow water turnover rates—lakes and reservoirs. By the time of developmental stage E, this mechanism provides the sustainable spatial separation of juvenile fish, which in the future may lead to intrapopulation differentiation in roach.

Modelling flowering time of rhododendron

Plant phenology, primarily affected by temperature and photoperiod, is a useful indicator to study the effects of climate change. Even though, it is a proven fact that climate change has affected the phenology of a wide range of species, but degree of impact varies across the species. It is very important to understand the sequence and timing of developmental stages (phenological events) such as bud development and flowering time in response to change in environmental conditions. Along with the identity of being a national flower of Nepal, the beauty of the rhododendron flower welcomes thousands of foreign tourist every year. Non uniformity in flowering time of rhododendron in recent years across the region is commonly expressed by local people and also reported in recent local news. To understand the flowering time behavior of rhododendron a flowering time model was developed in this study. The good agreement between observed and simulated flowering time during the calibration process showed that the developed model has the potential for predicting flowering time of Rhododendron arboreum in response to temperature and photoperiod. Simulation results (Late flowering in higher elevation and early in lower elevation) showed that there exists a linear relationship between altitude and flower onset time of rhododendron in Nepal. In addition, flowering time prediction in response to future climate data showed that phenology of rhododendron is going to shift early as the year advances.

Gene Expression in Thyroxin-Induced Metamorphosing Axolotl Hearts

The Mexican axolotl (Ambystoma mexicanum) is a unique model to study vertebrate heart development for several reasons. In addition to the wild-type animal, there is also an embryonic lethal condition caused by a homozygous recessive mutation in cardiac gene “c” [1,2]. These mutant embryonic hearts do not contract, are deficient in tropomyosin, and lack organized myofibrils [3,4], making them an excellent model to study the process of cardiac myofibrillogenesis [5,6]. In contrast to most other model organisms currently being utilized, axolotl embryos are comparatively large (2mm diameter), hence, they can be studied with relative ease. Being amphibians, axolotl embryos mature externally within jelly coats. Therefore, unlike using mammalian embryos, it is unnecessary to sacrifice the parent. Moreover, an average of a hundred axolotl embryos are produced from a single spawning and these embryos develop relatively slowly which is useful for studying vital developmental stages of interest [7]. In fact the timing of developmental stages of interest may be controlled to some extent, as the rate of development for these poikilothermic animal embryos is temperature dependent [8].

Effect of oxygen concentration on human embryo development evaluated by time-lapse monitoring

To evaluate, using time-lapse monitoring, the temporal influence of culture in 5% O2 or 20% O2 on human embryonic development. Retrospective cohort study. University-based fertility clinic. Invitro fertilized embryos from women aged <38 years with no endometriosis and ≥8 oocytes retrieved. Culture in 20% O2 exclusively (group 1), 20% and 5% O2 combined (group 2), or 5% O2 exclusively (group 3). Developmental rates and timing of developmental stages. The timing of the third cleavage cycle was delayed for embryos cultured in 20% O2 (group 1) compared with embryos cultured in 5% O2 (groups 2 and 3). No difference was observed in timing of the early and full blastocyst stages. More embryos in groups 2 and 3 reached the 8-cell, early blastocyst, and full blastocyst stages than in group 1. We found that embryos in group 3 (5% O2) reached the 8-cell stage faster than embryos in group 2 (5% + 20% O2), but none of the other parameters (i.e., other time points, cumulative development, and embryo score) differed between the two groups. Culture in 20% O2 reduces developmental rates and delays completion of the third cell cycle. The delayed development after culture in atmospheric oxygen was seen in the precompaction embryo only and therefore appears to be stage specific. NCT01139268.

The postmarsupial development of Porcellio siculoccidentalis, with some data on reproductive biology (Crustacea, Isopoda, Oniscidea)

In the broader context of research on the Sicilian Porcellio imbutus-complex, the postmarsupial development of Porcellio siculoccidentalis Viglianisi, Lombardo & Caruso, 1992 was studied in detail. This research was conducted in the laboratory under controlled conditions, allowing us to follow the stages of development, from the formation of the marsupium in ovigerous females until the larval stages and development of the seventh pair of legs. The timing of developmental stages and the morphological modifications of appendages in the postmarsupial manca stages (M I–M III) are described. The manca stage M I had a duration of about one hour. Ovigerous females were collected and reared separately, and the number of parturial molts in the absence of males was counted. The results showed a maximum of four successive parturial molts. Fecundity and fertility were evaluated as the number of eggs and embryos, respectively, inside the marsupium of the ovigerous females. Both parameters were positively correlated with the size of the females. The maximum numbers of eggs and embryos in the marsupium were 113 and 141, respectively. Data describing the total number of postmarsupial mancas released per month indicated that the highest release occurred in April.

Timing of developmental stages in permanent mandibular teeth of Finns from birth to age 25

Objective. The aim was to provide radiographic data on postnatal development of the 8 mandibular teeth to serve as reference norms in clinical dentistry, forensic dentistry, anthropology, and research. Material and Methods. Developmental stages of teeth were assessed from a total of 2795 radiographs, mostly panoramic, of 1970 Finns (966 M and 1004 F) from birth to age 25. The grading was based on Demirjian's 8 mineralization stages and the crypt stage. Results. Timing of development in individual mandibular teeth is presented in two ways: as age at attainment of each developmental stage and as age of subjects in a developmental stage. Initiation of mineralization was visible in 1st molars at 0.20 years, in central incisors at 0.22 years, lateral incisors at 0.37 years, and canines at 0.56 years of age. Timing was usually earlier in girls than in boys. Differences were greatest in canines, where females were advanced by 1.74 years at the closure of the apex. Root development in 3rd molars showed an opposite trend, where apical closure was 1.19 years earlier in men. In 3rd molars, age at apical closure in females was 21.50 years, among the highest reported. In general, the early developmental stages had the shortest duration and the last stages the longest. Conclusion. Timing of postnatal development of individual mandibular teeth in Finns resembled developmental schedules reported for other Caucasian population groups. Any differences were mostly small and inconsequential.

Maternal care and infant behaviour of the bridled nailtail wallaby (Onychogalea fraenata)

AbstractBridled nailtail wallabies Onychogalea fraenata are endangered, medium‐sized, nocturnal macropodids that persist at only one location in central Queensland, Australia. Characteristics of juvenile development, shelter use, anti‐predator behaviour and maternal care were investigated in the wild using trapping, radio‐tracking and spotlighting observations. Timing of developmental stages was identical to the pattern previously found in captivity, except for age at weaning which was much earlier in the wild. After young had left the pouch permanently at 17 weeks of age and weighing c. 800 g, they always spent the day concealed in dense cover, generally &gt;200 m from their mothers. Juveniles were also alone in &gt;50% of observations at night, and stayed closer to cover than did adult females. Young became independent of their mothers 7–8 weeks after permanent exit from the pouch and weighing c. 1800 g. Females with dependent juveniles changed their behaviour in ways likely to reduce predation on young. They reduced their home ranges, stayed closer to cover and became more wary than other females. Juveniles differed from adult females in their habitat use, anti‐predator behaviour and shelter site preferences. Juveniles were more likely than adults to respond to threats by standing still or lying flat on the ground, whether or not they were in concealing cover. Juveniles used a wider range of smaller shelters than adults, and were less likely to use solid shelters such as hollow logs during the day. Because bridled nailtail wallabies have a ‘hider’ strategy of maternal care and the young rely on crypsis, successful breeding in the wild requires dense vegetation cover.

Evaluation of the pregnancy immunotrophism hypothesis by assessment of the reproductive performance of young adult mice of genotype scid/scid.bg/bg

The hypothesis that enhancement of pregnancy success results from immune recognition of the conceptus was evaluated by studying reproductive performance in a new line of mice deficient in NK cells and lacking B cells and T cells. Doubly mutant mice of genotype scid/scid.bg/bg are both viable and fertile. The numbers of offspring born to pairs of this genotype were not different from numbers born to heterozygous pairs. Differences in prenatal loss could not be found between genotypes by counts of either fetal resorption sites or corpora lutea. The timing of developmental stages and the differentiation of trophoblast, placenta, decidua and metrial gland in scid/scid.bg/bg mice appeared normal. These results suggest either that lymphokine influences on trophoblast cells in vivo do not contribute, in a major way, to pregnancy success or that the important cytokines are derived from uterine cell populations that are not classical, mature B cells, T cells or NK cells.

Rangeland Grasshoppers (Orthoptera: Acrididae): Modeling Phenology of Natural Populations of Six Species

Data were collected near Roundup, Mont., on phenology of six species of rangeland grasshoppers for 2 years. Logistic probability distribution was used to describe timing of developmental stages (instar 1 through adult) for each generation as a function of accumulated degree-days. Model results showed that there were significant differences in seasonal phenology between the generations for populations of each of the six species examined. However, average number of accumulated degree-days (17.8°C base) before peak instar 3 each year for the six species varied only slightly between seasons. Interspecific comparisons indicated that of the six species, Melanoplus infantilis Scudder developed fastest. Model design, assumptions, and applications as a descriptive tool are discussed, as are potential uses of the model to pest managers.