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Results for “developmental timing”

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At least 19 recordsLinked to original sources
PubMed1990

Clock mutations alter developmental timing in Drosophila.

The developmental time of period mutants in Drosophila melanogaster was monitored under different environmental conditions. We observed that the pers mutants, which have short 19 h circadian cycles, develop faster from eggs to adult than the wild-type: perL mutants, which have long 28 h circadian rhythms, complete development more slowly than the wild-type. These results suggest that endogenous timers may be involved in regulating the development time of D. melanogaster.

Analysis of Variance↗
PubMed1989

Genotype-by-environment and epistatic interactions in Drosophila melanogaster: the effects of Gpdh allozymes, genetic background and rearing temperature on larval developmental time and viability.

The possible role of temperature as a component of natural selection generating the latitudinal clines in Gpdh allele frequencies in natural populations of Drosophila melanogaster was examined. Effects of rearing temperature (16 degrees, 22 degrees and 29 degrees) and of Gpdh allozymes (S and F) on larval developmental time and viability were measured. Eight genetic backgrounds from each of three populations (continents) were used to assess the generality of any effects. Analyses of variance indicated significant temperature effects and allozyme-by-genetic background interaction effects for both characters. Viability showed significant genetic background effects, as well as significant temperature-by-allozyme and temperature-by-allozyme-by-population interactions. In general, the S/S genotype was significantly lower in viability than the F/F and F/S genotypes at extreme temperatures (16 degrees and 29 degrees), with no significant differences at 22 degrees. However, each population had a slightly different pattern of viability associated with temperature, and only the Australian population showed a pattern that could contribute to the observed cline formation. Although the same two interactions were not significant for developmental time, examination of the means showed that the S/S genotype had a slightly faster rate of development at 16 degrees than the F/F genotype in all populations (by an average of 0.25 day or 1.1%). The low temperature effect on developmental time is consistent with the clines observed in nature, with the S allele increasing in frequency with higher latitudes. The results for both viability and developmental time are consistent with the interpretation of Gpdh as a minor polygene affecting physiological phenotypes, as indicated by previous work with adult flight metabolism. Finally, it is proposed that the temperature-dependent antagonistic effects of the allozymes on viability vs. developmental time and flight metabolism may be the underlying force giving rise to the worldwide polymorphism.

Analysis of Variance↗
PubMed1985

The maintenance of polymorphism owing to differences in developmental time and competition.

The effect of developmental time on the maintenance of an enzyme polymorphism is analyzed under the assumption that competition exists for a reproductively essential resource. Specifically, in laboratory vials Drosophila compete for oviposition and pupation sites. This system of competition serves as a prototype for the model with late-eclosing individuals being excluded from the reproductive pool. Two mating behaviors are modelled: (i) mating is with individuals from only the same cohort group and occurs only once, and (ii) mating is with all individuals that have eclosed up to that time and occurs daily. Numerical analyses are done on both mating structures using data from Drosophila mercatorum. The simulations show that mating structure and initial conditions do not affect the equilibrium genotype frequencies, but that slight changes in the level of competition can dramatically alter the equilibrium values.

Alcohol Dehydrogenase↗
PubMed1987

The effect of chemically produced shifts in developmental timing on postmetamorphic morphology in Bombina orientalis.

The effect of altering developmental timing on postmetamorphic morphology was examined in the frog Bombina orientalis. The length of the larval period was manipulated with the use of a thyroid inhibitor. Results show that differences in time to metamorphosis are correlated with shifts in postmetamorphic relative hindlimb length. Furthermore, these differences in relative hindlimb length are similar to those found among closely related species. Variation in the timing of development may be responsible for a significant portion of the postmetamorphic shape variation found among frogs.

Animals↗
PubMed1990

Developmental time and mortality of the reduviid bug Triatoma infestans with differential exposure to coprophagic infections with Blastocrithidia triatomae (Trypanosomatidae).

Developmental time and survival in larvae of the reduviid bug Triatoma infestans were studied in uninfected groups and in those exposed to a coprophagic infection with Blastocrithidia triatomae. Addition to young uninfected larvae of (a) different numbers of infected bugs, (b) infected and uninfected bugs, and (c) fresh or dry infectious feces were compared. Retardation of development was evident in groups given infected larvae or fresh feces. Mortality rates were correlated with infection rates and were higher in groups given more infected bugs, independent of the presence of uninfected bugs. Therefore, bugs did not discriminate between feces from infected and uninfected bugs, or they did not reject infectious feces. Dry feces had to be redissolved with fresh feces before infection was possible.

Animals↗
PubMed1991

Effect of larval diet on cat flea (Siphonaptera: Pulicidae) developmental times and adult emergence.

The natural diet of cat flea, Ctenocephalides felis (Bouche), larvae is primarily adult flea feces, but dried bovine blood may be substituted in the laboratory. Percentage adult emergence (79.4% on feces; 78.9% on blood) and developmental times (20.6 d on feces; 17.1 d on blood) did not significantly differ for the two diets. The drying temperature of blood determined its quality; blood dried at 120 degrees C was unsatisfactory for larval development. The dietary value of dried bovine blood was not enhanced when supplemented with brewer's yeast, rodent chow, or a combination of those constituents. Blood particle size ranging from less than 180 to greater than 500u did not affect the value of blood as a diet. Rodent chow, yeast, albumen, hemoglobin, and mixtures of these constituents were unsuitable as larval diets.

Animals↗
PubMed1988

Developmental time course of the effect of nerve growth factor on the parasympathetic ciliary ganglion.

Neurite outgrowth in the presence and absence of nerve growth factor (NGF) was compared in neuronal cultures from the parasympathetic ciliary ganglion and from a traditional target of NGF, the sensory dorsal root ganglion. Both ciliary and dorsal root ganglion cultures exhibited a developmental time window during which the effect of NGF on neurite length was maximal. Although neuronal cultures from embryonic day 4 and 5 ganglia exhibited considerable neurite outgrowth in the absence of NGF, there was no significant increase in neurite outgrowth in the presence of NGF. After embryonic day 6, there was a steady increase in the effect of NGF in both types of ganglia. With ciliary ganglia, the effect of NGF increased until day 8, plateaued, then fell off significantly after day 11. With dorsal root ganglia, the effect of NGF continued to increase until day 12, plateaued, then fell off significantly after day 17. Thus, the period of maximal responsiveness of chick ciliary ganglia to NGF occurs earlier in development than for dorsal root ganglia. At the ages when the effect of NGF was maximal, approximately 20% of ciliary ganglion neurons exhibited substantial increases in neurite length compared to approximately 40% of dorsal root ganglion neurons. The effect of NGF was maximal at or below 1 ng/ml (4 X 10(-11) M) for both types of ganglia. These results support previous evidence that NGF does not simply boost ciliary ganglionic neurite growth non-specifically: the effect of NGF is already maximal at low, physiological concentrations and it appears at a specific time in development.

Animals↗
PubMed2025

Developmental timing of index trauma exposure and accelerated epigenetic aging in United States military veterans.

Trauma exposure has been linked to accelerated GrimAge, an epigenetic biomarker of premature morbidity and mortality. Building on this evidence, the present study examined whether the type and timing of index trauma exposure are differentially associated with accelerated GrimAge. Participants were 873 European American male United States military Veterans from the National Health and Resilience in Veterans Study. We investigated associations between self-reported age at index trauma, index trauma type (interpersonal violence, non-interpersonal trauma, or loss/instability/other), and accelerated GrimAge, operationalized as GrimAge exceeding chronological age by five or more years. Results revealed that interpersonal violence was associated with three-fold greater odds of accelerated GrimAge compared to other trauma types. Age at index trauma was not independently associated with accelerated GrimAge. However, we observed a significant interaction between trauma type and its developmental timing, even after adjusting for index trauma recency, cumulative trauma burden, and other potential confounders. Specifically, Veterans who were older at the time of exposure to interpersonal violence or trauma involving loss or instability had higher odds of accelerated GrimAge. In contrast, exposure to non-interpersonal trauma was more strongly associated with accelerated GrimAge when it occurred at younger ages. These results indicate that trauma type and timing jointly influence epigenetic aging in Veterans, highlighting the need for tailored interventions that address specific trauma characteristics to reduce associated long-term health risks in this population.

Humans↗
PubMed1985

Deletions within a defective suppressor-mutator element in maize affect the frequency and developmental timing of its excision from the bronze locus.

Six independent derivatives of the bz-m13 allele, which contains a 2.2-kilobase-pair defective Suppressor-mutator (dSpm) insertion at the bronze (bz) locus, have been isolated and analyzed. The derivatives were selected for alterations in the frequency and timing of somatic reversion; such derivatives have previously been analyzed genetically and designated "changes in state" by McClintock [McClintock, B. (1955) Carnegie Inst. Washington, Yearb. 54, 245-255]. All of the derivatives analyzed in the present study revert substantially later in development than the original insertion mutation and some show a very low frequency of reversion as well. All of the derivatives contain insertions at the same site as the parent bz-m13 allele. Deletions of 400-1300 base pairs were found in the dSpm elements in four of the six derivatives; the remaining derivatives could not be distinguished structurally from the original mutant allele. The results suggest that changes in the frequency and developmental timing of excision are attributable to alterations in the dSpm element. Furthermore, these data suggest that DNA sequences near the ends of the element are important for responding to the two transacting functions supplied by the transposition-competent Suppressor-mutator (Spm) element.

Base Sequence↗
PubMed1992

Maize mutants and variants altering developmental time and their heterochronic interactions.

It is useful to envision two fundamentally different ways by which the timing of plant development is regulated: developmental stage-transition mechanisms and time-to-flowering mechanisms. The existence of both mechanisms is indicated by the behavior of various mutants. Shoot stage transitions are defined by dominant mutants representing at least four different genes; each mutant retards transitions from juvenile shoot stages to more adult shoot stages. In addition, dominant leaf stage-transition mutants in at least seven different genes have similar phenotypes, but the leaf rather than the shoot is the focus (and at least two of these genes encode homeodomain proteins.) One mutant, Hairy sheath frayed 1-O (Hsf1-O) simultaneously affects shoot and leaf; this mutant's behavior initiated our interest in plant heterochronism. The second type of timekeeping involves time-to-flowering. As with most plant but not animal species, cultivars of the maize species vary greatly for the time-to-flowering quantitative trait: between 6 and 14 weeks is common. It is via the 'slipping time frames' interaction that takes place between stage-transition mutants and time-to-flowering genetic backgrounds that unexpected and radical phenotypes occur. We see a reservoir of previously unsuspected morphological possibilities among the few heterochronic genotypes we have constructed, possibilities that may mimic the sort of variation needed to fuel macroevolution without having to posit (as done by Goldschmidt) any special macromutational mechanisms.

Biological Evolution↗
PubMed1991

Disruption of developmental timing in the albino rat retina.

We have examined the spatial and temporal gradients of two developmental processes in albino and pigmented rats: outer plexiform layer (OPL) development, and rate of cell production. The OPL first appears as a thin, discontinuous break in the cytoblast layer that is frequently interrupted by the profiles of migrating neuro- and glioblasts. In both strains, this occurs in an area temporal to the optic disc that corresponds to the eventual site of peak ganglion cell density, but is not located along the line of nasotemporal division. The OPL is first evident at P5 in pigmented animals, but its appearance in albino animals is delayed approximately 30 hours, and its development appears to follow a flatter spatial gradient than in pigmented animals. In pigmented animals OPL formation is complete over most of the retina by P10, but in albino animals at this age it is yet to be completely formed at any retinal location. Reductions in mitotic activity are also first evident in temporal retina, but unlike OPL development, appear to follow the same temporal-spatial gradient in both strains. Reductions in temporal retina are obvious by P4, and mitotic activity has ceased altogether in midtemporal retina by P6 and throughout most remaining retinal regions by P8. Thus, the initial reduction of mitotic activity precedes the onset of OPL formation in both strains, but OPL development lags behind the reduction of mitotic activity to a greater extent in albino than in pigmented animals. Some aspects of differentiation within the inner nuclear layer (INL) were also examined. Just prior to the time of the onset of OPL formation, three distinct sublaminae are apparent in the INL. Cells in the innermost sublamina appear to be in an early stage of differentiation. Cells in the middle sublamina appear to be postmigratory, but have not yet begun to differentiate. Cells in the outermost sublamina have the appearance of migrating neuroblasts. At least some of these outer cells appear to migrate across the developing OPL to the outer nuclear layer, since the outermost sublamina becomes thinner and eventually disappears at the same time that the OPL becomes a continuous, uninterrupted plexiform layer. Cells of the middle sublamina apparently begin differentiation at about the time that this migration is complete. Although this sequence is the same in both albino and pigmented strains, its onset is delayed in albino animals by the same amount as the onset of OPL formation.(ABSTRACT TRUNCATED AT 400 WORDS)

Albinism↗
PubMed1987

Three ATPase activities have an abnormal developmental time course in trembler sciatic nerves.

Trembler mutant mice are affected by a peripheral neuropathy characterized by hypomyelination, demyelination, and Schwann cell proliferation. In adult mutants, supernumerary Schwann cells form membranous structures known as 'onion-bulb' formations. The activities of the Na+, K+-ATPase and of two ouabain-insensitive Mg2+-ATPases were investigated in sciatic nerves of young and adult mutants. The Na+, K+-ATPase activities were 92 and 76% of the control values in young and adult mutants, respectively. By immunoblot analysis, the alpha-subunit of the Na+, K+-ATPase had an identical apparent molecular weight in controls at both ages and in young mutants. In adult mutants, on the contrary, the alpha-subunit appeared smaller by about 2 kd, similar to that in kidney, indicating that the Na+, K+-ATPase was localized mainly on supernumerary Schwann cells. In addition, in the mutants, the developmental increase of both the mitochondrial and the nonmitochondrial Mg2+-ATPase was abnormally high. We suggest that the abnormal increase of the nonmitochondrial Mg2+-ATPase activity during development reflects an enrichment of that enzyme in 'onion-bulb' formations.

Animals↗
PubMed1988

An analysis of developmental timing in Blastocladiella emersonii sporulation.

We propose a model of time regulation for the expression of the Blastocladiella emersonii sporulation phenotypes based on new methods (Soll, 1986) which analyse the effect of temperature on the rate limiting processes, i.e., "timers" of certain events during development. By using reciprocal shift experiments (transferring sporulating cells from 22 to 27 degrees C and vice versa) we characterized the timers of the phenotypes: septate zoosporangium, papillate zoosporangium, cleavage zoosporangium, and empty zoosporangium, considering the number of the components, sensitivity, duration, and the mutual dependency of each limiting factor. The timers for the first three phenotypes started at zero time of sporulation induction and acted in parallel. The fourth phenotype, empty zoosporangium, has a timer which appears to act sequentially to that of the papillate zoosporangium. We also studied the effects of polyoxin D, calcofluor white, and congo red on sporulation. The first drug prevents the appearance of the septate zoosporangium and the other two prevent the expression of the papillate zoosporangium. In spite of the morphological blockage, the zoosporogenesis proceeds, resulting in the formation of normal zoospores. These results are interpreted as additional evidence for the parallel model of control proposed here.

Benzenesulfonates↗
PubMed1992

Cell lineages, developmental timing, and spatial pattern formation in embryos of free-living soil nematodes.

From soils of various origins we have isolated a number of nematode strains and cultured them on agar plates. We have analyzed their anatomy, reproduction, and particularly their pattern of embryogenesis. With respect to early cleavage we can define six different classes. The basic scheme of embryogenesis is similar in all strains but considerable differences were observed in detail. Embryogenesis is more than five times longer in the slowest strain than in the fastest. The following general correlation was found: The slower embryogenesis proceeds in a strain, the relatively earlier the cleavage of germline cells occurs. In the fastest strain the primordial germ cell P4 is present at the 24-cell stage, while in the slowest strain it is already generated in the 5-cell stage. We hypothesize that germline cleavages have to occur within a certain time limit to preserve germline quality. The typical reversal of cleavage polarity in the division of the germline cell P2 is absent in the slowest, on other grounds apparently more primitive strain. This results in an unusual spatial arrangement of cells transiently. However, prior to gastrulation as a consequence of compensatory cell migrations (which may indicate the necessity for cell interactions), the pattern becomes very similar to that in the other strains. We propose that a standard cellular configuration is required at the beginning of gastrulation to ensure normal further development. Early cell interactions might be necessary to achieve this standard pattern. In about half of the analyzed strains cellular structures can be marked with an antibody raised against germline-specific granules of Caenorhabditis elegans. Our results do not support the notion that the staining pattern for P granules is a useful indicator for phylogenetic relationship.

Animals↗