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At least 307 records · Page 17Linked to original sources
PubMed1984

Perinatal development of the lung in rat and spiny mouse: its relation to altricial and precocial timing of birth.

Rat and spiny mouse (Acomys cahirinus) are closely related murinoid species that represent altricial (rat) and precocial (spiny mouse) modes of development. The late intrauterine developmental stages of the spiny mouse therefore seem comparable to the early extrauterine developmental stages of the rat. To elucidate the question to what extent the development of the lung is related to the developmental timing of birth, we have studied some enzymes involved in the de novo synthesis of phosphatidylcholine. Of the enzymes studied, cholinephosphate cytidylyltransferase shows peaks in activity in the perinatal period (rat and spiny mouse) and at the beginning of the 3rd postnatal week (rat only). This enzyme fulfills the requirements for a developmental parameter best as changes in activity of this enzyme can be correlated with phases of cell proliferation and surface expansion in the lung of the rat. The single peak of cholinephosphate cytidylyltransferase activity in the spiny mouse as well as microscopical examination of the lung support the hypothesis that the processes of proliferation and surface expansion, which occur consecutively in the rat, develop concurrently in the spiny mouse.

Animals↗
PubMed2006

The effect of temperature on the development of Angiostrongylus cantonensis (Chen 1935) in Pomacea canaliculata (Lamarck 1822).

Angiostrongyliasis cantonensis, clinically presented as eosinophilic meningitis, is a snail-borne parasitic disease. We studied the effects of different temperatures on the larval development of Angiostrongylus cantonensis in the freshwater snail Pomacea canaliculata. Six groups of snails were infected and each group was cultured under different temperature conditions. At predefined intervals, four snails from each group were dissected to examine the larval development. The development-time curve of each group was drawn according to the fraction of third-stage larvae present. The developmental time was defined as the time needed until 50% of the first-stage larvae developed into third-stage larvae. A linear regression model was established based on the time (D; in days) and the corresponding temperature (T; in degrees Celsius): DT = 15.04 x D + 262.53. The threshold temperature for larval development was 15.04 degrees C and the thermal constant was 262.53 degree-days. These parameters could be helpful in estimating the number of parasite generations in a year and the impact of climate change on the distribution of A. cantonensis.

Angiostrongylus cantonensis↗
PubMed2005

Novel heterochronic functions of the Caenorhabditis elegans period-related protein LIN-42.

LIN-42, the Caenorhabditis elegans homolog of the Period (Per) family of circadian rhythm proteins, functions as a member of the heterochronic pathway, regulating temporal cell identities. We demonstrate that lin-42 acts broadly, timing developmental events in the gonad, vulva, and sex myoblasts, in addition to its well-established role in timing terminal differentiation of the hypodermis. In the vulva, sex myoblasts, and hypodermis, lin-42 activity prevents stage-specific cell division patterns from occurring too early. This general function of timing stage-appropriate cell division patterns is shared by the majority of heterochronic genes; their mutation temporally alters stage-specific division patterns. In contrast, lin-42 function in timing gonad morphogenesis is unique among the known heterochronic genes: inactivation of lin-42 causes the elongating gonad arms to reflex too early, a phenotype which implicates lin-42 in temporal regulation of cell migration. Three additional isoforms of lin-42 are identified that expand our view of the lin-42 locus and significantly extend the homology between LIN-42 and other PER family members. We show that, similar to PER proteins, LIN-42 has a dynamic expression pattern; its levels oscillate relative to the molts during postembryonic development. Transformation rescue studies indicate lin-42 is bipartite with respect to function. Intriguingly, the hallmark PAS domain is dispensable for LIN-42 function in transgenic animals.

Amino Acid Sequence↗
PubMed2000

Variation in performance on cry1Ab-transformed and nontransgenic rice varieties among populations of Scirpophaga incertulas (Lepidoptera: Pyralidae) from Luzon Island, Philippines.

We quantified variation in performance under greenhouse conditions among seven populations of Scirpophaga incertulas (Walker) from Luzon Island, Philippines, on three rice varieties: 'IR58' transformed with the cry1Ab gene from Bacillus thuringiensis Berliner, and nontransgenic IR58 and IR62. On IR62, S. incertutas performance did not differ among provinces for any of the 10 parameters measured, but there was a significant effect of town within province for one parameter, 20-d-old larval weight. Larval survival after 48 h on cy1Ab-transformed IR58 did not differ significantly among provinces, but did differ significantly among towns within a province. There was no geographic variation in larval survival after 48 h on control plants of IR58. Surviving insects from the cry1Ab-transformed IR58 were transferred to IR62 to complete development. There was no geographic variation in the percentage of insects completing development to adult emergence and the time required by the transferred female insects to complete development. However, there was variation among provinces in male developmental time. The absence of geographic variation on nontransgenic IR58 and the very limited variation on IR62 indicated that there was little variation in general vigor among the S. incertulas populations and thus that the variation in performance oil cry1Ab-transformed IR58 was probably attributable to differences in susceptibility to Cry1Ab.

Animals↗
PubMed2026

Origins and timing of somatic variants in the brain.

Somatic variants accumulate in human brain cells throughout the lifespan. Variant allele fraction has traditionally been used as a proxy for both the developmental timing of somatic variants and their functional effect, based on the assumption that earlier mutations are shared by larger cell populations and therefore have greater potential for severe phenotypes. However, recent discoveries challenge this simplified model. Variables such as developmental bottlenecks, lineage restriction, and cellular and molecular context play critical roles in shaping the distribution and functional impact of somatic variants in the brain. These insights support a shift toward a context-dependent framework for interpreting somatic mosaicism.

Humans↗
PubMed2003

The Arabidopsis heterochronic gene ZIPPY is an ARGONAUTE family member.

Plants progress through a temporal sequence of juvenile, adult, and reproductive phases, each marked by the expression of phase-specific traits. Here we show that loss-of-function mutations in ZIPPY (ZIP) cause the premature expression of adult vegetative traits but do not accelerate the onset of reproductive competence or flowering time. ZIP encodes ARGONAUTE7 (AGO7), one of ten members of the ARGONAUTE family in Arabidopsis. In addition to playing developmental roles, some ARGONAUTE family members are required for RNAi-like phenomena, such as posttranscriptional gene silencing. In contrast to Arabidopsis ARGONAUTE1, ZIP has no significant role in transgene silencing; its primary function is in the regulation of developmental timing.

Arabidopsis↗
PubMed2002

Extended in vitro culture of Microplitis croceipes teratocytes and secretion of TSP14 protein.

Teratocytes, cells which originate from the serosal membrane of some Braconidae and Scelionidae, can be found in the hemocoel of permissive hosts during part or all of the developmental time of the parasitoid larva. Teratocytes from Microplitis croceipes are known to secrete biologically active proteins, which contribute to developmental arrest and failure to pupate of Heliothis virescens larvae. One such protein, which has a molecular weight of approximately 14 kDa is called TSP14. The presence of parasitoid larvae is essential to maintain teratocytes under in vitro conditions with protein-free EX-CELL 400. The teratocyte viability was maintained in vitro for at least 12 days in the presence of larvae when medium was exchanged every three days. Western blots show that TSP14 was secreted during the entire period of exchanges. In the absence of parasitoid larvae, teratocyte viability was only 30% by day 6 and no TSP14 had been secreted. In the absence of parasitoid larvae, teratocytes maintained in vitro in EX-CELL 400 medium supplemented with 10% FBS remained viable for at least nine days and secreted TSP14 for at least six days. This suggests that parasitoid larval secretions are sufficient but not uniquely essential to maintain teratocyte viability. Parasitoid larvae maintained in the absence of teratocytes did not secrete TSP14 and their secretory products did not inhibit pupation of H. virescens larvae.

Journal Article↗
PubMed2003

MicroRNA pathways in flies and worms: growth, death, fat, stress, and timing.

Drosophila geneticists have uncovered roles for microRNAs in the coordination of cell proliferation and cell death during development, and in stress resistance and fat metabolism. In C. elegans, a homolog of the well-known fly developmental regulator hunchback acts downstream of the microRNAs lin-4 and let-7 in a pathway controlling developmental timing.

Animals↗
PubMed1998

Influence of form and quantity of selenium on the development and survival of an insect herbivore.

Even plants classified as 'nonaccumulators' can sequester concentrations of sodium selenate, sodium selenite, selenocystine and selenomethionine that can strongly influence insect development and survival. These forms of selenium (Se), tested in diet-incorporation bioassays, proved toxic to larvae of a generalist insect herbivore at relatively low levels. Sodium selenite was the most toxic form tested against Spodoptera exigua (Hübner), with an LC(50) of 9.14 microg g(-1) wet wt (21.11 microg g(-1) dry wt). Selenocystine was intermediate with an LC(50) of 15.2 microg g(-1) wet wt. The least toxic forms, sodium selenate and selenomethionine, had LC(50)s below 50 microg g(-1) dry wt, the upper level for tissues of plants classified as nonaccumulators. Ingestion of some forms of Se also affected growth and development. Increasing concentrations of sodium selenate and sodium selenite decreased pupal weight and added significantly to the time needed for development to the pupal and adult stages. The time required to complete the larval stage increased by over 25% and the time from egg to adult emergence was extended by 22% to nearly 30%. Selenocystine and selenomethionine did not significantly increase developmental times, even at concentrations that killed 90% or more of the test populations. Analyses of relative growth rate, relative growth index, and an analysis of covariance technique for measuring growth indicated that the form of Se affected growth rates, growth inhibition responses of the larvae, and toxicological effects. Thus, quantity and the form of Se accumulating in plants grown on Se-contaminated sites are likely to influence the population dynamics of insect herbivores. The implications of these results for the ecology of contaminated sites are discussed.

Journal Article↗
PubMed1997

Developmental changes in calcium current pharmacology and somatostatin inhibition in chick parasympathetic neurons.

Voltage-dependent calcium (Ca2+) currents were characterized and modulatory effects of somatostatin were measured in acutely dissociated chick ciliary ganglion neurons at embryonic stages 34, 37, and 40. This developmental time period coincides with the period of synapse formation between ciliary ganglion neurons and peripheral eye muscles. At all three developmental stages Ca2+ current could be blocked almost completely by combined application of omega-CgTX GVIA and nitrendipine. At young embryonic ages there was significant overlap in sensitivity, with approximately 75% of the current sensitive to either blocker applied independently. By stage 40, there was very little or no overlap in sensitivity, with approximately 75% of the current blocked by omega-CgTX GVIA (N-type) and 30% blocked by nitrendipine (L-type). These data are consistent with earlier findings that the pharmacology of acetylcholine release from ciliary ganglion nerve terminals changes during development from sensitivity to both dihydropyridines and omega-CgTX GVIA to selective sensitivity to omega-CgTX GVIA (Gray et al., 1992). Somatostatin reduced Ca2+ current by 50-60% at all three developmental stages. At early developmental stages somatostatin receptors coupled predominantly to the current that was sensitive to both omega-CgTX GVIA and nitrendipine. By stage 40, somatostatin primarily inhibited classically defined N-type current (selectively sensitive to omega-CgTX GVIA). Thus, somatostatin receptor coupling to Ca2+ channels persisted throughout development as Ca2+ current pharmacology changed.

Animals↗
PubMed1990

Times of origin of brachial sensory neurons are not correlated with neuronal phenotype.

The times of origin (birthdays) of sensory and motor neurons that innervate the triceps brachii muscles of the bullfrog (Rana catesbeiana) were determined to learn whether neurons innervating a specific target are generated at a particular developmental time. 3H-thymidine (3H-TdR) was made available continuously throughout a specific developmental period. All neurons that innervated the triceps muscle in juvenile frogs (identified by filling cells retrogradely with HRP) were generated prior to metamorphosis. Triceps motoneurons were all postmitotic by early limb bud stage V. Triceps sensory neurons were generated over a protracted period of larval development, from stage V through early pre-metamorphic stage XV. Most large triceps sensory neurons were generated before the majority of the small cells. However, there was considerable overlap in the times of origin of the two populations; both large and small cells were generated at all stages of sensory neurogenesis. There was thus no strict relationship between sensory soma size and birthdate. Late-generated sensory neurons tended to be located in clusters within ganglia, whereas HRP-filled triceps neurons were not. These 3H-labeled clusters may represent clones of neurons which would indicate that late stage neuroblasts give rise to neurons that supply different peripheral targets. The time course of triceps neuronal generation paralleled that of all other brachial sensory neurons implying that the time of last cell division does not in itself determine either the target a neuron will innervate or the sensory modality to which it will respond.

Animals↗
PubMed1984

The prepatent period and cercarial production of Schistosoma haematobium in Bulinus truncatus (Egyptian field strains) at different constant temperatures.

The developmental time of Schistosoma haematobium in Bulinus truncatus snails (field strains) was determined in the laboratory at different constant temperatures between 18 and 32 degrees C. The basic relationship between the length of the minimum prepatent period (y, in days) and the temperature (x, in degree C) is given by the hyperbolic formula y = 295/(x-15.3), 15.3 being the theoretical "developmental null point" and 295 the constant time-temperature product. The shortest prepatency was 17-19 days at 30, 31 and 32 degrees C; at 18 degrees C, cercarial development required at least 106-113 days. The maturation time frequently exceeded the possible minimum by several weeks. No schistosome matured in our experiments at 17 degrees or 33 degrees C. The cercarial release per snail at weekly exposures showed a maximum at 25 degrees C with a geometric mean of 109 cercariae (95% confidence limits 79-149), decreasing to 8 (2-30) at 18 degrees C and 62 (38-100) at 32 degrees C. The absolute maximum of cercariae shed by one snail during 5 h "stimulation" was 2,150 in a 25 degrees C batch, 48 at 18 degrees C and 529 at 32 degrees C. The epidemiological application, the prognosis of the transmission period and the estimation of the transmission potential in relation to climatic conditions are discussed.

Animals↗
PubMed1991

Differential development of insulin-like growth factor-I binding in the hypothalamus of hamster and rat.

We investigated the binding of [125]insulin-like growth factor-I ([125I]IGF-I) within the hamster suprachiasmatic nucleus (SCN) and median eminence (ME) by quantitative autoradiography and compared the development of binding to the same regions in the rat. Binding in the hamster SCN was to a single class of sites (estimated Kd = 6 x 10(-10) M). Binding in the ME was approx. 1.5-fold that of the SCN. Full displacement of binding from the SCN and ME of adults and neonates was achieved by 10(-8) M IGF-I, 10(-8) M IGF-II or 10(-6) M insulin. Binding within the hamster SCN was evident by E15, peaked between P5 and P7 and decreased to adult levels by P20 while binding in the rat SCN peaked perinatally and declined to adult levels by P6. Binding in the hamster ME was evident at P4, peaked by P12 and decreased to adult levels by P20 while binding in rat ME was present by P2, peaked by P7 and declined to adult levels by P9. These results demonstrate a different developmental time course for [125I]IGF-I binding between the SCN and ME of hamster and rat. The peak binding in the SCN of each species correlates with previously reported time courses for onset of retinohypothalamic innervation of the SCN. Further study of IGFs in these regions may help elucidate the developmental role of brain IGFs.

Animals↗
PubMed1996

Congenital hypothyroidism delays the formation and retards the growth of the mouse primary somatic sensory cortex (S1).

Intrinsic neural factors are thought to regulate the growth and formation of specific regions of the neocortex. To determine whether factors extrinsic to the brain are also involved in shaping the cytoarchitecture of the mammalian neocortex, we evaluated the effects of thyroid hormone (TH) on the formation and postnatal growth of the mouse S1 postero-medial barrel subfield (PMBSF). Congenital deficiency of TH, induced by propylthiouracil administration from day 12 of gestation, did not disrupt S1 specification, because no alterations in barrel number or configuration were observed in congenital hypothyroid mice. Barrel formation, however, was delayed by 3 days. In control mice, barrels were first seen at postnatal day (PN) 4, whereas in congenital hypothyroid mice they appeared at PN7. TH deficiency led to reduced adult brain, cortical, and S1 barrel dimensions. Barrel size, however, was relatively more affected than brain and cortical size. Our observations indicate, therefore, that TH does not participate in S1 specification, but in timing its formation. Our findings also indicate that TH regulates the relative size of the S1 barrel field by modulating the developmental timing of areal specification and brain growth.

Analysis of Variance↗
PubMed2007

Atypical epigenesis.

It is becoming increasingly clear that little in development is predetermined or permanently fixed. Rather, gene expression is activity dependent, and epigenesis is probabilistic. So, the study of genetic disorders needs to change from the still widely held view that developmental disorders can be accounted for in terms of intact versus impaired modules, to one which takes serious account of the fact that the infant cortex passes from an initial state of high regional interconnectivity to a subsequent state of increasing specialization and localization of function. With such early interconnectivity in mind, developmental neuroscientists must consider the possibility that an early deficit in one part of the brain may have subtle effects on other parts of the developing brain, even when scores fall 'in the normal range'. In studying developmental disorders, it is thus crucial to examine not only domains of clear-cut deficit, but also domains of behavioural proficiency. Atypical epigenesis may often involve a lack of specialization and localization of brain function over developmental time, even in cases of behavioural proficiency.

Brain↗
PubMed1992

Ontogeny of a biological clock in Drosophila melanogaster.

Drosophila melanogaster born and reared in constant darkness exhibit circadian locomotor activity rhythms as adults. However, the rhythms of the individual flies composing these populations are not synchronized with one another. This lack of synchrony is evident in populations of flies commencing development at the same time, indicating that a biological clock controlling circadian rhythmicity in Drosophila begins to function without a requirement for light and without a developmentally imparted phase. It is possible to synchronize the phases of rhythms produced by dark-reared flies with light treatments ending as early as the developmental transition from embryo to first-instar larva: Light treatments occurring at developmental times preceding hatching of the first-instar larva fail to synchronize adult locomotor activity rhythms, while treatments ending at completion of larval hatching entrain these rhythms. The synchronized rhythmic behavior of adult flies receiving such light treatments suggests that a clock controlling circadian rhythms may function continuously from the time of larval hatching to adulthood.

Age Factors↗
PubMed1998

Identification of heterochronic mutants in Caenorhabditis elegans. Temporal misexpression of a collagen::green fluorescent protein fusion gene.

The heterochronic genes lin-4, lin-14, lin-28, and lin-29 specify the timing of lateral hypodermal seam cell terminal differentiation in Caenorhabditis elegans. We devised a screen to identify additional genes involved in this developmental timing mechanism based on identification of mutants that exhibit temporal misexpression from the col-19 promoter, a downstream target of the heterochronic gene pathway. We fused the col-19 promoter to the green fluorescent protein gene (gfp) and demonstrated that hypodermal expression of the fusion gene is adult-specific in wild-type animals and temporally regulated by the heterochronic gene pathway. We generated a transgenic strain in which the col-19::gfp fusion construct is not expressed because of mutation of lin-4, which prevents seam cell terminal differentiation. We have identified and characterized 26 mutations that restore col-19::gfp expression in the lin-4 mutant background. Most of the mutations also restore other aspects of the seam cell terminal differentiation program that are defective in lin-4 mutant animals. Twelve mutations are alleles of three previously identified genes known to be required for proper timing of hypodermal terminal differentiation. Among these are four new alleles of lin-42, a heterochronic gene for which a single allele had been described previously. Two mutations define a new gene, lin-58. When separated from lin-4, the lin-58 mutations cause precocious seam cell terminal differentiation and thus define a new member of the heterochronic gene pathway.

Animals↗
PubMed1990

Diabetic ketoacidosis. Neurologic collapse during treatment followed by severe developmental morbidity.

Diabetic Ketoacidosis (DKA) remains the leading cause of death in children with type 1 diabetes mellitus. Complications occurring during DKA treatment include cerebral edema and neurologic collapse. Developmental outcomes following neurologic deterioration during DKA have varied from no sequelae to severe developmental disabilities. A total of three children developed neurologic deterioration during treatment of DKA at Buffalo Children's Hospital between 1984 and 1987. The authors treated aggressively for cerebral edema. Characteristic findings on the computed tomography (CT) scans and magnetic resonance imaging (MRI) of the brain included hemorrhagic infarctions of the thalami, basal ganglia and lentiform nuclei. The authors conducted developmental follow-up examinations between 1-1/2 - 3 years following recovery from DKA coma. Although they noted significant recoveries over time, developmental disabilities persisted. The clinical courses and neuroradiographic findings of these patients are compatible with sequelae of central brain stem herniation and cytotoxic brain injury. Continued efforts are needed in the prevention and early detection of clinically significant cerebral edema during treatment of DKA.

Brain Diseases↗