A quantitative analysis of the incidence of certain cytoplasmic structures in the ovum of the rat during cleavage

Summary The volumetric density of most cytoplasmic organelles in the segmenting ovum of the rat was determined by morphometric techniques described by Weibel, at the 1-, 2-, 4-, and 8-cell stages, and at the early and late blastocyst stages.During the course of cleavage, the volumetric density of mitochondria remained practically unchanged. The volumetric density of the Golgi complex was too small to permit assessment of the differences between the individual stages of development. Significant changes were found in both granular and agranular endoplasmic reticulum, secondary lysosomes, multivesicular bodies, lamellar structures and lipid droplets. Granular endoplasmic reticulum was first observed as late as the 8-cell ovum stage and its volumetric density increased further in the early and late blastocysts. The relative volume of agranular endoplasmic reticulum was highest in the 1-cell ovum and decreased during the course of cleavage. The same is true for multivesicular bodies. The volumetric density of secondary lysosomes increased during cleavage, reaching the highest values in the 8-cell ovum. Lamellar structures were the most voluminous part of the cytoplasm of the segmenting ovum at all stages. Their volumetric density, however, decreased during the course of cleavage. Lipid droplets occur in very small quantities in the 1- to 4-cell ova, but at later stages their volumetric density increased.Our findings underline the importance of acquiring quantitative information about changes in cell organelle populations for assessing morphological and functional relationships during the early stages of cleavage of the ovum.     

Influence of neuroendocrine shifts in the pubertal period on the working memory operation in adolescents

It was found that the volume of working memory in adolescents at the initial pubertal stages (II–III) was lower than in adults. Analysis of the event-related potentials (ERPs) in various cortical areas in adolescents when they compared two successive pictures revealed specific features of neurophysiological mechanisms of visual working memory at the early pubertal stages. As compared to adult subjects, the adolescents were characterized by longer latencies and higher amplitudes of the early components of the ERPs. Certain differences were revealed in the functional organization of working memory both at the stages of stimulus fixation and in its comparison with the current information.     

Lateral line placodes are induced during neurulation in the axolotl

In order to determine the time window for induction of lateral line placodes in the axolotl, we performed two series of heterotopic and isochronic transplantations from pigmented to albino embryos at different stages of embryogenesis and assessed the distribution of pigmented neuromasts in the hosts at later stages. First, ectoderm from the prospective placodal region was transplanted to the belly between early neurula and mid tailbud stages (stages 13-27). Whereas grafts from early neurulae typically differentiated only into epidermis, grafts from late neural fold stages on reliably resulted in differentiation of ectopic pigmented neuromasts. Second, belly ectoderm was transplanted to the prospective placodal region between early neurula and tailbud stages (stages 13-35). Normal lateral lines containing pigmented neuromasts formed in most embryos when grafts were performed prior to early tailbud stages (stage 24) but not when they were performed later. Our findings indicate that lateral line placodes, from which neuromasts originate, are already determined at late neural fold stages (first series of grafts) but are inducible until early tailbud stages (second series of grafts). A further series of heterochronic transplantations demonstrated that the decline of inducibility at mid tailbud stages is mainly due to the loss of ectodermal competence.     

Quantitative proteomic analyses reveal the dynamics of protein and amino acid accumulation during soybean seed development

Using high throughput tandem mass tag (TMT) based tagging technique, we identified 4172 proteins in three developmental stages: early, mid, and late seed filling. We mapped the identified proteins to metabolic pathways associated with seed filling. The elevated abundance of several kinases was observed from the early to mid-stages of seed filling, indicating that protein phosphorylation was a significant event during this period. The early to late seed filling stages were characterized by an increased abundance of proteins associated with the cell wall, oil, and vacuolar-related processes. Among the seed storage proteins, 7S (β-subunit) and 11S (Gy3, Gy4, Gy5) steadily increased in abundance during early to late stages of seed filling, whereas 2S albumin exhibited a decrease in abundance during the same period. An increased abundance of proteases, senescence-associated proteins, and oil synthesis proteins was observed from the mid to late seed filling stages. The mid to late stages of seed filling was also characterized by a lower abundance of transferases, transporters, Kunitz family trypsin, and protease inhibitors. Two enzymes associated with methionine synthesis exhibited lower abundance from early to late stages. This study unveiled several essential enzymes/proteins related to amino acid and protein synthesis and their accumulation during seed development. All data can be accessed through this link: https://massive.ucsd.edu/ProteoSAFe/dataset.jsp?task=38784ecbd0854bb3801afc0d89056f84 . (Accession MSV000087577)     

Spontaneous and evoked postsynaptic potentials in an embryonic neuromuscular system of the lobster,Homarus americanus

The embryonic motor innervation to the deep extensor abdominal muscles was studied in lobster eggs in which reflex twitches and tail flips could be evoked by mechanical stimulation in early embryos. Recordings from impaled fibers during early and later stages of embryonic development revealed spontaneous depolarizing and hyperpolarizing potentials, suggesting the presence of excitatory and inhibitory axons. Stimulation of the extensor motor innervation produced a variety of EPSPs and IPSPs. The depolarizing responses included small and large EPSPs and nonovershooting spikes. Although moderate facilitation of the EPSP was sometimes observed, defacilatation was observed in the majority of fibers of all stages. Spiking could not be evoked by motor axon stimulation in embryos of early stages. These findings indicate that from the outset the deep abdominal extensor neuromuscular system of the lobster is phasic in its response to nerve stimulation and is functional as part of the tail flip reflex at least six months before hatching.     

Water-soluble proteins in early amphibian embryos. III. Immunoelectrophoretic analysis of the antigenic changes in the ectoderm of the early gastrula and neural plate during development

20 water-soluble antigen have been identified with the help of rabbit antisera to extracts of the early gastrula ectoderm and neural plate in Rana temporaria. All of them were also found in the early blastula embryos and unfertilized eggs. The identified antigens are characterized by a definite embryospecificity. As the development proceeds, the concentration of these antigens in the embryonic tissues decreases until the complete disappearance of corresponding immunoelectrophoretic reactions. By this characteristic all antigens under study are subdivided into four groups: I--five antigens identified at the early developmental stages only (until hatching, stage 29); II--nine antigens present up to stages 33--35; III--three antigens followed up to stages 39--40 (well formed tadpole); IV--three antigens were found at all developmental stages under study up to stages 45--47. 11 out of 20 identified antigens have antigenic similarity with the proteins of blood serum of adult amphibians. Besides, the early gastrula ectoderm contains antigens similar with those of the brain of adult amphibians.     

Effect of assimilate supply on the growth of individual cucumber fruits

The effects of assimilate supply on the growth of individual fruits during different stages of fruit development were analysed in cucumber ( Cucumis sativus L. cv. Corona). The assimilate supply was varied by maintaining different numbers of fruits per plant or maintaining different irradiances. The growth rate of a cucumber fruit strongly increased with increasing assimilate supply, but its growing period was not noticeably affected. At a low assimilate supply both cell number and cell size were reduced. Increasing the assimilate supply at different stages of fruit development showed that the early development of a cucumber fruit was not crucial for setting its growth potential. A small number of cells, due to a low assimilate supply, during early fruit development, was to a great extent compensated by an increased expansion rate of individual cells. It is concluded that cell number is not an important determinant of fruit size in cucumber, although fruit size is often positively correlated with cell number. In the early stages of fruit development the effect of irradiance on the fruit growth rate depends on the presence of an earlier developed fruit because of dom-inance between fruits. In later stages of fruit development, a decrease in irradiance reduced the growth rate of all fruits relatively to the same extent independent of age or presence of other fruits.     

Effects of gall damage by the introduced biocontrol agent Epiblema strenuana (Lep., Tortricidae) on the weed Parthenium hysterophorus (Asteraceae)

Effects of gall damage by the introduced moth Epiblema strenuana on different growth stages of the weed Parthenium hysterophorus was evaluated in a field cage using potted plants with no competition and in naturally regenerated populations with intraspecific competition. Gall damage at early stages of plant growth reduced the plant height, main stem height, flower production, leaf production, and shoot and root biomass. All galled, potted plants with no competition produced flowers irrespective of the growth stage at which the plants were affected by galling, but lesser than in ungalled plants. Gall induction during early growth stages in field plants experiencing competition prevented 30% of the plants reaching flowering. However, 6% of the field plants escaped from gall damage, as their main stems were less vigorous to sustain the development of galls. Flower production per unit total plant biomass was lower in galled plants than in ungalled plants, and the reduction was more intense when gall damage was initiated at early stages of plant growth. In potted plants with no competition, the number of galls increased with the plant vigour, as the gall insects preferred more vigorous plants. But in field plants there were no relationship between gall abundance and plant vigour, as intraspecific competition enhanced the negative effects of galling by reducing the vigour of the weed.     

Origins of carbon sustaining the growth of whitefish Coregonus lavaretus early larval stages in Lake Annecy: insights from fatty-acid biomarkers

The hypothesis that diatom carbon (C) produced during the spring peak supported spring zooplankton production and, ultimately, the growth of Coregonus lavaretus early larval stages from March to May 2006 in Lake Annecy, France, was tested using gut content analyses and fatty acid biomarkers. Gut content results showed that C. lavaretus larvae from stages 1 to 4 preferentially fed on copepods with Daphnia sp. only a minor proportion of larval diet. The levels of diatom-marker fatty acids (C16:1n-7 and C20:5n-3) were high in Daphnia sp., but lower in both copepods and C. lavaretus larvae from stages 0 to 4. These results indicated that the spring diatom biomass was actually grazed by Daphnia sp., but, contrary to what was expected, the spring bloom was not the only C source supporting copepods secondary production and, consequently, the growth of C. lavaretus early larval stages. In contrast, levels of terrestrial fatty acid marker (C24:0) were low in Daphnia sp. but high in copepods and C. lavaretus larvae, indicating a significant contribution of terrestrial carbon to copepods and, ultimately, to the growth of C. lavaretus early larval stages.     

药用植物款冬花芽分化过程观察

实验以不同生长发育阶段的款冬花序芽突起为材料,通过制作石蜡切片,在显微镜下观察款冬花序芽分化各阶段的形态特征。结果表明:款冬花序芽从7月上旬开始花序(盘)分化至十月初小花胚珠分化完成,分化时期可分为分化前期、花盘形成期、花原基分化期、中央花(筒状)花瓣原基分化期、中央花雄蕊原基分化期、中央花雌蕊原基分化期、边缘花(舌状)花瓣原基分化期、边缘花雌蕊原基分化期、中央花花粉分化形成期、子房胚珠分化期共10个时期,阐明了款冬花序芽分化各时期与生长时间的关系。     

Effects of phosphorus and nitrogen on nodulation are seen already at the stage of early cortical cell divisions in Alnus incana

BACKGROUND AND AIMS: The present work aimed to study early stages of nodulation in a chronological sequence and to study phosphorus and nitrogen effects on early stages of nodulation in Alnus incana infected by Frankia. A method was developed to quantify early nodulation stages in intact root systems in the root hair-infected actinorhizal plant A. incana. Plant tissue responses were followed every 2 d until 14 d after inoculation. Cortical cell divisions were already seen 2 d after inoculation with Frankia. Cortical cell division areas, prenodules, nodule primordia and emerging nodules were quantified as host responses to infection. METHODS: Seedlings were grown in pouches and received different levels of phosphorus and nitrogen. Four levels of phosphorus (from 0.03 to 1 mM P) and two levels of nitrogen (0.71 and 6.45 mM N) were used to study P and N effects on these early stages of nodule development. KEY RESULTS: P at a medium concentration (0.1 mM) stimulated cell divisions in the cortex and a number of prenodules, nodule primordia and emerging nodules as compared with higher or lower P levels. A high N level inhibited early cell divisions in the cortex, and this was particularly evident when the length of cell division areas and presence of the nodulation stages were related to root length. CONCLUSIONS: Extended cortical cell division areas were found that have not been previously shown in A. incana. The results show that effects of P and N are already expressed at the stage when the first cortical cell divisions are induced by Frankia.     

Morphofunctional changes in the thymus of semisyngenous chimeras during the "graft versus host" response]

Activation of the enzymatic processes in the thymus cells was noted in the thymus gland at the early stages of the "transplantat-versus-host" reaction; the later stages were attended by inhibition of metabolic processes and reduction in number of immature and mature thymocytes in the cortical substance of the thymus. Besides, the cortical substance displayed accumulation of mesenchymal macrophages rich in lysosomal enzymes, particularly in the subcapsular layer where small foci of destruction formed at the late stages of the reaction.     

Histones of spermatogenous cells in the house cricket

Histones were isolated from testis of the house cricket and analyzed by electrophoresis on polyacrylamide gels containing urea and acetic acid. Testes of two different nymphal instars and of adults were examined. The testes contained gonial and meiotic stages in the younger nymphs analyzed, and these same stages plus early spermatids in the older nymphs. At both nymphal instars, testis histone displayed the same five major fractions that are found in somatic nuclei of the cricket; the only unusual feature noted in nymph testis was a high abundance of phosphorylated F1. Adult testis has the same histone fractions as nymph testis and has two new fractions in addition. SDS electrophoresis also shows the presence of two more histones in adult testis than in nymph testis. — The unusual testis histones appear to accumulate during the nuclear elongation stages of spermiogenesis. The occurrence of these stages in adult testis is correlated with the presence of the extra histones. Nuclei of adult testis were separated into fractions enriched for early, mid, and late stages by velocity sedimentation at unit gravity. The unusual histones predominate in the fractions enriched for late spermiogenic stages. Both of the new histones appear to occur in the same stages of spermiogenesis, and display linked accumulation. Eventually they make up at least seventy percent of the histone complement.     

不同环境下水稻谷粒重发育的杂种优势和遗传相关性分析

选用9个不同类型的水稻品种(系),按双列杂交设计(6×5)配成两套亲本和F12个世代的遗传材料,采用数量性状的加性、显性遗传模型、发育遗传模型比较分析了水稻谷粒重发育的杂种优势和遗传相关性。结果表明,早季在谷粒充实前期(1～12d)群体平均优势较小,中后期(13～28d)正向优势趋于明显,在谷粒充实的全过程均表现较小的负向群体超亲优势;晚季则在谷粒充实前中期(1～18d)表现正向群体平均优势。后期(19～28d)优势不明显,在谷粒充实前期(1～12d)表现正向群体超亲优势,之后转为明显的负向群体超亲优势,表明晚季谷粒发育的杂种优势表现较之早季更有利于提高籽粒充实质量,不同发育时期谷粒重之间以及与最终谷粒重之间的遗传相关分析表明,早季以显性相关为主,晚季以加性相关为主,随着发育进程的推进,相关趋于密切。     

Technic for Photographing Early Cleavage Stages of the Hen's Egg

Altho photographs have been secured of early cleavage stages in the pigeon's egg, no photographs of corresponding stages of development of the hen's egg have been published. Satisfactory photographs of early cleavage stages of the hen's egg have been difficult to obtain in the past because of the indistinctness of the furrows and the lack of contrast between them and the remainder of the blastodisc. The indistinctness of the cleavage furrows in the hen's egg as compared with those of the pigeon's egg was recognized by Patterson (1910) who, after having studied both types of eggs, states (p. 109): “The lack of a furrow is the cause of the indistinctness of the early cells. In this respect, the early cleavages of the hen's egg differ greatly from those of the pigeon's egg, for in the latter their clearness is such as to permit photographing the living cells, while in the former photographs are impossible, except in a few cases”.     

The effect of thidiazuron on the yield of wheat grown with varying nutrient supply

The effect of the synthetic cytokinin thidiazuron on the yield of wheat growing under conditions of varying nutrient supply was investigated. Applications of thidiazuron during the early growth stages of wheat promoted tillering but reduced yield. Applications of thidiazuron during flag leaf senescence had little effect on yield. However, the yield of plants was increased at all levels of nutrient supply by treating plants with paclobutrazol during the early growth stages followed by thidiazuron during flag leaf senescence. Yield increases were greatest in moderately nutrient stressed plants, but were accompanied by a reduction in the N concentration of the grain. Possible reasons for the interaction between thidiazuron and paclobutrazol in increasing the yield of wheat are discussed.     

Centrifugal elutriation of porcine oocytes isolated from the ovaries of newborn piglets.

A two step enzymatic procedure for the isolation of ovarian follicles and oocytes at early stages of development from the ovaries of newborn piglets was devised. The isolated oocytes were then separated from the overwhelming majority of the ovarian somatic cells using a centrifugal elutriation system. Twenty to thirty thousand oocytes were routinely collected after elutriation of the cell suspension derived from a pair of ovaries. In the enriched fraction the ratio of oocyte:somatic cells was between 1:1 and 1:3. The validation of the method as an efficient procedure for the isolation of a large, viable, and highly enriched population of oocytes at early stages of development was provided by uptake studies carried out after each step of the isolation and separation technique and by a comparative analysis of the pattern of structural proteins of the enriched fraction and of fully grown porcine oocytes. The results confirmed that the isolated cells were actually oocytes at early stages of development and that they were viable throughout the entire procedure.