Stage- and cell-specific expression of cyclic adenosine 3',5'-monophosphate-dependent protein kinases in rat seminiferous epithelium.

Expression of mRNAs in the rat testis encoding cyclic AMP (cAMP)-dependent protein kinases (PKAs) was studied. A microdissection method was used to isolate 10 pools of seminiferous tubules representing various stages of the cycle of the seminiferous epithelium in combination with Northern blots and in situ hybridization. The results showed a differential expression of the four isoforms of the regulatory subunits (PKA-R) at various stages of the cycle. RI alpha mRNA was detected at approximately the same levels at all stages while expression of RI beta mRNA was low at stages XIII-III, started to increase at stages IV-V, and reached a maximum at stages VIII-XI. The level of RII alpha mRNA was low at stages II-VI, increased markedly at stage VIIa,b, and reached maximal levels at stages VIIc,d and VIII, followed by a reduced expression at later stages, RII beta mRNA levels increased significantly at stage VI with maximal levels at stages VII and VIII. In situ hybridization of sections from the adult rat testis revealed RI alpha mRNA in the layers of pachytene spermatocytes and round spermatids of all stages. RI beta mRNA was detected over late pachytene spermatocytes and round spermatids of stages VII-XIII. RII alpha mRNA was seen in the layers of round spermatids of stages VII-VIII and elongating spermatids of later stages while RII beta mRNA was detected only in the round spermatid region of stages VII-VIII and in some tubules of stages I-VI. These data show that mRNAs encoding PKA-R are expressed in a stage-specific manner in differentiating male germ cells with different patterns of expression for each subunit; this suggests specific roles for these protein kinases at different times of spermatogenesis.     

Analysing growth and development of plants jointly using developmental growth stages

Background and Aims Plant growth, the increase of organ dimensions over time, and development, the change in plant structure, are often studied as two separate processes. However, there is structural and functional evidence that these two processes are strongly related. The aim of this study was to investigate the co-ordination between growth and development using mango trees, which have well-defined developmental stages.Methods Developmental stages, determined in an expert way, and organ sizes, determined from objective measurements, were collected during the vegetative growth and flowering phases of two cultivars of mango, Mangifera indica. For a given cultivar and growth unit type (either vegetative or flowering), a multistage model based on absolute growth rate sequences deduced from the measurements was first built, and then growth stages deduced from the model were compared with developmental stages.Key Results Strong matches were obtained between growth stages and developmental stages, leading to a consistent definition of integrative developmental growth stages. The growth stages highlighted growth asynchronisms between two topologically connected organs, namely the vegetative axis and its leaves.Conclusions Integrative developmental growth stages emphasize that developmental stages are closely related to organ growth rates. The results are discussed in terms of the possible physiological processes underlying these stages, including plant hydraulics, biomechanics and carbohydrate partitioning.     

Integrating function across marine life cycles

Complex life cycles involve a set of discrete stages that candiffer dramatically in form and function. Transitions betweendifferent stages vary in nature and magnitude; likewise, thedegree of autonomy among stages enabled by these transitionscan vary as well. Because the selective value of traits is likelyto shift over ontogeny, the degree of autonomy among stagesis important for understanding how processes at one life-historystage alter the conditions for performance and selection atothers. We pose 3 questions that help to define a research focuson processes that integrate function across life cycles. First,to what extent do particular transitions between life-historystages allow those stages to function as autonomous units? Weidentify the roles that stages play in the life history, typesof transitions between stages, and 3 forces (structural, genetic/epigenetic,and experiential) that can contribute to integration among stages.Second, what are the potential implications of integration acrosslife cycles for assumptions and predictions of life-historytheory? We provide 3 examples where theory has traditionallyfocused on processes acting within stages in isolation fromothers. Third, what are the long-term consequences of carryoverof experience from one life cycle stage to the next? We distinguish3 scenarios: persistence (effects of prior experience persistthrough subsequent stages), amplification (effects persist andare magnified at subsequent stages), and compensation (effectsare compensated for and diminish at subsequent stages). We usethese scenarios to differentiate between effects of a carryoverof state and carryover into subsequent processes. The symposiumintroduced by our discussion is meant to highlight how discretestages can be functionally coupled, such that life cycle evolutionbecomes a more highly integrated response to selection thancan be deduced from the study of individual stages.     

Vertebral Abnormalities Following Heat Shock in Xenopus Embryos

Xenopus embryos were heat-shocked at several stages of development and vertebral abnormalities were examined by means of in situ staining. A high incidence of vertebral abnormalities was evident in larvae treated at the neurula stages (stages 15 and 20) and at the tailbud stages (stages 32 and 35). Heat shock at the neurula stages led to malformed vertebrae and their fusion following an altered arrangement of the arcualia. Heat shock at the tailbud stages induced an asymmetric arrangement of the sacrum and a change in the number of vertebrae, but the arrangement of the arcualia was not affected. Early events of the development of the vertebral column are discussed in relation to somitogenesis.     

Babesia bigemina sexual stages are induced in vitro and are specifically recognized by antibodies in the midgut of infected Boophilus microplus ticks

Babesia bigemina, a causative agent of bovine babesiosis, is transmitted from one bovine to another only by infected ticks. The life cycle of B. bigemina includes a sexual phase in the tick host; however, molecules from sexual stages of any Babesia species have not been characterized. This is the first report of the induction of sexual stages of any Babesia species in vitro, free of tick antigens. Intraerythrocytic parasites were cultured in vitro for 20h using an induction medium. Extraerythrocytic parasites were first seen 3h post induction; elongated stages with long projections appeared at 6h post induction and by 9h they paired and fused to form larger stages. Round zygotes appeared 20h post induction. Moreover, by using Percoll gradients, sexual stages were purified free of contaminating intraerythrocytic stages. Purified parasites were used to generate polyclonal antibodies, which specifically bound to antigens expressed in sexual stages induced in vitro, but not to antigens expressed in intraerythrocytic stages. Importantly, these antibodies specifically identified sexual stages from midguts of female Boophilus microplus ticks fed on infected cattle.     

响叶杨大、小孢子母细胞减数分裂进程及其对应关系

以响叶杨(P opu lus ad enop od a M ax im.)为材料,就大、小孢子母细胞减数分裂进程及其对应关系进行了研究.结果表明:响叶杨大、小孢子母细胞减数分裂进程与花芽外部形态存在一定的相关性,可从花芽外部形态变化估计大、小孢子母细胞减数分裂进程;响叶杨大、小孢子母细胞减数分裂进程亦存在一定的时序性相关,当雄配子发育至单核靠边期时,大孢子母细胞减数分裂进入粗线期;通过相同培养条件下小孢子发育进程的观察,可以实现响叶杨大孢子母细胞减数分裂进程的即时判别.     

Crucial stages of embryogenesis of R. arvalis: Part 1. Linear measurements of embryonic structures

Investigations of individual variability have allowed us to reveal the crucial (= nodal) stages in embryogenesis of the moor frog (Rana arvalis Nills.). These crucial stages are: the late gastrula stage (stages 18-20), the hatching stages (stages 32-33) and, apparently, early metamorphosis (stage 39). Moreover, we have found that each embryonic structure passes through its specific crucial stages. For example, stage 34 is crucial for the trait "tail width" but is internodal for all other embryonic traits. At this stage, larva passes from an attached to a free-swimming life style. We also found considerable differences between the different frog populations in the the level of developmental variability. These differences were associated with internodal developmental stages.     

HORMONES CONTROLLING COLLAGEN SYNTHESIS DURING METAMORPHOSIS IN THE THIGH BONE OF THE TADPOLE OF RANA CATESBEIANA

The rate of ¹⁴C-proline incorporation into collagen in the thigh bone of the Rana catesbeiana tadpole was determined in vitro. Intraperitoneal injection of bovine prolactin caused an increase in the rate of collagen synthesis during the premetamorphic stages (stages 12–16) and the early metamorphic stage (stage 18), but it exerted no effect on collagen synthesis in the metamorphic stages (stages 20–25). On the other hand, injection of growth hormone stimulated the rate of collagen synthesis in the metamorphic stages and caused a slight increase in the premetamorphic stages. When a tadpole in the early premetamorphic stages (stages 12–14) was kept in 5 × 10₋₈ M thyroxine solution for several days, the rate of collagen synthesis became higher than that in the bone of the control animal. The rate of collagen synthesis was not enhanced by prolactin in the thyroxine-treated tadpole, but was stimulated by growth hormone, even when the thyroxine-treated animal remained in the premetamorphic stages. With the treatment of the tadpole by thyroxine, prolactin-sensitivity seems to be reduced, and growth hormone-sensitivity becomes apparent.     

Spatial patterns and interspecific associations of three canopy species at different life stages in a subtropical forest, China

Spatial patterns of species at different life stages are an important aspect for understanding causal mechanisms that facilitate species co-existence.Using Ripley's univariate L(t) and bivariate L12(t) functions,we analyzed the spatial patterns and interspecific associations of three canopy species at different life history stages in a 20-ha subtropical forest plot in Dinghushan Nature Reserve.Based on diameter at breast height (DBH),four life stages were distinguished.Castanopsis chinensis and Schima superba showed a unimodal DBH distribution.Engelhardtia roxburghiana showed a bimodal curve.L(t) function analysis showed significantly aggregated distributions of all three species at later life stages and random distribution at early life stages at some scales.From the analysis of L12(t) function,the results showed the positive association was a dominant pattern for most species pairs at most scales but the intensity of association decreases with the increase of life stages.Juveniles of the three species had no negative intra- and interspecific associations with the older life stages.Only premature trees were suppressed by overmature trees at some scales.Considering these results,we found three canopy-dominant species that lacked regeneration.There was no direct competition occurring between understorey individuals.Young trees can grow well under conspecific species with two other species.Longevity and lack of regeneration led to a large number of trees stored in mature and overmature stages,therefore,intra-and inter-competition can be strong at later life stages.     

Morphogenesis of extraembryonic membranes and placentation in Mabuya mabouya (Squamata, Scincidae)

Topological and histological analyses of Mabuya mabouya embryos at different developmental stages showed an extraembryonic membrane sequence as follows: a bilaminar omphalopleure and progressive mesodermal expansion around the whole yolk sac at gastrula stages; mesodermal split and formation of an exocoelom in the entire embryonic chamber at neurula stages; beginning of the expansion of the allantois into the exocoelom to form a chorioallantoic membrane at pharyngula stages; complete extension of the allantois into the exocoelom between limb-bud to preparturition stages. Thus, a placental sequence could be enumerated: bilaminar yolk sac placenta; chorioplacenta; allantoplacenta. All placentas are highly specialized for nutrient absorption from early developmental stages. The bistratified extraembryonic ectoderm possesses an external layer with cuboidal cells and a microvillar surface around the whole yolk sac, which absorbs uterine secretions during development of the bilaminar yolk sac placenta and chorioplacenta. During gastrulation, with mesodermal expansion a dorsal absorptive plaque forms above the embryo and several smaller absorptive plaques develop antimesometrially. Both structures are similar histologically and are active in histotrophic transfer from gastrula stages until the end of development. The dorsal absorptive plaque will constitute the placentome and paraplacentome during allantoplacental development. At late gastrula-early neurula stages some absorptive plaques form chorionic concavities or chorionic bags that are penetrated by a long uterine fold and seem to have a specialized histotrophic and/or metabolic role. The extraembryonic mesoderm does not ingress into the yolk sac and neither an isolated yolk mass nor a yolk cleft are formed. This derived pattern of development may be related to the drastic reduction of the egg size and obligatory placentotrophy from early developmental stages. Our results show new specialized placentotrophic structures and a novel arrangement of extraembryonic membrane morphogenesis for Squamata.     

Crucial stages of embryogenesis of <Emphasis Type="Italic">R. arvalis</Emphasis>: Part 1. Linear measurements of embryonic structures

Investigations of individual variability have allowed us to reveal the crucial (=nodal) stages in embryogenesis of the moor frog (Rana arvalis Nills.). These crucial stages are: the late gastrula stage (stages 18–20), the hatching stages (stages 32–33) and, apparently, early metamorphosis (stage 39). Moreover, we have found that each embryonic structure passes through its specific crucial stages. For example, stage 34 is crucial for the trait “tail width” but is internodal for all other embryonic traits. At this stage, larva passes from an attached to a free-swimming life style. We also found considerable differences between the different frog populations in the the level of developmental variability. These differences were associated with internodal developmental stages.     

长毛对虾卵子皮层反应的研究

Morphology of the cortical reaction in the eggs of Penaeus penicillatus was studied with the light microscopy,scanning electron microscopy　and transmission electron microscopy. The cortical reaction is divided into four stages. These stages are unreacted stages, early stages, corona stages and dissipation stage. The cortical rods were released and formed a jelly coating around the surface of the egg. The jelly coating remained until the first cleavage had finished. In the end, the hatching membrane appeared around the egg. It is believed that these cortical reaction are responsible for the prevention of polyspermy by both a chemical and physical block and that also may establish a microenvironment inside a touch chorionic membrane for the developing embryo.     

Observations on an Intranuclear Microsporidian in Lymphoblasts from Farmed Atlantic Halibut Larvae (Hippoglossus hippoglossus L.)

ABSTRACT. An intranuclear microsporidian was observed in lymphoblasts from the kidney of farmed Atlantic halibut larvae ( Hippoglossus hippoglossus ). In addition to spores, intranuclear pre-spore stages were observed. Uninucleated stages with a slight thickening of the cell membrane were the most simple developmental stages observed. Multinucleated developmental stages contain electron-lucent vesicles and electron-dense discs. The spores are ovoid and measure 2.9 × 1.2 μm (mean). Sporophorous vesicles, diplokarya and mitochondria were not observed in any of the developmental stages. The developmental stages observed are similar to those of the family Enterocytozoonidae, genus Enterocytozoon. However, there are several differences between the present species and E. bieneusi from enterocytes in man. The relationship to the other species in the genus, E. salmonis can only be determined when all the developmental stages of the species from Atlantic halibut are identified.     

长毛对虾卵子皮层反应的研究

Morphology of the cortical reaction in the eggs of Penaeus penicillatus was studied with the light microscopy,scanning electron microscopy　and transmission electron microscopy. The cortical reaction is divided into four stages. These stages are unreacted stages, early stages, corona stages and dissipation stage. The cortical rods were released and formed a jelly coating around the surface of the egg. The jelly coating remained until the first cleavage had finished. In the end, the hatching membrane appeared around the egg. It is believed that these cortical reaction are responsible for the prevention of polyspermy by both a chemical and physical block and that also may establish a microenvironment inside a touch chorionic membrane for the developing embryo.     

Cell junctions in early embryos of squid (Loligo pealei)

Summary Squid embryos examined by freeze-fracture and thin-section electron microscopy exhibit identifiable gap junctions during mid-cleavage stages (stages 7–8), and junctional complexes composed of adherent appositions, elaborate septate junctions and gap junctions at slightly later stages (stages 12–13). During germinal layer establishment (stages 12–13) cytoplasmic bridges frequently link the embryonic cells. The presence of gap junctions in cleavagestage embryos provides the morphological substrate for a demonstrated pathway of direct cell-cell communication that is modifiable by experimental treatments and may be physiologically regulatable. The existence of septate junctions and adherent contacts at later stages suggests that some functional specialization, perhaps the establishment of a strongly joined framework of cells at the surface of the embryo, accompanies the formation of germinal layers.     

Radiosensitivity curve of different stages of spermatogenesis of Anopheles atroparvus (Diptera:Nematocera)]

In order to obtain a dose-hatchability curve for irradiated spermatogenetic stages of Anopheles atroparvus, we have irradiated with the same dose "4500 r" young fourth larval stages, old fourth larval stages, nymphae and adult males. Those different stages represent different phases of spermatogenesis. The peak of radiosensitivity for embryonic mortality, was found in spermatids, lowest appeared in spermatogonies.     

The ultrastructure of gametogenesis of cryptosporidium baileyi (eimeriorina; cryptosporidiidae) in the respiratory tract of broiler chickens (Gallus domesticus).

The ultrastructural features of sexual development of Cryptosporidium baileyi in the respiratory tract of experimentally infected broiler chickens were studied using transmission electron microscopy. Sexual stages of C. baileyi were seen attached to the tracheal epithelium and free in the tracheal lumen. These stages included intracellular type III merozoite-like stages, microgamonts, microgametes, macrogamonts, thin-walled oocysts, and thick-walled oocysts. These stages were developmentally similar to those observed for other Cryptosporidium species. All of the above stages were observed during each study day. Thin-walled oocysts, microgamonts, and microgametes were seen less frequently than other sexual stages. Microgamonts, macrogamonts, and oocysts attached to the epithelium were all contained in a host cell membrane or within a parasitophorous vacuole. Thin-walled oocysts of C. baileyi were observed for the first time on an ultrastructural level in the respiratory tract of chickens.