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At least 667 records · Page 37Linked to original sources
PubMed2001

Susceptibility of the different developmental stages of the asexual (schizogonic) erythrocyte cycle of Plasmodium chabaudi chabaudi to hyperimmune serum, immunoglobulin (Ig)G1, IgG2a and F(ab')2 fragments.

The mechanisms by which antibodies interfere with Plasmodium growth are still under debate. Characterizing the asexual erythrocyte stages susceptible to antibodies from hyperimmune individuals is therefore a relevant contribution to vaccine research. In this study, using a virulent and synchronous murine malaria parasite, Plasmodium chabaudi chabaudi AJ, we have shown that trophozoites and circulating schizonts are not the main targets for antibodies from hyperimmune serum. In drug-cured mice challenged with a high inoculum of ring-infected erythrocytes, parasitemias do not decline until the moment of erythrocyte rupture, suggesting that effector mechanisms operate immediately prior to reinvasion. Confirming these findings, treatment of primary-infected mice with hyperimmune serum inhibited the generation of new ring forms, but did not alter the numbers of schizont-infected erythrocytes, despite the fact that these cells were recognized by immunoglobulin (Ig)G antibodies. When these mice were treated with IgG1 or IgG2a purified from hyperimmune serum, both subclasses limited reinvasion, but IgG2a showed a stronger protective activity. The fact that Fc digestion decreases but does not abrogate protection suggests that both Fc-dependent and independent mechanisms participate in this process. Treatment with cobra venom factor did not interfere with the antibody-mediated protection, ruling out the participation of the complement system in both lysis and phagocytosis of merozoites or infected erythrocytes. Therefore, in mice suffering from P. c. chabaudi AJ malaria, merozoite neutralization seems to be a major mechanism of protection conferred by hyperimmune serum antibodies. However, FcgammaR-mediated interactions, or other mechanisms not yet defined, may also contribute to inhibit erythrocyte reinvasion.

Animals↗
PubMed2002

Fertilization in Arabidopsis thaliana wild type: developmental stages and time course.

We describe some previously uncharacterised stages of fertilization in Arabidopsis thaliana and provide for the first time a precise time course of the fertilization process. We hand-pollinated wild type pistils with wild type pollen (Columbia ecotype), fixed them at various times after pollination, and analysed 600 embryo sacs using Confocal Laser Scanning Microscopy. Degeneration of one of the synergid cells starts at 5 Hours After Pollination (HAP). Polarity of the egg changes rapidly after this synergid degeneration. Karyogamy is then detected by the presence of two nucleoli of different diameters in both the egg and central cell nuclei, 7-8 HAP. Within the next hour, first nuclear division takes place in the fertilized central cell and two nucleoli can then be seen transiently in each nucleus produced. In a second set of experiments, we hand-pollinated wild type pistils with pollen from a transgenic promLAT52::EGFP line that expresses EGFP in its pollen vegetative cell. Release of the pollen tube contents into the synergid cell could be detected in living material. We show that the timing of synergid degeneration and pollen tube release correlate well, suggesting that either the synergid cell degenerates at the time of pollen tube discharge or very shortly before it. These observations and protocols constitute an important basis for the further phenotypic analysis of mutants affected in fertilization.

Arabidopsis↗
PubMed1999

Isolation, characterization and immunolocalization of phosphorylcholine-substituted glycolipids in developmental stages of Caenorhabditis elegans.

Caenorhabditis elegans displays three neutral glycosphingolipids with structural homology to glycosphingolipids from the porcine nematode parasite, Ascaris suum. The present findings extend the degree of structural conservation between the two nematode species to glycosphingolipids with a phosphodiester substitution. Using a combination of hydrofluoric acid pretreatment, immunochemical characterization and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, three zwitterionic, phosphorylcholine-substituted glycosphingolipids could be identified in the neutral glycolipid fraction of C. elegans. The components were isolated as their zwitterionic, phosphorylcholine-substituted, pyridylaminated oligosaccharides by HPLC. Structural analysis was performed using hydrofluoric acid treatment, partial acid hydrolysis, methylation analysis, gas chromatography-mass spectrometry, cleavage with exoglycosidases and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Their chemical structures are proposed as: component Nz1, GalNAc(beta1-4)[phosphorylcholine]GlcNAc(beta1-3)Man(beta1-4)Glc-cera mide; component Nz2, Gal(alpha1-3)GalNAc(beta1-4)[phosphorylcholine]-GlcNAc(beta1-3)Man(be ta1-4)Glc-ceramide; and component Nz3, Gal(beta1-3)- Gal(alpha1-3)GalNAc(beta1-4)[phosphorylcholine]GlcNAc(beta1-3)Man(bet a1-4)Glc-ceramide. The oligosaccharide core is characteristic of the biosynthetic arthro-carbohydrate series of protostomial glycosphingolipids. The ceramide moiety was specified by a d17 : 1 sphingoid-base with iso-branching and anteiso-branching, and 2-hydroxy, saturated fatty acids as represented by docosanoic and tetracosanoic acids. Analysis of the spatial and temporal expression of the phosphorylcholine epitope, during embryonic and postembryonic development, showed it to be localized predominantly in seam cells and basement membranes, respectively. In early embryonic ontogenesis the phosphorylcholine epitope was only lipid bound, while in late embryonic and postembryonic development this epitope was both lipid bound and protein bound.

Animals↗
PubMed1999

Highly reproducible spatiotemporal patterns of mammalian embryonic movements at the developmental stage of the earliest spontaneous motility.

The principles underlying the variations in patterns of mammalian embryonic movements have not been established. In an attempt to clarify the mechanism that is responsible for the variations in motor patterns, we carried out a precise quantitative spatiotemporal analysis of movements in mouse embryos, using a transplacental perfusion method for the in vitro maintenance of live mammalian embryos. Episodes of spontaneous movements at the inception of motility, at embryonic day 12.5, occurred once every few minutes, lasted for several seconds and consisted of successive movements of body regions, the spatiotemporal patterns of which varied from episode to episode. By analysing and categorizing the patterns of these movements, we found that embryonic movements follow relatively few restricted patterns with respect to the order of the movements of body regions. A further analysis of episodes at high spatiotemporal resolution revealed that most of the episodes in a major category could be classified into two distinct subtypes. Each of these subtypes had its own highly reproducible spatiotemporal patterns of movement. Overall, these results show that early embryonic movements follow relatively few rather stereotyped patterns, and random local fluctuations have little effect on such movement patterns. The appearance of one pattern out of several rather stereotyped patterns may be the main cause of apparent variations in patterns of early embryonic movements. The stereotyped patterns may represent important orderly characteristics of spontaneous embryonic activities that may be involved in the development of orderly structures and functions in higher animals.

Animals↗
PubMed2000

Human retinal astroglia. A comparative study of adult and the 18 month postnatal developmental stage.

The immunohistochemical location of glial fibrillary acidic protein (GFAP) was used to study the state of maturation of retinal astrocytes from an 18-mo-old infant and to compare it with the situation in the adult. Infant astrocytes showed intense GFAP immunoreactivity in the perikarya and possessed spindle-like enlargements in their processes, while in the adult immunoreactivity in the perikarya was scarce and the spindle-like enlargements were not evident. Two types of astrocyte were observed in adult and child retinas: elongated and star-shaped. In the adult, the star-shaped type tend to be more stylised and to have longer processes than in the infant. In the infant, numerous astrocyte cell bodies were observed over vessels, while in the adult these were scarce. In the infant, the star-shaped astrocytes made up a honeycomb plexus, but this was not fully developed. These results suggest that at 18 mo of postnatal development the retinal astrocytes are still increasing and growing into the astroglial structure found in adults.

Adult↗
PubMed1998

Expression and localization of brain ankyrin isoforms and related proteins during early developmental stages of rat nervous system.

Expression and localization of two isoforms of brain ankyrin, 440- and 220-kDa ankyrinB, were studied in the developing nervous system of the rat fetus. The 440-kDa ankyrinB appeared on as early as embryonic day 13, and its level increased progressively toward the day of birth, which was similar to the expression pattern of growth-associated protein (GAP)-43, a well-established axonal protein. On the other hand, 220-kDa ankyrinB was expressed at a low level but constitutively throughout the latter prenatal period and was a major isoform even before embryonic day 14. Whereas the localization of 440-kDa ankyrinB was essentially confined to the axons, judging from the similarity with that of GAP-43, 220-kDa ankyrinB showed a rather general distribution in neural tissue. The localization of L1, known as an ankyrinB-binding protein, was similar to that of 440-kDa ankyrinB in the brain tissue, whereas it was similar to that of 220-kDa ankyrinB in cultured neurons, suggesting that the interaction of L1 with brain ankyrins in neurons is affected by their environment.

Animals↗
PubMed1997

[Immunofluorescence reaction of antibodies directed against the intestinal epithelium of Schistosoma mansoni. VI. Immunolocalization of a carbohydrate epitope at different developmental stages].

In the course of previous works, we described an IgM monoclonal antibody directed to a carbohydrate epitope located on the gut epithelium surface of the Schistosoma mansoni adult worm. We provided evidence that this epitope was present in all stages of the parasite and was particularly abundant in eggs. The current work was performed in order to specify the epitope localisation, at each stage, by immunohistochemical techniques. The epitope appears to be located on the peripheral membranes of the adult worm, while it is produced by the alive miracidium in the eggs located in the tissues and subsequently spread out inside the periovular granuloma. Moreover, in adult worms, the observed structure presents itself as a soluble form in organic solvents; on the other hand, in eggs, the epitope was essentially found made of an hydrosoluble substance. These datas can explain why, in experimentally infected mice, the epitope is mainly determined in urines at the sixth week of infestation, when eggs are settled down in the tissues. Besides, the inhibition of the monoclonal antibody fixation by a pentose which contains the Lewis X antigen, painted out that the carbohydrate structure recognised by the monoclonal antibody could be the Lewis X antigen or a very closed structure.

Animals↗
PubMed1997

In vivo gene transfer into the blastoderm of early developmental stage of chicken.

An attempt was made to improve gene transfer into chick embryos in order to produce transgenic chickens. The beta-actin-lacZ/MiwZ, a marker gene in transfection reagent, was injected into the blastodisc of either unincubated fertilized eggs (stage X) or eggs induced from the shell gland by treating the hens intravenously with oxytocin or arginine vasotocin (stages IV-VI). All the manipulated embryos were incubated to reach stage XIV, the period at which primordial germ cells (PGCs) migrate from the germinal crescent to the gonadal anlage via the blood stream. MiwZ was detected in the embryos, extraembryonic tissues and blood by the histochemical staining method of beta-galactosidase. The MiwZ DNA was detected in 57% (127/221) of the survival embryos and in 9% (12/127) of the embryonic tissues. The expression was observed mosaically in the epidermis, heart and neural tube. The PGCs in the blood collected from the vitelline artery or dorsal aorta also showed a positive histochemical staining. However, the expression of MiwZ using the soft shelled eggs was more intense in the extraembryonic tissues, although it did not emerge in the embryos. Thus, it is possible to introduce an exogenous gene into the embryonic tissues using incubated fertilized eggs without sacrificing the hens. This technique for successive genetic operations should facilitate the production of transgenic chickens.

Actins↗
PubMed2000

[Spondylolysis in the developmental stage: diagnostic contribution of MRI].

PURPOSE: To assess the value of MR imaging in demonstrating ongoing spondylolysis in adolescents. METHODS: MRI was performed in 9 juvenile patients (3 female, 6 male aged 8-16 years; mean 12.5 y) with pain during hyperextension. In 6 patients a CT scan and in 5 a plain film was available. RESULTS: In all patients bone marrow edema was found in the pars interarticularis and the pedicle, which was bilateral in 4 patients. In 7/9 cases the L5 vertebra was affected, in 2/9 cases spondylolysis was found in L4. In 3 cases the edema reached the middle third of the vertebral body and a tumor was suspected. In all CT scans a bilateral incomplete or complete cleft in the pars inter-articularis was found. In 4/6 CT-scans a sclerosis was seen in the area of the bone marrow edema. Only in 1/5 plain films was there a suspicion for a spondylolysis, four examinations were completely normal. CONCLUSIONS: To eliminate underlying causal conditions of spondylolysis and to install specific therapy, early diagnosis is mandatory. MR imaging should be the first and only imaging modality in young patients with low back pain during and after exercise and pain with hyperextension. Bone scans and CT scans should be avoided due to irradiation, plain films usually do not reveal pathological findings in developing sponylolysis.

Adolescent↗
PubMed2004

Changes in soluble carbohydrates and related enzymes induced by low temperature during early developmental stages of quinoa (Chenopodium quinoa) seedlings.

Low temperature represents one of the principal limitations in species distribution and crop productivity. Responses to chilling include the accumulation of simple carbohydrates and changes in enzymes involved in their metabolism. Soluble carbohydrate levels and invertase, sucrose synthase (SS), sucrose-6-phosphate synthase (SPS) and alpha-amylase activities were analysed in cotyledons and embryonic axes of quinoa seedlings grown at 5 degrees C and 25 degrees C in the dark. Significant differences in enzyme activities and carbohydrate levels were observed. Sucrose content in cotyledons was found to be similar in both treatments, while in embryonic axes there were differences. Invertase activity was the most sensitive to temperature in both organs; however, SS and SPS activities appear to be less stress-sensitive. Results suggest that 1) metabolism in germinating perispermic seeds would be different from endospermic seeds, 2) sucrose futile cycles would be operating in cotyledons, but not in embryonic axes of quinoa seedlings under our experimental conditions, 3) low temperature might induce different regulatory mechanisms on invertase, SS and SPS enzymes in both cotyledons and embryonic axes of quinoa seedlings, and 4) low temperature rather than water uptake would be mainly responsible for the changes observed in carbohydrate and related enzyme activities.

Acclimatization↗
PubMed2005

Toxicity assessment of the antifouling compound zinc pyrithione using early developmental stages of the ascidian Ciona intestinalis.

This study investigated the toxicity of zinc pyrithione (Zpt) on the early stages of development of the ascidian Ciona intestinalis. Larval morphological abnormalities were studied after the exposure of C. intestinalis embryos at different stages of development. The median effective concentrations (EC50) ranged from 226-590 nM. The larval settlement stage was the most sensitive to Zpt. Toxic effects of Zpt on larval settlement were detected at 9 nM (EC10). The inhibition of C. intestinalis embryonic development was also used to study the loss of toxicity in Zpt solutions exposed to direct sunlight and laboratory UV light. The results showed that the toxicity of Zpt solutions decreased but did not disappear after 4 h exposure to direct sunlight (EC50 = 484 nM) or UV light (EC50 = 453 nM), compared to control Zpt solutions prepared in dark conditions. On the basis of the present data, predicted no effect concentrations of Zpt to C. intestinalis larvae are lower than predicted environmental concentrations of Zpt in certain polluted areas and therefore, may pose a risk to C. intestinalis populations.

Animals↗