Search

Start Over Coverage 199-204

2. Host-finding behaviour of Cotylurus flabelliformis (Trematoda: Strigeidae) cercariae for snail hosts

Creator:
Campbell, Ronald A.
Format:
print
Type:
model:internalpart and TEXT
Subject:
Cotylurus, Strigeidae, Lymnaea stagnalis, cercariae, and chemoattraction
Language:
English
Description:
Cercariae of Cotylurus flabelliformis (Faust, 1917) were individually tested in 6 experiments for evidence of chemoattraction to snail hosts, host-speeificity, and rate of dispersal. Five species of snails were tested: Lymnaea stagnalis appressa Say, 1821, Stagnatola eludes (Say, 1821), Physella gyrina (Say, 1821), Planorbella trivnlvis (Say, 1817), and Oxyloma retusum (Lea, 1834). The data substantiate that cercariae of C. flabelliformis have a chemo-positive attraction to undetermined diffusable substances from snails, show host-specificity, and do not attack the snail that produced them. Cercarial response time was significantly influenced by cercarial age (post-emergence), and duration of presence of snails. Newly emerged cercariae were most consistently chemo-positive to L. stagnalis and quickly located all snail species except the unnatural host O. retusum. Tests of 121 cercariae proved statistically significant in showing preferences for snail hosts. Cercarial dispersal experiments showed that C. flabelliformis cercariae can disperse rapidly but few located and penetrated lab-reared S. eludes at distances up to 1.2 m. The results are consistent with other studies which indicate that chemical gradients are used by cercariae to locate slow moving hosts and that cercariae must come into close proximity of snails before attraction occurs. The significance of these observations to the distribution of C. flabelliformis in the molluscan population is discussed.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

3. Influence of latent ''asymptomatic'' toxoplasmosis on body weight of pregnant women

Creator:
Flegr, Jaroslav, Hrdá, Štěpánka, and Kodym, Petr
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
parasite, Toxoplasma, latent toxoplasmosis, pathology, permutation test, and gravidity
Language:
English
Description:
The latent toxoplasmosis is usually considered to be asymptomatic, however, this paradigm has never been rigorously tested. Here we searched for symptoms of deterioration of physical health (decrease of weight) in infected people by analysis of clinical records of 758 women tested for toxoplasmosis in the 16th week of gravidity. Toxoplasma-positive women have a lower body weight in the 16th week of gravidity (p = 0.02) than Toxoplasma-negative women. Moreover, a negative correlation between weight and the duration of toxoplasmosis was found in a subset of 174 Toxoplasma-positive women (p = 0.04), suggesting that slow and cumulative effects of latent toxoplasmosis, rather than a transient effect of acute toxoplasmosis, are responsible for the decreased weight of infected subjects. Longer duration of gravidity estimated from the date of last menstruation in the set of Toxoplasma-positive women in the 16th week of gravidity estimated with ultrasonography (p = 0.04) suggests a possibility of retarded foetal growth in Toxoplasma-positive women. The prevalence of latent toxoplasmosis is extremely high. Therefore, even its mild symptoms such as the decreased body weight in Toxoplasma-positive pregnant women might in fact indicate an unrecognized serious public health problem.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

4. Life cycle of Ascocotyle (Phagicola) angeloi (Digenea: Heterophyidae) in the Neotropical Region

Creator:
Ostrowski de Núňez, Margarita
Format:
print
Type:
model:internalpart and TEXT
Subject:
Ascocotyle (Phagicola) angeloi, Heterophyidae, Littoridina castellanosae, lifecycle, and Neotropical Region
Language:
English
Description:
Stages of the life cycle of Ascocotyle (Phagicola) angeloi Travassos, 1928 were experimentally obtained, from cercariae from naturally infected Littoridina castellanosae (Gaillard) collected in artificial ponds in the Zoological Garden of Buenos Aires. Metacercariac were found encysted mainly in muscles and ovary, but also in other parts of the body of naturally and experimentally infected fish Jenynsia lineata (Jenyns) (Atheriniformes: Jenynsidae). Adults were obtained experimentally from chicks and mice. Ascocotyle (Phagicola) angeloi, rcdescribed in the present paper, is distinguished from other species of the subgenus by the two rows of oral spines, each with 14 spines. The characteristics of the studied cercaria corresponds to those of the subgenus Phagicola.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

5. Physiological basis of the difference in net photosynthetic rate of leaves between two maize strains

Creator:
Jiang, Hua and Xu, Da-Quan
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
chlorophyll content, intercellular CO2 concentration, leaf area, photochemical efficiency, photosystem 2, plant height, quantum yield, stomatal concuctance, and Zea mays
Language:
Multiple languages
Description:
Significant differences in net photosynthetic rate (PN) of leaves between two maize (Zea mays L.) strains (Shuang 105 and 40×44) grown in the field were observed. At several growth stages, PN of 40×44 was higher than that of Shuang 105 (from 10.3 to 32.5 %). Moreover, the strain 40×44 had a higher plant height, larger leaf area, lower chlorophyll content, and higher photochemical efficiency of photosystem 2 (PS2) (Fv/Fm and ΔF/Fm') than strain Shuang 105. Shuang 105, which showed lower PN, had lower stomatal conductances (gs) but slightly higher intercellular CO2 concentrations (Ci) than those of 40×44. Hence the differences in PN between the two strains did not result from the difference in gs, but probably from that in light reaction system. and Hua Jiang, Da-Quan Xu.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

6. Recent Progress in the Understanding and Applications of Superhard Nanocomposites nc-TmN/a-Si3 N4

Creator:
Veprek, Stan and Veprek-Heijman, M. G. J.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
precision mechanics, nanotechnology, přesná mechanika, and nanotechnologie
Language:
Czech
Description:
We briefly summarize the recent progress in the understanding of the preparation, properties, origin of hardness enhancement and industrial applications of the superhard nanocomposites nc-TmN/a-Si3 N4 , that consist of 3-4 nm small nanocrystals of a hard transition metal nitride joined together by a strong, about 1 monolayer thin layer of silicon nitride. These unique materials can reach hardness far above 50 GPa. They are prepared by means of plasma chemical or physical vapor deposition as thin coatings and applied on tools for machining, such as turning, drilling, milling, forming and stamping. Compared to conventional hard coatings, the nanocomposites significantly increase the productivity of a large number of machining operations. and Stručně shrnujeme současný rozvoj v přípravě, vlastnostech a původu zvýšené tvrdosti a průmyslovém využití supertvrdých nanokompozitů nc-TmN/a- Si3N4, které jsou složeny z nanokrystalů tvrdého tranzitního nitridu kovu o velikosti 3-4 nm spojeného s pevnou vrstvou nitridu křemíku. Takový unikátní materiál dosahuje tvrdosti nad 40 GPa. Jsou vytvářeny pomocí plazmaticko chemického nebo fyzikálně vakuového nanášení v podobě tenkých vrstev a jsou využívány jako strojní nástroje pro soustružení, vrtání, frézování, tvarování a ražení. Nanokompozity v porovnání s konvenčním povlakováním zvyšují produktivitu řady strojních obrábění.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public