Search results for "Animal Structures"
showing 10 items of 876 documents
Formation of Epidermal and Dermal Merkel Cells During Human Fetal Skin Development
1986
The origin of Merkel cells is still a matter of debate, specifically the question of whether they are derived from epithelial cells of the epidermis or from immigrated neural crest cells. As an argument for the latter hypothesis the occurrence of dermal, nerve-associated Merkel cells in human fetal skin has often been mentioned. Therefore, we analyzed the distribution of Merkel cells in epidermis and dermis of plantar skin of human embryos and fetuses, ranging in gestational age between 7 and 17 weeks. Merkel cells were identified by immunocytochemistry on frozen sections using antibodies against simple epithelium-type cytokeratins and by electron microscopy. In the 17-week-old fetus, 17% o…
Water-Dependent Blending of Pectin Films: The Mechanics of Conjoined Biopolymers
2020
Biodegradable pectin polymers have been recommended for a variety of biomedical applications, ranging from the delivery of oral drugs to the repair of injured visceral organs. A promising approach to regulate pectin biostability is the blending of pectin films. To investigate the development of conjoined films, we examined the physical properties of high-methoxyl pectin polymer-polymer (homopolymer) interactions at the adhesive interface. Pectin polymers were tested in glass phase (10&ndash
Predation of perch on vendace larvae: diet composition in an oligotrophic lake and digestion time of the larvae
2007
The diet of perch Perca fluviatilis was studied to reveal possible predation on vendace Coregonus albula larvae in an oligotrophic lake. Perch diet changed with the size of the fish: small perch ate mainly zooplankton and the diet shifted more to benthic invertebrates and fishes in larger perch. There were also annual and spatial differences in the diet, probably reflecting differences in the availability of prey animals. Perch predation on vendace larvae was only observed in the area with high availability of the larvae. The result suggested strengthened predation when the density of the larvae increases. According to bioenergetics modelling, the perch population increased natural mortalit…
Ejection of a Polymer Chain from a Nanopore: Theory and Computer Experiment
2010
We consider the ejection dynamics of a flexible polymer chain out of confined environment. This situation arises in different physical contexts, including a flexible synthetic polymer partially confined in a nanopore and a viral genome partially ejected from its capsid. We describe the chain release from confinement both analytically and by means of dynamic Monte Carlo simulation. We find two distinct regimes of ejection dynamics depending on whether the chain is fully or partially confined. Partially confined chains are ejected from a pore of length L and diameter D after a typical time τ ∝ L2D5/3, regardless of their contour length N. The process is driven by a constant force f ≈ 5kBT/D a…
Mycotoxin Incidence in Some Fish Products: QuEChERS Methodology and Liquid Chromatography Linear Ion Trap Tandem Mass Spectrometry Approach
2019
The inclusion of vegetal raw materials in feed for fish farming has increased the risk of mycotoxin occurrence in feed, as well as in edible tissues from fish fed with contaminated feed, due to the carry-over to muscle portions. Therefore, the objective of this study was to evaluate the occurrence of 15 mycotoxins in processed fish products, which are commonly consumed, such as smoked salmon and trout, different types of sushi, and gula substitutes. A QuEChERS method was employed to perform the mycotoxin extraction from fish samples. For mycotoxin identification and quantitation, the selected technique was the liquid chromatography-tandem mass spectrometry linear ion trap (LC-MS/MS-LIT). Sm…
Development of nucleoside phosphotransferase activity in the cerebral hemispheres of embryonal and adult chick.
1981
In the cerebral hemispheres of the chick embryo, the level of nucleoside phosphotransferase activity is much higher than that of thymidine kinase and it increases progressively during development up to the adult stage. Therefore nucleoside phosphotransferase is not coupled with DNA synthesis.
Funktion der Spermien in inkompatiblen Kreuzungen der StechmückeCulex pipiens L.
1972
After irradiating males of the incompatible crossC. pipiens ‘Hamburg’ ♀♀×C. pipiens ‘Paris’ ♂♂ with X-ray doses between 1 kR and 40 kR, it could be shown that in this cross the sperm has only the function of activating the egg. All the hybrid embryos develop from the haploid female pronucleus.
Hsp60 and Hsp10 as antitumour molecular agents
2007
The molecular chaperones Hsp60 and Hsp10 are, according to recent reports, involved in cancer development and progression. We, for instance, have found that their expression varies with distinctive patterns in different malignancies: they are overexpressed in colorectal, exocervical and prostate carcinogenesis, and colorectal cancer progression, but they are downregulated during bronchial carcinogenesis. There is also evidence showing that Hsp60 and Hsp10 can be used as therapeutic agents, for example in rheumatoid arthritis. In view of these findings we want now to call attention to the potential of Hsp60 and Hsp10 in cancer therapy.
Crystal cell pattern modification in a melanotic tumor strain of Drosophila melanogaster.
1988
3rd instar larvae of the melanotic tumor tu-pb strain of Drosophila melanogaster hold a lower number of free-circulating crystal cells in their hemolymph than the wild type ones. This pattern could result from an abnormal retention of mature crystal cells in the hematopoietic organs, as the strong hemocyte melanization inside the lymph glands of heat-treated tu-pb larvae seems to demonstrate. Melanotic tumor formation and modification of the crystal cell pattern may be related.
A light and electron microscope study of spherical structures in the test cells of an ascidianCiona intestinalis L.
1984
Spherical structures in the test cells that surround the embryos of the ascidianCiona intestinalis L. (Tunicata, phylum Chordata) were studied by both light and electron microscope. Our data support the view that these structures are microorganism-like cells living in symbiosis with the test cells. Their possible role is discussed.