| 1. |
- Elofsson, Rolf, et al.
(författare)
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The anostracan rhabdom and the basement membrane. An ultrastructural study of the Artemia compound eye (Crustacea)
- 1975
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Ingår i: Acta Zoologica. - : Wiley. - 0001-7272 .- 1463-6395. ; 56, s. 141-153
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Tidskriftsartikel (refereegranskat)abstract
- The ommatidia of the compound eyes of Artemia salina L. are normally composed of four crystalline cone cells containing glycogen. The cells are enveloped by two so-called “cellules épidermiques juxta-cristallines”. There are also six pigmented retinula cells, all contributing to the rhabdom.A peculiar feature of the Artemia crystalline cone cells is that their elongated parts, the so-called cone cell roots, widen and flatten proximally, forming interdigitating “endfeet”. The basement membrane thus consists of a cellular portion combined with the basal lamina.The main mass of the rhabdom of the Artemia eye is built up by five retinula cells, two contributing a smaller part. The microvilli are oriented in four directions, two being orthogonal. The sixth cell contributes on two small portions to the rhabdom in the distalmost and a more proximal position. The rest of it runs axon-like outside the omnatidium. Where the sixth cell wedges in, the direction of the microvilli is changed and has no orthogonal pattern.Two rhabdom types of compound eyes are distinguished: the decapod or banded or layered rhabdom: and the anostracan rhabdom with continuous rhabdomeres.
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| 2. |
- Nilsson, Dan-E, et al.
(författare)
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The compound eye of Leptodora kindtii (Cladocera): : An adaptation to planctonic life.
- 1983
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Ingår i: Cell and Tissue Research. - 1432-0878. ; 230, s. 40-410
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Tidskriftsartikel (refereegranskat)abstract
- Each of the approximately 500 ommatidia in the compound eye of the cladoceran crustacean Leptodora kindtii has a crystalline cone consisting of five cells. Five retinula cells are also present, one of which contributes to the distal 1–2 μm of the rhabdom only; the other four retinula cells form a continuous rhabdom. Throughout the rhabdom its cross section displays two separate halves with the axis of the microvilli in one half perpendicular to that in the other (orthogonal pattern). Interferometric analysis of the refractive index of the crystalline cone revealed an inhomogeneous system with one distal and one proximal gradient. The gradient system was found to exclude rays entering from adjacent facets, thus maintaining the optical isolation. Consequently, these optics replace distal screening pigment, which is absent in the eye. The long and unscreened crystalline cones give rise to an almost transparent eye in conformity with the overall transparency of this planktonic animal.The morphological characteristics of the eye of this species deviate from other cladoceran eyes, but the optical design closely resembles that of some pelagic marine amphipod crustaceans.
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| 3. |
- Nässel, Dick, et al.
(författare)
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Neuronal connectivity patterns in the compound eyes of Artemia salina and Daphnia magna (Crustacea: Branchiopoda)
- 1978
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Ingår i: Cell and Tissue Research. - 1432-0878. ; 190, s. 435-457
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Tidskriftsartikel (refereegranskat)abstract
- The neuronal types and patterns in the visual system of the species Artemia salina and Daphina magna have been studied with the Golgi method and electron microscopy. The lamina contains five classes of neurons: photoreceptor axons, monopolar, centrifugal, tangential and amacrine neurons. The terminals of the receptor axons are distributed in two (A. salina) or three (D. magna) layers. The dilated terminals have an extensive and wide array of fine branches. One axon from each ommatidium bypasses the lamina and terminates in the medulla in A. salina. A. salina has four types of monopolar neurons, two of which are stratified, whereas in D. magna only two types are found, one of which is bistratified. Tangential T-neurons connect the lamina with the protocerebrum. D. magna has in addition one tangential T-neuron connecting both the lamina and the medulla with the protocerebrum. In both species monopolar-type centrifugal neurons connect the medulla and the lamina, whereas that of A. salina has a wide laminar distribution. Both species also have amacrine cells in the lamina. The medulla contains, besides those shared with the lamina, transmedullary neurons (two types in A. salina), amacrine cells and neurons originating in the protocerebrum.“Cartridge”-type synaptic compartments are lacking in the investigated species, although a periodic arrangement is discernible in the distal portion of the lamina of A. salina. The receptors from three types of specialized contacts in Artemia, one of which involves a dyad. D. magna has only one-to-one synapses. Neurosecretory fibres are absent in A. salina.
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| 4. |
- Odselius, Rolf, et al.
(författare)
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The basement membrane of the insect and crustacean compound eye: definition, fine structure and comparative morphology
- 1981
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Ingår i: Cell and Tissue Research. - 1432-0878. ; 216, s. 201-214
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Tidskriftsartikel (refereegranskat)abstract
- The basement membrane of the compound eye of four insect species and three crustacean species was investigated employing electron microscopy. The basement membrane consists of an extracellular (basal lamina) and a cellular portion, the latter being composed of the flattened terminal extensions of cone cells and accessory pigment cells in insects and distal pigment cells in crustaceans. Other cells can also contribute to the basement membrane. It is thus a complex structure in all well-developed compound eyes. The cellular contributions vary in different species and were found to correlate to specific taxonomic units.
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| 5. |
- Jansson, Hans-Börje, et al.
(författare)
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Growth and capture activities of nematophagous fungi in soil visualized by low temperature scanning electron microscopy
- 2000
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Ingår i: Mycologia. - 0027-5514. ; 92:1, s. 10-15
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Tidskriftsartikel (refereegranskat)abstract
- Growth and capture activities of nematophagous fungi in soil were observed using the low temperature scanning electron microscopy technique. The advantages of this sample preparation technique, compared with conventional scanning electron microscopy, are that it does not involve chemical fixation and dehydration of the sample and, therefore, gives a more accurate view of organ isms in soil. Growth, sporulation, trap formation, capture and digestion of nematodes were observed in soil using the nematode-trapping fungi Arthrobotrys superba, A. dactyloides and A. oligospora CT, and the endoparasite Drechmeria coniospora.
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| 6. |
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| 7. |
- Olsson, Lars-Fride, et al.
(författare)
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In vitro formation of nanocrystalline carbonate apatite - A structural and morphological analogue of atherosclerotic plaques
- 2007
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Ingår i: European Journal of Inorganic Chemistry. - : Wiley. - 1434-1948 .- 1099-1948 .- 1099-0682. ; :26, s. 4123-4127
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Tidskriftsartikel (refereegranskat)abstract
- The in vitro formation of carbonate apatite in solutions with ion concentrations comparable to those in human serum was studied. The composition and morphology of the resulting apatite precipitate displayed a hierarchical assembly of elongated plate-shaped nanocrystals of carbonate apatite analogous to previously characterized bioapatites formed in The main conclusion is that so-called bioapatites may form in vitro and that precipitation inhibitors most likely are essential for the prevention of spontaneous calcification at normal human serum ion concentrations.
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| 8. |
- Sandin, Karin, et al.
(författare)
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The observation of nano-crystalline calcium phosphate precipitate in a simple supersaturated inorganic blood serum model - composition and morphology
- 2009
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Ingår i: Journal of Applied Biomaterials and Biomechanics. - 1722-6899 .- 1724-6024. ; 7:1, s. 13-22
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Tidskriftsartikel (refereegranskat)abstract
- Aim. Calcium phosphate deposition in blood vessels is correlated to increased mortality risk. In this study, the formation of solid calcium phosphate in an in vitro solution mimicking the inorganic part of blood serum was studied. Methods. The precipitates formed were analyzed using several experimental techniques, including infrared spectroscopy, Raman spectroscopy, X-ray energy dispersive spectroscopy, chemical analysis of combustion gases, thermogravimetric analysis, as well as transmission electron microscopy and scanning electron microscopy. Results. The results indicate a microscopically amorphous but nano-crystalline material with an overall apatite structure. A plausible stoichiometry was determined to Ca-5(PO4)(3)(HCO3)center dot 4H(2)O with an estimated solubility constant of 6.10(-39) (mol/L)(9). Bicarbonate in the water solution was shown to be essential for the precipitation, giving implications for in vitro studies. Conclusions. The calcium phosphate formed in this study shows many similarities to pathological calcium phosphates regarding composition, morphology and crystallinity.
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| 9. |
- Shahana, Shahida, 1973-
(författare)
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Cell Contacts and Airway Epithelial Damage in Asthma
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Airway epithelial damage is commonly found in asthma patients. Epithelial damage was investigated with special reference to contacts between epithelial cells.Eosinophils, common in allergic asthma, secrete cationic proteins, particularly major basic protein (MBP). The effect of poly-L-arginine, an analogue of MBP, on airway epithelial cells was investigated. Poly-L-arginine induced membrane damage, resulting in increased permeability, loss of cell-cell contracts (tight junctions and desmosomes) and generalized cell damage.Adhesion molecules on airway epithelial cells may be important in recruiting leukocytes. Interferon (IFN)-γ increased intracellular adhesion molecule-1 expression in airway epithelial cell lines. A combination of interleukin-4 and IFN-γ opened the tight junctions.Epithelial damage in asthma was studied at the ultrastructural level in bronchial biopsies from patients with atopic or non-atopic asthma, and healthy controls. Epithelial damage was extensive in both asthma groups. In basal and columnar cells, relative desmosome length was reduced by 30-40%. In columnar cells, half-desmosomes were noticed. Changes tended to be more extensive in atopic asthma, but there was no significant difference between the two groups. Reduced desmosomal contact may be important in the epithelial shedding observed in asthma. The contact area between columnar cells and basal lamina is relatively small in the human airway. Attachment of columnar cells to the basal lamina occurs indirectly, via desmosomal attachment to basal cells. Direct attachment of columnar cells to the basal lamina is weakened in asthmatics.Nasal polyposis is a chronic inflammatory disease often associated with asthma. An ultrastructural study showed that epithelial damage of columnar cells is more pronounced in allergic patients. The length of columnar cell desmosomes was significantly reduced in asthmatics vs. non-asthmatics, and in allergics vs. non-allergics.Cell contacts in airway epithelium in asthmatics are weakened, which may be an intrinsic feature or due to the presence of eosinophils producing toxic proteins.
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| 10. |
- Åkesson, Kristina, et al.
(författare)
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Energy-dispersive X-ray microanalysis of the bone mineral content in human trabecular bone: a comparison with ICPES and neutron activation analysis
- 1994
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Ingår i: Calcified Tissue International. - 1432-0827. ; 55:3, s. 236-239
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Tidskriftsartikel (refereegranskat)abstract
- To evaluate the accuracy of bone mineral composition determination by electron microprobe analysis (EDX) the measurements have been compared to instrumental neutron activation analysis (INAA) and chemical analysis (ICPES). Bone specimens from five femoral heads were used. The trabecular content of calcium (Ca) and phosphorus (P) was analyzed by the three different methods. The EDX method allows for a microstructural analysis of intact, methylmetacrylate-embedded, undecalcified bone and the measuring points can thus be distinctly identified centrally in each trabecula. The analysis yielded 25.8 +/- 0.7 wt % Ca and 10.5 +/- 0.1 wt % P, compared with 22.2 +/- 0.5 and 23.0 +/- 1.0 wt % Ca, and 9.83 +/- 0.21 and 10.02 +/- 0.44 wt % P for INAA and ICPES, respectively. The EDX analysis was calibrated by consecutive measurements of a hard, pressed tablet of hydroxyapatit of known content. The mean Ca content deviated with -0.38 wt % from the given content and P with -0.89 wt %. We could not verify any particular interference from the embedding procedure, however, it is possible that the relatively lower P content still may reflect this. The magnesium (Mg) concentration was 0.31 +/- 0.02 wt % by EDX and 0.26 +/- 0.02 wt % by INAA. The EDX analytical method provides a useful tool for simultaneous elemental quantification in bone. It has the advantage of permitting the use of regular bone biopsy material and thus allowing for a unique microstructural evaluation of the degree of mineralization.(ABSTRACT TRUNCATED AT 250 WORDS)
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