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  • 1
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Glutaraldehyde (GA) crosslinking (fixation) of collageneous tissues is a widely used method for the preparation of implantible tissues to be used as biomaterials. In an attempt to optimize the fixation process, experiments were carried out with two types of collagen (native collagen membrane and synthetic collagen sheet) to study the effect on crosslinking of temperature, GA concentration and fixation time. Secondly, stimulation of GA diffusion was studied and finally, a procedure of low T-presoaking followed by brief exposure to high temperatures was investigated. As a measure of the degree of crosslinking the shrinkage temperature (T s) was determined. Temperature (20°C or 45°C), concentration (0.1% or 1.0%) or fixation time (4 or 24 h) were found to be positively correlated with the T s of the collagen sheets. Whereas untanned collagen exhibits a T s of around 60°C, short-term (1 or 5 min), high-temperature (50°C) fixation with a 0.1% GA solution caused the shrinkage temperature to increase to 72°C and 85.1°C, respectively. Fixation with 0.01% GA for 5 min at 50°C appeared equally effective as 1 min with 0.1% GA (T s=70°C). Microwave irradiation showed to be slightly more effective in enhancing the crosslinking process compared with conventional heating. Surprisingly, at any combination of temperature, concentration and fixation periods of 4 h or 24 h, an increased T s towards the central regions of the collagen was observed. Soaking the samples at 20°C (1 h) or at 0°C (3 h) with subsequent short-time heating to 45°C caused an almost equal rise in T s throughout the collagen samples and is therefore recommended for preparing implantable tissues.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Histochemistry and cell biology 73 (1981), S. 165-169 
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The transition from infanthood to adulthood is characterized by a sequence of events which are not yet fylly understood. Hormonal changes influencing neuronal circuits in various hypothalamic area are —at least in part — held responsible. Using catecholamine fluorescence techniques in rats it has been found that a displacement of dopaminergic cells can be seen; the fluorescence activity shifting from the median eminence at day 20 after birth to the dorsolateral part of the arcuate nucleus around day 45 after birth, as is the case for catalase positive cells in these areas. It is concluded that the displacement of at least two populations of cells from the median eminence to the arcuate nucleus runs parallel to the onset of puberty. The relation of this shift in respect to the suprachiasmaticpreoptic control will be discussed.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Histochemistry and cell biology 75 (1982), S. 145-150 
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The administration of monosodium glutamate (MSG) to newborn rats accelerates by two weeks the migration of fluorescent dopaminergic perikarya from the median eminence towards the arcuate nucleus at the time of puberty, which normally occurs from day 22 till 55 after birth. It is hypothesized that MSG affects the trigger mechanism for this migration. The disappearance of fluorescent dopaminergic cells that occurs after MSG administration is considered as a secondary effect.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular histology 20 (1988), S. 323-328 
    ISSN: 1573-6865
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary This paper evaluates and extends the novel method of preparing tissue blocks for paraffin sections within 30 to 60 min, that was proposed in early 1985 in a paper by Boonet al. (1986). More than 2 years' additional experience and testing various microwave ovens has led to new protocols reported in this paper. Results are given of testing (i) an especially designed microwave oven for histoprocessing, (ii) microwavable reagents, (iii) processing larger numbers of specimens simultaneously, (iv) handling different types and sizes of tissue. It is concluded that effective temperature control offers substantial advantages. In addition, the possibilities of performing routine diagnostic pathology omitting formalin altogether are sketched.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular histology 22 (1990), S. 381-388 
    ISSN: 1573-6865
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Microwave technology has become important in preparatory techniques for microscopy in many different ways. This paper discusses various aspects of the physics of microwaves. It gives some theoretical background to understand the practical procedures. Some peculiarities in the optics of microwaves are pointed out, and the practical implications in particular of choosing the size and shape of samples and containers are discussed. Diffusion rates and chemical-reaction rates increase exponentially with temperature, so that precise temperature control is essential in most histochemical procedures. Such control is complicated by localized heating of the system, and of temperature sensors themselves, which may occur as a result of microwave irradiation.
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  • 6
    ISSN: 1573-6865
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The effect of short time heating of aqueous solutions of glutaraldehyde (GA) on relative aldehyde concentration was determined using spectrophotometric analysis. Because free monomeric GA absorbs U. V. light at 280 nm, whereas the alpha, beta polymeric forms absorb at 235 nm, the purity of GA solutions can be expressed as the ratio: A 235 nm/A 280 nm (purification index, P.I.). Heating of 4 ml aliquots of 0.85% distilled aqueous GA solution resulted in an increase of the absorption at 280 nm which is correlated positively with temperature. No increase of absorption at 235 nm was found when solutions were kept at 40°C for several hours. The increase of absorption at 280 nm is caused by a rapid decyclization of hemiacetals producing an increase in free aldehyde concentration. No major differences in absorption were found between the solutions heated by microwave and by conventional heating. However, because microwave irradiation is known to produce an homogeneous rise in temperature, especially in bulky samples, it is expected that the results of fixation procedures will improve by the combined effect of higher temperature and enhanced diffusion rates of the fixating species.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular histology 20 (1988), S. 329-334 
    ISSN: 1573-6865
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Bone marrow smears were made and fixed in methanol or formaldehyde. Marrow sections of various thicknesses were also prepared from formaldehyde fixed marrows embedded in paraffin or plastic (glycol methacrylate). The different smears and sections were then stained by a Romanowsky-Giemsa procedure. Some specimens were stained using a standard microwave-stimulated method previously used diagnostically. The effects of technical variations were studied, including degree of microwave irradiation and the staining time. Comparisons of the resulting staining outcomes showed that microwave stimulated Romanowsky-Giemsa staining of plastic sections is a rate controlled process. Unusual aspects of the staining pattern of plastic sections (namely the purple basophilic cytoplasms and nucleoli, and blue chromatin) are due to microwave stimulation and formaldehyde fixation respectively.
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  • 8
    ISSN: 1573-6865
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The application of microwave irradiation at various steps in ‘normal’ EM procedures has been investigated. 1. The temperatures in various aqueous volumes were measured during microwave irradiation. Increases were small and the final temperature could be controlled by cooling the glass base plate. 2. The influence of microwave irradiation on the various fixation schedules for the electron microscopy of single cell populations was studied and the results favoured the idea that by the application of microwave irradiation a more life-like ultrastructural preservation could be obtained. 3. Peroxidase-like activity in erythrocytes, acid phosphatase activity in resident macrophages and peroxidase activity in monocyte granules was apparently not influenced by microwave irradiation during aldehyde fixation and incubation. 4. The anticipated microwave-induced penetration enhancement of cerium ions in a cytochemical reaction procedure to detect acid phosphatase activity in resident macrophages was not observed.
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  • 9
    ISSN: 1573-6865
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary A DNA-in situ hybridization protocol was adapted for application to sections of routinely processed paraffin embedded material. This protocol was developed previously for detecting DNA-virus infected cells in whole cell preparations and employs biotinylated DNA as probe. Three different biotin detection methods were optimized and applied. The first uses streptavidin and a biotinylated complex of alkaline phosphatase, the second consists of an immunogold-silver staining, and the third of a peroxidase technique using a silver amplification. The alkaline phosphatase method was the most rapid, and as sensitive as the immunogold-silver staining. The peroxidase method was the most sensitive. Microwave irradiation was applied to the different incubation steps of these three detection methods. Short incubations with microwave irradiation gave very poor results when peroxidase labelled antibodies were used. Short incubation with microwave irradiation gave results comparable to those obtained with conventional incubations, when streptavidin, antibiotin, complexed alkaline phosphatase, or gold labelled goat antirabbit were used. It was thus shown that microwave irradiation creates the possibility of a very rapid label-detection for nonradioactive DNA-in situ hybridization.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular histology 22 (1990), S. 335-340 
    ISSN: 1573-6865
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary A morphological and morphometrical study was performed on testicular cells after microwave stabilization of the tissue while immersed in phosphate buffered saline (PBS), 0.9 NaCl or Tris-HCl. Fixation in Carnoy's fluid without irradiation was chosen as a control chemical fixation method. After microwave stabilization or chemical fixation, the testes were embedded in paraffin or in plastic (glycolmethacrylate). An excellent morphology, comparable to that after chemical fixation in Carnoy's fluid, was observed in the plastic sections of tissue irradiated in PBS or NaCl, even when the sections were subsequently treated with an aggressive reagent at high temperature, required for the Feulgen reaction. The nuclear area of the microwave-stabilized Sertoli cells was 37–46% smaller in haematoxylin-eosin stained, paraffin sections in comparison with that in the glycolmethacrylate sections. The microwave-stabilized, paraffin-embedded tissue was much more vulnerable to the hot HCl treatment of the Feulgen staining than the chemically fixed tissue, resulting in an additional 10–20% decrease in nuclear size. The latter finding is particularly important for quantitative microscopy, where the Feulgen staining method is often employed.
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