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At least 109 records · Page 6Linked to original sources
PubMed1975

On the relationship between tetracycline and the incremental lines in dentine.

Ground and decalcified sections of human, goat and pig teeth were examined using polarized and ultraviolet fluorescence microscopy, microradiography and electron microscopy. The experimental animals were given doses of tetracycline within the range 3-150 mg/kg. After the low doses there was no evidence of any disturbance of mineralization or of structural organization in either the goat or the pig. After the higher doses, however, the tetracycline lines usually corresponded with a disturbance of structural organization and often with a disturbance of mineralization as well. In the human cases, the tetracycline lines sometimes corresponded with a disturbance of mineralization or of structural organization. However, our evidence suggests that the disturbances in the structure or mineralization of the dentine in the human subjects were not caused by the tetracycline. It was concluded that, provided the dose is kept low (3-31 mg/kg) tetracycline can be used as a reliable non-toxic marker in growth studies and is also used in the study of mineral deposition.

Animals↗
PubMed1991

Binding of the specific ligand to Fc receptors on Trypanosoma cruzi increases the infective capacity of the parasite.

The infective capacity of Trypanosoma cruzi was significantly increased after treatment with monoclonal IgG1 antibodies, whether or not specific for the parasite; minimal or no change in infectivity was seen after treatment with IgG2a, IgG2b or IgG3 monoclonal antibodies. The stimulatory effect was evidenced by elevated numbers of trypanosomes invading mammalian host cells in vitro compared to parasites treated with medium alone. Greater infectivity was also induced by pure human Fc, suggesting a role for Fc receptors on the organism. This inference received support in the fact that protein A inhibited the stimulatory effect of Fc. In addition, Fc-treated parasites incubated with fluorescein-labelled F(ab')2 from goat anti-human IgG exhibited fluorescence detectable by both ultraviolet microscopy and flow cytometry. 125I-Fc binding to T. cruzi was found to be saturable at 0 degrees and was inhibited by cold Fc but not by bovine serum albumin (BSA) or orosomucoid. Interestingly, 125I-Fc binding was greater at 37 degrees and it was not saturable with the concentrations that did saturate at 0 degrees. Possibly, Fc might up-regulate expression of its own receptor and greater endocytosis could take place at 37 degrees. Significant increases in infectivity were detectable after a 40 min pretreatment with Fc--hinting that Fc could trigger a chain of biochemical events underlying the phenomenon--and were reversible, becoming undetectable 2 hr after Fc removal. The average number of Fc receptors per parasite, determined at 0 degrees (at which binding saturation was possible), was estimated as 5 x 10(5), the dissociation constant was of the order of 10(-6)-10(7)M. The present results define an important biological role for an Fc-binding T. cruzi surface component and expose the capacity of this organism to exploit even elements of the immune system in its quest to attain intracellular localization, required for multiplication.

Animals↗
PubMed1978

Characteristics of neonatal calf diarrhea virus ribonucleic acid.

The nucleic acids of neonatal calf diarrhea virus were characterized by isopycnic centrifugation in Cs2SO4, electron microscopy, ultraviolet absorbance temperature profiles and polyacrylamide gel electrophoresis. These studies indicated that the neonatal calf diarrhea virus genome consists of 11 segments of double stranded RNA with a total molecular weight of 10.75 million daltons.

Centrifugation, Isopycnic↗
PubMed1989

Postmortem pink teeth. Histochemical identification of the causative pigment.

The phenomenon of postmortem pink teeth has been reported in subjects who have died suddenly and unnaturally, and whose bodies have been subsequently exposed to a wet or moist environment. Ground and EDTA-decalcified sections of teeth of 21 corpses exhibiting postmortem pink-stained teeth were investigated for the identification of the responsible pigment. With histochemical methods and ultraviolet microscopy, the causative pigment was identified as undegraded hemoglobin. Staining from hemosiderin, bile and bile-related pigments, and porphyrins was ruled out. However, histochemical techniques are unable to reveal the form in which the hemoglobin occurred. The cause of death or time of death had no observable effect on the staining reactions for hemoglobin in the teeth.

Burns↗
PubMed1978

[Polarized ultraviolet fluorescence microscopic study of the structural changes in muscle fiber contractile proteins. V. The possible nature of the conformational rearrangements in heavy meromyosin in fiber relaxation].

The mode and degree of tryptophanyl orientation relative to muscle fiber axes within hydrophobic and hydrophylic sites of myosin macromolecule in the presence of a fluorescence quencher (acrylamide, NO-3) during rigor and relaxation of glycerinated muscle fibers were studied using the polarized ultraviolet fluorescent microscopy. It was shown that myosin tryptophanyls both in LMM and HMM are oriented with their short axes along the longer axis of muscle fiber. Tryptophanyls in LMM have a more pronounced anisotropy of orientation in comparison with the fluorophore orientation anisotropy in hydrophobic sites of HMM. During the muscle fiber relaxation, conformational changes in HMM take place owing to which a section of polypeptide chain with a hydrophilic fluorophore is probably submerged deep into the macromolecule and becomes unapprochable to the quencher.

Animals↗
PubMed1985

Osteochondritis dissecans of the femoral condyles. A histological study with pre-operative fluorescent bone labelling and microradiography.

A review of the literature in osteochondritis dissecans of the femoral condyles reveals that the aetiopathology is still unclear and that relatively few histopathological studies have been carried out. The authors describe a method of study based on microradiography and on preoperative fluorescent labelling of the osteogenetic area followed by examination of the bone remodelling under ultraviolet light microscopy. The results in 12 adult cases are reported in relation to a topographical scheme which divides the lesions into four separate zones.

Adult↗
PubMed1982

Demonstration of rotavirus antigen in trypsin-digested paraffin tissue sections by immunofluorescence.

Trypsin-digested paraffin tissue sections were used to demonstrate rotavirus particles in small intestinal epithelial cells of dirrheic neonatal calves, using direct fluorescent-antibody assay. The results were compared with other techniques to demonstrate rotavirus particles in tissue sections by immunofluorescence. Enzyme treatment of deparaffinized tissue sections gave excellent results with distinct specific fluorescence and minimal background. Prior staining of the tissue section with Mayer's hematoxylin made simultaneous observation of the same tissue section by light and ultraviolet microscopies possible.

Animals↗
PubMed1984

Lectin binding to cystic stages of Taenia taeniaeformis.

Studies of membrane glycoconjugates of Taenia taeniaeformis were initiated by assays of the lectin binding characteristics of 35-day-old cysticerci. Parasites fixed in glutaraldehyde were incubated with one of the following FITC-labelled lectins: Concanavalin A (Con A), Lens culinaris agglutinin (LCA), Ricinus communis agglutinin (RCA), peanut agglutinin (PNA), fucose binding protein (FBP) and wheat germ agglutinin (WGA) and either their specific or a nonspecific sugar. Ultraviolet microscopy revealed that only Con A and LCA bound in large amounts to the surface of cysticerci. This binding was partly inhibited by the specific sugar, but the nonspecific sugar had little effect. The lectin not removed by either of the sugars may have been bound nonspecifically to the charged glycocalyx. Lectins were primarily bound on the anterior third of the parasite around the scolex invagination. Kinetic studies of lectin interactions were carried out with LCA and RCA by spectrophotofluorometric analysis of the amount bound specifically or nonspecifically over a range of lectin concentrations. Lens culinaris lectin binding was found to be specific and involve 2 receptors which showed large differences in their affinity for lectin and prevalence on the surface. Ricinus communis lectin did not bind specifically but nonspecific interactions were observed. Adherence of small numbers of host cells was shown to have no measurable effect on the lectin binding characteristics. The results suggest that the major surface carbohydrates exposed are D-mannose and/or D-glucose residues with the other sugar groups poorly represented. This relatively homogeneous surface may have implications for the antigenicity of the parasite in its host.

Animals↗
PubMed1978

Immunoperoxidase techniques: practical and theoretical aspects.

Immunoperoxidase methods have much in common with established immunofluorescence procedures. Both have the potential for specific demonstration of cell and tissue antigens, with similar limitations demanding rigorous control of specificity. In any study the choice of an immunofluorescence method or an immunoperoxidase method can be made on rational grounds, according to the desired objective, the degree of morphologic detail required, the material available for study, and the ease of access to specialized ultraviolet microscopy. In this article the relative merits of the various immunoperoxidase procedures are examined, and theoretical and practical aspects governing the application of these methods are discussed in detail.

Animals↗
PubMed1979

[State of the contractile apparatus during the development of a pathological process in the muscles. III. The nature and sequence of the structural changes in the contractile apparatus in Zenker's necrosis].

Using polarized ultraviolet (UV) fluorescence microscopy, it was shown that the local damage of muscle fibres causes in their morphologically unchanged parts the alternation of regions, being in different functional states referred to as "pseudocontraction" and "superrelaxation". The pattern of UV fluorescence anisotropy suggests that conformation of contractile proteins by "pseudocontraction" is similar to that at contraction, though changes in sarcomere length do not occur. The "superrelaxation" is characterized by a desorganization of myofilaments. During the spreading of Zenker's necrosis, the "pseudocontraction" is seen transferred first into "superrelaxation", and then into irreversible contracture and rigor. "The boundary of Zenker's necrosis" overlaps with the boundary of the self-propagating irreversible contracture. There is no proper boundary of Zenker's necrosis, because the destructive changes are observed over all the muscle fibre. Contraction nodules arise in the regions of "superrelaxation" and follow the changes of the contractile system, peculiar of contracture. The study of the influence of medium ionic composition on the development of Zenker's necrosis suggests that the arising and spreading of destruction are inseparably associated with the irreverrsible changes of intracellular membrane structures, and with the possibility of propogation of the damage signal by these structures along muscle fibres.

Animals↗
PubMed1981

[State of the contractile apparatus in the development of a pathological process in muscle. IV. Effect of Ca2+ on the process of contraction nodule formation and on the ATPase activity of muscle actomyosin in Zenker's necrosis].

Using phase-contrast and polarized ultraviolet (UV) fluorescent microscopy, the structure of single muscle fibres was studied in the course of the contraction module formation during Zenker's necrosis. The degree of manifestation of destructive changes in the contractile system was shown to depend upon the concentration of extracellular Ca-ions. With decreasing Ca2+ concentration, the fibre loses the ability to form contraction nodules peculiar to the Zenker necrosis, and the development of this process is interrupted at the stage of sarcomere supercontraction. The UV fluorescent anisotropy pattern of fibre regions, conforming with the contraction nodules, suggests the occurrence of a more pronounced disorganization of contractile system in the presence of Ca2+. The ATPase activity of actomyosin isolated from altered muscle was studied to appreciate the functional state of the contractile system. This actomyosin was found to be inactivated 1.5 times as much as that isolated from muscles treated during Zenker's necrosis in calcium-free media.

Actomyosin↗