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Biomedical subjects

I Becker

Publications and source records attributed to I Becker.

At least 73 records · Page 4Linked to original sources
PubMed1990

[The mechanism of natural resistance in the rat to Entamoeba histolytica].

The data presented in this paper may be summarized as follows: 1) intraportal injection of a virulent strain (HM-1) of Entamoeba histolytica in Wistar rats, of both sexes, gives way to non-progressive microscopic changes, characterized by a rapid leukocytic reaction surrounding the amebas, disappearance of the parasites within 5 hours, and total lack of hepatic damage; 2) leucopenia only modifies the previous description by the fact that there are no leucocytes around the amebas, although these disappear in the same time, showing, at this moment, an early and prominent vacuolar degeneration; 3) hypocomplementaemia shows the same results as leucopenia; 4) fragments and extracts from various tissues from the rat and hamster show variable degrees of interference with the viability of axenic amebas of Entamoeba histolytica conserved in culture; only a minimal part of the interference to be due to the activity of the complement which is present in the tissue extracts.

Animals↗
PubMed1990

Mitosis and polykaryon formation of Entamoeba histolytica in axenic cultures.

Axenic cultures of E. histolytica were established in Coplin jars containing glass slides. The cultures were harvested after 72 hours, fixed and stained with Giemsa and acridine orange. Sedimented parasites were used for inclusion in methacrylate for thin sections that were stained with acridine orange, and epon-araldite for ultrathin sections for electron microscope study. The Giemsa stain showed trophozoites of different sizes and variation in the shape, size and number of the nuclei. Division occurred by budding, sometimes by fission, with occasionally apparent extrusion of nuclear material into the cytoplasm. Acridine orange demonstrated DNA in the center of the nuclei and within intranuclear small vesicles. The electron microscope showed mono and multinucleated amoebae with irregular nuclear membranes, coarse material attached to the nuclear membrane, and sometimes intranuclear parallel microtubules without nuclear attachment. There were structures around the karyosome in some nuclei resembling chromosomic material of superior eukaryotes, without kinetochore, as well as intranuclear small vesicles containing sausage-shaped structures. The findings suggest that E. histolytica undergoes polyploidy evidenced by giant nuclei, followed by segregation of chromatin in smaller nuclei, by budding and production of polykaryons of different nuclear size. Multiple small intranuclear vesicles containing structures that may represent forms of rRNA thus contributing to ribosomes. Absence of cytokinesis is the cause of the production of polykaryons with an asynchronous rate of nuclear and cytoplasmic division. Polynucleation also could be related in the origin of cyst formation in amoeba, as unknown selective forces may induce amoebae the synthesis of chitin capsule.

Animals↗
PubMed1989

Proteinases of Entamoeba histolytica associated with different subcellular fractions.

Crude lysates of Entamoeba histolytica (strain HM 1:IMSS) analyzed by substrate gel electrophoresis in 12.5% acrylamide separating gels with reducing agents showed six hydrolysis zones with apparent molecular weights of 73,000 (high), 45,000, 36,000 (intermediate), 30,000, 26,000 and 23,000 (low molecular weight proteinases). Amebic lysates fractionated using the procedure of Aley et al. or the procedure of Rosenberg and Gitler and analyzed by the same method show all enzymes in the fractions with the soluble components and only the intermediate and low molecular weight proteinases in the fraction containing internal vesicles or membranes and plasma membrane. Some of these proteinases seem to be integral membrane proteins since they resist treatment with high salt, high urea buffer. All fractions are capable of digesting azocasein. Fractionation of amebic lysates by hydrophobic chromatography using phenyl-Sepharose or phase separation of amebic extracts with Triton X-114 show that proteinases with high, intermediate and low molecular weight behave as hydrophilic proteins while only proteinases of intermediate and low molecular weight behave as hydrophobic proteins. These results suggest that some proteinases are segregated in different compartments of the cell.

Animals↗
PubMed1989

Immunohistological investigation of mononuclear cell infiltrates in meningiomas.

Immunohistochemical analysis of inflammatory cell density and infiltrate subpopulations in 42 meningiomas was performed. Evaluation of infiltrating cell density was carried out by cell counting. Meningothelial and fibroblastic meningiomas contained an average of 3% mononuclear cells; the few lymphocytes were localized in the perivascular spaces. In subtypes with cellular atypies and recurrent tumors, the inflammatory cells increased up to 9%. We found small mononuclear cell clusters in the tumor parenchyma in addition to the perivascular infiltrates. Marked degrees of infiltration were found in anaplastic meningiomas (average 13.5% of total cells). The lymphocytic infiltrates were localized in multilayered perivascular cuffings and intraparenchymal cell clusters. The composition of the infiltrates, i.e., predominantly a mixed staining of cytotoxic/suppressor and helper cell phenotypes, did not vary in the different subtypes. We conclude: (1) that inflammatory infiltration is more frequent and denser in malignant than in benign meningiomas; and (2) that the tumor defense mechanisms in meningiomas are mediated particularly by T cell mediated immunity.

Antibodies, Monoclonal↗
PubMed1989

Monoclonal antibody analysis of major histocompatibility complex expression in human meningiomas.

Using monoclonal antibodies (MAB) in combination with the alkaline phosphatase anti-alkaline phosphatase technique, 20 meningiomas were examined for the expression of major histocompatibility complex (MHC) antigens. Most of the tumor cells were labeled with the MAB for class I MHC antigens. In addition, class I reactivity was seen in the tumor blood vessels, presumably reflecting labeling of the endothelial cells. Tumor cells and endothelium were not labeled with the MAB for class II MHC antigen HLA-DR. Occasionally a staining of periendothelial cells was detected. The presence of MHC antigens supports the assumption that endothelial cells play a role in antigen presentation, perhaps relevant to the initiation of an immune response, and that meningioma cells can be a target of T cell-mediated immune reactions.

Antibodies, Monoclonal↗
PubMed1989

Histogenesis of stromal cells in cerebellar hemangioblastomas. An immunohistochemical study.

Fifteen cerebellar hemangioblastomas were examined by immunohistochemistry for expression of neuron-specific enolase (NSE) and various neuropeptides using the avidin-biotin-complex peroxidase reaction with the following antibodies: NSE, synaptophysin, serotonin, substance P, vasoactive intestinal peptide (VIP), neuropeptide YY, neurotensin, and leu-enkephalin. In all tumor biopsies most of the stromal cells were positive for NSE. About 30% of the stromal cells showed a weak cytoplasmic synaptophysin positivity. Approximately 25% of the stromal cells were labeled with antibodies against substance P and neuropeptide YY. The partly strong reactivity was localized preferentially in perinuclear regions. These positive cells were mainly distributed in small cell clusters but were also scattered in the tumor parenchyma. In all tumor biopsies scattered cells exhibited strong perinuclear enkephalin positivity, corresponding probably to mast cells, whereas stromal cells were entirely negative. For serotonin, VIP, and neurotensin no specific reaction was seen. On the basis of these findings it is proposed that hemangioblastomas have a neuroendocrine component.

Biopsy↗
PubMed1988

Adult-onset rod disease with abundant intranuclear rods.

The third case of adult-onset rod disease (nemaline myopathy) with abundant myofibrillar as well as intranuclear rods is described. The 61-year-old woman suffered from progressive weakness of proximal extremities and of the neck, mimicking polymyositis. Muscle biopsy revealed a striking myopathic pattern, with intranuclear rods occurring in 31% of the fibres. On light and electron microscopy and by immunohistochemical study, the rods differed from myofibrillar rods. The absence of alpha-actinin in intranuclear rods suggests an enhanced readiness of actin filaments to bind to diverse proteins, instead of overproduction of alpha-actinin as the pathogenetic basis of the rod formation.

Actinin↗
PubMed1988

Entamoeba histolytica: role of amebic proteinases and polymorphonuclear leukocytes in acute experimental amebiasis in the rat.

The injection of 1 x 10(6) trophozoites of axenically grown Entamoeba histolytica strain HM-1 in the subcutaneous tissue of the rat results in an acute and self-limited inflammatory process, characterized by the early onset of conspicuous tissue necrosis and focal hemorrhage in the vicinity of the parasites, followed by infiltration with polymorphonuclear leukocytes. The process develops for 5-10 hr but during that period amebic trophozoites progressively disappear, leukocytes undergo degenerative changes, and the lesion tends to heal in 72-96 hr. In leukopenic animals (less than 1000 white blood cells/ml) tissue necrosis and hemorrhage are equally conspicuous in the neighborhood of amebas. Inhibition of amebic proteinase activity prior to injection by heat denaturation, p-hydroxy-mercuri-benzoate (PHMB), soybean trypsin inhibitor (STI), and human alpha-2-macroglobulin (alpha 2M), alone or in various combinations, results in absence or notorious decrease in tissue necrosis as well as in clearly diminished inflammatory reaction. This effect is particularly evident when cysteine proteinases are either specifically or generally inhibited. On the other hand, amebic proteinase inhibition with alpha 2M and STI does not interfere with the cell-killing capacity of trophozoites co-incubated in vitro for 2 hr with rat peritoneal cells enriched for macrophages. We conclude that in acute experimental amebiasis produced in the subcutaneous tissue of the rat, amebic cysteine (and perhaps other) proteinases are primarily responsible for necrosis and are also important, but not essential, for inflammation. We also suggest that in this model polymorphonuclear leukocytes are not required for tissue necrosis. Finally, in an in vitro model, the cell-killing capacity of amebas is not influenced by the proteinase activity of the parasite.

Amebiasis↗
PubMed1987

Catalytic classes of proteinases of Entamoeba histolytica.

Endopeptidase inhibitors were used to determine the catalytic classes of proteinases present in extracts of Entamoeba histolytica (strain HM 1:IMSS) axenically grown in vitro. Cysteine proteinases account for most of the proteolytic activity; one or more proteinases with different catalytic mechanisms are also present but could not be unambiguously assigned to a particular catalytic class. Proteinases in amebic lysates were resolved by polyacrylamide gel electrophoresis with sodium dodecyl sulfate. The detergent was exchanged with Triton X-100 and the proteolytic activity in the gels was demonstrated by overlaying it on another gel containing the substrate. Four lysis zones were observed corresponding to molecular weights of 66,000, 56,000, 40,000 and 27,000. The first cannot be classified yet, but the last three showed properties consistent with those of cysteine proteinases. Finally, a novel technique is described which uses purified human alpha-2-macroglobulin to trap, purify and characterize proteases from amebic lysates. The results obtained with this technique confirm those of the overlay technique, since both methods reveal four distinct proteinases in the two different amebic preparations examined.

Animals↗
PubMed1978

[Oral examinations by exfoliative cytology of the healthy oral mucosa and inflammatorily altered gingiva (author's transl)].

Exfoliative cytology allows important information to be obtained about the structure and function of individual sections of tissue. Use of this particular method of examination is characterized by simplicity and freedom from strain on the subject being tested. In addition, the method yields clear and comprehensive results. Smears obtained from different regions of the oral cavities of subjects with clinically healthy oral mucous membrans and intact teeth were carefully analyzed. Also examined by clinical methods as well as by exfoliative cytology was the healthy gingiva, with parodontopathia inflammata superficialis and parodontopathia inflammata profunda serving as reference groups.

Cytological Techniques↗
PubMed1978

[The origin and treatment of accidents after the injection of penicillin].

In case of unintentional intravascular uptake, the injection of repository penicillin may produce severe embolic obturations. Several batches of respository penicillin were tested for their crystal size in ready-for-injection suspensions. The greatest crystals were found in preparations with a high proportion of benzylpenicillin-procaine. To avoid untoward reactions (Hoigné syndrome, Nicolau syndrome), the recommendations of the Central Expert Committe on Drugs must be considered. Furthermore, the measures required in case of anaphylactic shock are dealt with.

Anaphylaxis↗
PubMed1978

[Comparative clinical and exfoliative cytological studies on the use of occlusive dressings].

Among the variety of surgical packs described in the literature, zinc oxide-based packs have proved especially useful. Two types still currently used are the zinc oxide-eugenol pack according to Büchs and Walter and the pack modified by Behlke which contains Peruvian balsam in place of eugenol. Of 27 patients who had undergone a periodontal-surgical intervention, 6 were treated with a zinc oxide-eugenol pack, and 21 with a pack modified by Behlke. Clinical and cytological examinations were performed before intervention, at each change of pack (on the 5th, 8th and 14th days after intervention) and 4 weeks after intervention. The comparison of the results obtained shows the superiority of the pack modified by Behlke over the zinc oxide-eugenol pack.

Balsams↗