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Biomedical subjects

M Sahm

Publications and source records attributed to M Sahm.

15 recordsLinked to original sources
PubMed2001

Effect of ultraviolet radiation on melanogenesis in four different types of cultured bovine ocular pigmented cells.

BACKGROUND: Ultraviolet radiation is thought to play a causative role in various ocular diseases such as macular degeneration, cataract, and possibly melanomas. Since most of the energy is absorbed by pigmented cells, the aim of this study was to examine and compare the reactions of different ocular melanocytic cells to ultraviolet light in vitro. MATERIALS AND METHODS: Bovine iris melanocytes, choroidal melanocytes, iris pigment epithelial cells, and retinal pigment epithelial cells were isolated and cultured. Semiconfluent cultures were exposed to ultraviolet radiation (280-380 nm). Cell number and melanin content were measured 10 days after radiation. Selected samples were examined by transmission electron microscopy. RESULTS: Following irradiation with ultraviolet light for 30 s, 60 s, and 120 s, the number of cells in culture decreased markedly. In contrast, total melanin content in the cultures of iris melanocytes, choroidal melanocytes, and iris pigment epithelial cells did not decrease despite the reduced number of cells. This finding suggested an increase in melanin per cell. However, the increase in average melanin content observed was not due to melanogenesis, because treatment with the melanogenesis inhibitor alpha-methyl-p-tyrosine did not reduce the melanin content of the cultures and electron-microscopic examination showed no morphological evidence of increased melanogenesis. CONCLUSION: In vitro, there was no convincing evidence of ultraviolet radiation-induced melanogenesis in ocular pigmented cells. Thus, it seems that ultraviolet radiation is a selection factor: more densely pigmented cells survive the treatment better than less pigmented cells.

Animals↗
PubMed2000

Light and electron microscopic examination of endothelial cells from bovine retinal vessels in long-term cultures.

The aim of the present work was to examine and compare the ultrastructure of bovine retinal endothelial cells (BRECs) in vitro during several passages in a medium selective for endothelial cells. The identity of the endothelial cells was confirmed immunohistochemically, up to the tenth passage. Changes in their ultrastructure in comparison to endothelial cells in vivo occurred at the onset of culturing and not progressively with repeated passages. The cultured BRECs show high metabolic activity in all passages. While retaining their identity as endothelial cells, they modify their lipid metabolism, so that lipids are stored. This change in lipid metabolism was induced by the medium.

Animals↗
PubMed2000

Is stage conversion the initiating event for reactivation of Toxoplasma gondii in brain tissue of AIDS patients?

Reactivation of chronic toxoplasmosis resulting in Toxoplasma encephalitis (TE) is a common event in acquired immune deficiency syndrome (AIDS) patients. Conversion from Toxoplasma gondii bradyzoites to tachyzoites is a prerequisite for reactivation. Until recently, the study of stage conversion in human tissue was not possible due to the lack of antibodies that recognize stage-specific epitopes after long-term formaldehyde fixation. Using the combination of a polyclonal anti-T. gondii antibody, the cyst-stage-specific monoclonal antibody CC2, and a tachyzoite-specific polyclonal antibody (anti-SAG1, recombinant), we tried to demonstrate parasite differentiation in the brain tissue of 10 AIDS patients with clinically suspected TE. Double labeling of the stage-specific antibodies enabled us to demonstrate interconversion between tachyzoites and bradyzoites for the first time in human tissue. The study confirmed that the transformation process is nonsynchronous and that the manifestation of TE depends on the degree and site of tissue destruction caused by invading tachyzoites. The original source of tachyzoites could never be located, but a few samples suggested that tachyzoites may invade by dissemination across the blood-brain barrier. Cyst rupture as the first event in the process of reactivation was not seen. We conclude that the initial site(s) of reactivation will be destroyed by tissue-destructive tachyzoites long before clinical symptoms occur.

AIDS-Related Opportunistic Infections↗
PubMed1998

GRA7, an excretory 29 kDa Toxoplasma gondii dense granule antigen released by infected host cells.

Monoclonal antibody (mAb) TxE2, reactive with Toxoplasma gondii excretory products, detects an acidic 29 kDa protein (p29) which, in 2D gel electrophoresis, exhibits a migration pattern distinct from those of the toxoplasmic excretory proteins described so far. The sequence of seven peptides from tryptic digestion of isolated p29 allowed the design of primers to obtain the coding DNA sequence. The full-length gene was amplified from genomic DNA of T. gondii strain BK and the sequence was identical with that of the corresponding cDNA, providing evidence for an intron-free gene structure. A single mRNA transcript of 1.3 kb was detected by Northern blot analysis. The deduced 236 amino acid protein contains a putative N-terminal signal peptide, one site of potential N-linked glycosylation, and, close to the C-terminus, a further hydrophobic, putative transmembrane domain. With synthetic peptides spanning the sequence of p29, the epitope for mAb TxE2 was mapped adjacent to the putative signal sequence. The antigen, which represents almost 0.5% of T. gondii protein, is expressed in strains of all three intraspecies subgroups, and is associated with the parasite dense granules as demonstrated by immunoelectron microscopy. In tachyzoite-infected cells, p29 accumulates within the parasitophorous vacuole and co-localizes with its delimiting membrane. In bradyzoite-infected cells, p29 is present within the host cell cytoplasm as detected by immunofluorescence staining, and, furthermore, in the supernatant of cyst-bearing cell culture lacking extracellular parasites as shown by enzyme-linked immunosorbent assay (ELISA). Thus, p29 which is named dense granule protein (GRA)7 may indicate the presence of intracellular toxoplasma.

Amino Acid Sequence↗
PubMed1998

Infection and stage conversion during murine pulmonary toxoplasmosis: a study with three different strains of Toxoplasma gondii.

A murine model of pulmonary toxoplasmosis was examined morphologically and immunochemically using 3 strains of Toxoplasma gondii. BALB/c and NMRI mice were infected with tachyzoites of a virulent strain (RH) or with brain cysts of an avirulent (GAIL), or moderately virulent, strain (NED). Depending on the strain of T. gondii, the degree of infection, number of parasites, and replicative potential of T. gondii in lungs varied. In lungs of mice infected with the RH strain, the number of parasites increased in mice during the survival period. Only tachyzoites were found, as confirmed by stage-specific monoclonal antibodies. In lungs of mice infected with the GAIL strain or the NED strain, different stages of parasites were detected. Up to day 14 after infection, only tachyzoites were present, followed by bradyzoites between days 14 and 20 after infection. The number of cysts decreased and finally could not be detected in this organ. In general, the number of cysts that developed in the lungs was smaller than the number that developed in the brain.

Animals↗
PubMed1998

[Laparoscopic versus conventional appendectomy].

From 1/1995 to 8/1997 857 appendectomies were observed in a prospective study. From then on in our clinic has done more laparoscopic then conventional operations, and has developed in the years before a permanent laparoscopic team. For all operations resterilized MIC-instruments are used. Preparation is done with bipolaric instruments and scissor, the appendix stump is supplied a with Röder-sling. The expensive Endo-GIA was used only 3x, if the coecumpole was also inflamed. Because of the fantastic intraabdominal view additional findings quickly be recognized through the laparoscopic method. It was then possible, to plan the therapeutic management exactly. Also variations of the appendix-position are seen clearly and can be operated on without other incisions. There is no significant difference in time between the two methods as we have seen here in practice (35.3 minutes for the conventional and 43.8 for the laparoscopic operation)--they will assimilate, when the surgeon is routine. Fat and muscular patients profit definitely. The problems of wound infection have been rarely observed by the laparoscopic operation. The rate of intraabdominal abscesses was 1.9% and therefore higher as by the conventional method (0.2%). This could be reduced during the period of the study, because we now often lavage and drain. We think that there are no surgical opponent indication to the laparoscopic appendectomy. The reliable conventional technique has to be an obligate technique also in future.

Adolescent↗
PubMed1997

Cyst formation by Toxoplasma gondii in vivo and in brain-cell culture: a comparative morphology and immunocytochemistry study.

Formation of Toxoplasma gondii cysts was examined in cultured murine brain cells and was compared with the development of cysts in mouse-brain tissue. Cultures of mixed glial cells from neonatal mouse brain were infected with bradyzoites of the avirulent T. gondii strain DX. The development and maturation of Toxoplasma cysts was monitored for up to 63 days after inoculation. Transmission electron microscopy indicated that in-vitro-derived cysts were morphologically similar to tissue cysts and were located intracellularly, even for up to 63 days postinfection. For immunohistological and immunocytochemical examination of both in-vivo- and in-vitro-infected material, monoclonal antibody (mAb) CC2 was used. MAb CC2 was shown to detect specifically the underlying granular material of the cyst wall without binding to the limiting membrane of the parasitophorous vacuole. This reactivity of mAb CC2 allows the distinction of bradyzoite-containing cysts from parasitophorous vacuoles harboring tachyzoites both in vitro and in vivo.

Amylopectin↗
PubMed1996

Nonimmunological factors affecting the release of excreted/secreted antigens from Toxoplasma gondii cysts.

The phenomenon of released Toxoplasma gondii cyst antigens was studied immunohistochemically and cytochemically. It could be demonstrated that the preservation and localization of excreted/secreted antigens depended not only on the technique of preparation and fixation of the infected tissue but also on the preservation of the host cell. The soluble, bradyzoite-secreted amorphous cyst matrix material is released either after host cell destruction or permeabilization of the cyst wall. Ultrastructural studies could prove that the liberation of the cyst from its host cell does not affect the basic structure of the cyst wall but causes stretching of the invaginated limiting membrane.

Animals↗
PubMed1996

The use of short-term cultures of Pneumocystis for drug testing.

A method for short-term drug testing for Pneumocystis is described. Up to now there was no successful cultivation method without feederlayers. Parasites for inocula were obtained from nude rats, kept under conventional conditions. Pneumocystis separation was done by two centrifugation steps from lung homogenates. Cultivation in a modified Tegoshi medium resulted in preservation of parasites for five days, however there was no growth of P. carinii. Quantification was done microscopically by counting trophozoites in triplicate cultures. The percentage of cysts with intracystic bodies did not exceed 2% of parasites. Tests with pentamidine isethionate as a reference drug demonstrated the suitability of this system for drug evaluation.

Animals↗
PubMed1996

Enhanced efficacy of a liposomal pentamidine preparation in Pneumocystis carinii in an ex vivo/in vitro culture model without feederlayer cells.

The effects of pentamidine isethionate, phosphatidylcholine-liposomes (PPC-lip) and combinations of both on the survival of Pneumocystis carinii trophozoites in a culture system without feederlayer cells were quantified. Pentamidine or PPC-lip alone reduced significantly the number of cells, with a clear dose dependence. Combinations of both drugs showed overadditive effects on cell counts reduction. Additional EM-investigations showed a rapid destruction of cell structures especially with the pentamidine/phospholipids-combinations. Our results could justify clinical tests with these combinations in AIDS patients in order to reduce the pentamidine dose, reduce local side effects with inhaled pentamidine while at least maintaining efficacy.

Animals↗
PubMed1986

Distribution of 125I-insulin in cardiocytes at steady state binding conditions at 37 degrees C.

The distribution of 125I-insulin in cardiocytes was analyzed by light microscope autoradiography. Semithin sections were used to distinguish between surface-bound and internalized tracer. At 37 degrees C, when steady state binding conditions were reached, 40 to 60% of the cell-bound tracer was located in the plasma membrane region and the remainder was in the cell interior. Autoradiograms of whole cells were used to study the distribution of tracer molecules on the cell surface. Because Poisson distributions of silver grains were observed on 90% of the cells, it was concluded that the distribution of the insulin-receptor complexes was close to random. In contrast to the findings of Schlessinger et al., no aggregation of insulin-receptor complexes into patches was observed.

Animals↗
PubMedDate not supplied

Short-time application of latanoprost does not stimulate melanogenesis in bovine ocular melanin-containing cells in vitro.

Topical use of latanoprost for glaucoma can lead to an increase in iris and eye lash pigmentation but the precise mechanism is unclear. To study the possible effect of this drug on ocular melanogenesis, we used cultures of bovine iris melanocytes, iris pigment epithelial cells, retinal pigment epithelial cells, and choroidal melanocytes. Latanoprost (at concentrations of 10(-8) and 10(-6) mol) was applied for 3 days, and cell numbers as well as melanin content were measured prior to and 10 days after exposure and compared to untreated controls. In none of the cell types examined a significant increase in melanin content or an increase in cell proliferation was observed. Additional treatment with the tyrosinase inhibitor alpha-methyl-p-tyrosine showed no significant effect either. Our results support the concept of a rather complex mechanism underlying the increased iris pigmentation after treatment with latanoprost.

Animals↗