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Biomedical subjects

H Walt

Publications and source records attributed to H Walt.

At least 37 records · Page 2Linked to original sources
PubMed1998

Enhanced photodynamic effects using fractionated laser light.

Photodynamic eradication of tumour cells depends on the presence of a photosensitizer and light delivery to the cells. The present study investigated the influence of fractionated light (on-off mode) on cell killing as documented by a colony-forming assay. Photosensitizers were m-THPC (ethanol soluble, Foscan) and m-THPC-MD (water soluble, both from Scotia Pharmaceuticals, Guildford, UK). Fractionated laser light at a wavelength of 652 nm with a light duration of 0.05 s was more effective than continuous illumination at the same power density for both photosensitizers. We propose that fractionated laser light is more toxic due to short phases of recovery during the dark intervals, probably resulting in more singlet oxygen under these conditions. By use of Foscan, for example, and fractionated laser light, a similar effect is expected for the treatment of solid tumours. In this case we expect improvements in photodynamic therapy (PDT) for patients by lowering the concentrations of photosensitizer and/or by reducing the applied light dose.

Antineoplastic Agents↗
PubMed1998

The effect of interferon-gamma and tumor necrosis factor-alpha on the expression of ICAM-1 and HLA-DR molecules on cells of a human germ cell neoplasm and their susceptibility to lysis by lymphokine-activated killer cells.

The ICAM-1 molecule plays a role in the interaction of NK cells with a variety of tumor cells, including carcinoma, melanoma and glioblastoma cells. In the present study, we analyzed the effect of IFN-gamma and TNF-alpha on both the expression of HLA-DR and ICAM-1 molecules on HGCN (Germa-2), and on their susceptibility to lysis by LAK cells. Our results show that 1,000 U/ml IFN-gamma induced a substantial increase in the expression of both ICAM-1 molecules and HLA-DR on the cell surface, while the effect of TNF-alpha on the expression of these molecules was substantially less prominent. When Germa-2 cells, previously exposed to 1,000 U/ml IFN-gamma, were employed as target cells in a 4-hour 51Cr release assay, a statistically significant increase in the lysis by LAK cells was noted. These results show that in the presence of IFN-gamma, Germa-2 tumor cells undergo modulation which affects both the expression of ICAM-1 and HLA-DR molecules as well as their susceptibility to lysis by LAK cells.

Cytotoxicity Tests, Immunologic↗
PubMed1998

Aspects of three-dimensional chromosome reorganization during the onset of human male meiotic prophase.

The three-dimensional morphology and distribution of human chromosomes 3 were studied in nuclei of spermatogonia and spermatocytes I from formaldehyde-fixed human testis sections. Chromosome arms, pericentromeres and telomeric regions were painted by a three-color, five-probe fluorescence in situ hybridization protocol. Light optical serial sections of premeiotic and meiotic nuclei obtained by confocal laser scanning microscopy revealed that premeiotic chromosomes 3 are separate from each other and occupy variably shaped territories, which are sectored in distinct 3 p- and q-arm domains. Three-dimensional reconstructions of the painted chromosome domains by a Voronoi tessellation approach showed that mean chromosome volumes did not differ significantly among the premeiotic and meiotic stages investigated. A significant increase in surface area and reduction of dimensionless 'roundness factor' estimates of arm domains indicated that the restructuring of spatially separate chromosome territories initiates during preleptotene. Telomeric regions, which in meiotic stem cells located predominantly in arm-domain chromatin, showed a redistribution towards the domain surface during this stage. At leptotene homologues were generally misaligned and displayed intimate intermingling of non-homologous chromatin. Pairing initiated at the ends of bent zygotene chromosomes, which displayed a complex surface structure with discernible sister chromatids. The results indicate that, in mammals, homology search is executed during leptotene, after remodeling of chromosome territories.

Chromatin↗
PubMed1998

m-THPC-mediated photodynamic therapy (PDT) does not induce resistance to chemotherapy, radiotherapy or PDT on human breast cancer cells in vitro.

Photodynamic therapy (PDT) uses laser light to activate a photosensitizer that has been absorbed preferentially by cancer cells after systemic administration. A phototoxic reaction ensues resulting in cell death and tissue necrosis. Some cells, however, may survive PDT. This study was performed to determine if surviving human breast cancer cells (MCF-7) can become resistant to PDT, chemotherapy or radiotherapy. The MCF-7 cells were cultured under standard conditions prior to being exposed to the photosensitizer, 5,10,15,20-meta-tetra(hydroxyphenyl)chlorin (m-THPC), for 24 h and then irradiated with laser light (652 nm). Surviving cells were allowed to regrow by allowing a 2 week interval between each additional PDT. After the third and final treatment, colony formation assays were used to evaluate the sensitivity of cultured cells to ionizing radiation and PDT and the ATP cell viability assay tested in vitro chemosensitivity. Flow cytometry was used to analyze the cell cycle. No alterations in the cell cycle were observed after three cycles of PDT with m-THPC. Similar responses to chemotherapy and ionizing radiation were seen in control and treatment groups. The m-THPC-sensitized PDT did not induce resistance to subsequent cycles of PDT, chemo- or radiotherapy. Photodynamic therapy with m-THPC may represent a novel adjunctive treatment of breast cancer that may be combined with surgery, chemotherapy or ionizing radiation.

Antineoplastic Agents↗
PubMed1997

Photosensitization of isolated rat liver mitochondria by tetra(m-hydroxyphenyl)chlorin.

Tetra(m-hydroxyphenyl)chlorin (mTHPC) is used as a photosensitizer in photodynamic therapy (PDT), a novel modality for cancer treatment. Since little is known about mTHPC-mediated damage in vitro, we chose isolated rat liver mitochondria as a model system to study its photodynamic effects. Incubation of isolated mitochondria with mTHPC plus irradiation with light of a wavelength of 652 nm resulted in protein oxidation and lipid peroxidation, as measured by the mitochondrial content of carbonyl groups and thiobarbituric acid-reactive substances, respectively. Type I and type II photochemical reactions contribute to this oxidative damage as shown by the use of scavengers. Photodynamically treated mitochondria had a reduced membrane potential, and their Ca2+ uptake was impaired. Oxygen consumption of complex I of the respiratory chain was stimulated at a low concentration of mTHPC plus irradiation, but decreased at higher concentrations, whereas oxygen consumption at complex II and IV decreased with all mTHPC concentrations offered. No mitochondrial changes were seen with mTHPC in the absence of irradiation. Our results confirm the sensitivity of mitochondria to PDT and may help to understand the mechanisms by which PDT using mTHPC kills cells.

Adenosine Diphosphate↗
PubMed1997

In vitro effects and localisation of the photosensitizers m-THPC and m-THPC MD on carcinoma cells of the human breast (MCF-7) and Chinese hamster fibroblasts (V-79).

BACKGROUND AND OBJECTIVE: Photodynamic therapy (PDT) is the combination of a photosensitizer with laser light to induce preferential destruction of malignant cells. In this study two new photosensitizers--5,10,15,20-meta-tetra(hydroxyphenyl) chlorin (m-THPC) and m-THPC MethoxyPEG2000 derivative (m-THPC MD)--were tested, both for their dark toxicity, i.e., cytotoxicity in the absence of light, and for their light-induced cytotoxicity in mammalian cell cultures. STUDY DESIGN/MATERIALS AND METHODS: Cell lines used were MCF-7 (human breast carcinoma) and V-79 (Chinese hamster lung fibroblast). After cultivation under standard conditions, cells were administered the photosensitizers and 24 hr later exposed to various energy levels of laser light at a wavelength of 652 nm. Cell survival was monitored using a clonogenic assay and was expressed as the surviving fraction of the untreated control. RESULTS: Up to an m-THPC concentration of 1 microgram/ml, no dark toxicity was observed; at higher concentrations a rapid fall in survival occurred. m-THPC MD showed no dark toxicity up to 100 micrograms/ml. In vitro m-THPC was approximately 10 times more cytotoxic than m-THPC MD. The MCF-7 and V-79 cell lines displayed similar responses to PDT. CONCLUSIONS: Both m-THPC and m-THPC MD are very efficient photosensitizers in vitro. Up to the therapeutic dose, neither exhibited dark toxicity. There is clinical relevance of the photosensitizers by a large therapeutic index.

Animals↗
PubMed1997

Premenopausal node-negative breast cancer: may adjuvant chemotherapy be indicated by the analysis of nuclear DNA dynamics?

The management of premenopausal node-negative breast cancer patients is discussed controversially. Accurate cellular as well as biochemical markers are essential for this cancer group to identify high risk patients needing adjuvant chemotherapy. In the present study, flow cytometric DNA analysis (DNA-ploidy status, DNA-index, S-phase fraction, S+(G2+M)-phase fraction) and clinico-pathological variables (clinical stage, tumor size, receptor status, age, histological type and grade) as prognostic factors were determined on paraffin-embedded tumors to predict overall survival (OS) and disease-free survival (DFS). Median observation time was 6.1 years (n = 57). S+(G2+M)-phase fraction was the only flow cytometric DNA predictor of overall survival in the univariate analysis (log-rank test): As compared to the patients with lower S+(G2+M)-phase fraction (< or = 9.3%), patients with S+(G2+M)-phase fraction greater than 9.3% had shorter survival (P = 0.039). Of all the clinico-pathological parameters analyzed (univariate analysis), the survival time was found to be longer when estrogen- and/or progesterone-receptor status was positive (overall survival: P = 0.039; disease-free survival: P = 0.017) and the histological grade was low (overall survival: I + II vs III: P = 0.024; I vs II vs III: P = 0.046). In the multivariate analysis, receptor status was the strongest predictor for overall and disease-free survival. These results suggest that S+(G2+M)-phase fraction in premenopausal node-negative breast cancer could be an additional valuable prognostic factor to classify high risk breast cancer patients needing adjuvant chemotherapy.

Adult↗
PubMed1997

[Primary ciliary dyskinesia in situs inversus without bronchiectasis].

BACKGROUND: In adults suffering from Kartagener's syndrome-which is found in 50% of patients with primary ciliary dyskinesia (PCD)-bronchiectasis is still one of three typical clinical features. In this condition it is caused by chronic bacterial inflammation as a result of impaired mucociliary clearance in congenital ciliary dysfunction. Little information is available on the incidence, age-related development and prophylactic therapy of bronchiectasis in children suffering from PCD. CASE REPORT/RESULTS: We describe the case of a 2-year old boy with clinical features of Kartagener's syndrome who showed impaired ciliary motility and typical ultrastructural defects of PCD. Bronchiectasis was excluded by bronchography. CONCLUSIONS: The diagnosis of PCD implies disturbed ciliary motility and abnormal ultrastructure of the cilia. In 50% of cases PCD is associated with situs inversus and is then referred to as kartagener's syndrome, whereas situs inversus itself does not define Kartagener's syndrome. Bronchiectasis is not necessarily present in children with PCD. Physiotherapy, inhalations, vaccinations and early antibiotic treatment may be of prophylactic value in preventing bronchiectasis. Early start of the life-long treatment depends on early diagnosis which should be based on well-defined criteria.

Aging↗
PubMed1996

[Primary ciliary dyskinesia, immotile cilia syndrome, and Kartagener syndrome: diagnostic criteria].

Primary ciliary dyskinesia is the generic term for a heterogeneous group of inherited diseases in which ciliary ultrastructure is defective and as a consequence ciliary motility is disturbed. An international consensus on the diagnostic criteria has not yet been reached. This paper reviews some recent findings which are useful in the diagnosis of the disease and attempts to establish the best diagnostic criteria. The marker symptoms are chronic bronchitis, otitis, and sinusitis since childhood. Additionally, one or more of the following criteria must be present: Kartagener syndrome, a dextrocardia situation, markedly reduced frequency in ciliary motility, or an essential ultrastructure deviation in more than 20% of the square cuts (e.g. reduced number of dynein arms). Biopsy of the ciliated mucosa is usually required for the above criteria and is studied by vital microscopy and transmission electron microscopy. Primary and secondary ciliary dyskinesia can be distinguished by these methods and the rare case of PCD without ultrastructure deficiency ruled out. In special cases a cell culture is recommended for the diagnosis. Practical aspects of the sampling methods and diagnostic pitfalls are reviewed.

Cilia↗
PubMed1996

[Benzoporphyrin derivative mono acid for photodynamic therapy of the endometrium].

The aim was to study the impact of photodynamic therapy (PDT) on the endometrium after local intrauterine application of photosensitiser (Ps) and laser light without sensitising the skin. To our knowledge Benzoporphyrin Derivative Mono Acid (BPD) was used for the first time for this purpose in the rat model. The advantage of using BPD is the fact that light of 690 nm (maximum absorption) penetrates deeper into tissue and shows less absorption by haemoglobin. Low-light level tissue fluorescence imaging revealed a distinct positive endometrium-to-myometrium ratio within the first 12 hours. Relative fluorescence was highest in the endometrial glands and lowest in the myometrium. After 12 hours the intensity of fluorescence levelled off in all compartments and values of the glands approached close to those of the other layers. REPRODUCTIVE PERFORMANCE AFTER PDT: There was a significant difference in nidations (p < 0.03) in the treated left uterine horn as compared to the untreated right horn and the control animals (light/no drug and drug/no light). HISTOLOGICAL CHANGES: Following PDT a marked atrophy of the endometrial layer was observed in most animals leaving just a single cell epithelial layer covering the myometrium. SKIN PHOTOSENSITIVITY: None of the animals showed any alterations in the light treated skin area at any time. These promising results show that PDT of the endometrium is possible after topical application of the photosensitising drug and the laser light without provoking skin sensitivity.

Animals↗
PubMed1995

Assessment of effect of photosensitizers on cytotoxicity of photodynamic therapy in human breast cancer cell cultures.

BACKGROUND: Photodynamic therapy (PDT) might be of clinical value for patients with breast cancer with local recurrences or metastasis. However, there is a need for improved photosensitizers that are effective in combination with laser light and have few, if any, side-effects. We evaluated in vitro the effectiveness of a second generation photosensitizer by testing the influence of laser light on cell cultures of a human breast carcinoma cell line, incubated with meta-tetrahydroxyphenylchlorin (m-THPC) (= Temoporfin). EXPERIMENTAL DESIGN: Five thousand MCF-7 cells were plated in 96-well plates. Forty-eight hours before laser treatment, the cells were plated to achieve a monolayer configuration. Twenty-four hours after plating, they were incubated with m-THPC. On day 6 after treatment with m-THPC we lysed the cells to extract the intracellular ATP that correlates with the number of living cells. The ATP-CVA was used to assess the cytotoxicity of the tested photosensitizer m-THPC at various concentrations and the relevant laser light alone prior to their combination after six days of culture. RESULTS: We found a dose-response for m-THPC alone ranging from 2 to 16 micrograms/ml. The calculated inhibition concentration to produce 50% cell kill (IC50) was 4.55 micrograms/ml. We also observed a very low cytotoxicity for laser irradiation alone but a very strong cell kill for the combination of m-THPC together with laser light. CONCLUSIONS: PDT gave almost total cell kill at m-THPC concentrations that are not toxic in vitro.

Adenosine Triphosphate↗
PubMed1995

Differentiation potential of ovarian dysgerminoma: an immunohistochemical study of 15 cases.

An immunohistochemical study of 15 ovarian formalin-fixed, paraffin-embedded dysgerminomas showed positive staining of tumor cells for vimentin in all cases. Ten dysgerminomas stained for cytokeratin 18. Desmin positivity of single tumor cells was detected in four dysgerminomas. Glial fibrillary acidic protein was present in two tumors. Prominent human beta chorionic gonadotropin staining was seen in one tumor. S-100 protein was found in two and carcinoembryonic antigen in one of the dysgerminomas. Placental alkaline phosphatase was present in 12 of the 15 tumors studied. The heterogeneity of the cytoskeletal profile and of other markers showed some similarities to our previously published results on testicular seminomas. Thus, in contrast to previous concepts, dysgerminoma, as is the case with its testicular counterpart the seminoma, appears to be capable of further differentiation, albeit at a primitive level. Our observations also may help to elucidate the relationship between dysgerminoma and other nondysgerminomatous ovarian germ cell tumors, and may be of help in the differential diagnosis with poorly differentiated carcinoma, ovarian lymphoma, or other germ cell tumors.

Biomarkers, Tumor↗
PubMed1995

[The combined use of photodynamic therapy with ionizing radiation on breast carcinoma cells in vitro].

PURPOSE: The photodynamic therapy is a technique by which the tumor cells are selectively sensitized to destruction by light of an appropriate wavelength. The aim of this work is to analyze the biological effectiveness of photochemical reactions induced by laser light in tumor cells exposed to photosensitizers. MATERIAL AND METHODS: The toxicity of the 2 photosensitizers zinc phthalocyanine (ZnPC) and meso-tetrahydroxyphenylchlorine (m-THPC) as well as the biological effect of the combination of sensitizers with laser light were tested in vitro by means of a colony forming assay. In addition, the influence on the photodynamic reaction of a previous exposure of the tumor cells to ionizing radiation has been tested. RESULTS: For both sensitizers doses of 5 micrograms per milliliter of culture medium showed low toxicity, i.e. the survival of the treated cells exceeded 90%. For laser treatments the dose permitting 90% survival was determined to be around 10 J/cm2. With these doses, the combined application of photosensitizers and laser light proved to be very effective and resulted in a nearly complete reduction of survival. As expected, irradiation of the cells with doses of 1 and 2 Gy of X-rays reduced the survival to 66 and 47%, respectively, compared to untreated controls. Cells surviving such treatment showed no changes either in the response to treatments with photosensitizers or to combined applications of photosensitizers and laser light. CONCLUSION: The effects of photodynamic treatment by ionizing radiation seem to be additive and independent of each other. So, our preliminary results are quite encouraging and point out the need of further detailed studies in view of the intended clinical application of this new kind of a local treatment.

Breast Neoplasms↗
PubMed1995

Correlation of microscopic phenotype with genotype in a formalin-fixed, paraffin-embedded testicular germ cell tumor with universal DNA amplification, comparative genomic hybridization, and interphase cytogenetics.

We present a strategy for the evaluation of numerical copy number changes of DNA segments within a solid tumor genome that allows the correlation of microscopic phenotype with genotype in formalin-fixed, paraffin-embedded tumor material. Cells from a human testicular germ cell tumor and adjacent tissue areas with normal seminiferous tubules were selected separately from microscopically analyzed histological tissue sections, and DNA was extracted from the selected areas. After universal DNA amplification, the amplification products were subjected to comparative genomic hybridization. The results confirmed balanced chromosome copy numbers for the normal tissue area, although the analysis of the tumor tissue area revealed numerous gains and losses of chromosome segments. The comparative genomic hybridization results were used to select DNA probes for interphase cytogenetics on serial sections. We conclude that this technique allows the screening of selected tissue areas for numerical DNA alterations, thus enabling a direct phenotype-genotype comparison.

Adult↗
PubMed1993

Chimeric human and mouse spheroids.

We investigated structures resembling embryoid bodies (EBs), grown intraperitoneally in nude mice after the injection of xenografted human teratocarcinoma cells. Following in situ hybridization of paraffin sections containing these EB-like structures with either human or mouse total genomic DNA, two species-specific types of cell nuclei were localized. Tumor cells of human origin were found centrally but flattened normal mouse cells formed an outer coat. Thus these spheric structures are of bispecies origin and do not meet the definition of EBs. For a clear distinction from EBs and spheroids, we termed these structures chimeric spheroids.

Animals↗
PubMed1993

Experimental testicular germ cell tumorigenesis in mouse strains with and without spontaneous tumours differs from development of germ cell tumours of the adult human testis.

The aim of this study was to undertake a morphological analysis of the earliest stages of experimentally induced (by genital ridge grafting) germ cell tumours in mouse strains with (129/Sv-ter) and without (MA) spontaneous tumorigenesis. Genital ridges from fetuses aged 12 or 13 days from 129/Sv-ter and MA were transplanted into the testes of adult 129/Sv-ter. The results show clearly that experimentally induced carcinoma-in-situ in mouse testes differs considerably from its human counterpart, found in patients with and without testicular germ cell tumours, and considered to be the precursor for all kinds of germ cell tumours of the adult testis apart from spermatocytic seminoma. The results indicate that development of testicular germ cell tumours is different in man and the mouse.

Adult↗
PubMed1991

Correlative histological and ultrastructural study of unusual changes in human tracheobronchial epithelium.

In tracheostomy patients with chronic bronchitis, scanning electron microscopy reveals detailed surface changes in the tracheobronchial mucosa. The principle of intermicroscopic correlation, i.e., the sequential examination of a specimen by different microscopic procedures, is illustrated with giant cilia. After re-embedding the scanning electron microscopic specimens and precisely locating a ciliary convolution by light microscopy in semithin section, the giant cilia were studied in ultrathin sections by transmission electron microscopy. The cilia were shown to be at least 9 microns long (normal ciliary length = 4-6 microns). Central and peripheral microtubular axonemal structures with a 9 + 2 arrangement were clearly shown in both longitudinal and cross section. Giant cilia, thus, most closely resemble outgrowths of normal cilia. If they are motile at all, they seem unlikely to effect a transport function coordinated in direction and time.

Bronchi↗