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Biomedical subjects

T B Krasieva

Publications and source records attributed to T B Krasieva.

11 recordsLinked to original sources
PubMed2001

Fluorescence detection of cervical intraepithelial neoplasia for photodynamic therapy with the topical agents 5-aminolevulinic acid and benzoporphyrin-derivative monoacid ring.

OBJECTIVE: The aim of this study was to determine whether 2 photosensitizers, benzoporphyrin-derivative monoacid ring and 5-aminolevulinic acid, are selectively absorbed by dysplastic cervical cells after topical administration. STUDY DESIGN: This phase I clinical trial involved 18 women with biopsy-proven cervical intraepithelial neoplasia at the Beckman Laser Institute, Irvine, Calif. Colposcopically directed cervical biopsy specimens obtained after 1.5, 3, or 6 hours of exposure to a randomly assigned photosensitizer were evaluated for selective drug absorption with hematoxylin and eosin staining and fluorescence microscopy. RESULTS: After exposure to 5-aminolevulinic acid, cervical tissue showed maximal fluorescence in dysplastic cells relative to normal cells, with negligible stromal fluorescence. According to our detection methods benzoporphyrin-derivative monoacid ring demonstrated nonselective, diffusion-driven uptake, with fluorescence appearing in the superficial cells, followed by nonselective drug absorption in the remaining cells and stroma of the epithelium. CONCLUSION: Our data demonstrated selective absorption of 5-aminolevulinic acid by dysplastic cervical cells. This agent therefore represents a promising photosensitizing prodrug for the treatment of cervical intraepithelial neoplasia with photodynamic therapy.

Absorption↗
PubMed2000

Morphological study of the effects of CO2 laser emitted at 9.3 microm on human dentin.

OBJECTIVE: The purpose of this study was to investigate the effects of dentin ablation using a carbon dioxide (CO2) laser emitted at 9.3 microm by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). BACKGROUND DATA: There have been no reports on effects of CO2 laser irradiation emitted at 9.3 microm on dentin by SEM and CLSM. METHODS: Thirty extracted human teeth showing no clinical signs of caries were used. All teeth were horizontally sectioned to approximately 200 microm thickness and sections were irradiated using a 9.3 microm CO2 laser at different parameters as follows: 26 mJ [energy density (ED) 53.0 J/cm2] and 30 mJ (ED 61.1 J/cm2). After laser irradiation, samples were treated with sodium hypochlorite, stained using rhodamine-123, and observed with CLSM followed by SEM procedures. RESULTS: No craters or cracks were observed, but many small molten and rehardened particles were documented on the sample surface using SEM. Some small cracks were seen in the subsurface layer, and some patent dentinal tubules were detected using CLSM. CONCLUSION: These results suggest that laser irradiation at these parameters affected the sample surface only (less than 20 microm) and would be less harmful to thermal damage of dental pulp for dentin ablation.

Carbon Dioxide↗
PubMed2000

A decrease in membrane tension precedes successful cell-membrane repair.

We hypothesized that the requirement for Ca(2+)-dependent exocytosis in cell-membrane repair is to provide an adequate lowering of membrane tension to permit membrane resealing. We used laser tweezers to form membrane tethers and measured the force of those tethers to estimate the membrane tension of Swiss 3T3 fibroblasts after membrane disruption and during resealing. These measurements show that, for fibroblasts wounded in normal Ca(2+) Ringer's solution, the membrane tension decreased dramatically after the wounding and resealing coincided with a decrease of approximately 60% of control tether force values. However, the tension did not decrease if cells were wounded in a low Ca(2+) Ringer's solution that inhibited both membrane resealing and exocytosis. When cells were wounded twice in normal Ca(2+) Ringer's solution, decreases in tension at the second wound were 2.3 times faster than at the first wound, correlating well with twofold faster resealing rates for repeated wounds. The facilitated resealing to a second wound requires a new vesicle pool, which is generated via a protein kinase C (PKC)-dependent and brefeldin A (BFA)-sensitive process. Tension decrease at the second wound was slowed or inhibited by PKC inhibitor or BFA. Lowering membrane tension by cytochalasin D treatment could substitute for exocytosis and could restore membrane resealing in low Ca(2+) Ringer's solution.

3T3 Cells↗
PubMed1999

Highly selective targeting of ovarian cancer with the photosensitizer PEG-m-THPC in a rat model.

Photodynamic therapy (PDT) uses light to activate a photosensitizer that has been absorbed or retained preferentially by cancer cells after systemic administration. The first pegylated photosensitizer, tetrakis-(m-methoxypolyethylene glycol) derivative of 7,8-dihydro-5,10,15,20-tetrakis(3-hydroxyphenyl)-21,23-[H]-porphyrin (PEG-m-THPC), was evaluated to target selectively unresectable pelvic ovarian cancer bulks. Our goals were two-fold: (1) to establish an ovarian cancer model suitable for the development of debulking techniques and (2) to characterize the pharmacokinetics and tumor selectivity of PEG-m-THPC by fluorescence microscopy. NuTu-19 ovarian cancer cells were injected into the caudal part of the right psoas muscle of Fisher rats. Five weeks later, 30 mg/kg body weight of PEG-m-THPC was injected intravenously. Necropsy was performed between 4 and 10 days following drug application, and fluorescence of the tumor and various abdominal organs was measured. All rats developed bulky pelvic tumors with an average diameter of 2.6 cm (+/- 0.6 SD). Tumor masses were encompassing and infiltrating pelvic organs in a similar manner to ovarian cancers in humans. Fluorescence of cancer tissue was maximal 8-10 days following drug application. At 8 days, the tumor-to-tissue ratio was 40:1 (+/- 12 SE) for most abdominal organs. We conclude that this tumor model may be used for the study of new pelvic debulking techniques, and that the tumor selectivity of PEG-m-THPC is exceptionally high 8 days after drug application. Based on these data, we are currently developing a PDT-based minimally invasive debulking technique for advanced ovarian cancer.

Animals↗
PubMed1999

Preclinical study in cats of the pro-photosensitizer 5-aminolevulinic acid.

OBJECTIVE: To determine whether feline cells were able to convert 5-aminolevulinic acid (ALA) to protoporphyrin IX (PpIX) in vivo and in vitro, whether i.v. administration of ALA to healthy cats resulted in adverse effects, and whether PpIX accumulated in a squamous cell carcinoma (SCC) of a cat. ANIMALS: 4 healthy adult cats and 1 adult cat with a cutaneous SCC. PROCEDURE: In vitro production of PpIX was determined by incubating Crandell feline kidney cells with ALA. Effects of ALA administration and in vivo production of PpIX were determined by administering ALA (100, 200, or 400 mg/kg of body weight) to healthy cats and collecting skin biopsy specimens for up to 24 hours after drug administration. Blood samples were collected for CBC and serum biochemical analyses, and necropsies were performed. Accumulation of PpIX in a SCC was determined by treating a cat with a facial SCC with ALA and collecting specimens of the tumor and adjacent grossly normal skin. RESULTS: Incubation of ALA with feline cells resulted in time- and dose-dependent cytoplasmic accumulation of PpIX in vitro. After i.v. ALA administration, PpIX was detected in all tissues examined, with the highest fluorescence intensity in epithelia and in squamous cell carcinoma. The tumor-to-skin fluorescence intensity ratio was 5. All cats developed hepatotoxicoses. CONCLUSIONS AND CLINICAL RELEVANCE: Results from this limited number of cats suggest that ALA may be a useful photosensitizer in cats, but that doses > 100 mg/kg, i.v., may not be safe.

Aminolevulinic Acid↗
PubMed1998

Laser-micropipet combination for single-cell analysis.

Due to its potential for exquisite mass detection limits and resolving power, capillary electrophoresis is used for biochemical measurements on single cells; however, accurate measurements of many physiological parameters require sampling strategies that are considerably faster than those presently available. We have developed a laser-based technique to lyse single, adherent, mammalian cells on millisecond time scales. The cellular contents are then introduced into a capillary where electrophoretic separation and detection are performed. Improved temporal resolution of biological measurements results from the extremely rapid lysis made possible by this method. Additionally, the cell is not perturbed by mechanical or electrical stresses prior to sampling. Such disturbances can alter cellular physiology, resulting in inaccurate measurements. The fast cell lysis, the absence of cellular stresses prior to lysis, and the application to adherent mammalian cells are significant refinements to CE-based measurements on single cells. With this laser-micropipet combination, it will be possible to measure the intracellular concentration of molecules that change on subsecond to second time scales, for example, substrates of many cellular enzymes.

Animals↗
PubMed1998

Uptake of the photosensitizer benzoporphyrin derivative in human endometrium after topical application in vivo.

STUDY OBJECTIVE: To determine both the time leading to maximum endometrial drug uptake and distribution of the photosensitizer benzoporphyrin derivative-monoacid ring A (BPD-MA) after intrauterine instillation (Canadian Task Force classification ). DESIGN: Assessment of histology specimens (Canadian Task Force classification I). SETTING: University-based facility. PATIENTS: Twenty-two women scheduled for hysterectomy. INTERVENTIONS: We instilled 1.5 ml of a 2 mg/ml of BPD-MA-Hyskon solution into the uterine cavity of 22 women before hysterectomy. The fluorescence induced was measured by fluorescence microscopy on frozen sections of uterine samples from 20 of 22 patients. Systemic uptake of BPD-MA was determined in plasma of six patients by spectrofluorometry. MEASUREMENTS AND MAIN RESULTS: The BPD-MA-induced fluorescence was maximum 1 hour after instillation, with significantly higher uptake in endometrial glands than in underlying stroma. Hormonal endometrial stimulation correlated with fluorescence intensity: atrophy < secretory phase < proliferative phase. Strongest fluorescence was seen in endometrial cancer. Drug uptake by endometrial glands was found at a depth of 2 mm from the surface. Systemic uptake of BPD-MA was under the detection level of 2 ng/ml after application. CONCLUSION: Fluorescence in human endometrial glands suggests that selective destruction of human endometrium with photodynamic therapy may be possible 1 hour after topical application of BPD-MA for benign and malignant lesions. No systemic drug uptake, side effects, or major technical difficulties were detected. Limited penetration of the drug and selective uptake by endometrial glands provided a high degree of safety for endometrial ablation.

Administration, Topical↗
PubMed1997

In vivo fluorescence detection of ovarian cancer in the NuTu-19 epithelial ovarian cancer animal model using 5-aminolevulinic acid (ALA).

The purpose of this study was to determine whether in vivo fluorescence detection of protoporphyrin IX (PpIX) could be used to identify intraperitoneal micrometastases of epithelial ovarian carcinoma after application of 5-aminolevulinic acid (ALA). ALA was applied intraperitoneal at different concentrations (25, 50, and 100 mg/kg) and iv (100 mg/kg) to immunocompetent Fischer 344 rats bearing a syngeneic epithelial ovarian carcinoma. At different time intervals after ALA administration (1.5, 3, and 6 hr) the peritoneal cavity was illuminated with ultraviolet (uv) light. In vivo fluorescence of PpIX initially was determined by direct visualization. Subsequently ex vivo measurements were made with a slow-scan, thermoelectrically cooled CCD camera. Red in vivo fluorescence was observed in ovarian micrometastases smaller than 0.5 mm in 100% of the ALA-administered animals independent of time interval, drug concentration, or route of administration. The intensity of the fluorescence was concentration dependent as strong fluorescence was consistently found only above 25 mg/kg ALA. Ex vivo tumor to peritoneum fluorescence yield peaked 3 hr after administration of a 100 mg/kg intraperitoneal dose. Direct visualization of in vivo fluorescence after ALA application may improve the detection of intraperitoneal ovarian cancer micrometastases.

Aminolevulinic Acid↗
PubMed1996

Fluorescence imaging studies for the disposition of daunorubicin liposomes (DaunoXome) within tumor tissue.

Unilamellar liposomes that retain their contents in the systemic circulation can alter the pharmacokinetics of anticancer agents in favorable ways. It has long been recognized that certain liposome compositions may increase the local drug concentration substantially above that achievable with a free drug. We report here that liposomes can alter the in vivo disposition of an entrapped drug not only on a macroscopic but also on a microscopic scale. We show through in vitro studies that intact liposomes composed of distearoylphosphatidylcholine and cholesterol and containing daunorubicin (DaunoXome) are taken up into P1798 tumor cells. These liposomes produce an enhanced cytotoxicity relative to the free drug for incubation times longer than about 8 h. For in vivo studies, we developed and used a noninvasive fluorescence imaging technique to follow the accumulation of liposomal daunorubicin within murine tumors. With this method, we show that the maximum concentration of the available liposomal drug in tumors exceeds that of the free drug, and additionally, liposomal daunorubicin persists at high levels for several days. Total liposome-delivered drug fluorescence from whole tumor extracts peaks at about 8 h. In comparison, the fluorescence intensity of daunorubicin demonstrate persistent high levels of daunorubicin fluorescence within cells and throughout the tumor masses. Free daunorubicin, in contrast, transiently achieves modest levels of fluorescence and rapidly drops to background within a few h. These results indicate distinct mechanisms for the localization of free and liposomal daunorubicin, suggesting that liposmal daunorubicin can provide sustained intracellular levels of the drug within the tumor.

Animals↗
PubMed1996

Polarity of T cell shape, motility, and sensitivity to antigen.

T cell activation requires contact with APCs. We used optical techniques to demonstrate T cell polarity on the basis of shape, motility, and localized sensitivity to antigen. An intracellular Ca2+ clamp showed that T cell shape and motility are extremely sensitive to changes in [Ca2+]i (Kd = 200 nM), with immobilization and rounding occurring via a calcineurin-independent pathway. Ca2+ dependent immobilization prolonged T cell contact with the antigen-presenting B cell; buffering the [Ca2+]i signal prevented the formation of stable cell pairs. Optical tweezers revealed spatial T cell sensitivity to antigen by controlling placement on the T cell surface of either B cells or alpha-CD3 MAb-coated beads. T cells were 4-fold more sensitive to contact made at the leading edge of the T cell compared with the tail. We conclude that motile T cells are polarized antigen sensors that respond physically to [Ca2+]i signals to stabilize their interaction with APCs.

Animals↗