Biomedical subjects

M Motamedi

Publications and source records attributed to M Motamedi.

At least 37 records · Page 2Linked to original sources

PubMed1999

Detection of pathological zinc accumulation in neurons: methods for autopsy, biopsy, and cultured tissue.

It has been repeatedly shown that synaptically released zinc contributes to excitotoxic neuronal injury in ischemia, epilepsy, and mechanical head trauma. Such zinc-induced injury leaves an unmistakable "footprint" in the injured neurons, allowing an easy and unambiguous postmortem diagnosis. This footprint is the presence of weakly bound, histochemically reactive zinc in the cytoplasm of the perikaryon and proximal dendrites. Such staining appears to be a necessary and sufficient marker for zinc-induced neuronal injury. Here we show how to prepare and stain tissue from biopsy, autopsy, or experimental animal sources for maximal contrast and visibility of zinc-injured neurons.

Animals↗

PubMed1998

Delta-aminolevulinic acid-mediated photosensitization of prostate cell lines: implication for photodynamic therapy of prostate cancer.

BACKGROUND: Delta-aminolevulinic acid (ALA)-mediated photodynamic therapy (PDT) is currently being investigated for the treatment of prostate diseases. In this study, we evaluate 1) the in vitro production of protoporphyrin IX (PPIX) (the active photosensitizing agent of ALA-mediated PDT) by two different prostate cancer cell lines (LNCaP and PC-3) and a benign, modified, prostatic cell line (TP-2), and 2) the extent of PDT-induced cell injury, as determined by electron microscopy (EM) and cell survival. METHODS: The cell lines were assigned into four treatment groups: group 1, control, no ALA and no light irradiation; group 2, dark control, ALA only; group 3, light control, radiation only; and group 4, PDT, ALA followed by irradiation (630 nm, 3 joules/cm2). The experiments were performed in triplicate. ALA concentration was 50 microg/ml of media in all instances. RESULTS: Following incubation with ALA, PPIX production was significantly increased in the three cell lines studied, and more notably in the PC-3 cell line. Compared to controls, EM and cell survival studies demonstrated significant mitochondrial damage and decreased survival, respectively, in the cells treated with PDT. This was also more evident in the PC-3 cell line. CONCLUSIONS: Our results demonstrate that prostate cells differ in their response to ALA-mediated PDT. This response appears to depend on the intracellular production of PPIX and the cell type, i.e., on the functional and structural characteristics of the cell mitochondria. In addition, our results suggest that PDT might be effective at killing prostate cancer cells.

Aminolevulinic Acid↗

PubMed1998

Laser assisted soldering: microdroplet accumulation with a microjet device.

BACKGROUND AND OBJECTIVE: We investigated the feasibility of a microjet to dispense protein solder for laser assisted soldering. STUDY DESIGN: Successive micro solder droplets were deposited on rat dermis and bovine intima specimens. Fixed laser exposure was synchronized with the jetting of each droplet. After photocoagulation, each specimen was cut into two halves at the center of solder coagulum. One half was fixed immediately, while the other half was soaked in phosphate-buffered saline for a designated hydration period before fixation (1 hour, 1, 2, and 7 days). After each hydration period, all tissue specimens were prepared for scanning electron microscopy (SEM). RESULTS: Stable solder coagulum was created by successive photocoagulation of microdroplets even after the soldered tissue exposed to 1 week of hydration. CONCLUSIONS: This preliminary study suggested that tissue soldering with successive microdroplets is feasible even with fixed laser parameters without active feedback control.

Animals↗

PubMed1998

Cardioprotection by local heating: improved myocardial salvage after ischemia and reperfusion.

BACKGROUND: Previous studies have shown that expression of the inducible 70-kD heat-shock protein (HSP72) by whole-body hyperthermia is associated with protection against ischemia-reperfusion injury. To develop techniques for regional elevation of heat-shock proteins that prevent extracardiac sequelae during whole-body hyperthermia, we sought to determine if local heating of the heart in vivo provides protection against ischemia-reperfusion injury in the rat. METHODS: A thermal probe was used to locally heat rat hearts at two adjacent sites on the epicardial surface of the left ventricle. Rats were subjected to either 30 minutes of sham surgery (control; n = 10) or two local applications of the probe at 42.5 degrees to 43.5 degrees C for 15 minutes each (n = 9). After 4 hours, rats were subjected to 30 minutes of regional ischemia followed by 120 minutes of reperfusion. Hearts were removed and area at risk and infarct area were determined. RESULTS: Localized heat stress resulted in a significant limitation of infarct size in heat-treated animals versus controls (mean +/- standard error of the mean infarct area/area at risk = 4.3% +/- 0.85 versus 19.2% +/- 3.4%; p < 0.005). Western blot experiments confirmed elevated HSP72 expression in left (heated) and right (nonheated) ventricular samples from treated animals (n = 6; left ventricular = 5.5-fold; right ventricular = 3.7-fold) compared with sham-operated controls. Controls treated with the probe at 37 degrees C (n = 4) showed no increases in HSP72. CONCLUSIONS: Local heating of the heart is associated with elevated levels of HSP72 and improved myocardial salvage. The increase in expression of HSP72 is not limited to the heated region, but extends into nonheated regions of the heart as well. This may lead to the development of new techniques that improve methods of myocardial revascularization and heart transplantation procedures.

Analysis of Variance↗

PubMed1998

Heat shock improves recovery and provides protection against global ischemia after hypothermic storage.

BACKGROUND: Improved methods of donor heart preparation before preservation could allow for prolonged storage and permit remote procurement of these organs. Previous studies have shown that overexpression of heat-shock protein 72 provides protection against ischemic cardiac damage. We sought to determine whether rats subjected to heat stress with only 6-hour recovery could acquire protection to a subsequent heart storage for 12 hours at 4 degrees C. METHODS: Three groups of animals (n = 10 each) were studied: control, sham-treated, and heat-shocked rats (whole-body hyperthermia 42 degrees C for 15 minutes). After 12-hour cold ischemia hearts were reperfused on a Langendorff column. To confirm any differences in functional recovery, hearts were then subjected to an additional 15-minute period of warm global ischemia after which function and lactate dehydrogenase enzyme leakage were measured. RESULTS: Heat-shocked animals showed marked improvements compared with controls in left ventricular developed pressure (63+/-4 mm Hg versus 44+/-4 mm Hg, p<0.05) heart rate x developed pressure (13,883+/-1,174 beats per minute x mm Hg versus 8,492+/-1,564 beats per minute x mm Hg, p<0.05), rate of ventricular pressure increase (1,912+/-112 mm Hg/second versus 1,215+/-162 mm Hg/second, p<0.005), rate of ventricular pressure decrease (1,258+/-89 mm Hg/second versus 774+/-106 mm Hg/second, p<0.005). Diastolic compliance and lactate dehydrogenase release were improved in heatshocked animals compared with controls and sham-treated animals. Differences between heat-shocked animals and control or sham-treated animals were further increased after the additional 15-minute period of warm ischemia. Western blot experiments confirmed increased heat-shock protein 72 levels in heat-shocked animals (>threefold) compared with sham-treated animals and controls. CONCLUSIONS: Heat shock 6 hours before heart removal resulted in marked expression of heat-shock protein 72 and protected isolated rat hearts by increased functional recovery and decreased cellular necrosis after 12-hour cold ischemia in a protocol mimicking that of heart preservation for transplantation. Protection was further confirmed after an additional 15-minute period of warm ischemia.

Animals↗

PubMed1998

Desulfovibrio aespoeensis sp. nov., a mesophilic sulfate-reducing bacterium from deep groundwater at Aspö hard rock laboratory, Sweden.

A sulfate-reducing bacterium, strain Aspo-2, was isolated from granitic groundwater sampled at a depth of 600 m. This and other strains of SRB frequently occur in the deep granitic rock aquifers studied. On the basis of its morphological, physiological and genotypical properties, and its unique habitat, we propose strain Aspo-2 as a new species of the genus Desulfovibrio, Desulfovibrio aespoeensis (DSM 10631T).

Cell Wall↗

PubMed1998

Noninvasive assessment of the hydration gradient across the cornea using confocal Raman spectroscopy.

PURPOSE: The feasibility of Raman spectroscopy for the noninvasive assessment of axial corneal hydration was investigated. METHODS: A scanning confocal Raman spectroscopy system, with an axial resolution of 50 microns, was used to assess noninvasively the water (OH-bond) to protein (CH-bond) ratio as a measure of the hydration in collagen-based phantom media and rabbit corneas. RESULTS: Raman spectra with high signal-to-noise ratios were obtained under in vitro and in vivo conditions within a range of corneal hydration (H = 0.0-8.3 mg water/mg dry wt). The Raman intensity ratio OH/CH showed a strong correlation with the hydration of the phantom medium (R2 > 0.99) and the rabbit corneas (R2 > 0.95). A degree of reproducibility was seen in measurements performed at a specific depth within the cornea (SD = 1.2%-2.7%). Quantitatively, the spatially resolved corneal water content, as assessed with our method, showed an increasing gradient from the anterior to the posterior region, with a difference of approximately 0.9. Significant qualitative differences in the axial hydration gradient were observed between the in vitro and in vivo situation, caused by the presence of an intact tear-film in vivo. Characterization of the axial corneal hydration using Raman spectroscopy provided a reliable estimation of total corneal hydration compared with conventional measurements using pachymetry and lyophilization. CONCLUSIONS: The proposed noninvasive confocal Raman spectroscopic technique has the potential to assess the axial corneal water gradient with a degree of sensitivity and reproducibility.

Animals↗

PubMed1997

Laser-tissue interaction during transmyocardial laser revascularization.

BACKGROUND: The clinical procedure known as transmyocardial revascularization has recently seen its renaissance. Despite the promising preliminary clinical results, the associated mechanisms are subject to much discussion. This study is an attempt to unravel the basics of the interaction between 800-W CO2 laser radiation and biological tissue. METHODS: Time-resolved flash photography was used to visualize the laser-induced channel formation in water and in vitro porcine myocardium. In addition, laser-induced pressures were measured. Light microscopy and birefringence microscopy were used to assess the histologic characteristics of laser-induced thermal damage. RESULTS: The channel depth increased logarithmically with time (ie, with pulse duration) in water and porcine myocardium. Pressure measurements showed the occurrence of numerous small transients during the laser pulse, which corresponded with channel formation, as well as local and partial channel collapse during the laser pulse. Twenty millimeters of myocardium was perforated in 25 ms. Increasing the pulse duration had a small effect on the maximum transversable thickness, but histologic analysis showed that thermal damage around the crater increased with increasing pulse duration. CONCLUSIONS: Several basic aspects of the interaction of high-power CO2 laser radiation with myocardial tissue and tissue phantoms were studied in vitro. Although the goal of this study was not to unravel the mechanisms responsible for the beneficial effects of transmyocardial revascularization, it provided important information on the process of channel formation and collapse and tissue damage.

Animals↗

PubMed1997

Photosensitization of experimental hepatocellular carcinoma with protoporphyrin synthesized from administered delta-aminolevulinic acid: studies with cultured cells and implanted tumors.

BACKGROUND/AIMS: Photodynamic therapy using porphyrins or related compounds and laser light is an investigational treatment for neoplasms. The aim of this study was to establish whether this might be applicable for hepatocellular carcinoma using protoporphyrin synthesized in the tissue from administered delta-aminolevulinic acid. METHODS: We measured porphyrin accumulation in normal rat hepatocytes and Morris hepatoma cells in culture, and in subcutaneously implanted hepatomas and other tissues of the rat after administration of delta-aminolevulinic acid, and assessed cell and tissue damage after application of laser light. RESULTS: Porphyrin accumulation after delta-aminolevulinic acid was added to the medium was greater and continued to increase for a longer period of time in hepatoma cells than in hepatocytes (1337+/-42 vs 513+/-31 fluorescence units/cell at 8 h, means+/-SE, p<0.001). After intraperitoneal injection of delta-aminolevulinic acid to rats with subcutaneously growing hepatomas, porphyrin content in tumor and liver was similar at 4 h but was higher in tumor at 6 h. Laser light caused necrosis of normal and malignant liver cells in culture and subcutaneous hepatomas in vivo. CONCLUSIONS: We conclude from these in vitro and in vivo studies that porphyrin accumulation after administration of delta-aminolevulinic acid in this hepatoma is substantial and time dependent, and delivery of laser light locally can cause tumor photosensitization and necrosis.

Aminolevulinic Acid↗

PubMed1996

Effect of pulse duration on bubble formation and laser-induced pressure waves during holmium laser ablation.

BACKGROUND AND OBJECTIVE: One concern during laser ablation of tissue is the mechanical injury that may be induced in tissue in the vicinity of the ablation site. This injury is primarily due to rapid bubble expansion and collapse or due to laser-induced pressure waves. In this study, the effect of laser pulse duration on the thermodynamics of bubble formation and accompanying acoustic pressure wave generation has been investigated. STUDY DESIGN/MATERIALS AND METHODS: Q-switched holmium:YAG laser pulses (pulse duration 500 ns, pulse energy 14 mJ) and free-running holmium:YAG laser pulses (pulse duration 100-1,100 microseconds, pulse energy 200 mJ) were delivered in water and tissue phantoms via a 200- and 400-microns fiber, respectively. The tissue phantoms consisted of polyacrylamide gels with varying mechanical strengths. Bubble formation was recorded with a fast flash photography setup, while acoustic transients were measured with a needle hydrophone. RESULTS: It was observed that, as the pulse length was increased the bubble shape changed from almost spherical for Q-switched pulses to a more elongated cylinder shape for longer pulse durations. The bubble expansion velocity was larger for shorter pulse durations. Only the Q-switched pulse induced a measurable thermo-elastic expansion wave. All pulses that induced bubble formation generated pressure waves upon collapse of the bubble in gels as well as in water. However, the magnitude of the pressure wave depended strongly on the size and geometry of the induced bubble. CONCLUSION: The magnitude of the collapse pressure wave decreased as laser pulse duration increased. Hence it may be possible to reduce collateral mechanical tissue damage by stretching the holmium laser pulse.

Acoustics↗

PubMed1996

Healing response of the canine prostate to Nd:YAG laser radiation.

The objective of the study was to characterize the healing response of the canine prostate to laser thermal injury. The study included 20 canine prostates that underwent transurethral laser radiation. The prostates were retrieved 1 hr after laser radiation in 7 dogs (acute group), and from 3 days to 9 weeks in 13 dogs (chronic group). Two distinct features were observed. First, reepithelialization of the prostate urethra resulted from mobilization of proliferating epithelial cells from acinar and ductal prostatic epithelium into the cavity surface, and not from the edges of the wound at the bladder neck. Squamous cell metaplasia was a prominent feature of reepithelialization. Second, the healing process in the canine prostate was relatively unimpeded. The large glandular component provided abundant germinal epithelial growth, and the absence of stromal elements allowed for complete sloughing of necrotic tissue without residual eschars. Further, the lesions in the chronic group had a tendency to be larger than those in the acute group, suggesting that extended delayed necrosis may occur at deep prostatic tissue layers.

Animals↗

PubMed1996

Optical characterization and coagulation performance of side-emitting fiber delivery systems for laser therapy of benign prostatic hyperplasia: a comparative study.

OBJECTIVES: Currently, various side-emitting optical fibers with different tip geometry are used transurethrally to deliver laser radiation for treatment of benign prostatic hyperplasia (BPH). Since fiber tip design could profoundly affect the size and profile of the emitted laser beam, and consequently the tissue response and the extent of tissue coagulation, we evaluted commercially available fibers in regard to their optical characteristics and their ability to coagulate tissue in a controlled experimental setting. METHODS: Thirteen fibers manufactured by different companies and clinically used at the present time were tested using a surgical neodymium: yttrium-aluminum-garnet laser. The profile of the laser beam delivered via each fiber was imaged on a CCD camera at various distances and evaluated by means of a laser beam analyzer. Beam divergence angle was then calculated for each tip. Tissue coagulation effects were assessed by irradiating samples of beef muscle immersed in water at 37 degrees C. The fiber tip was kept 2.5 mm away from the tissue and irrigation was maintained at flow rate of 350 to 400 cc/min during irradation. Laser powers of 20, 40, and 60 W were used for 180, 90, and 60 seconds, respectively, delivering a total energy of 3600 J. RESULTS: The results of the optical evaluation divided the fibers into two major groups: broad beam with large divergence angle and narrow beam with small divergence angle. Statistical analysis of the data (using analysis of variance) showed that volumes of coagulated tissue were significantly larger for broad beam fibers than for narrow beam fibers (1.15 +/- 0.32 versus 0.89 +/- 0.34 cm 3; P < 0.05). Also, significantly larger volumes were obtained for 20 W when compared with 60 W (1.08 +/- 0.43 versus 0.88 +/- 0.27 cm 3; P < 0.05). CONCLUSIONS: The laser power density delivered by individual fibers to the prostate tissue may vary significantly, thus greatly affecting the extent of tissue coagulation. Therefore, irradiation parameters must be optimized for each fiber type.

Animals↗

PubMed1996

Mechanism of healing of the human prostatic urethra following thermal injury.

OBJECTIVES: To characterize histopathologically the healing response of the prostatic urethra after laser thermal coagulation and standard transurethral resection of the prostate (TURP). METHODS: The study included 31 patients who underwent radical prostatectomy because of malignancy. Twenty-two (first group) had laser radiation either at the time of surgery (18 patients) or from 1 to 12 weeks prior to prostatectomy (4 patients). Nine patients (second group) had TURP from 6 to 96 weeks prior to prostatectomy. RESULTS: Coagulation necrosis followed by sloughing was observed during the first 10 weeks after laser radiation. After the first 10 weeks, the healing response was otherwise stereotypical and comparable for both groups of patients. Re-epithelialization was prominent and resulted from migration of proliferating epithelial cells from the remaining acinar and ductal epithelium. Squamous metaplasia was conspicuous and present indefinitely. Development of inflammatory reaction followed by granulation tissue and well-organized fibroblastic stroma were sequentially recognized, but less prominent. Complete re-epithelialization and wound sealing was not observed before the first 12 weeks of healing. CONCLUSIONS: Our study suggests that laser thermal coagulation and TURP are partial-thickness injuries. Because of the abundant germinal epithelium in the remaining prostatic glands and ducts, the healing response of the prostatic urethra is relatively unimpeded and free of contractures, analogous to second-degree skin burns.

Aged↗

PubMed1996

Dye-enhanced diode laser photothermal ablation of skin.

BACKGROUND: Near-infrared diode lasers are promising new light sources. However, their applications for rapid and precise removal of tissue is limited because their radiation is poorly absorbed by most tissue. OBJECTIVE: Our purpose was to determine the interaction of diode laser radiation with tissue by topically applying absorbing dye to enhance laser-tissue interaction and to examine the ability of this approach to create superficial and localized thermal effects in skin. METHODS: Immediate and long-term responses of guinea pig skin to low-power (3 to 5 W X 1 sec) diode laser (805 nm) irradiation in conjunction with indocyanine green as a dye were studied. Tissue response was characterized on the basis of gross and histopathologic analysis of biopsy specimens taken at different times. RESULTS: The observed depths of thermal damage with dye were greater than those produced by diode laser used alone at higher power settings (10 W X 1 sec). CONCLUSION: Interaction of diode laser radiation enhanced by topical application of dye causes localized superficial thermal effects in skin. This may offer a new modality in the treatment of superficial lesions.

Absorption↗

PubMed1996

Evaluation of spectral correction techniques for fluorescence measurements on pigmented lesions in vivo.

Recently, the use of optical spectroscopy for non-invasive diagnosis of malignant melanoma has been suggested. The reliability of such optical measurements can be seriously compromised by spatial variations in the optical properties of the tissue that are not related to malignancy. In the present paper we report a novel approach to fluorescence spectroscopy which allows for elimination of spatial variations in the optical properties of the tissue investigated. To test this concept we performed fluorescence and color measurements on moles and unpigmented control skin in human volunteers before and after topical application of delta-aminolevulinic acid (ALA). Two types of fluorescence data analysis were investigated; a single ratio technique based on the ratio of the red to the yellow fluorescence (660-750 nm to 550-600 nm) at 405 nm excitation and a double-ratio technique, the red-to-yellow ratio at 405 nm excitation divided by the red-to-yellow ratio at 435 nm excitation. The two excitation wavelengths were selected to be located close to the maximum and at some distance from the Soret excitation band of the porphyrins. The single ratio showed a significant correlation between fluorescence and color. The double ratio was independent of the color of the lesion. These findings indicate that the double-ratio technique is suitable for in-vivo detection of local differences in concentration of fluorescent tumor-localizing drugs in pigmented lesions. This enables in-vivo studies of the pharmacokinetics of tumor-localizing agents in pigmented lesions and may significantly contribute to the development of a non-invasive diagnostic tool for malignant melanoma.

Adult↗

PubMed1996

Dynamics of temperature dependent optical properties of tissue: dependence on thermally induced alteration.

Thermal damage in heated bovine myocardial tissue is assessed from measured changes in total reflection and transmission of light. Mathematical expressions, based on random walk analysis of light propagation within tissue slabs, are used to relate the diffuse reflection and transmittance to the absorption coefficient, mu a, and effective scattering coefficient, mu's, for samples of myocardial tissue which were subjected to rapid step changes in temperature. Time-dependent changes in mu's, indicate two processes, one with a fast and temperature-dependent rate the other with a slow and apparently temperature-independent rate. For final temperatures above 56.8 degrees C and for the first 500 s after the temperature change, the optical parameters are well fit by exponential forms that exhibit temperature-dependent time constants as predicted by Arrhenius reaction rate theory of thermal damage. The scattering changes are associated with an apparent activation energy, delta E, of 162 kJ/mole and a frequency constant, A, of 3 x 10(23) s-1. This method provides a means for estimating optical coefficients which are needed to assess laser tissue dosimetry.

Absorption↗

PubMed1996

Accumulation of porphyrins in plasma and tissues of dogs after delta-aminolevulinic acid administration: implications for photodynamic therapy.

Protoporphyrin accumulates in tissues after administration of delta-aminolevulinic acid, and can be used as a photosensitizer for photodynamic therapy. To determine the distribution of porphyrins in a large animal model after administration of this porphyrin precursor, delta-aminolevulinic acid was administered to anesthetized dogs (100 mg/kg body weight intravenously) and porphyrin concentrations were measured in tissues (liver, pancreas, prostate, bladder, muscle and skin), plasma and urine for 6-10 h. Porphyrins increased markedly (up to 50-fold) in plasma within 1 h, were still markedly increased at 8 h, and consisted mostly of coproporphyrin III and protoporphyrin. Tissue porphyrin concentrations increased more slowly, were highest in liver, pancreas and prostate 7-10 h after delta-aminolevulinic acid administration, and were predominantly protoporphyrin. Maximum porphyrin concentrations in liver were 3- and 4-fold higher than in pancreas and prostate, respectively. Urinary delta-aminolevulinic acid excretion increased and was greatest 2-4 h after dosing; urinary porphobilinogen and porphyrins increased more gradually and remained increased up to at least 8 h. Coproporphyrin III was the predominant porphyrin in urine at all times, but hepta-, hexa- and pentacarboxyl porphyrins increased proportionally after administration of delta-aminolevulinic acid. These results indicate that porphyrins accumulate in plasma as well as tissues and urine after administration of delta-aminolevulinic acid, and may contribute to tumor necrosis during photodynamic therapy.

Aminolevulinic Acid↗

PubMed1996

Laser irradiation for the treatment of benign prostatic hyperplasia.

Benign prostatic hyperplasia (BPH) is one of the most common medical problems encountered in the United States. For many years, transurethral resection of the prostate (TURP) has been the mainstay of treatment for symptomatic BPH. In recent times, newer modalities of treatment in the form of drugs (a- blockers, LHRH-agonist, anti-androgens, 5 a-reductase inhibitors), microwave hyperthermia, prostatic stents, balloon urethroplasty, laser prostatectomy, and most recently High Intensity Focal Ultrasound (HIFU) and Trans Urethral Needle Ablation (TUNA) are challenging TURP as the gold standard therapy for BPH. Today, laser prostatectomy holds a special place in therapy of BPH, as it is easy to perform, safe to apply with a vastly improved patient compliance, and is the first choice in certain special circumstances, e.g., patients on anticoagulants. In this chapter we discuss the present status of laser prostatectomy for BPH.

Journal Article↗