Ablation Cycles Research Articles

Prostate cancer cells generated during intermittent androgen ablation acquire a growth advantage and exhibit changes in epidermal growth factor receptor expression.

Intermittent androgen ablation is a palliative treatment option for advanced prostate cancer which is associated with less side effects, improved quality of life of patients, and reduced costs. Regulation of growth and survival of prostate cancer cells during intermittent androgen withdrawal has not been studied in appropriate models yet. Two cycles of androgen withdrawal and supplementation were performed in human prostate cancer cells LNCaP in vitro. Proliferation of prostate cancer cell sublines established after intermittent androgen withdrawal was assessed in the absence or presence of epidermal growth factor (EGF) by protein determination. Cell cycle was analyzed with a flow cytometer. EGF was measured in the supernatants of LNCaP sublines with a commercial ELISA. EGF receptor mRNA and protein were determined by real-time PCR and Western blot, respectively. Basal proliferation rate of all newly generated LNCaP sublines increased over that of the parental LNCaP cell line. The highest stimulation of proliferation by exogenous EGF was observed in parental LNCaP cells. In each LNCaP derivative established during intermittent androgen withdrawal, the percentage of cells in the S phase of cell cycle was higher than that in parental LNCaP cells. EGF levels did not increase during intermittent androgen ablation. The expression of EGF receptor protein decreased following each cycle of androgen ablation and increased subsequently after androgen supplementation. EGF receptor (EGFR) mRNA was regulated in a similar manner in LNCaP derivatives established during the second cycle of intermittent withdrawal. Changes in the expression of the EGF receptor occur during intermittent androgen ablation but they cannot be solely responsible for increased basal proliferation. Alternatively, other ligands and receptors of the EGF system may become overexpressed during prolonged withdrawal and supplementation of androgenic hormones in prostate cancer therapy.

Group A streptococcus septicaemia after thermal ablation of the endometrium for menorrhagia

A 38 year old woman had a three-year history of menorrhagia. Her periods were regular. A copper intrauterine contraceptive device had been removed in the past because of menorrhagia and she had subsequently been sterilised. Previously, she had had a Bartholin’s abscess and had been treated for cervicitis with laser vaporisation on three occasions, the last time being in 1998. She had four uncomplicated full term normal deliveries. As a child, she had meningitis and her only medication was beta mimetics to treat asthma. For several years, she had been anaemic and had been treated with iron tablets and tranexamic acid. This treatment did not reduce the menorrhagia and her general practitioner referred her to the hospital. Gynaecological examination was normal. Vaginal ultrasound revealed a uterus of normal size without fibroids and normal ovaries. Endometrial aspiration was performed and histological examinations showed secretory endometrium. Treatment was discussed and the options considered were the levonorgestrel intrauterine system and thermal ablation of the endometrium. She elected thermal ablation. The procedure was carried out five months after her first out patient appointment. Before the endometrial ablation, the vagina was cleaned with 0.1% chlorhexidine solution and 20 ml of 0.25% bupivacaine was given as a paracervical block. The cervix was dilated to 5 mm with Hegar dilators and the uterine cavity was noted to be 8 cm long. The ablation system (Thermachoice, Fa. Gynecare, Menlo Park, California, USA) was prepared and inserted into the uterine cavity in the standard manner. The ablation cycle was carried out without any problems and the woman was discharged 20 hours after the procedure. Thirty hours after the endometrial ablation, she experienced lower abdominal pain and fever. Six hours later, she was readmitted to hospital. The concentration of C reactive protein in her blood was 84 mg/ml (normal range <5 mg/ml), her platelet count was 87 10/L (normal range 150–450 10/L) and her white cell count was 3.4 10/L (normal range 3.5–10 10/L). A clinical diagnosis of pelvic infection was made and intravenous cefuroxime and metronidazole was started. During the following hours, she deteriorated with intense abdominal pain and circulatory collapse, suggesting severe septicaemia. A laparotomy was carried out five hours after her re-admission. Inspection of the abdominal cavity revealed bilaterally necrotic tubes and ovaries and a discolouration of the fundus of the uterus. A total hysterectomy and bilateral salphingo-oophorectomy was performed and all necrotic tissue was removed. A cystoscopy was carried out and ureteric stents were inserted bilaterally. The bladder mucosa was found to be haemorrhagic and discoloured in places. The abdomen was closed. Material from the left fallopian tube and the serosa of the uterus grew group A streptococcus, sensitive to the antibiotics being prescribed. Histopathological examination showed necrosis of the endometrium and the submucosal myometrium due to the thermal ablation. Abscesses were found in the myometrium and the left ovary containing Gram-positive coccus. Both adnexae and uterus showed areas of infarction. The woman then developed disseminated intravascular coagulation and renal failure. Vaginal examination 20 hours after the laparotomy showed necrosis of the vaginal stump and cystoscopy revealed haemorrhagic discolouration of most of the bladder mucosa. Since she had need of both continuous dialysis and major pelvic surgery, she was transferred to the regional hospital. Immediately after arrival, a cystectomy, vaginectomy, vulvectomy and a transverse colostomy were carried out. These entire organs were necrotic, as were the distal parts of the ureters. Urine was drained by bilateral ureterocutaneostomies. Due to septicaemia and disseminated intravascular coagulation, severe compartment syndromes developed in both legs and arms. Although fasciotomies were performed in all extremities, bilateral below knee amputations had to be performed in addition to a major resection of muscles of the right arm and a smaller resection of muscles in the left arm. BJOG: an International Journal of Obstetrics and Gynaecology April 2003, Vol. 110, pp. 439–440

PERCUTANEOUS RADIO FREQUENCY ABLATION OF SMALL RENAL TUMORS: INITIAL RESULTS

Thermal tissue ablation with radio frequency energy is an experimental treatment of renal tumor. We report early results of an ongoing trial of percutaneous radio frequency ablation for small renal tumors. Patients with percutaneously accessible renal tumors were evaluated for radio frequency ablation. Tumors were solid on computerized tomography (CT), 3 cm. or less in diameter and enlarging during at least 1 year. Ablation was performed at the Interventional Radiology suite under ultrasound and/or CT guidance. A 50 W., 460 kHz. electrosurgical generator delivered radio frequency energy via a percutaneously placed 15 gauge coaxial probe. At least 2, 10 to 12-minute ablation cycles were applied to each lesion. Patients were observed overnight before discharge from hospital and reevaluated 2 months later. A total of 24 ablations were performed in 21 patients with renal tumor, including solid von Hippel-Lindau clear cell tumor in 19 and hereditary papillary renal cancer 2. Most (22 of 24) procedures were performed with patients under conscious sedation. At 2 months postoperatively mean tumor diameter plus or minus standard deviation decreased from 2.4 +/- 0.4 to 2.0 +/- 0.5 cm. (p = 0.001), and a majority of tumors (19 of 24, 79%) ceased to be enhanced on contrast CT. Mean serum creatinine plus or minus standard deviation was unchanged during this interval (1.0 +/- 0.2 mg./dl.). No major and 4 minor complications were encountered, including 2 episodes each of transient psoas pain and flank skin numbness. Percutaneous radio frequency ablation of small renal tumor is well tolerated and minimally invasive. It will remain experimental until procedural and imaging parameters that correlate with tumor destruction are validated.

Depth profiling of tin-coated glass by laser ablation inductively coupled plasma emission spectrometry with acoustic signal measurement.

A pulsed, frequency-quadrupled Nd:YAG laser (266 nm, 10 Hz) coupled to an inductively coupled plasma atomic emission spectrometer (ICP-AES) was employed for depth profiling by ablation of a pyrolytically deposited Sn layer (300 nm) on float glass. The procedure consisted of performing individual ablation cycles (layer-by-layer). A raster with stroke distance of either 50 microm or 200 microm (the raster density) was used as an ablation pattern. The ablation was stopped after each cycle and the peak area of the resulting transient optical signal of the ICP discharge was plotted against the cycle number. The ablation rate of 90 to 20 nm per cycle at a low-energy pulse (6 mJ to 1 mJ) was determined by profilometry. A beam masking was employed to attenuate the laser shot energy and to eliminate the peripheral irregularity of the beam profile. Almost uniform removal of the square area (1 mm x 1 mm) of the coating by ablation was achieved by combining the fitted raster density, beam masking, focusing and beam energy. Different ablation processes were distinguished in cases of the tin coating and the uncoated glass surface. While the coating was mainly evaporated, the uncoated glass surface exhibited a crumbling associated with production of glass powder. This was confirmed by electron microscopy observations. The measured acoustic signal followed the behavior of the emission intensity of the Sn line and was supposed to be proportional to the amount of Sn vapors. The emission intensity depth profile of the Sn coating with graded structure was obtained, which qualitatively corresponded with the depth profile measured by secondary ion mass spectrometry.

The effect of ablation sequence and duration on lesion shape using rapidly pulsed radiofrequency energy through multiple electrodes.

Sequences of energy application to multiple electrodes and a study of ablation duration with distal tip and multi-electrode ablations were explored with a radiofrequency controller that distributes energy from a generator to up to 4 electrodes with various duty cycles. In vitro ablations were performed on bovine left ventricle in circulating blood and lesions in goats were performed to verify the in vitro results. All of the ablation sequences with simultaneous electrode activation of contiguous electrodes resulted in deeper lesions than those created in sequence. There was also no scalloping of the lesion if contiguous electrodes were activated simultaneously. During all distal tip ablations, lesion volume and depth was greater after 3 minutes of energy delivery than after 1 minute, but did not increase from 3 minutes to 5 minutes. There was a significant increase in multi-electrode ablation lesion depth with each additional minute in the ablation cycle. The in vivo ablations verified these results at 120 and 300 second ablations. Pulsed energy distal tip ablations resulted in deeper lesions than continuous only if power amplitudes over 50 W were employed. In conclusion, contiguous electrodes in simultaneous use create lesions that resemble one large lesion rather than two lesions positioned next to each other. Multi-electrode ablation lesions continue to grow at ablation durations of up to 5 minutes compared to distal tip lesions which reach steady-state between 1 and 3 minutes. Pulsed energy delivery to distal tips may result in deeper lesions than conventional if high powers are employed.

Study of UV Laser Ablation of Nitrided Steels Using Inductively Coupled Plasma Atomic Emission Spectrometry

A depth profile study of nitrided steels containing Ti or V sputtered in the surface layer was performed by means of laser ablation inductively coupled plasma atomic emission spectrometry. An Nd:YAG laser was used in the Q-switched mode and operated at 355 and 266 nm. The laser ablation patterns were obtained on the material surface by moving the ablation cell relative to the laser beam by means of an XY-translator. Depth resolution was obtained by using successive limited numbers of ablation cycles. The corresponding transient signals of Ti or V and Fe were measured simultaneously with a dual monochromator. The effect of the number of cycles, the laser power and laser wavelength on the time-dependent behaviour of the Ti or V and Fe line intensities was studied along with the erosion rate. It was found that the erosion rate was lower than 0.6 μm per cycle and depended on the depth of penetration. Emission of sputtered Ti and V was mainly observed in an external layer of less than 2 μm. The laser wavelength did not modify the shape of the crater but significantly changed the line intensity of Fe. The Fe line intensity was also enhanced during the ablation of the nitrided steel compared with the ablation of untreated steel. This study contributes to the knowledge of behaviour of the modified metal surface during interaction with the laser radiation, which is important for development of the method for determination of composition of nitrided surface layers.

Glacier Fluctuations in the Antarctic Peninsula: The Last Decade (Abstract)

Following international recommendations (UNESCO / IASH 1969), the decision was made to determine the surface profile of a number of glaciers in Palmer Land and Alexander Island. By comparison with the ice sheet elsewhere on the continent, the chosen glaciers were small and hence more sensitive to the effect of climate over the last few decades. Six profiles were established between 1972 and 1976 and they were re-levelled in the 1985-86 summer. The profiles are between 0.5 and 4.5 km long and are terminated, at one end at least, by a bench mark established on rock. The profiles were re-measured close to the calendar date of the original survey so that recent trends would not be masked by the annual cycle of accumulation, densification and ablation. Five of the six profiles show that the ice sheet has thickened in the last 10-15 years, albeit at a slow rate. Changes in four profiles on Alexander Island within 300 m of sea-level range from a thickening of 66 mm a−1 to a thinning of 83 mm a−1; on average the sites show a thickening of just 6 mm a year. This is similar to the thickening rate of 5 mm a−1 which was found for a cold site on the spine of the Antarctic Peninsula at 1600 m above sea-level. The greatest change was found at an intermediate elevation (500 m). In a snow-field between two parallel mountain groups in the Batterbee Mountains of Palmer Land, thickening averaged 165 mm a−1. To put these values into perspective, in the absence of glacier flow and summer melting, the glaciers would thicken by up to about 500 mm each year as a result of the accumulation of snow.Except in the Batterbee Mountains, we find that glacier flow is in close balance with present climate, despite the general warming trend that has occurred in the Antarctic Peninsula region over the past 30 years.

Glacier Fluctuations in the Antarctic Peninsula: The Last Decade (Abstract)

Following international recommendations (UNESCO / IASH 1969), the decision was made to determine the surface profile of a number of glaciers in Palmer Land and Alexander Island. By comparison with the ice sheet elsewhere on the continent, the chosen glaciers were small and hence more sensitive to the effect of climate over the last few decades. Six profiles were established between 1972 and 1976 and they were re-levelled in the 1985-86 summer. The profiles are between 0.5 and 4.5 km long and are terminated, at one end at least, by a bench mark established on rock. The profiles were re-measured close to the calendar date of the original survey so that recent trends would not be masked by the annual cycle of accumulation, densification and ablation. Five of the six profiles show that the ice sheet has thickened in the last 10-15 years, albeit at a slow rate. Changes in four profiles on Alexander Island within 300 m of sea-level range from a thickening of 66 mm a−1 to a thinning of 83 mm a−1; on average the sites show a thickening of just 6 mm a year. This is similar to the thickening rate of 5 mm a−1 which was found for a cold site on the spine of the Antarctic Peninsula at 1600 m above sea-level. The greatest change was found at an intermediate elevation (500 m). In a snow-field between two parallel mountain groups in the Batterbee Mountains of Palmer Land, thickening averaged 165 mm a−1. To put these values into perspective, in the absence of glacier flow and summer melting, the glaciers would thicken by up to about 500 mm each year as a result of the accumulation of snow. Except in the Batterbee Mountains, we find that glacier flow is in close balance with present climate, despite the general warming trend that has occurred in the Antarctic Peninsula region over the past 30 years.

A simple parameterization for ice sheet ablation rate

A parameterization of monthly mean ice sheet ablation as a function only of surface air temperature and insolation is examined. By considering differences in summer climate between the present and the last ice age, it is suggested that the parameterization adequately describes long-term changes in ablation. Although significant discrepancies are found between the parameterization and the seasonal variation of ablation observed on present-day glaciers, the seasonal ablation cycle is still predicted accurately enough to maintain the validity of the parameterization for long-term net annual variations.

A simple parameterization for ice sheet ablation rate

A parameterization of monthly mean ice sheet ablation as a function only of surface air temperature and insolation is examined. By considering differences in summer climate between the present and the last ice age, it is suggested that the parameterization adequately describes long-term changes in ablation. Although significant discrepancies are found between the parameterization and the seasonal variation of ablation observed on present-day glaciers, the seasonal ablation cycle is still predicted accurately enough to maintain the validity of the parameterization for long-term net annual variations.

Problèmes hydrologiques et hydrochimiques du karst du Liban central

SUMMARY The wealth of karst in central Lebanon has permitted the study of the perched aquifer (of the high cenomanien plateau of Kesrouane) in comparison to the Barred limestone aquifer (of the low and middle mountains) and the cretaceous aquifer of the littoral area that contributes of the alimentation of powerful submarine springs. The study of the « ablation cycle » leads to the valuation of the dissolved contents of the meteoric waters, the streaming, percolated, infiltred waters, as well as of the subterranean rivers and the karstic springs. The chimical analyse of rain waters, as soon as they arrive on a karstic reception basin and stream on a distance of 100 meters, gives important results.