Cryosurgery of the prostate: techniques and indications

Cryosurgical ablation of the prostate (CSAP) is indicated for patients with high-stage and high-grade tumors, patients with recurrent/persistent carcinoma of the prostate after external radiation therapy or brachytherapy, and others. At Allegheny General Hospital, CSAP is performed as follows: the patient is prepped in an exaggerated lithotomy position; a volumetric study of the gland is obtained with transrectal ultrasound; 5 to 15 cryoneedles are placed (in three to five horizontal rows) through a 17-gauge, stepper-mounted template; a cystoscopy is performed; and a urethral warming catheter is introduced. The rows of cryoneedles are then activated from anterior to posterior, and generally two freeze-thaw cycles are used. In longer glands, a pullback of the cryoneedles might be needed to completely cover the apical portion of the gland. The skills required for CSAP are identical to those required for brachytherapy needle placement, thus the training required for physicians already proficient in brachytherapy is minimized.     

The renin–angiotensin system plays a major role in voiding dysfunction of ovariectomized rats

Aims

The renin–angiotensin system (RAS) plays a major role in cardiovascular diseases in postmenopausal women, but little is known about its importance to lower urinary tract symptoms. In this study we have used the model of ovariectomized (OVX) estrogen-deficient rats to investigate the role of RAS in functional and molecular alterations in the urethra and bladder.

Main methods

Responses to contractile and relaxant agents in isolated urethra and bladder, as well as cystometry were evaluated in 4-month OVX Sprague–Dawley rats. Angiotensin-converting enzyme activity and Western blotting for AT1/AT2 receptors were examined.

Key findings

Cystometric evaluations in OVX rats showed increases in basal pressure, capacity and micturition frequency, as well as decreased voiding pressure. Angiotensin II and phenylephrine produced greater urethral contractions in OVX compared with Sham group. Carbachol-induced bladder contractions were significantly reduced in OVX group. Relaxations of urethra and bladder to sodium nitroprusside and BAY 41-2272 were unaffected by OVX. Angiotensin-converting enzyme activity was 2.6-fold greater (p < 0.05) in urethral tissue of OVX group, whereas enzyme activity in plasma and bladder remained unchanged. Expressions of AT1 and AT2 receptors in the urethra were markedly higher in OVX group. In bladder, AT1 receptors were not detected, whereas AT2 receptor expression was unchanged between groups. 17β-Estradiol replacement (0.1 mg/kg, weekly) or losartan (30 mg/kg/day) largely attenuated most of the alterations seen in OVX group.

Significance

Prolonged estrogen deprivation leads to voiding dysfunction and urethral hypercontractility that are associated with increased ACE activity and up-regulation of angiotensin AT1/AT2 receptor in the urethral tissue.     

Cryoprotective therapy for hepatocellular carcinoma: Study of 51 patients with a single lesion

Percutaneous cryoablation is a potentially curative treatment for hepatocellular carcinoma (HCC). After liver cryosurgery, rapid elevations of transaminases and bilirubin are common, but are usually transient and normalize within a few days. This study retrospectively reviewed clinical data from 51 patients who underwent liver cryoablation in our hospital during the past 4.5 years. Sixty-six percutaneous cryoablations were performed in these patients and transaminase and bilirubin levels before and after the procedure were observed. Although most patients received liver-protective treatment before cryosurgery, transaminase levels were double (mean alanine transaminase (ALT) and aspartate transaminase (AST) were 71 U/L and 85 U/L, respectively) the normal ranges in our hospital. One day after cryosurgery, ALT and AST had increased 3.3-fold (peak mean was 241 U/L) and 5-fold (peak mean was 427 U/L), respectively, but were close to the preoperative level 5 days post-cryosurgery. No significant increase of serum bilirubin was observed. Serum transaminase and bilirubin levels were compared between hepatitis B positive and hepatitis B negative patients. Only in the hepatitis B positive group were total bilirubin (74 μmol/L/23 μmol/L = 3.2) and direct bilirubin (45 μmol/L/12 μmol/L = 3.8) more than 3 times the preoperative level 7–9 days after treatment. Overall, ALT and AST are valuable as indicators of liver function impairment following cryosurgery. In patients with hepatitis B virus, serum bilirubin was 3 times the preoperative level 7–9 days after cryosurgery. Liver-protective treatment may alleviate liver function impairment due to cryosurgery.     

Liquid nitrogen for the treatment of actinic keratosis: A longitudinal assessment

Cryosurgery with liquid nitrogen is one of the most used treatments for actinic keratosis. We aimed to study the effectiveness of two consecutive sessions of cryosurgery for actinic keratosis and investigate factors associated with its therapeutic success. Hence, we conducted a longitudinal study including 92 patients of both sexes, aged 50–75 years with 5–50 actinic keratosis on the face and forearms, who underwent cryosurgery and treatment with sunscreen SPF 30, at baseline and after 120 days. The lesions were counted in duplicate by the same examiner before the start of treatment and after 120 (N = 92) and 300 days (N = 33), represented by their medians and quartiles and compared using the generalized linear mixed effects model (negative binomial). Treatment behavior was investigated in relation to sex, age, education, skin type, smoking, sun exposure at work and the use of aspirin, anti-inflammatory and angiotensin-converting enzyme inhibitors. There was a significant reduction in the actinic keratosis count on the face and forearms (p < 0.05). Our results confirmed the effectiveness of cryosurgery for actinic keratosis, with a 57% reduction in the number, and size of the lesions. Higher education levels (p = 0.02) and less sun exposure at work (p = 0.02) independently promoted a significant reduction in the actinic keratosis count. Different population groups showed characteristic responses to the treatment, which may be explained by the degree of adherence to the use of photoprotection. In two sessions, cryosurgery with liquid nitrogen reduced the actinic keratosis count.     

Devitrification and recrystallization of nanoparticle-containing glycerol and PEG-600 solutions

Nanoparticles in solution offer unique electrical, mechanical and thermal properties due to their physical presence and interaction with the state of dispersion. This work is aimed to study the effects of hydroxyapatite (HA) nanoparticles on the devitrification and recrystallization events of two important cryoprotective solutions used in cell and tissue preservation namely glycerol (60% w/w) and PEG-600 (50% w/w). HA nanoparticles (20, 40 or 60 nm) were incorporated into solutions at the content of 0.1% or 0.5% (w/w), and were studied by differential scanning calorimeter (DSC) and cryomicroscopy. The presence of nanoparticles does not change the glass transition temperatures and melting temperatures of quenched solutions, but significantly affects the behavior of devitrification and recrystallization upon warming. Cryomicroscopic investigation showed the complex interactions among solution type, nanoparticle size and nanoparticle content, which apparently influence ice crystal growth or recrystallization in the quenched dispersions. These findings have significant implications for biomaterial cryopreservation, cryosurgery, and food manufacturing. The complexity of ice crystal growth kinetics in nanoparticle-containing dispersions remains to be poorly understood at the moment.     

A new urethral catheter

A new balloon catheter for women with a flexible urethral portion that conforms to the shape of the closed urethra was tested. In sheep control catheters caused epithelial destruction, which was absent with the conformable catheter. A 12 week crossover trial compared control catheters in 52 long stay geriatric patients. Eighty two out of 91 conformable catheters were rated as comfortable compared with 68 of 87 control (p=0·006). The average length of time in situ was 15·9 days for the conformable catheter compared with 12·9 days for the control (p=0·001). The average number of bypasses a week with the conformable catheter was 1·1 compared with 1·3 for the control; this difference was not significant. Examination of 249 used catheters showed significantly fewer with intraluminal obstruction with struvite among the conformable than control catheters (1 (0·8%) versus 15 (11·5%); p<0·001).This new catheter for women is a substantial improvement over the Foley catheter and (except in urethral stricture) is suitable for all forms of drainage.     

Can the Day 0 CT-scan predict the post-implant scanning? Results from 136 prostate cancer patients

PurposePost-implant CT-scanning is an essential part of permanent prostate brachytherapy. However, the evaluation of post-implant CT dosimetry is not straightforward due to the edema that can modify the dose to the prostate and to the organs at risk. The aim of this study is to evaluate the impact of the timing of the post-implant CT-scan on the dosimetric results and to verify if the Day 0 scan findings can predict Day 50 scanning.Methods136 consecutive patients who received monotherapy with I-125 implants were selected for this study. Two sets of 8 dosimetric quality parameters corresponding to 2 different CT-scans (Day 0 and Day 50) were calculated and compared. The dosimetric parameters included are the percentage volume of the post-implant prostate receiving 80%, 100% and 150% of the prescribed dose, the doses covering 80% and 90% of the prostate volume and the Dose Homogeneity Index. The values of the dose covering 1 cm³ of the rectum and urethra were assessed.ResultsAll the dosimetric parameters of the Day 50 were higher than those of the Day 0 scan. Linear functions were obtained that calculate D₉₀ and V₁₀₀ values at Day 50 based on the Day 0 findings. Rectal and urethral parameters tended to be underestimated on Day 0 CT-scan relative to Day 50 based dosimetry.ConclusionsPredicting the Day 50 dosimetry from the Day 0 scan could be a possible alternative to a Day 50 scan only in specific situations, but with a degree of uncertainty in the predicted values.     

New device for the vitrification and in-straw warming of in vitro produced bovine embryos

Two experiments were designed to test the use of a new device designed to vitrify and in-straw warm in vitro produced (IVP) embryos, which can potentially be used for their direct transfer to recipient females in field conditions. In experiment 1, IVP embryos from both prepubertal and adult animals were vitrified on cryotops and warmed in steps (1, 0.5 and 0 M sucrose; protocol W3) or directly in 0.5 M (protocol W1/0.5) or 0 M sucrose (protocol W1/0). Similar survival rates were recorded 24 h after warming for calf embryos irrespective of the warming procedure (W3: 79.2%, W1/0.5: 62.5%, W1/0: 66.7%). For cow embryos, survival rates at 24 h post-warming were significantly higher when embryos were warmed using the W3 (85.7%) or W1/0.5 (89.1%) protocols compared to the W1/0 protocol (70.5%). In experiment 2, IVP embryos were vitrified on the new designed device followed by their in-straw cryoprotectant (0.5 M sucrose) dilution/warming and different warming temperatures (45, 50, 60 and 70 °C) were tested. When warming solution passed through the new vitrification/warming device at 45 °C, 61.5% of blastocysts were fully re-expanded or hatched at 24 h post-warming, being not significantly different to the control (65%). Other warming temperatures triggered significantly lower survival rates at 24 h post-warming. No significant differences were detected in total cell numbers and blastocyst apoptosis indices in response to vitrification followed by warming at 45 °C respect to the control. Our findings indicate that the new device allows vitrification and in-straw warming of IVP bovine embryos, being a useful option for their direct transfer in field conditions.     

Alleviating the pain of unresectable hepatic tumors by percutaneous cryoablation: Experience in 73 patients

Pain caused by liver tumors can be alleviated by cryoablation, but little is known about the analgesic effects and duration of pain alleviation. We retrospectively reviewed the changes in the severity of pain before and after percutaneous cryoablation of hepatic tumors. Each patient enrolled in this study had a single hepatic tumor; patients with large tumors (major diameter, ?5 cm) underwent transarterial chemoembolization (TACE) first and then cryoablation. Severe abdominal pain that was not controlled with long-lasting oral analgesics was treated with opioid injections. In all 73 study patients, severe abdominal pain was gradually eased 5 days after cryosurgery, completely disappeared after 15 days and did not recur for more than 8 weeks. There were no differences in analgesic effects between patients with hepatocellular carcinomas and those with liver metastasis (P > 0.05). The patients were divided into four groups depending on their pain outcomes: (i) immediate relief (n = 6), severe abdominalgia was no longer present after cryosurgery; (ii) delayed relief (n = 11), severe abdominalgia disappeared gradually within 15 days after the cryosurgery; (iii) always pain-free (n = 39), severe abdominalgia was not present before or after treatment; and (iv) new pain (n = 17), abdominalgia developed after treatment and disappeared within 15 days. In summary, percutaneous cryoablation of hepatic tumors caused short-term pain in some patients, but this pain disappeared within 15 days. Moreover, the pain-relieving effect of this treatment was sustained for at least 8 weeks, without severe side effects.     

Increased renal ENaC subunits and sodium retention in rats with chronic heart failure

The goal of this study was to examine acute morphological changes, edema, muscle damage, inflammation, and hypoxia in urethral and vaginal tissues with increasing duration of vaginal distension (VD) in a rat model. Twenty-nine virgin Sprague-Dawley rats underwent VD under anesthesia with the use of a modified Foley catheter inserted into the vagina and filled with saline for 0, 1, 4, or 6 h. Control animals were anesthetized for 4 h without catheter placement. Urogenital organs were harvested after intracardiac perfusion of fixative. Tissues were embedded, sectioned, and stained with Masson's trichrome or hematoxylin and eosin stains. Regions of hypoxia were measured by hypoxyprobe-1 immunohistochemistry. Within 1 h of VD, the urethra became vertically elongated and displaced anteriorly. Edema was most prominent in the external urethral sphincter (EUS) and urethral/vaginal septum within 4 h of VD, while muscle disruption and fragmentation of the EUS occurred after 6 h. Inflammatory damage was characterized by the presence of polymorphonuclear leukocytes in vessels and tissues after 4 h of VD, with the greatest degree of infiltration occurring in the EUS. Hypoxia localized mostly to the vaginal lamina propria, urethral smooth muscle, and EUS within 4 h of VD. Increasing duration of VD caused progressively greater tissue edema, muscle damage, and morphological changes in the urethra and vagina. The EUS underwent the greatest insult, demonstrating its vulnerability to childbirth injury.     

Thermal response and reversibility of prolonged larval diapause in the chestnut weevil, Curculio sikkimensis

Curculio sikkimensis undergoes prolonged larval diapause that is terminated by chilling and warming cycles. To examine the effects of warming temperatures and their duration on diapause termination, we exposed diapause larvae that had not been reactivated after chilling at 5 °C to 20 or 25 °C and chilled them again before incubation at 20 °C. With increasing warming duration at 20 °C, diapause termination after chilling increased and shorter chilling durations became effective. In contrast, few or no larvae warmed at 25 °C terminated diapause after chilling, irrespective of the warming duration. To investigate the effect of warming temperature on diapause intensity, larvae with diapause weakened by initial incubation at 20 °C after the first chilling were subsequently incubated at 15, 20, or 25 °C, then chilled at 5 °C before incubation at 20 °C. Diapause termination increased significantly after the larvae were treated at 15 or 20 °C but decreased significantly after they were treated at 25 °C. The intensification of prolonged diapause at 25 °C was reversed when the larvae were transferred to 20 °C. Diapause intensity in C. sikkimensis therefore decreases at 20 °C, increases at 25 °C, and can be reversed by alternately exposing diapause larvae to 20 and 25 °C. In C. sikkimensis, prolonged diapause does not always proceed in one direction, and its intensity fluctuates in response to ambient temperature conditions.     

Engineering of pre‐vascularized urethral patch with muscle flaps and hypoxia‐activated hUCMSCs improves its therapeutic outcome

Tissue engineering has brought new hopes for urethral reconstruction. However, the absence of pre‐vascularization and the subsequent degradation of materials often lead to the failure of in vivo application. In this study, with the assistance of hypoxia‐activated human umbilical cord mesenchymal stem cells (hUCMSCs), pedicled muscle flaps were used as materials and pre‐incubated in ventral penile subcutaneous cavity of rabbit for 3 weeks to prepare a pre‐vascularized urethral construct. We found that small vessels and muscle fibres were scattered in the construct after 3 weeks' pre‐incubation. The construct presented a fibrous reticular structure, which was similar to that of the corpus spongiosum under microscope examination. The produced constructs were then used as a patch graft for reconstruction of the defective rabbit urethra (experimental group), natural muscular patch was used as control (control group). Twelve weeks after the reconstructive surgery, urethrography and urethroscope inspections showed wide calibres of the reconstructed urethra in the experimental group. Histopathological studies revealed that fibrous connective tissues and abundant muscle fibres constituted the main body of the patch‐grafted urethra. In contrast, in the control group, only adipose tissue was found in the stenosis‐reconstructed urethra, replacing the originally grafted muscular tissue. To our knowledge, this is the first report that successfully constructed a pre‐vascularized urethral construct by using hypoxia‐activated hUCMSC and pedicled muscle flaps. More importantly, the pre‐vascularized construct showed a good performance in urethral reconstruction when applied in vivo. The study provided a novel strategy for tissue engineering of pre‐vascularized urethral construct for the defective urethra, representing a further advancement in urethral reconstruction.     

A dynamic in vitro model for evaluating antimicrobial activity against bacterial biofilms using a new device and clinical-used catheters

The activity of daptomycin compared to vancomycin against Staphylococcus epidermidis-biofilms on intravascular catheters has been evaluated using the new Sevilla device that enables to use medical grade-catheters, in an in vitro model that simulates the in vivo conditions. S. epidermidis-biofilms were obtained on polyurethane catheter segments using the Sevilla device linked to a continuous culture system for 24 h. To assess the antimicrobial activity, at this time the continuous culture system was changed to therapeutic antimicrobial concentration solutions for 48 h. At each 24 h interval time, catheter segments were taken out, washed and sonicated. Viable adherent bacteria were determined by agar plating. Data of surviving bacteria numbers attached to the catheter surface obtained with the Sevilla device showed a very good reproducibility. Daptomycin showed a good activity against S. epidermidis-biofilm on polyurethane catheter surface. After 48 h exposure to daptomycin, surviving adherent bacteria were reduced by 4 log compared to the control with no antimicrobial. Using the same model, vancomycin reduced bacterial survival by only 1.3 log. The Sevilla device enables antimicrobial agent activity against bacterial biofilms grown on the external surface of catheters used in clinical practice to be evaluated. The model used replicates as closely as possible the biofilm formed in a highly standardized way. Using this model, daptomycin demonstrates potent in vitro activity against S. epidermidis-biofilm on a polyurethane catheter; this activity was greater than that showed by vancomycin.     

Expression of cyclooxygenase-2 in the canine lower urinary tract with regard to the effects of gonadal status and gender

As pituitary gonadotrophins can induce prostaglandin (PG) synthesis and receptors for LH and FSH are present in the canine lower urinary tract (LUT), the objectives of this study were to (i) investigate the expression of COX-2, a key rate-limiting enzyme in PG production, in the canine LUT and (ii) determine if COX-2 expression differs between gender, gonadal status (intact and gonadectomised) and LUT regions. Four regions (body and neck of the bladder as well as proximal and distal urethra) of the LUT were obtained from 20 clinically healthy dogs (5 intact males, 5 intact anoestrous females, 4 castrated males, 6 spayed females). In situ hybridization and immunohistochemistry were performed to determine the presence of COX-2 mRNA and protein, respectively. The mRNA and protein expression was semi-quantitatively assessed. The scoring system combined both the distribution and intensity of positive staining and was carried out separately on the three tissue layers (epithelium, sub-epithelial stroma and muscle) for each of four regions of the LUT. In comparison to intact dogs, lower expression (P < 0.001) of COX-2 and its mRNA in gonadectomised males and females was observed in all tissue layers of each region of the LUT except in the distal urethra where there was no difference in mRNA expression between gonadal statuses. Regardless of region and tissue layer, intact females expressed more (P < 0.05) COX-2 and its mRNA than intact males. However, in gonadectomised dogs, mRNA expression of COX-2 did not differ between genders; males had higher (P < 0.001) protein level of COX-2 compared to females. In conclusion, both COX-2 and its mRNA were expressed in the canine LUT and COX-2-regulated PG synthesis in the canine LUT may differ between gonadal statuses and genders. The lower expression of COX-2 in gonadectomised dogs may impair normal function of the LUT and probably implicated in the development of neutering-induced urinary incontinence in the dog.     

Paleoenvironmental conditions preceding the Messinian Salinity Crisis in the Central Mediterranean: Integrated data from the Upper Miocene Trave section (Italy)

Integrated data of calcareous plankton and benthic foraminifers from the pre-evaporitic interval of Trave section (Central Italy) allowed the reconstruction of surface and bottom-water conditions in the Central Mediterranean during the interval from 7.61 to 6.33 Ma, preceding the Messinian Salinity Crisis.Our data point out a three-step paleoenvironmental evolution. During the first stage (7.61-7.02 Ma) benthic foraminiferal assemblages depict stable, well-oxygenated and ventilated bottom-water conditions, while the surface water records variable temperature and high nutrient conditions, probably associated with strong seasonality. The second stage (7.02-6.70 Ma) points to unfavourable bottom-water condition, triggered by deep-sea stagnation. This is witnessed by a significant decrease in oxygen concentration and biotic diversity, and by the presence of stress-tolerant taxa. A general warming of the surface water and a strongly stratified water column, characterized by an expanded mixed layer, are also recorded.From 6.70 Ma onwards (third stage), a prominent change to more restricted, low-oxygenated, hypersaline conditions at the sea floor is testified by the total disappearance of deep-dwelling planktonic foraminifers and the increasing abundance of stress-tolerant species. Calcareous plankton reflects high instability of the surface water in terms of nutrients, temperature and salinity. During this stage the environmental deterioration reaches intermediate depths in the water column.The initial change toward a step-wise isolation of the Central Mediterranean bottom-waters is probably related to a general warming, responsible for a first slowing-down of the vertical circulation, favouring stratification of surface and intermediate waters and stagnation of bottom-waters. This warming is related to the restricted connection between the Mediterranean Sea and the Atlantic Ocean, which occurred since 7.146 Ma.In the Trave section, the isolation of bottom-waters most likely occurred at the same time as in other Mediterranean sections. However, due to the presence of a hiatus it cannot be excluded that it occurred with a delay of ~ 100 kyr, probably related to the shallower paleodepth of the basin.     

Past, current and future thermal profiles of green turtle nesting grounds: Implications from climate change

Sex determination and hatching success in sea turtles is temperature dependent and as a result global warming poses a threat to sea turtles. Warmer sand temperatures may skew sea turtle population′s sex ratios towards predominantly females and decrease hatching success. Therefore, understanding the rates at which sand temperatures are likely to increase as climate change progresses is warranted. We recorded sand temperature and used historical sea surface and air temperature to model past and to predict future sand temperature under various scenarios of global warming at key sea turtle nesting grounds (n = 7) used by the northern Great Barrier Reef (nGBR) green turtle, Chelonia mydas, population. Reconstructed temperatures from 1990 to the present suggest that sand temperatures at the nesting sites studied have not changed significantly during the last 18 years. Current thermal profile at the nesting grounds suggests a bias towards female hatchling production into this population. Inter-beach thermal variance was observed at some nesting grounds with open areas in the sand dune at northern facing beaches having the warmest incubating environments. Our model projections suggest that a near complete feminization of hatchling output into this population will occur by 2070 under an extreme scenario of climate change (A1T emission scenario). Importantly, we found that some nesting grounds will still produce male hatchlings, under the most extreme scenario of climate change, this finding differs from predictions for other locations. Information from this study provides a better understanding of possible future changes in hatching success and sex ratios at each site and identifies important male producing regions. This allowed us to suggest strategies that can be used at a local scale to offset some of the impacts of warmer incubating temperatures to sea turtles.     

A novel approach to improve the efficacy of tumour ablation during cryosurgery

Freezing tumours and ablating it using cryosurgery is becoming a popular surgical procedure for treatment of carcinomas. In order to improve the efficiency of the cryosurgical procedure different approaches have been implemented till now, e.g., injecting high thermal conductivity fluid inside the tumour, low latent heat fluids inside the tumour prior to cryosurgery etc. These techniques improve the cryosurgical process to some extent but lack in minimising the damage to the surrounding healthy tissues. In this study, a novel concept is proposed which advocates the use of solutions with specific thermophysical properties around the interface of tumour. Numerical modelling has been done to determine the location of the ice fronts in the presence of this solution around the boundary of the tumour. It is noticed that in the presence of solution layer, owing to its distinct thermophysical properties like low thermal conductivity, not only the cellular destruction is enhanced but also the damage to the surrounding healthy tissue is minimised. Further, results indicate that this strategy leads to a faster ablation rate reducing the surgical time immensely. Also, an optimal offset, the minimum distance between the tip of cryoprobe and the boundary of the tumour, is identified for a given tumour radius with a given active length which gives maximum tumour necrosis in less time. This optimal offset which has been identified for each case will help the surgeons in proper planning of cryosurgery and improving the effectiveness of this technique greatly, making it a better treatment modality than its counterparts in many ways. It is also observed that for a 2 mm increase in activelength of the cryoprobe, the decrease in optimal offset is approximately 1 mm, i.e. optimal offset decreases linearly with an increase in the activelength for a given radius of the tumour. Also, for tumour with different radii, ranging between 10 mm to 15 mm, with same active length, the time taken for complete ablation by the larger tumour is nearly 2.7 times the time taken by the smaller one for every 2.5 mm increase in the tumour radius.     

Numerical simulation for heat transfer in prostate cancer cryosurgery

A comprehensive computational framework to simulate heat transfer during the freezing process in prostate cancer cryosurgery is presented. Tissues are treated as nonideal materials wherein phase transition occurs over a temperature range, thermophysical properties are temperature dependent and heating due to blood flow and metabolism are included. Boundary conditions were determined at the surfaces of the commercially available cryoprobes and urethral warmer by experimental study of temperature combined with a mathematical optimization process. For simulations, a suitable computational geometry was designed based on MRI imaging data of a real prostate. An enthalpy formulation-based numerical solution was performed for a prescribed surgical protocol to mimic a clinical freezing process. This computational framework allows for the individual planning of cryosurgical procedures and objective assessment of the effectiveness of prostate cryosurgery.     

Modulation of glutathione-related antioxidant defense system of fish chronically treated by the fungicide propiconazole

Recently, residual fungicides are generally recognized as relevant sources of aquatic environmental pollutants. However, the toxicological effects of these contaminants have not been adequately researched. In this study, the chronic effect of PCZ, a triazole-containing fungicide commonly present in aquatic environment, on GSH-related antioxidant system and oxidative stress indices of rainbow trout (Oncorhynchus mykiss) were investigated. Fish were exposed at sub-lethal concentrations of PCZ (0.2, 50 and 500 μg/L) for 7, 20 and 30 days. GSH levels and GSH-related enzyme activities, including GPx, GR and GST, were quantified in three tissues—liver, gill and muscle. The levels of LPO and CP were also measured as makers of oxidative damage. In addition, the correlations of the measured parameters in various tissues were evaluated by using PCA. The results of this study indicate that chronic exposure of PCZ has resulted in different responses in various tissues and the gill was the most sensitive tissue; however, before these parameters are used as potential biomarkers for monitoring residual fungicides in aquatic environment, more detailed experiments in laboratory need to be performed in the future.