Critical temperature for skin necrosis in experimental cryosurgery

To investigate the minimal lethal freezing temperature required to produce skin necrosis in dogs, multiple skin sites were frozen with cryosurgical equipment. Tissue temperatures were recorded from thermocouple sites placed at diverse distances, usually 5 mm from the edge of the freezing probe. In single freezing cycles of about 3 min duration, tissue temperatures in the range of 0 to ?60 °C were produced. Punch biopsies of the skin at the thermocouple sites 3 days after freezing injury provided tissues for estimation of viability by histologic examination.The histologic findings permitted classification of the biopsy tissue into three groups, that is, viable, borderline, or necrotic. When classified as borderline, the division between the necrotic and viable tissue was evident on the histologic slide. The viable specimens were scattered through the 0 to ?35 °C range. All specimens frozen to ?10 °C or warmer were viable. In biopsies classified as borderline, the range of viability extended from ?11 ° to ?50 °C. The necrotic biopsies covered a range of ?14 ° to ?50 °C. Cell death was certain at temperatures colder than ?50 °C. The data showed cryosurgical freezing conditions produced a range of temperatures in which viability or death of tissue may occur and that the ranges of viability and necrosis overlapped to a great extent.The wide range of temperatures at which cells were viable shows the need to achieve tissue temperatures in the range of ?50 °C in the cryosurgical treatment of cancer.     

Flounder antifreeze peptides increase the efficacy of cryosurgery

Type I antifreeze protein (AFP) from the winter flounder (Pseudopleuronectes americanus) was used as an adjuvant to cryosurgery of subcutaneous tumors of Dunning AT-1 rat prostate cells grown in Copenhagen rats. The cryosurgical procedure was performed with a commercially available cryosurgery device (CRYO-HIT, Galil Medical) with clinically relevant single- and double-freeze protocols. Injury was assessed with the alamar blue indicator of metabolic activity. The assay gave anomalous results when used to assess the extent of injury immediately following the procedure, underestimating the extent of injury. However, a double-freeze procedure with antifreeze protein present was found to give significantly better ablation than a double-freeze without AFP or a single-freeze with or without AFP.     

The safety and efficacy of breast implants for augmentation mammaplasty

This review of the efficacy and safety of breast implants was intended to focus on our current body of knowledge about these devices. There are informational gaps, but not all of these can be laid at the door of imperfect studies or failed scientific methods. Certain properties of the implants are still unmeasurable, immunologic investigation is still evolving, the cause of wound contraction is inexplicable here or in the burnscar contracture, and the indications for and results of this surgery necessarily are subjective. Still, there are a number of investigative avenues open to us, and our cumulative experience shows no reluctance on the part of plastic surgeons to initiate further studies.     

Immunological response of regional lymph nodes after tumor cryosurgery: experimental study in rats

Seven days after inoculation of metastasizing rat mammary tumor No. 1 into the thigh of 5-week-old female Sprague-Dawley rats, the tumor was treated cryosurgically by two-cycle freezing and by contact methods at -170 degrees C. Weights of the thymus and the spleen, histological findings of the lumbar lymph nodes, phytohemagglutinin (PHA)-induced blastogenesis of lymphocytes obtained from the lumbar lymph nodes and peripheral blood, and resistance rate to tumor rechallenge were examined 1, 3, 6, 10, and 17 week(s) after cryosurgery, with the following results: Thymus weight gradually decreased by 3 weeks after cryosurgery, while spleen weight increased by 1 week, recovering the preoperative level at 6 weeks. Paracortical hyperplasia of the lumbar lymph nodes markedly increased in 1 week and sinus histiocytosis increased after 3 weeks, both remaining at high values until 10 weeks, while germinal center hyperplasia showed a high value at 3 weeks and thereafter decreased gradually. PHA-induced blastogenesis of the lumbar lymph nodes significantly increased 1 week after cryosurgery and remained at its high value until 10 weeks. PHA-induced blastogenesis of peripheral lymphocytes showed the lowest value at 3 weeks and then significantly increased at 6 weeks. Resistance rate to rechallenge showed the lowest value at 3 weeks, reaching the highest level 10 weeks after cryosurgery. From the above results, it was suggested that anti-tumor immunity (resistance to tumor rechallenge) induced by cryosurgery was at the lowest level at 3 weeks after cryosurgery, and gradually increased starting at 6 weeks.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of varying freezing and thawing rates in experimental cryosurgery

Six different freezing/thawing programs, which varied freezing rate, duration of freezing, and thawing rates, were used to investigate the effect of these factors on cell destruction in dog skin. The range of tissue temperatures produced was from -15 to -50 degrees C. The extent of destruction was evaluated by skin biopsies 3 days after cold injury. In single, short freezing/thawing cycles, the temperature reached in the tissue was the prime factor in cell death. Longer freezing time and slow thawing were also important lethal factors which increased destruction of cells. Cooling rate, whether slow or fast, made little difference in the outcome. The experiments suggested that present-day, commonly employed cryosurgical techniques, which feature fast cooling, slow thawing, and repetition of the freeze/thaw cycle, should be modified by the use of maintenance of the tissue in the frozen state for several minutes and slow thawing. Thawing should be complete before freezing is repeated. These modifications in technique will maximize tissue destruction, an important consideration in cancer cryosurgery.     

Human insulin: study of safety and efficacy in man.

The safety and efficacy of a new highly purified neutral soluble human insulin produced by conversion of porcine insulin was compared with a highly purified neutral soluble porcine insulin in six normal men. The insulins were administered by subcutaneous injection at a dose of 0.075 U/kg body weight. Somatostatin was infused during the experiment to suppress endogenous insulin secretin. No difference was found in the plasma glucose, insulin, or metabolite responses. Thus the potency, onset, and duration of effect were identical with the two insulins. No short-term side effects to either insulin were observed. Highly purified, semi-synthetic human insulin offers a safe and effective means to explore the possible advantages of homologous human insulin in the management of diabetes mellitus.     

The effect of exenatide re-exposure on safety and efficacy

Exenatide, a synthetic peptide originally isolated from salivary secretions of Heloderma suspectum, like other subcutaneously injected peptides, can cause antibody formation. Despite that antibody formation has been observed in some patients, results from previous clinical trials have not shown safety and efficacy concerns in exenatide-naïve patients. The objective of this multicenter, open-label study was to investigate the response of anti-exenatide antibody formation and the incidence of immune-related and hypersensitivity reactions after exenatide re-exposure. Fifty-eight patients (57% male; 59 ± 10 years; weight 85 ± 19 kg; HbA1c 8.1 ± 0.9%; duration of diabetes 10 ± 5 years) were enrolled. At study initiation, 98.3% of patients were taking 1 or more antidiabetes drugs, including oral medication and various types of insulin. Treatment-emergent adverse events (TEAEs) at any time during the study were observed in 40 and 47% of patients with positive and negative treatment-emergent antibodies, respectively. Immune-related AEs were observed in 6 patients (4 were antibody positive). These AEs had not been reported in their previous exposure to exenatide. Re-exposure to exenatide did not result in increased hypersensitivity reactions. Overall, 72% of patients had a baseline to endpoint reduction in HbA1c (range −0.1 to −2.8%), and 87% of antibody negative versus 62% of antibody positive patients had an HbA1c endpoint reduction. The study design and the patients’ baseline characteristics, including diabetes treatment at study initiation, are confounding factors limiting clinical conclusions on exenatide's glycemic effect in this patient population. The study results indicate that anti-exenatide antibody formation did not increase the incidence of TEAEs in patients re-exposed to exenatide.     

凝结芽胞杆菌(TBC169)片治疗便秘的实验研究和临床疗效

目的观察凝结芽胞杆菌片（BC1）对便秘的药理作用和I临床疗效。方法昆明种雄性小鼠随机分为6组（每组10只）。BC1片（3个剂量）和BCz片治疗组小鼠口服BC。片和BC2片,空白对照组小鼠和模型对照组小鼠口服自来水,每天1次,共7d。之后,两治疗组和模型对照组小鼠在禁食12h后．均口服复方地芬诺酯（CDX）片,引发便秘。成人慢性便秘38例患者随机分为治疗组（20例）和对照组（18例）,分别口服BC1片和金双歧片（BG）,每天3次,共14～21d。结果BC1片能明显地减少便秘小鼠的首次排便时间（P〈0．05）和显著地增加大便粒数及重量（P〈0．05）。在临床试验中,治疗成人慢性便秘,BC1片的治愈率为45％,总有效率为70％,而相对的BG片分别为44％和72％,两药均未见不良反应或副作用。结论BC1片对小鼠实验性便秘和成人慢性便秘均有明显的治疗作用,在临床试验中未见不良反应或副作用。     

Effects of cryosurgery in experimental carcinoma on lectin binding and keratin distribution

Histochemical alterations of lectin binding and keratin distribution in experimental carcinomas of the hamster cheek pouch were obtained following cryotreatment. Cryotreated carcinoma cells showed a characteristic reduction in lectin binding and keratin staining shortly following cryosurgery. Tumor tissue, on the 2nd and 3rd days after cryotreatment, displayed destruction and necrosis with almost a complete loss of lectin binding and keratin staining. The remaining neoplastic cells located in the deeper layer showed positive reaction for both lectin binding and keratin, which is indicative of tumor recurrence. Histochemical staining of lectin binding and keratin proteins were useful markers in cryotreated tumor cells to identify either destruction and necrosis or vital activity of neoplastic growth.     

Pre-clinical efficacy and safety of experimental vaccines based on non-replicating vaccinia vectors against yellow fever

Background

Currently existing yellow fever (YF) vaccines are based on the live attenuated yellow fever virus 17D strain (YFV-17D). Although, a good safety profile was historically attributed to the 17D vaccine, serious adverse events have been reported, making the development of a safer, more modern vaccine desirable.

Methodology/Principal Findings

A gene encoding the precursor of the membrane and envelope (prME) protein of the YFV-17D strain was inserted into the non-replicating modified vaccinia virus Ankara and into the D4R-defective vaccinia virus. Candidate vaccines based on the recombinant vaccinia viruses were assessed for immunogenicity and protection in a mouse model and compared to the commercial YFV-17D vaccine. The recombinant live vaccines induced γ-interferon-secreting CD4- and functionally active CD8-T cells, and conferred full protection against lethal challenge already after a single low immunization dose of 10⁵ TCID₅₀. Surprisingly, pre-existing immunity against wild-type vaccinia virus did not negatively influence protection. Unlike the classical 17D vaccine, the vaccinia virus-based vaccines did not cause mortality following intracerebral administration in mice, demonstrating better safety profiles.

Conclusions/Significance

The non-replicating recombinant YF candidate live vaccines induced a broad immune response after single dose administration, were effective even in the presence of a pre-existing immunity against vaccinia virus and demonstrated an excellent safety profile in mice.     

Tissue impedance and temperature measurements in relation to necrosis in experimental cryosurgery

Tissue temperature and impedance were measured in dog skin during freezing in situ. The previously frozen skin was removed by punch biopsies 3 days later to permit microscopic evaluation of the extent of necrosis. The histologic observations were related to the temperature and impedance measurements in an effort to determine the usefulness of the monitoring techniques in clinical cryosurgery. Tissue temperature and impedance have a definite relationship in tissue freezing, but the range of temperatures about any impedance values causes some concern. The tissue biopsies showed that an impedance value of at least 10 Mohms is not always associated with tissue death. In these experiments, there was the usual range of temperatures in relation to tissue death, but tissue temperatures of -30 degrees C and colder were always associated with complete necrosis. It is concluded that tissue temperatures are the more accurate and useful monitoring technique to supplement clinical judgment. However, impedance techniques may also be used to monitor therapy, especially if used primarily to monitor depth of therapy, and if controlled by clinical judgment wary of the inaccuracy of the technique.     

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 prediction of freezing fronts in cryosurgery: comparison with experimental results

Recent developments in scientific computing now allow to consider realistic applications of numerical modelling to medicine. In this work, a numerical method is presented for the simulation of phase change occurring in cryosurgery applications. The ultimate goal of these simulations is to accurately predict the freezing front position and the thermal history inside the ice ball which is essential to determine if cancerous cells have been completely destroyed. A semi-phase field formulation including blood flow considerations is employed for the simulations. Numerical results are enhanced by the introduction of an anisotropic remeshing strategy. The numerical procedure is validated by comparing the predictions of the model with experimental results.