Cryosurgery of Normal and Tumor Tissue in the Dorsal Skin Flap Chamber: Part I—Thermal Response

2001 ◽  
Vol 123 (4) ◽  
pp. 301-309 ◽  
Author(s):  
Nathan E. Hoffmann ◽  
John C. Bischof
Keyword(s):  
Blood Flow ◽  
Thermal Properties ◽  
Thermal History ◽  
Tumor Tissue ◽  
Normal Skin ◽  
Skin Flap ◽  
Companion Paper ◽  
Two Dimensional ◽  
Dorsal Skin ◽  
Freezing And Thawing

Current research in cryosurgery is concerned with finding a thermal history that will definitively destroy tissue. In this study, we measured and predicted the thermal history obtained during freezing and thawing in a cryosurgical model. This thermal history was then compared to the injury observed in the tissue of the same cryosurgical model (reported in companion paper (Hoffmann and Bischof, 2001)). The dorsal skin flap chamber, implanted in the Copenhagen rat, was chosen as the cryosurgical model. Cryosurgery was performed in the chamber on either normal skin or tumor tissue propagated from an AT-1 Dunning rat prostate tumor. The freezing was performed by placing a ∼1 mm diameter liquid-nitrogen-cooled cryoprobe in the center of the chamber and activating it for approximately 1 minute, followed by a passive thaw. This created a 4.2 mm radius iceball. Thermocouples were placed in the tissue around the probe at three locations (r=2, 3, and 3.8 mm from the center of the window) in order to monitor the thermal history produced in the tissue. The conduction error introduced by the presence of the thermocouples was investigated using an in vitro simulation of the in vivo case and found to be <10°C for all cases. The corrected temperature measurements were used to investigate the validity of two models of freezing behavior within the iceball. The first model used to approximate the freezing and thawing behavior within the DSFC was a two-dimensional transient axisymmetric numerical solution using an enthalpy method and incorporating heating due to blood flow. The second model was a one-dimensional radial steady state analytical solution without blood flow. The models used constant thermal properties for the unfrozen region, and temperature-dependent thermal properties for the frozen region. The two-dimensional transient model presented here is one of the first attempts to model both the freezing and thawing of cryosurgery. The ability of the model to calculate freezing appeared to be superior to the ability to calculate thawing. After demonstrating that the two-dimensional model sufficiently captured the freezing and thawing parameters recorded by the thermocouples, it was used to estimate the thermal history throughout the iceball. This model was used as a basis to compare thermal history to injury assessment (reported in companion paper (Hoffmann and Bischof, 2001)).

Cryosurgery of Normal and Tumor Tissue in the Dorsal Skin Flap Chamber: Part II—Injury Response

2001 ◽  
Vol 123 (4) ◽  
pp. 310-316 ◽  
Author(s):  
Nathan E. Hoffmann ◽  
John C. Bischof
Keyword(s):  
Vascular Injury ◽  
Normal Tissue ◽  
Tumor Tissue ◽  
Skin Flap ◽  
Hold Time ◽  
Companion Paper ◽  
Temperature History ◽  
Dorsal Skin ◽  
Tissue Lesion ◽  
Cellular Destruction

It has been hypothesized that vascular injury may be an important mechanism of cryosurgical destruction in addition to direct cellular destruction. In this study, we report correlation of tissue and vascular injury after cryosurgery to the temperature history during cryosurgery in an in vivo microvascular preparation. The dorsal skin flap chamber, implanted in the Copenhagen rat, was chosen as the cryosurgical model. Cryosurgery was performed in the chamber on either normal skin or tumor tissue propagated from an AT-1 Dunning rat prostate tumor, as described in a companion paper (Hoffmann and Bischof, 2001). The vasculature was then viewed at 3 and 7 days after cryoinjury under brightfield and FITC-labeled dextran contrast enhancement to assess the vascular injury. The results showed that there was complete destruction of the vasculature in the center of the lesion and a gradual return to normal patency moving radially outward. Histologic examination showed a band of inflammation near the edge of a large necrotic region at both 3 and 7 days after cryosurgery. The area of vascular injury observed with FITC-labeled dextran quantitatively corresponded to the area of necrosis observed in histologic section, and the size of the lesion for tumor and normal tissue was similar at 3 days post cryosurgery. At 7 days after cryosurgery, the lesion was smaller for both tissues, with the normal tissue lesion being much smaller than the tumor tissue lesion. A comparison of experimental injury data to the thermal model validated in a companion paper (Hoffmann and Bischof, 2001) suggested that the minimum temperature required for causing necrosis was −15.6±4.3°C in tumor tissue and −19.0±4.4°C in normal tissue. The other thermal parameters manifested at the edge of the lesion included a cooling rate of ∼28°C/min, 0 hold time, and a ∼9°C/min thawing rate. The conditions at the edge of the lesion are much less severe than the thermal conditions required for direct cellular destruction of AT-1 cells and tissues in vitro. These results are consistent with the hypothesis that vascular-mediated injury is responsible for the majority of injury at the edge of the frozen region in microvascular perfused tissue.

Cryo, Hyper or Both? Investigating Combination Cryo/Hyperthermia in the Dorsal Skin Flap Chamber

2000 ◽  
Author(s):  
Nathan E. Hoffmann ◽  
Bo H. Chao ◽  
John C. Bischof
Keyword(s):  
Combination Therapy ◽  
Thermal History ◽  
Standard Treatment ◽  
Tissue Injury ◽  
Skin Flap ◽  
Dorsal Skin ◽  
Combination Therapies ◽  
Disease Treatment ◽  
Copenhagen Rat

Abstract Combination therapies have been investigated as a mean to increase efficacy of disease treatment. For example, combinations such as radiation and chemotherapy, surgery and chemotherapy, and two different chemotherapies have become standard treatment for most cancers. Current theories suggest that vascular-mediated injury is an important mechanism of cryosurgical (reviewed in Gage and Baust (1998)) and hyperthermic destruction (Badylak et al., 1985; Dudar and Jain, 1984) in the treatment of solid tumors. These techniques appear complementary. Freezing creates vascular damage and promotes stasis within the vessels (Rabb et al., 1974), whereas hyperthermia creates cell and vascular destruction more effectively with a compromised vasculature (Shakil et al., 1999). Thus, in this study, we investigated the effect of combining these therapies on the vascular and tissue injury from the two therapies. We chose the dorsal skin flap chamber (DSFC) implanted in the Copenhagen rat as the cryosurgical model for this study. This in vivo freezing model allowed us to monitor thermal history and investigate both vascular and tissue injury in response to the combination therapy.

Observation of Vascular Injury After Freezing: Investigating the Response of Normal Skin and Subcutaneous AT-1 Tumor Tissue to Cryosurgery in the Dorsal Skin Flap Chamber

1999 ◽  
Author(s):  
Nathan E. Hoffmann ◽  
David J. Swanlund ◽  
John C. Bischof
Keyword(s):  
Vascular Injury ◽  
Thermal History ◽  
Host Response ◽  
Tissue Injury ◽  
Skin Flap ◽  
Tissue Type ◽  
Crystal Formation ◽  
Dorsal Skin ◽  
Tissue Necrosis

Abstract Two main mechanisms have been explored in an attempt to explain injury to the cells of tissues due to freezing in vivo. The first is direct cellular injury caused by injurious osmotic changes and ice crystal formation that happens as a result of freezing (Mazur, 1984). The second is host response injury caused by the vascular damage and immunologic response in response to freezing (Gage and Baust, 1998). The amount of injury caused by freezing appears to vary with tissue type and thermal history of the freezing protocol. The hypothesis of this study was that host response injury, specifically vascular injury, causes the majority of tissue necrosis at the edge of a frozen region and therefore determines the size of the lesion seen after in vivo freezing. Many investigations have previously made a qualitative correlation between thermal history, vascular injury, and tissue necrosis (e.g. Greene. 1943 and Rabb et al., 1974). We chose the dorsal skin flap chamber (DSFC) implanted in the Copenhagen rat as the cryosurgical model for this study. This in vivo freezing model appears insensitive to the immunologic phenomenon (Hoffmann et al., 1999) and allows us to monitor thermal history and investigate both vascular and tissue injury in response to cryosurgery.

Thermal Therapy of Prostate Tumor Tissue in the Dorsal Skin Flap Chamber

2002 ◽  
Vol 64 (1) ◽  
pp. 170-173 ◽  
Author(s):  
Sankha Bhowmick ◽  
Nathan E. Hoffmann ◽  
John C. Bischof
Keyword(s):  
Tumor Tissue ◽  
Skin Flap ◽  
Prostate Tumor ◽  
Thermal Therapy ◽  
Dorsal Skin

scholarly journals Efficacy and mechanism of adenovirus-mediated VEGF-165 gene therapy for augmentation of skin flap viability

2006 ◽  
Vol 291 (1) ◽  
pp. H127-H137 ◽  
Author(s):  
Ning Huang ◽  
Asim Khan ◽  
Homa Ashrafpour ◽  
Peter C. Neligan ◽  
Christopher R. Forrest ◽  
...  
Keyword(s):  
Gene Therapy ◽  
Blood Flow ◽  
Protein Expression ◽  
Skin Flap ◽  
Capillary Density ◽  
Distal Portion ◽  
Dorsal Skin ◽  
Flap Viability ◽  
Enos Protein Expression ◽  
Enos Protein

Skin ischemic necrosis due to vasospasm and/or insufficient vascularity is the most common complication in the distal portion of the skin flap in reconstructive surgery. This project was designed to test our hypothesis that preoperative subdermal injection of adenoviral vectors encoding genes for vascular endothelial growth factor-165 (Ad.VEGF-165) or endothelial nitric oxide (NO) synthase (Ad.eNOS) effectively augments skin viability in skin flap surgery and that the mechanism of Ad.VEGF-165 gene therapy involves an increase in synthesis/release of the angiogenic and vasodilator factor NO. PBS (0.5 ml) or PBS containing Ad.VEGF-165, Ad.eNOS, or adenovirus (Ad.Null) was injected subdermally into the distal half of a mapped rat dorsal skin flap (4 × 10 cm) 7 days preoperatively, and skin flap viability was assessed 7 days postoperatively. Local subdermal gene therapy with 2 × 107–2 × 1010 plaque-forming units of VEGF-165 increased skin flap viability compared with PBS- or Ad.Null-injected control ( P < 0.05). Subdermal Ad.VEGF-165 and Ad.eNOS gene therapies were equally effective in increasing skin flap viability at 5 × 108 plaque-forming units. Subdermal Ad.VEGF-165 therapy was associated with upregulation of eNOS protein expression, Ca2+-dependent NOS activity, synthesis/release of NO, and increase in capillary density and blood flow in the distal portion of the skin flap. Injection of the NOS inhibitor Nω-nitro-l-arginine (15 mg/kg im), but not the cyclooxygenase inhibitor indomethacin (5 mg/kg im), 45 min preoperatively completely abolished the increase in skin flap blood flow and viability induced by Ad.VEGF-165 injected subdermally into the mapped skin flap 7 days preoperatively. We have demonstrated for the first time that 1) Ad.VEGF-165 and Ad.eNOS mapped skin flap injected subdermally into the mapped skin flap 7 days preoperatively are equally effective in augmenting viability in the rat dorsal skin flap compared with control, 2) the mechanism of subdermal Ad.VEGF-165 gene therapy in augmenting skin flap viability involves an increase in NO synthesis/release downstream of upregulation of eNOS protein expression and Ca2+-dependent NOS activity, and 3) the vasodilating effect of NO may predominantly mediate subdermal Ad.VEGF gene therapy in augmenting skin flap blood flow and viability.

Three-Dimensional Structure of Cloned T3 Connector Protein at 1.6nm Resolution

1990 ◽  
Vol 48 (1) ◽  
pp. 282-283
Author(s):  
José L. Carrascosa ◽  
José M. Valpuesta ◽  
Hisao Fujisawa
Keyword(s):  
Dna Sequences ◽  
Expression Vector ◽  
Three Dimensional ◽  
Deae Cellulose ◽  
Dna Packaging ◽  
Dimensional Structure ◽  
Two Dimensional ◽  
Freezing And Thawing ◽  
Three Dimensional Structure ◽  
Dimensional Reconstruction

The head to tail connector of bacteriophages plays a fundamental role in the assembly of viral heads and DNA packaging. In spite of the absence of sequence homology, the structure of connectors from different viruses (T4, Ø29, T3, P22, etc) share common morphological features, that are most clearly revealed in their three-dimensional structure. We have studied the three-dimensional reconstruction of the connector protein from phage T3 (gp 8) from tilted view of two dimensional crystals obtained from this protein after cloning and purification.DNA sequences including gene 8 from phage T3 were cloned, into Bam Hl-Eco Rl sites down stream of lambda promotor PL, in the expression vector pNT45 under the control of cI857. E R204 (pNT89) cells were incubated at 42°C for 2h, harvested and resuspended in 20 mM Tris HC1 (pH 7.4), 7mM 2 mercaptoethanol, ImM EDTA. The cells were lysed by freezing and thawing in the presence of lysozyme (lmg/ml) and ligthly sonicated. The low speed supernatant was precipitated by ammonium sulfate (60% saturated) and dissolved in the original buffer to be subjected to gel nitration through Sepharose 6B, followed by phosphocellulose colum (Pll) and DEAE cellulose colum (DE52). Purified gp8 appeared at 0.3M NaCl and formed crystals when its concentration increased above 1.5 mg/ml.

Graphene and Graphene-Based Materials in Biomedical Applications

2019 ◽  
Vol 26 (38) ◽  
pp. 6834-6850 ◽  
Author(s):  
Mohammad Omaish Ansari ◽  
Kalamegam Gauthaman ◽  
Abdurahman Essa ◽  
Sidi A. Bencherif ◽  
Adnan Memic
Keyword(s):  
Tissue Engineering ◽  
Thermal Properties ◽  
Gene Delivery ◽  
Regenerative Medicine ◽  
Biomedical Research ◽  
Biomedical Applications ◽  
Biomedical Application ◽  
Two Dimensional ◽  
Drug And Gene Delivery ◽  
Biomedical Fields

: Nanobiotechnology has huge potential in the field of regenerative medicine. One of the main drivers has been the development of novel nanomaterials. One developing class of materials is graphene and its derivatives recognized for their novel properties present on the nanoscale. In particular, graphene and graphene-based nanomaterials have been shown to have excellent electrical, mechanical, optical and thermal properties. Due to these unique properties coupled with the ability to tune their biocompatibility, these nanomaterials have been propelled for various applications. Most recently, these two-dimensional nanomaterials have been widely recognized for their utility in biomedical research. In this review, a brief overview of the strategies to synthesize graphene and its derivatives are discussed. Next, the biocompatibility profile of these nanomaterials as a precursor to their biomedical application is reviewed. Finally, recent applications of graphene-based nanomaterials in various biomedical fields including tissue engineering, drug and gene delivery, biosensing and bioimaging as well as other biorelated studies are highlighted.

Sign in / Sign up

Export Citation Format

Share Document