The relative thermal stability of tissue macromolecules and cellular structure in burn injury

Thermal effect on eyelid and tear film after low-level light therapy and warm compress

CLINICAL RELEVANCE

The warming effect of low-level light therapy may contribute to its therapeutic mechanism which is beneficial for dry eye management.

BACKGROUND

Low-level light therapy is proposed to work via cellular photobiomodulation and a potential thermal effect in dry eye management. This study examined the change in eyelid temperature and tear film stability after low-level light therapy compared to warm compress.

METHODS

Participants with no to mild dry eye disease were randomised into control, warm compress, and low-level light therapy groups. The low-level light therapy group was treated with Eyelight mask (633 nm) for 15 minutes, the warm compress group with Bruder mask for 10 minutes, and the control group with an Eyelight mask having inactive LEDs for 15 minutes. Eyelid temperature was measured using the FLIR One® Pro thermal camera (Teledyne FLIR, Santa Barbara, CA, USA), and clinical measures of tear film stability were evaluated before and after treatment.

RESULTS

Thirty-five participants (mean age ± SD, 27.3 ± 4.3 years) completed the study. Eyelid temperatures for external upper, external lower, internal upper and internal lower eyelids were significantly greater in the low-level light therapy and warm compress groups immediately after treatment compared to the control group (all p < 0.001). No difference in temperature was observed between the low-level light therapy and warm compress groups at all time points (all p > 0.05). Tear film lipid layer thickness was significantly greater after treatment (mean (95% CI), 13.1 nm (5.3 to 21.0), p < 0.005) but not different between groups (p > 0.05).

CONCLUSION

A single treatment of low-level light therapy increased eyelid temperature immediately after treatment, but the increase was not significantly different from warm compress. This suggests that thermal effects may in part contribute to the therapeutic mechanism of low-level light therapy.

Eyelid Warming Devices: Safety, Efficacy, and Place in Therapy

Meibomian gland dysfunction (MGD) is characterized by the obstruction and/or inflammation of the meibomian glands that result in decreased and altered meibum secretion. This results in deficiencies in the tear film lipid layer which contributes to increased evaporation and destabilization of the tear film. One of the mainstay therapies for MGD is medical devices that apply heat and/or pressure to the eyelids and promote the liquification and outflow of meibum into the tear film. Over the past two decades, there have been a surge of interest in diagnosing and managing MGD. As a result, numerous medical devices have been developed and each have their own unique approach to treating MGD. This narrative review was conducted to summarize the current state of knowledge on eyelid warming devices, specifically warm eye coverings, devices that direct heat and/or pressure to the eyelids, moisture chamber goggles, and light-based therapy. This review summarized 58 human clinical studies and found that most eyelid warming devices were efficacious in improving signs and symptoms in a wide range of MGD severities and were generally safe to use.

Design and Characterization of a Bioinspired Polyvinyl Alcohol Matrix with Structural Foam-Wall Microarchitectures for Potential Tissue Engineering Applications

Traditional medical soft matrix used in a surgical treatment or in wound management was not good enough in both the structural support and interconnectivity to be applied in tissue engineering as a scaffold. Avian skeleton and feather rachises might be good reference objects to mimic in designing a scaffold material with good structural support and high interconnectivity because of its structural foam-wall microarchitectures and structural pneumaticity. In this study, a biomimetic airstream pore-foaming process was built up and the corresponding new medical soft matrix derived from polyvinyl alcohol matrix (PVAM) with air cavities inspired by avian skeleton and feather rachises was prepared. Furthermore, the resulting medical soft matrix and bovine Achilles tendon type I collagen could be employed to prepare a new collagen-containing composite matrix. Characterization, thermal stability and cell morphology of the bioinspired PVA matrix and the corresponding collagen-modified PVA composite matrix with open-cell foam-wall microarchitectures were studied for evaluation of potential tissue engineering applications. TGA, DTG, DSC, SEM and FTIR results of new bioinspired PVA matrix were employed to build up the effective system identification approach for biomimetic structure, stability, purity, and safety of target soft matrix. The bioinspired PVA matrix and the corresponding collagen-modified PVA composite matrix would be conductive to human hepatoblastoma HepG2 cell proliferation, migration, and expression which might serve as a promising liver cell culture carrier to be used in the biological artificial liver reactor.

Damage integral and other predictive formulas for nonisothermal heating during laser exposure

SIGNIFICANCE

Physics-based models supply simulated temperature rises to photothermal damage rate models and provide comprehensive risk assessments for laser-induced damage. As the physics-based models continue to be refined, the damage rate models have not advanced. This peculiar lack of improvement is counterintuitive considering the damage integral (Ω), originally derived for isothermal heating events, and fails to accurately represent the nonisothermal heating from short laser exposures.

AIM

Derive a nonisothermal form of the damage integral and predict more accurately the damage induced by short laser exposures, as well as identify the role of heating rate in laser damage.

APPROACH

From first principles, we derived a version of the damage integral specific to the shape of thermal profiles rather than the square function provided by Arrhenius plots. We used previously published threshold thermal profiles, where all nonisothermal frequency factors (Anon) solved all Ωnon values to unity. Nonisothermal correction factors correct isothermal Aiso values.

RESULTS

The Ea values were identical for both the isothermal and nonisothermal conventions. Correction factor values for Ωiso ranged from 0.0 (20-s exposures at thermal steady state) to -0.93 (0.05-s exposures). Based on empirical results, we have derived a two-dimensional empirical formula that predicts the heating rate as a function of exposure duration and ambient temperature. Threshold peak temperatures (Tpthr) and threshold critical temperatures are mathematically determined without thermal profiles when appropriate Ea and Anon values are established.

CONCLUSIONS

We have identified a modified damage integral that does not rely on the Arrhenius plot and provides a value for the frequency factor (A) that accounts for the nonisothermal nature of short laser exposures. The method, validated in our in vitro retinal model, requires thermal profiles recorded under threshold conditions, such as at minimum visible lesions or the boundary of cell death. The method is a new option for laser damage modelers.

A Single-center Retrospective Trial of a Blink-assisted Eyelid Device in Treating the Signs and Symptoms of Dry Eye

SIGNIFICANCE

The clinical features of meibomian gland disease include altered tear film stability, damage to the ocular surface, symptoms of ocular surface irritation, and visual fluctuations. Finding an adequate treatment to alleviate a patient's signs and symptoms is vital to caring for those with dry eye disease resulting from meibomian gland disease.

PURPOSE

The purpose of this analysis was to determine whether the controlled heating of meibomian glands with the SmartLid devices (TearCare) combined with evacuation of the liquefied meibum using a handheld clearance assistant would improve a patient's dry eye symptoms (as measured by the Standardized Patient Evaluation of Eye Dryness [SPEED] questionnaire) and signs (as measured by meibomian gland expression [MGE] scores).

METHODS

This study involved a retrospective analysis of data gathered in a single-center ophthalmology/optometry practice. The symptom frequency and severity were assessed using the SPEED questionnaire, and the signs were assessed via MGE scores before and after (8 to 12 weeks) treatment. A further analysis evaluating efficacy in subgroups based on age, race, and sex was performed. A statistical analysis was performed with t tests for group comparisons.

RESULTS

A SPEED questionnaire was answered by 92 patients with dry eye disease. In addition, each patient's meibomian gland function was recorded as MGE scores for each eye (176 eyes). These procedures were completed before and approximately 8 weeks after a single bilateral TearCare treatment. The median total SPEED score was reduced from 16 to 9, and the total MGE scores improved from 5.0 to 9.0 in the right eye and 4.0 to 9.0 in the left eye after a single TearCare treatment.

CONCLUSIONS

A single TearCare treatment was effective in reducing both the signs and symptoms of dry eye in all subjects.

Prospective trial of a 2940 nm Er:YAG laser for the treatment of meibomian gland dysfunction

PURPOSE

The primary objective was to evaluate the efficacy and safety of Er:YAG laser treatment for meibomian gland dysfunction (MGD) in a prospective study.

METHODS

A total of 128 eyes from 64 patients with MGD were enrolled to receive either three Er:YAG laser treatments with meibomian gland expression (MGX) or MGX-alone treatment sessions at 3-week intervals. The Standard Patient Evaluation of Eye Dryness (SPEED) validated questionnaire; fluorescein breakup time of the tear film (FBUT); corneal fluorescein staining (CFS); lid margin abnormalities; meibomian gland morphology (meiboscore); lower tear meniscus height (TMH); and assessment of 15 meibomian glands in the lower eyelids, including total meibomian gland secretion quality (TMGS), the number of glands secreting any liquid (GSAL), and the number of glands yielding optimal clear liquid secretion (GYCL), were assessed at day (D)0, D21, D42, and D63 for the Er:YAG-MGX group and D0 and D63 for the MGX group.

RESULTS

At D63, significant decreases in SPEED scores and lid margin abnormalities as well as significant increases in FBUT, TMGS, and GSAL were observed in both groups (all p < 0.05). The Er:YAG-MGX group showed a significantly better improvement in SPEED scores, TMGS, and GYCL than the MGX group (all p < 0.05).

CONCLUSION

Although preliminary, the study results of Er:YAG laser treatment for dry eye syndrome caused by MGD are promising. Er:YAG laser treatment may be a new direction for managing MGD.

TRIAL REGISTRATION

The study was registered at www.chictr.org.cn : ChiCTR1900026004.

The Physics of Magnetic Resonance Imaging Safety

Magnetic resonance (MR) imaging relies on a strong static magnetic field in conjunction with careful orchestration of pulsed linear gradient magnetic fields and radiofrequency magnetic fields in order to generate images. The interaction of these fields with patients as well as materials with magnetic or conducting properties can be a source of risk in the MR environment. This article provides a basic review of the physical underpinnings of the primary risks in MR imaging to foster development of intuition with respect to both patient and risk management in the MR environment.

Therapeutic Instruments Targeting Meibomian Gland Dysfunction

The most prevalent type of meibomian gland dysfunction (MGD), which is obstructive, is the main cause of evaporative dry eye and is characterized by changes in the meibum composition and duct obstruction. Eyelid hygiene has usually been the most common clinical approach. However, alternative therapies for MGD are emerging on the market. Some warming and humidity devices have led to an improvement in the signs and symptoms in MGD patients. Likewise, eyelid massaging and cleaning devices are also beneficial for ocular signs and symptoms; however, patients usually need more than one session to maintain the therapeutic effect. Thermal pulsation has been reported to be more efficient than other strategies, and the effects can last up to 12 months. Moreover, intense pulsed light therapy has been demonstrated to improve ocular signs and symptoms alone and in combination with other therapies. Proper counseling of clinicians considering MGD status and patient compliance will help patients to undergo the adequate technique that best suits their condition.

Coming to Consensus: What Defines Deep Partial Thickness Burn Injuries in Porcine Models?

Deep partial thickness burns are clinically prevalent and difficult to diagnose. In order to develop methods to assess burn depth and therapies to treat deep partial thickness burns, reliable, accurate animal models are needed. The variety of animal models in the literature and the lack of precise details reported for the experimental procedures make comparison of research between investigators challenging and ultimately affect translation to patients. They sought to compare deep partial thickness porcine burn models from five well-established laboratories. In doing so, they uncovered a lack of consistency in approaches to the evaluation of burn injury depth that was present within and among various models. They then used an iterative process to develop a scoring rubric with an educational component to facilitate burn injury depth evaluation that improved reliability of the scoring. Using the developed rubric to re-score the five burn models, they found that all models created a deep partial thickness injury and that agreement about specific characteristics identified on histological staining was improved. Finally, they present consensus statements on the evaluation and interpretation of the microanatomy of deep partial thickness burns in pigs.

Too Hot to Handle-Quantifying Temperature Variations in the Nasal Endoscope Ocular Assembly and Light Post

Background

Nasal endoscopes have transformed and improved the safety of intranasal and transnasal surgery. The heat they can produce may, however, reach dangerous levels for surgeons. Studies have not previously assessed the temperature of the nasal endoscope light post/ocular assembly (LP/OA)—where the surgeon usually holds the endoscope.

Objective

This study aims to understand the effect of different nasal endoscopes, light sources, and light cords on the LP/OA temperature.

Methods

We measured the temperature at the LP/OA of various rigid nasal endoscopes at multiple time intervals over 30 minutes, as well as after turning off the light source and irrigating the LP/OA with 10 mL of saline.

Results

The highest temperature recorded was 67.37°C at the LP/OA at 30 minutes, using a new light cord, older endoscope, and 184-hour xenon light bulb. In every trial, the temperature of the LP/OA continually increased until 30 minutes when the light source was turned off. Statistically significant ( P < .001) temperature differences were seen in trials using the older xenon light sources. The light-emitting diode light source was significantly cooler with an older light cord regardless of the age of the scope ( P = .003).

Conclusion

Endoscope temperatures during sinus surgery may reach potentially dangerous levels at the LP/OA region. These temperatures may be sufficient to cause second-degree burns during normal usage. Factors associated with higher endoscope temperatures include longer times with the light source on and xenon light bulbs.

Therapeutic profile of a latent heat eyelid warming device with temperature setting variation

PURPOSE

To compare the effects on ocular temperature and tear film parameters following a single application of a latent heat eyelid warming device at a range of temperature settings.

METHODS

Fifteen subjects were enrolled in a prospective, investigator-masked, randomised, cross-over trial. On separate days, participants were randomised to 10-minute application of a research latent heat device (Laboratoires Théa) at device temperature settings of 45 °C, 50 °C and 55 °C. Outer eyelid and corneal temperatures, tear film lipid layer grade, and non-invasive tear film breakup time (NIBUT) were measured at baseline and immediately after 10 min of device application.

RESULTS

Baseline measurements did not differ between treatment groups (all p > 0.05). Ocular temperatures, lipid layer grade and non-invasive tear film stability rose significantly following device application in all treatment groups (all p < 0.05). The 55 °C setting effected a mean ocular surface temperature rise in the order of +4 °C from baseline, which was 1.46 and 1.26 times greater than at the 45 °C and 50 °C temperature settings, respectively (all p < 0.05). Similarly, improvements in mean non-invasive tear film stability from baseline in the order of +7 s were observed, which were 2.43 and 1.66 times greater than those at the lower temperature settings of 45 °C and 50 °C, respectively (all p < 0.05).

CONCLUSIONS

At all temperature settings, the latent heat device resulted in clinically and statistically significant increases in ocular temperature, lipid layer grade, and non-invasive tear film stability. However, the 55 °C setting proved to be most effective at raising ocular temperature (in the order of +4 °C from baseline) and improving tear film stability.

Cell salvage in acute and chronic wounds: a potential treatment strategy. Experimental data and early clinical results

On 9 May 2018, the authors took part in a closed panel discussion on the impact of cell salvage in acute and chronic wounds. The goal was to deliberate the possible use of plurogel micelle matrix (PMM) as a new treatment strategy for wound healing and the authors openly shared their experiences, thoughts, experimental data and early clinical results. The outcome of the panel discussion has been abridged in this paper. The cell membrane consists of a lipid bilayer, which provides a diffusion barrier separating the inside of a cell from its environment. Cell membrane injury can result in acute cellular necrosis when defects are too large and cannot be resealed. There is a potential hazard to the body when these dying cells release endogenous alarm signals referred to as 'damage (or danger) associated molecular patterns' (DAMPs), which trigger the innate immune system and modulate inflammation. Cell salvage by membrane resealing is a promising target to ensure the survival of the individual cell and prevention of further tissue degeneration by inflammatory processes. Non-ionic surfactants such as poloxamers, poloxamines and PMM have the potential to resuscitate cells by inserting themselves into damaged membranes and stabilising the unstable portions of the lipid bilayers. The amphiphilic properties of these molecules are amenable to insertion into cell wall defects and so can play a crucial, reparative role. This new approach to cell rescue or salvage has gained increasing interest as several clinical conditions have been linked to cell membrane injury via oxidative stress-mediated lipid peroxidation or thermal disruption. The repair of the cell membrane is an important step in salvaging cells from necrosis to prevent further tissue degeneration by inflammatory processes. This is applicable to acute burns and chronic wounds such as diabetic foot ulcers (DFUs), chronic venous leg ulcers (VLUs), and pressure ulcers (PUs). Experimental data shows that PMM is biocompatible and able to insert itself into damaged membranes, salvaging their barrier function and aiding cell survival. Moreover, the six case studies presented in this paper reveal the potential of this treatment strategy.

Effect of ambient temperature and intracellular pigmentation on photothermal damage rate kinetics

Computational models predicting cell damage responses to transient temperature rises generated by exposure to lasers have implemented the damage integral (Ω), which time integrates the chemical reaction rate constant described by Arrhenius. However, few published reports of empirical temperature histories (thermal profiles) correlated with damage outcomes at the cellular level are available to validate the breadth of applicability of the damage integral. In our study, an analysis of photothermal damage rate processes in cultured retinal pigment epithelium cells indicated good agreement between temperature rise, exposure duration (τ), and threshold cellular damage. Full-frame thermograms recorded at high magnification during laser exposures were overlaid with fluorescence damage images taken 1 h postexposure. From the image overlays, pixels of the thermogram correlated with the boundary of cell death were used to extract threshold thermal profiles. Assessing photothermal responses at these boundaries standardized all data points, irrespective of laser irradiance, damage size, or optical and thermal properties of the cells. These results support the hypothesis that data from boundaries of cell death were equivalent to a minimum visible lesion, where the damage integral approached unity (Ω  =  1) at the end of the exposure duration. Empirically resolved Arrhenius coefficients for use in the damage integral determined from exposures at wavelengths of 2  μm and 532 nm and durations of 0.05-20 s were consistent with literature values. Varying ambient temperature (Tamb) between 20°C and 40°C during laser exposure did not change the τ-dependent threshold peak temperature (Tp). We also show that, although threshold laser irradiance varied due to pigmentation differences, threshold temperatures were irradiance independent.

Efficacy and Safety of Wet Wipes Containing Hy-Ter® Solution Compared with Standard Care for Bilateral Posterior Blepharitis: A Preliminary Randomized Controlled Study

INTRODUCTION

A novel treatment for posterior blepharitis which involves the use of disposable wet wipes imbibed with a solution of terpinen-4-ol and hyaluronic acid (Hy-Ter^®) as well as aloe, natural anti-inflammatories and antiseptics (Blephapad Combo; Novelty Technology Care, Milan, Italy) has been proposed. The aim of this study was to compare the efficacy and safety of treatment with Blephapad Combo with standard treatment.

METHODS

We conducted 4-week, open-label, randomized controlled study with a closed sequential design at the Magna Graecia University of Catanzaro, Italy in which patients aged > 40 years with symmetrical bilateral posterior blepharitis were enrolled. Each eye represented a single experimental unit. Patients were randomly assigned using a computer-generated randomization list to apply a reusable heated compress to the eyelid of one eye before cleansing the eyelid with the Blephapad Combo wet wipe (Blephapad Combo treatment arm) or to use the standard treatment of applying a wet and warm gauze to the other eye (standard treatment arm), twice daily for 4 weeks. The primary endpoint was the percentage change from baseline to week 4 in meibomian gland dysfunction (MGD) grading scale scores.

RESULTS

Eighteen patients (9 men; 9 women) with a mean (± standard deviation) age of 66.9 ± 9.03 years were included in the study. Compared with the eye receiving the standard treatment, treatment with Blephapad Combo appeared to improve the MGD total score after 4 weeks of treatment (mean change from baseline - 29.9 vs. - 38.5%). The assessment of the investigators was that in 11 patients the eye treated with Blephapad Combo showed greater benefit, in two patients the eye treated with the standard treatment showed greater benefit and in four patients there was no difference between treatments. Blephapad Combo was well tolerated, with no serious adverse events (AEs) reported. Minor ocular AEs were reported in 44.4 and 38.9% of patients in the Blephard Combo and standard treatment arms, respectively.

CONCLUSIONS

Treatment with Blephapad Combo was more effective than the standard treatment in ameliorating MGD in patients with posterior blepharitis. Minor ocular AEs events were equally distributed between the two treatments arms.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT03301844.

A novel system, TearCare®, for the treatment of the signs and symptoms of dry eye disease

PURPOSE

The objective of this study was to evaluate the safety and effectiveness of the TearCare® System in adult patients with clinically significant dry eye disease (DED).

PATIENTS AND METHODS

This was a prospective, single-center, randomized, parallel-group, clinical trial. Subjects with DED were randomized to either a single TearCare treatment conducted at the clinic or 4 weeks of daily warm compress (WC) therapy. The TearCare procedure consisted of 12 minutes of thermal eyelid treatment immediately followed by manual expression of the meibomian glands. WC therapy consisted of once daily application of the compresses to the eyelids for 5 minutes. Subjects were followed until 6 months post-treatment. The primary effectiveness end point was defined as change from baseline to 4 weeks for tear breakup time (TBUT). Secondary effectiveness end points included meibomian gland assessment, corneal and conjunctival staining scores, and assessment of dry eye symptoms using validated questionnaires. Safety was evaluated by collecting device-related adverse events, intraocular pressure, and best spectacle-corrected Snellen Visual acuity.

RESULTS

Twenty-four subjects were enrolled and all subjects completed 6 months follow-up. At the 1-month follow-up, TearCare subjects demonstrated an improvement from baseline in mean (±SD) TBUT of 11.7±2.6 seconds compared with an average worsening of -0.3±1.1 seconds for subjects in the WC group (p<0.0001). Significantly greater improvements in the change from baseline in meibomian gland scores, as well as corneal and conjunctival staining scores, were observed in the TearCare group. Subjects in the TearCare group also showed significantly greater improvement in dry eye symptoms as measured by the 3 questionnaires. Both treatments were well-tolerated.

CONCLUSION

The findings of this pilot study suggest that the TearCare System is an effective treatment option for patients with DED, with the effects on the signs and symptoms of DED persisting for at least 6 months.

A review of the evidence for threshold of burn injury

INTRODUCTION

Burn injury is common and depth is one measure of severity. Although the depth of burn injury is determined by many factors, the relationship between the temperature of the injurious agent and exposure duration, known as the time-temperature relationship, is widely accepted as one of the cornerstones of burn research. Moritz and Henriques first proposed this relationship in 1947 and their seminal work has been cited extensively. However, over the years, readers have misinterpreted their findings and incorporated misleading information about the time-temperature relationship into a wide range of industrial standards, burn prevention literature and medicolegal opinion.

AIM

The purpose of this paper is to present a critical review of the evidence that relates temperature and time to cell death and the depth of burn injury. These concepts are used by researchers, burn prevention strategists, burn care teams and child protection professionals involved in ascertaining how the mechanism of burning relates to the injury pattern and whether the injury is consistent with the history.

REVIEW METHODS

This review explores the robustness of the currently available evidence. The paper summarises the research from burn damage experimental work as well as bioheat transfer models and discusses the merits and limitations of these approaches.

REVIEW FINDINGS

There is broad agreement between in vitro and in vivo studies for superficial burns. There is clear evidence that the perception of pain in adult human skin occurs just above 43°C. When the basal layer of the epidermis reaches 44°C, burn injury occurs. For superficial dermal burns, the rate of tissue damage increases logarithmically with a linear increase in temperature. Beyond 70°C, rate of damage is so rapid that interpretation can be difficult. Depth of injury is also influenced by skin thickness, blood flow and cooling after injury. There is less clinical evidence for a time-temperature relationship for deep or subdermal burns. Bioheat transfer models are useful in research and becoming increasingly sophisticated but currently have limited practical use. Time-temperature relationships have not been established for burns in children's skin, although standards for domestic hot water suggest that the maximum temperature should be revised downward by 3-4°C to provide adequate burn protection for children.

CONCLUSION

Time-temperature relationships established for pain and superficial dermal burns in adult human skin have an extensive experimental modeling basis and reasonable clinical validation. However, time-temperature relationships for subdermal burns, full thickness burns and burn injury in children have limited clinical validation, being extrapolated from other data, and should be used with caution, particularly if presented during expert evidence.

The Limitation of Applying Heat to the External Lid Surface: A Case of Recalcitrant Meibomian Gland Dysfunction

The effects on the inner surface temperatures of the upper and lower eyelids of four commercial heat therapies were compared for an individual with recalcitrant meibomian gland dysfunction. Three therapies (Bruder mask, Blephasteam, and MiBoFlo) involved the application of heat to the external lid surface, and the fourth (LipiFlow) applied heat to the internal lid surface. Only LipiFlow was effective in elevating the inner surface temperatures to the reported 40°C therapeutic threshold for melting obstructed meibum.

Contribution of mitochondria to injury of hepatocytes and liver tissue by hyperthermia

OBJECTIVE

The aim of this study was to investigate functional changes of liver mitochondria within the experimentally modeled transition zone of radiofrequency ablation and to estimate possible contribution of these changes to the energy status of liver cells and the whole tissue.

MATERIALS AND METHODS

Experiments were carried out on mitochondria isolated from the perfused liver and isolated hepatocytes of male Wistar rats. Hyperthermia was induced by changing the temperature of perfusion medium in the range characteristic for the transition zone (38-52°C). After 15-min perfusion, mitochondria were isolated to investigate changes in the respiration rates and the membrane potential. Adenine nucleotides extracted from isolated hepatocytes and perfused liver subjected to hyperthermic treatment were analyzed by HPLC.

RESULTS

Hyperthermic liver perfusion at 42-52°C progressively impaired oxidative phosphorylation in isolated mitochondria. Significant inhibition of the respiratory chain components was observed after perfusion at 42°C, irreversible uncoupling became evident after liver perfusion at higher temperatures (46°C and above). After perfusion at 50-52°C energy supplying function of mitochondria was entirely compromised, and mitochondria turned to energy consumers. Hyperthermia-induced changes in mitochondrial function correlated well with changes in the energy status and viability of isolated hepatocytes, but not with the changes in the energy status of the whole liver tissue.

CONCLUSIONS

In this study the pattern of the adverse changes in mitochondrial functions that are progressing with increase in liver perfusion temperature was established. Results of experiments on isolated mitochondria and isolated hepatocytes indicate that hyperthermic treatment significantly and irreversibly inhibits energy-supplying function of mitochondria under conditions similar to those existing in the radiofrequency ablation transition zone and these changes can lead to death of hepatocytes. However, it was not possible to estimate contribution of mitochondrial injury to liver tissue energy status by estimating only hyperthermia-induced changes in adenine nucleotide amounts on the whole tissue level.

The Pentablock Amphiphilic Copolymer T1107 Prevents Aggregation of Denatured and Reduced Lysozyme

Aggregation of denatured or unfolded proteins establishes a large energy barrier to spontaneous recovery of protein form and function following traumatic injury, tissue cryopreservation, and biopharmaceutical storage. Some tissues utilize small heat shock proteins (sHSPs) to prevent irreversible aggregation, which allows more complex processes to refold or remove the unfolded proteins. It is postulated that large, amphiphilic, and biocompatible block copolymers can mimic sHSP function. Reduced and denatured hen egg white lysozyme (HEWL) is used as a model aggregating protein. The poloxamine T1107 prevents aggregation of HEWL at 37 °C by three complimentary measures. Structural analysis of denatured HEWL reveals a partially folded conformation with preserved or promoted beta-sheet structures only in the presence of T1107. The physical association of T1107 with denatured HEWL, and the ability to prevent aggregation, is linked to the critical micelle temperature of the polymer. The results suggest that T1107, or a similar amphiphilic block copolymer, can find use as a synthetic chaperone to augment the innate molecular repair mechanisms of natural cells.

All Warm Compresses Are Not Equally Efficacious

PURPOSE

To investigate which warm compress (WC) methods used in a small case series are the most effective in providing heat to the inner eyelids for the supplemental treatment of meibomian gland dysfunction.

METHODS

Inclusion criteria included the following: 18 years or older and willingness to participate in the study, no current ocular inflammation/disease, and no ocular surgery within the last 6 months. Five patients were fully consented and enrolled. Various forms of contact and noncontact WC heating methods (dry, wet/moist, and chemically activated dry heat) were tested. A paired contralateral design was used; each subject had a heated test eye and an unheated control eye. For both test and control eyes, the temperature of the external upper, external lower, and internal lower lids was measured at baseline and every 2 minutes for 10 minutes during application. Each participant underwent each of the eight treatments under study. Microwaved compresses were heated to 47 ± 1.0°C; two compresses were self-heating and thus not under investigator control.

RESULTS

The mean (± SD) age of the patients was 42.2 (± 20.3) years. Out of the eight methods tested, the bundled wet/moist towel method was the only compress that elevated the temperature of all three lid surfaces (external upper, external lower, and internal lower lids) to 40°C or higher. The chemically activated EyeGiene, MGDRx EyeBag, and MediBeads compresses resulted in the lowest temperature increase at the inner palpebral surface.

CONCLUSIONS

The Bundle method, although the most labor intensive, increased lid temperatures above therapeutic levels, as reported in the literature, for all measured sections during the WC application. As such, this method of WC application can be recommended for supplemental at-home therapy for meibomian gland dysfunction and any condition requiring that therapeutic heat of 40°C be administered to the meibomian glands.

Temperature profiles of patient-applied eyelid warming therapies

PURPOSE

To compare temperature profile characteristics (on and off eye) of two patient-applied heat therapies for meibomian gland dysfunction (MGD): an eye mask containing disposable warming units (EyeGiene(®)) and a microwave-heated flaxseed eye bag(®) (MGDRx EyeBag(®)).

METHODS

In vitro evaluation: surface temperature profiles of activated eye masks and heated eye bags(®) (both n=10), were tracked every 10s until return to ambient temperature. Heat-transfer assessment: outer and inner eyelid temperature profiles throughout the eye mask and eye bag(®) treatment application period (10min) were investigated in triplicate. The devices were applied for 12 different time intervals in a randomised order, with a cool-down period in between to ensure ocular temperatures returned to baseline. Temperature measurements were taken before and immediately after each application.

RESULTS

In vitro evaluation: on profile, the eye bag(®) surface temperature peaked earlier (0±0 s vs. 100±20 s, p<0.001), cooled more slowly and displayed less variability than the eye mask (all p<0.05). Heat-transfer assessment: the eye bag(®) effected higher peak inner eyelid temperatures (38.1±0.4°C vs. 37.4±0.2°C, p=0.04), as well as larger inner eyelid temperature increases over the first 2 min, and between 9 and 10 min (all p<0.05).

CONCLUSIONS

The eye bag(®) surface temperature profile displayed greater uniformity and slower cooling than the eye mask, and was demonstrated to be significantly more effective in raising ocular temperatures than the eye mask, both statistically and clinically. This has implications for MGD treatment, where the melting points of meibomian secretions are likely to be higher with increasing disease severity.

Non-lethal heat treatment of cells results in reduction of tumor initiation and metastatic potential

Non-lethal hyperthermia is used clinically as adjuvant treatment to radiation, with mixed results. Denaturation of protein during hyperthermia treatment is expected to synergize with radiation damage to cause cell cycle arrest and apoptosis. Alternatively, hyperthermia is known to cause tissue level changes in blood flow, increasing the oxygenation and radiosensitivity of often hypoxic tumors. In this study, we elucidate a third possibility, that hyperthermia alters cellular adhesion and mechanotransduction, with particular impact on the cancer stem cell population. We demonstrate that cell heating results in a robust but temporary loss of cancer cell aggressiveness and metastatic potential in mouse models. In vitro, this heating results in a temporary loss in cell mobility, adhesion, and proliferation. Our hypothesis is that the loss of cellular adhesion results in suppression of cancer stem cells and loss of tumor virulence and metastatic potential. Our study suggests that the metastatic potential of cancer is particularly reduced by the effects of heat on cellular adhesion and mechanotransduction. If true, this could help explain both the successes and failures of clinical hyperthermia, and suggest ways to target treatments to those who would most benefit.

Enhancing laser therapy using PEGylated gold nanoparticles combined with ultrasound and microbubbles

BACKGROUND

Gold nanorod (AuNR) laser therapy (LT) is a non-invasive method of increasing the temperature of a target tissue using near infrared light. In this study, the effects of ultrasound and microbubbles (USMB) with AuNR and LT were investigated on cell viability.

METHODS

MDA-MB-231 cells in suspension were treated with three different treatment combinations of AuNR, LT and USMB (Pneg=0.6 or 1.0 MPa): (1) AuNR with USMB followed by LT, (2) AuNR and LT followed by USMB, and (3) USMB followed by AuNR and LT. Cells were also exposed to USMB and LT without AuNR. The USMB conditions were: 500 kHz frequency, 16 cycles, 1kHz pulse repetition frequency for 1 min in the presence of Definity microbubbles (1.7% v/v). AuNR and LT conditions were: mPEG coated AuNR at 3×10(11) np/mL and 1.9 W/cm(2) for 3 min. Following the treatment, cell viability was assessed using propidium iodide (PI) fluorescent marker and flow cytometry (VPI), and colony assay (VCA). Cell viabilities were compared using a non-parametric Mann-Whitney U-test and synergism was assessed using the Bliss Independence Model.

RESULTS AND DISCUSSION

USMB improved cell death when combined with AuNR and LT. VPI of 17±2% (at 0.6 MPa) and 11±4% (at 1.0 MPa) were observed with combined treatment of AuNR and USMB followed by LT compared to VPI of 60±2% (at 0.6 MPa) and 42±3% (at 1.0 MPa) with USMB alone and VPI of 22±3% for AuNR and LT. The combined effect of AuNR and LT with USMB was additive regardless of treatment order. VCA results agreed with the additive effect caused by combining AuNR and LT with USMB for all treatment orders. In the absence of AuNR, samples exposed to LT prior to USMB at 0.6 MPa increased VPI by 13% (p<0.01) showing a protective effect.

CONCLUSION

Combining AuNR and LT with USMB resulted in an additive effect on cell viability compared to AuNR and LT, or USMB. In addition, cells exposed to low intensity NIR light appear to be protected against USMB exposure.

Hyperthermia differently affects connexin43 expression and gap junction permeability in skeletal myoblasts and HeLa cells

Stress kinases can be activated by hyperthermia and modify the expression level and properties of membranous and intercellular channels. We examined the role of c-Jun NH2-terminal kinase (JNK) in hyperthermia-induced changes of connexin43 (Cx43) expression and permeability of Cx43 gap junctions (GJs) in the rabbit skeletal myoblasts (SkMs) and Cx43-EGFP transfected HeLa cells. Hyperthermia (42°C for 6 h) enhanced the activity of JNK and its target, the transcription factor c-Jun, in both SkMs and HeLa cells. In SkMs, hyperthermia caused a 3.2-fold increase in the total Cx43 protein level and enhanced the efficacy of GJ intercellular communication (GJIC). In striking contrast, hyperthermia reduced the total amount of Cx43 protein, the number of Cx43 channels in GJ plaques, the density of hemichannels in the cell membranes, and the efficiency of GJIC in HeLa cells. Both in SkMs and HeLa cells, these changes could be prevented by XG-102, a JNK inhibitor. In HeLa cells, the changes in Cx43 expression and GJIC under hyperthermic conditions were accompanied by JNK-dependent disorganization of actin cytoskeleton stress fibers while in SkMs, the actin cytoskeleton remained intact. These findings provide an attractive model to identify the regulatory players within signalosomes, which determine the cell-dependent outcomes of hyperthermia.

Effect of a commercially available warm compress on eyelid temperature and tear film in healthy eyes

PURPOSE

To evaluate eyelid temperature change and short-term effects on tear film stability and lipid layer thickness in healthy patients using a commercially available warm compress (MGDRx EyeBag) for ophthalmic use.

METHODS

Eyelid temperature, noninvasive tear film breakup time (NITBUT), and tear film lipid layer thickness (TFLLT) of 22 healthy subjects were measured at baseline, immediately after, and 10 minutes after application of a heated eyebag for 5 minutes to one eye selected at random. A nonheated eyebag was applied to the contralateral eye as a control.

RESULTS

Eyelid temperatures, NITBUT, and TFLLT increased significantly from baseline in test eyes immediately after removal of the heated eyebag compared with those in control eyes (maximum temperature change, 2.3 ± 1.2 °C vs. 0.3 ± 0.5 °C, F = 20.533, p < 0.001; NITBUT change, 4.0 ± 2.3 seconds vs. 0.4 ± 1.7 seconds, p < 0.001; TFLLT change, 2.0 ± 0.9 grades vs. 0.1 ± 0.4 grades, Z = -4.035, p < 0.001). After 10 minutes, measurements remained significantly higher than those in controls (maximum temperature change, 1.0 ± 0.7 °C vs. 0.1 ± 0.3 °C, F = 14.247, p < 0.001; NITBUT change, 3.6 ± 2.1 seconds vs. 0.1 ± 1.9 seconds, p < 0.001; TFLLT change, 1.5 ± 0.9 vs. 0.2 ± 0.5 grades, Z = -3.835, p < 0.001). No adverse events occurred during the study.

CONCLUSIONS

The MGDRx EyeBag is a simple device for heating the eyelids, resulting in increased NITBUT and TFLLT in subjects without meibomian gland dysfunction that seem to be clinically significant. Future studies are required to determine clinical efficacy and evaluate safety after long-term therapy in meibomian gland dysfunction patients.

Case report: a successful LipiFlow treatment of a single case of meibomian gland dysfunction and dropout

OBJECTIVE

The aim of this study was to investigate whether a single case of meibomian gland dysfunction (MGD), with significant MG dropout resulting in evaporative dry eye, could be effectively treated with the LipiFlow (a new Food and Drug Administration-approved thermodynamic pulsatile treatment).

MATERIALS AND METHODS

A 39-year-old white woman experienced severe dry eye symptoms because of MGD with considerable MG dropout resulting in evaporative dry eye. Standardized diagnostic MG expression and meibography led to the tentative diagnosis of nonobvious MGD (only 1 functional MG on each lower lid) and MG dropout (∼50% of the lower lid MGs were missing with the remaining MGs being severely truncated). The patient underwent a single 12-min LipiFlow treatment per eye and returned for follow-up at 1 and 7 months posttreatment.

RESULTS

The LipiFlow treatment increased the number of functional lower lid MGs from 1 to 5 glands OD and 1 to 7 glands OS at 1 month with slight regression at 7 months (4 OD and 4 OS); increased fluorescein break-up time from 4 to 7 sec OD and 4 to 9 sec OS at both 1 and 7 months; and decreased symptom scores by approximately 50% at 1 month and approximately 75% at 7 months.

CONCLUSIONS

These results demonstrate the effectiveness of the LipiFlow in restoring MG function and improving ocular comfort even in this particular case of significant MG dropout and MG truncation.

QUANTIFICATION AND THE UNDERLYING MECHANISM OF SKIN THERMAL DAMAGE: A REVIEW

Skin thermal damage is the most common thermal trauma in civilian and military communities. Besides, advances in laser, microwave, and similar technologies have led to recent developments of thermal treatments for diseases involving skin tissue aiming at inducing damage precisely within targeted tissue structures without affecting the surrounding healthy tissue. Pain sensation accompanying thermal damage is also a serious problem for burn patients. Therefore, it is of great importance to quantify the thermal damage in skin tissue. In this review, we detail the progress of the state-of-the-art mathematical models and experimental methods for the quantification of thermal damage (both heat damage and cold damage) and the general development of thermal treatments in tissue engineering. This could enable better understanding of the underlying mechanisms of skin thermal damage and the optimization of clinical thermal therapies.

Antigen retrieval causes protein unfolding: evidence for a linear epitope model of recovered immunoreactivity

Antigen retrieval (AR), in which formalin-fixed paraffin-embedded tissue sections are briefly heated in buffers at high temperature, often greatly improves immunohistochemical staining. An important unresolved question regarding AR is how formalin treatment affects the conformation of protein epitopes and how heating unmasks these epitopes for subsequent antibody binding. The objective of the current study was to use model proteins to determine the effect of formalin treatment on protein conformation and thermal stability in relation to the mechanism of AR. Sodium dodecyl sulfate polyacrylamide gel electrophoresis was used to identify the presence of protein formaldehyde cross-links, and circular dichroism spectropolarimetry was used to determine the effect of formalin treatment and high-temperature incubation on the secondary and tertiary structure of the model proteins. Results revealed that for some proteins, formalin treatment left the native protein conformation unaltered, whereas for others, formalin denatured tertiary structure, yielding a molten globule protein. In either case, heating to temperatures used in AR methods led to irreversible protein unfolding, which supports a linear epitope model of recovered protein immunoreactivity. Consequently, the core mechanism of AR likely centers on the restoration of normal protein chemical composition coupled with improved accessibility to linear epitopes through protein unfolding.

A novel thermodynamic treatment for meibomian gland dysfunction

PURPOSE

To evaluate a novel thermodynamic treatment for obstructive meibomian gland dysfunction (MGD).

MATERIALS AND METHODS

Fourteen adult subjects (10 females, 4 males, mean age = 54.2 ± 9.6 yr) were recruited in a multi-center, feasibility clinical trial in Durham and Cary, North Carolina and Boston, Massachusetts. Inclusion criteria included: previous diagnosis of moderate to severe dry eye; dry eye symptoms for at least three months prior; daily topical lubricant use; and evidence of meibomian gland (MG) obstruction in the central five glands of both eyes lower eyelids. Exclusion criteria included: history of recent acute or chronic ocular inflammation or infection and lid surface abnormalities affecting lid function. The treatment: the device heats the palpebral surface of upper and lower eyelids while simultaneously applying graded pulsatile pressure to the outer eyelid for 12 min, thereby expressing the MGs during heating. One eye was randomly selected to undergo additional manual heated expression with another treatment device.

RESULTS

The mean MG secretion score, tear break-up time, corneal staining score, number of MGs yielding liquid secretion and symptom scores all improved significantly from baseline to 1 week. This was maintained through the 3-month follow-up. There was no statistically significant difference in any outcome between the automated device treatment only and the additional heated manual expression.

CONCLUSION

The combination of heat applied to the palpebral surface, while simultaneously expressing MGs during a single 12-minute treatment, was effective, in this feasibility study, in treating obstructive MG dysfunction and dry eye signs and symptoms for the 3-month study period.

Nonobvious obstructive meibomian gland dysfunction

This review presents the rationale and supporting data for a recent paradigm shift in our understanding of meibomian gland dysfunction (MGD). The historical understanding of MGD has been that of an infectious hypersecretory disorder with obvious signs of inflammation, hypersecretion, and purulent excreta. The current understanding of MGD now includes the polar concept of a less obvious or nonobvious type of hyposecretory obstructive MGD, where inflammation and other signs of pathology may be absent unless special examination techniques are employed. A new term, nonobvious obstructive MGD (NOMGD), is used to describe what may be the most common form of obstructive MGD. Obstructive MGD is an area of growing importance because obstructive MGD is now recognized to be the most common cause of evaporative dry eye, and because NOMGD seems to be the precursor to obvious obstructive MGD, it is also an important area to understand. The prevalence of NOMGD seems to be very high but currently significantly underdiagnosed. This review presents the relevant anatomy and physiology, concepts of obstructive MGD, the usual absence of inflammation in obstructive MGD, nomenclature and classification of obstructive and NOMGD, clinical diagnosis of NOMGD emphasizing the necessity for diagnostic expression, the use of a new instrument for diagnostic expression providing a standardized method of assessing meibomian gland functionality, the complementary roles of the aqueous and lipid layers, and the specific treatment of NOMGD, emphasizing that the success of treatment of all forms of obstructive MGD is dependent on the relief of the obstruction.

Quantitative assessments of burn degree by high-frequency ultrasonic backscattering and statistical model

An accurate and quantitative modality to assess the burn degree is crucial for determining further treatments to be properly applied to burn injury patients. Ultrasounds with frequencies higher than 20 MHz have been applied to dermatological diagnosis due to its high resolution and noninvasive capability. Yet, it is still lacking a substantial means to sensitively correlate the burn degree and ultrasonic measurements quantitatively. Thus, a 50 MHz ultrasound system was developed and implemented to measure ultrasonic signals backscattered from the burned skin tissues. Various burn degrees were achieved by placing a 100 °C brass plate onto the dorsal skins of anesthetized rats for various durations ranged from 5 to 20 s. The burn degrees were correlated with ultrasonic parameters, including integrated backscatter (IB) and Nakagami parameter (m) calculated from ultrasonic signals acquired from the burned tissues of a 5 × 1.4 mm (width × depth) area. Results demonstrated that both IB and m decreased exponentially with the increase of burn degree. Specifically, an IB of -79.0 ± 2.4 (mean ± standard deviation) dB for normal skin tissues tended to decrease to -94.0 ± 1.3 dB for those burned for 20 s, while the corresponding Nakagami parameters tended to decrease from 0.76 ± 0.08 to 0.45 ± 0.04. The variation of both IB and m was partially associated with the change of properties of collagen fibers from the burned tissues verified by samples of tissue histological sections. Particularly, the m parameter may be more sensitive to differentiate burned skin due to the fact that it has a greater rate of change with respect to different burn durations. These ultrasonic parameters in conjunction with high-frequency B-mode and Nakagami images could have the potential to assess the burn degree quantitatively.

Reduced heat shock protein 70 in airway smooth muscle in patients with chronic obstructive pulmonary disease

Studies demonstrated that pathophysiological abnormalities of airway smooth muscle (ASM) contribute significantly to chronic obstructive pulmonary disease (COPD) pathogenesis, the aim of this study is to investigate heat shock protein 70 (Hsp70) in ASM in COPD. ASM from 8 COPD patients and 6 controls were isolated for detection of Hsp70 using Western blot. Male adult Wister rats were exposed to mixture of cigarette smoke/air or room air for an indicated period. The lung tissues were obtained for pathological analysis, and ASM were dissected for Hsp70 detection. Normalized Hsp70 in ASM from COPD patients was significantly lower than that from controls (P <.001), and it was a significant positive correlation of Hsp70 and lung function. One-month exposure of rats to cigarette smoke/air mixture led to increased expression of Hsp70 and heat shock transcription factor (Hsf1) in ASM as compared to controls, whereas 3-month exposure caused dramatically reduced Hsp70 and Hsf1 than control animals. In addition, 3-month exposure to cigarette smoke/air mixture resulted in significantly lower Hsp70 and Hsf1 in rats ASM than 1-month exposure (P <.001), and it was a positive correlation of Hsf1 and Hsp70. Long-term cigarette smoking results in reduced expression of Hsp70 in ASM. This finding provides additional insight in understanding molecular changes in ASM during COPD pathogenesis.

Acute temperature resistance threshold in heart mitochondria: Febrile temperature activates function but exceeding it collapses the membrane barrier

PURPOSE

Molecular mechanisms underlying hyperthermia-induced cellular injury are not fully understood. The aim of this study was to identify the components of mitochondrial oxidative phosphorylation affected by mild hyperthermia and to quantify the contribution of each component to changes in system behaviour.

METHODS

Temperature effects on the oxidative phosphorylation in isolated rat-heart mitochondria were assessed using modular kinetic analysis. Mitochondrial H(2)O(2) production and lipid peroxidation were measured for estimation of temperature-induced oxidative damage.

RESULTS

The increase of temperature in the febrile range (40 degrees C) slightly activated mitochondrial function through stimulation of the respiratory module, without affecting the kinetics of the proton leak and phosphorylation modules. At 42 degrees C, state 3 respiration rate remained unchanged, the proton leak across the inner mitochondrial membrane was substantially increased, the respiratory module slightly inhibited, leading to decreased membrane potential (Deltapsi) and diminished ATP synthesis (16% lower phosphorylation flux). Increase of temperature above 42 degrees C caused dissipation of Deltapsi and abolishment of ATP synthesis indicating complete uncoupling of oxidative phosphorylation. The changes in mitochondrial functions induced by incubation at 42 degrees C were completely reversible in contrast to only partial recovery after incubation at higher temperature (45 degrees C). Furthermore, hyperthermia stimulated the production of H(2)O(2) and membrane lipid peroxidation with maximal rates observed at 40 degrees C.

CONCLUSIONS

We demonstrated for the first time that febrile temperature (40 degrees C) activates mitochondrial energy supplying functions, whereas further temperature increase by only a few degrees leads to severe impairment of mitochondrial ability to maintain DeltaPsi and synthesise ATP.

Supraphysiological thermal injury in different human bladder carcinoma cell lines

Depending on the duration of exposure to supraphysiological temperatures, cellular proteins and organelles can suffer from structural alternations and irreversible denaturation, which may induce cell death. The thermotolerance of three human urinary bladder carcinoma cell lines, TSGH-8301, J82 and TCC-SUP (cytological grade 2, 3 and 4, respectively), was investigated in the present study. A home-made heating stage was used to provide a constant temperature for different cell lines of bladder carcinoma. The experimental data showed that the TCC-SUP and TSGH-8301 cells exhibited the lowest and highest thermotolerances, respectively, while J82 cells were intermediate. Moreover, the differences in the thermotolerances for the TSGH-8301 and J82 cells are significant when the supraphysiological temperature is higher than 43 degrees C. As for TSGH-8301 and TCC-SUP cells, the thermotolerances are significantly different for all of the thermal treatments tested. Furthermore, the thermotolerances of J82 and TCC-SUP are significantly different when the cells are exposed to a temperature less than 50 degrees C for longer than 2 min. Overall, the results suggest that the high cytological grade of the cell line of bladder cancer exhibits a low thermotolerance. The kinematic parameters of the activation energy and frequency factor for bladder cancer cell lines with different cytological grades were also quantitatively evaluated in this work.

Quinacrine protects neuronal cells against heat-induced injury

The effects of quinacrine (QA) on heat-induced neuronal injury have been explored, with the intention of understanding the mechanisms of QA protection. Primary cultivated striatum neurons from newborn rats were treated with QA 1h before heat treatment at 43 degrees C which lasted for another 1h, and necrosis and apoptosis were detected by Annexin-V-FITC and propidium iodide (PI) double staining. Neuronal apoptosis was determined using terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick end labeling (TUNEL) techniques. Cell membrane fluidity, activity of cytosolic phospholipase A(2) (cPLA(2)) and the level of arachidonic acid (AA) were also examined. Membrane surface ultrastructure of striatum neurons was investigated by atomic force microscopy (AFM). Results showed that heat treatment induced great striatum neurons death, with many dying neurons undergoing necrosis rather than apoptosis. QA alone had little effect on the survival of striatum neurons, while QA pretreatment before heat treatment decreased necrosis. Heat treatment also resulted in decreased membrane fluidity and increased cPLA(2) activity as well as arachidonic acid level; these effects were reversed by QA pretreatment. QA pretreatment also significantly prevented damage to the membrane surface ultrastructure of heat-treated neurons. These results suggest that QA protects striatum neurons against heat-induced neuronal necrosis, and also demonstrate that inhibition of cPLA(2) activity and stabilization of membranes may contribute to protective effect of quinacrine.

Treatment of burn injury by cellular repair

Burn injury leads to a direct damaging effect on cells, disrupting the assembly of the cell and denaturing proteins. Although modern medicine has significantly improved the survival of burn victims, a method to treat injury at the cellular level is presented. In particular, the cell membrane is most vulnerable to heat injury. Copolymer surfactants have been shown to repair the cell membrane, and agents such as poloxamer 188 have demonstrated this effect in numerous studies. Furthermore, copolymer surfactants have been shown to act as molecular chaperones, allowing denatured proteins to regain their native confirmation. Pharmaceutical agents may be developed to repair the cell membrane and refold proteins, mimicking endogenous repair mechanisms and salvaging cells that would otherwise be lost.