Dr. Denise H. Hawkins Evans Profile

Dr. Denise H. Hawkins Evans

at Univ of Johannesburg

SPIE Involvement:

Author

Publications (5)

Proceedings Article | 24 February 2009 Paper

The effect of 648 nm diode laser irradiation on second messengers in senescent human keratinocytes

D. Hawkins Evans, H. Abrahamse

Proceedings Volume 7165, 716509 (2009) https://doi.org/10.1117/12.809009

KEYWORDS: Laser irradiation, Acquisition tracking and pointing, Proteins, Cell death, Semiconductor lasers, Calcium, NOx, Luminescence, Laser therapeutics, Bioalcohols

Read Abstract +

Background/purpose: Stress induced premature senescence (SIPS) is defined as the long-term effect of subcytotoxic stress on proliferative cell types. Cells in SIPS display differences at the level of protein expression which affect energy metabolism, defense systems, redox potential, cell morphology and transduction pathways. This study aimed to determine the effect of laser irradiation on second messengers in senescent cells and to establish if that effect can be directly linked to changes in cellular function such as cell viability or proliferation. Materials and Methods: Human keratinocyte cell cultures were modified to induce premature senescence using repeated sub-lethal stresses of 200 uM H₂O₂ or 5% OH every day for four days with two days recovery. SIPS was confirmed by senescence-associated β-galactosidase staining. Control conditions included normal, repeated stress of 500 uM H₂O₂ to induce apoptosis and 200 uM PBN as an anti-oxidant or free radical scavenger. Cells were irradiated with 1.5 J/cm² on day 1 and 4 using a 648 nm diode laser (3.3 mW/cm²) and cellular responses were measured 1 h post irradiation. The affect on second messengers was assessed by measuring cAMP, cGMP, nitric oxide and intracellular calcium (Ca²⁺) while functional changes were assessed using cell morphology, ATP cell viability, LDH membrane integrity and WST-1 cell proliferation. Results: Results indicate an increase in NO and a decrease in cGMP and Ca²⁺ in 200 uM H2O2 irradiated cells while PBN irradiated cells showed a decrease in cAMP and an increase in ATP viability and cell proliferation. Conclusion: Laser irradiation influences cell signaling which ultimately changes the biological function of senescent cells. If laser therapy can stimulate the biological function of senescent cells it may be beneficial to conditions such as immune senescence, skin ageing, muscle atrophy, premature ageing of arteries in patients with advanced heart disease, neurodegenerative disorders and chronic renal failure.

Proceedings Article | 18 February 2009 Paper

DNA damage in wounded, hypoxic and acidotic human skin fibroblast cell cultures after low laser irradiation

D. Hawkins Evans, A. Mbene, I. Zungu, N. Houreld, H. Abrahamse

Proceedings Volume 7165, 71650E (2009) https://doi.org/10.1117/12.809093

KEYWORDS: Comets, Laser irradiation, Control systems, Skin, Phototherapy, Laser therapeutics, Oxygen, Wound healing, Visible radiation, In vitro testing

Read Abstract +

Phototherapy has become more popular and widely used in the treatment of a variety of medical conditions. To ensure sound results as evidence of its effectiveness, well designed experiments must be conducted when determining the effect of phototherapy. Cell culture models such as hypoxic, acidotic and wounded cell cultures simulating different disease conditions including ischemic heart disease, diabetes and wound healing were used to determine the effect of laser irradiation on the genetic integrity of the cell. Even though phototherapy has been found to be beneficial in a wide spectrum of conditions, it has been shown to induce DNA damage. However, this damage appears to be repairable. The risk lies in the fact that phototherapy may help the medical condition initially but damage DNA at the same time leaving undetected damage that may result in late onset, more severe, induced medical conditions including cancer. Human skin fibroblasts were cultured and used to induce a wound (by the central scratch model), hypoxic (by incubation in an anaerobic jar, 95% N₂ and 5% O₂) and acidotic (reducing the pH of the media to 6.7) conditions. Different models were irradiated using a Helium-Neon (632.8 nm) laser with a power density of 2.07 mW/cm2 and a fluence of 5 J/cm² or 16 J/cm². The effect of the irradiation was determined using the Comet assay 1 and 24 h after irradiation. In addition, the Comet assay was performed with the addition of formamidopyrimidine glycosylase (FPG) obviating strand brakes in oxidized bases at a high fluence of 16 J/cm². A significant increase in DNA damage was seen in all three injured models at both 1 and 24 h post-irradiation when compared to the normal un-injured cells. However, when compared to non-irradiated controls the acidotic model showed a significant decrease in DNA damage 24 h after irradiation indicating the possible induction of cellular DNA repair mechanisms. When wounded cells were irradiated with higher fluences of 16 J/cm², there was a significant increase in DNA damage in irradiated cells with and without the addition of FPG. These results are indicative of the importance of both cell injury model as well as fluence when assessing the effect of phototherapy on DNA integrity.

Proceedings Article | 13 July 2007 Paper

Efficacy of a single high dose versus multiple low doses of LLLT on wounded skin fibroblasts

Denise Hawkins, Heidi Abrahamse

Proceedings Volume 6632, 66321U (2007) https://doi.org/10.1117/12.725409

KEYWORDS: Aluminium phosphide, Acquisition tracking and pointing, Laser irradiation, Wound healing, In vitro testing, Cell death, Comets, Skin, Tissues, In vivo imaging

Read Abstract +

Proceedings Article | 28 February 2006 Paper

Effect of wavelength and fluence on morphology cellular and genetic integrity of diabetic wounded human skin fibroblasts

H. Abrahamse, D. Hawkins, N. Houreld

Proceedings Volume 6140, 614006 (2006) https://doi.org/10.1117/12.641172

KEYWORDS: Wound healing, Aluminium phosphide, Control systems, Tissues, Genetics, Acquisition tracking and pointing, Laser therapeutics, Laser irradiation, Skin, Comets

Read Abstract +

Proceedings Article | 30 August 2005 Paper

Influence of beam shape on in-vitro cellular transformations in human skin fibroblasts

Patience Mthunzi, Andrew Forbes, Denise Hawkins, Heidi Abrahamse, Aletta Karsten

Proceedings Volume 5876, 58760V (2005) https://doi.org/10.1117/12.614950

KEYWORDS: Beam shaping, Gaussian beams, Acquisition tracking and pointing, Wound healing, Laser therapeutics, Laser irradiation, Aluminium phosphide, In vitro testing, Seaborgium, Skin

Read Abstract +

View contact details

UPDATE YOUR PROFILE

Is this your profile? Update it now.

Sign into your SPIE.org account

Don’t have a profile and want one?

Create an account on SPIE.org

Keywords/Phrases

Search In:

Publication Years