Effects of a new advanced glycation inhibitor, LR-90, on mitigating arterial stiffening and improving arterial elasticity and compliance in a diabetic rat model: aortic impedance analysis

BACKGROUND AND PURPOSE

We determined the effects of treatment with LR-90, an inhibitor of advanced glycation end products, on the mechanical properties of the arterial system in streptozotocin (STZ)-induced diabetic Sprague Dawley rats, using aortic impedance analysis, and further investigated the effects of LR-90 on the progression of aortic pathology.

EXPERIMENTAL APPROACH

STZ-induced diabetic rats were treated with or without LR-90 (50 mg L(-1) in drinking water) for 8 weeks and compared with control groups. Arterial BP measurements, various metabolic parameters, aortic histopathology, collagen cross-linking, AGE accumulation, and RAGE protein expression in aortic tissue were determined. Pulsatile parameters were evaluated using a standard Fourier series expansion technique and impulse response function of the filtered aortic input impedance spectra.

KEY RESULTS

LR-90 reduced glycated haemoglobin and triglycerides levels, although it had no effect on the glycaemic status. LR-90 did not affect arterial BP, but prevented the diabetes-induced increase in peripheral resistance and variations in aortic distensibility, as it reduced aortic characteristic impedance by 21%. LR-90 also prevented the elevation in wave reflection factor, as indicated by a 22.5% reduction and an associated increase of 23.5% in wave transit time, suggesting it prevents the augmentation of the systolic load of the left ventricle. Moreover, LR-90 inhibited collagen cross-linking and the accumulation of AGE and RAGE in the vasculature of diabetic rats.

CONCLUSIONS AND IMPLICATIONS

Treatment with LR-90 may impart significant protection against diabetes-induced aortic stiffening and cardiac hypertrophy and provides an additional therapeutic option for treatment of AGE associated diabetic complications.

Ketamine sedation during the treatment of retinopathy of prematurity

AIMS

To report the use of ketamine sedation as an alternative anaesthetic method for babies undergoing treatment for retinopathy of prematurity (ROP).

METHODS

All babies who underwent treatment for ROP over a 2-year period were included in this study. The babies preoperative weight, medical condition, and ventilation status was recorded. Data were collected on their ventilation status pre-, intra-, and postprocedure. Any change in their cardiac or respiratory status during or in the subsequent 3 days following the treatment was noted.

RESULTS

Eleven babies, 22 eyes, required treatment over this period. The procedure was well tolerated with only three babies having intraoperative complications, which all resolved spontaneously. Two babies had postoperative complications requiring additional ventilation. In no case was the procedure abandoned owing to anaesthetic complications.

CONCLUSIONS

The use of ketamine sedation allows the laser to be performed in a ward setting and avoids the potential risk of general anaesthesia and inter- and intra-hospital transfer. It has been found to produce few intra- or postoperative complications for the infant, while providing satisfactory conditions for the treatment of ROP.

Retinopathy screening in children and adolescents with diabetes

Diabetic retinopathy is a complication of diabetes that affects the blood vessels of the retina. The majority of patients with diabetic retinopathy exhibit background retinopathy. In approximately 10% of patients, background retinopathy will progress to sight-threatening retinopathy. The aims of our study were to measure the prevalence of retinopathy among our population and to assess the optimal time of screening children and adolescents with type 1 diabetes.

A model for the fluid motion of vitreous humour of the human eye during saccadic movement

During saccadic motion the eyewall moves in a manner similar to a sinusoid or at least can be represented by a sine Fourier series. Motion of the vitreous is induced by the saccade and the vitreo-retinal interface is subjected to a time-dependent shear. This force may be a significant factor for retinal tearing in the neighbourhood of small retinal holes or tears. An analytical viscoelastic model and a numerical, Newtonian model of the motion of the vitreous are presented and compared. Under sinusoidal boundary motion the analytical model shows that a viscous wave propagates inward toward the axis of rotation and the characteristic length of this wave is a function of the Womersley number. The numerical solution indicates that the vitreous moves similarly to the analytical result with small secondary motion; however, this motion allows complete recirculation of the vitreous over large timescales. Excellent agreement is found between the analytical and numerical models. The time-dependent fluid shear is evaluated and from the analytical solution the maximum value of this is found to be proportional to R0 square root of v(omega)3, where R0 is the eye radius, v the modified complex viscosity and omega the sinusoidal frequency. This indicates that myopes have a larger shear force exerted on them by virtue of the larger eye size. Further work is directed toward a model which links the stress found in the sclera to that exerted on the vitreo-retinal interface by the vitreous fluid motion.

Time-dependent stress and displacement of the eye wall tissue of the human eye

Myopia or short sightedness, is the most important predisposing factor to retinal detachment. The relative risk of detachment rises with increasing myopia. The model characterizes that because the severity of myopia increases with the axial length (antero-posterior diameter) of the eyeball, the relative risk of retinal detachment rises with increasing eye size. We present a mathematical model of the time-dependent shear stress force that occurs in the thin eye wall shell supporting the vitreous humour inside the eye globe during the acceleration and deceleration phases of saccadic eye movement. Results show that the shear force increases as the thickness of the eye wall decreases. It is common for myopes to have thinner eye wall tissue than emmetropes. In addition, if account is taken of the increased force required to provide normal saccadic movement of myopic (larger) eyes, then the shear force is up to seven times greater than that experienced for emmetropes.

Fiber-optic confocal microscope: FOCON

A new design for a reflecting fiber-optic confocal microscope, FOCON, is presented in which the beam splitter of a conventional confocal microscope is replaced by a fiber-optic splitter, and the core of a single-mode fiber takes the place of both the source and detector pinholes. It is shown that FOCON has the same resolution characteristics as a conventional confocal microscope, and requires fewer optical components and only rough alignment. The microscope is robust and can be rapidly scanned in the x, y, and z directions through the simple movement of the end of an optical fiber.

Single-mode fibers used as confocal microscope pinholes

Conventional clear-aperture pinholes in confocal microscopes can be replaced by single-mode optical fibers, thereby reducing alignment and dust accumulation problems and providing greater flexibility for optical and electronic hardware placement.

Morphological observations on patients with presumed trichiasis

The clinical findings in 116 patients with a provisional diagnosis of trichiasis are presented. In 69% a small degree of entropion producing lash-globe contact was detected. The term lid border entropion is proposed for this condition, which is recognised clinically by conjunctivalisation of the meibomian gland orifices and anterior placement of the mucocutaneous junction. These features were clearly demonstrated by electron microscopy of a biopsy specimen from one patient. An analysis of other causes of trichiasis is discussed and an attempt is made to clarify the terminology currently in use.

The seat belt law and after

We report a retrospective study of 378 perforating eye injuries presenting between August 1981 and July 1984 to four major teaching hospitals. The aetiological groups have been analysed together and by region, and preventive measures for some groups are discussed. We have confirmed the effectiveness of seat belt legislation in reducing serious eye injury.