AC/A ratios in myopic and emmetropic Hong Kong children and the effect of timolol§

Purpose: Caucasian children with myopia have elevated response accommodative vergence to accommodation (AC/A) ratios. The purpose of this study was twofold: to determine if response AC/A ratios vary with refractive error and with myopic progression rate in Hong Kong Chinese children, and to determine the effect of beta‐adrenergic antagonism with topical timolol application on AC/A ratios. Methods: Thirty children aged eight to 12 years participated in the study. All refractive errors were corrected with spectacle lenses. Accommodative responses were measured using a Shin‐Nippon autorefractor and concurrent changes in vergence were assessed using a vertical prism and a Howell‐Dwyer card at three metres and 0.33 metre. Accommodative demand was altered using plus or minus two dioptre lenses and lens‐ and distance‐induced response AC/A ratios were calculated. Measurements were repeated 30 minutes after the instillation of topical timolol maleate (0.5 per cent). Results: AC/A ratios appeared higher in progressing myopic children but the difference was not statistically significant. Timolol application reduced accommodative convergence (AC) in the stable myopes (reduction = ‐3 ± 1.14^A) but not in the emmetropes (0.69 ± 0.9^P) or progressing myopes (0.16 ± 0.43^A) and this difference between refractive groups was statistically s ignificant (F^2,27= 3.766; P= 0.036). However, timolol did not produce a significant change in the accommodative response to positive or negative lenses or response AC/A ratios. Conclusions: We did not find that AC/A ratios in myopic Chinese children were elevated and therefore, it is unlikely that elevated AC/A ratios are responsible for the high levels of myopia that occur in Hong Kong. The finding that timolol reduced AC in the stable myopes suggests that the autonomic control of accommodative convergence in these children may be different from that in emmetropic children and those with progressing myopia.     

Murine skin flap survival may not be affected by underlying fat viability.

One problem in the treatment of degloving injuries is the accurate prediction of the survivability of the avulsed tissue. Initial evaluation frequently underestimates the degree of eventual flap loss, and in many cases, there is a progressive necrosis that continues over the ensuing days. The pathophysiology of this phenomenon is unclear. We undertook this study to test the theory that underlying devascularised fat contributes to overlying skin necrosis. A dorsal random skin flap model was used in the rat. Sixty-six rats were divided into three groups: flaps with viable fat and silicone sheeting underneath, flaps with devascularised fat and silicone sheeting underneath and control flaps with only silicone sheeting underneath. Flap necrosis (% area+/-SEM) was evaluated at one week, and found to be 27.1+/-4% in the live fat group, 33.2+/-4% in the dead fat group and 33.6+/-5% in the control group. One-way analysis of variance showed no statistically significant difference between the three groups at a power of 80%. In this study, we have shown that neither live nor dead fat has a significant influence on the survival of an overlying random skin flap in the rat.     

Magnetically-labeled sensitized splenocytes to identify glioma by MRI: a preliminary study.

This study investigated the feasibility of imaging the migration and incorporation of magnetically-labeled sensitized splenocytes in an experimental 9L glioma brain tumor model. Splenocytes collected from tumor-bearing (sensitized splenocytes) or control (nonsensitized splenocytes) host rats were analyzed to determine the population of different cells, labeled with ferumoxides-protamine sulfate (FePro) and injected intravenously to recipient rats (N=4, for each group) bearing intracranial 9L tumors. Day 3 postinjection of splenocytes multiecho T2*-weighted and three-dimensional (3D) gradient echo MRI were obtained using a 7 Tesla MR system. R2* (1/T2*) maps were created from the T2*-weighted images. Signal intensities (SIs) and R2* values in the tumors and contralateral brain were determined by hand drawn regions of interest (ROIs). Brain sections were stained for the evidence of administered cells. Both 3D and T2*-weighted MRI showed low signal intensity areas in and around the tumors in rats that received labeled sensitized splenocytes. Prussian blue (PB), CD45- and CD8-positive cells were present in areas at the corresponding sites of low signal intensities seen on MRI. Rats that received labeled nonsensitized splenocytes did not show low signal intensity areas or PB positive cells in or around the implanted tumors. In conclusion, the immunogenic reaction can be exploited to delineate recurrent glioma using MRI following systemically delivered magnetically labeled sensitized splenocytes or T-cells.     

Cerebral Cortical Aquaporin-4 Expression in Brain Edema following Cardiac Arrest in Rats

OBJECTIVES: Brain edema occurs following clinical as well as experimental cardiac arrest (CA) and predicts a poor neurologic outcome. The objective of this study was to determine the expression of cerebral cortex aquaporin (AQP)-4, a member of a family of membrane water-channel proteins, in brain edema formation following normothermic or hypothermic CA. METHODS: Twenty-four rats were subjected to time-matched normothermic (N-Sham, 37.5 degrees C +/- 0.5 degrees C, n = 6) or hypothermic (H-Sham, 34 degrees C +/- 0.5 degrees C, n = 6) sham experiments and normothermic (N-CA, n = 6) or hypothermic (H-CA, n = 6) CA induced by asphyxiation for 8 minutes. Hypothermia was induced before CA. The animals were resuscitated with cardiopulmonary resuscitation, ventilation, and epinephrine administration. Brain edema was determined by brain wet-to-dry weight ratio at one hour of resuscitation. AQP4 immunoactivity in the cerebral cortex was determined using immunohistochemical staining and was semiquantified as an intensity of staining with an automated cell imaging system. RESULTS: Mild hypothermia in the sham experiments did not alter cerebral cortex AQP4 immunoactivity (mean +/- SD) (55.0 +/- 3.7 in H-Sham vs. 53.3 +/- 1.7 in N-Sham, p > 0.05). N-CA resulted in a significant increase in AQP4 immunoactivity (61.8 +/- 4.5) compared with N-Sham (p = 0.01) and H-Sham (p = 0.03). H-CA attenuated AQP4 compared with N-CA (53.4 +/- 1.3, p = 0.01). Brain wet-to-dry weight ratios were 4.41 +/- 0.07 in N-Sham, 4.40 +/- 0.08 in H-Sham (p > 0.05 vs. N-Sham), 4.55 +/- 0.04 in N-CA (p = 0.004 vs. N-Sham; p = 0.005 vs. H-Sham), and 4.43 +/- 0.09 in H-CA (p = 0.02 vs. N-CA; p > 0.05 vs. N-Sham and H-Sham). CONCLUSIONS: Cerebral cortical AQP4 expression is up-regulated after normothermic CA, which is attenuated by hypothermia induced before CA.     

THE RELATION OF HEMATIN TO PATHOLOGICAL PIGMENT FORMATION

1. It has been shown that powdered hematin is exceedingly resistant to the metabolic action of tissue cells, and wherever injected it will remain for weeks with but slight and slowly progressing alteration. 2. The changes produced in hematin by tissue cells are identical with those changes resulting from the oxidation of hematin by hydrogen peroxid, forming a series of bodies of decreasing color intensity, which manifest an iron reaction in inverse proportion to their color. 3. These hemosideroid pigments are distinguished from true hemosiderin by the type of their iron reaction, by their solubility in dilute alkalies, and by their destructive oxidation by hydrogen peroxid. 4. Crystalline hematin injected into the tissues is subject to the same changes as powdered hematin. 3. Whereas powdered parahemosiderin is converted into hemosiderin by the tissue cells with comparative ease, powdered hematin shows no such conversion within forty-seven days, and as the only demonstrable change produced in hematin by the tissue cells does not result in the formation of either hemosiderin or hematoidin, the assumption that hematin is the progenitor of these pigments seems unwarranted.     

V-Y advancement flaps. Reusable flaps for pressure ulcer repair

V-Y advancement modification of skin paddle design for the biceps femoris, tensor fascia lata, transverse lumbar, and gracilis flaps permits readvancement of each of these flaps for recurrent pressure ulcers. Our use of this refinement of these flaps over the past twelve years shows that up to two readvancements of each of these flaps can be done, thus preserving reconstructive options in a patient population prone to pressure ulcer recurrence.     

Left ventricular fibroma: echocardiographic diagnosis and successful surgical excision in three cases

The management of three patients with left ventricular fibromas is outlined. All were asymptomatic children. Routine chest radiography suggested cardiac masses. M-mode and two-dimensional echocardiography were valuable adjuncts to conventional angiography in assessing these children. Electrocardiographic changes, present in all cases, were shown to regress postoperatively. We stress the importance of these noninvasive aids in the initial investigation and outline our operative methods of reconstruction.