Cone differentiation with no photopigment coexpression

PURPOSE: To decide whether the transitory coexpression of cone visual pigments described in the developing rat and gerbil retina is a universal feature of dichromatic mammalian species. METHODS: The rabbit, a species widely used in eye research, was selected for the study and a search made for the presence of cones that bound more than one cone antibody during the first postnatal week. To plot the densities of individual cone types and to colocalize the two visual pigments, immunocytochemistry on retinal wholemounts and consecutive tangential sections, respectively, were used. RESULTS: The sequence in which the visual pigments began to be expressed was the same as that observed in other mammals: first, rhodopsin; second, blue pigment; and last, green pigment. The striking increase in blue cone density numbers observed in the rat, however, did not occur in the rabbit. Instead, some days after the first blue cones appeared, the green cones also started to express their visual pigment, and this cone type soon outnumbered the blue cones. Within the limits of the immunocytochemical method, it was established that unlike the developing rat, the presence of double-labeled cones was not a character of the rabbit retina. CONCLUSIONS: Visual pigment coexpression is an interesting phenomenon of retinal development, however, it is not the exclusive scenario of photoreceptor differentiation. Each species must be carefully studied before deciding whether its retinal cones synthesize both pigments during retinal development.     

Effect of using prismatic eye lenses on the posture of patients with adolescent idiopathic scoliosis measured by 3-d motion analysis

This is a preliminary investigation to detect the body sway and postural changes of patients with AIS under different spatial images. Two pairs of low-power prismatic eye lenses (Fresnel prisms) with 5 dioptre and 10 dioptre were used. In the experiment, the apices of the prisms were orientated randomly at every 22.5 degrees from 0 degrees to 360 degrees to test changes. Four patients with mean age of 11 and Cobb's angle of 30 degrees were recruited and the results showed that the low-power prisms at specific orientations (157.5 degrees and 180 degrees) could cause positive postural changes (2.1 degrees-2.7 degrees reduction of angle of trunk mis-alignment) measured by 3-D motion analysis. This might be used for controlling their scoliotic curves by induced visual bio-feedback. Apart from this laboratory test, a longitudinal study is necessary to investigate the long-term effect of the prisms at different powers and orientations (under both static and dynamic situations) on the patient's posture, spinal muscular activities, vision, eye-hand coordination, psychological state and other daily activities before it becomes an alternative management of AIS.     

An autologous blood donation program for paediatric scoliosis patients in Hong Kong

A retrospective audit was conducted to determine the safety, efficacy and patient satisfaction related to a preoperative autologous blood donation program for children and teenagers undergoing corrective surgery for scoliosis. Forty-five of the 77 patients donated the requested amount of blood. These 45 compliant patients had been requested to donate fewer units of blood than noncompliant patients (mean 4.0 vs 4.6 respectively, P = 0.02). Twelve patients required allogeneic blood transfusion. Two patients had surgery delayed making the collected autologous blood unavailable. The extent of the operation was associated with the need for allogeneic blood transfusion. Six and a half percent of all donated units of blood were discarded. No major complications were reported. Overall, 93% of patients were satisfied with the program. With careful patient selection, good inter-departmental coordination and teamwork, preoperative autologous blood donation in paediatric patients undergoing extensive corrective surgery for scoliosis is safe and effective.     

Homogenous distribution of fast response action potentials in canine pulmonary vein sleeves: a contradictory report

Pulmonary veins may serve as source of ectopic focus (or foci) in initiating atrial tachyarrhythmias in human beings. However, the animal model for such focal atrial fibrillation is still lacking and cellular mechanism for arrhythmias remains to be studied. Recently, a series of reports of cellular electrophysiological characterization of pulmonary vein sleeves demonstrated an extremely high incidence of automaticity (varied from 40 to 76%) and triggered activity (from 0 to 44%) in normal healthy control dogs and rabbits. The present study was therefore designed to re-investigate the cellular electrophysiological properties of canine pulmonary veins. Intracellular action potentials were characterized in pulmonary vein sleeves in 50 normal healthy dogs. Conventional glass microelectrode recording technique was used. Experiments were focused on the incidence of automaticity and triggered activity in pulmonary vein sleeve tissues. Surprisingly, our results showed that all pulmonary vein sleeves tissues in these dogs displayed fast-response action potentials under the well-controlled experimental condition (100%, n=50). No spontaneous pacemaking activities, early or delayed afterdepolarisations were observed (0%, n=50). No high-frequency spikes or irregular rhythm could be recorded in all experiments (0%, n=50). Both the frequency response and membrane responsiveness of the pulmonary vein action potentials were characterized. No electrophysiological inhomogeneity between the distal and the proximal part of the sleeves was observed. In conclusion, canine pulmonary vein sleeves do not display arrhythmogenic activities under normal physiological conditions. The possible explanations for the controversy in pulmonary veins electrophysiology were discussed.     

Technetium-99m-sestamibi/pertechnetate subtraction scintigraphy vs ultrasonography for preoperative localization in primary hyperparathyroidism

A prospective study was performed to evaluate the efficacy of technetium-99m-sestamibi and technetium-99m-pertechnetate subtraction scanning and US for imaging parathyroid glands in primary hyperparathyroidism. Sixty-three patients were surgically treated for primary hyperparathyroidism (HPT). Preoperative scintigraphy and US were performed in all cases. Bilateral neck exploration was carried out on each patient. Results of radionuclide studies and US were compared with surgical and histological findings. In 57 patients with primary HPT the radionuclide scanning gave true-positive results. Four false-negative and two false-positive scintigrams were obtained. The sensitivity and the positive predictive value (PPV) of scintigraphy were 93 and 97%, respectively. Forty-one cases were correctly localized by the US. Seventeen US results were false negative and five were false positive. The sensitivity and the PPV for US were 71 and 89%, respectively. There was a statistically significant difference between the sensitivity of the scintigraphy compared with the US ( p=0.001). Sensitivities of radionuclide scans and US were higher for adenomas (100 and 83%) than for hyperplastic glands (75 and 40%). The sensitivity of technetium-99m-sestamibi and technetium-99m-pertechnetate subtraction scintigraphy was significantly higher compared with US. This sensitive method could help surgeons in performing a rapid and directed parathyroidectomy.     

Flexion-distraction injuries in the thoracolumbar spine: an in vitro study of the relation between flexion angle and the motion axis of fracture

A new concept, the motion axis of fracture (MAF), which is defined as the transitional point from anterior compressive to posterior splitting failure on a lateral radiograph, has provided a true understanding of the mechanisms of flexion-distraction injuries in clinical cases. This study was designed to produce in vitro injuries that have MAFs and to clarify the relation between the flexion angle and the MAF location. Adolescent porcine thoracolumbar spines were exposed to a vertical compressive load to failure at three different flexion angles and then examined radiographically. The MAF location was recorded as the distance from the anterior border to the MAF expressed as a percentage of the anteroposterior diameter of the vertebral body. All specimens showed similar injuries, with MAFs consisting of anterior compression fractures in the vertebral bodies and posterior disruptions. A significant negative correlation emerged between the flexion angle and the MAF location (r = -0.890; p < 0.0001). These results suggest that even a vertical compressive load contributes to the production of a flexion-distraction injury with an MAF in the thoracolumbar spine. They also indicate that the flexion angle of the spine at which the vertical compressive load is applied is an important factor in determining the MAF location; that is, the larger the flexion angle, the more anterior the MAF.     

Suprasellar ectopic pituitary adenoma presenting as cranial diabetes insipidus.

We describe the occurrence of a supracellar ectopic pituitary adenoma in a 34 year old woman who presented with cranial diabetes insipidus and subsequently developed galactorrhoea-amenorrhoea. The tumour was demonstrated by both contrast computed tomography scan and magnetic resonance imaging with gadolinium enhancement and was confirmed at operation. Histological examination showed that the suprasellar lesion consisted of a pituitary adenoma while the pituitary biopsy revealed an unrelated pituitary microadenoma embedded in normal pituitary tissues. A review is made of the reported cases of ectopic pituitary adenomas.     

Factors affecting cosmetic outcome in breast-conserving cancer treatment--objective quantitative assessment.

A battery of objective measurements of cosmetic outcome was performed on 114 patients who had been treated by breast-preservation techniques for breast cancer. Cosmetic breast retraction, as determined by Breast Retraction Assessment (BRA) measurements, was significantly greater in patients who underwent extensive primary tumor resection, were more than 60 years old, weighed more than 150 lbs, or had a primary tumor in an upper breast quadrant. While use of a local RT boost, per se, was not a significant factor, those patients with high dose and/or large volume local boosts more frequently had marked retraction. Breast telangiectasia and depigmentation (T/D) was related to use of a local RT boost, patient age greater than 60 years, and use of separate nodal RT fields. Breast T/D was significantly more frequent with use of electron beam local RT boost which delivered a boost skin dose exceeding 1600 cGy. Objective quantitative assessments, such as BRA and T/D area measurements, provide data to determine factors related to each type of cosmetic change and thus provide guidelines for optimizing cosmetic outcome. Limiting the extent of primary tumor resection may minimize the amount of breast retraction. Omitting the local RT boost, particularly large volume, high dose boosts, may reduce the frequency of marked cosmetic retraction and skin T/D.