LYSOSOMAL IRON ACCUMULATION AND TUBULAR DAMAGE IN RAT PUROMYCIN NEPHROSIS AND AGEING

1. Energy dispersive X-ray spectrometry was used to examine the relationship between proteinuria and increased urinary iron excretion, and structural and functional damage in puromycin nephrosis. 2. After 11–12 days rats treated with puromycin (10 mg/100g, i.v.i.) had greater proteinuria (211.6 ± 35.7 mg/day, mean ± s.e.m.) and urinary iron excretion (15.4 ± 2.2 μg/day) than salinetreated controls (14.5 ± 1.4 mg/day and 1.1 ± 0.2 μg/day, respectively, both P<0.001). 3. On day 13, mean lysosomal iron concentration of proximal tubular cells (306.6 ± 64.5 vs 11.9 ± 8.6 mg%, P<0.001), and proximal tubular cell damage assessed semi-quantitively (1.17 ± 0.10 vs 0.62 ± 0.10, P<0.001) were higher and creatinine clearance (0.15 ± 0.01 vs 0.29 ± 0.02 mL/min perg kidney weight, P<0.001) lower than in control rats. 4. At days 35, 60 and 360 there were no differences in any of the measured parameters between rats treated with puromycin or saline, and in both groups proteinuria, tissue damage and lysosomal iron concentration increased with time. 5. Lysosomal iron accumulation was the only independent predictor of both functional and structural damage. 6. In conclusion, the apparent association between proteinuria and tubulo-interstitial damage in puromycin nephrosis, and with ageing, is best explained by factors associated with accumulation of iron within lysosomes of proximal tubule cells.     

Inter- and intra-individual variability of non-invasive tear break-up time in Hong Kong Chinese

Non-invasive tear break-up time (NITBUT) has been proposed as a measure of tear film integrity which is superior to the more commonly used tear break-up time (TBUT), since it does not alter the volume or the physicochemical properties of the tear layer by the addition of fluorescein. We measured NITBUT by measuring the time taken for distortions or discontinuities to appear in the reflected image of a grid pattern which covered about 80 per cent of the corneal surface. NITBUT measures were made 100 times on seven Hong Kong Chinese subjects with up to 20 consecutive measures being made on a single day. We also measured NITBUT on one occasion on an unselected population of 52 Hong Kong Chinese subjects. NITBUT shows a skewed distribution in all subjects, with many shorter values and some extremely long values. There are statistically significant variations in NITBUT from day to day, and from subject to subject. The group of 52 subjects also had a skewed NITBUT distribution with many short values and some very long values. The arithmetic mean does not adequately represent NITBUT data, either for individual subjects or for this group of subjects. As many as five to eight measures may be necessary to gain a stable estimate of the NITBUT and stability of the measure is improved if extreme values are omitted. We recommend the use of nonparametric statistics to compare NITBUT values from day to day in or between subjects.     

Flip side of synaptic plasticity: Long-term depression mechanisms in the hippocampus

There is growing interest in the phenomenon of long-term depression (LTD) of synaptic efficacy that, together with long-term potentiation (LTP), is a putative information storage mechanism in mammalian brain. In neural network models, multiple learning rules have been used for LTD induction. Similarly, in neurophysiological studies of hippocampal synaptic plasticity, a variety of activity patterns have been effective at inducing LTD, although experimental paradigms are still being optimized. In this review the authors summarize the major experimental paradigms and compare what is known about the mechanisms of LTD induction. Although all paradigms appear to initiate a cascade of events leading to an elevated level of Ca²⁺ postsynaptically, the extent to which these paradigms involve common expression mechanisms has not yet been tested. The authors discuss several critical experiments that would address this latter issue. Numerous questions about the properties and mechanisms of LTD(s) in the hippocampus remain to be answered, but it is clear that LTD has finally arrived, and will soon be attracting attention equal to its flip side, LTP. © 1994 Wiley-Liss, Inc.     

Basic ophthalmic assessment and care workshops for rural health workers

The inequitable distribution of medical services in Australia means that many rural dwellers do not have easy access to ophthalmic care. In regions with no medical personnel, appropriately trained rural health workers may provide ophthalmic assessment, primary treatment, and, in some circumstances, definitive care. In areas with overburdened services, these rural health workers may augment facilities already established. In an attempt to improve the accessibility and quality of ophthalmic services available to presently disadvantaged rural inhabitants, the aims, curriculum, and structure of a 'Basic Ophthalmic Assessment and Care Workshop', for the transfer of knowledge and skills to such rural health workers, is presented.     

Implications of remarriage and stepfamily formation for marriage education*

Couples in remarriages with stepchildren are a significant portion of the marriage population and have unique educational needs regarding aspects of couple functioning within the context of stepfamily development. From a review of the literature, we examine current curricula focused on these couples. Information is offered on implementation issues regarding recruitment, delivery context, facilitator and participant characteristics, and evaluation.     

An assessment of the characteristics of n-type diodes for use in electron beam radiotherapy.

Diodes are now commercially available for use in electron beams. This paper aims to assess their response and limitations under different clinical conditions. Parameters considered were applicator factors, focus skin distance (FSD), angle of incidence, and temperature dependence. The beam perturbation was also measured. The beam energies used varied from 5 to 17 MeV. Applicator factors, measured at the surface of a phantom, differed by up to 7% compared with ion chamber measurements at Dmax. Similarly, large differences were found in FSD dependence. The temperature dependence was found to be approximately double the manufacturer's specification at 0.7% per degree Centigrade and the angular dependence was within the specification of +/- 2% for angles of +/- 30 degrees. The beam perturbation was measured as a maximum of 25% for 5-MeV electrons. The measurements were compared to other published data but this is highly dependent on the methodology employed. It was concluded that the diodes could be used in some circumstances, but only if used with extreme caution. An extensive set of commissioning measurements would be required before introducing the diodes into use clinically.     

Ocular findings in the chromosome 22q11.2 deletion syndrome.

PURPOSE: To identify the ocular features of the chromosome 22q11.2 deletion syndrome and to provide ophthalmologic examination recommendations for affected patients. METHODS: Ocular abnormalities were evaluated prospectively in patients with 22q11.2 deletion at the Children's Hospital of Philadelphia between 1997 and 1999. RESULTS: Ninety patients with confirmed 22q11.2 deletion were examined. Posterior embryotoxon was found in 49%, tortuous retinal vessels in 34%, eyelid hooding in 20%, strabismus in 18%, ptosis in 4%, amblyopia in 4%, and tilted optic nerves in 1%. CONCLUSIONS: The high incidence of ocular conditions that can potentially affect visual development suggest that children with 22q11.2 deletion should undergo a comprehensive eye examination upon diagnosis of the condition with follow-up as indicated by the findings in each case. In addition, knowledge of the ocular findings, in conjunction with certain cardiac, otolaryngologic, immunologic, and other systemic findings, may alert physicians to the possibility of a chromosome 22q11.2 deletion.