Biomedical subjects
Publications and source records attributed to C I Phillips.
Three brothers had bilateral retinoblastoma: one other sibling, a girl, had normal eyes. The parents were second cousins once removed. The father's right divergent eye, 'amblyopic' from childhood, showed a large atrophic patch in the macular area, probably a spontaneously resolved retinoblastoma.
5-S-cysteinyldopa concentrations were determined by high-pressure liquid chromatography and electrochemical detection in plasma from normally pigmented patients and patients with oculocutaneous albinism, both tyrosinase-positive and tyrosinase-negative. The plasma 5-S-cysteinyldopa concentrations were similar in all three groups, suggesting that 5-S-cysteinyldopa can be produced by mechanisms which do not involve tyrosinase.
The commonest cause of blindness among the 67 patients at the Yamanashi School for the Blind was congenital cataract (16). Next was retinitis pigmentosa or choroido-retinal degeneration (8), then retinopathy of prematurity (7). Congenital glaucoma and brain tumor each contributed five. Four were due to microphthalmia/micro-cornea and five to high myopia. Direct ocular trauma caused three. Two each were attributable to complete albinism, aniridia, congenital nystagmus and bilateral retinoblastoma. Single cases each of anophthalmos, Behçet's disease, Hallerman-Streiff syndrome, hydrocephalus, macular degeneration and optic atrophy were recorded. 41.8% of all cases were "very probably" hereditary and a further 10.4% "probably" so. 12.2% of the hereditary cases had consanguineous parents. An autosomal recessive (AR) cause is the likeliest explanation for the majority of the nonenvironmental causes (42.9% very probably AR and 14.3% probably AR), so that the possibility of prevention by genetic counseling was limited, but should have been given as soon as the first affected child was born. Parental consanguinity supports an autosomal recessive cause. 10.2% are very definitely due to an autosomal dominant gene; in them, counseling may well also have had a limited effect but might have prevented the birth of one or both of the siblings with aniridia inherited from the mother, and at least two, if not all three, of the three siblings with congenital cataract also inherited from the mother.
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A peripheral corticosteroid blocker RU 486-6, instilled as a 1% suspension at random into one eye of 12 rabbits, produced a consistent fall in intraocular pressure as measured by a hand-held applanation tonometer, when compared with the fellow control eye. This or a similar drug may be applicable for treatment of human open-angle glaucoma, or ocular hypertension, by eliminating that part of ocular tension attributable to the effect on aqueous outflow of the normal and fluctuating level of tissue corticosteroids.
Some problems of cataract epidemiology are briefly reviewed. Studies of the incidence and prevalence of cataract, and of economic status, measure social need but cannot, by themselves, point to possible causes. Information on geographical or regional distributions and medical, clinical and occupational studies permit the formulation of socially, medically or experimentally testable hypotheses concerning specific contributory factors. We have found several such factors to be significantly associated with cataract; they appear to be risk factors. Some risk factors are associated with subclinical deviations from the range of normal concentrations of certain plasma constituents, whereas clinically or experimentally acute deviations are known to be rapidly cataractogenic. Other risk factors include medical conditions and certain drugs. Although individuals may have several risk factors, controls have significantly fewer than cataract patients of the same age. This difference in the number of risk factors is also age-related, as is the degree of divergence from the normal range in the concentrations of several plasma constituents.
Both intraocular pressure and aqueous humour turnover rate were determined at intervals over three months in three females in order to investigate whether a correlation existed between these variables and the menstrual cycle. Not only was there a lack of correlation between intraocular pressure or aqueous humour flow rate and menses but intraocular pressure and aqueous humour flow rate were also not related to each other. If pharmacologically administered doses of progesterone or oestrogen influence intraocular pressure, the present data indicate that the effect is probably mediated through effects on the aqueous outflow pathways.
A young man of 17 years presented with bilateral reduced vision because of cataracts. Investigations showed a low level of serum calcium along with other evidence of renal failure. The cataracts were mainly in the posterior pole (cupulliform); faint peripheral cortical opacities were also present--in the form of about a dozen half-loops straddling the equator and extending about half way towards the axial centre of the lens.
The specific activities of glutathione reductase (GR), EC 1.6.4.2, and aldolase, (ALD) EC 4.1.2.13, were determined in the homogenates of 60 cataractous lenses. Concentrations of certain plasma constituents and the morphological types of cataract of the patients were known. Investigations were aimed at establishing a possible correlation between enzyme activities and plasma constituents as well as between the specific activities of GR and ALD and type of cataract. A correlation between the specific activity of GR and the urea content of the blood could be identified. Results also indicated a relationship between the decrease in GR activity and the formation of cortical cataracts.
Informative members of more than twenty families with X-linked retinitis pigmentosa have been sampled by venipuncture and DNA extracted from peripheral blood leucocytes and lymphoblastoid cell lines. X chromosome-specific recombinant DNA probes have been isolated from an X chromosomal genomic DNA library obtained by flow-sorting human chromosomes. These, and similar probes obtained from other laboratories, are being used to identify restriction fragment length polymorphisms in retinitis pigmentosa obligate heterozygotes. By analysis of linkage relationships in the offspring of double heterozygotes, it may be possible to localize the gene(s) responsible for this disorder to a particular subregion of the X-chromosome. Such probes are potentially useful for carrier detection and prenatal diagnosis.
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Problems of epidemiological studies of cataract are outlined. Some results are reported from a study on 931 cataract patients and 325 non-cataractous individuals. After correction by age and sex several single variables were found to have significant positive or negative correlations with cataract. Interactions between variables were found; these include age, diabetes, the use of diuretics and cataract, between age, sex, the level of alcohol consumption and cataract, and between age, sex, plasma urea levels and the use of different diuretic drugs, only some of which were found to have a positive association with cataract.
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A brother and sister, children of normal parents are described. They had retinitis pigmentosa, causing near-blindness as a result of very narrow fields of vision, associated with metaphyseal chondrodysplasia and marked shortening of the metacarpals and terminal phalanges. Autosomal recessive inheritance is suggested with a common biochemical cause for all these defects. This apparently new association of retinitis pigmentosa with a systemic bone dysplasia emphasises that this not uncommon clinical diagnosis has a variety of different possible causes.
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Tonometry in 9 eyes (7 patients) provides some evidence that timolol eye drops are useful in improving control of pressure in eyes operated for closed-angle glaucoma. In cases 1 and 2 (Figs, 1 and 2) this beta 1 and 2 blocker reduced pressure consistently. Case 3 (Fig. 3) showed that timolol 0.5% twice daily was as effective as pilocarpine 2% or 4% with adrenaline 1%. The effect of timolol 0.5% in case 4 (Fig. 4) and case 6 (Fig. 6) was additive to pilocarpine and adrenaline; in case 5 (Fig. 5) it probably improved the effect of adrenaline, but in cases 4 and 5 there may have been some loss of effect with time. Case 7 (Fig. 7) showed a good effect of timolol, reversed on withdrawal, but pressure fell again in spite of continued withholding of timolol. Timolol will be especially valuable in the control of pressure if an operation involving iridectomy has not been completely successful in open-angle glaucoma or more especially in closed-angle glaucoma because it has no effect on the pupil. Miotics will tend to produce posterior pupillary synechiae because aqueous humour will go through the iridectomy, not under the edge of the pupil. The danger will be greater in eyes with closed-angle glaucoma because the pupil is closely applied to the anterior lens surface, which will also tend to produce irritative iridocyclitis.
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