Capsular 'pits' in the human lens

The lens capsule is an atypical basement membrane surrounding the lens epithelial cells and lens fibres which make up the remainder of the human lens. A seemingly unreported morphological change visible in the lens capsule with the biomicroscope is described.

Autofluorescence of the crystalline lens in early and late onset diabetes

Blue/green autofluorescence (excitation around 420 to 430 nm, emission around 520 nm) of the crystalline lens has been studied by an in vivo photographic method in two populations of diabetics and controls. The populations consisted of a geographically based survivor group of 161 mixed early and late onset diabetics (and 133 non-diabetic controls) and a second group of 104 early onset insulin dependent diabetics (and 138 non-diabetic controls), the latter all with non-cataractous lenses. Powerful associations (p less than 10(-6) were found between the presence of diabetes and increased lenticular autofluorescence in both populations. Among the mixed diabetics diabetic type was a significant factor after accounting for the effects of age and diabetic duration. In the early onset group (clear lenses) a powerful association existed between autofluorescence and diabetic duration (p = 0.000011) after allowing for the effect of age, while in a subgroup of late onset diabetics with clear lenses this effect was modest (p = 0.015). In the early onset diabetic group diabetic retinopathy (p = 0.0064) was associated with increased lenticular autofluorescence after allowing for the effects of age and diabetic duration. In addition a powerful interaction between diabetic duration and the presence of diabetic retinopathy (p less than 10(-6) was found in this subgroup. Among the geographically based population of diabetics, increased nuclear brunescence was powerfully associated (p less than 10(-6) with increased autofluorescence after allowing for the effects of age, diabetic duration, and type of diabetes. This association was not found in the non-diabetic population. Non-enzymatic glycosylation of lens proteins should be considered as a possible mechanism of production of the fluorogen with emission around 520 nm.

Changes in light scatter and width measurements from the human lens cortex with age

Light scatter and width measurements of the anterior cortical layers of the human lens were made in 50 eyes of 50 subjects using computerised linear scanning densitometry of Scheimpflug images. It was demonstrated that the amount of light scatter increased with age in all of the three major zones and that zone C3 showed the most marked increase. Most lens growth occurs in zone C2 with C3 showing little increase in width once it has become established. Zone C1 showed a tendency to decrease in width with age. In addition it was shown that the C3 zone, which is not present at birth and during early childhood, appears as a distinct layer during the second decade of life. Its scattering properties continue to increase throughout life, exceeding all other zones after approximately 30 years of age, in the absence of cataract. Possible explanations for the lens zone pattern are discussed.

Inter and intra observer reproducibility of the new Oxford CCD Scheimpflug camera

Scheimpflug photography is a well recognised technique for obtaining sagittal views of the anterior structures of the human eye in vivo. A new generation of Scheimpflug camera, which uses a CCD (charge coupled device) instead of film, permitting the digitised image achieved to be directly analysed using computerised linear scanning densitometry, is described. The advantages and present limitations of this system over the older film using system are discussed and the reproducibility of the new CCD system in its ability to measure certain features of the crystalline lens is presented.

Comparative human cellular radiosensitivity: III. Gamma-radiation survival of cultured skin fibroblasts and resting T-lymphocytes from the peripheral blood of the same individual

Skin and blood samples were obtained from 34 donors, for whom there was no indication of abnormal radiosensitivity. From these, in 33 cases both fibroblast and T-lymphocyte cultures were obtained and in 26 cases at least three fibroblast and at least two G0 (resting) T-lymphocyte survival assays were possible. Within this set of results, differences in radiosensitivity between donors were significant for fibroblasts but not T-lymphocytes, although the range of radiosensitivity was similar for the two cell types (D 0.90-1.68 Gy for fibroblasts; 1.26-2.15 Gy for T-lymphocytes). Furthermore, there was little evidence for a correlation in radiosensitivity between the two cell types. These results suggest limitations in the predictive value of conventional measurement of cell survival.

The acuityscope: a resolution test target projection ophthalmoscope

The Acuityscope projects an image of a three bar resolution test target onto the patient's retina, where it is viewed and read by an observer. The test target consists of a series of three bar targets varying in size on a logarithmic scale. Individual targets are identified in the projected image by Bailey-Lovie log visual acuity equivalents. The projected image includes only those target sizes which are useful for estimating visual acuity. The Acuityscope is used for assessing the quality of retinal image formation, and is thus able to differentiate between poor visual acuity due to image degradation, (e.g. cataract or corneal disease) and poor visual acuity due to image handling defects (e.g. retinal or optic nerve disease). The use of the instrument is relevant to both clinical situations (e.g. pre-operative assessment of opacification of optical media) and experimental situations (e.g. clinical trials).

Adaptation of postimplantation embryos to culture: membrane lipid synthesis and response to valproate

The environment of the conceptus in culture is quite different from that in utero. It is likely that the embryo adapts to this environment in various ways, but little is known of adaptation, nor of its significance to mechanistic studies using embryo culture. To illustrate this area, we summarize data from two comparative studies: of membrane lipid synthesis by conceptuses in culture and in utero, and of the morphologic response of conceptuses to valproate in these two environments. The synthesis of the major membrane lipids, cholesterol and phospholipids, is significantly affected by culture. De novo synthesis of cholesterol progressively increases during culture, compared to equivalent stages in utero. In contrast, phospholipid synthesis decreases in culture. Cultured conceptuses were morphologically similar to those in utero, suggesting that apparent structural normality does not guarantee biochemical activity equivalent to that in vivo. Conceptuses exposed to valproate in vivo showed a wide range of severity of defects. Those abnormalities that apparently permit survival to term seem relatively subtle, while more severe defects (as usually reported in culture studies) appear to be lethal. Subtle defects, very similar to those induced in vivo, can be reproduced in culture, but only with short-term, not continuous, exposure. We have previously proposed that valproate may interfere with embryonic lipid synthesis. Thus, despite lipid synthetic pathways adapting to the culture environment, the response to valproate in vitro, can mimic that in utero, with appropriate exposure conditions.

The development of handed asymmetry in aggregation chimeras of situs inversus mutant and wild-type mouse embryo

Mutant iv/iv mice develop as if they have no sense of left and right, so the development of asymmetry is random: half normal, half as a mirror-image of normal, situs inversus. We have made aggregation chimeras of 8-cell stage iv/iv and +/+ embryos, transferred them into pseudopregnant mice, and examined their phenotype on day 10 of gestation. The contribution of mutant and wild-type cells to tissues of the embryo was estimated by strain-specific isozyme (GPI-1) analysis. We have also performed reciprocal embryo transfers, iv/iv blastocysts into +/+ mice, and vice versa. These transfers show that the development of handed asymmetry is determined by embryonic genotype, and is unaffected by the maternal environment (at least after day 3), or by the procedures of embryo collection, culture and transfer. Our observations on the development of 21 viable chimeric embryos show that neither iv/iv nor +/+ cells are dominant. All embryos (12) with less than 50% contribution of iv/iv cells to the heart developed with normal situs. Of 9 embryos with greater than 50% iv/iv cells, only 2 developed with inverted situs. These findings suggests that there was partial ‘rescue’ of embryos by some influence of normal over mutant cells. However, we cannot, statistically, exclude an alternative interpretation that cells are behaving autonomously. Interestingly, the embryos that developed with inverted situs were unique in having greater than two thirds contribution of iv/iv cells to both the heart and the visceral yolk-sac.

Biometry of the crystalline lens in early-onset diabetes

Lenticular biometry on non-cataractous lenses has been studied by means of Scheimpflug photography and digital image analysis in 153 patients with early-onset insulin-dependent diabetes and 153 non-diabetic controls. Anteroposterior axial lens thickness, cortical thickness, nuclear thickness, anterior and posterior lenticular curvatures, and anterior chamber depth were assessed. Highly significant differences between the lenses of the diabetic subjects and non-diabetic controls were found. After the effect of age had been accounted for within the diabetic subgroup, diabetic duration was found to be a highly significant determinant of lens dimensions, such that age-related dimensional changes for various biometric parameters were accelerated by between 52% and 121% after the onset of diabetes. Because the diabetic duration of the early-onset diabetic subjects studied in this work was accurately known, this report is the first in which a precise assessment of the effect of 'true' diabetic duration on lens biometry has been possible.

Induction of alkaline phosphatase in mouse L cells by overexpression of the catalytic subunit of cAMP-dependent protein kinase

Mouse L929 cells were used to study the mechanism of cAMP induction of alkaline phosphatase (AP) activity. Following treatment with 200 microM 8-chlorophenylthio-cAMP (CPT-cAMP), alkaline phosphatase enzyme activity was observed to increase 80-fold after 24 h. The CPT-cAMP dose response of the alkaline phosphatase enzyme activity correlated well with the CPT-cAMP activation of cAMP-dependent protein kinase in L cells. A cDNA clone for the alkaline phosphatase was isolated and used to demonstrate a 10-fold increase in alkaline phosphatase mRNA levels after a 24-h treatment of L cells with CPT-cAMP. Increased mRNA levels were first detected 4-6 h, after CPT-cAMP treatment, and the level of alkaline phosphatase mRNA decreased rapidly after removal of CPT-cAMP. In vitro nuclear transcription studies showed that a 3-fold increase in alkaline phosphatase gene transcription was detectable 6 h after CPT treatment, and this increase was blocked by cycloheximide. In order to determine if the catalytic (C) subunit of cAMP-dependent protein kinase was able to mediate the induction of AP, L cells were transfected with expression vectors containing the metallothionein promoter and coding for the C alpha isoform of the catalytic subunit of cAMP-dependent protein kinase or for a catalytic subunit in which lysine 72 had been mutated to methionine (C alpha K72M). Zinc treatment of stably transfected cells expressing the wild-type C subunit showed an increase in protein kinase activity and an increase in AP activity. Zinc treatment of cells containing the mutant C subunit expression vector produced an increase in the amount of a protein which was recognized by C subunit antibodies on Western blots, but these cells showed no increase in protein kinase activity or in AP activity. We conclude that the C subunit is sufficient for transcriptional induction of the AP gene and that the phosphotransferase activity of the C subunit is required for this induction.

Light scatter from the central human cornea

Light scatter from the central human cornea was measured in 60 eyes of 60 patients using computerised image analysis of Scheimpflug slit image photographs. There was no correlation between the amount of scatter and the age of the patients (correlation 0.035, p = 0.79). In addition it was found that light was scattered more at the anterior and at the posterior surfaces of the cornea than from the stroma.

The Oxford modular cataract image analysis system

A modular system of acquisition and analysis of Scheimpflug, retro-illumination and fluorescence images of the in vivo human crystalline lens is described. Image analysis is directed towards the following goals: Scheimpflug slit-images are analysed for: (1) The optical density of nuclear cataract present; (2) The dimensions of the lens and the lenticular zones; (3) The curvatures of the lens and lenticular zones. Retro-illumination images are analysed for: (1) The percentage area which is occupied by cataract; (2) A combined measure (weighted integral) describing both the amount of cataract present and its optical density. Lenticular auto-fluorescence images are analysed for the mean density (fluorescence) of the lens as a whole. A pilot study of the repeatability of the methods is presented.

The development of handedness in left/right asymmetry

The development of handed asymmetry requires a special mechanism for consistently specifying a difference between left and right sides. This is to be distinguished from both random asymmetry, and from those left/right differences that are mirror symmetrical. We propose a model for the development of handedness in bilateral animals, comprising three components. (i) A process termed conversion, in which a molecular handedness is converted into handedness at the cellular level. A specific model for this process is put forward, based on cell polarity and transport of cellular constituents by a handed molecule. (ii) A mechanism for random generation of asymmetry, which could involve a reaction-diffusion process, so that the concentration of a molecule is higher on one side than the other. The handedness generated by conversion could consistently bias this mechanism to one side. (iii) A tissue-specific interpretation process which responds to the difference between the two sides, and results in the development of different structures on the left and right. There could be direct genetic control of the direction of handedness in this model, most probably through the conversion process. Experimental evidence for the model is considered, particularly the iv mutation in the mouse, which appears to result in loss-of-function in biasing, and so asymmetry is random. The model can explain the abnormal development of handedness observed in bisected embryos of some mammalian, amphibian and sub-vertebrate species. Spiral asymmetry, as seen in spiral cleavage and in ciliates, involves only conversion of molecular asymmetry to the cellular and multicellular level, with no separate interpretation step.

Relationship of cataract to radiation sensitivity

Considerable exposure to radiation always causes posterior subcapsular cataract (PSC). This investigation was conducted to ascertain whether cellular hypersensitivity to radiation may be identified as a possible cause of cataract in persons exposed to low levels of radiation. Patients were studied in whom PSC had followed probable exposure to low levels of radiation or in whom PSC had developed before the age of 60 without known exposure. The patients with cataract were compared with age and sex matched controls without cataract. Radiation sensitivity was estimated by measuring clonal growth of skin fibroblasts and peripheral blood lymphocytes after exposure to graded doses of radiation and by measuring postirradiation reconstruction of separated nuclear material from lymphocytes. The results show variations in the level of radiation sensitivity between the patients, without significant differences from the controls. It is concluded that radiation hypersensitivity, as tested by the methods used in this study, is not normally associated with the development of posterior subcapsular cataract.

The development of asymmetry: the sidedness of drug-induced limb abnormalities is reversed in situs inversus mice

We are studying the development of handedness, in particular the relationships between handed structures with bilateral symmetry, for example the limbs, and those with lateral asymmetry, such as the heart, lungs and gut. Asymmetric (unilateral) developmental limb abnormalities can be induced by chemical treatment of mouse embryos, either in utero by acetazolamide, or in culture by misonidazole. We have examined these effects in mice homozygous for the iv gene. The development of bilateral symmetry in iv/iv mice is normal, but the control of asymmetry appears to be random, that is 50% develop normally (situs solitus), 50% with laterally inverted viscera (situs inversus). We find that the handedness of induced asymmetric limb defects is highly correlated with embryonic visceral situs. Right limb defects are induced in situs solitus embryos, left-sided defects in situs inversus. This suggests that the mechanism of induction of asymmetric defects is not related to any intrinsic difference between the development of left and right limbs, but is connected to visceral asymmetry. In addition, the high correlation of limb defects with situs was observed in culture as well as in utero suggesting that the maternal environment plays no role in the development of asymmetry.

Lamellar separation in the human lens: the case for fibre folds. A combined in vivo and electron microscopy study

Lamellar separation is seen as parallel lines in the lens cortex. It has been the subject of a joint study between Oxford and Amsterdam. The condition was studied in vivo by macro photography and in vitro by scanning electron microscopy. The lines are seen to run concentric with the lens equator, crossing the lens fibres at right angles. The lines are commonly limited by a spoke cataract, a water cleft, or a lens suture. The line may continue beyond these features with a change in direction. The lines may branch and rejoin. The lines extend in depth into the lens, polarised light showing that the lines are due to reflection. The name 'lamellar separation' implied that the appearance is due to separation between the lens lamellae. Lamellar separation is now shown by electron microscopy to be due to folds crossing the lens fibres. The clinical study showed the lines occurring with spoke cataract and the electron microscopy showed the association with the novel finding of peripheral breaks in the fibres. A new name 'Fibre Folds' is proposed.

The prevalence and morphology of cataract in patients on allopurinol treatment

We have shown that an unusual morphological thinning of the anterior clear zone of the lens is found in patients with gout on long term Allopurinol therapy. The significance of this is discussed.

Clinical and serological features of human herpesvirus-6 infection in three adults

3 adult patients with serological evidence of human herpesvirus-6 (HHV-6) infection had mild, afebrile illnesses with nonspecific symptoms. In each case, the characteristic clinical feature was the presence of enlarged, bilateral, non-tender, anterior and posterior cervical nodes early in the illness which persisted for up to 3 months. HHV-6 IgG antibody reciprocal titres of 160 to 2560 were found during acute infection, and decreased to a titre of 10 in 1 patient 3 years later. IgM responses were detected at low reciprocal titres (10) in 2 patients and disappeared after several months.

Central compaction in the process of lens growth as indicated by lamellar cataract

The lens growth through life is the net result of surface accretion partially offset by central compaction. Compaction has previously been shown to affect the cortex. The present study examines compaction in the nucleus by measuring the change in dimensions of congenital lamellar cataract with time and by comparing the different dimensions of dominantly inherited lamellar cataract in individuals of different ages in the same family. It is now shown that compaction affects the nucleus at a decreasing rate with increasing age and that the rate of compaction of lamellar cataracts is faster the greater diameter of the affected lamella. It is concluded that compaction of lens fibres towards the centre of the lens affects all regions of the cortex and nucleus in youth and that the compaction becomes largely or completely confined to the cortex in middle age and beyond. The shape of the lamellar cataract changes from a lenticular shape in youth to a rounded shape with increasing age. This accounts for the development of the peripheral divergence of the zones of discontinuity of the cortex, which allows the lens to remain emmetropic with increasing age in spite of changes in surface curvature.

Control of astigmatism in cataract surgery

A study is reported on cataract surgery, with intraocular lens implant, with measurement of the preoperative astigmatism and of the postoperative astigmatism over 28 weeks. Nine interrupted 10/0 nylon sutures are used to close a limbal section. Preoperative astigmatism is compensated for in the method of suturing by the placement of additional sutures. Postoperatively sutures are cut in line with the plus cylinder axis in eyes showing excessive astigmatism with the rule. Final postoperative astigmatism is controlled within 2.25 D cyl. 68% of cases lie within 1.0 D cyl with the rule to 1.0 D cyl against the rule. The average case in which sutures are not cut is one having 1.51 D cyl with the rule at one week postoperatively, declining to zero at approximately 12 weeks, and having a final value of 0.17 D cyl against the rule. No significant change in cylinder is seen after 10 weeks. The final postoperative astigmatism is only weakly correlated with the preoperative astigmatism, showing that the surgical method is effective. The spherical equivalent error is shown to shift in the direction of myopia in the postoperative period.

B-cell lymphoproliferation and lymphomagenesis are associated with clonotypic intracellular terminal regions of the Epstein-Barr virus

We analyzed 17 B-cell lineages cloned from two patients with infectious mononucleosis and found that different B-cell lineages exhibited notable variation in the length of the fused Epstein-Barr virus (EBV) terminal region on intracellular EBV episomes. EBV termini in different B-cell clones from the same person differed by as many as 15 to 20 reiterations of the ca. 500-base-pair terminal repeat sequence. In contrast, analysis of seven B-cell lineages cloned from a patient with a fatal, oligoclonal lymphoma revealed that three of the cell clones had the same-sized EBV terminal region. These three clones had previously been shown, by immunoglobulin gene analysis, to be metastatic daughter cells descended from a common progenitor. Similarity of the EBV terminal regions in the three daughter clones suggested that EBV infected the progenitor cell before proliferation and metastasis. Individual, EBV-infected cells from a single individual showed sufficient heterogeneity in their EBV termini to allow use of terminal fragment size as a clonal marker in studies addressing the contribution of EBV to the clonal pathogenesis of tumors with which this virus has been associated.

B-cell lymphoma in severe combined immunodeficiency not associated with the Epstein-Barr virus

Patients with congenital and acquired immunodeficiencies are at increased risk for the development of B-cell lymphoproliferative disorders. When the appropriate tests have been performed, the Epstein-Barr virus (EBV) nuclear antigen (EBNA) or EBV DNA has been found in tissues from these tumors. These data have provided support for the idea that these tumors are associated with EBV. In this article we report about a child with severe combined immunodeficiency (SCID) who developed a malignant B-cell lymphoma that was not associated with EBV. The B-cell lymphoma in the patient proved to be, by hybridization analysis of immunoglobulin (Ig) heavy chain gene rearrangements of tumor-cell DNA, of clonal origin. However, neither EBNA nor EBV DNA could be detected in tumor tissue by anticomplement immunofluorescence or in situ cytohybridization with an EBV DNA probe. Furthermore, EBV DNA could not be detected by Southern blot hybridization using two EBV DNA hybridization probes on the same DNA blots that clearly contained the clonal Ig gene rearrangement. This case represents a clonal B-cell lymphoma occurring in a severely immunodeficient patient that was not associated with EBV. Antiviral chemoprophylaxis has been recommended for the prevention of EBV-related B-cell lymphoproliferations in transplant patients. Such prophylaxis may be ineffective in patients with B-cell lymphoproliferative disorders not associated with EBV.

An estimate of the size and shape of the human lens fibre in vivo

The size and shape of the lens fibres were estimated by specular reflex photography. The fibres were measured in three separate regions. Peripheral fibres have a mean width of 10.2 micron, the central fibres 11.9 micron, and the central fibres with suture 15.8 micron. Measurements were made of the taper (becoming narrower towards the suture) and flare (becoming wider towards the suture). The peripheral fibres have a mean taper of 0.3 micron per 100 micron. The central fibres have a mean flare of 0.6 micron per 100 micron, and the central fibres with suture have a mean flare of 2.4 micron per 100 micron. These differences are highly significant (p less than 10(-6]. From these measurements the overall shape of the average lens fibre was estimated. This fibre tapers as it passes forward from the equator to the peripheral extent of the lens sutures and then flares increasingly as the junction with the lens suture is approached. A mean increase in peripheral lens fibre width with age at 0.028 micron per year was demonstrated. This is significant (p = 0.042). No difference in fibre width was found in diabetics and non-diabetics.

Cataract: the relation between myopia and cataract morphology

The association between high myopia and cataract is already well established and an association between simple myopia and cataract has been suggested, but it has not been clear to what extent the myopia precedes the cataract or is the result of it. The present study compares the refraction of a group of 100 British patients at the time of first presentation with cataract in whom the refraction was also known four years previously, with a group of matched controls in whom the refraction was also known four years previous to presentation. The study shows that simple myopia does not appear to predispose to cataract. It is the development of the cataract itself, in particular nuclear sclerosis, which causes the refractive change towards myopia. The myopic change precedes the development of cataract, and patients over the age of 55 showing a myopic change in refraction have a very high probability of developing nuclear sclerotic cataract. The healthy aging eye and eyes with cortical cataract or subcapsular cataract, but without nuclear sclerosis, continue to show a gradual hypermetropic change with time.

An estimate of the human lens epithelial cell size in vivo

There are few previous estimates of the size of the human lens epithelium. In this study the lens epithelium is measured by specular reflex photography with a macro camera. The results are corrected for cornea magnification. One hundred subjects were studied ranging in age from 11 to 75 and including 20 diabetics and 18 subjects with cataract. The results show a range of epithelial cell diameters from 8-21 microns with 97% of the measurements lying in the 9-17 microns range. Pleomorphism is marked. The mean cell size was 12.7 microns. Large differences exist in mean cell size between individuals, but no correlation was found with age, diabetes or cataract.

The objective assessment of cataract

The objective assessment of cataract is central to any epidemiological or therapeutic study of cataract. The objective methods consist of: 1: A resolution target projection ophthalmoscope (Acuity scope) for the estimation of potential visual acuity. 2: The Oxford Clinical Cataract Classification and Grading System, which records and quantifies the features of the lens that are visible at the slit-lamp microscope. This system is essential since photographic methods cannot define the morphology of cataract. 3: Two photographic methods; slit-lamp photography and retro-illumination photography are needed to give a comprehensive statement about the amount of cataract. The negatives are measured by computerised image analysis systems.

Perinuclear lens retrodots: a role for ascorbate in cataractogenesis

Lens retrodots are round, oblong, or oval features in the perinuclear zone of the adult lens after the fifth decade of life and associated with cataract. Retrodots were found in 47 out of 121 eyes with cataract (39%) in the present series. They show birefringence in vivo and in vitro, and chemical studies suggest that they contain calcium oxalate. It is proposed that ascorbic acid, which is abundant in the normal human lens, is the most likely source for this oxalate. Ascorbic acid is thought to have a protective role against oxidative stress in the lens and other parts of the eye, and its level is known to be reduced in senile cataract. The presence of the retrodots may identify lenses which have been exposed to oxidative stress and are less capable of resisting oxidative damage.

Short-chain carboxylic acids, a new class of teratogens: studies of potential biochemical mechanisms

Certain short-chain carboxylic acids (SCCA) appear to share a common teratogenic potential, although the structural requirements for activity remain obscure. By using a whole rat embryo culture model system, several biochemical processes have been examined, either as potential initial sites of teratogenic action or as early steps in the pathway to malformation. Valproate, methoxyacetate, and butyrate were the prototype SCCA examined. Measurement of [14C]glucose utilization and lactate production confirmed that energy production by the early organogenesis embryo is predominantly from glycolysis. While the positive control agent, iodoacetate, caused a significant inhibition of lactate production, none of the SCCA affected this process or glucose utilization at teratogenic concentrations. Valproate did not influence embryonic acetyl CoA levels, in marked contrast to the reported response of adult liver, the other major target of valproate toxicity. Pinocytosis by the visceral yolk sac (VYS) was measured by the uptake of [125I]polyvinylpyrrolidone. This process ultimately supplies the embryo with amino-acids and is essential for normal development. SCCA induce morphological abnormalities of the VYS in embryo culture. Pinocytosis was slightly reduced by valporate, but not the other SCCA. However, comparison with the action of an antiserum, for which inhibition of pinocytosis is the initial teratogenic insult, suggests that this is not the mechanism for valproate. Incorporation of [3H]thymidine into embryo or yolk sac was not affected after 3 hr of SCCA exposure, but there was a marked effect of the positive control, hydroxyurea. This suggests that DNA synthesis is not directly influenced by SCCA.(ABSTRACT TRUNCATED AT 250 WORDS)

The Oxford Clinical Cataract Classification and Grading System

A composite slit-lamp based system for the clinical classification and grading of cataract is described. Cataract features are classified morphologically, and individual features are graded by comparison with standard diagrams mounted adjacent to the slit-lamp. Attention has been paid to relevant aspects of measurement theory, with equal interval steps between the grades. The image degrading effect of the cataract is assessed using a 'resolution target projection ophthalmoscope'. The method may be used in conjunction with photographic and image analysing techniques.

Clonal origins of lymphoproliferative disease induced by Epstein-Barr virus

Analysis of immunoglobulin gene rearrangements in 16 B-cell lineages clonally propagated from two mononucleosis patients supported the notion that mononucleosis is a polyclonal B-lymphoproliferative disorder. Three of seven cell clones from a patient with a fatal B lymphoma revealed the same pattern of immunoglobulin gene rearrangement, indicating that this patient's disease was oligoclonal. The three similar clones were propagated from two sites (blood and spleen), indicating that they represent a metastatic cell lineage which arose during the patient's fatal B lymphoproliferation.