Drusen and RPE atrophy automated quantification by optical coherence tomography in an elderly population

PURPOSE

Correlate OCT-derived measures of drusen and retinal pigment epithelium (RPE) atrophy areas (RAs) with demographic features in an elderly population.

PATIENTS AND METHODS

Subjects aged 50 years and older underwent Cirrus OCT scanning. Drusen area and volume were obtained from the macula within a central circle (CC) of 3 mm and a surrounding perifoveal ring (PR) of 3-5 mm, using the RPE analysis software (6.0). RA measurements were generated for the 6 × 6 mm(2) retinal area. Gender, age, smoking status, and systolic blood pressure (SBP) were considered.

RESULTS

A total of 434 eyes were included. RA was larger in women (0.63±0.16 vs 0.26±0.08 mm(2), P=0.05) and with increasing age. The PR drusen area increased with increasing age (P<0.001), whereas the CC drusen area remained stable after the age of 70 years (0.25±0.06 mm(2) for ages 70-79 years and 0.25±0.07 mm(2) for ages >80 years). Drusen volume in the CC was smaller after the age of 80 years (0.009±0.003 mm(3)) compared with the 70- to 79-year-old group (0.02±0.008 mm(3)). Drusen measurements were similar between smokers and nonsmokers, but the PR drusen area (0.29 mm(2), P=0.05) and volume (0.40 mm(3), P=0.005) were correlated with years smoked. RA (0.24 mm(2), P=0.10), PR drusen area (0.29 mm(2), P=0.05), and volume (0.40 mm(3), P=0.005) were found to be directly associated with SBP. There was a high correlation between the eyes of the same subject.

CONCLUSION

OCT-based automated algorithms can be used to analyze and describe drusen and geographic atrophy burden in such population-based studies of elderly patients.

Genetic susceptibility and mechanisms for refractive error

Refractive errors, myopia and hyperopia, are the most common causes of visual impairment worldwide. Recent advances in genetics have been utilized to identify a wealth of genetic loci believed to contain susceptibility genes for refractive error (RE). The current genetic evidence confirms that RE is influenced by both common and rare variants with a significant environmental component. These studies argue that only by combining genetic and environmental knowledge with in vivo measurements of biological states will it be possible to understand the underlying biology of RE that will lead to novel therapeutic targets and accurate genetic predictions.

Transcriptome analysis and molecular signature of human retinal pigment epithelium

Retinal pigment epithelium (RPE) is a polarized cell layer critical for photoreceptor function and survival. The unique physiology and relationship to the photoreceptors make the RPE a critical determinant of human vision. Therefore, we performed a global expression profiling of native and cultured human fetal and adult RPE and determined a set of highly expressed ‘signature’ genes by comparing the observed RPE gene profiles to the Novartis expression database (SymAtlas: http://wombat.gnf.org/index.html) of 78 tissues. Using stringent selection criteria of at least 10-fold higher expression in three distinct preparations, we identified 154 RPE signature genes, which were validated by qRT-PCR analysis in RPE and in an independent set of 11 tissues. Several of the highly expressed signature genes encode proteins involved in visual cycle, melanogenesis and cell adhesion and Gene ontology analysis enabled the assignment of RPE signature genes to epithelial channels and transporters (ClCN4, BEST1, SLCA20) or matrix remodeling (TIMP3, COL8A2). Fifteen RPE signature genes were associated with known ophthalmic diseases, and 25 others were mapped to regions of disease loci. An evaluation of the RPE signature genes in a recently completed AMD genomewide association (GWA) data set revealed that TIMP3, GRAMD3, PITPNA and CHRNA3 signature genes may have potential roles in AMD pathogenesis and deserve further examination. We propose that RPE signature genes are excellent candidates for retinal diseases and for physiological investigations (e.g. dopachrome tautomerase in melanogenesis). The RPE signature gene set should allow the validation of RPE-like cells derived from human embryonic or induced pluripotent stem cells for cell-based therapies of degenerative retinal diseases.

A novel approach to search for identity by descent in small samples of patients and controls from the same mendelian breeding unit: a pilot study on myopia

Autosomal dominant high myopia, a genetic disorder already mapped to region 18p11.31, is common in Carloforte (Sardinia, Italy), an isolated village of 8,000 inhabitants descending from a founder group of 300 in the early 1700s. Fifteen myopic propositi and 36 normal controls were selected for not having ancestors in common at least up to the grandparental generation, although still descendants of the original founders. All subjects were genotyped for 14 markers located on autosome 18 at a resolution of about 10 cM. Allelic distributions were found to be similar at all tested loci in propositi and controls, except for the candidate marker D18S63 known to segregate in close linkage association with high myopia. In particular, the frequency of allele 85 among the propositi was almost double that of the controls (Fisher's exact test, p = 0.037). The association is more striking when the frequency of the genotype 85/85 in the two groups is compared (Fisher's exact test, p = 0.005). This conclusion was further evaluated through a bootstrap analysis by computing the overall probability of the observed data under the null hypothesis (i.e. no difference between the two groups in frequency distributions for the chromosome 18 markers). Again, marker D18S63 was found to have a sample probability lower than 0.004, which is significant at the 0.05 level after correcting for simultaneous testing of multiple loci. The study demonstrates the efficiency of our novel strategy to detect identity by descent (IBD) in small numbers of patients and controls when they are both part of well-defined Mendelian breeding units (MBUs). The iterative application of our strategy in separate MBUs is expected to become the method of choice to evaluate the ever-growing number of reported associations between candidate genes and multifactorial traits and diseases.

Lens changes in hereditary hyperferritinemia-cataract syndrome

PURPOSE

To provide detailed description and illustration of the lens changes found in hereditary hyperferritinemia-cataract syndrome, a newly reported autosomal dominant condition.

METHODS

Observational case reports. A 19-year-old man was referred for evaluation of possible hereditary hyperferritinemia-cataract syndrome. His serum ferritin level was increased at 1291 microg/L during a routine screening examination. Genetic analysis revealed mutation G51C on chromosome 19, predicting an altered iron response element in L-ferritin mRNA. Subsequent evaluation of his 46-year-old father revealed similar findings.

RESULTS

Multiple breadcrumb-like nuclear and cortical lens opacities were seen in this father-son pair. These cases represent the first detailed description and illustration of hereditary hyperferritinemia-cataract syndrome cataracts in the ophthalmic literature.

CONCLUSION

Hereditary hyperferritinemia-cataract syndrome can be associated with distinct breadcrumb-like lens opacities. Recognition of these characteristic cataracts may aid identification and study of patients with this unusual disorder and provide insight into mechanisms of cataract formation.

A mouse model of galactose-induced cataracts

Galactokinase (GK; EC 2.7.1.6) is the first enzyme in the metabolism of galactose. In humans, GK deficiency results in congenital cataracts due to an accumulation of galactitol within the lens. In an attempt to make a galactosemic animal model, we cloned the mouse GK gene (Glk1) and disrupted it by gene targeting. As expected, galactose was very poorly metabolized in GK-deficient mice. In addition, both galactose and galactitol accumulated in tissues of GK-deficient mice. Surprisingly, the GK-deficient animals did not form cataracts even when fed a high galactose diet. However, the introduction of a human aldose reductase transgene into a GK-deficient background resulted in cataract formation within the first postnatal day. This mouse represents the first mouse model for congenital galactosemic cataract.

Additional copies of the proteolipid protein gene causing Pelizaeus-Merzbacher disease arise by separate integration into the X chromosome

The proteolipid protein gene (PLP) is normally present at chromosome Xq22. Mutations and duplications of this gene are associated with Pelizaeus-Merzbacher disease (PMD). Here we describe two new families in which males affected with PMD were found to have a copy of PLP on the short arm of the X chromosome, in addition to a normal copy on Xq22. In the first family, the extra copy was first detected by the presence of heterozygosity of the AhaII dimorphism within the PLP gene. The results of FISH analysis showed an additional copy of PLP in Xp22.1, although no chromosomal rearrangements could be detected by standard karyotype analysis. Another three affected males from the family had similar findings. In a second unrelated family with signs of PMD, cytogenetic analysis showed a pericentric inversion of the X chromosome. In the inv(X) carried by several affected family members, FISH showed PLP signals at Xp11.4 and Xq22. A third family has previously been reported, in which affected members had an extra copy of the PLP gene detected at Xq26 in a chromosome with an otherwise normal banding pattern. The identification of three separate families in which PLP is duplicated at a noncontiguous site suggests that such duplications could be a relatively common but previously undetected cause of genetic disorders.

Novel mutations in 13 probands with galactokinase deficiency

Galactokinase is an essential enzyme in the metabolism of galactose. Patients with deficiencies in galactokinase exhibit early-onset cataracts. We examined the sequence of the human galactokinase gene (GK1) from 13 patients exhibiting galactokinase deficiency and identified 12 novel mutations. One of the mutations occurred in six of the 13 probands examined, and the remaining 11 were unique mutations. Expression of each of the mutant GK1 genes in Xenopus oocytes resulted in very low galactokinase activity levels. These results provide important information regarding the types of GK1 mutations that occur in the human population.

Abnormal eye development associated with Cat4a, a dominant mouse cataract mutation on chromosome 8

PURPOSE

Cat4a, one of four mutant alleles at the mouse Cat4 locus, causes central corneal opacity and anterior polar cataract in heterozygotes and microphthalmia in homozygotes. The Cat4 locus has been mapped to chromosome 8, 31 cM from the centromere. In this study ocular development of Cat4a mutant mice was investigated to characterize the defects in eye morphogenesis.

METHODS

Serial sections from eyes of wild-type, heterozygous, and homozygous littermates were examined by means of light microscopy at selected intervals from embryonic day 11 to postnatal day 1. Eyes of adult heterozygous and homozygous mice also were evaluated histologically.

RESULTS

Failure of separation of the lens vesicle from the surface ectoderm was the earliest structural defect observed. In heterozygous embryos, the abnormality was limited to persistent connection of the anterior pole of the lens to the cornea. Adult heterozygotes had defects in the central corneal stroma and endothelium and anterior polar cataracts with or without keratolenticular adhesion. In homozygous embryos, the persistent connection of lens to surface ectoderm was associated with aborted lens development, failure of closure of the optic fissure, and impairment of growth of the eyecup. Microphthalmic eyes of adult homozygous mice had a poorly developed cornea, and the anterior chamber and vitreous compartment were absent. An extensively folded retina and remnants of a degenerated lens filled the interior of the globe.

CONCLUSIONS

A developmental defect inhibits separation of the lens vesicle from surface ectoderm in mice heterozygous or homozygous for the Cat4a mutation. In homozygotes subsequent lens and eye morphogenesis are also severely affected. Cat4a shows phenotypical similarity to several other independent mouse mutations including Small eye, a mutation of the Pax6 gene. Cat4 may be one of several genes involved in a common developmental path and may be part of the Pax6-regulated gene cascade governing eye morphogenesis.

The mouse Cat4 locus maps to chromosome 8 and mutants express lens-corneal adhesion

Cat4 is the second largest allelism group in the collection of mouse dominant eye mutations recovered in Neuherberg and carriers express anterior polar cataract, central corneal opacity, and lens-corneal adhesions. We have mapped the Cat4 locus of the mouse to central Chromosome (Chr) 8 at position cM 31. Histological characterization of Cat4(a) heterozygotes and homozygotes indicates failure of separation of the lens vesicle from the surface ectoderm. Human anterior segment ocular dysgenesis (ASOD) is autosomal dominant, carriers express an eye phenotype similar to that of Cat4(a) carriers, and it has been mapped to a region of 4q homologous to mouse central Chr 8. Thus, on the basis of phenotype and map position, Cat4 may be a mouse model of human ASOD. The genes Junb, Jund1, Mel, and Zfp42 are discussed as possible candidates for Cat4.

Genetic mapping of a mouse ocular malformation locus, Tcm, to chromosome 4

The Tcm mutation in the mouse is an autosomal dominant ocular malformation manifesting as microphthalmia, iris dysplasia, cataract, and coloboma. As a first step to cloning the Tcm gene, we report the localization of the Tcm mutation with respect to known microsatellite markers. Backcross progeny carrying the Tcm mutation were produced by mating Tcm/+ heterozygous mice to normal C57BL/6 partners. Genomic DNA from each mouse was subjected to PCR analysis to identify simple sequence length polymorphisms. Our results locate Tcm to Chr 4 and suggest candidate genes responsible for the Tcm phenotype. Finally, ocular histopathology was done in 3-week-old animals to define the extent of the malformation.

Fine structure of the human galactokinase GALK1 gene

Defects in the human GALK1 gene result in galactokinase deficiency and cataract formation. We have isolated this gene and established its structural organization. The gene contains 8 exons and spans approximately 7.3 kb of genomic DNA. The GALK1 promoter was localized and found to have many features in common with other housekeeping genes, including high GC content, several copies of the binding site for the Sp1 transcription factor, and the absence of TATA-box and CCAAT-box motifs typically present in eukaryotic Pol II promoters. Analysis by 5'-RACE PCR indicates that the GALK1 mRNA is heterogeneous at the 5' terminus, with transcription sites occurring at many locations between 21 and 61 bp upstream of the ATG start site of the coding region. In vitro translation experiments of the GALK1 cDNA indicate that the protein is cytosolic and not associated with the endoplasmic reticulum membrane.

Mouse galactokinase: isolation, characterization, and location on chromosome 11

Elevated galactose levels can be caused by several enzyme defects, one of which is galactokinase. Galactokinase deficiency cause congenital cataracts during infancy and presenile cataracts in the adult population. We have isolated the mouse cDNA for galactokinase, which shares extensive amino acid sequence homology, 88% identity, with a recently cloned human galactokinase. It is expressed in all tissues examined. In an interspecific backcross analysis galactokinase maps to the distal region of mouse chromosome 11, a region that is homologous to human chromosome 17q22-25. The availability of the mouse gene provides an opportunity to make a knockout model for galactokinase deficiency.

Mapping of the 75-kDa inositol polyphosphate-5-phosphatase (Inpp5b) to distal mouse chromosome 4 and its exclusion as a candidate gene for dysgenetic lens

We have determined the chromosomal localization of the murine gene encoding a 75-kDa inositol polyphosphate-5-phosphatase (Inpp5b). Using two independent approaches, fluorescence in situ hybridization and interspecific backcross analysis, we show that Inpp5b maps to distal mouse Chromosome 4. This map position is within the conserved linkage group corresponding to the short arm of human Chromosome 1, where the human homologue, INPP5B, has been shown to map previously. The position of Inpp5b on mouse Chromosome 4 is in the vicinity of the mouse developmental mutation dysgenetic lens (dyl). However, using a genetic approach, we show that Inpp5b maps distal to dyl on mouse Chromosome 4.

Comparison of the enzymatic activities of human galactokinase GALK1 and a related human galactokinase protein GK2

The GALK1 cDNA encoding human galactokinase was recently cloned and its cognate GALK1 gene shown to be involved in galactokinase deficient galactosemia. Previously, a separate human galactokinase cDNA, GK2, was cloned by complementation of a galactokinase deficient yeast mutant; however, the galactokinase activity of GK2 was not demonstrated in mammalian cells. To compare the relative galactokinase activity of GALK1 and GK2, their corresponding cDNAs were expressed in COS cells. Northern blot analysis indicated that both cDNAs were transcribed into mRNA transcripts of the expected size; however, only the GALK1 cDNA produced high levels of galactokinase activity. This result would suggest that GALK1 is the major enzyme for galactose metabolism while the role of GK2 remains uncertain.

Cloning of the galactokinase cDNA and identification of mutations in two families with cataracts

Galactokinase is an essential enzyme for the metabolism of galactose and its deficiency causes congenital cataracts during infancy and presenile cataracts in the adult population. We have cloned the human galactokinase cDNA, which maps to chromosome 17q24, and show that the isolated cDNA expresses galactokinase activity in bacteria and mammalian cells. We also describe two different mutations in this gene in unrelated families with galactokinase deficiency and cataracts. The availability of the cloned galactokinase gene provides an important reference to identify mutations in patients with galactokinase deficiency and cataracts.

Mapping of the X-linked cataract (Xcat) mutation, the gene implicated in the Nance Horan syndrome, on the mouse X chromosome

The Xcat mutation in the mouse, an X-linked inherited disorder, is characterized by the congenital onset of cataracts. The cataracts have morphologies similar to those of cataracts found in the human Nance Horan (X-linked cataract dental) syndrome, suggesting that Xcat is an animal model for Nance Horan. The Xcat mutation provides an opportunity to investigate, at the molecular level, the pathogenesis of cataract. As a first step to cloning the Xcat gene, we report the localization of the Xcat mutation with respect to known molecular markers on the mouse X chromosome. Back-cross progeny carrying the Xcat mutation were obtained from an interspecific cross. Genomic DNA from each mouse was subjected to Southern and PCR analysis to identify restriction fragment length polymorphisms and simple sequence length polymorphisms, respectively. Our results refine the location of Xcat to a 2-cM region, eliminate several genes from consideration as the Xcat mutation, identify molecular probes tightly linked with Xcat, and suggest candidate genes responsible for the Xcat phenotype.

Lens development in a dominant X-linked congenital cataract of the mouse

Xcat is a recently identified mouse mutation causing X-linked dominant congenital cataract. The mutation is of particular interest as a possible animal model for the human X-linked cataract syndrome. Using light microscopy, we examined the histological changes of mutant lenses at selected intervals between embryonic (E) day 14 and postnatal (P) day 21. At E14, primary fiber formation completely fills the former lens vesicle in both normal and mutant mice, but in affected animals the primary fibers are irregularly arranged and show small foci of cellular disintegration. Progressive degeneration of primary fibers occurs from E15 to E18 and, during late gestation, secondary lens fibers also begin to degenerate. The lens epithelium and newly differentiated fibers, however, show no evident abnormality. Postnatally, most of the lens substance becomes amorphous; the cataractous process terminates in rupture of the posterior lens capsule by P21. Analysis of crystallin and cytoskeletal proteins of postnatal cataractous lenses revealed no significant abnormalities when compared to normal lenses. The observed sequence of histological changes indicates that the Xcat mutation affects the differentiation of lens fiber cells at some point after their initial elongation.

Cytogenetic and molecular investigation of a balanced Xq13q translocation in a patient with retinoblastoma

We report on a 4-year-old girl with retinoblastoma and de novo balanced translocation [46,X,t (X;13) (q23;q13)]. Unilateral retinoblastoma was discovered at age 9 months along with developmental delay and several manifestations of Turner syndrome. Chromosome studies showed an X/13 translocation and an X inactivation pattern showing the translocated X chromosome active in all 50 cells examined. Standard Southern blot analysis and pulsed field gel electrophoresis using a 3.8 kb EcoR1 fragment of the cDNA probe to the 3' end of the RB1 locus demonstrated a normal genomic pattern. The results of the cytogenetic and molecular analysis suggests that the RB1 locus has not been disrupted by the chromosome rearrangement. This case is the fifth report of an X/13 translocation associated with a retinoblastoma.

Nance-Horan syndrome: localization within the region Xp21.1-Xp22.3 by linkage analysis

Nance-Horan Syndrome (NHS) or X-linked cataract-dental syndrome (MIM 302350) is a disease of unknown pathogenesis characterized by congenital cataracts and dental anomalies. We performed linkage analysis in three kindreds with NHS by using six RFLP markers between Xp11.3 and Xp22.3. Close linkage was found between NHS and polymorphic loci DXS43 (theta = 0 with lod score 2.89), DXS41 (theta = 0 with lod score 3.44), and DXS67 (theta = 0 with lod score 2.74), defined by probes pD2, p99-6, and pB24, respectively. Recombinations were found with the marker loci DXS84 (theta = .04 with lod score 4.13), DXS143 (theta = .06 with lod score 3.11) and DXS7 (theta = .09 with lod score 1.68). Multipoint linkage analysis determined the NHS locus to be linked completely to DXS41 (lod score = 7.07). Our linkage results, combined with analysis of Xp interstitial deletions, suggest that the NHS locus is located within or close to the Xp22.1-Xp22.2 region.

Ribosomal RNA gene sequences and hominoid phylogeny

Sequences totaling 3,500 bases from the 28S rRNA gene and from one of the ribosomal internal transcribed spacers (ITS1) have been determined for human, chimpanzee (Pan troglodytes), gorilla (Gorilla gorilla), and orangutan (Pongo pygmaeus). Analyses of the rRNA alignments show (1) a clustering of substitutions in the "variable regions" of the 28S gene, (2) a 1.5-3-fold increase in divergence in the transcribed spacer over that in the exon, and (3) that human and chimpanzee are the most closely related pair, in agreement with the results of Miyamoto et al., Sibley and Ahlquist, and Caccone and Powell.

Sequence and structure correlation of human ribosomal transcribed spacers

We report the sequences of the transcribed spacers of human rRNA that now allow us to piece together the entire primary transcript sequence of approximately 13.3 x 10(3) base-pairs. Comparison of transcribed spacer sequences with those of variable regions of rRNA and with those of the non-transcribed spacers supports the hypothesis that the variable regions are descended from transcribed spacers. Nucleotide sequence-derived secondary structures for the 5' external transcribed spacer and for internal transcribed spacers 1 and 2 match both the sizes and shapes of the structures that were visualized 15 years ago on electron micrographs. Parts of these structures are conserved in mammals and may be related to transcript processing.

Mapping X-linked ophthalmic diseases. IV. Provisional assignment of the locus for X-linked congenital cataracts and microcornea (the Nance-Horan syndrome) to Xp22.2-p22.3

The Nance-Horan syndrome (NHS) is an infrequent X-linked disorder typified by dense congenital central cataracts, microcornea, anteverted and simplex pinnae, brachymetacarpalia, and numerous dental anomalies. The regional location of the genetic mutation causing NHS is unknown. The authors applied the modern molecular techniques of analysis of restriction fragment length polymorphisms to five multigenerational kindreds in which NHS segregated. Provisional linkage is established to two DNA markers--DXS143 at Xp22.3-p22.2 and DXS43 at Xp22.2. Regional localization of NHS will provide potential antenatal diagnosis in families at risk for the disease and will enhance understanding of the multifaceted genetic defects.

Galactose and cataract

Galactosemia is a disorder caused by a deficiency of any one of three possible enzymes involved in the metabolism of galactose: galactokinase, transferase or epimerase. Any single deficient enzyme can result in cataract through the accumulation of galactitol in the lens. The ophthalmologist may play an important role in this disease, since early recognition of cataract development followed by the initiation of a galactose-free diet may lead to clearing of lenticular opacities. The clinical and laboratory findings that distinguish the three enzyme deficiency disorders of galactosemia are discussed. The biochemical genetics of each enzyme also are reviewed, along with the recent evidence linking heterozygous galactokinase deficiency and presenile cataract.

Cataracts in patients heterozygous for galactokinase deficiency

The role of heterozygous galactokinase deficiency in the development of presenile cataracts is presently undetermined. Erythrocyte galactokinase activity was measured from 95 normal Caucasian subjects and from 39 Caucasian patients who had developed idiopathic bilateral cataracts between ages 20 and 55. The diagnosis of heterozygous galactokinase deficiency was based on the following criteria: galactokinase activity more than 2.0 SD below the control population mean; when available, familial evidence for heterozygous galactokinase activity was used as additional evidence. Three of 39 patients (1/13) with cataracts were found to be carriers of the galactokinase deficiency allele (P less than 0.001). Two heterozygotes had high dietary galactose intake suggesting a possible relationship between a high galactose diet and cataract formation. Dietary information was unavailable for the third heterozygote. We conclude that there is a high prevalence of heterozygous galactokinase deficiency existing in patients less than 55 yr of age with cataracts, and recommend that adults at risk restrict their consumption of dairy products.

Purification of human galactokinase and evidence for its existence as a monomer form

A procedure for preparing a highly purified galactokinase (ATP:D-galactose 1-phosphotransferase, EC 2.7.1.6) from human erythrocytes and placenta is described, involving DEAE-Sephacel, ammonium sulfate fractionation, gel-filtration and a subsequent chromatography step on Blue Sepharose CL-6B. The final chromatography step yields a homogeneous preparation of high specific activity. The subunit molecular weight was determined to be 38 000 for both placental and erythrocyte galactokinases. Both active preparations of the native enzyme eluted from a gel filtration column gave a molecular weight of 37 000-38 000, thus suggesting the enzyme to be present in monomeric form. The isoelectric points for both crude and their respective purified enzymes was determined to be at pH 5.7. This method for purifying human galactokinase from placenta and erythrocytes represents a significant improvement over that previously reported and contradicts past evidence for the enzyme existing as a dimer.

Isoelectric-focusing of galactokinase in lens and other tissues

Thin-layer isoelectric focusing was used to investigate galactokinase in lenses from humans, cows, rats, rabbits and also in other tissues (red cells, liver, kidney, brain, placenta) from these species. In each case the enzyme activity was present as a single isozyme. The isoelectric point was the same in lens, red cell and other tissues of the same species, but differed from species to species. Post-translational modification due to deamidation was not detected in the lens or red cell from these species. Galactokinase activities in whole tissue extract were determined in different tissues of the various species. There were wide variations in activity. In the adult human lens, both normal and cataractous, it was low. The findings indicate that isoelectric focusing of RBC galactokinase combined with specific enzyme staining allows one to monitor lens galactokinase in patients with cataracts.

Optic neuropathy associated with vitamin B12 deficiency

A 17-year-old boy with vitamin B12 deficiency that occurred after a small bowel resection developed bilateral centrocecal scotomas during folic acid therapy and improved on therapy including vitamin B complex.