A comprehensive,sensitive and economical approach for the detection of mutations in the <Emphasis Type="Italic">RB1</Emphasis> gene in retinoblastoma

Retinoblastoma (Rb) is the most common primary intraocular malignancy in children. It is brought about by the mutational inactivation of both alleles of RB1 gene in the developing retina. To identify the RB1 mutations, we analysed 74 retinoblastoma patients by screening the exons and the promoter region of RB1. The strategy used was to detect large deletions/duplications by fluorescent quantitative multiplex PCR; small deletions/insertions by fluorescent genotyping of RB1 alleles, and point mutations by PCR-RFLP and sequencing. Genomic DNA from the peripheral blood leucocytes of 74 Rb patients (53 with bilateral Rb, 21 with unilateral Rb; 4 familial cases) was screened for mutations. Recurrent mutations were identified in five patients with bilateral Rb, large deletions in 11 patients (nine with bilateral Rb and two with unilateral Rb), small deletions/insertions were found in 12 patients all with bilateral Rb, and point mutations in 26 patients (14 nonsense, six splice site, five substitution and one silent change). Three mutations were associated with variable expressivity of the disease in different family members. Using this method, the detection rates achieved in patients with bilateral Rb were 44/53 (83%) and with unilateral Rb, 5/21 (23.8%). This approach may be feasible for clinical genetic testing and counselling of patients.     

儿童过敏性结膜炎与变应性鼻炎的相关性及鼻眼联合防治效果分析

目的：探讨儿童过敏性结膜炎与变应性鼻炎的相关性研究及鼻眼联合防治的临床效果。方法：回顾性分析300 例儿童过敏性 结膜炎与310 例儿童变应性鼻炎患者的临床资料,对儿童过敏性结膜炎与变应性鼻炎的相关性进行分析后将所有患儿随机均分 为对照组与观察组,对照组采用常规点眼的方法进行治疗,观察组则采用鼻朗喷鼻联合人工泪液点眼进行治疗。比较两组临床疗 效及不良反应情况。结果：（1）300 例过敏性结膜炎患儿中,50 例（16.67%）并发变应性鼻炎;310 例变应性鼻炎患儿中,59 例 （19.03%）并发过敏性结膜炎（P＞0.05）;（2）109 例同时并发两种疾病患儿中,均进行眼结膜与鼻粘膜的刮片检查嗜酸性粒细胞, 其中60 例（55.05%）结膜刮片与67 例（61.47%）鼻粘膜刮片检测到嗜酸性粒细胞（P＞0.05）;（3）两组治疗前后BUT 及角膜荧光素 染色评分、症状评分、临床总有效率比较差异明显（P＜0.05）。结论：儿童过敏性结膜炎与变应性鼻炎具有一定的相关性;鼻朗喷鼻 联合人工泪液点眼治疗儿童合并变应性鼻炎的临床疗效显著。     

Growth in paediatric Crohn's disease

Growth failure (GF) is one of the major complications affecting children with inflammatory bowel disease. The faltering is temporary in 40-50% of cases and prolonged in 10-20% in Crohn's disease (CD). Such failure is rare in children with ulcerative colitis (5%). This complication is often associated with retarded bone development and delayed onset of sexual maturation. The delayed linear growth has a variety of causes including insufficient intake due to anorexia and the inflammatory process with increased energy and protein expenditure. Other factors are increased intestinal loss, secondary hypopituitarism and treatment with steroids. Therapeutic strategies of CD in children have changed this last decade by introducing new therapeutic agents such as topic steroids, immunosuppressors, anti-TNF (antibody and notably in children enteral nutrition which has shown its efficacy in inducing remissions of active CD, restoring nutritional status and stimulation of linear growth. The results of a recent prospective multicentric study over 2 years in 82 CD show that severe GF (-2 SD) is initially present in 15% (n = 12), among them 11 remain < -2SD after 2 years of follow-up. Six patients who were on the normal range initially increased their GF during the follow-up (< -2SD) (total 21% < -2SD (n = 17) at 2 years). At inclusion in this group there was no difference in growth velocity, used of steroids, enteral nutrition or severity of CD as compared to the group with no GF. It suggests that new treatment strategy should be developed in the future for this specific complication of paediatric CD.     

Completion total thyroidectomy in children with differentiated thyroid cancer

INTRODUCTION: The optimal surgical treatment of children with differentiated thyroid cancer remains an important point of discussion. Especially the need for completion operation is questioned in young patients. Our objective was to examine the rate of residual neoplastic disease after non radical initial operation. MATERIAL AND METHODS: From the 235 children diagnosed with differentiated thyroid cancer, 131 (56%) needed completion operation due to incomplete primary surgery. Completion operation involved thyroid bed, lymph nodes or both respectively in 91 (39%), 13 (6%) and 27 (11%) cases. Risk factors responsible for residual disease were evaluated by means of logistic regression analysis. RESULTS: Residual disease was detected in 46 (35%) of reoperated children (25% in thyroid bed and 85% in lymph node of lateral neck compartment). Sex and age did not influence the risk of residual disease in thyroid bed or lymph nodes. Papillary type of cancer and multifocality increased risk of residual disease in thyroid bed respectively by the factor of 15 (95% CI: 2-125) and 2.3 (95% CI: 1.2-4.4). Infiltration of thyroid capsule did not correlate with the risk of residual disease. Lymph node metastases in primary operation increased risk of residual disease by the factor of 16 (95% CI: 1.2-245). Histopathology, multifocality of primary tumour or infiltration of lymph node capsule did not influence the risk of residual disease in lymph nodes of lateral neck compartment. CONCLUSIONS: In children with differentiated thyroid cancer residual disease is diagnosed in about 1/3 of non radically operated cases. This high incidence justifies completion operations. The risk of residual disease is significantly increased in papillary thyroid cancer, multifocal tumours and cases with lymph node metastases.     

Prevention of blindness by screening for diabetic retinopathy: a quantitative assessment.

Diabetic retinopathy is an important cause of blindness in the Western World. A review of the randomised trials of laser photocoagulation of the retina as a method of preventing blindness from this disorder showed that this treatment is very effective, reducing the risk of blindness by 61% in a treated eye. As only one eye is needed for sight the reduction in blindness in a population will be greater than 61% because the effect of treatment in one eye is not always identical with the effect in the other eye. For analysis this reduction was taken as 73%, representing the average of the minimum and maximum estimates (61% and 85%). The effectiveness of this treatment suggests that there is the potential for a national screening programme to bring about a major reduction in blindness from this cause. A quantitative assessment of the effect of screening indicated that a programme in which patients with diabetes mellitus are systematically referred to ophthalmic opticians for a retinal examination could detect 88% of all diabetics with serious retinopathy and that 87% of these cases would be treatable. Screening and early treatment of retinopathy would prevent deterioration of visual acuity and could reduce the risk of blindness due to diabetic retinopathy by an estimated 56% (0.73 X 0.88 X 0.87). The findings suggest that an effectively managed community based screening programme encompassing detection, referral, treatment, and follow up would prevent about 260 new cases of blindness in diabetics under the age of 70 each year in England and Wales. This would represent over 10% of all cases of blindness in adults in this age group.     

Pathogenesis of thyroid eye disease - does autoimmunity against the TSH receptor explain all cases?

Thyroid associated ophthalmopathy, or thyroid eye disease (TED), is a complex inflammatory disorder of the eye that, as its name implies, is usually associated with thyroid disease. Clinical observation supports the existence of three main TED subtypes, namely ocular myopathy, congestive myopathy, and mixed congestive and myopathic ophthalmopathy. Although the precise pathophysiology of TED remains unclear, it is likely to reflect an autoimmune reaction involving sensitised T lymphocytes and autoantibodies directed against a specific orbital or thyroid-and-orbital shared antigen(s). One well-studied candidate in this immune reaction is the thyroid-stimulating hormone receptor (TSHR), which is also expressed in the orbital fibroblast and preadipocyte. Most patients with ophthalmopathy have associated Graves' disease, 10% have Hashimoto's thyroiditis in which the eye changes are often mild and expressed mainly as upper eyelid retraction (UER), and 10% have no apparent associated thyroid disease - so-called "euthyroid Graves' disease". Ophthalmopathy can also occur in some patients with transient thyroiditis, thyroid cancer, and Graves' disease many years after treatment of the hyperthyroidism - situations where TSHR antibodies are not expected to be present, suggesting that the relationship between TSHR antibodies and the eye disorder has not been established for all cases. In our studies of TED we have investigated the nature and significance of antibodies targeting other eye muscle and orbital connective tissue (OCT) antigens, in particular the calcium binding protein calsequestrin (CASQ1) and the orbital fibroblast membrane antigen collagen XIII. Our working hypotheses for the pathogenesis of TED are: i) the initial reaction in the orbit is antibody and T lymphocyte targeting of the TSHR in the OCT compartment, and ii) the associated extra ocular and upper eyelid muscle inflammation reflects either autoimmunity against primary skeletal muscle antigens such as CASQ1 or a secondary, non specific effect of the OCT reactions as proposed by the main proponents of the "TSHR hypothesis". Here, we review the evidence that autoimmunity against the TSHR expressed in the orbit can be implicated in the development of all cases of TED. Although there is a close general correlation between ophthalmopathy and TSHR antibodies there are many exceptions, suggesting that the continued study of the possible role of autoimmunity against calsequestrin and collagen XIII is justified.     

Intraocular tumours

Intraocular tumours may be benign or malignant. The latter are more numerous, and endanger not only vision but life as well. Two of them deserve special attention: melanoma malignum oculi in adults and retinoblastoma in children. Melanoma malignum may arise from all three areas of the uvea: the iris, the ciliary body and the choroid. The more malignant growths are those which are situated closer to the posterior pole. Histologically the epitheloid cell-type of melanoma is more malignant than those containing only spindle cells. Their treatment depends on the size: in the case of large tumours enucleation is required, while for the smaller ones, radiation therapy can be applied. Retinoblastoma is most common in children of 1-2 years of age. It has familial and sporadic forms. Sixty-seven percent of the inherited-type cases are bilateral. An early symptom in small children is strabismus. A white tissue mass growing into the vitreous is seen on the fundus. A diagnostic feature that can be detected by ultrasound examination is calcification. The tumour may also present intracranially, therefore CT of the skull should be performed in each case. Histologically the tumour contains malignant neuroepithelial cells, which may form a rosette. In the case of large tumours the treatment is enucleation; in bilateral processes the bulbus with the larger mass is removed and the other eye is treated with radiation therapy. In both cases chemotherapy is used according to a prescribed schedule. Metastases to the eye occur most frequently from carcinomas of the breast, lungs or gastrointestinal tract. These are treated with radiotherapy, chemotherapy and hormone therapy. Primary intraocular lymphoma often occurs bilaterally, and may be accompanied by primary lymphoma of the central nervous system (CNS). Some benign tumours are found by chance on routine eye examinations, others due to subjective and objective symptoms.     

The Importance of Networking in Autism Gaze Analysis

Visual scanning of faces in individuals with Autism Spectrum Disorder (ASD) has been intensively studied using eye-tracking technology. However, most of studies have relied on the same analytic approach based on the quantification of fixation time, which may have failed to reveal some important features of the scanning strategies employed by individuals with ASD. In the present study, we examined the scanning of faces in a group of 20 preschoolers with ASD and their typically developing (TD) peers, using both classical fixation time approach and a new developed approach based on transition matrices and network analysis. We found between group differences in the eye region in terms of fixation time, with increased right eye fixation time for the ASD group and increased left eye fixation time for the TD group. Our complementary network approach revealed that the left eye might play the role of an anchor in the scanning strategies of TD children but not in that of children with ASD. In ASD, fixation time on the different facial parts was almost exclusively dependent on exploratory activity. Our study highlights the importance of developing innovative measures that bear the potential of revealing new properties of the scanning strategies employed by individuals with ASD.     

The potential application of iron chelators for the treatment of neurodegenerative diseases

Many forms of neurodegenerative disease, for instance Alzheimer's disease, Parkinson's disease, Friedreich's ataxia, Hallervorden Spatz syndrome and macular degeneration, are associated with elevated levels of redox active metals in the brain and eye. A logical therapeutic approach therefore, is to remove the toxic levels of these metals, copper and iron in particular, by selective chelation. The increased number of iron-selective chelators now available for clinical use has enhanced interest in this type of therapy. This review summarises the recent developments in the design of chelators for treatment of neurodegenerative disease, identifies some of the essential properties for such molecules and suggests some future strategies.     

Insights from animal models on the origins and progression of retinoblastoma

The RB gene was discovered 20 years ago because of its role in the childhood eye cancer retinoblastoma. However, surprisingly little progress was made in defining the role of RB protein in the retina. In the last two years, new models exploiting conditional deletion of the mouse Rb gene have altered this picture radically. These models provide insight into the first Rb function, the cell of origin of retinoblastoma, the window during which Rb acts, distinct cell-specific defenses against Rb loss, the number and type of post-Rb lesions required for transformation, why pediatric tumors exist, the controversial role of the p53 pathway in retinoblastoma, and the reason why the disease is virtually unique to humans. Two years have dramatically improved our understanding of Rb function in the tissue that gave us this important tumor suppressor.     

Clinical Evolution of Paracoccidioidomycosis in 38 Children and Teenagers

Paracoccidioidomycosis (PCM) in children is rare, and its clinical progression is not clearly understood. The admission and post-admission clinical records of 38 children and teenagers aged up to 14 were studied who had been under treatment for 24–30 months. It is a consecutive case series, 17 retrospective and 21 prospective, from 1977 to 2000, admitted before and after 1990, respectively. The main clinical presentations were lymphatic, abdominal and cutaneous involvement, and fever. The alterations which disappeared more slowly were lymphadenomegaly, hepatomegaly, splenomegaly, and osteoarticular pain. Poor intestinal absorption, esophageal varices and splenic calcification were observed before treatment and persisted as sequelae. There was a satisfactory response to initial treatment in 56.7% of cases. Half the patients became asymptomatic in the ninth month of treatment, and 17±8% of cases presented with at least one symptom of the disease after 30 months of treatment. There were five deaths, and treatment failure was frequent and associated in part with the irregular use of antifungal. Treatment with ketoconazole was safe and effective. PCM is a serious systemic disease with slow evolution and high lethality, requiring treatment maintenance for a minimum of 24 months with careful and prolonged follow-up. Studies are necessary to evaluate the efficacy of different antifungals and the ideal treatment length for children with PCM.     

Lymphocyte chromosome survey in 42 patients with retinoblastoma: Effort to detect 13q14 deletion mosaicism

Summary The results of a lymphocyte chromosome survey of retinoblastoma (Rb) patients using a method able to detect a relatively low proportion mosaicism of 13q14 deletion are presented. Three out of 42 Rb patients had abnormal karyotypes; two mosaic cases with the karyotype 46,XY,del(13) (q14.1q14.3)/46,XY and 46,XX,del(13)(q14.1q14.3)/46,XX(the proportions of 13q14-cells, 51% and 9%, respectively), and the other with the karyotype 46,XY,del(13)(q14.1q21.2). All of these three cases had bilateral sporadic Rb. Two mosaic cases had an apparently normal phenotype except for Rb. These data suggest that the frequency of Rb cases with a 13q- cell line in lymphocytes may be greater than that which has been reported.     

Obesity reduction within a generation: the dual roles of prevention and treatment

In 2010, the White House Task Force on Childhood Obesity provided benchmark goals for reducing childhood obesity. We evaluated the balance of prevention and treatment required for achieving Task Force goals in benchmark years 2015, 2020, and 2030. We created a simulation of US birth cohorts (2-19 years) born 2008-2030. For each year, we assumed "old" birth cohorts (part of previous benchmark obesity estimates) would benefit from obesity treatment strategies, and "new" birth cohorts would benefit from obesity prevention strategies. We assessed obesity prevalence that must be achieved through prevention strategies, under varying assumptions of treatment effectiveness. When we assumed a 1% absolute reduction in prevalence through treatment, we found that prevention strategies would need to achieve an obesity prevalence of 12% by 2015, 8% by 2020, and 0.3% by 2030. Because of higher obesity prevalence among minority children, prevention strategies would need to achieve a negative prevalence by 2030, which is implausible. Under more generous assumptions of treatment effectiveness, estimates became positive but remained low. Task Force goals are more difficult to achieve with each benchmark year. Policies must focus on obesity treatment interventions, particularly targeted to racial/ethnic minority children, to make progress in stemming the epidemic.     

儿科呼吸道疾病中肺炎支原体感染的结果分析

目的探讨儿科肺炎支原体（MP）感染特点,辅助临床医师早期诊断,合理用药。方法测定我院一年来2013例儿科呼吸道疾病患儿的肺炎支原体抗体（IgM）。结果2013例呼吸道感染患儿,检出肺炎支原体抗体（IgM）阳性者769例,占38.2%,769例阳性分别表现为肺炎369例（48%）,支气管炎238例（31%）,咽炎92例（12%）,哮喘70例（9%）。其中,肺炎组与各组相比较,具有统计学意义。MP IgM感染的检出率明显高于其他各组（P〈0.01）。结论MP感染是患儿不可忽视的病原体,检测患儿血清MP抗体能够及早诊断,指导治疗。     

The epidemiology and disease burden of children hospitalized for viral infections within the family Flaviviridae in China: A national cross-sectional study

BackgroundViruses of the family Flaviviridae, including Japanese encephalitis virus (JEV), dengue virus (DENV), yellow fever virus (YFV) and hepatitis C virus (HCV), are widely distributed worldwide. JEV, DENV and YFV belong to the genus Flavivirus, whereas HCV belongs to the genus Hepacivirus. Children’s symptoms are usually severe. As a result, rates of hospitalization due to infection with these viruses are high. The epidemiology and disease burden of hospitalized children have rarely been described in detail to date. The objective of this study was to report the general epidemiological characteristics, clinical phenotype, length of stay (LOS), burden of disease, and potential risk factors for hospitalized children infected with JEV, DENV, YFV, or HCV in Chinese pediatric hospitals.MethodologyA cross-sectional study of epidemiology and disease burden of children hospitalized for Flaviviridae virus infections between December 2015 and December 2020 in China was performed. Face sheets of discharge medical records (FSMRs) were collected from 27 tertiary children’s hospitals in the Futang Research Center of Pediatric Development and aggregated into FUTang Update medical REcords (FUTURE). Information on sociodemographic variables, clinical phenotype, and LOS as well as economic burden was included in FSMRs and compared using appropriate statistical tests.FindingsThe study described 490 children aged 0–15 years hospitalized for infections with Flaviviridae viruses. Japanese encephalitis (JE) cases are the highest, accounting for 92.65% of the total hospitalization cases caused by Flaviviridae virus infection. The incidence of JE peaked from July to October with a profile of a high proportion of severe cases (68.06%) and low mortality (0.44%). Rural children had a significantly higher incidence than urban children (91.63%). Most hospitalized dengue cases were reported in 2019 when dengue outbreaks occurred in many provinces of China, although only 14 dengue cases were collected during the study period. Yellow fever (YF) is still an imported disease in China. The hospitalizations for children with hepatitis C (HC) were not high, and mild chronic HC was the main clinical phenotype of patients. Among the four viral infections, JE had the highest disease burden (LOS and expenditure) for hospitalized children.ConclusionFirst, the present study reveals that JE remains the most serious disease due to Flaviviridae virus infection and threatens children’s health in China. Many pediatric patients have severe illnesses, but their mortality rate is lower, suggesting that existing treatment is effective. Both JEV vaccination and infection control of rural children should represent a focus of study. Second, although the dual risks of indigenous epidemics and imports of DENV still exist, the prevalence of DENV in children is generally manageable. Third, YFV currently shows no evidence of an epidemic in China. Finally, the proportion of children with chronic hepatitis C (CHC) is relatively large among hospitalized children diagnosed with HCV. Thus, early and effective intervention should be offered to children infected with HCV to ease the burden of CHC on public health.     

The Effect of Multiple Rounds of Mass Drug Administration on the Association between Ocular Chlamydia trachomatis Infection and Follicular Trachoma in Preschool-Aged Children

Purpose

To examine the relationship between ocular Chlamydia trachomatis infection and follicular trachoma (TF) in children prior to and following multiple rounds of annual mass drug administration (MDA) with azithromycin.

Methodology/principal findings

Thirty-two communities with endemic trachoma in Kongwa District, Tanzania, were offered annual MDA as part of a district-wide trachoma control program. Presence of ocular C. trachomatis infection and TF were assessed in 3,200 randomly sampled children aged five years and younger, who were examined prior to each MDA. Infection was detected using the Amplicor CT/NG assay and TF was identified by clinical examination using the World Health Organization (WHO) simplified grading system. The association between chlamydial infection and TF in children was evaluated at baseline prior to any treatment, and 12 months after each of three annual rounds of mass treatment. Factors associated with infection were examined using generalized estimating equation models.At baseline, the overall prevalence of chlamydial infection and TF was 22% and 31%, respectively. Among children with clinical signs of TF, the proportion of those with infection was 49% prior to treatment and declined to 30% after three MDAs. The odds of infection positivity among children with clinical signs of TF decreased by 26% (OR 0.74, 95% CI 0.65 to 0.84, p = <0.01) with each MDA, after adjusting for age. For children aged under one year, who did not receive treatment, the relationship was unchanged.

Conclusions/significance

The association between ocular C. trachomatis infection and TF weakened in children with each MDA, as both infection and clinical disease prevalence declined. However, there was still a significant proportion of TF cases with infection after three rounds of MDA. New strategies are needed to assess this residual infection for optimal treatment distribution.     

Cryptococcosis in Colombian children and literature review

Cryptococcosis is reported in adults and is often acquired immune deficiency syndrome (AIDS)-associated; however, its frequency in children is low. Based on the National Survey on Cryptococcosis conducted in Colombia, an epidemiological and clinical analysis was performed on cases of the disease observed in children less than 16 years old between 1993-2010. We found 41 affected children (2.6% prevalence) from the 1,578 surveys received. The country mean annual incidence rate was 0.017 cases/100,000 children under 16 years, while in Norte de Santander the incidence rate was 0.122 cases/100,000 (p < 0.0001). The average age of infected children was 8.4 and 58.5% were male. In 46.3% of cases, a risk factor was not identified, while 24.4% had AIDS. The most frequent clinical manifestations were headache (78.1%), fever (68.8%), nausea and vomiting (65.6%), confusion (50%) and meningeal signs (37.5%). Meningitis was the most frequent clinical presentation (87.8%). Amphotericin B was given to 93.5% of patients as an initial treatment. Positive microbiological identification was accomplished by India ink (94.7%), latex in cerebrospinal fluid (100%) and culture (89.5%). Out of 34 isolates studied, Cryptococcus neoformans var. grubii (VNI 85.3%, VNII 8.8%) was isolated in 94.1% of cases and Cryptococcus gattii (VGII) was isolated in 5.9% of cases. These data are complemented by a literature review, which overall suggests that cryptococcosis in children is an unusual event worldwide.     

Atypical and complicated Kawasaki disease in infants. Do we need criteria?

Case reports suggest that infants with Kawasaki disease have atypical presentations and a high complication rate, likely related to delayed diagnosis and treatment. To date, no study of consecutive cases has compared infants with older children who have both atypical and typical Kawasaki disease. We retrospectively reviewed 44 cases of Kawasaki disease treated at our hospital from March 1980 to 1990: 11 (25%) were infants; 9 (20%) had atypical Kawasaki disease, of which 5 (56%) were infants; the male to female ratio was 1.7:1. Infants had a higher incidence of atypical Kawasaki disease (5 [45%] versus 4 [12%]; P = .007) and of coronary artery complications (7 [64%] versus 3 [9%]; P = .002), and coronary artery complications developed in all of the infants with atypical Kawasaki disease (5 [100%] versus 0 [0%]; P < .01). Yet, the other manifestations and laboratory changes were at least as common as in the older children. Coronary artery complications did not develop in any patient who received early intravenous immune globulin therapy. We suggest that in infants with Kawasaki disease, accepted criteria are too restrictive to allow early diagnosis and effective treatment. Until a definitive test is available, clinical judgment is required in the diagnosis of atypical Kawasaki disease. Intravenous immune globulin is known to be safe, and its early use in patients with suspected atypical Kawasaki disease is appropriate.     

Synthetic lethality of retinoblastoma mutant cells in the Drosophila eye by mutation of a novel peptidyl prolyl isomerase gene

Mutations that inactivate the retinoblastoma (Rb) pathway are common in human tumors. Such mutations promote tumor growth by deregulating the G1 cell cycle checkpoint. However, uncontrolled cell cycle progression can also produce new liabilities for cell survival. To uncover such liabilities in Rb mutant cells, we performed a clonal screen in the Drosophila eye to identify second-site mutations that eliminate Rbf(-) cells, but allow Rbf(+) cells to survive. Here we report the identification of a mutation in a novel highly conserved peptidyl prolyl isomerase (PPIase) that selectively eliminates Rbf(-) cells from the Drosophila eye.