The vascular geometry of the choriocapillaris is associated with spatially heterogeneous molecular exchange with the outer retina

Vision relies on the continuous exchange of material between the photoreceptors, retinal pigment epithelium and choriocapillaris, a dense microvascular bed located underneath the outer retina. The anatomy and physiology of the choriocapillaris and their association with retinal homeostasis have proven difficult to characterize, mainly because of the unusual geometry of this vascular bed. By analysing tissue dissected from 81 human eyes, we show that the thickness of the choriocapillaris does not vary significantly over large portions of the macula or with age. Assessments of spatial variations in the anatomy of the choriocapillaris in three additional human eyes indicate that the location of arteriolar and venular vessels connected to the plane of the choriocapillaris is non-random, and that venular insertions cluster around arteriolar ones. Mathematical models built upon these anatomical analyses reveal that the choriocapillaris contains regions where the transport of passive elements is dominated by diffusion, and that these diffusion-limited regions represent areas of reduced exchange with the outer retina. The width of diffusion-limited regions is determined by arterial flow rate and the relative arrangement of arteriolar and venular insertions. These analyses demonstrate that the apparent complexity of the choriocapillaris conceals a fine balance between several anatomical and functional parameters to effectively support homeostasis of the outer retina. KEY POINTS: The choriocapillaris is the capillary bed supporting the metabolism of photoreceptors and retinal pigment epithelium, two critical components of the visual system located in the outer part of the retina. The choriocapillaris has evolved a planar multipolar vascular geometry that differs markedly from the branched topology of most vasculatures in the human body. Here, we report that this planar multipolar vascular geometry is associated with spatially heterogenous molecular exchange between choriocapillaris and outer retina. Our data and analyses highlight a necessary balance between choriocapillaris anatomical and functional parameters to effectively support homeostasis of the outer retina.

Clinical, histological and genetic findings in a donor with a clinical history of type 1 Autoimmune Polyendocrinopathy Syndrome

Purpose

Autoimmune Polyendocrinopathy Syndrome (APS) is a rare condition caused by an autoimmune failure of two or more endocrine glands. In this case, we report the ocular findings and correlated histopathology from a human eye donor with a prior clinical history of Type 1 APS.

Observations

The 23 year-old patient originally presented with blurred vision at the 20/125 level caused by papilledema of the right eye. Bilateral pigmentary changes in the peripheral retinal were also noted. The patient passed away due to electrolyte abnormalities related to autoimmune illness. Histopathology of the posterior segments documents that these pigmentary changes were caused by pigment deposition around inner retinal vessels with corresponding outer retina atrophy. Postmortem genetic sequence analyses revealed a homozygous R257X (C to T substitution) mutation within exon 6 of the AIRE gene.

Conclusions and importance

The retinal findings in Type 1 Autoimmune Polyendocrinopathy Syndrome resemble those observed in individuals with retinitis pigmentosa, suggesting that similar pathological processes occur in both.

Changes in the survival of patients with systemic lupus erythematosus in childhood: 30 years experience in Chile

The objective of this study was to analyse the survival rate and cause of death in children with systemic lupus erythematosus (SLE) during the past 30 years in Chile. A retrospective analysis was performed between 1969 and 2000 on patients attending pediatric rheumatology centres in Santiago, Chile. Survival and causes of death in 31 children followed from 1969 to 1980 fulfilling the 1982 American College of Rheumatology criteria for SLE and treated with oral steroids were compared with 50 other patients who were treated with oral steroids and an aggressive treatment of IV bolus of cyclophosphamide (38 patients) and azathioprine (12 patients). Global survival at five and 10 years follow-up for the patients studied from 1969 to 1980 was 68 and 40%, respectively. During the second study period these values were significantly improved and global survival reached 95% at five years and 90% at 10 years follow-up (P, 0.05). Survival at 10 years follow-up for patients with lupus nephropathy increased from 28% (study period 1964-1980) to 86% (study period 1984-2000). Twelve children died (38%) during the 1964-1980 study period. The causes of death were six due to kidney failure, three due to infectious conditions and another three of unknown causes. During the 1980-2000 study period mortality reached 6% (three cases), two cases died of a lupus flare-up and one case due to infection. In the last three decades, we have seen an important increase in the survival of children with SLE, especially in those patients with renal involvement. Management with immunosuppressive drugs, such as IV cyclophosphamide or azathioprine has changed the prognosis in these children. These results demonstrate that our children with SLE increased their life expectancy but are now faced with new types of morbidity because of the sequelae related to the disease itself.

Assessment of Proteins Associated With Complement Activation and Inflammation in Maculae of Human Donors Homozygous Risk at Chromosome 1 CFH-to-F13B

PURPOSE

To determine the effects of chromosome 1 genotype and cigarette smoking on levels of complement activation and inflammation in the human macula.

METHODS

Donor macular tissue was stratified into three groups by diplotype at the AMD-associated CFH-to-F13B locus: homozygous "risk" (n = 9, 56-78 years), homozygous neutral (n = 2, 64-79 years), and homozygous "protective" (n = 6, 61-78 years) diplotype. Importantly, all donors were homozygous nonrisk at the ARMS2/HTRA1 locus, so that purely chromosome 1-directed pathways were examined. Immunohistochemistry was performed by using 14 antibodies, mostly against markers of complement and inflammation, followed by confocal microscopy and immunofluorescence quantification (all masked to donor status).

RESULTS

Donors homozygous risk at CFH-to-F13B exhibited significantly higher levels of terminal complement complex (TCC) in macular Bruch's membrane (BM; P = 0.03), choriocapillaris (CC; P = 0.04), and choriocapillaris intercapillary septa (CC IS; P = 0.03), compared to homozygous protected donors. Smoking was associated with increased TCC in BM (P = 0.05), CC IS (P = 0.03), and choroidal stroma (CS; P = 0.01), and with substantially elevated C-reactive protein (CRP) levels in RPE (P = 0.04), BM (P = 0.01), CC (P = 0.05), and CS (P = 0.05). Smoking was associated with higher levels of oxidative stress in macular RPE (P = 0.04) and CS (P = 0.01).

CONCLUSIONS

Genetic risk at the CFH-to-F13B locus was associated with higher levels of complement activation at the human macular RPE-choroid interface, as was cigarette smoking. Levels of CRP were substantially elevated in risk donors with smoking history. Examination of human macular tissue from donors with "pure" diplotypes allows assessment of AMD-associated pathways driven solely by CFH-to-F13B. These findings have important implications for identifying chromosome 1-directed pathways and therapeutic targets.

Expressed sequence tag (EST) analysis of Gregarine gametocyst development

Gregarines are protozoan parasites of invertebrates in the phylum Apicomplexa. We employed an expressed sequence tag strategy in order to dissect the molecular processes of sexual or gametocyst development of gregarines. Expressed sequence tags provide a rapid way to identify genes, particularly in organisms for which we have very little molecular information. Analysis of approximately 1800 expressed sequence tags from the gametocyst stage revealed highly expressed genes related to cell division and differentiation. Evidence was found for the role of degradation and recycling in gametocyst development. Numerous additional genes uncovered by expressed sequence tag sequencing should provide valuable tools to investigate gametocyst development as well as for molecular phylogenetics, and comparative genomics in this important group of parasites.

Childhood stroke associated with protein C or S deficiency and primary antiphospholipid syndrome

Two girls, 22 months and 12 years of age, presented with repeated cerebral infarctions in association with primary antiphospholipid syndrome. The younger patient also suffered from protein C deficiency, while the other one had protein S and complement C4 deficiencies. All other causes of cerebral infarction were excluded; however, vasculitis remains a possibility in one patient. Both girls developed spastic tetraparesis as a sequela of the previous infarctions. The two patients were treated with aspirin and prednisone, with remission of the infarctions during the next 8 months of observation. A primary deficiency of protein C or S is proposed which would produce cerebral thrombosis with exposure of phospholipids; this thrombosis then, like antigens, would generate antibodies acting on the thrombin-thrombomodulin complex, exacerbating the thrombotic process. The association of complement C4 deficiency is an additional risk factor.

Antihypertensive activity of once daily metoprolol alone and with chlorthalidone and comparison with a twice daily regimen

In a multicentre, double-blind (DB), within-patient study, the antihypertensive effectiveness and tolerability of two oral administration schedules of metoprolol (M) 100 mg b.i.d. versus 200 mg once daily (o.d.), were investigated in 103 outpatients with mild to moderate essential hypertension. The study lasted 14 weeks and was divided into 3 periods: a) a weeks of single-blind (SB) placebo wash-out; b) 4 weeks of SB administration of M 100 mg b.i.d.; at the end of the second week of this period, chlorthalidone (C) 25 mg was added in patients with a recumbent diastolic blood pressure (BP) still greater than 95 mmHg and was continued throughout the following period; and c) DB cross-over administration of M 200 mg/d for 4 weeks on a b.i.d. schedule and 4 weeks on a once daily schedule. In comparison with pretreatment values, heart rate and systolic and diastolic BP were reduced (p less than 0.001) by both M administration schedules; there was no differences between the once and twice daily treatment regimens. During M once daily, betablockade was still maintained over 24 hours or longer, as the heart rate remained significantly lower than the basal value. In 57 patients, C was added at the end of the second week of SB M administration, and a further decrease in BP was observed; again, there was no significant change during once and twice daily M administration. Unwanted effects during M treatment were of minor severity, and the majority occurred when C, too, was added.

A fixed combination of oxprenolol slow-release and chlorthalidone once daily in treatment of mild to moderate hypertension

In a multicenter, single-blind, interpatient study, 103 outpatients with mild to moderate hypertension were given, after 2 weeks of placebo wash-out, 160 mg oxprenolol slow-release in fixed combination with chlorthalidone (20 mg per tablet) (SROC 160) once daily or conventional oxprenolol (80 mg) in fixed combination with chlorthalidone (10 mg per tablet) (COC 80) twice daily for 8 weeks. Throughout the study 22 of 51 patients on SROC 160 and 24 of 51 on COC 80 received 1 tablet once daily and, respectively, 1 tablet twice daily. The remaining patients of both groups double the corresponding dosage after the first 4 weeks. Systolic and diastolic blood pressure decreased on both treatments without and difference observed between the groups. Diastolic blood pressure normalization was achieved in both groups in the same number of patients (35). Minor side effects occurred on both treatments: only one patient on SROC 160 interrupted the study due to severe dizziness and fatigue. The advantages are discussed as regards patient's compliance with administration of fixed combination SROC 160 once daily in treatment of mild to moderate hypertension.

[A case of polyarteritis nodosa associated with pulmonary hypertension]

A case of polyarteritis nodosa marked by concomitant systemic and pulmonary hypertension is presented. The part played by pulmonary hypertension in this disease is briefly discussed in the light of the necropsy findings and the literature.