Does a glucose-based hydrogen and methane breath test detect bacterial overgrowth in the jejunum?

BACKGROUND: Direct diagnosis of small intestinal bacterial overgrowth (SIBO) requires the collection and culture of fluid from the jejunal lumen, with a finding of over 105 viable bacteria per mL. More often, SIBO is diagnosed indirectly, using a non-invasive test of the exhaled hydrogen and methane generated by microbial fermentation when ingested glucose reaches the jejunum. Our objective was to determine how well this breath test detects chronic overgrowth of jejunal bacteria that is unrelated to gastrointestinal surgery. METHODS: Eighteen patients reporting symptoms consistent with SIBO received a glucose breath test. On a later day, the jejunal lumen was sampled via aspiration during enteroscopy. Jejunal aspirates were cultured on aerobic and anaerobic media. DNA was extracted from the same samples and analyzed by quantitative pan-bacterial PCR amplification of 16S ribosomal rRNA genes, which provided a culture-independent bacterial cell count. KEY RESULTS: Combined bacterial colony counts ranged from 5.7 x 103 to 7.9 x 106 CFU/mL. DNA-based yields ranged from 1.5 x 105 to 3.1 x 107 bacterial genomes per mL. Microbial viability ranged from 0.3% to near 100%. We found no significant correlation of glucose breath test results with either the number of bacterial colonies or with the DNA-based bacterial cell counts. Instead, higher signals in the hydrogen-methane breath test were significantly correlated with a lower viability of jejunal bacteria, at a P-value of .014. CONCLUSIONS & INFERENCES: The glucose-based hydrogen and methane breath test is not sensitive to the overgrowth of jejunal bacteria. However, a positive breath test may indicate altered jejunal function and microbial dysbiosis.

Pain rather than induced emotions and ICU sound increases skin conductance variability in healthy volunteers.

BACKGROUND: Assessing pain in critically ill patients is difficult. Skin conductance variability (SCV), induced by the sympathetic response to pain, has been suggested as a method to identify pain in poorly communicating patients. However, SCV, a derivate of conventional skin conductance, could potentially also be sensitive to emotional stress. The purpose of the study was to investigate if pain and emotional stress can be distinguished with SCV. METHODS: In a series of twelve 1-min sessions with SCV recording, 18 healthy volunteers were exposed to standardized electric pain stimulation during blocks of positive, negative, or neutral emotion, induced with pictures from the International Affective Picture System (IAPS). Additionally, authentic intensive care unit (ICU) sound was included in half of the sessions. All possible combinations of pain and sound occurred in each block of emotion, and blocks were presented in randomized order. RESULTS: Pain stimulation resulted in increases in the number of skin conductance fluctuations (NSCF) in all but one participant. During pain-free baseline sessions, the median NSCF was 0.068 (interquartile range 0.013-0.089) and during pain stimulation median NSCF increased to 0.225 (interquartile range 0.146-0.3175). Only small increases in NSCF were found during negative emotions. Pain, assessed with the numeric rating scale, during the sessions with pain stimulation was not altered significantly by other ongoing sensory input. CONCLUSION: In healthy volunteers, NSCF appears to reflect ongoing autonomous reactions mainly to pain and to a lesser extent, reactions to emotion induced with IAPS pictures or ICU sound.

Male and female physical intimate partner violence and socio-economic position: a cross-sectional international multicentre study in Europe.

OBJECTIVES: This work explores the association between socio-economic position (SEP) and intimate partner violence (IPV) considering the perspectives of men and women as victims, perpetrators and as both (bidirectional). STUDY DESIGN: Cross-sectional international multicentre study. METHODS: A sample of 3496 men and women, (aged 18-64 years), randomly selected from the general population of residents from six European cities was assessed: Athens; Budapest; London; Östersund; Porto; and Stuttgart. Their education (primary, secondary and university), occupation (upper white collar, lower white collar and blue collar) and unemployment duration (never, ≤12 months and >12 months) were considered as SEP indicators and physical IPV was measured with the Revised Conflict Tactics Scales. RESULTS: Past year physical IPV was declared by 17.7% of women (3.5% victims, 4.2% perpetrators and 10.0% bidirectional) and 19.8% of men (4.1% victims, 3.8% perpetrators and 11.9% bidirectional). Low educational level (primary vs university) was associated with female victimisation (adjusted odds ratio, 95% confidence interval: 3.2; 1.3-8.0) and with female bidirectional IPV (4.1, 2.4-7.1). Blue collar occupation (vs upper white) was associated with female victimisation (2.1, 1.1-4.0), female perpetration (3.0, 1.3-6.8) and female bidirectional IPV (4.0, 2.3-7.0). Unemployment duration was associated with male perpetration (>12 months of unemployment vs never unemployed: 3.8; 1.7-8.7) and with bidirectional IPV in both sex (women: 1.8, 1.2-2.7; men: 1.7, 1.0-2.8). CONCLUSIONS: In these European centres, physical IPV was associated with a disadvantaged SEP. A consistent socio-economic gradient was observed in female bidirectional involvement, but victims or perpetrators-only presented gender specificities according to levels of education, occupation differentiation and unemployment duration potentially useful for designing interventions.

Gender differences in the risk of coronary artery disease in iran.

BACKGROUND: Given gender differences in the risk of coronary artery disease (CAD), the present study sought to investigate these dissimilarities amongst patients who underwent angiography at a major, tertiary heart hospital in Iran. METHODS: Between 2005 and 2010, 44,820 patients who underwent coronary angiography were enrolled in a registry. Pre-procedural data such as demographics, CAD risk factors, presenting symptoms, and laboratory tests, as well as post-procedural data were collected. The data were, subsequently, compared between the men and women. RESULTS: Out of the 44,820 patients (16,378 women), who underwent coronary angiography, 37,358 patients (11,995 women) had CAD. Amongst the CAD patients, the females were not only significantly older, less educated, and more overweight than were the males but also had higher levels of triglyceride, cholesterol, low-density lipoprotein, high-density lipoprotein, and fasting blood sugar (P< 0.001). Of all the risk factors, hypertension and diabetes mellitus showed the strongest association in our female CAD patients (OR=3.45, 95%CI: 3.28-3.61 and OR=2.37, 95%CI: 2.26-2.48, respectively). Acute coronary syndrome was more prevalent in the men (76.1% vs. 68.6%, P< 0.001), and chronic stable angina was more frequent in the females (31.4% vs. 23.9%, P< 0.001). With respect to post-procedural recommendations, the frequency of recommendations for non-invasive modalities was higher in the females (20.1% vs. 18.6%, P< 0.001). CONCLUSION: Hypertension and diabetes mellitus had the strongest association with CAD in our female patients. In the extensive CAD patients, medical treatment was recommended to the women more often.

Effects of a stress management program on vital exhaustion and depression in women with coronary heart disease: a randomized controlled intervention study.

OBJECTIVES: Psychosocial factors, including depression and vital exhaustion (VE) are associated with adverse outcome in coronary heart disease (CHD). Women with CHD are poor responders to psychosocial treatment and knowledge regarding which treatment modality works in them is limited. This randomized controlled clinical study evaluated the effect of a 1-year stress management program, aimed at reducing symptoms of depression and VE in CHD women. DESIGN: Patients were 247 women, < or =75 years, recruited consecutively after a cardiac event and randomly assigned to either stress management (20 2-h sessions) and medical care by a cardiologist, or to obtaining usual health care as controls. Measurements at; baseline (6-8 weeks after randomization), 10 weeks (after 10 intervention sessions), 1 year (end of intervention) and 1-2 years follow-up. RESULTS: For VE, intention to treat analysis showed effects for time (P < 0.001) and time x treatment interaction (P = 0.005), reflecting that both groups improved over time, and that the decrease of VE was more pronounced in the intervention group. However, the level of VE was higher in the intervention group than amongst controls at baseline, 22.7 vs. 19.4 (P = 0.036) but it did not differ later. The change in depressive symptoms did not differ between the groups. CONCLUSIONS: CHD women attending our program experienced a more pronounced decrease in VE than controls. However, as they had higher baseline levels, due to regression towards the mean we cannot attribute the decrease in VE to the intervention. Whether the program has long-term beneficial effects needs to be evaluated.

Burnout among women: associations with demographic/socio-economic, work, life-style and health factors.

This study examined the occurrence of low/high burnout among women and the demographic/socio-economic, work, life-style, and health "correlates" of high burnout. The sample consisted of 6.000 randomly selected women from the general population, of which 3.591 participated. The design was cross-sectional. The univariate analyses showed that about 21% of the women had high burnout, and compared to those with low burnout, they were more often younger, divorced, blue-collar workers, lower educated, foreigners, on unemployment/retirement/sick-leave, financially strained, used more medication and cigarettes, reported higher work demands and lower control/social support at work, more somatic problems (e.g. pain) and depression. The regression analysis showed that only age, sick-leave, financial strain, medication, work demands, depression and somatic ailments were independently associated with high burnout. Thus, women with high burnout were apparently faring poorly financially, emotionally and physically. Considering our findings, interventions to alleviate their problems may be necessary. We may have provided new insights into women's burnout experiences, but longitudinal studies are warranted to firmly identify "determinants" of burnout.

Intensive group cognitive treatment and individual cognitive therapy vs. treatment as usual in social phobia: a randomized controlled trial.

UNLABELLED: To compare the effects of an intensive group cognitive treatment (IGCT) to individual cognitive therapy (ICT) and treatment as usual (TAU) in social phobia (DSM-IV). METHOD: Hundred patients were randomized to: IGCT involving 16 group sessions spread over three weeks; ICT involving 16 shorter weekly sessions in 4 months and; TAU involving an indicated selective serotonin reuptake inhibitor (SSRI) with therapy sessions as required for 1 year. The main outcome measure was a Social Phobia Composite that combined several standardized self-report measures. Diagnostic assessment was repeated at 1-year follow-up. RESULTS: Significant improvements were observed with all treatments. ICT was superior to IGCT and TAU, which did not differ in overall effectiveness. CONCLUSION: The study confirms and extends previously reported findings that ICT is more effective than group cognitive treatment and treatment with SSRIs. IGCT lasts only 3 weeks, and is as effective as more protracted TAU.

A G1103R mutation in CRB1 is co-inherited with high hyperopia and Leber congenital amaurosis.

PURPOSE: To identify the genetic basis of recessive inheritance of high hyperopia and Leber congenital amaurosis (LCA) in a family of Middle Eastern origin. MATERIALS AND METHODS: The patients were examined using standard ophthalmic techniques. DNA samples were obtained and genetic linkage was carried out using polymorphic markers flanking the known genes and loci for LCA. Exons were amplified and sequenced. RESULTS: All four members of this family affected by LCA showed high to extreme hyperopia, with average spherical refractive errors ranging from +5.00 to +10.00. Linkage was obtained to 1q31.3 with a maximal LOD score of 5.20 and a mutation found in exon 9 of the CRB1 gene, causing a G1103R substitution at a highly conserved site in the protein. CRB1 is a vertebrate homolog of the Drosophila crumbs gene, which is required for photoreceptor morphogenesis, and has been associated with either retinitis pigmentosa (RP) or LCA. This sequence variant has previously been reported as a compound heterozygote in one sporadic LCA patient. CONCLUSION: Although hyperopia has been associated with LCA, it is typically moderate and variable between patients with the same mutation. In addition, some CRB1 mutations can be associated with either RP or LCA. We have shown that hyperopia and LCA are linked to the mutant CRB1 gene itself and are not dependent on unlinked modifiers.

Redefining papillorenal syndrome: an underdiagnosed cause of ocular and renal morbidity.

PURPOSE: To report ocular and renal findings specific to the inheritable entity called papillorenal (also known as renal-coloboma) syndrome and relate these to a common cause. DESIGN: Observational case series and genetic study. PARTICIPANTS: Two unrelated probands presenting with absent central retinal vessels and 11 available family members. TESTING: Doppler ultrasonographic imaging of the optic nerves and kidneys, fluorescein angiography, and genetic testing for PAX2 mutations were performed. In selected cases, indocyanine green angiography, scanning laser ophthalmoscope perimetry, Retinal Thickness Analyzer measurements, visual evoked potentials, and magnetic resonance imaging were also performed. MAIN OUTCOME MEASURES: Better defined characteristics of the papillorenal syndrome. RESULTS: Numerous cilioretinal vessels were present with rudimentary or absent central retinal vessels. Superonasal visual field defects, typical for papillorenal syndrome, corresponded to inferotemporal areas of anomalous retinal and choroidal perfusion and hypoplastic retina. Renal hypoplasia was discovered in two affected members of one family (with previously unsuspected renal failure in one case), and recurrent pyelonephritis was discovered in four affected members of the other family. No PAX2 mutations were detected. CONCLUSIONS: In the papillorenal syndrome, the hereditary absence of central retinal vessels may be missed, leading to confusion with isolated coloboma, low-tension glaucoma, and morning glory anomaly. Greater awareness of this syndrome will avoid unneeded glaucoma therapy, allow earlier recognition of renal diseases, and allow genetic counseling. We propose that the papillorenal syndrome is a primary dysgenesis that causes vascular abnormalities predominantly affecting the eye, kidney, and urinary tract, leading to hypoplasia of these structures. The absence of defects in the PAX2 gene in these families suggests that mutations in other genes may also be responsible for this syndrome.

Mutational analysis and clinical correlation in Leber congenital amaurosis.

UNLABELLED: Leber congenital amaurosis (LCA, MIM 204001) is a clinically and genetically heterogeneous retinal disorder characterized by severe visual loss from birth, nystagmus, poor pupillary reflexes, retinal pigmentary or atrophic changes, and a markedly diminished electroretinogram (ERG). PURPOSE: To examine 100 consecutive patients with LCA in order to assess the relative burden of the three known genes involved in LCA, namely retinal guanylyl cyclase (GUCY2D), retinal pigment epithelium protein ( RPE65), and the cone-rod homeobox (CRX), and to define their clinical correlates. METHODS: Mutational analysis and detailed clinical examinations were performed in patients diagnosed with LCA at the Johns Hopkins Center for Hereditary Eye Diseases and the Montreal Children's Hospital. RESULTS: Mutations were identified in 11% of our patients: GUCY2D mutations accounted for 6%, while RPE65 and CRX gene mutations accounted for 3% and 2%, respectively. The clinical presentation was variable; however, the visual evolution in patients with mutations in GUCY2D and CRX remained stable, while individuals with mutations in the RPE65 gene showed progressive visual loss. CONCLUSIONS: This study suggests that molecular diagnosis of Leber congenital amaurosis could provide important information concerning prognosis and course of treatment.

A CRX null mutation is associated with both Leber congenital amaurosis and a normal ocular phenotype.

PURPOSE: To identify and characterize new cone rod homeobox (CRX) mutations associated with the Leber congenital amaurosis phenotype. METHODS: The human CRX gene was sequenced in 74 consecutive patients carrying the diagnosis of Leber congenital amaurosis. RESULTS: Two mutations were identified in CRX that cause frameshifts and predict severe truncations of the encoded protein. One of these, a 1-bp insertion, spares only nine N-terminal amino acids, removing the homeodomain, WSP motif, and conserved OTX domain at the C terminus. Of the CRX mutations described in the literature, this is the first that convincingly represents a null allele of the gene. Although the patient heterozygous for this null allele is affected with Leber congenital amaurosis, it was surprising that her father, who had normal vision, was heterozygous for the same mutation. CONCLUSIONS: These results strongly suggest that haploinsufficiency of CRX is not sufficient to cause a retinal disorder. Loss of function alleles of CRX appear to cause Leber congenital amaurosis through a recessive or multigenic mechanism.

Genetic basis of total colourblindness among the Pingelapese islanders.

Complete achromatopsia is a rare, autosomal recessive disorder characterized by photophobia, low visual acuity, nystagmus and a total inability to distinguish colours. In this disease, cone photoreceptors, the retinal sensory neurons mediating colour vision, seem viable but fail to generate an electrical response to light. Achromatopsia, or rod monochromatism, was first mapped to 2p11-2q12 (MIM 216900; ref. 3), where it is associated with missense mutations in CNGA3 (ref. 4). CNGA3 encodes the alpha-subunit of the cone cyclic nucleotide-gated cation channel, which generates the light-evoked electrical responses of cone photoreceptors. A second locus at 8q21-q22 has been identified among the Pingelapese islanders of Micronesia, who have a high incidence of recessive achromatopsia (MIM 262300). Here we narrow the achromatopsia locus to 1.4 cM and show that Pingelapese achromatopsia segregates with a missense mutation at a highly conserved site in CNGB3, a new gene that encodes the beta-subunit of the cone cyclic nucleotide-gated cation channel. Two independent frameshift deletions establish that achromatopsia is the null phenotype of CNGB3. Combined with earlier findings, our results demonstrate that both alpha- and beta-subunits of the cGMP-gated channel are essential for phototransduction in all three classes of cones.

Two-year results of a controlled study of residential rehabilitation for patients treated with percutaneous transluminal coronary angioplasty. A randomized study of a multifactorial programme.

AIMS: In a multifactorial lifestyle behaviour programme, of 2 years duration, to study the maintenance of achieved behaviour and risk factor-related changes. METHODS AND RESULTS: Out of a consecutive population of 151 patients treated with percutaneous transluminal angioplasty under 65 years of age, 87 were randomly allocated to an intervention group (n=46) or to a control group (n=41). The programme started with a 4 week residential stay, which was focused on health education and the achievement of behaviour change. During the first year of follow-up, a maintenance programme included regular contacts with a nurse, while no further rehabilitative efforts were offered during the second year. One patient died (control). During the second year the proportion of hospitalized patients was lower in the intervention group (4% vs 20%;P<0.05). Patients in the intervention group improved several lifestyle dependent behaviours: diet (index at 0, 12 and 24 months): 10.5+/-3. 4, 12.9+/-2.5 and 12.4+/-2.6 in the intervention group (I) vs 10. 1+/-3.2, 10.7+/-3.0 and 11.8+/-3.2 in the control group (C);P<0.05, exercise sessions per week: 2.5+/-2.3, 4.5+/-1.9 and 4.4+/-2.1 (I) vs 3.1+/-2.2, 3.5+/-2.3 and 3.7+/-2.7 (C);P<0.05, and smoking; 18%, 6% and 9% (I) vs 12%, 21% and 18% (C);P<0.05. This corresponded to improvement in exercise capacity (0, 12 and 24 months): 156+/-42, 174+/-49 and 165+/-47 W (I) vs 164+/-40, 163+/-49 and 156+/-48 watts (C);P<0.05. There were no significant differences between the two groups with regard to serum cholesterol levels at 0 and 24 months: 5. 4+/-0.8 and 5.2+/-0.9 mmol. l(-1)(I) vs 5.4+/-1.0 and 4.9+/-0.9 mmol. l(-1)(C); ns, low density lipoprotein cholesterol level: 3.6+/-0.8 and 3.4+/-0.8 mmol. l(-1)(I) vs 3.7+/-0.9 and 3.3+/-0.7 mmol. l(-1)(C); ns, triglyceride level: 2.2+/-1.6 and 1.8+/-1.3 mmol. l(-1)(I) vs 2.2+/-1.4 and 1.6+/-0.6 mmol. l(-1)(C); ns, body mass index (0, 12 and 24 months): 27.5+/-4.5, 27.0+/-4.3 and 27.4+/- 4.5 kg. m(-2)(I) vs 26.8+/-2.8, 26.9+/-2.7 and 26.9+/- 3.2 kg. m(-2)(C); ns, waist/hip ratio or blood pressure. The two groups did not differ in quality of life, or psychological factors. Return to work after 12 and 24 months was 74% and 78% (I) vs 68% and 61% (C); ns. CONCLUSION: This rehabilitation programme influenced important lifestyle behaviour and reduced some, but not all, important risk factors

Sequence and location of SIX3, a homeobox gene expressed in the human eye.

Mouse Six3 is a homeobox gene expressed almost exclusively in the developing retina, lens, hypothalamus, and pituitary. It belongs to the same family as sine oculis, a Drosophila regulatory gene that encodes a transcription factor essential for eye development. The optix gene is its closest known Drosophila homologue, with a homeodomain that is 95% identical in sequence to the Six3 protein. We have isolated the homologous human gene, SIX3, which is expressed in the adult retina and encodes a 332 amino acid protein that is 98% identical to its mouse counterpart. The SIX3 protein coding region is interrupted by a single intron located just downstream of the homeobox. A surprising feature of the SIX3 gene is a 533 nucleotide 5' untranslated region that contains long polypyrimidine tracts with 96% identity to mouse Six3. We have used in-situ hybridization to map SIX3 to 2p21-p22, a site that is syntenic with the Six3 region of mouse chromosome 17. Large heterozygous deletions associated with human holoprosencephaly type 2 have been previously mapped to 2p21, opening the possibility that SIX3 could be involved in the development of midline structures of the head. Alternatively, the expression pattern of mouse Six3 suggests that human SIX3 could be involved in disorders of eye and pituitary development.

Expression of the optx2 homeobox gene during mouse development.

Optx2, a member of the sine oculis-Six family of homeobox genes, is first expressed in the anterior neural plate of the mouse embryo, and subsequently in the optic vesicle and ventral forebrain. During later development, expression is further restricted to precursors of the neural retina, optic chiasm, adenohypophysis and neurohypophysis. In the adult mouse retina, Optx2 mRNA is found in cells within the ganglion cell layer and inner nuclear layer.

Multifactorial evaluation of a program for lifestyle behavior change in rehabilitation and secondary prevention of coronary artery disease.

A comprehensive, multifactorial lifestyle behavior change program was developed for rehabilitation and secondary prevention of subjects with coronary artery disease. The purpose of the present report is to describe this intervention model and to analyze results achieved in a first group of consecutive participants. Main inclusion criteria for the 292 subjects were a recent history of acute myocardial infarction, coronary artery bypass surgery, or percutaneous transluminal coronary angioplasty. The program commenced with a 4-week residential stay, with the focus on health education and the achievement of behavior change in major lifestyle areas. During the year of follow-up a systematic maintenance program included regular contact with a nurse. Morbidity and mortality was low. Self-reported quality of life improved and there were significant improvements in blood lipids, exercise capacity and body mass index. There were also significant changes both in psychological variables such as Type A behavior, anger, hostility, and in major lifestyle areas such as stress reactions, diet, exercise and smoking. These changes compared favorably with data from relevant samples from the Swedish normal population. This program had a considerable effect on a number of important factors for rehabilitation and secondary prevention of coronary artery disease.

Behavioral effects of a comprehensive, multifactorial program for lifestyle change after percutaneous transluminal coronary angioplasty: a prospective, randomized controlled study.

A group of 93 coronary patients recently treated with percutaneous transluminal coronary angioplasty (PTCA) were randomly assigned to either an intervention or a control group. Subjects in the intervention group participated in a comprehensive behaviorally oriented program aimed at achieving significant long-term changes in risk factor-related lifestyle behavior. Assessments of lifestyle behaviors, psychological factors, biological risk factors, and rehabilitation as well as secondary prevention endpoints were carried out, at inclusion and after 12 months. Results showed that the intervention patients, as compared with controls, improved significantly on measures assessing smoking, exercise, and diet habits. These self-rated changes were confirmed by weight reductions and improved exercise capacity, as well as by between-group differences in subclinical chest pain during an exercise test. However, few effects were found on the different psychological variables, as well as on morbidity or return to work.

The optx2 homeobox gene is expressed in early precursors of the eye and activates retina-specific genes.

Vertebrate eye development begins at the gastrula stage, when a region known as the eye field acquires the capacity to generate retina and lens. Optx2, a homeobox gene of the sine oculis-Six family, is selectively expressed in this early eye field and later in the lens placode and optic vesicle. The distal and ventral portion of the optic vesicle are fated to become the retina and optic nerve, whereas the dorsal portion eventually loses its neural characteristics and activates the synthesis of melanin, forming the retinal pigment epithelium. Optx2 expression is turned off in the future pigment epithelium but remains expressed in the proliferating neuroblasts and differentiating cells of the neural retina. When an Optx2-expressing plasmid is transfected into embryonic or mature chicken pigment epithelial cells, these cells adopt a neuronal morphology and express markers characteristic of developing neural retina and photoreceptors. One explanation of these results is that Optx2 functions as a determinant of retinal precursors and that it has induced the transdifferentiation of pigment epithelium into retinal neurons and photoreceptors. We also have isolated optix, a Drosophila gene that is the closest insect homologue of Optx2 and Six3. Optix is expressed during early development of the fly head and eye primordia.

Pax-6, Prox 1, and Chx10 homeobox gene expression correlates with phenotypic fate of retinal precursor cells.

PURPOSE: To study the expression patterns of the homeobox genes Pax-6, Prox 1, and Chx10 during chick retinal development in vivo and in vitro. METHODS: Sections of paraformaldehyde-fixed, paraffin-embedded eyes were obtained at a range of developmental stages. In situ hybridization was carried out on tissue sections using digoxigenin-labeled sense and antisense RNA probes that recognize chicken Pax-6 and Prox 1 (whose sequences were already available), and chicken Chx10 (which was cloned and sequenced as part of this study). Selected developmental stages were also studied by immunocytochemistry with antibodies against Pax-6 and Prox 1, and by Northern blot analysis using 32P-labeled probes. RESULTS: Until embryonic day (ED) 5, in situ hybridization shows widespread, diffuse distribution of all three genes. Between ED 6 and ED 8, however, they acquire distinct, topographically specific patterns of expression. The Prox 1 signal is predominantly expressed in the prospective horizontal cell layer of the neuroepithelium, decreases vitreally, and is absent from ganglion cells and the prospective photoreceptor layer. Pax-6 is strongly expressed only in the prospective ganglion-cell and amacrine-cell regions at the same stages, and is not detected in prospective photoreceptors. Chx10 expression becomes concentrated in the future bipolar-cell region of the inner nuclear layer. Similar patterns are maintained by ED 15 through ED 18, after cell differentiation has taken place. Pax-6 and Prox 1 immunoreactive materials showed nuclear localization and a pattern of laminar distribution equivalent to that seen by in situ hybridization. CONCLUSIONS: These results suggest that the differentiated fate of retinal precursor cells may be influenced by Pax-6, Prox 1, or Chx10, this hypothesis is now being tested using dissociated chick embryo retinal cell cultures.