Swallowing disorders, pneumonia and respiratory tract infectious disease in the elderly.

Swallowing disorders (or dysphagia) are common in the elderly and their prevalence is often underestimated. They may result in serious complications including dehydration, malnutrition, airway obstruction, aspiration pneumonia (infectious process) or pneumonitis (chemical injury caused by the inhalation of sterile gastric contents). Moreover the repercussions of dysphagia are not only physical but also emotional and social, leading to depression, altered quality of life, and social isolation. While some changes in swallowing may be a natural result of aging, dysphagia in the elderly is mainly due to central nervous system diseases such as stroke, parkinsonism, dementia, medications, local oral and oesophageal factors. To be effective, management requires a multidisciplinary team approach and a careful assessment of the patient's oropharyngeal anatomy and physiology, medical and nutritional status, cognition, language and behaviour. Clinical evaluation can be completed by a videofluoroscopic study which enables observation of bolus movement and movements of the oral cavity, pharynx and larynx throughout the swallow. The treatment depends on the underlying cause, extent of dysphagia and prognosis. Various categories of treatment are available, including compensatory strategies (postural changes and dietary modification), direct or indirect therapy techniques (swallow manoeuvres, medication and surgical procedures).

[Swallowing disorders, pneumonia and respiratory tract infectious disease in the elderly]. / Troubles de la déglutition du sujet âgé et pneumopathies en 14 questions/réponses.

Swallowing disorders (or dysphagia) are common in the elderly and their prevalence is often underestimated. They may result in serious complications including dehydration, malnutrition, airway obstruction, aspiration pneumonia (infectious process) or pneumonitis (chemical injury caused by the inhalation of sterile gastric contents). Moreover the repercussions of dysphagia are not only physical but also emotional and social, leading to depression, altered quality of life, and social isolation. While some changes in swallowing may be a natural result of aging, dysphagia in the elderly is mainly due to central nervous system diseases such as stroke, parkinsonism, dementia, medications, local oral and oesophageal factors. To be effective, management requires a multidisciplinary team approach and a careful assessment of the patient's oropharyngeal anatomy and physiology, medical and nutritional status, cognition, language and behaviour. Clinical evaluation can be completed by a videofluoroscopic study which enables observation of bolus movement and movements of the oral cavity, pharynx and larynx throughout the swallow. The treatment depends on the underlying cause, extent of dysphagia and prognosis. Various categories of treatment are available, including compensatory strategies (postural changes and dietary modification), direct or indirect therapy techniques (swallow manoeuvres, medication and surgical procedures).

Varying insulin use in older hospitalized patients with diabetes.

OBJECTIVE: Observation of insulin use in consecutive hospitalized diabetic older patients in acute care wards with reference to nutritional intakes, measures of functional status, and varying clinical situations. METHODS: Prospective case study in a geriatric medicine ward with CGA, dietary intake measure and used insulin dosage. RESULTS: Among 600 inpatients, 90 diabetic subjects were found. Only 12.2 % diabetic patients had MMSE > 23 and 23.3% were unable to eat without assistance. During the stay 54 patients had received insulin. From admission to discharge or death, doses were 0.39 to 0.19 U/kg (SD 0.41-0.15) during palliative care, 0.43 to 0.45 U/kg (SD 0.20-0.20) in the event of failure of oral therapy, 0.38 to 0.42 U/kg (SD 0.18-0.25) if creatinine clearance was 30 ml/min or lower, and 0.38 to 0.27 U/kg (SD 0.24-0.26) in critical diseases. Dietary intake increased in all during the stay with an energy intake close to 20 kCal/kg/d at discharge, except for those in palliative care, who had a final intake of 8.2 kCal/kg/d (SD 9.1). CONCLUSION: Insulin treatment guidelines adapted to this frail diabetic population are necessary.

[Lung cancer in the elderly subject]. / Cancer bronchique du sujet âgé.

INTRODUCTION: In France, the average age for the diagnosis of bronchial carcinoma is 64. It is 76 in the population of over 70. In fact, its incidence increases with age linked intrinsic risk of developing a cancer and with general ageing of the population. Diagnosis tools are the same for elderlies than for younger patients, and positive diagnosis mainly depends on fibreoptic bronchoscopy, complications of which being comparable to those observed in younger patients. STATE OF THE ART: The assessment of dissemination has been modified in recent years by the availability of PET scanning which is increasingly becoming the examination of choice for preventing unnecessary surgical intervention, a fortiori in elderly subjects. Cerebral imaging by tomodensitometry and nuclear magnetic resonance should systematically be obtained before proposing chirurgical treatment. An assessment of the general state of health of the elderly subject is an essential step before the therapeutic decision is made. This depends on the concept of geriatric evaluation: Geriatric Multidimensional Assessment, and the Comprehensive Geriatric Assessment which concerns overall competence of the elderly. PERSPECTIVES: This is a global approach that allows precise definition and ranking of the patient's problems and their impact on daily life and social environment. Certain geriatric variables (IADL, BADL, MMSE, IMC etc) may be predictive of survival rates after chemotherapy or the incidence of complications following thoracic surgery. The main therapeutic principles for the management of bronchial carcinoma are applicable to the elderly subject; long term survival without relapse after surgical resection is independent of age. Whether the oncological strategy is curative or palliative, the elderly patient with bronchial carcinoma should receive supportive treatments. They should be integrated into a palliative programme if such is the case. In fact, age alone is not a factor that should detract from optimal oncological management. CONCLUSIONS: The development of an individual management programme for an elderly patient suffering from bronchial carcinoma should be based on the combination of oncological investigation and comprehensive geriatric assessment.

[Analysis of left-censored quantitative outcome: example of procalcitonin level]. / Analyse d'une variable quantitative censurée à gauche: exemple du taux de procalcitonine.

BACKGROUND: When the sensitivity of an assay used to quantify a marker is poor, some of the values are below the detection limit resulting in left-censoring. Analysis of such data requires appropriate statistical techniques. In this study, we aimed at comparing various methods used to deal with left-censored outcome in regression analysis. METHODS: The application was a real study evaluating the performance of procalcitonin for the diagnosis of bacterial infections among elderly patients. Among 85 patients, eleven had a procalcitonin value below the detection limit. A simulation study was then performed with data sampled according to a Gaussian distribution with parameters estimated on observed data. Various levels of left-censoring were simulated (13, 25 and 50%). A linear regression model was used to explain procalcitonin variations according to another marker, C reactive protein. To handle left-censoring, several methods were used: complete case analysis, simple imputation and multiple imputation methods, and parametric modelling. In the simulation study, estimations according to different methods were compared in terms of bias and mean square error according to each left-censoring level. Estimations obtained with real data were also compared according to the methods used. All analyses were implemented using SAS software. RESULTS: In the simulation study, parametric modelling using maximum likelihood showed best performances whatever the level of censoring. On the other hand, methods using complete cases and simple imputation by the detection limit were highly skewed. On observed data, estimations of the slope varied slightly according to the methods. However the p-values (Wald test) of beta=0 varied from 0.0001 to 0.13 leading to different decisions according to the method used. CONCLUSION: Left-censoring handling in data analysis requires special attention, as different methods may yield results leading to different conclusions.

[Evaluation of pulmonary function in the elderly. Intergroupe Pneumo Gériatrie SPLF-SFGG]. / Evaluation de la fonction respiratoire chez le sujet âgé. Intergroupe Pneumo Gériatrie SPLF-SFGG.

Aging is associated with a progressive decrease in lung function. As a consequence of aging, individual's reserve is diminished, but this decrease is heterogeneous between individual subjects. Many factors are involved in the overall decline in lung function. The prevalence of asthma in the elderly is estimated between 6 and 10%. Mortality due to COPD is increasing, especially among older subjects. Older subjects are at an increased risk of developing chronic diseases such as Parkinson's disease, which can have consequences for lung function. Under-nutrition is also common in the elderly and can produce sarcopenia and skeletal muscle dysfunction. The presentation of respiratory disorders may differ in the elderly, especially because of a lack of perception of symptoms such as dyspnea. The impact of bronchodilatators or corticosteroids on respiratory function has not been studied in the elderly. Drugs usually used for the treatment of hypertension or arrhythmias, which are often observed with aging, can have pulmonary toxicity. There is no difference between functional evaluation in younger and older subjects but it is more difficult to find predicted values for older patients. Performing pulmonary function tests in older patients is often difficult because of a higher prevalence of cognitive impairment and/or poor coordination. When assessing pulmonary function in the elderly, the choice of tests will be depend on the circumstances, with the use of voluntary manoeuvres dependent on the condition of the patient.

Prospective audit of diabetes care and outcomes in a group of geriatric French care homes.

BACKGROUND: In geriatric institutions, diabetes prevalence varies from 10 to 20%. However, little is known about patterns of care and their outcomes. To assess both, an 18-month prospective audit was conducted in 240-bed nursing and 80-bed residential care homes. METHODS: In diabetic subjects, items of care were compared to the corresponding French guideline end-points. Dependency in activities for daily living (ADL) was evaluated at inclusion and at the end of the survey for survivors. Diabetic residents were compared to others for age, sex, mortality and one-year change of iso-resource group ranging (IRG), a need-of-care scale. RESULTS: The 73 diabetic patients among 494 residents (14.8%) were not different from the others for age and sex (respectively age: 76.0 y +/- 7.9 compared to 78.2 y +/- 9.4; M/F sex ratio: 0.59 compared to 0.31). Oral hypoglycemic agents were prescribed in 29 (39.7%) and insulin in 26 (35.6%). Control of diabetes with HbA(1C) was in keeping with guidelines in 23.3%, HbA(1C) was never performed in 26%, and > 8% in 20.5%. Rates of items of guidelines that were never addressed ranged from 2 to 80%. During the stay, ADL dependency worsened in diabetic patients, but their one-year change in GIR range was not different from that in the others. Mortality was 30.1% compared to 37.1% in the others (NS). This mortality rate and the evolution of functional dependency were not influenced by the quality of diabetes control. CONCLUSION: In these disabled elderly patients, diabetes management needs to be improved. However, mortality and the evolution of functional dependency were similar in diabetic people than in others. Interventional studies for controlling with reference to geriatric evaluation, i.e. function, nutrition and mental health, are needed in order to establish specific guidelines based on benefit-burden analysis.

Is a 24-h cyclic closed enteral feeding system microbiologically safe in geriatric patients?

BACKGROUND AND AIMS: The microbiological quality of a 1-l closed enteral feeding system (CS) was prospectively monitored under clinical conditions simulating cyclic feeding over a 24-h period in geriatric patients. METHOD: The set was connected after diet sampling (T0). After 5-h feeding, the set was disconnected and a sample taken (T5). Diet was sampled after 12 h before (T12A) and after a 10 ml diet-flush of the set (T12B), after 24-h (T24) and in the pouch (P24). Concentrations of micro-organisms were considered significant when above 10(4) colony-forming units per millilitre. RESULTS: Twenty-one CS were examined. T0 samples were all sterile; 10 out of 21 T5 were contaminated. The microbiological content of the diet was lower in T12B, compared to T12A (P=0.002). None of the P24 samples was contaminated; 19 were sterile and two contained low levels of micro-organisms that had been previously found in the sets. CONCLUSION: The CS was sterile before connecting to the patient. Retrograde contamination of the set was observed without contamination of the pouch after 24-h hanging time. Performing a diet-flush decreased the rate of diet contamination at the distal extremity of the set. Thus, cyclic enteral nutrition using the same pouch during a 24-h period seems to be safe in geriatric patients.

Reticular premotor neurons projecting to both facial and hypoglossal nuclei receive trigeminal afferents in rats.

The distribution of premotor neurons projecting to motor nuclei of both the VIIth (VII) and XIIth (XII) nerves was examined in the pontomedullary reticular formation (RF) of the rat by using retrograde double labeling. After injection of two different tracers in the VII and the XII, most of the double labeled neurons were found caudally in the dorsal RF whereas rostrally they were located in the ventral RF. In some experiments, additional injections of an anterograde tracer were made in the sensory trigeminal nuclei. Anterogradely labeled trigeminal boutons were found in contact with retrogradely double labeled neurons throughout the pontomedullary RF. These neurons were mainly encountered ventral to the trigeminal motor nucleus and dorsal to the VII. Functionally, this region is known to be involved in eye protection mechanisms.

Trigemino-reticulo-facial and trigemino-reticulo-hypoglossal pathways in the rat.

This study was undertaken to identify premotor neurons in the pontomedullary reticular formation serving as relay neurons between the sensory trigeminal complex and the motor nuclei of the VIIth and XIIth nerves. Trigeminoreticular projections were first investigated after injections of anterogradely transported tracers (biotinylated dextran amine, biocytin) into single subdivisions of the sensory trigeminal complex. The results show that the trigeminoreticular projections were abundant from the pars interpolaris (5i) and caudalis (5c) and moderate from pars oralis (5o) of the spinal trigeminal nucleus. Injections into the 5i and 5c produce dense anterograde labeling (1) in the dorsal medullary reticular field; (2) in the parvocellular reticular field, medially adjacent to the 5i; and (3) more rostral in the region dorsal and lateral to the superior olivary nucleus. Some labeled terminals were also found in the intermediate reticular field, whereas only light anterograde labeling was observed in the gigantocellular and oral pontine reticular formation. The 5o sends fibers and terminals throughout the whole reticular formation, with no clear preferential projections within a particular field. Only light projections originated from the principal nucleus (5P). In a second series of experiments, we examined whether premotor neurons in the reticular formation are afferented by trigeminal fibers. Double labeling was performed by injection of an anterograde tracer in the 5i and 5c and retrograde tracer (gold-horseradish peroxidase complex) into the VII or the XII motor nucleus on the same side. Retrogradely labeled neurons in contact with anterogradely labeled boutons were found throughout the reticular formation with predominance in the parvocellular and intermediate reticular fields. These experiments demonstrate the existence of trigeminal disynaptic influences, via reticular neurons of the pontomedullary reticular formation, in the control of orofacial motor behaviors.

[Annual incidence and risk factors for nosocomial bacterial infections in an acute care geriatric unit]. / Incidence sur un an et facteurs de risque des infections nosocomiales bactériennes dans un service de médecine interne gériatrique.

PURPOSE: Elderly inpatients are particularly exposed to the risk of nosocomial infections, thus the study of their risk factors and consequences is of interest. METHODS: Among 1,565 subjects referred to a short-term geriatric unit, patients hospitalised for a year for an acute event and unable to move themselves were followed up for the occurrence of nosocomial infections. RESULTS: Among these 402 immobilised patients (age: 86.3 +/- 7.6 years), 102 nosocomial infections occurred in 91 patients (22.6%), whereas the estimation of the incidence in the total hospitalised population (1,565 subjects, age: 85.1 +/- 6.2 years) was 9.4% (95% confidence interval [CI] 8.3-11.2). Forty-seven point seven percent of nosocomial infections were urinary tract nosocomial infections, 27.5% were lower respiratory nosocomial infections, 9.2% were cutaneous nosocomial infections, 7.3% were septicaemia and 8.2% were of unknown origin. The relative risk (RR) of NI linked to functional dependency for mobility was 5.5 (95% CI: 3.93-7.7, P < 0.001). Other risk factors were: for all nosocomial infections: cancer diagnosis (RR 1.1, 95% CI: 1.1-1.2, P = 0.01); and respectively for urinary tract NI: bladder indwelling (RR 4.8, 95% CI: 2.9-7.7, P < 0.001), pulmonary NI: swallowing disorders (RR 5.4, 95% CI: 2.8-10.5, P < 0.001); and septicaemia: venous catheter (RR 5.4, 95% CI: 1.3-23.3, P = 0.002). NI were associated with an increased length of stay (22.1 +/- 11.7 days in infected patients vs 16.3 +/- 9.5 days in immobilised non-infected subjects, P < 0.001). The mean length of stay for the 1,565 subjects was 10.3 +/- 7.6 days. Death was attributed to nosocomial infections in 13 subjects. In conclusion, functional dependency for mobility, bladder indwelling, venous catheter, swallowing disorders and diagnosis of cancer were risk factors for nosocomial infections in hospitalised elderly subjects in an acutecare setting.

Connections between the trigeminal mesencephalic nucleus and the superior colliculus in the rat.

Retrograde tracing methods are employed here to demonstrate that neurons in the trigeminal mesencephalic nucleus (5me) project to the superior colliculus (SC) in the rat. These neurons, mainly of small size, are situated bilaterally in the caudal part of the nucleus. Anterograde tracing studies demonstrated the existence of SC projections to neurons in 5me. The SC fibers contact 'en passant' small as well as large cell bodies of 5me neurons. These pathways suggested a role of the 5me neurons in oculomotor control and associated oro-facial functions.

Trigeminal projections to hypoglossal and facial motor nuclei in the rat.

This study was undertaken to identify the trigeminal nuclear regions connected to the hypoglossal (XII) and facial (VII) motor nuclei in rats. Anterogradely transported tracers (biotinylated dextran amine, biocytin) were injected into the various subdivisions of the sensory trigeminal complex, and labeled fibers and terminals were searched for in the XII and VII. In a second series of experiments, injections of retrogradely transported tracers (biotinylated dextran amine, gold-horseradish peroxidase complex, fluoro-red, fluoro-green) were made into the XII and the VII, and labeled cells were searched for in the principal sensory trigeminal nucleus, and in the pars oralis, interpolaris, and caudalis of the spinal trigeminal nucleus. Trigeminohypoglossal projections were distributed throughout the ventral and dorsal region of the XII. Neurons projecting to the XII were found in all subdivisions of the sensory trigeminal complex with the greatest concentration in the dorsal part of each spinal subnucleus and exclusively in the dorsal part of the principal nucleus. Trigeminofacial projections reached all subdivisions of the VII, with a gradual decreasing density from lateral to medial cell groups. They mainly originated from the ventral part of the principal nucleus. In the spinal nucleus, most of the neurons projecting to the VII were in the dorsal part of the nucleus, but some were also found in its central and ventral parts. By using retrograde double labeling after injections of different tracers in the XII and VII on the same side, we examined whether neurons in the trigeminal complex project to both motor nuclei. These experiments demonstrate that in the spinal trigeminal nucleus, neurons located in the pars caudalis and pars interpolaris project by axon collaterals to XII and VII.

Prospective audits of quality of PEM recognition and nutritional support in critically ill elderly patients.

BACKGROUND AND AIMS: Undereating is a frequent concern in acute care geriatric settings and is supposed to worsen the outcomes of the underlying diseases, while the quality of nutritional support could be improved. METHODS: Two consecutive and prospective audits (A and B) with team training over a 1 year period investigated the quality of malnutrition recognition and nutritional support and outcomes in immobilized, critically ill elderly subjects. RESULTS: Audit A included 170 patients (86.3+/-6.1 years old) and audit B, 232 patients (86.3+/-6.3), respectively 20.6% and 31.4% of the hospitalized population. Misclassifications occurred in A in 54.0% compared to 34.05% in B (P < 0.001). 32.6% in A versus 86.9% in B adequately received oral supplements (P = 0.02). Significant risk factors for the adverse outcomes in the combined two audits were: dementia (RR: 1.8, 95%CI: 1.0 to 3.0, P= 0.04) and dehydration (RR: 2.0, 95%CI:1.0 to 4.1, P= 0.05) for pressure ulcer incidence; stroke (RR: 8.8, 95%CI: 4.8 to 16.0, P < 0.001) for pressure ulcer prevalence at discharge; neoplasms (RR: 1.1, 95%CI: 1.0 to 1.2, P = 0.02) for nosocomial infections; bladder indwelling for urinary tract infections (RR: 4.8, 95%CI: 2.9 to 7.7, P<< 0.001); swallowing problems for pulmonary infections (RR: 5.4, 95%CI: 2.8 to 10.5, P < 0.001); venous indwelling for septicaemia (RR: 5.4, 95%CI: 1.3 to 23. 3, P= 0.02). However, after adjustment on significant risk factors, the outcome rate was similar in audit B: death rate: A (15.6%), B (14.2%); length of stay: A (17.3+/-10.4 days), B (17.4+/-10.0); pressure ulcer incidence: A (26.4%), B (20.2%), (83% were erythema); pressure ulcer prevalence at discharge: A (14.7%), B (10.3%), (40% were erythema); nosocomial infections: A (26.4%), B (19.0%). CONCLUSION: The improvement of malnutrition recognition and nutritional support was not followed by a perceptible decrease in adverse outcome rate, this latter being mainly related to the underlying conditions of these critically ill elderly patients.

Primary trigeminal afferents to the vestibular nuclei in the rat: existence of a collateral projection to the vestibulo-cerebellum.

Projections from the mesencephalic trigeminal nucleus to the vestibular nuclei were analyzed using retrograde and anterograde tracing methods. The results show that neurons in the caudal part of the trigeminal mesencephalic nucleus project mainly to the medial, inferior and lateral vestibular nuclei and moderately to the peripheral part of the superior vestibular nucleus. Using the double-labeling technique we demonstrate that individual neurons of the mesencephalic nucleus send collaterals to the vestibular nuclei and the vestibulo-cerebellum. These results suggest that these anatomical connections are involved in mechanisms of eye-head coordination.

Audit of percutaneous endoscopic gastrostomy in long-term enteral feeding in a nursing home.

OBJECTIVES: Percutaneous endoscopic gastrostomy (PEG) is now easily used in the event of long-term enteral nutrition. Tolerance of long-term enteral feeding has been documented in different populations but the documentation is incomplete in the case of older and frail people. Our aim was to describe early and late tolerance in this population, and to propose ways in which it could be improved. DESIGN: Retrospective study in two parts: tolerance and quality of care; case-control study for tolerance. SETTING: A nursing home with 240 beds in south-west France. who had undergone PEG insertion between January 1990 and June 1994. Fifty-eight patients were involved, 12 under 65 years (48 +/- 10.6), and 46 over 65 (80.7 +/- 9.3). The gastrostomy insertion was performed because of a vegetative state in 6 patients, swallowing difficulties in 31 and anorexia in 21. A control group was gathered in December 1996, which included all patients for whom the question of nutritional support was mentioned books but where no artificial nutrition had been implemented due to the patients' or families' refusal or to a staff decision. This group included 50 patients, 5 younger than 65 years (54 +/- 8.3), and 45 older (84.7 +/- 7.6). In 22 cases the nutritional problem was swallowing difficulties and in 28 cases anorexia. Pressure ulcers were present before insertion in 34 patients in the PEG group and in 7 of the control group (p < 0.001). MAIN OUTCOME MEASURES: Prognosis, early and late cutaneous digestive (ileus, vomiting, gastroesophageal reflux) and pulmonary (bronchorrhea, dyspnea and aspiration pneumonia) complications for PEG and control groups, and patients with signs of poor behavioural tolerance of PEG were recorded in the chart. Audit of quality of care was performed in the PEG group using eight criteria: two concerned the pre-insertion period, two the early follow-up and four the long-term follow-up. RESULTS: Early mortality (4 weeks) was 13.8% in PEG (vs 10%, NS), mid-term mortality (between 4 and 8 weeks) was 12.1% (vs 14%, NS) and late mortality was 19.0% (vs 42.0%, length of follow-up 63.4 +/- 42.1 weeks compared to 53.1 +/- 63.8 weeks, NS). The duration of follow-up of the living patients was 71.6 +/- 61.8 weeks in PEG compared to 48.0 +/- 70.5 in the control group. Only 20% in PEG were free of any cutaneous complication around the insertion site, and 8 abscesses occurred during the first week. Pulmonary complications occurred in 39% of the PEG group (vs 30.0, NS). Aspiration pneumonia was significantly associated with swallowing difficulties in both groups (p < 0.05). Vomiting occurred for 15.5% of the PEG group (vs 12%, NS), ileus in 13.8% (vs 6%, NS). Gastroesophageal reflux was found in 2 PEG patients, compared to 1 case among the control patients. Pressures sores were healing in 20 out of 34 patients in the PEG group (vs 2 out of 7) and new ulcers appeared in 6 out of 24 (vs 8 out of 43). Fifteen (25.8%) of the PEG patients attempted to withdraw the tube.

Projection from trigeminal nuclei to neurons of the mesencephalic trigeminal nucleus in rat.

The mesencephalic trigeminal nucleus contains cell bodies of primary somatic sensory neurons that innervate the head region. The neurons resemble dorsal root ganglion cells but a striking difference is the presence of synaptic boutons in the nucleus. The present report demonstrates with anterograde tracers, the existence of a direct trigeminal projection from secondary sensory neurons of the principal and spinal nuclei to the mesencephalic nucleus. Our observations strongly suggest that synaptic contact may be established on the cell bodies as well as on the neurites of the mesencephalic neurons. These pathways could play a modulatory role in the processing of sensory afferent information and in the control of orofacial and/or oculomotor functions.

Development of retino-tectal arborizations in the trout.

In order to visualize the organization and the morphology of developing retinal axons in the trout (Oncorhynchus mykiss), HRP or DiI crystals were applied on the central part of the retina at different stages ranging from 21 days postfertilization (stage 27) to one month post-hatching (stage 36). Retinal axons and arborizations were observed on tectal whole mounts with a light microscope. The earliest stage investigated (stage 27) showed two groups of axons entering the tectum by its ventro-rostral part and extending in a dorso-caudal direction. As the tectum grows, these two groups separate to outline the dorsal and the ventral borders of the tectum. At three weeks post-hatching (stage 35) we observed three distinct brachia: the dorsal and ventral fascicles, and a small group in the middle that we called the intermediate fascicle. At hatching (stage 30), retinal axons start to arborize in the centre of the tectum. During the first month post-hatching, these axons migrate dorso-caudally and exhibit various morphologies. Until two weeks post-hatching (stage 34), they sprout a few long side branches, bearing numerous filopodial growth cones, in a phase of exploratory growth towards their target site. At stage 36, four types of terminal arborizations can be identified on the basis of their tangential and radial location in the tectum, and on their gross morphology. Three of these arbor types are already present at earlier stages and undergo refinements in their shape--reduction in their branching axes, loss of branches that are behind the terminal arborization, and the sprouting of more numerous branches at their extremities. These findings confirm that the widely branched arborizations are transient during development.

[Expression of vimentin and GFAP and development of the retina in the trout]. / Expression de la vimentine et de la GFAP et développement de la rétine chez la truite.

The glial cell development was studied during the edification of the retina and the optic tract, in a teleost, the rainbow trout. The intermediate filament proteins, vimentin and glial fibrillary acidic protein (GFAP) were visualized by an indirect immunohistochemical method. Results show that both vimentin and GFAP are early expressed in the developing retina and, particularly in the Müller cells, a coexpression of vimentin and GFAP is observed from embryonic to adult stages. The ganglion cell layer and the optic fiber layer both exhibit GFAP-positive structures. The deep staining for GFAP is also seen in the optic nerve and induces us to credit astrocyte-like cells with a leading role in the pattern formation of this tract.