Identification of RDH10, an All-trans Retinol Dehydrogenase, in Retinal Muller Cells

PURPOSE: To investigate the expression of RDH10, an all-trans retinol dehydrogenase identified in the retinal pigment epithelium (RPE), in retinal Muller cells. METHODS: The RDH10 protein levels in mouse eyecups and bovine tissues were examined by Western blot analysis using a polyclonal antibody against RDH10. The cellular localization in the retina was determined by immunohistochemistry. Expression of RDH10 in rMC-1, a cell line derived from rat Muller cells, was determined by RT-PCR and Western blot analysis. All-trans retinol dehydrogenase activity assays were performed using lysates from rMC-1 cells. The generation of all-trans retinal from tritiated all-trans retinol was analyzed by HPLC. RESULTS: RDH10, retinal G protein-coupled receptor (RGR), and RPE65 all had higher expression levels in the eyecups of BALB/c than in C57Bl/6 mice. In addition to the RPE, RDH10 was also detected at lower levels in the retina and liver. Immunohistochemistry showed that RDH10 was localized in Muller cells in retinal sections. RDH10 was detected in rMC-1 cells, at both the RNA and protein levels. The rat RDH10 cDNA containing the full-length coding region was cloned from rMC-1 cells. The rat RDH10 cDNA encodes a protein of 341 amino acids and shares 99% sequence identity with human, bovine, and mouse RDH10 at the amino acid level. In rMC-1 cells, all-trans retinol dehydrogenase activity was detected in the microsomal fraction. NADP was shown to be the preferred cofactor, which is identical with the cofactor preference of the recombinant RDH10. CONCLUSIONS: RDH10 was expressed in retinal Muller cells, in addition to the RPE. RDH10 generates all-trans retinal, which is the substrate for the photoisomerase RGR in Muller cells.     

Risk factors associated with delayed thyrotropin elevations in congenital hypothyroidism

OBJECTIVES: To identify risk factors associated with delayed thyrotropin elevations in cases of congenital hypothyroidism. To determine whether routine rescreening of babies who have very low birth weight (VLBW) and babies in the neonatal intensive care unit is justified. STUDY DESIGN: Retrospective review of the New England Newborn Screening database (January 1989-June 2002) of newborns screened for hypothyroidism to determine the incidence of congenital hypothyroidism associated with delayed thyrotropin elevations and to characterize features associated with delayed thyrotropin elevations in newborns with VLBW and non-VLBW (NVLBW). RESULTS: The incidence of hypothyroidism was 14-fold higher for newborns with VLBW (1:250) compared with newborns with NVLBW (1:3500). Of the newborns with VLBW, two thirds were not detectable on the initial screening specimen. Among newborns with VLBW with delayed thyrotropin elevation, iodine exposure was found in 23%. Among newborns with NVLBW, 45% had congenital cardiac anomalies. For every 20 NVLBW cases of congenital hypothyroidism detectable by initial screening specimen, one additional case was detected with delayed thyrotropin elevation. CONCLUSIONS: Routine rescreening of babies with VLBW and babies in the neonatal intensive care unit is justified, and particular attention to follow-up testing of newborns known to have cardiac disease is warranted.     

Caregiving and institutionalization of cognitively impaired older people: utilizing dynamic predictors of change

PURPOSE: The purpose of this study was to identify reliable predictors of nursing home entry over a 3-year period in a sample of 3,944 persons with dementia who resided in a home setting at baseline. Strengths of the analysis include a multiregional recruitment strategy, incorporation of salient caregiver characteristics, and a 3-year prospective design that allows for the modeling of change in important variables (e.g., care recipient functional status or caregiving indicators) when time to institutionalization is predicted. DESIGN AND METHODS: Data were derived from the control sample of the Medicare Alzheimer's Disease Demonstration Evaluation (MADDE). A Cox proportional hazards model was used to predict time to institutionalization among individuals with dementia (baseline was enrollment into MADDE). Predictors included care recipient demographics, caregiver demographics, and time-varying measurements of care recipient functional status, caregiving indicators, and service utilization. Indicators of change were also incorporated to capitalize on the prospective data available. RESULTS: Although several results were consistent with prior findings, caregiving indicators (i.e., burden and self-rated health) and community-based service use were significant predictors of earlier placement. Change in caregiver instrumental activities of daily living and care recipient activities of daily living were also related to expedited institutionalization. IMPLICATIONS: The findings emphasize the importance of incorporating both care recipient and caregiver function and service use patterns when targeting programs designed to prevent or delay institutionalization for people with dementia.     

Cerebrospinal fluid lactate and pyruvate concentrations and their ratio in children: age-related reference intervals

BACKGROUND: Lactate (L) and pyruvate (P) concentrations in cerebrospinal fluid (CSF) and the L/P ratio have diagnostic value in numerous primary and acquired disorders affecting the central nervous system, but age-related reference values are not available for children. METHODS: We analyzed CSF and blood lactate and pyruvate concentrations and their ratio in a 4-year retrospective survey of a children's hospital laboratory database. Reference intervals (10th-90th percentiles) were established from data on 197 hospitalized children. A recent regression modeling method was used to normalize and smooth values against age. The model equation of best fit was calculated for each variable. RESULTS: Slight age-related variations were shown by the model, with an increase in lactate, a decrease in pyruvate, and a resulting increase in the L/P ratio with increasing age. However, the SD did not vary with age. We defined the upper limit of the reference intervals as the 90th percentiles, which from birth to 186 months of age varied continuously from 1.78 to 1.88 mmol/L (6%), 148 to 139 micro mol/L (6%), and 16.9 to 19.2 (14%) for lactate, pyruvate, and the L/P ratio, respectively. At a threshold of 2 (in Z-score units), the sensitivity for a subgroup of inborn errors of metabolism (respiratory chain disorders) was 73%, 42%, and 31% for lactate, pyruvate, and the L/P ratio, respectively. CONCLUSIONS: In children, CSF lactate and pyruvate concentrations and their ratio appear to vary slightly with age. Average 90th percentile values of 1.8 mmol/L, 147 micro mol/L, and 17, respectively, could be used in infants up to 24 months of age. In older children, age-adjusted reference intervals should be used, especially when values are close to the 90th percentile.     

Modes of organising at two health services organizations: a case study approach

This paper applies a case study methodology to examine the development of two distinct models of organising allied health professionals within two health service organizations. In particular, it explores options in modes of organising. Case study data reflected that in one case a single stakeholder entity was achieved through the development of quasi-shareholder roles for allied health discipline leaders. In contrast, the second case included multiple small weak stakeholders who had competing visions regarding both identity and resource allocation. The emergence of these two distinct forms of organising within allied health has implications for policy and practice.     

Correlation of regenerable opsin with rod ERG signal in Rpe65-/- mice during development and aging

PURPOSE: RPE65 has been shown to be essential for the production of 11-cis retinal by the retinal pigment epithelium. Mutations in RPE65 are known to be associated with severe forms of early-onset retinal dystrophy. This project was designed to determine the amount of regenerable opsin in Rpe65-/- mice during development and aging, and to examine the function of this rhodopsin by electroretinography (ERG). METHODS: Young and aged Rpe65-/- and wild-type (WT) mice were dark adapted. Endogenous rhodopsin and regenerable opsin were measured using absorption-difference spectrophotometry. Photoreceptor function was assessed with scotopic single-flash ERGs and photoreceptors were counted in histologic sections. Opsin's primary structure was analyzed by mass-spectrometric mapping. RESULTS: Unlike WT mice, amounts of regenerable opsin in Rpe65-/- mice decreased significantly with age, which correlated with a decrease in the number of photoreceptors and a decline in ERG amplitudes. Opsin structure, however, did not change. No endogenous levels of rhodopsin were measurable in the Rpe65-/- mice (detection limit: 0.225 pmol). 11-cis Retinal injections resulted in the regeneration of similar amounts of rhodopsin and improved rod function in a comparable way, irrespective of age. CONCLUSIONS: In the aged Rpe65-/- mouse, opsin levels decrease because of the loss of photoreceptors. The remaining opsin is structurally intact, and the components of the phototransduction cascade and the retinal circuitry remain functional, despite the absence of normal photoreceptor activity.     

Role of specific amino acids in nutritional support

Attempts have been made over the past decade to evaluate the role of specific amino acids in the nutritional support of surgical patients. Particular attention has been paid to the branched-chain amino acids, glutamine, and a collection of compounds that have been referred to as 'immunonutrients'. The present review provides an overview of the rationale behind the use of these nutrients and reviews information about their role in patients undergoing surgery. In general, although the use of immunonutrients enhances the nutritional status of patients, and although a number of clinical trials have claimed clinical advantages, there are still doubts about their clinical utility and concerns about their high cost.