Combining TP53 mutation and isoform has the potential to improve clinical practice

The clinical importance of assessing and combining data on TP53 mutations and isoforms is discussed in this article. It gives a succinct overview of the structural makeup and key biological roles of the isoforms. It then provides a comprehensive summary of the roles that p53 isoforms play in cancer development, therapy response and resistance. The review provides a summary of studies demonstrating the role of p53 isoforms as potential prognostic indicators. It further provides evidence on how the presence of TP53 mutations may affect one or more of these activities and the association of p53 isoforms with clinicopathological data in various tumour types. The review gives insight into the present diagnostic hurdles for identifying TP53 isoforms and makes recommendations to improve their evaluation. In conclusion, this review offers suggestions for enhancing the identification and integration of TP53 isoforms in conjunction with mutation data within the clinical context.

Frequency of Defecation and Form of Stool among General Bangladeshi Population

Data on stool form and defecation frequency which are a prerequisite for defining normal bowel habit are lacking in Bangladesh. This observational cross sectional study was designed to find out defecation frequency and stool form among general population in Bangladesh. This study was performed in the Department of Gastroenterology, Shaheed Suhrawardy Medical College Hospital, Dhaka, Bangladesh from July 2017 to June 2018. Apparently healthy 1090 respondents were evaluated for predominant stool form (Bristol chart) and frequency. Data on demographic and life-style were collected. The study population consisted of 1090 respondents, among them, 65.13% male and 34.87% female and mean age of them was 40.20±12.39 years. Most of the people 874(80.2%) passed stool between 12-14 times per week followed by 111(10.2%) less than 3 stools per week, 95(8.7%) passed more than 14 stools per week and 10(0.9%) between 3-12 stools per week, p<0.001. Most people passed predominantly Bristol type IV stool- 610(56.0%); followed by type III- 274(25.1%). Other stool forms were: type I- 52(4.8%), type II- 59(5.4%), type V- 31(2.8%), type VI- 33(3.0%), type VII- 31(2.8%), p<0.001. In regard to the physical activity, most of the respondents (70.0%) are physically active whereas about 13.0% are sedentary and about 17.0% are physically intermediate between the two, p<0.001. In the case of dietary habit, most of the participants are non-vegetarian (82.5%) and the remaining are vegetarian (11.1%) and occasional non vegetarian (6.4%), p<0.001. Median stool frequency in the studied population was 14 per week and predominant form was Bristol type IV. Older age was associated with lesser stool frequency, particularly among female subjects.

Vascular Endothelial Growth Factor Expression in Colorectal Adenocarcinoma of Resected Samples and its Association with Histological Grade and Pathological Stage

Colorectal carcinoma (CRC) is one of the major public health problems. Vascular endothelial growth factor (VEGF) is an effective angiogenic factor and plays a pivotal role in the development, progression and metastasis of CRC. It also could further help in selecting patients of high risk of disease progression for adjuvant therapy. Therefore, this study was undertaken to reveal the importance of angiogenic factor (VEGF) as an adjunctive tool with histologic parameters of CRC. Total 45 cases were included in this cross-sectional observational study, performed in the department of Pathology, Mymensingh Medical College, Mymensingh and Immunohistochemistry was done in the department of Pathology, Bangabandhu Sheikh Mujib Medical University, Dhaka, Bangladesh from March 2019 to February 2021. All the cases were evaluated for VEGF immunohistochemical expression. Majority of cases were low grade adenocarcinoma (86.9%) and most common stage was stage III (48.9%). Among 45 cases collectively 13 (4-negative + 9-weak positive) cases were low for VEGF expression and 32 (22-moderate positive + 10-strong positive) cases were high for VEGF expression. Statistically significant association was found with VEGF expression and increasing tumor stage as well as with lymph node metastasis (p<0.05). VEGF had positive significant correlation with stage (r=0.322; p=0.031) of tumor. However, no correlation with VEGF expression and grade (r=0.219; p=0.149) and other clinicopathological parameters of tumor was seen.

Role of Nuclear Morphometry in the Cytologic Evaluation of Benign and Malignant Breast Lesions

Breast cancer is the most common diagnosed cancer in female over the world. It is the most important cause of 'cancer death' among female. For diagnosis of breast masses the Fine needle aspiration cytology (FNAC) is applied as the primary tool. Though it is an easy, rapid and comparatively minimally invasive and inexpensive procedure for quick diagnosis, it is largely a subjective tool. Computer-assisted image morphometry provides a new influential method for high-precision measurement of nuclear features and can help to differentiate between benign and malignant breast aspirates. Therefore, the aim of study was to evaluate computer assisted semi-automatic nuclear morphometry on cytology of breast lesions to differentiate benign and malignant lesions of breast. Total 70 cases were included in this cross sectional study, performed in the department of Pathology, Mymensingh Medical College, Mymensingh, Bangladesh from March 2019 to February 2021. Morphometric analysis was done on images captured from FNAC slides of the selected cases. Image J Morphometric Software was used for image analysis. Statistical analysis was done by using SPSS 26.0 version. On analysis of morphometry, four nuclear size parameters, two nuclear shape parameters and one nuclear chromasia parameter were measured. The cut-off values with sensitivity and specificity between benign and malignant category for mean nuclear area were 61.54μm², 91.0%, 97.0%, for mean maximum feret diameter 10.89μm, 94.0%, 95.0%, for mean minimum feret diameter 7.71μm, 94.0%, 97.0% and for mean nuclear perimeter 33.32μm, 94.0%, 95.0% respectively. So, in this observation, morphometry is adjunctive tools which may overcome the limitations of inter observer agreement, improve diagnostic accuracy and avoid unnecessary repeat Fine Needle Aspiration (FNA) in breast aspirates.

Tau pathology mediates age effects on medial temporal lobe structure

Hippocampal atrophy is endemic in 'normal aging' but it is unclear what factors drive age-related changes in medial temporal lobe (MTL) structural measures. We investigated cross-sectional (n = 191) and longitudinal (n = 164) MTL atrophy patterns in cognitively normal older adults from ADNI-GO/2 with no to low cerebral β-amyloid and assessed whether white matter hyperintensities (WMHs) and cerebrospinal fluid (CSF) phospho tau (p-tau) levels can explain age-related changes in the MTL. Age was significantly associated with hippocampal volumes and Brodmann Area (BA) 35 thickness, regions affected early by neurofibrillary tangle pathology, in the cross-sectional analysis and with anterior and/or posterior hippocampus, entorhinal cortex and BA35 in the longitudinal analysis. CSF p-tau was significantly associated with hippocampal volumes and atrophy rates. Mediation analyses showed that CSF p-tau levels partially mediated age effects on hippocampal atrophy rates. No significant associations were observed for WMHs. These findings point toward a role of tau pathology, potentially reflecting Primary Age-Related Tauopathy, in age-related MTL structural changes and suggests a potential role for tau-targeted interventions in age-associated neurodegeneration and memory decline.

Pathological drivers of neurodegeneration in suspected non-Alzheimer's disease pathophysiology

Background

Little is known about the heterogeneous etiology of suspected non-Alzheimer’s pathophysiology (SNAP), a group of subjects with neurodegeneration in the absence of β-amyloid. Using antemortem MRI and pathological data, we investigated the etiology of SNAP and the association of neurodegenerative pathologies with structural medial temporal lobe (MTL) measures in β-amyloid-negative subjects.

Methods

Subjects with antemortem MRI and autopsy data were selected from ADNI (n=63) and the University of Pennsylvania (n=156). Pathological diagnoses and semi-quantitative scores of MTL tau, neuritic plaques, α-synuclein, and TDP-43 pathology and MTL structural MRI measures from antemortem T1-weighted MRI scans were obtained. β-amyloid status (A+/A−) was determined by CERAD score and neurodegeneration status (N+/N−) by hippocampal volume.

Results

SNAP reflects a heterogeneous group of pathological diagnoses. In ADNI, SNAP (A−N+) had significantly more neuropathological diagnoses than A+N+. In the A− group, tau pathology was associated with hippocampal, entorhinal cortex, and Brodmann area 35 volume/thickness and TDP-43 pathology with hippocampal volume.

Conclusion

SNAP had a heterogeneous profile with more mixed pathologies than A+N+. Moreover, a role for TDP-43 and tau pathology in driving MTL neurodegeneration in the absence of β-amyloid was supported.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13195-021-00835-2.

Work Ability among Nurses in a Public Medical College Hospital

This cross sectional study was carried out 197 nurses of Shaheed Suhrawardy Medical College Hospital (ShSMCH), Dhaka, Bangladesh from 1st July 2015 to 30th June 2016. Purpose of the study was to assess work ability and its association with sociodemographic characteristics & work related variables which affect work ability among nurses in a Public Medical College Hospital. Sampling method was simple random sampling. By face to face interview data was collected with the help of semi-structured questionnaire and all data were analyzed with SPSS software version 21. For descriptive statistics means, SD and range were calculated as required. Data were presented in frequency table, pie diagram. Statistical test chi-square was used and p<0.05 was consider to be statistically significant. It was found that 136(69%) respondents were between the age of 21 to 39 years and mean age was 35.95 Years, 187(94.9%) were female, 156(79.2%) were Muslim, 166(84.3%) had Diploma, 180(91.4%) family income were equal to and more than 40,000 Tk. 189(95.5%) had done clinical work; 49(24.9%) worked at medicine. Majority 183(92.9%) respondents had good to excellent work ability and 14(7.1%) had less good work ability. In this study significant association (p<0.05) was found between work ability and gender, educational status and type of job. This research provides an initial step in understanding the work ability of nurses in a Public Medical College Hospital. The present study showed that nurses' work ability is at the good to excellent level. This study also reveals significant association between work ability and gender, educational status and type of job.

Comparison of In Vivo and Ex Vivo MRI of the Human Hippocampal Formation in the Same Subjects

Multiple techniques for quantification of hippocampal subfields from in vivo MRI have been proposed. Linking in vivo MRI to the underlying histology can help validate and improve these techniques. High-resolution ex vivo MRI can provide an intermediate modality to map information between these very different imaging modalities. This article evaluates the ability to match information between in vivo and ex vivo MRI in the same subjects. We perform rigid and deformable registration on 10 pairs of in vivo (3 T, 0.4 × 0.4 × 2.6 mm3) and ex vivo (9.4 T, 0.2 × 0.2 × 0.2 mm3) scans, and describe differences in MRI appearance between these modalities qualitatively and quantitatively. The feasibility of using this dataset to validate in vivo segmentation is evaluated by applying an automatic hippocampal subfield segmentation technique (ASHS) to in vivo scans and comparing SRLM (stratum/radiatum/lacunosum/moleculare) surface to manual tracing on corresponding ex vivo scans (and in 2 cases, histology). Regional increases in thickness are detected in ex vivo scans adjacent to the ventricles and were not related to scanner, resolution differences, or susceptibility artefacts. Satisfactory in vivo/ex vivo registration and subvoxel accuracy of ASHS segmentation of hippocampal SRLM demonstrate the feasibility of using this dataset for validation, and potentially, improvement of in vivo segmentation methods.

Defining SNAP by cross-sectional and longitudinal definitions of neurodegeneration

Introduction

Suspected non-Alzheimer's pathophysiology (SNAP) is a biomarker driven designation that represents a heterogeneous group in terms of etiology and prognosis. SNAP has only been identified by cross-sectional neurodegeneration measures, whereas longitudinal measures might better reflect “active” neurodegeneration and might be more tightly linked to prognosis. We compare neurodegeneration defined by cross-sectional ‘hippocampal volume’ only (SNAP/L−) versus both cross-sectional and longitudinal ‘hippocampal atrophy rate’ (SNAP/L+) and investigate how these definitions impact prevalence and the clinical and biomarker profile of SNAP in Mild Cognitive Impairment (MCI).

Methods

276 MCI patients from ADNI-GO/2 were designated amyloid “positive” (A+) or “negative” (A−) based on their florbetapir scan and neurodegeneration ‘positive’ or ‘negative’ based on cross-sectional hippocampal volume and longitudinal hippocampal atrophy rate.

Results

74.1% of all SNAP participants defined by the cross-sectional definition of neurodegeneration also met the longitudinal definition of neurodegeneration, whereas 25.9% did not. SNAP/L+ displayed larger white matter hyperintensity volume, a higher conversion rate to dementia over 5 years and a steeper decline on cognitive tasks compared to SNAP/L− and the A- CN group. SNAP/L− had more abnormal values on neuroimaging markers and worse performance on cognitive tasks than the A- CN group, but did not show a difference in dementia conversion rate or longitudinal cognition.

Discussion

Using a longitudinal definition of neurodegeneration in addition to a cross-sectional one identifies SNAP participants with significant cognitive decline and a worse clinical prognosis for which cerebrovascular disease may be an important driver.

•

74.1% of SNAP subjects also met the criteria for longitudinal neurodegeneration (L+).

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SNAP/L+ had a larger WMH volume compared to the SNAP/L− group and the A- CN group.

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SNAP/L+ showed a higher conversion rate and steeper cognitive decline than A- CN.

•

SNAP/L− showed similar conversion rate and cognitive decline as A- CN.

Mapping of pain circuitry in early post-natal development using manganese-enhanced MRI in rats

Premature or ill full-term infants are subject to a number of noxious procedures as part of their necessary medical care. Although we know that human infants show neural changes in response to such procedures, we know little of the sensory or affective brain circuitry activated by pain. In rodent models, the focus has been on spinal cord and, more recently, midbrain and medulla. The present study assesses activation of brain circuits using manganese-enhanced magnetic resonance imaging (MEMRI). Uptake of manganese, a paramagnetic contrast agent that is transported across active synapses and along axons, was measured in response to a hindpaw injection of dilute formalin in 12-day-old rat pups, the age at which rats begin to show aversion learning and which is roughly the equivalent of full-term human infants. Formalin induced the oft-reported biphasic response at this age and induced a conditioned aversion to cues associated with its injection, thus demonstrating the aversiveness of the stimulation. Morphometric analyses, structural equation modeling and co-expression analysis showed that limbic and sensory paths were activated, the most prominent of which were the prefrontal and anterior cingulate cortices, nucleus accumbens, amygdala, hypothalamus, several brainstem structures, and the cerebellum. Therefore, both sensory and affective circuits, which are activated by pain in the adult, can also be activated by noxious stimulation in 12-day-old rat pups.

A protocol for manual segmentation of medial temporal lobe subregions in 7 Tesla MRI

Recent advances in MRI and increasing knowledge on the characterization and anatomical variability of medial temporal lobe (MTL) anatomy have paved the way for more specific subdivisions of the MTL in humans. In addition, recent studies suggest that early changes in many neurodegenerative and neuropsychiatric diseases are better detected in smaller subregions of the MTL rather than with whole structure analyses. Here, we developed a new protocol using 7 Tesla (T) MRI incorporating novel anatomical findings for the manual segmentation of entorhinal cortex (ErC), perirhinal cortex (PrC; divided into area 35 and 36), parahippocampal cortex (PhC), and hippocampus; which includes the subfields subiculum (Sub), CA1, CA2, as well as CA3 and dentate gyrus (DG) which are separated by the endfolial pathway covering most of the long axis of the hippocampus. We provide detailed instructions alongside slice-by-slice segmentations to ease learning for the untrained but also more experienced raters. Twenty-two subjects were scanned (19-32 yrs, mean age = 26 years, 12 females) with a turbo spin echo (TSE) T2-weighted MRI sequence with high-resolution oblique coronal slices oriented orthogonal to the long axis of the hippocampus (in-plane resolution 0.44 × 0.44 mm2) and 1.0 mm slice thickness. The scans were manually delineated by two experienced raters, to assess intra- and inter-rater reliability. The Dice Similarity Index (DSI) was above 0.78 for all regions and the Intraclass Correlation Coefficients (ICC) were between 0.76 to 0.99 both for intra- and inter-rater reliability. In conclusion, this study presents a fine-grained and comprehensive segmentation protocol for MTL structures at 7 T MRI that closely follows recent knowledge from anatomical studies. More specific subdivisions (e.g. area 35 and 36 in PrC, and the separation of DG and CA3) may pave the way for more precise delineations thereby enabling the detection of early volumetric changes in dementia and neuropsychiatric diseases.

Automated Hippocampal Subfield Segmentation at 7T MRI

BACKGROUND AND PURPOSE

High resolution 7T MRI is increasingly used to investigate hippocampal subfields in vivo, but most studies rely on manual segmentation which is labor intensive. We aimed to evaluate an automated technique to segment hippocampal subfields and the entorhinal cortex at 7T MRI.

MATERIALS AND METHODS

The cornu ammonis (CA)1, CA2, CA3, dentate gyrus, subiculum, and entorhinal cortex were manually segmented, covering most of the long axis of the hippocampus on 0.70-mm(3) T2-weighted 7T images of 26 participants (59 ± 9 years, 46% men). The automated segmentation of hippocampal subfields approach was applied and evaluated by using leave-one-out cross-validation.

RESULTS

Comparison of automated segmentations with corresponding manual segmentations yielded a Dice similarity coefficient of >0.75 for CA1, the dentate gyrus, subiculum, and entorhinal cortex and >0.54 for CA2 and CA3. Intraclass correlation coefficients were >0.74 for CA1, the dentate gyrus, and subiculum; and >0.43 for CA2, CA3, and the entorhinal cortex. Restricting the comparison of the entorhinal cortex segmentation to a smaller range along the anteroposterior axis improved both intraclass correlation coefficients (left: 0.71; right: 0.82) and Dice similarity coefficients (left: 0.78; right: 0.77). The accuracy of the automated segmentation versus a manual rater was lower, though only slightly for most subfields, than the intrarater reliability of an expert manual rater, but it was similar to or slightly higher than the accuracy of an expert-versus-manual rater with ∼170 hours of training for almost all subfields.

CONCLUSIONS

This work demonstrates the feasibility of using a computational technique to automatically label hippocampal subfields and the entorhinal cortex at 7T MRI, with a high accuracy for most subfields that is competitive with the labor-intensive manual segmentation. The software and atlas are publicly available: http://www.nitrc.org/projects/ashs/.

Compact panicle architecture is detrimental for growth as well as sucrose synthase activity of developing rice kernels

The increase of spikelet number in the panicles of modern super rice has made the architecture compact, as the extra spikelets are accommodated mostly on secondary branches than on primary branches. However, the grain yield did not improve because of poor grain filling, which was more visible in the basal spikelets than apical spikelets. The objective of this study was to examine the effect of the compactness and positional difference of spikelets in the panicle on grain filling by comparing the activity and genetic expression of starch synthesising enzymes in the developing kernels of lax-(Upahar and CR3856-45-11-2-7-2-5 (CR-45)) and compact-(Mahalaxmi and CR3856-29-14-2-1-1-1 (CR-29)) panicle cultivars. Upahar and Mahalaxmi are genetically related, whereas CR-45 and CR-29 are recombinant inbred lines. The grain carbohydrate concentration and activity of sucrose synthase (SUS) enzyme were estimated during the active period of grain filling. Further, expression of isoforms of SUS, ADP glucose pyrophosphorylase (APL and APS for large and small units respectively) and starch synthase (SS and GBSS for soluble and granule bound starch synthases respectively) were also assayed through PCR studies. The genotype approach used revealed grain SUS activity and starch concentration high and sugar concentration low in the lax- compared with compact-panicle cultivars and in the apical spikelets compared with basal ones. The margin of variation between apical and basal spikelets was higher in the compact- than the lax-panicle cultivars. Genetic expression of most of the isoforms of the enzymes was higher in the lax- than the compact-panicle cultivars as seen in RT-PCR studies. A quantitative appraisal of transcript levels of isoforms in the qRT-PCR identified greater expression of SUS3 in the basal spikelets of Upahar than that in Mahalaxmi and in CR-45 over CR-29, most prominently during the active period of grain filling. We conclude that proximal location as well as increased density of spikelets on panicles affected SUS3 expression in the basal spikelets. The metabolic dominance of a spikelet in rice panicle is dependent on the expression of the genes for different isoforms of starch synthesising enzymes, but the expression of SUS3 could be more specific than the others. SUS3 expression is most active during grain filling of the lax-panicle cultivars, but its dominance is reduced significantly in the kernels of the compact-panicle cultivars.

Haemagglutinin mutations and glycosylation changes shaped the 2012/13 influenza A(H3N2) epidemic, Houston, Texas

While the early start and higher intensity of the 2012/13 influenza A virus (IAV) epidemic was not unprecedented, it was the first IAV epidemic season since the 2009 H1N1 influenza pandemic where the H3N2 subtype predominated. We directly sequenced the genomes of 154 H3N2 clinical specimens collected throughout the epidemic to better understand the evolution of H3N2 strains and to inform the H3N2 vaccine selection process. Phylogenetic analyses indicated that multiple co-circulating clades and continual antigenic drift in the haemagglutinin (HA) of clades 5, 3A, and 3C, with the evolution of a new 3C subgroup (3C-2012/13), were the driving causes of the epidemic. Drift variants contained HA substitutions and alterations in the potential N-linked glycosylation sites of HA. Antigenic analysis demonstrated that viruses in the emerging subclade 3C.3 and subgroup 3C-2012/13 were not well inhibited by antisera generated against the 3C.1 vaccine strains used for the 2012/13 (A/Victoria/361/2011) or 2013/14 (A/Texas/50/2012) seasons. Our data support updating the H3N2 vaccine strain to a clade 3C.2 or 3C.3-like strain or a subclade that has drifted further. They also underscore the challenges in vaccine strain selection, particularly regarding HA and neuraminidase substitutions derived during laboratory passage that may alter antigenic testing accuracy.

Caste variation in the distribution of placental alkaline phosphatase genes among the Hindus of West Bengal

798 placentas (Brahmin 141, Kayastha 303, Mahishya 91 and mixed low castes 263), from Calcutta hospitals, have been studied by starch gel electrophoresis for alkaline phosphatase types. The estimated gene-frequencies resemble those found else-where in caucasoid populations. Statistically significant differences (P approximately 0.02) were, however, noticed between the broadly divided upper caste group (Brahmin and Kayastha) and the lower caste group (Mahishya and mixed low castes) in respect of Plf 1 and Pls 1) gene distributions. The upper caste group has higher Plf 1 and lower Pls 1 frequencies than the lower caste group. The two broad caste groups are, however, quite uniform in Pli 1 distribution. All the six common phenotypes (S1, F1, I 1, S1F1, S1 I 1 and F1 I 1) and seven rare phenotypes (S1S2, S1S3, F1F2, F1S2, F2S1, F1S3 and I 1S2) were found.

The effect of parity on placental weight and birth weight: Interaction with placental alkaline phosphatase polymorphism

The effect of parity on placental weight and birth weight is examined through a series of birth records from an Indian population in Calcutta. Placental weight and birth weight increase with parity, the maximum increment occurring between parities 1 and 2. This is compatible with a hypothesis of sensitization of the mother to foetal, paternally derived, antigens. The three common placental alkaline phosphatase enzymic genotypes have no effect on determining foetal development.

Mortality prediction in adult cardiac surgery patients: comparison of two risk stratification models

OBJECTIVE

To assess and compare the two commonly applied models--EuroSCORE and Parsonnet--in our local adult cardiac surgery patients, according to risk factor quantification related to mortality using a risk stratification protocol to assess the quality of cardiac surgical care.

DESIGN

Prospective study.

SETTING

Cardiac surgery centre in a regional hospital in Hong Kong.

PATIENTS

All adult patients undergoing coronary artery bypass graft and heart valve surgery at the Grantham Hospital were evaluated prospectively from November 1999 to July 2005.

MAIN OUTCOME MEASURES

In-hospital mortality was the defined end-point. Statistical analyses consisted of observed against expected mortality, Hosmer-Lemeshow goodness-of-fit test for calibration accuracy, and receiver operating characteristic curve for discrimination performance.

RESULTS

During the study period, 1247 patients underwent coronary artery bypass graft surgery and 1406 underwent heart valve surgery. Observed mortality rates in these two patient groups were 2.9% and 4.8% respectively. The expected mortality rates as predicted by the EuroSCORE were (mean+/-standard deviation) 4.0+/-3.3% and 5.2+/-3.0% respectively, and by the Parsonnet model were 5.9+/-4.2% and 7.3+/-4.4% respectively. EuroSCORE performed better than the Parsonnet model at predicting in-hospital mortality assessed by the Hosmer-Lemeshow goodness-of-fit test. The areas under the receiver operating characteristic curves in coronary artery bypass graft surgery were 0.76 for EuroSCORE and 0.74 for Parsonnet. The receiver operating characteristic curve areas in valve surgery were 0.77 for EuroSCORE and 0.79 for Parsonnet.

CONCLUSION

Despite significant geographic and demographic differences between European and Asian patients, in our local adult cardiac surgery patients, the EuroSCORE performed well with good calibration and discrimination in predicting mortality. There was a tendency for both models to over predict. However, the EuroSCORE can serve as a baseline for the development of a local risk model.

A prospective evaluation of the effect of atazanavir on the QTc interval and QTc dispersion in HIV-positive patients

BACKGROUND

Atazanavir (ATV), an HIV protease inhibitor (PI) that may be preferred for the treatment of HIV-infected patients with cardiovascular comorbidities because of its favourable effects on plasma lipids, has been associated with cardiac rhythm disturbances.

OBJECTIVE

To quantify the effect of ATV on corrected QT (QTc) and QTc dispersion (QTd), markers of the potential for cardiac dysrhythmia, in patients switching from other PIs to ATV.

METHODS

In this prospective, single-centre, open-label study, 12-lead electrocardiograms were performed for subjects at baseline, 2 h after the first dose of ATV, and 1 month after initiation of ATV.

RESULTS

Twenty-one patients (19 received ritonavir-boosted ATV) completed the study. There was a trend towards an increase in the QTc at 2 h after the first dose [mean+/-standard deviation 3.19+/-8.0 ms; 95% confidence interval (CI) -0.47 to 6.85 ms; P=0.084]. There was no difference between QTc values at baseline and at 1 month (-1.5+/-8.75 ms; 95% CI -5.50 to 2.46; P=0.43). There was a nonsignificant decrease in the QTd between baseline and 2 h (-5.1+/-15.19 ms; 95% CI -13.22 to 2.96; P=0.197) and between baseline and 1 month (-0.61+/-15.04 ms; 95% CI -8.1 to 6.87; P=0.865). A significant increase in the PR interval (7.4+/-10.7 ms; 95% CI 2.5 to 12.25 ms; P=0.005) was observed at 1 month.

CONCLUSIONS

The use of ATV did not result in increases in the QTc interval or QTd. However, PR interval monitoring may be warranted in patients with underlying heart block or those treated with atrioventricular nodal blocking agents.

Mandibular invasion in oral squamous cell carcinoma: investigation by clinical examination and orthopantomogram

Assessing the relationship of oral squamous carcinoma with the mandible prior to definitive therapy poses a perplexing problem for the head and neck oncologist. We carried out a prospective open study of 51 (21 female and 30 male; mean age of 53.4 years) patients undergoing mandibular resections for oral squamous cell carcinoma to examine the incidence of mandibular bone invasion and to assess the predictive capabilities of clinical and radiological examination in detecting bone involvement. A detailed clinical examination was followed by radiographic evaluation of mandible for bone invasion. After resection, the mandible was sectioned serially at every cm to find the pathological bone involvement. Sensitivity, specificity, and positive and negative predictive values of clinical and radiological findings were calculated. Specimens from 25 patients (49%) (4 segmental 21 hemi) demonstrated tumour invasion on histological examination. Clinical impression of mandibular invasion showed a sensitivity of 96% and specificity of 65%, whereas radiological examination had a sensitivity of 92% and specificity of 88%. When considered together, clinical and radiological examinations were able to detect all the cases of bone invasion, but specificity was only 58%. This study advocates careful correlation of clinical and radiological findings prior to definitive therapy, as clinical examination tends to over diagnose bone invasion in tumours adjacent to the mandible. The specificity of imaging was also found to be low pointing towards the need for more specific diagnostic tools in doubtful cases. Aggressive surgical therapy, namely segmental or hemi resection of mandible is warranted in case of tumours of the lower alveolus with definite bone invasion. In case of carcinomas of the buccal mucosa and tongue the mandibular resection can be limited to that required for clearance of margins provided the radiology is negative.

Use of telemedicine in evading cholera outbreak in Mahakumbh Mela, Prayag, UP, India: an encouraging experience

Telemedicine (TM) services a process in which expert medical advice from afar is provided using electronic signals to transfer the medical data from one site to another. As a pilot project to assess the efficacy of TM in developing countries like India, a telemedicine center was set up at the main hospital of Mahakumbh mela--a grand religious fair, at Prayag, a city in north India. The daily reporting of the in-patient and outpatient cases at the fair revealed a surge of diarrhea cases among the pilgrims at the fair. This information was communicated to the referral center at Sanjay Gandhi Post Graduate Institute of Medical Sciences (SGPGIMS), which, with the help of its microbiology department, conducted microbiological examinations of stool samples and rectal swabs of patients along with various water samples. Vibrio cholerae was isolated in 22.6% (7/31) of the samples. This information was immediately relayed to the Main Hospital at the fair online, and then to the health authorities, who took strict and prompt measures to improve hygiene. Subsequently, the number of diarrhea cases decreased considerably in a matter of a few days, and thus an epidemic disaster was averted, which could have created havoc in such a large gathering.

The ORF3 protein of hepatitis E virus binds to Src homology 3 domains and activates MAPK

The hepatitis E virus (HEV) is the causative agent of hepatitis E, an acute form of viral hepatitis. The biology and pathogenesis of HEV remain poorly understood. We have used in vitro binding assays to show that the HEV ORF3 protein (pORF3) binds to a number of cellular signal transduction pathway proteins. This includes the protein tyrosine kinases Src, Hck, and Fyn, the p85alpha regulatory subunit of phosphatidylinositol 3-kinase, phospholipase Cgamma, and the adaptor protein Grb2. A yeast two-hybrid assay was used to further confirm the pORF3-Grb2 interaction. The binding involves a proline-rich region in pORF3 and the src homology 3 (SH3) domains in the cellular proteins. Competition assays and computer-assisted modeling was used to evaluate the binding surfaces and interaction energies of the pORF3.SH3 complex. In pORF3-expressing cells, pp60(src) was found to associate with an 80-kDa protein, but no activation of the Src kinase was observed in these cells. However, there was increased activity and nuclear localization of ERK in the pORF3-expressing cells. These studies suggest that pORF3 is a viral regulatory protein involved in the modulation of cell signaling. The ORF3 protein of HEV appears to be the first example of a SH3 domain-binding protein encoded by a virus that causes an acute and primarily self-limited infection.

Cyclosporine A-induced mammary hyperplasia and hyperprolactinemia in New Zealand White rabbits

PURPOSE

To investigate the potential activity of cyclosporin A (CsA) to induce mammary hyperplasia in New Zealand White (NZW) rabbits.

METHODS

Female NZW rabbits were used throughout experiments. To simulate the conditions of immunosuppression, CsA (10 mg/kg of body weight/d) was administered intravenously on a daily basis for 14 days and methylprednisolone (5 mg/kg/d) was administered on the first two days. The CsA (10 mg/kg/d) also was administered without methylprednisolone for 14 days to another cohort of rabbits. Mammary tissue of each rabbit was palpated and serially measured during this treatment period. The CsA was discontinued, and rabbits were monitored for 14 more days during the washout period. Sequential plasma concentrations of prolactin, 17beta-estradiol, and progesterone in each blood sample were determined by use of radioimmunoassay.

RESULTS

All NZW rabbits treated with CsA and methylprednisolone for immunosuppression consistently developed striking mammary tissue hyperplasia. At the end of treatment with CsA and methylprednisolone, mammary glands had extensive changes consistent with actively lactating glands. Similar but less extensive hyperplasia developed in response to CsA alone. Plasma concentration of prolactin increased during treatment and decreased during the washout period. Plasma concentration of 17beta-estradiol increased during treatment and continued to increase during the washout period. Plasma progesterone concentration decreased at the end of treatment. On discontinuation of CsA, mammary hyperplasia regressed.

CONCLUSIONS

Cyclosporine A, with or without methylprednisolone, induces mammary hyperplasia and hyperprolactinemia in NZW rabbits. This rabbit model may be a reliable in vivo system by which to study immunosuppressant-induced structural and functional changes of mammary glands similar to those observed in humans.

Inhibition of measles virus replication by 5'-nor carbocyclic adenosine analogues

Despite intense efforts to increase vaccine coverage, measles virus (MV) still causes significant morbidity and mortality in the world, sometimes as the result of severe, chronic, lethal disease. In an effort to develop therapies to supplement immunization strategies, a number of 5'-nor carbocyclic adenosine analogues were evaluated for anti-MV activity in CV-1 monkey kidney cells. Of those compounds tested, those either unsubstituted at C4 or possessing a hydroxyl, azido or amino substituent at that position were the most active, with particularly significant inhibition of MV, strain Chicago-1. The EC50 values against this strain ranged from <0.1 to 1 mg/ml, as determined by cytopathic effect reduction assay, and confirmed by neutral red uptake. By virus yield reduction assay (+)-(1S,25,3R,4S)-4-(6'-amino-9'H-purin-9'-yl)cyclopentane-1,2,3-triol (2) (-)-(1R,2S,3R)-1-(6'-amino-9'H-purin-9'-yl)-2,3-dihydoxycyclopent-4-ene (3) (-)-(1R,2S,3R)-1-(6'-amino-9'H-purin-9'-yl)cyclopentane-2,3-dihydoxycyclopentane (5) and (-)-(1R,2R,3R,4S)-4-amino-1-(6'-amino-9'H-purin-9'-yl)cyclopentane-2,3-diol (8) were the most potent compounds tested, all with EC90 values of < or =0.4 mg/ml. Compounds 3 and 5 were also tested against other MV strains, and similarly inhibited those strains except for four designated as Bil, Edmonston, SA and X-1108. Compound 8 did not potently inhibit these other MV strains. In addition, 3, 5 and 8 demonstrated synergistic (additive) inhibition of MV replication in combination with ribavirin at several concentrations. Compounds 3, 5 and 8 were also potent MV inhibitors even when added to infected cells 24 h after virus exposure. None of these three compounds was virucidal at concentrations that inhibited viral replication as determined by virus yield reduction assay. Most compounds tested were also not toxic at concentrations >100 mg/ml in actively growing and stationary-phase cells. Results suggest that these compounds may be clinically useful anti-MV virus agents.

5'-Nor carbocyclic 5'-deoxy-5'-(isobutylthio)adenosine and a 2',3'-dideoxy-2',3'-didehydro derivative

The inhibition of biochemical processes requiring S-adenosylmethionine as a co-factor have led to many nucleoside-based medicinal agents. Included in this group are 5'-deoxy-5'-(isobutylthio)adenosine (SIBA), a nucleoside with antiparasitic, antiviral and antiproliferative effects, and 5'-noraristeromycin, a carbocyclic-derived nucleoside with potent antiviral properties. This report brings together the structural components of these two compounds by describing both enantiomers of carbocyclic 5-nor SIBA (3 and 4). Owing to the recent interest in 2',3'-dideoxy-2',3'-didehydro nucleosides as antiviral agents, this derivative of 3 (5) is also described. All three compounds were screened against a variety of viruses and were found to be inactive at high concentrations or at limiting concentrations for the screening methods. The viruses subjected to 3-5 were herpes simplex virus types 1 and 2, human cytomegalovirus, vaccinia virus, vesicular stomatitis virus, respiratory syncytial virus, varicelIa zoster virus, coxsackie virus, parainfluenza-3 virus, sindbis virus, punta toro virus, reovirus-1, human immunodeficiency virus, influenza virus types A and B, adenovirus type 1 and measles virus. These results suggest that the C-5' methylene of the C-5' thio-based carbocyclic nucleosides is important for their antiviral properties.

Stock cultures of free-living amebas: effect of temperature on viability and pathogenicity

The effect of temperature on the viability and pathogenicity of free-living amebas during long-term storage were carried out for 34 mo at room temperature, 40 mo at +4 C, and 15 mo at -15 C. During long-term storage, pathogenic amebas tend to lose their virulence. Acanthamoeba showed better survival potential than Naegleria.

Risk factors for development of acute renal failure (ARF) requiring dialysis in patients undergoing cardiac surgery

Acute renal failure (ARF) is one of the major complications after cardiopulmonary bypass for open heart operations. The present study was undertaken to identify the risk factors for the development of ARF following cardiopulmonary bypass (CPB). Four hundred and forty-seven consecutive patients who underwent open heart procedures from July 1994 to June 1995 were analyzed retrospectively. Their mean age was 55.6 +/- 14.2 (SD) years (range, 18 to 80). Dialysis was instituted whenever a patient exhibited inadequate urine output (<0.5 mL/kg/hr) for 2 to 3 hours despite correction of hemodynamic status and diuretic therapy, especially if fluid overload, hyperkalemia, or metabolic acidosis were also present. Twenty variables were analyzed by univariate analysis; these included nine preoperative variables--age, sex, hypertension, atherosclerosis, diabetes mellitus, left ventricular end-diastolic dimension (LVEDD) >5 cm, preoperative congestive heart failure, renal insufficiency (serum creatinine > or =130 micromol/L on two occasions), and sepsis--10 intraoperative variables--duration of CPB, redo procedures, emergency surgery, use of intraaortic balloon pump (IABP) in operating room, use of gentamicin, use of ceftriaxone, use of sulbactam/ampicillin, requirement of deep hypothermic circulatory arrest, duration of low mean perfusion pressure (mean pressure <50 mmHg for more than 30 minutes), operation on multiple valves--and one postoperative variable--significant hypotension (systolic blood pressure less than 90 mmHg for more than 1 hour). Significant variables or the variables having a trend (p<0.1) to be associated with ARF were included in stepwise multiple logistic regression analyses. Three regression analyses were performed separately. The incidence of ARF requiring dialysis in the study period was 15.0%. Significant risk factors for whole group of patients (regression I) were preoperative renal insufficiency (p<0.0001), postoperative hypotension (p<0.0001), cardiopulmonary bypass time more than 140 min (p<0.005), preoperative congestive heart failure (p<0.01), and history of diabetes mellitus (p<0.01). The risk factors in the valve group of patients (regression II) were preoperative renal insufficiency (p<0.0001) and postoperative hypotension (p<0.05). Risk factors in the CABG patients (regression III) were postoperative hypotension (p=0.0001), CPB time more than 140 min (p<0.05), preoperative renal insufficiency (p<0.05), and age (p<0.05). The authors conclude that preoperative renal insufficiency and postoperative hypotension are the most important independent risk factors for ARF in postcardiac surgical patients. In addition, CPB time greater than 140 minutes and old age are also independent risk factors for ARF in CABG patients. CPB time more than 140 minutes, history of diabetes mellitus, and preoperative congestive heart failure are independent risk factors for development of ARF in our total group of patients. These findings may have important clinical implications in the prevention of ARF in postcardiac surgical patients.

A cross-sectional growth study of trunk and limb segments of the Bengali boys of Calcutta

This report deals with cross-sectional growth of sitting height (SH), subischial length (SL, estimated as height minus sitting height), height of the anterior superior iliac spine (HIS), and total arm length (TAL) of Bengali school boys (Calcutta), aged 7.0-16.0 years. Preece-Baines model 1 (PB1) fits to the cross-sectional means of the four traits estimate the average ages at maximum increment at 12.41 years for SL, at 12.43 years for HIS, at 12.97 for TAL, and at 13.74 years for SH. Maximum increment of the upper and lower segment of the body are reached at an earlier age in the present study than in a longitudinal analysis of semi-urban Bengali boys from the suburban area of Calcutta. Socioeconomic differences and secular trend might explain this shift towards earlier maturation.

The effect of erythritol on the stability of gamma-glutamyl transpeptidase and N-acetyl glucosaminidase in human urine

In toxicology studies and clinical trials of erythritol, treated animals and human subjects had higher urine gamma-glutamyl transpeptidase [gamma-glutamyl transferase (gamma-GT)] than untreated controls. It has previously been reported that gamma-GT activity in frozen urine decreases with time; therefore, a study was undertaken to examine the effects of storage temperature, time, and the presence of erythritol on the stability of gamma-GT and N-acetyl glucosaminidase in human urine. In this study, it was found that the rate of decrease of the activity of gamma-GT is much greater at -20 degrees C than at -70 degrees C. Variation in the storage temperature of the frozen urine is particularly deleterious to gamma-GT. The addition of erythritol in a concentration of 5% reduces this decrease. Approximately 15% of N-acetyl glucosaminidase activity is lost in the initial process of freezing the urine. Thereafter, conditions of temperature, time, and the presence or absence of erythritol account for little additional loss of activity.

Characterization of nucleoside uptake and transport in Entamoeba histolytica

The uptake and transportation of purine and pyrimidine based nucleosides by trophozoites of axenically grown Entamoeba histolytica (HMI-IMSS) were studied. The trophozoites transported adenosine and its analog tubercidin (1 microM) at a significant rate but poor transportation was observed in case of uridine (about 10% relative rate), inosine (3%), thymidine (2%) and formycin B (1%). The Km for adenosine was 160 +/- 42 microM. Unlabeled nucleosides (100 microM) inhibited adenosine and tubercidin transport. Adenosine related compounds 5'-deoxyadenosine and nebularin inhibited adenosine and tubercidine transport by 50% or more. However, inosine related compounds guanosine, 3'-deoxyinosine and formycin B were less inhibitory. The pyrimidine nucleosides uridine, thymidine and cytidine were poorly inhibitory. 6-[(4 nitrobenzyl)-mercapto] purine ribonucleoside, an inhibitor of mammalian nucleoside transporter, inhibited adenosine or tubercidin transport in E. histolytica variably between 0-30% at 10 microM, but dilazep, a known inhibitor, was inactive upto 10 microM. Increase in temperature from 22 degrees C to 33 degrees C enhanced the rate of transport of adenosine 4.5 fold, tubercidin 7.3 fold and of inosine 4 fold. These findings along with the structure activity figures suggested that transport was mediated and not passive.

Development of improved electrical-substitution radiometers at the National Research Council of Canada

We describe the development of a third generation of electrical-substitution radiometers (ESR's) at the National Research Council of Canada. The new ESR's follow the same general design as before, but incorporate improved thermopiles and electrical heating elements. The ESR's have a responsivity between 0.6 and 1.0 VW(-1), a time constant of approximately 2.0 s, a uniformity of 0.1% over a 6-mm-diameter region, and a noise level of approximately 6 nW. Performance characteristics of the new ESR's are discussed. It is shown that calibrations performed with these ESR's agree with those made with the previous generation of ESR's to better than 0.05%.

Alloxan diabetes in Swiss mice: activity of Na(+)-K(+)-ATPase and succinic dehydrogenase

The activities of two enzymes viz: Na(+)-K(+)-ATPase and succinic dehydrogenase (SDH) in brain and liver of alloxan diabetic Swiss albino mice are reported. Alloxan diabetes caused significant decrease in the activity of Na(+)-K(+)-ATPase reflecting reduced glucose transport across the cell membrane. On the contrary, the observed enhanced activity of the enzyme SDH is attributed to increased supply of TCA cycle substrates from accelerated oxidation of fatty acids.

Isoenzyme pattern of clones of Entamoeba histolytica

The isoenzyme pattern of clones of E. histolytica isolated from symptomatic and asymptomatic patients of amoebiasis were determined by starch gel electrophoresis. Ten parent cultures (uncloned), 5 from symptomatic and 5 from asymptomatic patients were isolated and established in Robinsons medium as xenic cultures. A total of 100 clones were isolated from parent cultures but only 65 could be established. Starch gel electrophoresis was carried out on the uncloned and cloned cultures. The analysis showed that the 5 uncloned culture from symptomatic patients had 4 isolates with pathogenic zymodeme and 1 isolate with non-pathogenic zymodeme pattern. The presence of beta band and absence of alpha band for phosphoglucomutase (PGM) and a fast moving Hexokinase (HK) band were taken as markers of pathogenicity. The 5 cloned cultures from asymptomatic patients had three isolates with pathogenic and 2 with non-pathogenic pattern. The cloned isolates from symptomatic patients (35) had 20 pathogenic zymodemes and asymptomatic patients (30) had 15 pathogenic zymodemes. Non-pathogenic zymodeme obtained in the present study were I, IV, V, X and XIII and the pathogenic zymodemes obtained were II and XIV. The data of the study indicated that (i) asymptomatic patients also harbour pathogenic zymodemes; and (ii) zymodeme II also coexsist with zymodeme XIV in the Indian population.

In vitro effect of alloxan on Na(+)-K(+)-ATPase and succinate dehydrogenase activities in brain and liver of mice

The present study reports in vitro inhibition of the activities of enzymes Na(+)-K(+)-ATPase and succinate dehydrogenase by alloxan in brain and liver homogenates of Swiss mice. The Vmax of both the enzymes was reduced in presence of alloxan without any substantial alteration in Km for substrate. Lineweaver Burk's plots showed higher 1/Vmax for alloxan treated samples and convergence of both slopes to intercept-1/Km. The observations pointed to non-competitive type inhibition of the enzymes by alloxan. This may be due to the modification of essential--SH groups present within/adjacent to substrate binding sites by alloxan.

Muller cells of chicken retina synthesize 11-cis-retinol

The amounts of endogenous retinyl palmitate, retinol and retinaldehyde were measured in the neural retina and retinal pigment epithelium (RPE) of predominantly cone (chicken), rod (rat) and more mixed (cat, human) retinae. The ratio of 11-cis to all-trans isomers of retinyl palmitate and retinol in the neural retina and the RPE increases progressively with the increase in diurnality of the species from rat to chicken. The membrane fractions of both chicken and bovine RPE enzymically isomerize all-trans retinol to 11-cis-retinol. Chicken neural retina membranes enzymically form 11-cis-retinol and all-trans-retinyl palmitate from all-trans-retinol. Light and electron microscopy revealed no contamination of chicken neural retina by RPE. Muller cells from chicken retina were isolated, cultured and characterized by immunocytochemical localization of cellular retinaldehyde-binding protein. Cultured chicken Muller cells form all-trans-retinyl palmitate, 11-cis-retinol and 11-cis-retinyl palmitate from all-trans-retinol and release most of the 11-cis-retinol into the medium. The results indicate that chicken neural retina and Muller cells in particular synthesize 11-cis-retinoids from all-trans-retinol.

An improved PVC strip ML-ELISA technique for diagnosis of recent cases of amoebiasis

Conventional plate ML-ELISA technique for diagnosis of recent cases of amoebiasis was converted into a simple polyvinyl chloride strip multilayer-enzyme linked immunosorbent assay (PVC strip ML-ELISA). This report details the development and preliminary characterization of the PVC strip ML-ELISA method for Entamoeba histolytica antigen detection in human fecal samples. In addition, we evaluated the relative efficacies of the PVC strip ML-ELISA and the conventional plate ML-ELISA methods by screening different categories of amoebiasis patients and other intestinal parasites. A significant correlation was found (P less than 0.01) between the two assay methods with reference to sensitivity and specificity of detecting E. histolytica antigens. However, with reference to operational case and economy, the PVC strip ML-ELISA may be performed even by paramedical technical personnel under field conditions.

Pathogenicity and antigenic components of excysted Giardia lamblia isolated from patients in Riyadh, Saudi Arabia

Giardia lamblia cysts were isolated from patients in Riyadh, Saudi Arabia. Cysts and trophozoites (from axenically excysted cysts) were given orally by gavage to mice to establish the pathogenicity of the Riyadh isolate. There was no effect of varying the dose of administered parasite on parasite excretion or morbidity. A typical pathologic pattern of giardiasis was demonstrated by histologic methods and electron microscopy. Antigenic components of the Riyadh isolate were compared with the Portland strain and with Entamoeba histolytica by gel diffusion immunoprecipitation and immunoblotting. There were few antigens in common between Riyadh isolate and the Portland strain, and little cross-reactivity of the Riyadh isolate with Entamoeba histolytica was observed.

Inhibition of axenically grown Entamoeba histolytica by purine nucleoside analogs and actions of natural nucleosides

The effects of the nucleoside analogs tubercidin, nebularin, formycin B and 3'-deoxyinosine on axenically grown Entamoeba histolytica were tested. Both tubercidin and nebularin showed pronounced inhibitory action, 50% of growth inhibition (IC50) being obtained at 0.14 and 0.82 microM, respectively. Formycin B and 3'-deoxyinosine were essentially inactive or weakly active at concentrations above 10 microM. Natural nucleosides, including adenosine, inosine, guanosine, thymidine, uridine and cytidine caused no significant effects at concentrations of 0.01-1 microM, however, significant inhibitory action was observed at or above 10 microM with cytidine and thymidine. The exploration of cytotoxic nucleosides as antiamebal drugs is of continued interest.

Protective and curative effects of rifampicin in Acanthamoeba meningitis of the mouse

BALB/c mice inoculated nasally with Acanthamoeba culbertsoni, resulting in amebic encephalitis and death 3-7 days, were treated with rifampicin prophylactically (daily for 2 days with 75 and 100 mg/kg) and after infection (daily for 5 days with doses of 10-100 mg/kg). Prophylactic treatment resulted in full protection against infection, as assessed by absence of symptoms of central nervous system malfunction and negative brain culture 10 days after inoculation. Curative treatment was effective at the same doses; however, at doses of 10, 25, and 50 mg/kg, only two of six animals were free of symptoms and infection.

Synthesis of retinoids by human retinal epithelium and transfer to rod outer segments

The synthesis and release of 11-cis-retinoids by primary cultures of human retinal pigment epithelium (RPE) and the transfer of these retinoids to co-incubated human rod outer segments (ROS) were studied. Monolayers of 2-3-week-old cultured RPE incorporate tritiated all-trans-retinol, esterify it to the corresponding retinyl palmitate, form 11-cis-retinol and 11-cis-retinaldehyde and release retinaldehyde into the culture medium. The ratio of 11-cis to all-trans isomers of retinol, retinyl palmitate and retinaldehyde formed in the cells along with retinaldehyde released and incorporated into the ROS progressively increases, indicating a progressive increase in the concentration of 11-cis isomer from the time it is formed in RPE cells until its transfer to ROS. Incorporation of 11-cis-retinaldehyde into the ROS is directly related to the amount of albumin present in the media, suggesting the transfer of retinoids from RPE to photoreceptor to be a protein-mediated process. Events leading to isomerization, esterification, oxidation and release of retinoids by human RPE and incorporation of retinoids into ROS can therefore be examined in vitro.