Effect of Light on the Metabolism of Lipids in the Rat Retina

The effect of light on the in vitro incorporation of a variety of radioactive precursors into glycerolipids was tested in isolated retinas of albino rats. There was an increase in the incorporation of [2-3H]myo-inositol, 32Pi, [2-3H]glycerol, and [methyl-3H]choline into retinal phospholipids in light compared to that in darkness. [2-3H]myo-Inositol was incorporated primarily into phosphatidylinositol. 32Pi was incorporated primarily into the phosphoinositides, although there were significant increases in the specific activities of all retinal phospholipids in light compared to those in darkness. Likewise, [2-3H]glycerol incorporation into all retinal phospholipids and diglycerides was greater in light than in the dark. There was no effect of light on the incorporation of [2-3H]ethanolamine into phosphatidylethanolamine or of [3-3H]serine into phosphatidylserine, although these phospholipids were labeled to a greater extent in light with [2-3H]glycerol. There was no effect of light on the incorporation of [3H]palmitic acid into diglycerides and phospholipids, with the exception of phosphatidylinositol. Light also had no effect on the uptake of [2-3H]glycerol, [2-3H]inositol, or [methyl-3H]choline into the retina. We conclude from these studies that light stimulates the phosphoinositide effect in the rat retina. Although some of the results are consistent with a stimulation of de novo synthesis of all lipid classes, our studies with [3H]palmitate, [2-3H]ethanolamine, and [3-3H]serine do not support this conclusion.(ABSTRACT TRUNCATED AT 250 WORDS)     

Lipid composition of Limulus photoreceptor membranes.

The lipid composition has been determined for rhabdomeric photoreceptor membranes of Limulus, and these data are compared with those from photoreceptor membranes of albino rats. The comparison is of interest because the membranes of these two photoreceptor cells regulate ionic transport differently during the response to illumination. 1. Phospholipid class composition of Limulus is similar, but not identical, to that of rats. The major differences are a greater percentage of sphingomyelin in Limulus and a greater percentage of phosphatidylethanolamine in the rat. 2. Ethanolamine plasmalogens, not observed in rat photoreceptor membranes, are present in Limulus photoreceptor fractions. 3. The level of cholesterol in Limulus is higher than that usually reported for vertebrate rod outer segments. 4. The predominant polyunsaturated fatty acids of Limulus photoreceptor membrane phospholipids are 20: 4(n-6) and 20: 5(n-3) with only traces of 22: 6(n-3). This is in sharp contrast with the large percentages of 22: 6(n-3) found in rat photoreceptors. 5. The fatty acid distributions of both membrane systems are highly unsaturated, but the ratio of (n-3) to (n-6) polyunsaturates is only 1.7 for Limulus as compared to 4.6 for rat.     

Transorbital Sonographic Evaluation of Normal Optic Nerve Sheath Diameter in Healthy Volunteers in Bangladesh

Introduction

Measurement of optic nerve sheath diameter (ONSD) by ultrasound is increasingly used as a marker to detect raised intracranial pressure (ICP). ONSD varies with age and there is no clear consensus between studies for an upper limit of normal. Knowledge of normal ONSD in a healthy population is essential to interpret this measurement.

Methods

In a prospective observational study, ONSD was measured using a 15 MHz ultrasound probe in healthy volunteers in Chittagong, Bangladesh. The aims were to determine the normal range of ONSD in healthy Bangladeshi adults and children, compare measurements in males and females, horizontal and vertical beam orientations and left and right eyes in the same individual and to determine whether ONSD varies with head circumference independent of age.

Results

136 subjects were enrolled, 12.5% of whom were age 16 or under. Median ONSD was 4.41 mm with 95% of subjects in the range 4.25–4.75 mm. ONSD was bimodally distributed. There was no relationship between ONSD and age (≥4 years), gender, head circumference, and no difference in left vs right eye or horizontal vs vertical beam.

Conclusions

Ultrasonographic ONSD in Bangladeshi healthy volunteers has a narrow bimodal distribution independent of age (≥4 years), gender and head circumference. ONSD >4.75 mm in this population should be considered abnormal.     

Glucose transporter 2 expression is down regulated following P2X7 activation in enterocytes

With the diabetes epidemic affecting the world population, there is an increasing demand for means to regulate glycemia. Dietary glucose is first absorbed by the intestine before entering the blood stream. Thus, the regulation of glucose absorption by intestinal epithelial cells (IECs) could represent a way to regulate glycemia. Among the molecules involved in glycemia homeostasis, extracellular ATP, a paracrine signaling molecule, was reported to induce insulin secretion from pancreatic β cells by activating P2Y and P2X receptors. In rat's jejunum, P2X7 expression was previously immunolocalized to the apex of villi, where it has been suspected to play a role in apoptosis. However, using an antibody recognizing the receptor extracellular domain and thus most of the P2X7 isoforms, we showed that expression of this receptor is apparent in the top two‐thirds of villi. These data suggest a different role for this receptor in IECs. Using the non‐cancerous IEC‐6 cells and differentiated Caco‐2 cells, glucose transport was reduced by more than 30% following P2X7 stimulation. This effect on glucose transport was not due to P2X7‐induced cell apoptosis, but rather was the consequence of glucose transporter 2 (Glut2)'s internalization. The signaling pathway leading to P2X7‐dependent Glut2 internalization involved the calcium‐independent activation of phospholipase Cγ1 (PLCγ1), PKCδ, and PKD1. Although the complete mechanism regulating Glut2 internalization following P2X7 activation is not fully understood, modulation of P2X7 receptor activation could represent an interesting approach to regulate intestinal glucose absorption. J. Cell. Physiol. 228: 120–129, 2013. © 2012 Wiley Periodicals, Inc.     

Ultra high risk status and transition to psychosis in 22q11.2 deletion syndrome

The 22q11.2 deletion syndrome (22q11DS) is characterized by high rates of psychotic symptoms and schizophrenia, making this condition a promising human model for studying risk factors for psychosis. We explored the predictive value of ultra high risk (UHR) criteria in a sample of patients with 22q11DS. We also examined the additional contribution of socio‐demographic, clinical and cognitive variables to predict transition to psychosis within a mean interval of 32.5 ± 17.6 months after initial assessment. Eighty‐nine participants with 22q11DS (age range: 8‐30 years; mean 16.1 ± 4.7) were assessed using the Structured Interview for Psychosis‐Risk Syndromes. Information on Axis I diagnoses, internalizing and externalizing symptoms, level of functioning and IQ was also collected. At baseline, 22 (24.7%) participants met UHR criteria. Compared to those without a UHR condition, they had a significantly lower functioning, more frequent anxiety disorders, and more severe psychopathology. Transition rate to psychosis was 27.3% in UHR and 4.5% in non‐UHR participants. Cox regression analyses revealed that UHR status significantly predicted conversion to psychosis. Baseline level of functioning was the only other additional predictor. This is the first study investigating the predictive value of UHR criteria in 22q11DS. It indicates that the clinical path leading to psychosis is broadly comparable to that observed in other clinical high‐risk samples. Nevertheless, the relatively high transition rate in non‐UHR individuals suggests that other risk markers should be explored in this population. The role of low functioning as a predictor of transition to psychosis should also be investigated more in depth.     

A revised annotation and comparative analysis of Helicobacter pylori genomes

Huge amounts of genomic information are currently being generated. Therefore, biologists require structured, exhaustive and comparative databases. The PyloriGene database (http://genolist.pasteur.fr/PyloriGene) was developed to respond to these needs, by integrating and connecting the information generated during the sequencing of two distinct strains of Helicobacter pylori. This led to the need for a general annotation consensus, as the physical and functional annotations of the two strains differed significantly in some cases. A revised functional classification system was created to accommodate the existing data and to make it possible to classify coding sequences (CDS) into several functional categories to harmonize CDS classification. The annotation of the two complete genomes was revised in the light of new data, allowing us to reduce the percentage of hypothetical proteins from approximately 40 to 33%. This resulted in the reassignment of functions for 108 CDS (approximately 7% of all CDS). Interestingly, the functions of only approximately 13% of CDS (222 out of 1658 CDS) were annotated as a result of work done directly on H.pylori genes. Finally, comparison of the two published genomes revealed a significant amount of size variation between corresponding (orthologous) CDS. Most of these size variations were due to natural polymorphisms, although other sources of variation were identified, such as pseudogenes, new genes potentially regulated by slipped-strand mispairing mechanism, or frame-shifts. 113 of these differences were due to different start codon assignments, a common problem when constructing physical annotations.