A genetically encoded sensor for in vivo imaging of orexin neuropeptides

Orexins (also called hypocretins) are hypothalamic neuropeptides that carry out essential functions in the central nervous system; however, little is known about their release and range of action in vivo owing to the limited resolution of current detection technologies. Here we developed a genetically encoded orexin sensor (OxLight1) based on the engineering of circularly permutated green fluorescent protein into the human type-2 orexin receptor. In mice OxLight1 detects optogenetically evoked release of endogenous orexins in vivo with high sensitivity. Photometry recordings of OxLight1 in mice show rapid orexin release associated with spontaneous running behavior, acute stress and sleep-to-wake transitions in different brain areas. Moreover, two-photon imaging of OxLight1 reveals orexin release in layer 2/3 of the mouse somatosensory cortex during emergence from anesthesia. Thus, OxLight1 enables sensitive and direct optical detection of orexin neuropeptides with high spatiotemporal resolution in living animals.

Obesity causes selective and long-lasting desensitization of AgRP neurons to dietary fat

Body weight is regulated by interoceptive neural circuits that track energy need, but how the activity of these circuits is altered in obesity remains poorly understood. Here we describe the in vivo dynamics of hunger-promoting AgRP neurons during the development of diet-induced obesity in mice. We show that high-fat diet attenuates the response of AgRP neurons to an array of nutritionally-relevant stimuli including food cues, intragastric nutrients, cholecystokinin and ghrelin. These alterations are specific to dietary fat but not carbohydrate or protein. Subsequent weight loss restores the responsiveness of AgRP neurons to exterosensory cues but fails to rescue their sensitivity to gastrointestinal hormones or nutrients. These findings reveal that obesity triggers broad dysregulation of hypothalamic hunger neurons that is incompletely reversed by weight loss and may contribute to the difficulty of maintaining a reduced weight.

Soma-Targeted Imaging of Neural Circuits by Ribosome Tethering

Neuroscience relies on techniques for imaging the structure and dynamics of neural circuits, but the cell bodies of individual neurons are often obscured by overlapping fluorescence from axons and dendrites in surrounding neuropil. Here, we describe two strategies for using the ribosome to restrict the expression of fluorescent proteins to the neuronal soma. We show first that a ribosome-tethered nanobody can be used to trap GFP in the cell body, thereby enabling direct visualization of previously undetectable GFP fluorescence. We then design a ribosome-tethered GCaMP for imaging calcium dynamics. We show that this reporter faithfully tracks somatic calcium dynamics in the mouse brain while eliminating cross-talk between neurons caused by contaminating neuropil. In worms, this reporter enables whole-brain imaging with faster kinetics and brighter fluorescence than commonly used nuclear GCaMPs. These two approaches provide a general way to enhance the specificity of imaging in neurobiology.

Sustained NPY signaling enables AgRP neurons to drive feeding

Artificial stimulation of Agouti-Related Peptide (AgRP) neurons promotes intense food consumption, yet paradoxically during natural behavior these cells are inhibited before feeding begins. Previously, to reconcile these observations, we showed that brief stimulation of AgRP neurons can generate hunger that persists for tens of minutes, but the mechanisms underlying this sustained hunger drive remain unknown (Chen et al., 2016). Here we show that Neuropeptide Y (NPY) is uniquely required for the long-lasting effects of AgRP neurons on feeding behavior. We blocked the ability of AgRP neurons to signal through AgRP, NPY, or GABA, and then stimulated these cells using a paradigm that mimics their natural regulation. Deletion of NPY, but not AgRP or GABA, abolished optically-stimulated feeding, and this was rescued by NPY re-expression selectively in AgRP neurons. These findings reveal a unique role for NPY in sustaining hunger in the interval between food discovery and consumption.

A Pool of Postnatally Generated Interneurons Persists in an Immature Stage in the Olfactory Bulb

Calretinin (CR)-expressing periglomerular (PG) cells are the most abundant interneurons in the glomerular layer of the olfactory bulb. They are predominately generated postnatally from the septal and dorsal subventricular zones that continue producing them well into adulthood. Yet, little is known about their properties and functions. Using transgenic approaches and patch-clamp recording in mice of both sexes we show that CR(+) PG cells of both septal and dorsal origin have homogeneous morphological and electrophysiological properties. However, unlike other PG cells, these axonless neurons express a surprisingly small repertoire of voltage-activated channels and do not fire or fire at most a single and often small action potential. Moreover, they are not innervated by olfactory sensory neurons and receive little synaptic inputs from mitral or tufted cells at excitatory synapses where NMDA receptors predominate. These membrane and synaptic properties, that resemble those of newborn immature neurons not yet integrated in the network, persist over time and limit the recruitment of CR(+) PG cells by afferent inputs that strongly drive local network activity. Together, our results show that postnatally generated CR(+) PG cells continuously supply a large pool of neurons with unconventional properties. These data also question the contribution of CR(+) PG cells in olfactory bulb computation.SIGNIFICANCE STATEMENT Calretinin-expressing PG cells are by far the most abundant interneurons in the glomerular layer of the olfactory bulb. They are continuously produced during postnatal life, including adulthood, from neural stem cells located in the subventricular zones. Surprisingly, unlike other postnatally generated newborn neurons that quickly integrate into preexisting olfactory bulb networks, calretinin-expressing PG cells retain immature properties that limit their recruitment in local network activity for weeks, if not months, as if they would never fully mature. The function of this so far unsuspected pool of latent neurons is still unknown.

Prevalence and risk factors associated with intestinal parasitic infections among schoolchildren in Punjab, Pakistan

Intestinal parasitic infections (IPIs) are a major cause of morbidity worldwide and have been described as an important public health concern. The present study aimed to determine the prevalence and identification of risk factors associated with IPIs among 3-15 years old school age children residing in Mandi Bahauddin, Pakistan from 2011- 2013. A cross sectional school-based study was conducted using a structured pre-tested questionnaire. Anthropometric tools and stool tests were used to obtain epidemiological and disease data. The direct wet mount preperation in saline/iodine/haematoxylin stain and Kato-Katz methods were used for stool examination. Data were analysed using appropriate descriptive, univariate and multivariable logistic regression methods. Of the 1,434 children studied (mean age of 8.6±3.6 years) the overall prevalence rate for intestinal parasitic infections was found to be 33.3%. Children infected with single parasite accounted for 27.6% and 5.7% were detected with poly-parasitism. The study showed that helminths (21.4%) were more prevalent than protozoans (17.9%). Ascaris lumbricoides (17.5%), Giardia lamblia (9.8%), Entamoeba histolytica (8.2%), Hymenolepis nana (2.0%), Trichuris trichiura (1.3%) and Taenia saginata (0.7%) were identified in children living in irrigated areas. The multiple logistic regression model indicated that age of the child, gender, family size, source of drinking water, type of milk used, house condition, feeding habit, personal hygiene and socioeconomic status were significantly (p<0.05) associated with the IPIs. Intestinal parasites were prevalent in varying magnitude among the schoolchildren located in irrigated areas. We conclude that there is a need for mass scale campaigns to create awareness regarding health and hygiene in children, and the need for development of effective poverty control programmes because deworming alone is not adequate to control parasitic infections.

[Role of twinkling artifact in characterization of urinary calculi]

INTRODUCTION

Stone characterization is becoming important before decision of treatment such as percutaneous nephrolithotomy (PCNL) and extracorporeal shock wave lithotripsy (ESWL). Some studies have reported that the twinkling artifact (color-flow ultrasonography artifact) may be useful to detect urinary stones. This study aims to determine whether the presence or absence of the twinkling artifact is correlated with the chemical composition of the stones.

MATERIAL AND METHOD

Patients with renal stones > 0.5 cm were included in a prospective study. Sixty patients were examined with x-ray film, intravenous pyelography, non-contrast computerized tomography, and color and spectral doppler ultrasonography. The artifact was considered grade 1 when occupied only one portion of the acoustic shadowing and when the artifact occupied the entire acoustic shadowing was considered grade 2. Patients with stones smaller than 2 cm were treated with SWL and patients with stones larger than 2 cm were treated with PCNL.

RESULTS

No artifact (grade 0) was detected in 11 subjects, grade 1 in 25 and grade 2 in 24. Significant relationship was found between the increase in twinkling artifact and stone size (p<0.001). When the relation between the composition of the stones and the twinkling artifact was analyzed, artifact was detected nearly in all of the calcium oxalate dihydrate and calcium phosphate stones; whereas the artifact was detected in more than half of the calcium oxalate monohydrate and uric acid stones. In ESWL group it was observed that as the grade of the twinkling artifact increases, the number of required ESWL sessions decreases (p<0.001). In PCNL group twinkling artifact was found in all of the patients (100%) with roughly surfaced stones.

CONCLUSION

The roughness of stone surface is the most important factor in terms of formation of the twinkling artifact in kidney stones. This artifact can be of use in anticipating the breakability of the stones of those patients to be treated with applied ESWL. One might anticipate that cases where the size of the stone is larger than 2 cm but no twinkling artifact is detected are calcium oxalate monohydrate, which is one of the stones with highest level of breakability.

Risk of subsequent fracture and mortality within 5 years after a non-vertebral fracture

SUMMARY

The absolute 5-year risk of subsequent non-vertebral fractures (NVFs) in 1,921 patients presenting with a NVF was 17.6% and of mortality was 32.3%. These risks were highest within the first year, indicating the need to study which reversible factors can be targeted to immediately minimise subsequent fracture risk and mortality.

INTRODUCTION

NVFs are the most frequent clinical fractures in patients presenting at the emergency unit because of a clinical fracture. The aim of the study was to determine the 5-year absolute risk (AR) of subsequent NVF and mortality in patients at the time they present with a NVF.

METHODS

Between 1999 and 2001, 1,921 consecutive patients 50+ years from a level 1 trauma centre were included. All NVFs were confirmed on radiograph reports, and mortality was checked in the national obituary database. Available potential risk factors for a subsequent NVF and mortality (age, sex and baseline fracture location: major-hip, pelvis, multiple ribs, proximal tibia/humerus and distal femur; minor-all others) were expressed as hazard ratios (HR) with 95% confidence intervals (CI) using multivariable Cox regression analysis.

RESULTS

The AR for a subsequent NVF was 17.6% and was related to age (HR per decade, 1.44; 95%CI, 1.29-1.60). The AR for mortality was 32.3% and was related to age (HR per decade, 2.59; 95%CI, 2.37-2.84), male sex (HR, 1.74; 95%CI, 1.44-2.10), major fracture at baseline (HR, 5.56; 95%CI, 3.48-8.88; not constant over time) and subsequent fracture (HR, 1.65; 95%CI, 1.33-2.05). The highest risks were found within the first year (NVFs, 6.4%; mortality, 12.2%) and were related to age and, in addition, to baseline fracture location for mortality.

CONCLUSIONS

Within 5 years after an initial NVF, nearly one in five patients sustained a subsequent NVF and one in three died. One third of subsequent NVFs and mortality occurred within 1 year, indicating the need to study which reversible factors can be targeted to immediately prevent subsequent fractures and mortality.