Channelrhodopsin-2–XXL,a powerful optogenetic tool for low-light applications

Channelrhodopsin-2 (ChR2) has provided a breakthrough for the optogenetic control of neuronal activity. In adult Drosophila melanogaster, however, its applications are severely constrained. This limitation in a powerful model system has curtailed unfolding the full potential of ChR2 for behavioral neuroscience. Here, we describe the D156C mutant, termed ChR2-XXL (extra high expression and long open state), which displays increased expression, improved subcellular localization, elevated retinal affinity, an extended open-state lifetime, and photocurrent amplitudes greatly exceeding those of all heretofore published ChR variants. As a result, neuronal activity could be efficiently evoked with ambient light and even without retinal supplementation. We validated the benefits of the variant in intact flies by eliciting simple and complex behaviors. We demonstrate efficient and prolonged photostimulation of monosynaptic transmission at the neuromuscular junction and reliable activation of a gustatory reflex pathway. Innate male courtship was triggered in male and female flies, and olfactory memories were written through light-induced associative training.Identifying causal relationships between neuronal activity and animal behavior is a fundamental goal of neuroscience. Crucially, this task requires testing whether defined neuronal populations are sufficient for eliciting behavioral modules. The development of light-gated ion channels that can be genetically targeted to specific cells has provided a unique solution to this challenge. In pioneering work, such optogenetic effectors or actuators were originally used as multicomponent approaches (1–3). The introduction of Channelrhodopsin-1 (ChR1) (4) and especially ChR2 as a light-sensitive cation channel (5) dramatically advanced the field by providing an efficient and straightforward single-component strategy for stimulating neuronal activity (6, 7).Besides cell-specific targeting of appropriate effector elements, precise neuronal control by optogenetics demands efficient light delivery to the neurons of interest. For behavioral studies, photostimulation is ideally accomplished in intact, freely moving organisms and accompanied by functional readouts. The combination of a rich, well-characterized behavioral repertoire and elegant molecular genetics has contributed to Drosophila’s strong impact on behavioral neurogenetics (8, 9). However, low light transmission through the pigmented cuticle presupposes high light intensities for using ChR2 in flies. This obstacle greatly complicates the experimental setup for freely moving animals, and the required light energies can cause heat damage when stimulation is applied over extended time periods. Moreover, limited cellular availability of all-trans-retinal (hereafter retinal for short) demands adding high retinal concentrations as a dietary supplement. If optical access to target cells is not provided by a translucent body wall (e.g., as in nematodes, zebrafish, and Drosophila larvae), an alternative solution is the implantation of an optical fiber directly into the brain. Although this approach has been used successfully in mammals (10), such an invasive procedure is infeasible for the study of intact small organisms.Due to these restrictions in Drosophila, ChR2 has not reached the popularity attained in other organisms, and instead the field has turned mainly to thermogenetic neuronal stimulation (11–13). As with all techniques, there are also drawbacks to using temperature as a stimulus, such as undesired background activity and a multitude of temperature-sensitive cellular processes and behavioral responses. Photo-liberation of caged ATP, combined with genetic targeting of ATP-gated ion channels, has been introduced as a different optogenetic technique in Drosophila (3, 14). However, its applications are constrained by invasive, time-consuming procedures for injection of caged ATP and a limited experimental time window.Here, we introduce improved ChR2 variants as an alternative approach to address these shortcomings in Drosophila. Compared with wild-type ChR2 (ChR2-wt), expression of these mutants in target cells led to strongly enhanced photocurrents. We provide the first report, to our knowledge, of ChR2-T159C (15, 16) in flies and describe a ChR2 variant, ChR2-XXL (extra high expression and long open state), that is characterized by an extended open-state lifetime, elevated cellular expression, enhanced axonal localization, and reduced dependence on retinal addition. As a consequence, this mutant does not require dietary retinal supplementation to depolarize cells, evoke synaptic transmission, and activate neuronal networks at very low irradiance. These features enabled behavioral photostimulation in freely moving flies using diffuse low-intensity light.     

Selfish supernumerary chromosome reveals its origin as a mosaic of host genome and organellar sequences

Supernumerary B chromosomes are optional additions to the basic set of A chromosomes, and occur in all eukaryotic groups. They differ from the basic complement in morphology, pairing behavior, and inheritance and are not required for normal growth and development. The current view is that B chromosomes are parasitic elements comparable to selfish DNA, like transposons. In contrast to transposons, they are autonomously inherited independent of the host genome and have their own mechanisms of mitotic or meiotic drive. Although B chromosomes were first described a century ago, little is known about their origin and molecular makeup. The widely accepted view is that they are derived from fragments of A chromosomes and/or generated in response to interspecific hybridization. Through next-generation sequencing of sorted A and B chromosomes, we show that B chromosomes of rye are rich in gene-derived sequences, allowing us to trace their origin to fragments of A chromosomes, with the largest parts corresponding to rye chromosomes 3R and 7R. Compared with A chromosomes, B chromosomes were also found to accumulate large amounts of specific repeats and insertions of organellar DNA. The origin of rye B chromosomes occurred an estimated ～1.1-1.3 Mya, overlapping in time with the onset of the genus Secale (1.7 Mya). We propose a comprehensive model of B chromosome evolution, including its origin by recombination of several A chromosomes followed by capturing of additional A-derived and organellar sequences and amplification of B-specific repeats.     

Left ventricular mass and function with reduced-fat or reduced-carbohydrate hypocaloric diets in overweight and obese subjects

In animals, carbohydrate and fat composition during dietary interventions influenced cardiac metabolism, structure, and function. Because reduced-carbohydrate and reduced-fat hypocaloric diets are commonly used in the treatment of obesity, we investigated whether these interventions differentially affect left ventricular mass, cardiac function, and blood pressure. We randomized 170 overweight and obese subjects (body mass index, 32.9±4.4; range, 26.5-45.4 kg/m(2)) to 6-month hypocaloric diets with either reduced carbohydrate intake or reduced fat intake. We obtained cardiac MRI and ambulatory blood pressure recordings over 24 hours before and after 6 months. Ninety subjects completing the intervention period had a full cardiac MRI data set. Subjects lost 7.3±4.0 kg (7.9±3.8%) with reduced-carbohydrate diet and 6.2±4.2 kg (6.7±4.4%) with reduced-fat diet (P<0.001 within each group; P=not significant between interventions). Caloric restriction led to similar significant decreases in left ventricular mass with low-carbohydrate diets (5.4±5.4 g) or low-fat diets (5.2±4.8 g; P<0.001 within each group; P=not significant between interventions). Systolic and diastolic left ventricular function did not change with either diet. The 24-hour systolic blood pressure decreased similarly with both interventions. Body weight change (β=0.33; P=0.02) and percentage of ingested n-3 polyunsaturated fatty acids (β=-0.27; P=0.03) predicted changes in left ventricular mass. In conclusion, weight loss induced by reduced-fat diets or reduced-carbohydrate diets similarly improved left ventricular mass in overweight and obese subjects over a 6-month period. However, n-3 polyunsaturated fatty acid ingestion may have an independent beneficial effect on left ventricular mass.     

Changes in masticatory mandibular movements in growing individuals: a six-year follow-up

The pattern of mandibular movement during chewing is influenced by several central and peripheral factors. The aim of the present study was to determine whether changes in masticatory function, characterized by mandibular velocity and displacement, occurred during individuals' normal growth. Forty-seven children, 9-15 years of age, were followed over a 6-year period. All had an Angle Class I occlusion with no obvious orthodontic problems. Oral motor function with respect to mandibular displacement, duration, and velocity was monitored 3-dimensionally with an opto-electronic method. The chewing cycle was divided into an opening, closing, and occlusal phase. Total body height was measured. During the follow-up period, all masticatory variables except the 3-dimensional opening distance showed significant changes. The total chewing cycle duration, the opening and occlusal time of the chewing cycle, and the 3-dimensional closing distance increased during the growth period, while the closing time of the chewing cycle, the 2-dimensional lateral and vertical distances and both the opening and closing velocity decreased. The children who grew proportionally most in height during the 6-year period, i.e. the youngest children in the group studied, showed a significantly larger decrease in the opening velocity. From this study it becomes evident that the variables of the chewing cycle undergo a continuous process of change during growth. This is possibly a reflection of anatomical changes, maturation of the central nervous system, and altered functional demands.     

The Hedonic Drive to Consume Palatable Foods Appears to be Lower in Gastric Band Carriers than in Severely Obese Patients Who Have Not Undergone a Bariatric Surgery

Background

We have recently shown that severely obese patients display a markedly enhanced drive to consume palatable food, and that this hedonic hunger is reduced after gastric bypass surgery. Adjustable gastric banding is another frequently performed bariatric operation with unknown effects on hedonic hunger motivation. Here, we compared the level of hedonic hunger in patients who have undergone a gastric banding with that in severely obese patients who have not undergone a bariatric operation and nonobese controls.

Methods

In a cross-sectional case–control study, 116 gastric banding patients, 138 severely obese patients, and 133 nonobese controls were examined with the Power of Food Scale (PFS), a questionnaire that reliably measures an individual’s motivation to consume highly palatable food.

Results

While the severely obese patients displayed markedly higher aggregated PFS scores and scores on the subdomain “generally available” and “physically present” food than the nonobese controls (all P?<?0.001), the gastric banding patients showed significantly lower scores on all of these variables than the obese patients (all P?<?0.001). However, the generally available food score was still higher in gastric banding patients than in the nonobese controls (P?=?0.001).

Conclusions

Data suggest that adjustable gastric banding may reduce the excessive appetite for palatable foods in severely obese patients. This suggestion needs to be confirmed in longitudinal studies.     

Roux-en Y Gastric Bypass Surgery Reduces Hedonic Hunger and Improves Dietary Habits in Severely Obese Subjects

Background

Many obese subjects suffer from an increased hedonic drive to consume palatable foods, i.e., hedonic hunger, and often show unfavorable dietary habits. Here, we investigated changes in the hedonic hunger and dietary habits after Roux-en-Y gastric bypass (RYGB) surgery.

Methods

Forty-four severely obese patients were examined before and on average 15.9?±?0.9 months after RYGB surgery with the Power of Food Scale (PFS), a questionnaire that reliably measures an individual’s motivation to consume highly palatable foods but not actual consumptive behavior. Dietary habits were assessed by a food frequency questionnaire.

Results

After the RYGB procedure, patients showed markedly lower aggregated PFS scores and sub-domain scores related to generally available, physically present, as well as tasted foods than before the surgery (all P?<?0.001). Changes in dietary habits after the surgery were characterized by a more frequent consumption of poultry, fish, eggs, and cooked vegetables (P?<?0.008) and a less frequent consumption of chocolate (P?<?0.048), cakes/biscuits/cookies (P?=?0.09), and fruit juice/soft drinks (P?=?0.08).

Conclusions

Data show a marked reduction of the hedonic drive to consume palatable food and beneficial changes in dietary habits characterized by an increased intake of protein-rich foods and vegetables and a reduced consumption of sugar-containing snacks and beverages after RYGB surgery. Based on these findings, it can be speculated that the reduction of the hedonic drive to consume palatable foods induced by RYGB surgery helps severely obese patients to establish healthier dietary habits.     

Implantatversagen an der Wirbelsäule

Background

Standard procedures are available for treatment of the most common spinal injuries. However, complications (e.g., implant failure and loosening) occur, which can make reoperation necessary.

Risks

Loosening of hardware, especially pedicel screws, can be due to osteoporosis or other pathological findings in the bone. On the other hand, an undersized implant can lead to implant failure because mechanical requirements cannot be met. In this article, several typical examples of complications are presented and discussed.

Prevention

The preoperative measurement of bone mineral density is helpful in making the decision concerning the correct implant device. The preoperative analysis of the degree of instability (e.g., with the Magerl classification) is also essential to select an adequate implant device.

Conclusion

The aim should be to preoperatively analyze bone quality and the mechanical requirements of the implant in order to reduce failure rates.     

The Torg-Pavlov ratio for the prediction of acute spinal cord injury after a minor trauma to the cervical spine

Background contextAcute cervical spinal cord injury (SCI) has been observed in some patients after a minor trauma to the cervical spine. The discrepancy between the severity of the trauma and the clinical symptoms has been attributed to spinal canal stenosis. However, to date, there is no universally established radiological parameter for identifying critical spinal stenosis in these patients. The spinal canal–to–vertebral body ratio (Torg-Pavlov ratio) has been proposed for assessing developmental spinal canal stenosis. The relevance of the Torg-Pavlov ratio for predicting the occurrence and severity of acute cervical SCI after a minor trauma to the cervical spine has not yet been established.PurposeTo investigate the Torg-Pavlov ratio values of the cervical spine in patients suffering from acute cervical SCI after a minor trauma to the cervical spine and the use of the Torg-Pavlov ratio for identifying patients at risk of cervical SCI and predicting the severity and course of symptoms.Study design/settingRetrospective radiological study of consecutive patients.Patient sampleForty-five patients suffering from acute cervical SCI and 68 patients showing no neurologic symptoms after a minor trauma to the cervical spine.Outcome measuresMidvertebral sagittal cervical spinal canal diameter and the sagittal vertebral body diameter. Calculation of the Torg-Pavlov ratio values.MethodsConventional lateral radiographs of the cervical spine (C3–C7) were analyzed to determine the Torg-Pavlov ratio values. Receiver operating characteristic curves were calculated for evaluating the classification accuracy of the Torg-Pavlov ratio for predicting SCI.ResultsThe Torg-Pavlov ratio values in the SCI group were significantly (p<.04) smaller compared with that in the control group. A Torg-Pavlov ratio cutoff value of 0.7 yielded the greatest positive likelihood ratio for predicting the occurrence of SCI. However, there were no significant differences in the Torg-Pavlov ratio values between the different American Spinal Injury Association Impairment Score groups and between patients with complete, partial, and no recovery of symptoms.ConclusionsDevelopmental cervical spinal canal stenosis assessed by the Torg-Pavlov ratio was characteristic for patients suffering from acute cervical SCI after a minor trauma to the cervical spine. Patients at risk of SCI after a minor trauma to the cervical spine can be identified by applying a Torg-Pavlov ratio cutoff value of 0.7. Other factors in addition to the spinal canal–to–vertebral body ratio affect the severity and course of symptoms as a result of cervical SCI.     

Neuron specific enolase and serum remain unaffected by ultra high frequency left prefrontal transcranial magnetic stimulation in patients with depression: a preliminary study

Serum levels of neuron specific enolase (NSE) and protein S-100 were analysed in 22 patients with depression, who got repetitive transcranial magnetic stimulation (rTMS) for 3 weeks with ultra high frequency stimulation or sham. NSE and S-100 at baseline and after 3 weeks did not differ between the groups. Neither in the ultra high frequency group, nor in the sham group a difference between baseline and end could be found. No evidence for a significant rise in brain damage markers in rTMS was found in this preliminary study.     

25 Jahre Notfall+Rettungsmedizin – reine Männersache?

Notfall + Rettungsmedizin -