Brains Of Animals Research Articles

Biomedical Engineering Research Based on Computer Propagation Technology: Treatment of neurodigestive diseases

With the support of the Institute of Cancer Hospital of Chifeng University, Sarkov and Markov Memorial Health Informatics Laboratory designed a new working concept of innovative Nursing by using neural network and Brain–computer interface technology. The research team proposed a direct connection between human or animal brain (or brain cell culture) and external equipment. In the case of one-way Brain–computer interface, the computer may accept commands from the brain. Using this point to detect the emotion of patients after surgery and carry out necessary gourds, a two-way information exchange method and model of two-way Brain–computer interface are also proposed. The potential non-invasive Brain–computer interface designed by us has been deeply studied, mainly because of its good time resolution, ease of use, portability and relatively low price. Especially in the specific application and working practice of EEG (Electroencephalography), our achievements directly meet the application of clinical institutions.

Prophylactic and therapeutic inhalation of two essential oils ameliorates scopolamine-induced cognitive impairment in mice

Clover and lemongrass essential oils of contrasting composition, at three concentration levels (1%, 5%, 10%), were administrated via prophylactic and therapeutic inhalation to scopolamine-treated mice. Chemical analysis showed that clover oil was dominant in eugenol (47.69%) and lemongrass free of eugenol but mainly containing monoterpenoids of comparable proportions. Animal behavioural and brain biochemical tests showed that injection of scopolamine caused memory and learning deficit in mice while prophylactic and therapeutic inhalation of two oils at moderate to high concentrations all obviously reversed the cognitive impairment via inhibiting acetylcholinesterase activities, oxidation and inflammation. Lemongrass essential oil with diverse monoterpenoids can be as effective as or a little bit more potent than eugenol-rich clover essential oil possibly due to the synergistic effect of various monoterpenoids. These findings implied that sniffing of such aroma recipes could be a promising complementary approach for the mitigation of Alzheimer’s disease-related cognitive impairment.

Entangled brains and the experience of pains.

The International Association for the Study of Pain (IASP) revised its definition of pain to "an unpleasant sensory and emotional experience." Three recent recommendations for understanding pain if there are no clear brain correlates include eliminativism, multiple realizability, and affordance-based approaches. I adumbrate a different path forward. Underlying each of the proposed approaches and the new IASP definition is the suspicion that there are no specific correlates for pain. I suggest that this basic assumption is misguided. As we learn more about brain function, it is becoming clear that many areas process many different types of information at the same time. In this study, I analogize how animal brains navigate in three-dimensional space with how the brain creates pain. Underlying both cases is a large-scale combinatorial system that feeds back on itself through a diversity of convergent and divergent bi-directional connections. Brains are not like combustion engines, with energy driving outputs via the structure of the machine, but are instead more like whirlpools, which are essentially dynamic patterns in some substrates. We should understand pain experiences as context-dependent, spatiotemporal trajectories that reflect heterogeneous, multiplex, and dynamically adaptive brain cells.

Antitumoral Activity of Cecropia Pachystachya Leaves Extract in Vitro and in Vivo Model of Rat Glioma: Brain and Blood Effects.

The aim of this study was to investigate the antiglioma effect of Cecropia pachystachya Trécul (CEC) leaves extract against C6 and U87 glioblastoma (GB) cells and in a rat preclinical GB model. The CEC extract reduced in vitro cell viability and biomass. In vivo, the extract decreased the tumor volume approximately 62%, without inducing systemic toxicity. The deficit in locomotion and memory and an anxiolytic-like behaviors induced in the GB model were minimized by CEC. The extract decreased the levels of reactive oxygen species, nitrites and thiobarbituric acid reactive substances and increased the activity of antioxidant enzymes in platelets, sera and brains of GB animals. The activity of NTPDases, 5'-nucleotidase and adenosine deaminase (ADA) was evaluated in lymphocytes, platelets and serum. In platelets, ATP and AMP hydrolysis was reduced and hydrolysis of ADP and the activity of ADA were increased in the control, while in CEC-treated animals no alteration in the hydrolysis of ADP was detected. In serum, the reduction in ATP hydrolysis was reversed by CEC. In lymphocytes, the increase in the hydrolysis of ATP, ADP and in the activity of ADA observed in GB model was altered by CEC administration. The observed increase in IL-6 and decrease in IL-10 levels in the serum of GB animals was reversed by CEC. These results demonstrate that CEC extract is a potential complementary treatment to GB, decreasing the tumor size, while modulating aspects of redox and purinergic systems.

An operating principle of the cerebral cortex, and a cellular mechanism for attentional trial-and-error pattern learning and useful classification extraction.

A feature of the brains of intelligent animals is the ability to learn to respond to an ensemble of active neuronal inputs with a behaviorally appropriate ensemble of active neuronal outputs. Previously, a hypothesis was proposed on how this mechanism is implemented at the cellular level within the neocortical pyramidal neuron: the apical tuft or perisomatic inputs initiate "guess" neuron firings, while the basal dendrites identify input patterns based on excited synaptic clusters, with the cluster excitation strength adjusted based on reward feedback. This simple mechanism allows neurons to learn to classify their inputs in a surprisingly intelligent manner. Here, we revise and extend this hypothesis. We modify synaptic plasticity rules to align with behavioral time scale synaptic plasticity (BTSP) observed in hippocampal area CA1, making the framework more biophysically and behaviorally plausible. The neurons for the guess firings are selected in a voluntary manner via feedback connections to apical tufts in the neocortical layer 1, leading to dendritic Ca2+ spikes with burst firing, which are postulated to be neural correlates of attentional, aware processing. Once learned, the neuronal input classification is executed without voluntary or conscious control, enabling hierarchical incremental learning of classifications that is effective in our inherently classifiable world. In addition to voluntary, we propose that pyramidal neuron burst firing can be involuntary, also initiated via apical tuft inputs, drawing attention toward important cues such as novelty and noxious stimuli. We classify the excitations of neocortical pyramidal neurons into four categories based on their excitation pathway: attentional versus automatic and voluntary/acquired versus involuntary. Additionally, we hypothesize that dendrites within pyramidal neuron minicolumn bundles are coupled via depolarization cross-induction, enabling minicolumn functions such as the creation of powerful hierarchical "hyperneurons" and the internal representation of the external world. We suggest building blocks to extend the microcircuit theory to network-level processing, which, interestingly, yields variants resembling the artificial neural networks currently in use. On a more speculative note, we conjecture that principles of intelligence in universes governed by certain types of physical laws might resemble ours.

Senolytics prevent age-associated changes in female mice brain

PurposeConsidering that the combination of dasatinib and quercetin (D + Q) demonstrated a neuroprotective action, as well as that females experience a decline in hormonal levels during aging and this is linked to increased susceptibility to Alzheimer’s disease, in this study we evaluated the effect of D + Q on inflammatory and oxidative stress markers and on acetylcholinesterase and Na+, K+-ATPase activities in brain of female mice. MethodsFemale C57BL/6 mice were divided in Control and D (5 mg/kg) + Q (50 mg/kg) treated. Treatment was administered via gavage for three consecutive days every two weeks starting at 30 days of age. The animals were euthanized at 6 months of age and at 14 months of age. ResultsResults indicate an increase in reactive species (RS), thiol content and lipid peroxidation followed by a reduction in nitrite levels and superoxide dismutase, catalase and glutathione S-transferase activity in the brain of control animals with age. D+Q protected against age-associated increase in RS and catalase activity reduction. Acetylcholinesterase activity was increased, while Na+, K+-ATPase activity was reduced at 14 months of age and D+Q prevented this reduction. ConclusionThese data demonstrate that D+Q can protect against age-associated neurochemical alterations in the female brain.

EFFECT OF ACTG(4-7)-PRO-GLY-PRO AND ACTG(6-9)-PRO-GLY-PRO ON THE INTENSITY OF REDOX PROCESSES AND BEHAVIOURAL STATUS OF RATS UNDER THYROID HYPERFUNCTION CONDITIONS

The aim of the work is to study the effect of melanocortins on the intensity of redox processes in the prefrontal region of the brain and the behavioral status of rats against the background of thyroid hyperfunction. Material and methods. In the experiment, the test animals were divided into the following groups (n = 10): intact rats (control); animals treated with sodium salt pentahydrate L-thyroxine (hyperthyroidism); rats receiving ACTH (4-7)-Pro-Gly-Pro and individuals receiving ACTH (6-9)-Pro-Gly-Pro, re-spectively, intraperitoneally daily for 21 days, starting from day 22 of administration of sodium salt pentahydrate L-thyroxine. Hyperthyroidism was simulated in animals by intragastric administration of L-thyroxine sodium salt pentahydrate for 42 days. The intensity of lipoperoxidation processes was studied by the content of diene and triene conjugates in the prefrontal zone tissue, the initial level of TBА-reactive products, and the rates of spon-taneous and ascorbic peroxidation of lipids. The level of protein peroxidation products was determined by the reaction of oxidized amino acid residues of proteins with 2,4-dinitrophenyl hydrazone. Evaluation of the enzymatic unit of the antioxidant system of the prefrontal region was carried out by de-termining the activity of superoxide dismutase and catalase. The behavioral status of laboratory rodents was studied using the «Hole board» test. Results. The use of ACTH(4-7)-Pro-Gly-Pro and ACTH(6-9)-Pro-Gly-Pro compounds under experimental hyperthyroidism led to a decrease in the intensity of the processes of peroxidation of lipids, proteins and the restoration of levels of activity of antioxidant enzymes – superoxide dismutase and catalase in the tissue of the prefrontal region of the brain of animals, as well as correction behavioral indicators in the «Hole board» test. Conclusion. The obtained experimental data indicate that ACTH(4-7)-Pro-Gly-Pro and ACTH(6-9)-Pro-Gly-Pro show antiperoxy and antioxidant activity against lipoperoxidation parameters and oxidative modification of proteins and enzymatic protection systems in the prefrontal brain zone tissue, as well as exert psychocorregating action on behavioral responses of white rats against the background of thyroid hyperfunction.

Developing a non-cadaveric brain tumour surgery lab in resource-constrained settings.

To develop the country's first brain tumour surgery lab in resource-constrained settings, for training young neurosurgeons and residents. A workshop was developed using mixed-fidelity models for assessing and training a participant's psychomotor skills, hand-eye coordination, and teaching the principles of brain tumour surgery. Affordable noncadaveric models were used to compare and contrast the benefit of each teaching model. Within the existing space for wet labs at our institution, 8 different dissection stations were set up with adequate space for 2 people to work at a time. Each station was equipped with an operating room-Caliber microscope, a lighting system and a camera linked to a screen and high-powered electric drills and basic surgical equipment. Our team was able to develop and use 3D-printed skull models and animal brain models for training in complex approaches and craniotomy. Surgical simulation training, in a cost-effective manner, provides the benefit of training residents and students in neurosurgical techniques in a safe, controlled environment leading to improvement in skills and technique.

Systematic development of immunohistochemistry protocol for large cryosections-specific to non-perfused fetal brain

BackgroundImmunohistochemistry (IHC) is an important technique in understanding the expression of neurochemical molecules in the developing human brain. Despite its routine application in the research and clinical setup, the IHC protocol specific for soft fragile fetal brains that are fixed using the non-perfusion method is still limited in studying the whole brain. New methodThis study shows that the IHC protocols, using a chromogenic detection system, used in animals and adult humans are not optimal in the fetal brains. We have optimized key steps from Antigen retrieval (AR) to chromogen visualization for formalin-fixed whole-brain cryosections (20 µm) mounted on glass slides. ResultsWe show the results from six validated, commonly used antibodies to study the fetal brain. We achieved optimal antigen retrieval with 0.1 M Boric Acid, pH 9.0 at 70°C for 20 minutes. We also present the optimal incubation duration and temperature for protein blocking and the primary antibody that results in specific antigen labeling with minimal tissue damage. Comparison with existing methodsThe IHC protocol commonly used for adult human and animal brains results in significant tissue damage in the fetal brains with little or suboptimal antigen expression. Our new method with important modifications including the temperature, duration, and choice of the alkaline buffer for AR addresses these pitfalls and provides high-quality results. ConclusionThe optimized IHC protocol for the developing human brain (13–22 GW) provides a high-quality, repeatable, and reliable method for studying chemoarchitecture in neurotypical and pathological conditions across different gestational ages.

18F]pFBC, a Covalent CLIP-Tag Radiotracer for Detection of Viral Reporter Gene Transfer in the Murine Brain.

Preclinical models of neurological diseases and gene therapy are essential for neurobiological research. However, the evaluation of such models lacks reliable reporter systems for use with noninvasive imaging methods. Here, we report the development of a reporter system based on the CLIP-tag enzyme and [18F]pFBC, an 18F-labeled covalent CLIP-tag-ligand synthesized via a DoE-optimized and fully automated process. We demonstrated its specificity using a subcutaneous xenograft model and a model of viral vector-mediated brain gene transfer by engineering HEK293 cells and striatal neurons to express membrane-tethered CLIP-tag protein. After in vitro characterization of the reporter, mice carrying either CLIP-tag expressing or control subcutaneous xenografts underwent dynamic [18F]pFBC PET imaging. The CLIP-tag expressing xenografts showed a significantly higher uptake than control xenografts (tumor-to-muscle ratio 5.0 vs 1.7, p = 0.0379). In vivo, metabolite analysis by radio-HPLC from plasma and brain homogenates showed only one radio-metabolite in plasma and none in the brain. In addition, [18F]pFBC showed fast uptake and rapid clearance from the brain in animals injected with adeno-associated virus (AAV)-CLIP in the right striatum but no right-to-left (R-L) uptake difference in the striata in the acquired PET data. In contrast, autoradiography showed a clear accumulation of radioactivity in the AAV-CLIP-injected right striatum compared to the sham-injected left striatum control. CLIP-tag expression and brain integrity were verified by immunofluorescence and light sheet microscopy. In conclusion, we established a novel reporter gene system for PET imaging of gene expression in the brain and periphery and demonstrated its potential for a wide range of applications, particularly for neurobiological research and gene therapy with viral vectors.

Abstract TP33: Knockout of Kruppel-Like Factor 4 in Brain Endothelial Cells Accelerates Vascular and Neuronal Degeneration During Aging

As we get older, various aspects of our bodies start to decline, including brain function. The mechanisms behind the decline in brain function due to aging are still not well understood. The blood-brain barrier (BBB) is crucial for maintaining brain health and homeostasis by controlling both passive and active exchange of materials between the blood and brain. This barrier is predominantly composed of endothelial cells, which deteriorate in both aging and neurodegenerative disorders. Endothelial cells are also highly enriched in the Kruppel-like factor 4 (KLF4) transcription factor, which is reduced in expression as we age. In this study, we report that endothelial-specific KLF4 KO mice demonstrate accelerated brain aging, including accelerated BBB deterioration, neurodegeneration, and cognitive decline. Single-cell RNA sequencing from brain endothelial cells of endothelial-specific KLF4 KO mice demonstrate aberrantly high expression of adaptive and innate immune response genes, and live animal brain imaging across the lifespan reveals accelerated aging-related BBB deterioration, decreased blood flow, and impaired neurovascular coupling. Endothelial-specific KLF4 KO mice show increased neuroinflammation and neutrophil infiltration. Our data suggest that diminished endothelial cell KLF signaling with age could be a novel therapeutic target to preserve health and function of the aging brain.

Bioorthogonal chemical labeling of endogenous neurotransmitter receptors in living mouse brains

Neurotransmitter receptors are essential components of synapses for communication between neurons in the brain. Because the spatiotemporal expression profiles and dynamics of neurotransmitter receptors involved in many functions are delicately governed in the brain, in vivo research tools with high spatiotemporal resolution for receptors in intact brains are highly desirable. Covalent labeling by chemical reaction (chemical labeling) of proteins without genetic manipulation is now a powerful method for analyzing receptors in vitro. However, selective target receptor labeling in the brain has not yet been achieved. This study shows that ligand-directed alkoxyacylimidazole (LDAI) chemistry can be used to selectively tether synthetic probes to target endogenous receptors in living mouse brains. The reactive LDAI reagents with negative charges were found to diffuse well over the whole brain and could selectively label target endogenous receptors, including AMPAR, NMDAR, mGlu1, and GABAAR. This simple and robust labeling protocol was then used for various applications: three-dimensional spatial mapping of endogenous receptors in the brains of healthy and disease-model mice; multi-color receptor imaging; and pulse-chase analysis of the receptor dynamics in postnatal mouse brains. Here, results demonstrated that bioorthogonal receptor modification in living animal brains may provide innovative molecular tools that contribute to the in-depth understanding of complicated brain functions.

Brain-inspired chaotic spiking backpropagation.

Spiking neural networks (SNNs) have superior energy efficiency due to their spiking signal transmission, which mimics biological nervous systems, but they are difficult to train effectively. Although surrogate gradient-based methods offer a workable solution, trained SNNs frequently fall into local minima because they are still primarily based on gradient dynamics. Inspired by the chaotic dynamics in animal brain learning, we propose a chaotic spiking backpropagation (CSBP) method that introduces a loss function to generate brain-like chaotic dynamics and further takes advantage of the ergodic and pseudo-random nature to make SNN learning effective and robust. From a computational viewpoint, we found that CSBP significantly outperforms current state-of-the-art methods on both neuromorphic data sets (e.g. DVS-CIFAR10 and DVS-Gesture) and large-scale static data sets (e.g. CIFAR100 and ImageNet) in terms of accuracy and robustness. From a theoretical viewpoint, we show that the learning process of CSBP is initially chaotic, then subject to various bifurcations and eventually converges to gradient dynamics, consistently with the observation of animal brain activity. Our work provides a superior core tool for direct SNN training and offers new insights into understanding the learning process of a biological brain.

Mitigating Age-Related Cognitive Decline and Oxidative Status in Rats Treated with Catechin and Polyphenon-60.

Aging is a normal physiological process influenced by the combination of multiple mechanisms, primarily oxidative stress and neuroinflammation, which impact general physiology and brain function. Phenolic compounds have demonstrated the ability to slow down the aging process of the brain due to their antioxidant and anti-inflammatory effects. This study assessed the protective properties of catechin and polyphenon-60 in non-pathologically aged rats regarding visuo-spatial learning and the oxidative status of the frontal cortex. Old animals were treated with catechin or green tea extract (polyphenon-60) for 36 days, daily. Healthy old and young rats were used as controls. During the first training phase, treated rats executed the test better, locating the target in less time compared with the controls. Biomarkers of oxidative stress (catalase activities, superoxide dismutase, glutathione reductase, and glutathione S-transferase) were reduced in the brain of old animals, although their activities were partially improved after both antioxidant treatments. Furthermore, the rise in the production of reactive oxygen species and malondialdehyde levels-a marker of lipid peroxidation-in the frontal cortex of aged animals was significantly ameliorated after the interventions. In conclusion, old rats exhibited enhanced cognitive function and reduced stress levels following the administration of catechin and polyphenon-60.

Neurophysiology of male sexual arousal—Behavioral perspective

In the presented review, we analyzed the physiology of male sexual arousal and its relation to the motivational aspects of this behavior. We highlighted the distinction between these processes based on observable physiological and behavioral parameters. Thus, we proposed the experimentally applicable differentiation between sexual arousal (SA) and sexual motivation (SM). We propose to define sexual arousal as an overall autonomic nervous system response leading to penile erection, triggered selectively by specific sexual cues. These autonomic processes include both spinal and supraspinal neuronal networks, activated by sensory pathways including information from sexual partner and sexual context, as well as external and internal genital organs. To avoid misinterpretation of experimental data, we also propose to precise the term “sexual motivation” as all actions performed by the individual that increase the probability of sexual interactions or increase the probability of exposition to sexual context cues. Neuronal structures such as the amygdala, bed nucleus of stria terminalis, hypothalamus, nucleus raphe, periaqueductal gray, and nucleus paragigantocellularis play crucial roles in controlling the level of arousal and regulating peripheral responses via specific autonomic effectors. On the highest level of CNS, the activity of cortical structures involved in the regulation of the autonomic nervous system, such as the insula and anterior cingulate cortex, can visualize an elevated level of SA in both animal and human brains. From a preclinical perspective, we underlie the usefulness of the non-contact erection test (NCE) procedure in understanding factors influencing sexual arousal, including studies of sexual preference in animal models. Taken together results obtained by different methods, we wanted to focus attention on neurophysiological aspects that are distinctly related to sexual arousal and can be used as an objective parameter, leading to higher translational transparency between basic, preclinical, and clinical studies.

Accelerated Neuroimmune Dysfunction in Aged HIV-1-Infected Humanized Mice.

Disordered immunity, aging, human immunodeficiency virus type one (HIV-1) infection, and responses to antiretroviral therapy are linked. However, how each factor is linked with the other(s) remains incompletely understood. It has been reported that accelerated aging, advanced HIV-1 infection, inflammation, and host genetic factors are associated with host cellular, mitochondrial, and metabolic alterations. However, the underlying mechanism remains elusive. With these questions in mind, we used chronically HIV-1-infected CD34-NSG humanized mice (hu-mice) to model older people living with HIV and uncover associations between HIV-1 infection and aging. Adult humanized mice were infected with HIV-1 at the age of 20 weeks and maintained for another 40 weeks before sacrifice. Animal brains were collected and subjected to transcriptomics, qPCR, and immunofluorescence assays to uncover immune disease-based biomarkers. CD4+ T cell decline was associated with viral level and age. Upregulated C1QA, CD163, and CXCL16 and downregulated LMNA and CLU were identified as age-associated genes tied to HIV-1 infection. Ingenuity pathway analysis affirmed links to innate immune activation, pyroptosis signaling, neuroinflammation, mitochondrial dysfunction, cellular senescence, and neuronal dysfunction. In summary, CD34-NSG humanized mice are identified as a valuable model for studying HIV-1-associated aging. Biomarkers of immune senescence and neuronal signaling are both age- and virus-associated. By exploring the underlying biological mechanisms that are linked to these biomarkers, interventions for next generation HIV-1-infected patients can be realized.

Single-cell transcriptomics reveals that glial cells integrate homeostatic and circadian processes to drive sleep–wake cycles

The sleep–wake cycle is determined by circadian and sleep homeostatic processes. However, the molecular impact of these processes and their interaction in different brain cell populations are unknown. To fill this gap, we profiled the single-cell transcriptome of adult Drosophila brains across the sleep–wake cycle and four circadian times. We show cell type-specific transcriptomic changes, with glia displaying the largest variation. Glia are also among the few cell types whose gene expression correlates with both sleep homeostat and circadian clock. The sleep–wake cycle and sleep drive level affect the expression of clock gene regulators in glia, and disrupting clock genes specifically in glia impairs homeostatic sleep rebound after sleep deprivation. These findings provide a comprehensive view of the effects of sleep homeostatic and circadian processes on distinct cell types in an entire animal brain and reveal glia as an interaction site of these two processes to determine sleep–wake dynamics.

Implantation of Flexible Electrodes for Simultaneous in-vivo Extracellular Recording and Two-Photon Imaging

Introduction: Rigid silicon electrodes like Utah array grids and Neuropixel probes have been used in human and animal brain models to understand the dynamics of neural computation, treat neurodegenerative disorders, and act as brain-machine-interfaces. However, when implanted chronically, glial proliferation can rapidly disrupt the interaction between neurons and electrodes, drastically reducing recording fidelity. The development of flexible electrodes has the potential to minimize tissue damage and inflammation, which allows for long-term recordings over several months. In line with this objective, the Nano-neurotechnology Lab at Purdue University has developed a 6-µm thick, flexible, and biocompatible Parylene probe to facilitate chronic recordings in awake mice. However, flexible electrodes present a unique engineering challenge as the force required to insert into the brain causes the probe to buckle and fail during insertion. 
 Methods and Results: Here, I designed a micropipette shuttle using a glass micropipette and custom insertion system which provided reproducible probe implantation into the cortex. The implantation device was designed in CAD software and 3D-printed for rapid prototyping. The procedure was developed on brain phantoms made of 0.6% agarose with a comparable Young’s modulus to mouse brain tissue. Utilizing 3D-printed pieces and the surface tension of diluted poly-vinyl-acrylate adhesive to align the probe to a micropipette, insertion of the electrode and retraction of the shuttle was accomplished in awake mice. 
 Conclusion: The implications of flexible recording electrodes are extensive. Long-term implantation opens the door for understanding behavioral and learning dynamics over time. Moreover, the flexibility of these probes allows for the combination of 2-photon optical microscopy, thus enabling multi-modal investigation of neuronal physiology. A low-cost, consistent procedure is the first step in the implementation of these flexible probes for further advancements in fundamental neuroscience research and its potential applications in human and animal studies.

Application of proteomics in brain's aging research

Proteomics is one of the commonly used techniques to explore the protein composition or protein modification status in various healthy or diseased brain tissues in the past decades. Aging is an extremely complex biological process including physiological function decline with age increasing. To have a better understanding of protein changes along with aging, proteomics has been applied in aging-associated research trying to uncover protein changes or post-translational modification (PTM) occurs in aging with the advantage of screening proteins on a large scale. In this review, we summarized protein expression differences detected by proteomics in human or animal brains at different age stages. Protein differences among species or brain regions are obvious, which reminds us to carefully consider these factors in brain aging research. Important protein changes have been found in multiple brain regions in the aging process and these differentially expressed proteins are mainly involved in cellular components, activities of metabolism, mitochondria changes, oxidative modification and some specific signaling pathways.

Engineered serum markers for non-invasive monitoring of gene expression in the brain.

Measurement of gene expression in the brain requires invasive analysis of brain tissue or non-invasive methods that are limited by low sensitivity. Here we introduce a method for non-invasive, multiplexed, site-specific monitoring of endogenous gene or transgene expression in the brain through engineered reporters called released markers of activity (RMAs). RMAs consist of an easily detectable reporter and a receptor-binding domain that enables transcytosis across the brain endothelium. RMAs are expressed in the brain but exit into the blood, where they can be easily measured. We show that expressing RMAs at a single mouse brain site representing approximately 1% of the brain volume provides up to a 100,000-fold signal increase over the baseline. Expression of RMAs in tens to hundreds of neurons is sufficient for their reliable detection. We demonstrate that chemogenetic activation of cells expressing Fos-responsive RMA increases serum RMA levels >6-fold compared to non-activated controls. RMAs provide a non-invasive method for repeatable, multiplexed monitoring of gene expression in the intact animal brain.