Alterations in social behavior are among the major negative consequences observed in children with Fetal Alcohol Spectrum Disorders (FASDs). Several independent laboratories have demonstrated robust alterations in the social behavior of rodents exposed to alcohol during brain development across a wide range of exposure durations, timing, doses, and ages at the time of behavioral quantification. Prior work from this laboratory has identified reliable alterations in specific forms of social interaction following moderate prenatal alcohol exposure (PAE) in the rat that persist well into adulthood, including increased wrestling and decreased investigation. These behavioral alterations have been useful in identifying neural circuits altered by moderate PAE1, and may hold importance for progressing toward a more complete understanding of the neural bases of PAE-related alterations in social behavior. This paper describes procedures for performing moderate PAE in which rat dams voluntarily consume ethanol or saccharin (control) throughout gestation, and measurement of social behaviors in adult offspring.
20 Related JoVE Articles!
An Affordable HIV-1 Drug Resistance Monitoring Method for Resource Limited Settings
Institutions: University of KwaZulu-Natal, Durban, South Africa, Jembi Health Systems, University of Amsterdam, Stanford Medical School.
HIV-1 drug resistance has the potential to seriously compromise the effectiveness and impact of antiretroviral therapy (ART). As ART programs in sub-Saharan Africa continue to expand, individuals on ART should be closely monitored for the emergence of drug resistance. Surveillance of transmitted drug resistance to track transmission of viral strains already resistant to ART is also critical. Unfortunately, drug resistance testing is still not readily accessible in resource limited settings, because genotyping is expensive and requires sophisticated laboratory and data management infrastructure. An open access genotypic drug resistance monitoring method to manage individuals and assess transmitted drug resistance is described. The method uses free open source software for the interpretation of drug resistance patterns and the generation of individual patient reports. The genotyping protocol has an amplification rate of greater than 95% for plasma samples with a viral load >1,000 HIV-1 RNA copies/ml. The sensitivity decreases significantly for viral loads <1,000 HIV-1 RNA copies/ml. The method described here was validated against a method of HIV-1 drug resistance testing approved by the United States Food and Drug Administration (FDA), the Viroseq genotyping method. Limitations of the method described here include the fact that it is not automated and that it also failed to amplify the circulating recombinant form CRF02_AG from a validation panel of samples, although it amplified subtypes A and B from the same panel.
Medicine, Issue 85, Biomedical Technology, HIV-1, HIV Infections, Viremia, Nucleic Acids, genetics, antiretroviral therapy, drug resistance, genotyping, affordable
A Mouse Model for Pathogen-induced Chronic Inflammation at Local and Systemic Sites
Institutions: Boston University School of Medicine, Boston University School of Medicine.
Chronic inflammation is a major driver of pathological tissue damage and a unifying characteristic of many chronic diseases in humans including neoplastic, autoimmune, and chronic inflammatory diseases. Emerging evidence implicates pathogen-induced chronic inflammation in the development and progression of chronic diseases with a wide variety of clinical manifestations. Due to the complex and multifactorial etiology of chronic disease, designing experiments for proof of causality and the establishment of mechanistic links is nearly impossible in humans. An advantage of using animal models is that both genetic and environmental factors that may influence the course of a particular disease can be controlled. Thus, designing relevant animal models of infection represents a key step in identifying host and pathogen specific mechanisms that contribute to chronic inflammation.
Here we describe a mouse model of pathogen-induced chronic inflammation at local and systemic sites following infection with the oral pathogen Porphyromonas gingivalis
, a bacterium closely associated with human periodontal disease. Oral infection of specific-pathogen free mice induces a local inflammatory response resulting in destruction of tooth supporting alveolar bone, a hallmark of periodontal disease. In an established mouse model of atherosclerosis, infection with P. gingivalis
accelerates inflammatory plaque deposition within the aortic sinus and innominate artery, accompanied by activation of the vascular endothelium, an increased immune cell infiltrate, and elevated expression of inflammatory mediators within lesions. We detail methodologies for the assessment of inflammation at local and systemic sites. The use of transgenic mice and defined bacterial mutants makes this model particularly suitable for identifying both host and microbial factors involved in the initiation, progression, and outcome of disease. Additionally, the model can be used to screen for novel therapeutic strategies, including vaccination and pharmacological intervention.
Immunology, Issue 90,
Pathogen-Induced Chronic Inflammation; Porphyromonas gingivalis; Oral Bone Loss; Periodontal Disease; Atherosclerosis; Chronic Inflammation; Host-Pathogen Interaction; microCT; MRI
Construction of Vapor Chambers Used to Expose Mice to Alcohol During the Equivalent of all Three Trimesters of Human Development
Institutions: University of New Mexico Health Sciences Center.
Exposure to alcohol during development can result in a constellation of morphological and behavioral abnormalities that are collectively known as Fetal Alcohol Spectrum Disorders (FASDs). At the most severe end of the spectrum is Fetal Alcohol Syndrome (FAS), characterized by growth retardation, craniofacial dysmorphology, and neurobehavioral deficits. Studies with animal models, including rodents, have elucidated many molecular and cellular mechanisms involved in the pathophysiology of FASDs. Ethanol administration to pregnant rodents has been used to model human exposure during the first and second trimesters of pregnancy. Third trimester ethanol consumption in humans has been modeled using neonatal rodents. However, few rodent studies have characterized the effect of ethanol exposure during the equivalent to all three trimesters of human pregnancy, a pattern of exposure that is common in pregnant women. Here, we show how to build vapor chambers from readily obtainable materials that can each accommodate up to six standard mouse cages. We describe a vapor chamber paradigm that can be used to model exposure to ethanol, with minimal handling, during all three trimesters. Our studies demonstrate that pregnant dams developed significant metabolic tolerance to ethanol. However, neonatal mice did not develop metabolic tolerance and the number of fetuses, fetus weight, placenta weight, number of pups/litter, number of dead pups/litter, and pup weight were not significantly affected by ethanol exposure. An important advantage of this paradigm is its applicability to studies with genetically-modified mice. Additionally, this paradigm minimizes handling of animals, a major confound in fetal alcohol research.
Medicine, Issue 89, fetal, ethanol, exposure, paradigm, vapor, development, alcoholism, teratogenic, animal, mouse, model
A Procedure to Observe Context-induced Renewal of Pavlovian-conditioned Alcohol-seeking Behavior in Rats
Institutions: Concordia University.
Environmental contexts in which drugs of abuse are consumed can trigger craving, a subjective Pavlovian-conditioned response that can facilitate drug-seeking behavior and prompt relapse in abstinent drug users. We have developed a procedure to study the behavioral and neural processes that mediate the impact of context on alcohol-seeking behavior in rats. Following acclimation to the taste and pharmacological effects of 15% ethanol in the home cage, male Long-Evans rats receive Pavlovian discrimination training (PDT) in conditioning chambers. In each daily (Mon-Fri) PDT session, 16 trials each of two different 10 sec auditory conditioned stimuli occur. During one stimulus, the CS+, 0.2 ml of 15% ethanol is delivered into a fluid port for oral consumption. The second stimulus, the CS-, is not paired with ethanol. Across sessions, entries into the fluid port during the CS+ increase, whereas entries during the CS- stabilize at a lower level, indicating that a predictive association between the CS+ and ethanol is acquired. During PDT each chamber is equipped with a specific configuration of visual, olfactory and tactile contextual stimuli. Following PDT, extinction training is conducted in the same chamber that is now equipped with a different configuration of contextual stimuli. The CS+ and CS- are presented as before, but ethanol is withheld, which causes a gradual decline in port entries during the CS+. At test, rats are placed back into the PDT context and presented with the CS+ and CS- as before, but without ethanol. This manipulation triggers a robust and selective increase in the number of port entries made during the alcohol predictive CS+, with no change in responding during the CS-. This effect, referred to as context-induced renewal, illustrates the powerful capacity of contexts associated with alcohol consumption to stimulate alcohol-seeking behavior in response to Pavlovian alcohol cues.
Behavior, Issue 91, Behavioral neuroscience, alcoholism, relapse, addiction, Pavlovian conditioning, ethanol, reinstatement, discrimination, conditioned approach
Design and Implementation of an fMRI Study Examining Thought Suppression in Young Women with, and At-risk, for Depression
Institutions: McMaster University, McMaster University, University of Calgary, McMaster University.
Ruminative brooding is associated with increased vulnerability to major depression. Individuals who regularly ruminate will often try to reduce the frequency of their negative thoughts by actively suppressing them. We aim to identify the neural correlates underlying thought suppression in at-risk and depressed individuals. Three groups of women were studied; a major depressive disorder group, an at-risk group (having a first degree relative with depression) and controls. Participants performed a mixed block-event fMRI paradigm involving thought suppression, free thought and motor control periods. Participants identified the re-emergence of “to-be-suppressed” thoughts (“popping” back into conscious awareness) with a button press. During thought suppression the control group showed the greatest activation of the dorsolateral prefrontal cortex, followed by the at-risk, then depressed group. During the re-emergence of intrusive thoughts compared to successful re-suppression of those thoughts, the control group showed the greatest activation of the anterior cingulate cortices, followed by the at-risk, then depressed group. At-risk participants displayed anomalies in the neural regulation of thought suppression resembling the dysregulation found in depressed individuals. The predictive value of these changes in the onset of depression remains to be determined.
Behavior, Issue 99, Major Depressive Disorder, Risk, Thought Suppression, fMRI, Women, Rumination, Thought Intrusion
EPA Method 1615. Measurement of Enterovirus and Norovirus Occurrence in Water by Culture and RT-qPCR. I. Collection of Virus Samples
Institutions: U.S Environmental Protection Agency, U.S Environmental Protection Agency.
EPA Method 1615 was developed with a goal of providing a standard method for measuring enteroviruses and noroviruses in environmental and drinking waters. The standardized sampling component of the method concentrates viruses that may be present in water by passage of a minimum specified volume of water through an electropositive cartridge filter. The minimum specified volumes for surface and finished/ground water are 300 L and 1,500 L, respectively. A major method limitation is the tendency for the filters to clog before meeting the sample volume requirement. Studies using two different, but equivalent, cartridge filter options showed that filter clogging was a problem with 10% of the samples with one of the filter types compared to 6% with the other filter type. Clogging tends to increase with turbidity, but cannot be predicted based on turbidity measurements only. From a cost standpoint one of the filter options is preferable over the other, but the water quality and experience with the water system to be sampled should be taken into consideration in making filter selections.
Environmental Sciences, Issue 97, enteric virus, environmental microbiology, water, virus occurrence, electropositive cartridge filters, sample collection
Adapting Human Videofluoroscopic Swallow Study Methods to Detect and Characterize Dysphagia in Murine Disease Models
Institutions: University of Missouri, University of Missouri, University of Missouri.
This study adapted human videofluoroscopic swallowing study (VFSS) methods for use with murine disease models for the purpose of facilitating translational dysphagia research. Successful outcomes are dependent upon three critical components: test chambers that permit self-feeding while standing unrestrained in a confined space, recipes that mask the aversive taste/odor of commercially-available oral contrast agents, and a step-by-step test protocol that permits quantification of swallow physiology. Elimination of one or more of these components will have a detrimental impact on the study results. Moreover, the energy level capability of the fluoroscopy system will determine which swallow parameters can be investigated. Most research centers have high energy fluoroscopes designed for use with people and larger animals, which results in exceptionally poor image quality when testing mice and other small rodents. Despite this limitation, we have identified seven VFSS parameters that are consistently quantifiable in mice when using a high energy fluoroscope in combination with the new murine VFSS protocol. We recently obtained a low energy fluoroscopy system with exceptionally high imaging resolution and magnification capabilities that was designed for use with mice and other small rodents. Preliminary work using this new system, in combination with the new murine VFSS protocol, has identified 13 swallow parameters that are consistently quantifiable in mice, which is nearly double the number obtained using conventional (i.e.,
high energy) fluoroscopes. Identification of additional swallow parameters is expected as we optimize the capabilities of this new system. Results thus far demonstrate the utility of using a low energy fluoroscopy system to detect and quantify subtle changes in swallow physiology that may otherwise be overlooked when using high energy fluoroscopes to investigate murine disease models.
Medicine, Issue 97, mouse, murine, rodent, swallowing, deglutition, dysphagia, videofluoroscopy, radiation, iohexol, barium, palatability, taste, translational, disease models
Non-invasive Assessment of the Efficacy of New Therapeutics for Intestinal Pathologies Using Serial Endoscopic Imaging of Live Mice
Institutions: The Walter and Eliza Hall Institute for Medical Research, University of Melbourne, Olivia Newton-John Cancer Research Institute.
Animal models of inflammatory bowel disease (IBD) and colorectal cancer (CRC) have provided significant insight into the cell intrinsic and extrinsic mechanisms that contribute to the onset and progression of intestinal diseases. The identification of new molecules that promote these pathologies has led to a flurry of activity focused on the development of potential new therapies to inhibit their function. As a result, various pre-clinical mouse models with an intact immune system and stromal microenvironment are now heavily used. Here we describe three experimental protocols to test the efficacy of new therapeutics in pre-clinical models of (1) acute mucosal damage, (2) chronic colitis and/or colitis-associated colon cancer, and (3) sporadic colorectal cancer. We also outline procedures for serial endoscopic examination that can be used to document the therapeutic response of an individual tumor and to monitor the health of individual mice. These protocols provide complementary experimental platforms to test the effectiveness of therapeutic compounds shown to be well tolerated by mice.
Medicine, Issue 97, cancer, colitis, colon, endoscopy, mucosa, therapy.
Glass Wool Filters for Concentrating Waterborne Viruses and Agricultural Zoonotic Pathogens
Institutions: United States Geological Survey, University of Wisconsin – Madison, United States Department of Agriculture, United States Geological Survey.
The key first step in evaluating pathogen levels in suspected contaminated water is concentration. Concentration methods tend to be specific for a particular pathogen group, for example US Environmental Protection Agency Method 1623 for Giardia
, which means multiple methods are required if the sampling program is targeting more than one pathogen group. Another drawback of current methods is the equipment can be complicated and expensive, for example the VIRADEL method with the 1MDS cartridge filter for concentrating viruses2
. In this article we describe how to construct glass wool filters for concentrating waterborne pathogens. After filter elution, the concentrate is amenable to a second concentration step, such as centrifugation, followed by pathogen detection and enumeration by cultural or molecular methods. The filters have several advantages. Construction is easy and the filters can be built to any size for meeting specific sampling requirements. The filter parts are inexpensive, making it possible to collect a large number of samples without severely impacting a project budget. Large sample volumes (100s to 1,000s L) can be concentrated depending on the rate of clogging from sample turbidity. The filters are highly portable and with minimal equipment, such as a pump and flow meter, they can be implemented in the field for sampling finished drinking water, surface water, groundwater, and agricultural runoff. Lastly, glass wool filtration is effective for concentrating a variety of pathogen types so only one method is necessary. Here we report on filter effectiveness in concentrating waterborne human enterovirus, Salmonella enterica, Cryptosporidium parvum
, and avian influenza virus.
Immunology, Issue 61, avian influenza virus, environmental sampling, Cryptosporidium, pathogen concentration, Salmonella, water, waterborne disease, waterborne pathogens
Investigating Intestinal Inflammation in DSS-induced Model of IBD
Institutions: McMaster University .
Inflammatory bowel disease (IBD) encompasses a range of intestinal pathologies, the most common of which are ulcerative colitis (UC) and Crohn's Disease (CD). Both UC and CD, when present in the colon, generate a similar symptom profile which can include diarrhea, rectal bleeding, abdominal pain, and weight loss.1
Although the pathogenesis of IBD remains unknown, it is described as a multifactorial disease that involves both genetic and environmental components.2
There are numerous and variable animal models of colonic inflammation that resemble several features of IBD. Animal models of colitis range from those arising spontaneously in susceptible strains of certain species to those requiring administration of specific concentrations of colitis-inducing chemicals, such as dextran sulphate sodium (DSS). Chemical-induced models of gut inflammation are the most commonly used and best described models of IBD. Administration of DSS in drinking water produces acute or chronic colitis depending on the administration protocol.3
Animals given DSS exhibit weight loss and signs of loose stool or diarrhea, sometimes with evidence of rectal bleeding.4,5
Here, we describe the methods by which colitis development and the resulting inflammatory response can be characterized following administration of DSS. These methods include histological analysis of hematoxylin/eosin stained colon sections, measurement of pro-inflammatory cytokines, and determination of myeloperoxidase (MPO) activity, which can be used as a surrogate marker of inflammation.6
The extent of the inflammatory response in disease state can be assessed by the presence of clinical symptoms or by alteration in histology in mucosal tissue. Colonic histological damage is assessed by using a scoring system that considers loss of crypt architecture, inflammatory cell infiltration, muscle thickening, goblet cell depletion, and crypt abscess.7
Quantitatively, levels of pro-inflammatory cytokines with acute inflammatory properties, such as interleukin (IL)-1β, IL-6 and tumour necrosis factor (TNF)-α,can be determined using conventional ELISA methods. In addition, MPO activity can be measured using a colorimetric assay and used as an index of inflammation.8
In experimental colitis, disease severity is often correlated with an increase in MPO activity and higher levels of pro-inflammatory cytokines. Colitis severity and inflammation-associated damage can be assessed by examining stool consistency and bleeding, in addition to assessing the histopathological state of the intestine using hematoxylin/eosin stained colonic tissue sections. Colonic tissue fragments can be used to determine MPO activity and cytokine production. Taken together, these measures can be used to evaluate the intestinal inflammatory response in animal models of experimental colitis.
Medicine, Issue 60, inflammation, myeloperoxidase (MPO), acute colonic damage, granulocyte, colon, dextran sulfate sodium (DSS), neutrophil
Aseptic Laboratory Techniques: Plating Methods
Institutions: University of California, Los Angeles .
Microorganisms are present on all inanimate surfaces creating ubiquitous sources of possible contamination in the laboratory. Experimental success relies on the ability of a scientist to sterilize work surfaces and equipment as well as prevent contact of sterile instruments and solutions with non-sterile surfaces. Here we present the steps for several plating methods routinely used in the laboratory to isolate, propagate, or enumerate microorganisms such as bacteria and phage. All five methods incorporate aseptic technique, or procedures that maintain the sterility of experimental materials. Procedures described include (1) streak-plating bacterial cultures to isolate single colonies, (2) pour-plating and (3) spread-plating to enumerate viable bacterial colonies, (4) soft agar overlays to isolate phage and enumerate plaques, and (5) replica-plating to transfer cells from one plate to another in an identical spatial pattern. These procedures can be performed at the laboratory bench, provided they involve non-pathogenic strains of microorganisms (Biosafety Level 1, BSL-1). If working with BSL-2 organisms, then these manipulations must take place in a biosafety cabinet. Consult the most current edition of the Biosafety in Microbiological and Biomedical Laboratories
(BMBL) as well as Material Safety Data Sheets
(MSDS) for Infectious Substances to determine the biohazard classification as well as the safety precautions and containment facilities required for the microorganism in question. Bacterial strains and phage stocks can be obtained from research investigators, companies, and collections maintained by particular organizations such as the American Type Culture Collection
(ATCC). It is recommended that non-pathogenic strains be used when learning the various plating methods. By following the procedures described in this protocol, students should be able to:
● Perform plating procedures without contaminating media.
● Isolate single bacterial colonies by the streak-plating method.
● Use pour-plating and spread-plating methods to determine the concentration of bacteria.
● Perform soft agar overlays when working with phage.
● Transfer bacterial cells from one plate to another using the replica-plating procedure.
● Given an experimental task, select the appropriate plating method.
Basic Protocols, Issue 63, Streak plates, pour plates, soft agar overlays, spread plates, replica plates, bacteria, colonies, phage, plaques, dilutions
Micro-dissection of Rat Brain for RNA or Protein Extraction from Specific Brain Region
Institutions: The University of Hong Kong - HKU.
Micro-dissection of rat brain into various regions is extremely important for the study of different neurodegenerative diseases. This video demonstrates micro-dissection of four major brain regions include olfactory bulb, frontal cortex, striatum and hippocampus in fresh rat brain tissue. Useful tips for quick removal of respective regions to avoid RNA and protein degradation of the tissue are given.
Issue 7, Neuroscience, brain, dissection
Intravitreous Injection for Establishing Ocular Diseases Model
Institutions: The University of Hong Kong - HKU.
Intravitreous injection is a widely used technique in visual sciences research. It can be used to establish animal models with ocular diseases or as direct application of local treatment. This video introduces how to use simple and inexpensive tools to finish the intravitreous injection procedure. Use of a 1 ml syringe, instead of a hemilton syringe, is used. Practical tips for how to make appropriate injection needles using glass pipettes with perfect tips, and how to easily connect the syringe needle with the glass pipette tightly together, are given.
To conduct a good intravitreous injection, there are three aspects to be observed: 1) injection site should not disrupt retina structure; 2) bleeding should be avoided to reduce the risk of infection; 3) lens should be untouched to avoid traumatic cataract. In brief, the most important point is to reduce the interruption of normal ocular structure. To avoid interruption of retina, the superior nasal region of rat eye was chosen. Also, the puncture point of the needle was at the par planar, which was about 1.5 mm from the limbal region of the rat eye. A small amount of vitreous is gently pushed out through the puncture hole to reduce the intraocular pressure before injection. With the 45° injection angle, it is less likely to cause traumatic cataract in the rat eye, thus avoiding related complications and influence from lenticular factors. In this operation, there was no cutting of the conjunctiva and ocular muscle, no bleeding. With quick and minor injury, a successful intravitreous injection can be done in minutes.
The injection set outlined in this particular protocol is specific for intravitreous injection. However, the methods and materials presented here can also be used for other injection procedures in drug delivery to the brain, spinal cord or other organs in small mammals.
Neuroscience, Issue 8, eye, injection, rat
Laser-Induced Chronic Ocular Hypertension Model on SD Rats
Institutions: The University of Hong Kong - HKU.
Glaucoma is one of the major causes of blindness in the world. Elevated intraocular pressure is a major risk factor. Laser photocoagulation induced ocular hypertension is one of the well established animal models. This video demonstrates how to induce ocular hypertension by Argon laser photocoagulation in rat.
Neuroscience, Issue 10, glaucoma, ocular hypertension, rat
Interview: HIV-1 Proviral DNA Excision Using an Evolved Recombinase
Institutions: Heinrich-Pette-Institute for Experimental Virology and Immunology, University of Hamburg.
HIV-1 integrates into the host chromosome of infected cells and persists as a provirus flanked by long terminal repeats. Current treatment strategies primarily target virus enzymes or virus-cell fusion, suppressing the viral life cycle without eradicating the infection. Since the integrated provirus is not targeted by these approaches, new resistant strains of HIV-1 may emerge. Here, we report that the engineered recombinase Tre (see Molecular evolution of the Tre recombinase , Buchholz, F., Max Planck Institute for Cell Biology and Genetics, Dresden) efficiently excises integrated HIV-1 proviral DNA from the genome of infected cells. We produced loxLTR containing viral pseudotypes and infected HeLa cells to examine whether Tre recombinase can excise the provirus from the genome of HIV-1 infected human cells. A virus particle-releasing cell line was cloned and transfected with a plasmid expressing Tre or with a parental control vector. Recombinase activity and virus production were monitored. All assays demonstrated the efficient deletion of the provirus from infected cells without visible cytotoxic effects. These results serve as proof of principle that it is possible to evolve a recombinase to specifically target an HIV-1 LTR and that this recombinase is capable of excising the HIV-1 provirus from the genome of HIV-1-infected human cells.
Before an engineered recombinase could enter the therapeutic arena, however, significant obstacles need to be overcome. Among the most critical issues, that we face, are an efficient and safe delivery to targeted cells and the absence of side effects.
Medicine, Issue 16, HIV, Cell Biology, Recombinase, provirus, HeLa Cells
Retrograde Labeling of Retinal Ganglion Cells by Application of Fluoro-Gold on the Surface of Superior Colliculus
Institutions: The University of Hong Kong - HKU.
Retinal ganglion cell (RGC) counting is essential to evaluate retinal degeneration especially in glaucoma. Reliable RGC labeling is fundamental for evaluating the effects of any treatment. In rat, about 98% of RGCs is known to project to the contralateral superior colliculus (SC) (Forrester and Peters, 1967). Applying fluoro-gold (FG) on the surface of SC can label almost all the RGCs, so that we can focus on this most vulnerable retinal neuron in glaucoma. FG is taken up by the axon terminals of retinal ganglion cells and bilaterally transported retrogradely to its somas in the retina. Compare with retrograde labeling of RGC by putting FG at stump of transected optic nerve for 2 days, the interference of RGC survival is minimized. Compare with cresyl violet staining that stains RGCs, amacrine cells and endothelium of the blood vessel in the retinal ganglion cell layer, this labeling method is more specific to the RGC. This video describes the method of retrograde labeling of RGC by applying FG on the surface of SC. The surgical procedures include drilling the skull; aspirating the cortex to expose the SC and applying gelatin sponge over entire dorsal surface of SC are shown. Useful tips for avoiding massive intracranial bleeding and aspiration of the SC have been given.
Neuroscience, Issue 16, Retrograde labeling, retinal ganglion cells, ophthalmology research, superior colliculus, experimental glaucoma
Protocol for Production of a Genetic Cross of the Rodent Malaria Parasites
Institutions: National Institutes of Health, Xiamen University.
Variation in response to antimalarial drugs and in pathogenicity of malaria parasites is of biologic and medical importance. Linkage mapping has led to successful identification of genes or loci underlying various traits in malaria parasites of rodents1-3
. The malaria parasite Plasmodium yoelii
is one of many malaria species isolated from wild African rodents and has been adapted to grow in laboratories. This species reproduces many of the biologic characteristics of the human malaria parasites; genetic markers such as microsatellite and amplified fragment length polymorphism (AFLP) markers have also been developed for the parasite7-9
. Thus, genetic studies in rodent malaria parasites can be performed to complement research on Plasmodium falciparum
. Here, we demonstrate the techniques for producing a genetic cross in P. yoelii
that were first pioneered by Drs. David Walliker, Richard Carter, and colleagues at the University of Edinburgh10
Genetic crosses in P. yoelii
and other rodent malaria parasites are conducted by infecting mice Mus musculus
with an inoculum containing gametocytes of two genetically distinct clones that differ in phenotypes of interest and by allowing mosquitoes to feed on the infected mice 4 days after infection. The presence of male and female gametocytes in the mouse blood is microscopically confirmed before feeding. Within 48 hrs after feeding, in the midgut of the mosquito, the haploid gametocytes differentiate into male and female gametes, fertilize, and form a diploid zygote (Fig. 1). During development of a zygote into an ookinete, meiosis appears to occur11
. If the zygote is derived through cross-fertilization between gametes of the two genetically distinct parasites, genetic exchanges (chromosomal reassortment and cross-overs between the non-sister chromatids of a pair of homologous chromosomes; Fig. 2) may occur, resulting in recombination of genetic material at homologous loci. Each zygote undergoes two successive nuclear divisions, leading to four haploid nuclei. An ookinete further develops into an oocyst. Once the oocyst matures, thousands of sporozoites (the progeny of the cross) are formed and released into mosquito hemoceal. Sporozoites are harvested from the salivary glands and injected into a new murine host, where pre-erythrocytic and erythrocytic stage development takes place. Erythrocytic forms are cloned and classified with regard to the characters distinguishing the parental lines prior to genetic linkage mapping. Control infections of individual parental clones are performed in the same way as the production of a genetic cross.
Infectious Disease, Issue 47, Genetic cross, genetic mapping, malaria, rodent
A Simple Way to Measure Ethanol Sensitivity in Flies
Institutions: University of Texas Southwestern Medical Center.
Low doses of ethanol cause flies to become hyperactive, while high doses are sedating. The sensitivity to ethanol-induced sedation of a given fly strain is correlated with that strain s ethanol preference, and therefore sedation is a highly relevant measure to study the genetics of alcohol responses and drinking. We demonstrate a simple way to expose flies to ethanol and measure its intoxicating effects. The assay we describe can determine acute sensitivity, as well as ethanol tolerance induced by repeat exposure. It does not require a technically involved setup, and can therefore be applied in any laboratory with basic fly culture tools.
Neuroscience, Issue 48, Drosophila, behavior, alcohol, addiction
Hyponeophagia: A Measure of Anxiety in the Mouse
Institutions: University of Oxford.
Before the present day, when fast-acting and potent rodenticides such as alpha-chloralose were not yet in use, the work of pest controllers was often hampered by a phenomenon known as "bait shyness". Mice and rats cannot vomit, due to the tightness of the cardiac sphincter of the stomach, so to overcome the problem of potential food toxicity they have evolved a strategy of first ingesting only very small amounts of novel substances. The amounts ingested then gradually increase until the animal has determined whether the substance is safe and nutritious. So the old rat-catchers would first put a palatable substance such as oatmeal, which was to be the vehicle for the toxin, in the infested area. Only when large amounts were being readily consumed would they then add the poison, in amounts calculated not to affect the taste of the vehicle. The poisoned bait, which the animals were now readily eating in large amounts, would then swiftly perform its function.
Bait shyness is now used in the behavioural laboratory as a way of measuring anxiety. A highly palatable but novel substance, such as sweet corn, nuts or sweetened condensed milk, is offered to the mice (or rats) in a novel situation, such as a new cage. The latency to consume a defined amount of the new food is then measured.
Robert M.J. Deacon can be reach at email@example.com
Neuroscience, Issue 51, Anxiety, hyponeophagia, bait shyness, mice, hippocampus, strain differences, plus-maze
Induction and Clinical Scoring of Chronic-Relapsing Experimental Autoimmune Encephalomyelitis
Institutions: University of California, Irvine (UCI).
Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) that commonly affects young adults. It is characterized by demyelination and glial scaring in areas disseminated in the brain and spinal cord. These lesions alter nerve conduction and induce the disabling neurological deficits that vary with the location of the demyelinated plaques in the CNS (e.g. paraparesis, paralysis, blindness, incontinence).
Experimental autoimmune encephalomyelitis (EAE) is a model for MS. EAE was first induced accidentally in humans during vaccination against rabies, using viruses grown on rabbit spinal cords. Residues of spinal injected with the inactivated virus induced the CNS disease. Following these observations, a first model of EAE was described in non-human primates immunized with a CNS homogenate by Rivers and Schwenther in 1935. EAE has since been generated in a variety of species and can follow different courses depending on the species/strain and immunizing antigen used. For example, immunizing Lewis rats with myelin basic protein in emulsion with adjuvant induces an acute model of EAE, while the same antigen induces a chronic disease in guinea pigs.
The EAE model described here is induced by immunizing DA rats against DA rat spinal cord in emulsion in complete Freund's adjuvant. Rats develop an ascending flaccid paralysis within 7-14 days post-immunization. Clinical signs follow a relapsing-remitting course over several weeks. Pathology shows large immune infiltrates in the CNS and demyelination plaques. Special considerations for taking care for animals with EAE are described at the end of the video.
Immunology, Issue 5, Autoimmune Disease, Animal Model, EAE, Experimental Allergic Encephalomyelitis, Multiple Sclerosis, Immunology, Clinical Scoring, Disease Model, Inflammation, Central Nervous System