Animal Use Alternatives
Disease Models, Animal
Models, Animal
Mice, Inbred C57BL
Huntington Disease
Neurodegenerative Diseases
New perspectives on biliary atresia. (1/64177)
An investigation into the aetiology, diagnosis, and treatment of biliary atresia was carried out because the prognosis remains so poor.In an electron microscopical study no viral particles or viral inclusion bodies were seen, nor were any specific ultrastructural features observed. An animal experiment suggested that obstruction within the biliary tract of newborn rabbits could be produced by maternal intravenous injection of the bile acid lithocholic acid.A simple and atraumatic method of diagnosis was developed using(99) (m)Tc-labelled compounds which are excreted into bile. Two compounds, (99m)Tc-pyridoxylidene glutamate ((99m)Tc-PG) and (99m)Tc-dihydrothioctic acid ((99m)Tc-DHT) were first assessed in normal piglets and piglets with complete biliary obstruction. Intestinal imaging correlated with biliary tract patency, and the same correlation was found in jaundiced human adults, in whom the (99m)Tc-PG scan correctly determined biliary patency in 21 out of 24 cases. The (99m)Tc-PG scan compared well with liver biopsy and (131)I-Rose Bengal in the diagnosis of 11 infants with prolonged jaundice.A model of extrahepatic biliary atresia was developed in the newborn piglet so that different methods of bile drainage could be assessed. Priorities in biliary atresia lie in a better understanding of the aetiology and early diagnosis rather than in devising new bile drainage procedures. (+info)The evolution of early fibromuscular lesions hemodynamically induced in the dog renal artery. I. Light and transmission electron microscopy. (2/64177)
In view of the important roles of arterial intimal fibromuscular lesions as precursors of atherosclerotic plaque and occlusive lesions in arterial reconstructions, a model has been developed for the rapid hemodynamic induction of these lesions by anastomosis of the dog right renal artery to the inferior vena cava. Light and transmission electron microscopic observations were made on the arterial shunt after periods of rapid flow ranging form 10 minutes to 2 hours to identify initial factor(s) and evolutionary mechanisms in the etiology of the lesions. The sequence of events included aberrations in ruthenium red staining of the endothelial luminal membrane at 10 minutes, multilayered thickening of the subendothelial basement membrane (BM) at 15 minutes, and initial reorientation and migration of smooth muscle cells (SMC) into the intima along with the appearance of areas of degeneration of the internal elastic lamina (IEL) at 30 minutes. The endothelial cells were still intact in some areas overlying the SMC migration and IEL degeneration, but they were separating from the surface in other such areas. As subendothelium became exposed, some platelet adherence was noted. By 2 hours, the entire wall reaction was fully developed. Initial observations indicate that in the evolution of this hemodynamically induced lesion visible alteration in the endothelial cells is not prerequisite to degeneration of the underlying IEL and reorientation and migration of medial SMC. (+info)Site of myocardial infarction. A determinant of the cardiovascular changes induced in the cat by coronary occlusion. (3/64177)
The influence of site of acute myocardial infarction on heart rate, blood pressure, cardiac output, total peripheral resistance (TPR), cardiac rhythm, and mortality was determined in 58 anesthetized cats by occlusion of either the left anterior descending (LAD), left circumflex or right coronary artery. LAD occlusion resulted in immediate decrease in cardiac output, heart rate, and blood pressure, an increase in TPR, and cardiac rhythm changes including premature ventricular beats, ventricular tachycardia, and occasionally ventricular fibrillation. The decrease in cardiac output and increase in TPR persisted in the cats surviving a ventricular arrhythmia. In contrast, right coronary occlusion resulted in a considerably smaller decrease in cardiac output. TPR did not increase, atrioventricular condition disturbances were common, and sinus bradycardia and hypotension persisted in the cats recovering from an arrhythmia. Left circumflex ligation resulted in cardiovascular changes intermediate between those produced by occlusion of the LAD or the right coronary artery. Mortality was similar in each of the three groups. We studied the coronary artery anatomy in 12 cats. In 10, the blood supply to the sinus node was from the right coronary artery and in 2, from the left circumflex coronary artery. The atrioventricular node artery arose from the right in 9 cats, and from the left circumflex in 3. The right coronary artery was dominant in 9 cats and the left in 3. In conclusion, the site of experimental coronary occlusion in cats is a major determinant of the hemodynamic and cardiac rhythm changes occurring after acute myocardial infarction. The cardiovascular responses evoked by ligation are related in part to the anatomical distribution of the occluded artery. (+info)Hierarchy of ventricular pacemakers. (4/64177)
To characterize the pattern of pacemaker dominance in the ventricular specialized conduction system (VSCS), escape ventricular pacemakers were localized and quantified in vivo and in virto, in normal hearts and in hearts 24 hours after myocardial infarction. Excape pacemaker foci were localized in vivo during vagally induced atrial arrest by means of electrograms recorded from the His bundle and proximal bundle branches and standard electrocardiographic limb leads. The VSCS was isolated using a modified Elizari preparation or preparations of each bundle branch. Peacemakers were located by extra- and intracellular recordings. Escape pacemaker foci in vivo were always in the proximal conduction system, usually the left bundle branch. The rate was 43+/-11 (mean+/-SD) beats/min. After beta-adrenergic blockade, the mean rate fell to 31+/-10 beats/min, but there were no shifts in pacemaker location. In the infarcted hearts, pacemakers were located in the peripheral left bundle branch. The mean rate was 146+/-20 beats/min. In isolated normal preparations, the dominant pacemakers usually were in the His bundle, firing at a mean rate of 43+/-10 beats/min. The rates of pacemakers diminished with distal progression. In infarcted hearts, the pacemakers invariably were in the infarct zone. The mean firing rates were not influenced by beta-adrenergic blockade. The results indicate that the dominant pacemakers are normally in the very proximal VSCS, but after myocardial infarction pacemaker dominance is shifted into the infarct. Distribution of pacemaker dominance is independent of sympathetic influence. (+info)A genetic model of substrate deprivation therapy for a glycosphingolipid storage disorder. (5/64177)
Inherited defects in the degradation of glycosphingolipids (GSLs) cause a group of severe diseases known as GSL storage disorders. There are currently no effective treatments for the majority of these disorders. We have explored a new treatment paradigm, substrate deprivation therapy, by constructing a genetic model in mice. Sandhoff's disease mice, which abnormally accumulate GSLs, were bred with mice that were blocked in their synthesis of GSLs. The mice with simultaneous defects in GSL synthesis and degradation no longer accumulated GSLs, had improved neurologic function, and had a much longer life span. However, these mice eventually developed a late-onset neurologic disease because of accumulation of another class of substrate, oligosaccharides. The results support the validity of the substrate deprivation therapy and also highlight some limitations. (+info)DMPK dosage alterations result in atrioventricular conduction abnormalities in a mouse myotonic dystrophy model. (6/64177)
Myotonic dystrophy (DM) is the most common form of muscular dystrophy and is caused by expansion of a CTG trinucleotide repeat on human chromosome 19. Patients with DM develop atrioventricular conduction disturbances, the principal cardiac manifestation of this disease. The etiology of the pathophysiological changes observed in DM has yet to be resolved. Haploinsufficiency of myotonic dystrophy protein kinase (DMPK), DM locus-associated homeodomain protein (DMAHP) and/or titration of RNA-binding proteins by expanded CUG sequences have been hypothesized to underlie the multi-system defects observed in DM. Using an in vivo murine electrophysiology study, we show that cardiac conduction is exquisitely sensitive to DMPK gene dosage. DMPK-/- mice develop cardiac conduction defects which include first-, second-, and third-degree atrioventricular (A-V) block. Our results demonstrate that the A-V node and the His-Purkinje regions of the conduction system are specifically compromised by DMPK loss. Importantly, DMPK+/- mice develop first-degree heart block, a conduction defect strikingly similar to that observed in DM patients. These results demonstrate that DMPK dosage is a critical element modulating cardiac conduction integrity and conclusively link haploinsufficiency of DMPK with cardiac disease in myotonic dystrophy. (+info)Alternative sulfonylurea receptor expression defines metabolic sensitivity of K-ATP channels in dopaminergic midbrain neurons. (7/64177)
ATP-sensitive potassium (K-ATP) channels couple the metabolic state to cellular excitability in various tissues. Several isoforms of the K-ATP channel subunits, the sulfonylurea receptor (SUR) and inwardly rectifying K channel (Kir6.X), have been cloned, but the molecular composition and functional diversity of native neuronal K-ATP channels remain unresolved. We combined functional analysis of K-ATP channels with expression profiling of K-ATP subunits at the level of single substantia nigra (SN) neurons in mouse brain slices using an RT-multiplex PCR protocol. In contrast to GABAergic neurons, single dopaminergic SN neurons displayed alternative co-expression of either SUR1, SUR2B or both SUR isoforms with Kir6.2. Dopaminergic SN neurons expressed alternative K-ATP channel species distinguished by significant differences in sulfonylurea affinity and metabolic sensitivity. In single dopaminergic SN neurons, co-expression of SUR1 + Kir6.2, but not of SUR2B + Kir6.2, correlated with functional K-ATP channels highly sensitive to metabolic inhibition. In contrast to wild-type, surviving dopaminergic SN neurons of homozygous weaver mouse exclusively expressed SUR1 + Kir6.2 during the active period of dopaminergic neurodegeneration. Therefore, alternative expression of K-ATP channel subunits defines the differential response to metabolic stress and constitutes a novel candidate mechanism for the differential vulnerability of dopaminergic neurons in response to respiratory chain dysfunction in Parkinson's disease. (+info)DEF-1, a novel Src SH3 binding protein that promotes adipogenesis in fibroblastic cell lines. (8/64177)
The Src homology 3 (SH3) motif is found in numerous signal transduction proteins involved in cellular growth and differentiation. We have purified and cloned a novel protein, DEF-1 (differentiation-enhancing factor), from bovine brain by using a Src SH3 affinity column. Ectopic expression of DEF-1 in fibroblasts resulted in the differentiation of a significant fraction of the culture into adipocytes. This phenotype appears to be related to the induction of the transcription factor peroxisome proliferator-activated receptor gamma (PPARgamma), since DEF-1 NIH 3T3 cells demonstrated augmented levels of PPARgamma mRNA and, when treated with activating PPARgamma ligands, efficient induction of differentiation. Further evidence for a role for DEF-1 in adipogenesis was provided by heightened expression of DEF-1 mRNA in adipose tissue isolated from obese and diabetes mice compared to that in tissue isolated from wild-type mice. However, DEF-1 mRNA was detected in multiple tissues, suggesting that the signal transduction pathway(s) in which DEF-1 is involved is not limited to adipogenesis. These results suggest that DEF-1 is an important component of a signal transduction process that is involved in the differentiation of fibroblasts and possibly of other types of cells. (+info)"Animal Use Alternatives" refers to the methods and techniques used in scientific research, testing, and education that avoid or reduce the use of animals. The three main categories of alternatives are:
1. Replacement: This involves using non-animal methods to entirely replace the use of animals in a particular procedure or experiment. Examples include the use of computer modeling, cell cultures, and tissue samples instead of live animals.
2. Reduction: This refers to methods that reduce the number of animals used in a given procedure or experiment while still achieving the same scientific objective. Examples include using statistical methods to design experiments that require fewer animals, or sharing data and resources between research groups.
3. Refinement: This involves modifying procedures to minimize suffering and improve animal welfare for those animals that are still used. Examples include using anesthesia and pain relief during surgical procedures, providing appropriate housing and enrichment, and implementing humane endpoints in experiments.
The development and implementation of animal use alternatives is a key goal in the ethical and responsible conduct of scientific research, testing, and education.
Animal disease models are specialized animals, typically rodents such as mice or rats, that have been genetically engineered or exposed to certain conditions to develop symptoms and physiological changes similar to those seen in human diseases. These models are used in medical research to study the pathophysiology of diseases, identify potential therapeutic targets, test drug efficacy and safety, and understand disease mechanisms.
The genetic modifications can include knockout or knock-in mutations, transgenic expression of specific genes, or RNA interference techniques. The animals may also be exposed to environmental factors such as chemicals, radiation, or infectious agents to induce the disease state.
Examples of animal disease models include:
1. Mouse models of cancer: Genetically engineered mice that develop various types of tumors, allowing researchers to study cancer initiation, progression, and metastasis.
2. Alzheimer's disease models: Transgenic mice expressing mutant human genes associated with Alzheimer's disease, which exhibit amyloid plaque formation and cognitive decline.
3. Diabetes models: Obese and diabetic mouse strains like the NOD (non-obese diabetic) or db/db mice, used to study the development of type 1 and type 2 diabetes, respectively.
4. Cardiovascular disease models: Atherosclerosis-prone mice, such as ApoE-deficient or LDLR-deficient mice, that develop plaque buildup in their arteries when fed a high-fat diet.
5. Inflammatory bowel disease models: Mice with genetic mutations affecting intestinal barrier function and immune response, such as IL-10 knockout or SAMP1/YitFc mice, which develop colitis.
Animal disease models are essential tools in preclinical research, but it is important to recognize their limitations. Differences between species can affect the translatability of results from animal studies to human patients. Therefore, researchers must carefully consider the choice of model and interpret findings cautiously when applying them to human diseases.
An animal model in medicine refers to the use of non-human animals in experiments to understand, predict, and test responses and effects of various biological and chemical interactions that may also occur in humans. These models are used when studying complex systems or processes that cannot be easily replicated or studied in human subjects, such as genetic manipulation or exposure to harmful substances. The choice of animal model depends on the specific research question being asked and the similarities between the animal's and human's biological and physiological responses. Examples of commonly used animal models include mice, rats, rabbits, guinea pigs, and non-human primates.
C57BL/6 (C57 Black 6) is an inbred strain of laboratory mouse that is widely used in biomedical research. The term "inbred" refers to a strain of animals where matings have been carried out between siblings or other closely related individuals for many generations, resulting in a population that is highly homozygous at most genetic loci.
The C57BL/6 strain was established in 1920 by crossing a female mouse from the dilute brown (DBA) strain with a male mouse from the black strain. The resulting offspring were then interbred for many generations to create the inbred C57BL/6 strain.
C57BL/6 mice are known for their robust health, longevity, and ease of handling, making them a popular choice for researchers. They have been used in a wide range of biomedical research areas, including studies of cancer, immunology, neuroscience, cardiovascular disease, and metabolism.
One of the most notable features of the C57BL/6 strain is its sensitivity to certain genetic modifications, such as the introduction of mutations that lead to obesity or impaired glucose tolerance. This has made it a valuable tool for studying the genetic basis of complex diseases and traits.
Overall, the C57BL/6 inbred mouse strain is an important model organism in biomedical research, providing a valuable resource for understanding the genetic and molecular mechanisms underlying human health and disease.
Huntington Disease (HD) is a genetic neurodegenerative disorder that affects both cognitive and motor functions. It is characterized by the progressive loss of neurons in various areas of the brain, particularly in the striatum and cortex. The disease is caused by an autosomal dominant mutation in the HTT gene, which codes for the huntingtin protein. The most common mutation is a CAG repeat expansion in this gene, leading to the production of an abnormal form of the huntingtin protein that is toxic to nerve cells.
The symptoms of HD typically appear between the ages of 30 and 50, but they can start earlier or later in life. The early signs of HD may include subtle changes in mood, cognition, and coordination. As the disease progresses, individuals with HD experience uncontrolled movements (chorea), emotional disturbances, cognitive decline, and difficulties with communication and swallowing. Eventually, they become dependent on others for their daily needs and lose their ability to walk, talk, and care for themselves.
There is currently no cure for HD, but medications and therapies can help manage the symptoms of the disease and improve quality of life. Genetic testing is available to confirm the diagnosis and provide information about the risk of passing the disease on to future generations.
Neurodegenerative diseases are a group of disorders characterized by progressive and persistent loss of neuronal structure and function, often leading to cognitive decline, functional impairment, and ultimately death. These conditions are associated with the accumulation of abnormal protein aggregates, mitochondrial dysfunction, oxidative stress, chronic inflammation, and genetic mutations in the brain. Examples of neurodegenerative diseases include Alzheimer's disease, Parkinson's disease, Huntington's disease, Amyotrophic Lateral Sclerosis (ALS), and Spinal Muscular Atrophy (SMA). The underlying causes and mechanisms of these diseases are not fully understood, and there is currently no cure for most neurodegenerative disorders. Treatment typically focuses on managing symptoms and slowing disease progression.
Transgenic mice are genetically modified rodents that have incorporated foreign DNA (exogenous DNA) into their own genome. This is typically done through the use of recombinant DNA technology, where a specific gene or genetic sequence of interest is isolated and then introduced into the mouse embryo. The resulting transgenic mice can then express the protein encoded by the foreign gene, allowing researchers to study its function in a living organism.
The process of creating transgenic mice usually involves microinjecting the exogenous DNA into the pronucleus of a fertilized egg, which is then implanted into a surrogate mother. The offspring that result from this procedure are screened for the presence of the foreign DNA, and those that carry the desired genetic modification are used to establish a transgenic mouse line.
Transgenic mice have been widely used in biomedical research to model human diseases, study gene function, and test new therapies. They provide a valuable tool for understanding complex biological processes and developing new treatments for a variety of medical conditions.