Development of CRISPR Cas9, spin-off technologies and their application in model construction and potential therapeutic methods of Parkinson's disease.

Parkinson's disease (PD) is one of the most common degenerative diseases. It is most typically characterized by neuronal death following the accumulation of Lewis inclusions in dopaminergic neurons in the substantia nigra region, with clinical symptoms such as motor retardation, autonomic dysfunction, and dystonia spasms. The exact molecular mechanism of its pathogenesis has not been revealed up to now. And there is a lack of effective treatments for PD, which places a burden on patients, families, and society. CRISPR Cas9 is a powerful technology to modify target genomic sequence with rapid development. More and more scientists utilized this technique to perform research associated neurodegenerative disease including PD. However, the complexity involved makes it urgent to organize and summarize the existing findings to facilitate a clearer understanding. In this review, we described the development of CRISPR Cas9 technology and the latest spin-off gene editing systems. Then we focused on the application of CRISPR Cas9 technology in PD research, summarizing the construction of the novel PD-related medical models including cellular models, small animal models, large mammal models. We also discussed new directions and target molecules related to the use of CRISPR Cas9 for PD treatment from the above models. Finally, we proposed the view about the directions for the development and optimization of the CRISPR Cas9 technology system, and its application to PD and gene therapy in the future. All these results provided a valuable reference and enhanced in understanding for studying PD.

A novel nuclear receptor subfamily enlightens the origin of heterodimerization.

BACKGROUND: Nuclear receptors are transcription factors of central importance in human biology and associated diseases. Much of the knowledge related to their major functions, such as ligand and DNA binding or dimerization, derives from functional studies undertaken in classical model animals. It has become evident, however, that a deeper understanding of these molecular functions requires uncovering how these characteristics originated and diversified during evolution, by looking at more species. In particular, the comprehension of how dimerization evolved from ancestral homodimers to a more sophisticated state of heterodimers has been missing, due to a too narrow phylogenetic sampling. Here, we experimentally and phylogenetically define the evolutionary trajectory of nuclear receptor dimerization by analyzing a novel NR7 subgroup, present in various metazoan groups, including cnidarians, annelids, mollusks, sea urchins, and amphioxus, but lost in vertebrates, arthropods, and nematodes. RESULTS: We focused on NR7 of the cephalochordate amphioxus B. lanceolatum. We present a complementary set of functional, structural, and evolutionary analyses that establish that NR7 lies at a pivotal point in the evolutionary trajectory from homodimerizing to heterodimerizing nuclear receptors. The crystal structure of the NR7 ligand-binding domain suggests that the isolated domain is not capable of dimerizing with the ubiquitous dimerization partner RXR. In contrast, the full-length NR7 dimerizes with RXR in a DNA-dependent manner and acts as a constitutively active receptor. The phylogenetic and sequence analyses position NR7 at a pivotal point, just between the basal class I nuclear receptors that form monomers or homodimers on DNA and the derived class II nuclear receptors that exhibit the classical DNA-independent RXR heterodimers. CONCLUSIONS: Our data suggest that NR7 represents the "missing link" in the transition between class I and class II nuclear receptors and that the DNA independency of heterodimer formation is a feature that was acquired during evolution. Our studies define a novel paradigm of nuclear receptor dimerization that evolved from DNA-dependent to DNA-independent requirements. This new concept emphasizes the importance of DNA in the dimerization of nuclear receptors, such as the glucocorticoid receptor and other members of this pharmacologically important oxosteroid receptor subfamily. Our studies further underline the importance of studying emerging model organisms for supporting cutting-edge research.

CRISPR/Cas9 system: a reliable and facile genome editing tool in modern biology.

Genome engineering has always been a versatile technique in biological research and medicine, with several applications. In the last several years, the discovery of Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-Cas9 technology has swept the scientific community and revolutionised the speed of modern biology, heralding a new era of disease detection and rapid biotechnology discoveries. It enables successful gene editing by producing targeted double-strand breaks in virtually any organism or cell type. So, this review presents a comprehensive knowledge about the mechanism and structure of Cas9-mediated RNA-guided DNA targeting and cleavage. In addition, genome editing via CRISPR-Cas9 technology in various animals which are being used as models in scientific research including Non-Human Primates Pigs, Dogs, Zebra, fish and Drosophila has been discussed in this review. This review also aims to understand the applications, serious concerns and future perspective of CRISPR/Cas9-mediated genome editing.

Paradigm shifts in animal epigenetics: Research on non-model species leads to new insights into dependencies, functions and inheritance of DNA methylation.

Recent investigations with non-model species and whole-genome approaches have challenged several paradigms in animal epigenetics. They revealed that epigenetic variation in populations is not the mere consequence of genetic variation, but is a semi-independent or independent source of phenotypic variation, depending on mode of reproduction. DNA methylation is not positively correlated with genome size and phylogenetic position as earlier believed, but has evolved differently between and within higher taxa. Epigenetic marks are usually not completely erased in the zygote and germ cells as generalized from mouse, but often persist and can be transgenerationally inherited, making them evolutionarily relevant. Gene body methylation and promoter methylation are similar in vertebrates and invertebrates with well methylated genomes but transposon silencing through methylation is variable. The new data also suggest that animals use epigenetic mechanisms to cope with rapid environmental changes and to adapt to new environments. The main benefiters are asexual populations, invaders, sessile taxa and long-lived species.

Central Asian Rodents as Model Animals for Leishmania major and Leishmania donovani Research.

The clinical manifestation of leishmaniases depends on parasite species, host genetic background, and immune response. Manifestations of human leishmaniases are highly variable, ranging from self-healing skin lesions to fatal visceral disease. The scope of standard model hosts is insufficient to mimic well the wide disease spectrum, which compels the introduction of new model animals for leishmaniasis research. In this article, we study the susceptibility of three Asian rodent species (Cricetulus griseus, Lagurus lagurus, and Phodopus sungorus) to Leishmania major and L. donovani. The external manifestation of the disease, distribution, as well as load of parasites and infectiousness to natural sand fly vectors, were compared with standard models, BALB/c mice and Mesocricetus auratus. No significant differences were found in disease outcomes in animals inoculated with sand fly- or culture-derived parasites. All Asian rodent species were highly susceptible to L. major. Phodopus sungorus showed the non-healing phenotype with the progressive growth of ulcerative lesions and massive parasite loads. Lagurus lagurus and C. griseus represented the healing phenotype, the latter with high infectiousness to vectors, mimicking best the character of natural reservoir hosts. Both, L. lagurus and C. griseus were also highly susceptible to L. donovani, having wider parasite distribution and higher parasite loads and infectiousness than standard model animals.

From Mice to Monkeys? Beyond Orthodox Approaches to the Ethics of Animal Model Choice.

Recent developments in genome editing tools, along with limits in the translational potential of rodent models of human disease, have spurred renewed biomedical research interest in large mammals like nonhuman primates, pigs, and dogs. Such scientific developments raise ethical issues about the use of these animals in comparison with smaller mammals, such as mice and rats. To examine these ethical questions, we first consider standard (or "orthodox") approaches, including ethics oversight within biomedical research communities, and critical theoretical reflections on animal research, including rights-based and utilitarian approaches. We argue that oversight of biomedical research offers guidance on the profession's permitted uses of animals within a research setting and orthodox approaches to animal ethics questions when and whether animals should be used in biomedicine; however, neither approach sufficiently investigates the nuances of ethical practices within the research setting. To fill this lacuna, we consider a virtue ethical approach to the use of specific animal models in biomedicine. From this perspective, we argued that limitations on flourishing for large mammals in a research setting, as well as potential human-animal bonds, are two sources of likely ethical tensions in animal care and use in the context of larger mammals.

Animal models of human atherosclerosis: current progress

Atherosclerosis retains the leading position among the causes of global morbidity and mortality worldwide, especially in the industrialized countries. Despite the continuing efforts to investigate disease pathogenesis and find the potential points of effective therapeutic intervention, our understanding of atherosclerosis mechanisms remains limited. This is partly due to the multifactorial nature of the disease pathogenesis, when several factors so different as altered lipid metabolism, increased oxidative stress, and chronic inflammation act together leading to the formation and progression of atherosclerotic plaques. Adequate animal models are currently indispensable for studying these processes and searching for novel therapies. Animal models based on rodents, such as mice and rats, and rabbits represent important tools for studying atherosclerosis. Currently, genetically modified animals allow for previously unknown possibilities in modelling the disease and its most relevant aspects. In this review, we describe the recent progress made in creating such models and discuss the most important findings obtained with them to date.

Social creatures: Model animal systems for studying the neuroendocrine mechanisms of social behaviour.

The interaction of animals with conspecifics, termed social behaviour, has a major impact on the survival of many vertebrate species. Neuropeptide hormones modulate the underlying physiology that governs social interactions, and many findings concerning the neuroendocrine mechanisms of social behaviours have been extrapolated from animal models to humans. Neurones expressing neuropeptides show similar distribution patterns within the hypothalamic nucleus, even when evolutionarily distant species are compared. During evolution, hypothalamic neuropeptides and releasing hormones have retained not only their structures, but also their biological functions, including their effects on behaviour. Here, we review the current understanding of the mechanisms of social behaviours in several classes of animals, such as worms, insects and fish, as well as laboratory, wild and domesticated mammals.

Commercial Rodents in America: Standard Animals, Model Animals, and Biological Diversity.

Rodents as standardized test animals were developed for commercial distribution in the USA between 1910 and the 1930s. The selective breeding of rats (Rattus norvegicus) and pure-bred mice (Mus musculus) at the Wistar Institute and the Jackson Memorial Laboratories eventually led to a decline in the diversity of species used in American medical and life sciences. The early driving figures, science administrator Milton Greenman and the scientists Henry Donaldson and Clarence Little, sought to standardize animals to render science and its application to humanity more precise. But their efforts were exaggerated in the USA through an expanding industrial and engineering ideal, culminating in a preference for Big Science. I explore the nineteenth century origins of this ideal in Emil Du Bois-Reymond's neurophysiology. This foundation later merged with increasing standardization, American commercialism, and the success of Big Science to transform animal laboratory "standards" into "model animals." Recent accounts of research with commercially bred mice reveal how findings can be co-constructed using human clinical data, as animal research is applied to humans. The neglect of evolutionary perspectives and the dominance of "models" may even have begun with the government's post-war emphasis on funding greater species access for large-scale biomedical research.

The Sox2 promoter-driven CD63-GFP transgenic rat model allows tracking of neural stem cell-derived extracellular vesicles.

Extracellular vesicles (EVs) can modulate microenvironments by transferring biomolecules, including RNAs and proteins derived from releasing cells, to target cells. To understand the molecular mechanisms maintaining the neural stem cell (NSC) niche through EVs, a new transgenic (Tg) rat strain that can release human CD63-GFP-expressing EVs from the NSCs was established. Human CD63-GFP expression was controlled under the rat Sox2 promoter (Sox2/human CD63-GFP), and it was expressed in undifferentiated fetal brains. GFP signals were specifically observed in in vitro cultured NSCs obtained from embryonic brains of the Tg rats. We also demonstrated that embryonic NSC (eNSC)-derived EVs were labelled by human CD63-GFP. Furthermore, when we examined the transfer of EVs, eNSC-derived EVs were found to be incorporated into astrocytes and eNSCs, thus implying an EV-mediated communication between different cell types around NSCs. This new Sox2/human CD63-GFP Tg rat strain should provide resources to analyse the cell-to-cell communication via EVs in NSC microenvironments.

Establishment of rat model of orthotopic bladder cancer induced by MNU and diagnosis value of MRI / 吉林大学学报(医学版)

Objective:To construct the rat models of orthotopic bladder cancer induced by N-methyl-nitrosourea (MNU),and to evaluate the value of magnetic resonance imaging (MRI)in the noninvasive diagnosis of the bladder cancer model.Methods:Sixty femail SD rats were divided into experiment group (n=45)and control group (n=15).The rats experiment group were induced with MNU (2 mg per rat)by intravesical administration every other week,for 4 times.Meantime,the rats in control group were treated with normal saline (0.2 mL per rat)by intravesical administration.At the end of the 14th week,all rats were examined by MRI and the pathological changes of bladder tissue were detected.Results:In experiment group,43 rats were alived and 2 rats were died at the end of the 14th week;the survial rate was 95.6% and the death rate was 4.4%;the abnormal signals were found in each of 43 rats by MRI which manifested as bladder tumor, and the same results were identified by pathology;the tumor formation rate was 100%.In control group,14 rats were alived and 1 rat was died at the end of the 14th week;the survival rate was 93.3%,and the death rate was 6.7%;there was no abnormal signal in the MRI examination and no bladder cancer in the pathological examination;the tumor formation rate was 0.The tumor formation rates of bladder cancer of the rats in two groups had significant difference (P 0.05).Conclusion:The method to establish the rat models of orthotopic bladder cancer induced by MNU is simple and reliable;the results of MRI are consistent with the pathological results and MRI examination is a reliable diagnostic method concerning this model.

Establishment of Congenital Heart Disease Transposition of Great Arteries in Experimental Mice Model / 中国循环杂志

Objective: To establish a mice model of congenital heart disease transposition of great arteries in order to provide a research reference for the occurrence and development of transposition of great arteries. Methods: A total of 20 pregnant ICR mice at 8-10 weeks of age were divided into 2 groups: Control group, the mice received a single dose of DMSO 70 mg/kg at 8.5 days of gestation,n=5 and Experiment group, the mice received a single dose of all-trans retinoic acid 70 mg/kg at 8.5 days of gestation,n=15. All animals were treated for 18 days and then the embryos were taken to observe cardiac morphology under stereomicroscope. Results: Compared with Control group, Experiment group had obviously increased occurrence rates of premature delivery, abortion and embryo absorption, and 61.2% phenotype for transposition of great arteries; meanwhile, combining with non-heart defect phenotypeas exophthalmos and spinal malformation. Conclusion: All-trans retinoic acid may induce transposition of great arteries in mice embryos, which is a feasible animal model in experimental research.

Homozygous loss of mouse tetraspanin CD82 enhances integrin αIIbß3 expression and clot retraction in platelets.

Integrin αIIbß3 is critical for platelet-mediated blood clotting. Tetraspanins are well-established regulators of integrins and genetic loss of tetraspanin CD151 or TSSC6 in mice leads to increased bleeding due to inadequate integrin αIIbß3 outside-in signaling. Conversely, mild but enhanced integrin αIIbß3 activation and hyperaggregation is observed in CD9 and CD63 null mice respectively. CD82 is reportedly expressed in platelets; however its function is unknown. Using genetically engineered CD82 null mice, we investigated the role of the tetraspanin CD82 in platelet activation. Loss of CD82 resulted in reduced bleed times in vivo. CD82 was present on the surface of both human and mouse platelets, and its levels did not change upon platelet activation or degranulation. No differences in platelet activation, degranulation, or aggregation in response to ADP or collagen were detected in CD82 null mice. However, the kinetics of clot retraction was enhanced, which was intrinsic to the CD82-null platelets. Integrin αIIbß3 surface expression was elevated on the platelets from CD82 null mice and they displayed enhanced adhesion and tyrosine kinase signaling on fibrinogen. This is the first report on CD82 function in platelets; which we found intrinsically modulates clot retraction, integrin αIIbß3 expression, cell adhesion, and tyrosine signaling.

Rodent models for human diseases.

One of the factors limiting the translation of knowledge from preclinical studies to the clinic has been the limitations of in vivo diseases models. Except in the case of highly controlled and regulated clinical trials, geneticists and scientists do not use humans for their experimental investigations because of the obvious risk to life. Instead, they use various animal, fungal, bacterial, and plant species as model organisms for their studies. Amongst these model organisms, rodent models are the most used due to the easiness for the experiments and the possibility to modify genetically these model animals. Nevertheless, due to the fact that animal models typically do not contract the same genetic diseases as people, so scientists must alter their genomes to induce human disease states and to know what kind of mutation causes the disease. In this brief review, we will discuss the interests of rodent models that have been developed to simulate human pathologies, focusing in models that employ xenografts and genetic modification. Within the framework of genetically engineered mouse (GEM) models, we will review some of the current genetic strategies for modeling diseases.

Comparative analysis of virulence of a novel, avian-origin H3N2 canine influenza virus in various host species.

A novel avian-origin H3N2 canine influenza A virus (CIV) that showed high sequence similarities in hemagglutinin and neuraminidase genes with those of non-pathogenic avian influenza viruses was isolated in our routine surveillance program in South Korea. We previously reported that the pathogenicity of this strain could be reproduced in dogs and cats. In the present study, the host tropism of H3N2 CIV was examined by experimental inoculation into several host species, including chickens, pigs, mice, guinea pigs, and ferrets. The CIV infection resulted in no overt symptoms of disease in these host species. However, sero-conversion, virus shedding, and gross and histopathologic lung lesions were observed in guinea pig and ferrets but not in pigs, or mice. Based on the genetic similarity of our H3N2 CIV with currently circulating avian influenza viruses and the presence of α-2,3-linked rather than α-2,6-linked sialic acid receptors in the respiratory tract of dogs, we believed that this strain of CIV would have avian virus-like receptor specificity, but that seems to be contrary to our findings in the present study. Further studies are needed to determine the co-receptors of hemagglutinin or post-attachment factors related to virus internalization or pathogenesis in other animals.

Effect of Jianxi Qianggu Pill on the pathological changes of articular cartilage in knee osteoarthritis rabbits / 中国组织工程研究

BACKGROUND:Knee osteoarthritis is characterized by inreversible pathological changes, belonging to arthragia syndrome. The goal of the treatment is to release or relieve symptoms and delay joint degeneration. Jianxi Qianggu Pil is an empirical formula developed by the Third People’s Hospital of Jingzhou, School of Basic Medical Science, Wuhan University, China. This prescription can nourish liver and kidney, eliminate wind and disperse cold, expel wet and dredge the col aterals, consolidate bone and reinforce knee. OBJECTIVE:To observe the protective effect of Jianxi Qianggu Pil on joint cartilage and expression of bone morphogenetic protein 7 in rabbits with knee osteoarthritis. METHODS:A total of 36 New Zealand rabbits were randomly divided into three groups, with 12 ones in each. The involved rabbits were applied to establish the model of knee osteoarthritis by using the modified Hulth’s method. At 6 weeks after modeling, the drug group was given 0.1 g/kg Jianxi Qianggu Pil via intragastric administration, while model group and normal control group received equal volume of saline. At 4 weeks after drug administration, rabbit articular cartilage was evaluated with Mankin’s scoring method. The cartilage morphology was observed under electron microscopy, and bone morphogenetic protein 7 expression was detected using immunohistochemistry. RESULTS AND CONCLUSION:The pathological degeneration degree of articular cartilage in the drug group was significantly lighter, and bone morphogenetic protein 7 expression was significantly higher than the other two groups (P<0.05). Experimental findings indicate that, Jianxi Qianggu Pil can promote the expression of bone morphogenetic protein 7 in articular cartilage of knee osteoarthritis rabbits, thereby promoting articular cartilage regeneration and reducing cartilage deformation or necrosis for the treatment of arthritis.

Insulin-like growth factor 1 promotes in vitro proliferation of chondrocytes in traumatic arthritis / 中国组织工程研究

BACKGROUND:The early damaged chondrocytes are susceptible to de-differentiate and exert unstable phenotype during the in vitro culture, thus needing some growth factors. OBJECTIVE:To observe the promotion effect of insulin-like growth factor 1 on the in vitro proliferation of chondrocytes in adult rabbits with traumatic arthritis. METHODS:Traumatic arthritis models of adult rabbits were established by using the modified Hulth method. After the models were successful y established, the distal femur and proximal tibia were harvested under sterile conditions, the chondrocytes were cultured. The cultured cells were divided into two groups:control group was cultured with Dulbecco’s modified Eagle’s medium containing 10%fetal bovine serum, while experimental group was cultured with Dulbecco's modified Eagle’s medium containing 100μg/L insulin-like growth factor 1. The effect of insulin-like growth factor 1 on the proliferation of chondrocytes in adult rabbits with traumatic arthritis was determined through the cytomorphology, cellcounting, and cellactivity. RESULTS AND CONCLUSION:The chondrocytes in adult rabbits with traumatic arthritis were successful y cultured, the majority of cells were mini-cells, presenting smal fusiform, round or polygonal shape. Hematoxylin-eosin staining showed that the number of cells in experimental group was higher than that in control group. MTT assay found that the absorbance of cells in experimental group was greater than that in control group (P<0.01). Our findings indicate that, insulin-like growth factor 1 can promote the in vitro proliferation of chondrocytes in adult rabbits with traumatic arthritis.

Role of stem cells, endothelial cells and cytokines in the development and regression of infantile hemangioma / 中国组织工程研究

BACKGROUND:At present, there are few efficient therapies for infantile hemangioma, and the pathogenesis mechanisms remain unclear. OBJECTIVE:To review the literatures available on the epidemiology, pathophysiology and pathogenesis of infantile hemangioma, to understand the research progress on the pathogenesis of infantile hemangioma, and to provide a reference for developing new drug therapies. METHODS:A computer-based online search was performed in the PubMed database for literatures related to the pathogenesis, physiopathological features and epidemiology data of infantile hemangioma published from January 2009 to February 2014. The subject headings are“hemangioma, capil ary, classification, epidemiology, etiology, embryology, cytology, physiopathology, pathology, immunology, genetics, drug therapy, therapy”. RESULTS AND CONCLUSION:Accumulating evidence has investigated the occurrence, development and regression of infantile hemangioma. However, no large-scale, multi-central epidemiology data are reported, and there is no theory explaining the pathogenesis of infantile hemangioma completely. Moreover, the relationship between al those theories about the pathogenesis remains unclear. The most important obstacle constraining the research is the lack of ideal animal model of infantile hemangioma. Due to the restrictions of nude mice models, it is imminent to develop new animal models for infantile hemangioma research.

Impaired fracture healing and change of advanced glycation end products in vivo in type 2 diabetes rats / 中国组织工程研究

BACKGROUND:Increasing attention has been paid on the role of advanced glycation end products in bone tissue. Glucose metabolic disorder is one of the main reasons for the increase of advanced glycation end products. OBJECTIVE:To observe the change of advanced glycation end products expressed in type 2 diabetes rats, and to investigate the relationship between impaired fracture healing and change of advanced glycation end products expression in vivo. METHODS:Thirty Sprague-Dawley rats were randomly and equal y divided into two groups:control group (normal feeding) and experimental group (high fat and sucrosum diet feeding to establish type 2 diabetes model). After diabetes models were established, the model of distraction osteogenesis in the left tibiae of al the rats was produced. Distraction was given 0.3 mm per day and continued for 14 days. RESULTS AND CONCLUSION:After the traction was complete, cal us formation in distraction gap was obviously reduced in experimental group compared with control group by X-ray examination. The array of microcolumn formation was disordered and the area of primary matrix front was catachromasis by histology examination. The enzyme-linked immunosorbent assay results showed that, the level of advanced glycation end products was obviously elevated (P<0.01) while osteocalcin was obviously reduced (P<0.01) in experimental group in comparison with control group. The formation of distraction cal us was impaired in the process of fracture healing and blood of type 2 diabetes rats. The increase of advanced glycation end products may be one of the reasons that cause impaired fracture healing in diabetic rats.

Histochemical and morphological characteristics of the levator ani muscle in rats / Características morfológicas e histoquímicas del músculo elevador del ano en ratas

The current study aimed to analyze the histochemical and morphological characteristics of the levator ani muscle in rats. For this, we used 10 Wistar rats (5 males and 5 females), weighing between 200 and 765g. The animals were dissected fresh and in formalin for the levator ani muscle anatomical observation. Muscle fragments were collected and frozen in n-Hexane previously cooled in liquid nitrogen. Then, the muscles were transferred to a microtome cryostat (HM 505 E Microm), being fixed in metal mounts with the adhesive Tissue Freezing Medium. Histological sections of 6.0um were removed and subjected to HE staining. Other sections were subjected to NADH-TR and SDH reactions. After being dissected and fixed, the architecture of the female pelvic floor revealed the presence of two muscles: iliocaudalis and pubocaudalis. The anatomical inspection in male rats revealed, pronouncedly, the presence of the levator ani muscle: ischiocavernosus and bulbocavernous. We therefore observed a marked anatomical difference between animals of the same species, which does not occur with humans. The HE staining revealed muscular fibers with preserved morphology, contours ranging from polygonal to rounded, acidophilic cytoplasm, one or more peripheral nuclei with rounded shape and dense chromatin aspect. The fibers were organized in fascicles arranged by a dense connective tissue, the perimysium, and each fiber surrounded by the endomysium, composed of loose connective tissue. The sections subjected to NADH-TH and SDH, whose reactions show the activity of oxidative or glycolytic muscle fibers, allowed the identification of the two types of fiber. The fast-twitch fiber shows weaker reactivity, whereas the slow-twitch fiber has small diameter and intense reactivity, especially in the subsarcolemmal, presenting a highly oxidative metabolism. It was found that the pelvic floor muscles in rats are composed primarily by fast-twitch fibers, while in humans they are...

El estudio tuvo como objetivo analizar las características histoquímicas y morfológicas del músculo elevador del ano en ratas. Para esto, se utilizaron 10 ratas Wistar (5 machos y 5 hembras), con un peso entre 200 y 765g. Los animales fueron disecados frescos y en formol para la observación anatómica del músculo elevador del ano. Fragmentos de músculo fueron recogidos y congelados en n-Hexano, previamente enfriado en nitrógeno líquido. Luego, los músculos fueron trasladados a un micrótomo criostato (Microm HM 505 E), fijados en soportes metálicos con adhesivo Tissue Freezing Medium. Cortes histológicos de 6,0 um fueron retirados y sometidos a tinción de H-E. Otras secciones fueron sometidas a las reacciones de NADH-TR y SDH. Después de haber sido disecado y fijado, la arquitectura del suelo de la pelvis de las ratas hembra, reveló la presencia de dos músculos: m. iliocaudalis y m. pubocaudalis. La inspección anatómica de las ratas macho mostró, marcadamente, la presencia del músculo elevador del ano: isquiocavernoso y bulbocavernoso. Por lo tanto, observamos una marcada diferencia anatómica entre los animales de la misma especie, lo que no ocurre con los seres humanos. La tinción HE reveló fibras musculares con morfología conservada, contornos que van desde el esquema poligonal al redondeado, citoplasma acidófilo, uno o más núcleos periféricos con forma redondeada y un aspecto denso de la cromatina. Las fibras se organizaban en fascículos compuestos por un tejido conectivo denso, perimisio, y cada fibra rodeada por el endomisio compuesto por tejido conectivo laxo. En las secciones sometidas a NADH-TH y SDH, cuyas reacciones muestran la actividad oxidativa o glicolítica de las fibras musculares, permitió la identificación de los dos tipos de fibras. Las fibras de contracción rápida muestran más débil reactividad y, las de contracción lenta tienen un diámetro pequeño y reactividad intensa, especialmente en las regiones subsarcolemales, presentando un...