Course Of Proliferation Research Articles

The Evaluation, Diagnosis, and Management of Infantile Hemangiomas-A Comprehensive Review.

Infantile hemangioma (IH) is the most common pediatric benign vascular tumor. Its pathogenesis is still poorly understood, and it usually appears during the first few weeks of life and follows a characteristic natural course of proliferation and involution. Most IHs are small, benign, resolve spontaneously, and do not require active treatment but only active observation. A minority of IHs are potentially problematic because they can cause life-threatening complications, permanent disfigurement, and functional impairment. Diagnosis is usually clinical, and propranolol is currently the mainstay of treatment. Other therapeutic modalities may be used alone or in combination, depending on the characteristics of the specific IH. New treatment options are being explored every day, and some are showing promising results. It is undeniable that therapeutic modalities for IHs must be selected based on the child's age, the size and location of the lesion, the presence of complications, the implementation conditions, and the possible outcomes of the treatment. The future of IH management will certainly be reflected in improved advanced imaging modalities, research into the genetic and molecular basis, the development of new pharmacological agents or techniques, and the development of standardized protocols, all to optimize outcomes with minimal side effects.

Vascular Endothelial Growth Factor A and Leptin Expression Associated with Ectopic Proliferation and Retinal Dysplasia in Zebrafish Optic Pathway Tumors

In the central nervous system injury induces cellular reprogramming and progenitor proliferation, but the molecular mechanisms that limit regeneration and prevent tumorigenesis are not completely understood. We previously described a zebrafish optic pathway tumor model in which transgenic Tg(flk1:RFP)is18/+ adults develop nonmalignant retinal tumors. Key pathways driving injury-induced glial reprogramming and regeneration contributed to tumor formation. In this study, we examine a time course of proliferation and present new analyses of the Tg(flk1:RFP)is18/+ dysplastic retina and tumor transcriptomes. Retinal dysplasia was first detected in 3-month-old adults, but was not limited to a specific stem cell or progenitor niche. Pathway analyses suggested a decrease in cellular respiration and increased expression of components of Hif1-α, VEGF, mTOR, NFκβ, and multiple interleukin pathways are associated with early retinal dysplasia. Hif-α targets VEGFA (vegfab) and Leptin (lepb) were both highly upregulated in dysplastic retina; however, each showed distinct expression patterns in neurons and glia, respectively. Phospho-S6 immunolabeling indicated that mTOR signaling is activated in multiple cell populations in wild-type retina and in the dysplastic retina and advanced tumor. Our results suggest that multiple pathways may contribute to the continuous proliferation of retinal progenitors and tumor growth in this optic pathway tumor model. Further investigation of these signaling pathways may yield insight into potential mechanisms to control the proliferative response during regeneration in the nervous system.

Sorafenib treatment during partial hepatectomy reduces tumorgenesis in an inflammation-associated liver cancer model.

The long-term prognosis after resection of hepatocellular carcinoma (HCC), which is one of the treatment options for early-stage HCC, remains unsatisfactory as a result of a high incidence of disease recurrence. Recent studies performed in murine models revealed a link between liver regeneration under chronic inflammation and hepatic tumorigenesis. Sorafenib is a potent drug for advanced HCC with multikinase inhibition activity. We propose that inhibition of signal transduction pathways which are activated during hepatectomy, using Sorafenib, will reduce accelerated tumorigenesis. To test this hypothesis, we studied the Mdr2-knockout (KO) mouse strain, a model of inflammation-associated cancer, which underwent partial hepatectomy (PHx) at three months of age, with or without Sorafenib.Here we show that Sorafenib treatment during PHx inhibited different signal transduction pathways at the multikinase levels, but did not result in increased morbidity or mortality. At the early stages after PHx, Sorafenib treatment had no effect on the course of proliferation, apoptosis and DNA repair in the regenerating liver, but resulted in decreased stellate cells activation and inflammatory response. Finally, we show that Sorafenib treatment during PHx at three months of age resulted in decreased fibrosis and tumor formation at 8.5 months.In conclusion our study indicates that short-term Sorafenib treatment during PHx is safe and effective in inhibiting inflammation-associated cancer, and is therefore a potential strategy for recurrence prevention in patients with early-stage HCC treated with PHx.

Bilateral retinal microglial response to unilateral optic nerve transection in rats

When retinal ganglion cells undergo apoptosis after optic nerve (ON) injury, microglial cells proliferate and promptly clear the degenerated debris in the ipsilateral retina. However, microglial changes in the contralateral retina have not been fully elucidated. This study characterized the long-term bilateral retinal microglial responses after unilateral ON transection. We analyzed the time course of proliferation and morphology changes of microglial cells, between 3days and 12weeks post ON transection, of undisturbed and reactive microglia in bilateral retinas of adult Fischer rats with unilateral ON transection. Microglia in retinas without ON transection were distributed homogeneously and possessed a highly ramified morphology, as judged by immunohistochemistry for ionized calcium-binding adapter molecule 1 (Iba1). After ON transection, microglia density in the ipsilateral retina increased gradually from 3days to 2weeks, and decreased from 3weeks to 12weeks, along with dramatic inverted alteration of process branch points of microglia in the ganglion cell layer (GCL). Transformation of ramified microglia into ameboid-like macrophages with few branching processes was observed in the ipsilateral retina from 1week to 3weeks. Though an increase in microglial density was weak in the contralateral retina and could only be statistically detected in the central retina, the morphological alteration over time was obvious and similar to that of the ipsilateral retina. In the inner plexiform layer (IPL), cell density and morphological changes of microglia in both the ipsilateral and contralateral retina were not prominent. These findings indicates that, though proliferation of microglial cells is weak in the contralateral retina after unilateral ON transection, conspicuous alterations in microglial morphology occur bilaterally. These suggest that using the contralateral retina as a control in studies of retinal degeneration should be considered with caution.

Comprehensive characterization of human adipose tissue-derived stem cells expanded in vitro

Adipose tissue seems to be a rich and safe source of mesenchymal stem cells (MSCs). The present study was aimed to investigate the biological and morphological characteristics of human adipose tissue-derived stem cells (ATSCs). Light and transmission electron microscopy were used. Course of proliferation was analyzed by growth curve. Expression of surface antigens was assessed by flow cytometry. Chondrogenic potential was assessed by immunohistochemistry. Obtained results showed morphology typical of fibroblastoid cells. TEM analysis proved ultrastructural morphology similar to MSCs from other sources. ATSCs reflected their proteosynthetic and metabolic activity. Each cell had irregular shape of nucleus with noticeable nucleoli. Abundant cisterns of rough endoplasmic reticulum were present in their cytoplasm. Karyotype mapping showed normal count of human chromosomes (46,XX). The growth curve revealed high capability for proliferation and population doubling time was 27.36 hours. ATSCs were positive for CD13, CD29, CD44, CD73, CD90, CD105 and CD106, but did not express CD14, CD34, CD45 and HLA-DR. It was also proved that ATSCs underwent chondrogenic differentiation in vitro. On the basis of obtained results it should be emphasized that ATSCs are typical MSCs and after further investigations they may be used in tissue engineering and regenerative medicine.

Апоптоз и нейтрофилы в регуляции пролиферации и дифференцировки миелоидных клеток с Ph-хромосомойex vivo

Human myeloid cells with Ph chromosome (Ph+ cells) from chronic myeloid leukemia (CML) in the course of proliferation and differentiation ex vivo are regulated under alternation of cell proliferation and neutrophil maturation stages by consecutive blocking and inducing apoptosis with of neutrophils participation as well bcr/abl, bax and bcl2 genes expression. Apoptosis regulation of three main Ph+ cells types from CML patients depends on alternation sequences of proliferation (1) and maturation (2) cell stages and realized by two ways. The first one is performed by consecutive blocking and inducing apoptosis under 2/1/2 stage alternation. The way is not described early. Neutrophils accumulation correlates with apoprosis blocking. Apoptosis level enhances under neutrophils exhausted. Apoptosis blockage allows cells to proliferate and, thus, to form new portion of neutrophils with consecutive regular their death as well a consequent alternation of apoptosis blocking and inducing. This way regulates proliferation efficiency indexes P/D that reflect Ph+ cells proliferating potential and performs cycle completion for proliferation and differentiation. The second way of apoptosis regulation starts from proliferation stage and performs for 1/2/1 alternations under diminished content of neutrophils and a little increase under next maturation. It leads to resistant depressed apoptosis levels that, at maximal points, are 3-8 times lower than those under alternation 2/1/2. Resistant apoptosis blocking is observed in the Ph+ cells with prolong proliferation or maturation stages, when blasts and myelosytes are accumulated under enhanced bcr/abl and bcl2 > box gene expression and remain under next maturation. Stable apoptosis blocking is accompanied by increasing amounts of blasts and myelocytes and enhancing bcr/abl and bcl 2 > bax expression. This is observed under CML progression. Ph+ cells cultivation may be useful for more distinct diagnostics of CML phases of individual CML patients and optimization of the treatment.

Variations in genomic DNA methylation during the long-term in vitro proliferation of oil palm embryogenic suspension cultures

KEY MESSAGE : The long-term proliferation of embryogenic cell suspensions of oil palm is associated with changes in both genomic methylation rates and embryogenic capacities. In the aim of exploring the relationship between epigenetic stability and the long-term in vitro proliferation of plant tissues, we have studied changes in genomic DNA methylation levels in embryogenic suspensions of oil palm (Elaeis guineensis Jacq.). Five embryogenic callus lines were obtained from selected hybrid seeds and then proliferated as suspension cultures. Each clonal line obtained from a single genotype was subdivided into three independent subclonal lines. Once established, cultures proliferated for 12months and genomic DNA was sampled at 4months intervals for the estimation of global DNA methylation rates through high performance liquid chromatography (HPLC) quantitation of deoxynucleosides. Our results show that in vitro proliferation induces DNA hypermethylation in a time-dependent fashion. Moreover, this trend is statistically significant in several clonal lines and shared between subclonal lines originating from the same genotype. Interestingly, the only clonal line undergoing loss of genomic methylation in the course of proliferation has been found unable to generate somatic embryos. We discuss the possible implications of genome-wide DNA methylation changes in proliferating cells with a view to the maintenance of genomic and epigenomic stability.

Infantile Hemangiomas: New Frontiers

It is a very exciting time for clinicians who are confronted with infantile hemangiomas. So much new information is now available regarding pathogenesis, epidemiology, differential diagnosis, and therapy. These aspects are reviewed in greater detail in the accompanying articles by a group of experienced scientists and clinicians, who help provide a richer and more sophisticated understanding of these common vascular lesions. Hemangiomas are common vascular tumors of infancy. These tumors have a largely predictable course of proliferation, plateau, and eventual involution. As a result, pediatric clinicians confronted with hemangiomas have traditionally emphasized active nonintervention for uncomplicated lesions. Recent observations have suggested that earlier evaluation and consideration of earlier intervention for infantile hemangiomas may lead to better outcomes for affected infants. The most rapid period of hemangioma growth may occur earlier than originally thought. Reviews of serial photography at 1- to 2-week intervals over a 6-month period indicate that the growth velocity of hemangiomas is greatest between 5.5 and 7.5 weeks. Anatomic sites with hemangiomas that could become problematic therefore ideally should be evaluated before 8 weeks of age so that effective interventions can be initiated. 1 Whereas older studies have reported that hemangiomas leave residua in about 10% to 15% of cases, a more recent report looked for any signs of hemangioma residua and found that 69% of involuted hemangiomas demonstrate remaining telangiectasia, atrophic scar, skin surplus, erythema, pigmentary disturbance, or some other textural abnormalities. 2 Although some families may be satisfied with some of these changes, others may not find these acceptable; earlier intervention may provide an improved outcome for these children. Complications may arise as a result of hemangiomas being located at inconvenient anatomic locations, developing ulceration, or having associated embryologic malformations (as seen with segmental hemangiomas of the head and neck or in the lumbosacral and genital

Development of the olfactory system in turbot ( Psetta maxima L.)

We have examined the histogenesis of the olfactory system during turbot development using histological and immunohistochemical methods. Proliferating cell nuclear antigen (PCNA) immunohistochemistry was used to detect dividing cells, whereas calretinin (CR) immunohistochemistry was used to distinguish some neuronal components of the olfactory system. Around hatching, the olfactory placode of embryos transforms into an olfactory pit, which enlarges progressively during development. In metamorphic turbots, the right olfactory organ moves to the tip of the head. Each olfactory chamber opens to the external medium by two nostrils and accessory nasal sacs develop during metamorphosis. The order of birth of olfactory receptor cells in the sensory epithelium follows the pattern of most teleosts: ciliated cells differentiate prior to microvillous cells in turbot larvae, and crypt cells are generated during metamorphosis. Axons of olfactory sensory neurons reach the rostral forebrain by hatching, and calretinin-immunoreactive (CR-ir) glomerular fields were apparent during the subsequent larval development. During metamorphosis olfactory bulbs become strongly distorted by head torsion and glomeruli acquire asymmetric organization. The spatio-temporal course of proliferation in the olfactory system reveals changes in the distribution of dividing cells in the sensory epithelium throughout the developmental period investigated. In the olfactory bulb, proliferative activity becomes restricted to the ventral periventricular zone in turbot larvae, as well as in metamorphic specimens.

Osteoblast and Fibroblast Culture Proliferation on Injectable Calcium Ceramics Polymer Composite

Considerable demand for the repair of bone defects cannot be met solely by using biological donor materials. Hence, the use of biocomposites will most likely be increased in reconstructive surgery in future. Metallic implants cannot be used in all cases, because the defects in the skeleton vary greatly, differing from each other in their shape, size, anatomic location, and physiological weight-bearing in the anatomic location. Therefore, more sophisticated orthopaedic materials (e.g. non-metallic fibre-reinforced composites and particulate filler composites) should be available for clinical practice. Our studies have focused on the development of injectable composites of biostable bone cements, i.e. in situ curable resin systems containing impregnated calcium ceramics particles. The properties of the bone cement composites aspire to simulate as closely as possible the mechanical and structural properties of bone. The purpose of this study was to evaluate the in vitro cell proliferation on the experimental injectable biostable polymer modified with calcium ceramics. In the course of proliferation, the cell activity on the calcium ceramics containing biostable polymer composite increased throughout the experiment. As a conclusion, this cell proliferation study indicated that the studied biocomposite has a good potential to promote cell interaction.

Human neural precursor cells continue to proliferate and exhibit low cell death after transplantation to the injured rat spinal cord

During the last decade, the interest in stem and progenitor cells, and their applications in spinal cord injuries have steadily increased. However, little is known about proliferation and cell death mechanisms in these cells after transplantation to the spinal cord. The aim of the present project was to study cell turn-over, i.e. total cell number, with time course of proliferation and cell death, in human neural precursor cells (NPCs) after transplantation to the injured rat spinal cord. Immunodeficient rats were subjected to lateral clip compression injuries, transplanted with neurospheres of human forebrain-derived NPCs two weeks after lesion, and sacrificed after 6 h, 1, 3, 10, or 21 days. Cell death was assessed by quantifying human cells immunoreactive for active caspase-3 and calpain 1-dependent fodrin breakdown products (FBDP). The results showed that after an initial drop, the number of implanted cells increased over time after transplantation. Cell proliferation was substantial, with 34% of human cells being immunoreactive for proliferating cell nuclear antigen at 6 h, but which declined over the next few days. The fractions of caspase-3-, and FBDP-immunoreactive cells were remarkably low, together representing 18% of all human cells at 6 h, and rapidly decreasing the next few days. Our results show that already 10 days after spinal cord transplantation of human NPCs as intact neurospheres, the number of human cells exceeded the initially implanted, which was the result of marked cell proliferation in combination with a low rate of apoptotic and non-apoptotic cell death taking place early after transplantation.

Pediatric Orbit Tumors and Tumorlike Lesions: Nonosseous Lesions of the Extraocular Orbit

The histologic spectrum of nonosseous tumors and tumorlike lesions of the extraocular orbit in children differs from that in adults, and the appearance of these lesions at imaging reflects their pathologic features. Rhabdomyosarcoma is the most common extraocular orbital tumor in children. This neoplasm usually manifests in young children, grows quite rapidly, and is fairly vascular. Vasculogenic lesions are common orbital lesions in newborns and young infants. The most prevalent of these are infantile hemangioma, a true neoplasm, and venous-lymphatic malformation, a developmental anomaly. Hemangioma is quite vascular, has a predictable course of proliferation followed by slow involution, and is distinguished on magnetic resonance images by the finding of flow voids within the mass and at its periphery. Venous-lymphatic malformation in the orbit is an anomaly of venous and lymphatic development that is characterized by unenhancing, cystic lymphatic and enhancing, solid venous components. Intralesional hemorrhage is common and frequently produces distinctive fluid-fluid levels within the cystic portions. Unlike hemangiomas, venous-lymphatic malformations grow with the patient and never involute spontaneously. Infantile fibromatosis is one of the fibromatoses and affects newborns and young infants. The tumor is nodular and composed of a zonal architecture, with frequent hemorrhage or necrosis in the central portion, characteristics that confer a target appearance at imaging. These lesions usually stop growing or spontaneously regress. All of these extraocular masses typically manifest with proptosis, and imaging differentiation is desirable because the treatments and prognoses vary greatly.

Human progenitor cells isolated from the developing cortex undergo decreased neurogenesis and eventual senescence following expansion in vitro

Isolation of a true self-renewing stem cell from the human brain would be of great interest as a reliable source of neural tissue. Here, we report that human fetal cortical cells grown in epidermal growth factor expressed low levels of telomerase and telomeres in these cultures shortened over time leading to growth arrest after 30 weeks. Following leukemia inhibitory factor (LIF) supplementation, growth rates and telomerase expression increased. This was best demonstrated following cell cycle synchronization and staining for telomerase using immunocytochemistry. This increase in activity resulted in the maintenance of telomeres at approximately 7 kb for more than 60 weeks in vitro. However, all cultures displayed a lack of oligodendrotye production, decreases in neurogenesis over time and underwent replicative senescence associated with increased expression of p21 before 70 weeks in vitro. Thus, under our culture conditions, these cells are not stable, multipotent, telomerase expressing self-renewing stem cells. They may be more accurately described as human neural progenitor cells (hNPC) with limited lifespan and bi-potent potential (neurons/astrocytes). Interestingly, hNPC follow a course of proliferation, neuronal production and growth arrest similar to that seen during expansion and development of the human cortex, thus providing a possible model neural system. Furthermore, due to their high expansion potential and lack of tumorogenicity, these cells remain a unique and safe source of tissue for clinical transplantation.

The role of GLUT1 immunostaining in the diagnosis and classification of liver vascular tumors in children

Background/Aim GLUT1 is an erythrocyte-type glucose transporter protein typically expressed in cutaneous proliferating hemangioma. Immunostaining for GLUT1 is becoming valuable for predicting the outcome of vascular skin tumors. Liver vascular tumors (LVTs) are a serious challenge for pediatric surgeons because of their often severe and sometimes unpredictable clinical course. To improve therapeutic strategies, we designed this study in which we tested in pathology specimens of LVT the hypothesis that GLUT1 expression could be useful to understand and classify LVT. Material and methods In the last 10 years, we treated 20 children with LVT. Pathology specimens from biopsy, excision, or autopsy were available in 11 of them. The paraffin sections were immunostained for GLUT1 and also for Ki-67 to assess the proportion of proliferating cells. Patients were divided into 2 groups: GLUT1-positive (n = 4) and GLUT1-negative (n = 7) that were compared for age at diagnosis, survival, and proportion of proliferating cells. Nonparametric and χ 2 tests were used for statistical analysis as appropriate. Results Mean age at diagnosis was higher in GLUT1-positive group, although not statistically significant in comparison with GLUT1-negative (308 ± 515 vs 70 ± 51 days, respectively). Three of 4 children in GLUT1-positive group died versus 1 of 7 in the GLUT1-negative group (not significant). All GLUT1-positive tumors were multicentric hemangiomata without central necrosis and only 1 with large vessels. Among GLUT1-negative tumors, 5 were solitary masses and 2 were multicentric (the value of the last 2 specimens was uncertain), 2 had central necrosis, and 2 had large vessels. Proliferation index was 18% ± 1.42% and 1.42% ± 0.97%, respectively, in each group ( P < .05). Conclusions GLUT1-positive tumors have significantly higher proliferation rates than negative ones. Mortality tended to be higher in children with GLUT1-positive tumors. Positive GLUT1 immunostaining is likely specific for proliferating hemangioma, and it predicts the typical course of proliferation followed by involution.

Keratinocyte growth factor therapy in murine oleic acid-induced acute lung injury

Alveolar type II (ATII) cell proliferation and differentiation are important mechanisms in repair following injury to the alveolar epithelium. KGF is a potent ATII cell mitogen, which has been demonstrated to be protective in a number of animal models of lung injury. We have assessed the effect of recombinant human KGF (rhKGF) and liposome-mediated KGF gene delivery in vivo and evaluated the potential of KGF as a therapy for acute lung injury in mice. rhKGF was administered intratracheally in male BALB/c mice to assess dose response and time course of proliferation. SP-B immunohistochemistry demonstrated significant increases in ATII cell numbers at all rhKGF doses compared with control animals and peaked 2 days following administration of 10 mg/kg rhKGF. Protein therapy in general is very expensive, and gene therapy has been suggested as a cheaper alternative for many protein replacement therapies. We evaluated the effect of topical and systemic liposome-mediated KGF-gene delivery on ATII cell proliferation. SP-B immunohistochemistry showed only modest increases in ATII cell numbers following gene delivery, and these approaches were therefore not believed to be capable of reaching therapeutic levels. The effect of rhKGF was evaluated in a murine model of OA-induced lung injury. This model was found to be associated with significant alveolar damage leading to severe impairment of gas exchange and lung compliance. Pretreatment with rhKGF 2 days before intravenous OA challenge resulted in significant improvements in PO2, PCO2, and lung compliance. This study suggests the feasibility of KGF as a therapy for acute lung injury.

Transiently Arterialized Hemangiomas: Relevant Clinical and Cardiac Issues

Although the majority of hemangiomas of infancy undergo an uncomplicated, predictable course of proliferation followed by involution, a subset of patients sustain a more fastidious course. These include hemangiomas that, at least during part of their life cycle, have a high flow (arterial) component. Hemangiomas with high flow are most frequently located in the liver. These lesions can lead to significant morbidity, with high output cardiac failure. We have identified nonhepatic hemangiomas that have an apparent propensity to develop a high flow element--the parotid, upper arm, scalp, and rarely the upper lip--and present our experience in this report. These lesions appear to behave as transiently "arterialized" hemangiomas.

The Response of Uninvolved Skin of Patients with Psoriasis to Single and Repeated Applications of Dithranol Cream: An Immunohistochemical Assessment

Dithranol is one of the most effective topical treatments for patients with psoriasis. The well-known irritation is a serious limitation. In an earlier study we investigated the inflammatory response to single and repeated applications with dithranol 2% cream in skin from healthy volunteers. In the present study, we assessed the clinical and cell-biological response of single and repeated challenges with dithranol 2% cream in uninvolved skin of patients with psoriasis. A striking difference between the two studies is the late phase in the single-challenge group after 8 days, showing a longer-lasting response in the uninvolved skin compared to normal skin with respect to proliferation and inflammation markers. A controlled and synchronised irritation by dithranol might induce anti-inflammatory processes and as such constitute an antipsoriatic principle. It is attractive to speculate that in psoriasis the induction of anti-inflammatory responses is defective. Following repeated applications of dithranol, a more uniform course of proliferation, differentiation and inflammation markers was observed in the uninvolved psoriatic skin as compared to the skin of healthy volunteers. Again a defect in the induction of anti-inflammatory responses might account for this event. In view of these differences between normal skin and psoriatic uninvolved skin, it may be advisable to use the uninvolved skin of patients with psoriasis in further studies on the interference between dithranol irritancy and various anti-inflammatory agents.

Proliferation pattern changes in the zebrafish brain from embryonic through early postembryonic stages.

Proliferating cell nuclear antigen (PCNA)-immunohistochemistry was used for demonstrating the spatiotemporal course of proliferation in the brains of embryonic (24 h) through postembryonic (5 days) zebrafish (Danio rerio). Parallel series of the same stages prepared according to the combined Bodian fiber silver-stain/cresyl Nissl-stain were used for improved morphogenetic analysis (i.e., in detecting critical neuroanatomical landmarks). Starting from an essentially ubiquituous proliferation throughout the neural tube before 24 h, PCNA-immunoreactive cells become successively more restricted to a subset of gray matter cells around 48 h and even more distinct proliferation zones become apparent around 72 h. Both hindbrain and forebrain reveal a segmental organization with regard to the distribution of proliferation zones, but the rhombomeric pattern of PCNA-immunoreactive cells emerging between 48 h and 72 h precedes a similar prosomeric pattern by about 48 h. Two divisions of the midbrain-hindbrain boundary are described here morphologically and both are demonstrated to show sustained proliferation throughout the investigated time frame. In contrast, proliferation in the adjacent mesencephalic and cerebellar domains is rapidly down-regulated during the first 5 days of development.

Myotube morphology, and expression and distribution of collagen type I during normal and low score normal avian satellite cell myogenesis

Myogenic satellite cells are essential for postnatal muscle growth and the regeneration of muscle in response to injury. An understanding of how the extracellular matrix affects satellite cell activity, and the temporal and spatial expression of extracellular matrix macromolecules is largely unknown. In the avian genetic muscle weakness, low score normal (LSN), satellite cell proliferation and differentiation rates are significantly lower than that observed in normal chicken satellite cells, which may be attributed to a late embryonic increase in the expression of decorin. Satellite cell-derived morphological properties, collagen type I expression, and the spatial distribution of collagen type I were investigated during normal and LSN satellite cell proliferation and differentiation. These studies showed a decrease in LSN myotube length and the number of nuclei per myotube. Collagen type I expression was similar between the LSN and normal satellite cell cultures during the course of proliferation and differentiation. However, the spatial distribution of collagen type I was altered in the LSN cultures 48 h after the initiation of fusion. The LSN cultures exhibited a premature extracellular distribution of collagen type I compared to the normal satellite cells.

The effect of retinoic acid on Ito cell proliferation and content of DNA and RNA.

The development of liver fibrosis is due to an imbalance between synthesis and degradation of extracellular matrix. Recent studies have shown that Ito cells which are located along the sinuses of liver, can store and metabolize Vit A, and are the main cells that produce collagen, among which type I, III and IV and laminin, account for 80%-95% of the total hepatic collagen[1]. Ito cells in the course of proliferation and synthesis of collagen showed a reduction of Vit A contents and retinoic acid receptors[2]. This study was designed to investigate the effect of retinoic acid on Ito cell proliferation and the contents of DNA/RNA and to analyse further its mechanism or pathways.