In the present review we discuss two interrelated events-axonal damage and repair-known to occur ... more In the present review we discuss two interrelated events-axonal damage and repair-known to occur after spinal cord injury (SCI) in the zebrafish. Adult zebrafish are capable of regenerating axonal tracts and can restore full functionality after SCI. Unlike fish, axon regeneration in the adult mammalian central nervous system is extremely limited. As a consequence of an injury there is very little repair of disengaged axons and therefore functional deficit persists after SCI in adult mammals. In contrast, peripheral nervous system axons readily regenerate following injury and hence allow functional recovery both in mammals and fish. A better mechanistic understanding of these three scenarios could provide a more comprehensive insight into the success or failure of axonal regeneration after SCI. This review summarizes the present understanding of the cellular and molecular basis of axonal regeneration, in both the peripheral nervous system and the central nervous system, and large scale gene expression analysis is used to focus on different events during regeneration. The discovery and identification of genes involved in zebrafish spinal cord regen-eration and subsequent functional experimentation will provide more insight into the endogenous mechanism of myelination and remyelination. Furthermore, precise knowledge of the mechanism underlying the extraordinary axonal regeneration process in zebrafish will also allow us to unravel the potential therapeutic strategies to be implemented for enhancing regrowth and remyelination of axons in mammals.
We reported earlier on the occurrence of cholinephosphotransferase in the mitochondria of guinea ... more We reported earlier on the occurrence of cholinephosphotransferase in the mitochondria of guinea pig lung. In order to determine whether organ and/or species specificities exist in regard to the cholinephosphotransferase activity in mitochondria, we have compared the subcellular distribution of the enzyme in the liver and lungs of rats and guinea pigs. Even though the activity of the enzyme was higher in microsomes than it was in mitochondria, the mitochondrial activity was authentic in both tissues of both species. The authenticity of mitochondrial activity was established by marker enzyme studies and ultrastructural examination of mitochondrial preparations.
I t is known that thyroid hormone enhances the biosynthesis of phosphatidylcholine in the lung. T... more I t is known that thyroid hormone enhances the biosynthesis of phosphatidylcholine in the lung. The purpose of the present study was to investigate the effects of thyroid hormone on the activity of cholinephosphotransferase, the terminal enzyme in the CDP-choline pathway, in guinea pig lung mitochondria and microsomes. Intramuscular injection of triiodothyronine (T3, 0. 2 5 4 mglkg body wt) stimulated the activities of both mitochondria1 and rnicrosomal enzymes in a dose-dependent manner. However, the stimulation was much more pronounced in the microsomes than in the mitochondria. The stirnulatory effect of T3 was blocked by the intraperitoneal injection of both actinomycin D and cycloheximide in the microsomes, whereas in the mitochondria, the hormonal effect was blocked only by cycloheximide. Thus, it is suggested that T3 stimulates not only the nucleocytoplasmic system for the de novo synthesis of the enzyme, but possibly also the regulation of the transport of the synthesized protein into the mitochondria. Furthermore, administration of T3 produced an increase in the uptake and incorporation of [14C]choline into phospholipids of lung slices in vitro. However, this effect was blocked by intraperitoneal injection of both actinomycin D and cycloheximide. Thus, the change in CPT activity by T3 in mitochondria is not reflected by enhanced incorporation of choline into phosphatidylcholine.
We have reported earlier that cholinephosphotransferase (EC 2.7.8.2) is present in both mitochond... more We have reported earlier that cholinephosphotransferase (EC 2.7.8.2) is present in both mitochondria and microsomes of fetal guinea pig lung. This study was designed to compare the properties of mitochondrial and microsomal cholinephosphotransferase in fetal guinea pig lung. Various parameters, such as substrate specificity, K m values, sensitivity to N-ethylmaleimide, dithiothreitol and trypsin were measured. Both showed significant preference for unsaturated diacylglycerols over saturated diacylglycerols. Data on K m and Vmax indicate that the affinity of this enzyme for different diacylglycerols varies between the two forms. The IDs0 values for N-ethylmaleimide were 20 mM and 12.5 mM for the mitochondrial and microsomal form of the enzyme, respectively. Dithiothreitol showed an inhibitory effect on both; however, the mitochondrial form was inhibited less than the microsomal form. The effects of N-ethylmaleimide and dithiothreitol on both forms of enzyme indicated that the microsomal cholinephosphotransferase requires a higher concentration of-SH for its activity than the mitochondrial enzyme does. The enzyme was inhibited by trypsin in both mitochondria and microsome under isotonic condition suggesting that this enzyme is on the outside of the membrane in both endoplasmic reticulum and mitochondria.
Adult skeletal muscles are composed of different ®bre types. What initiates the distinctive muscl... more Adult skeletal muscles are composed of different ®bre types. What initiates the distinctive muscle ®bre type-speci®c specialization in a developing embryo is still controversial. In vitro studies of avian muscles have shown the expression of one of the slow myosin heavy chains, SM2, in only some myotubes. In this report we demonstrate the expression of another slow myosin heavy chain, SM1, restricted to only some chicken myotubes (presumptive slow) in vitro. We also demonstrate that as is the case for avian species, distinct fast and slow myogenic cells are detectable in mammalian species, human and rat, during in vitro development in the absence of innervation. While antibodies to fast myosin heavy chains stained all myotubes dark in these muscle cell cultures, antibodies to slow myosin heavy chains stained only a proportion of the myotubes (presumptive slow). The other myotubes were either unstained or only weakly stained with slow myosin heavy chain antibodies. The muscle cell cultures prepared from different developmental stages of rat skeletal muscles showed a reduction in the number of slow myosin heavy chain-positive myotubes with advancing foetal growth. It is concluded that embryonic myogenic cells that are likely to form distinct fast or slow muscle ®bre types are intrinsically heterogeneous, not only in avian but also in mammalian species, although extrinsic factors reinforce and modify such commitment throughout subsequent development. Ó Kluwer Academic Publishers.
Zebrafish proves to be an excellent model system to study spinal cord regeneration because it can... more Zebrafish proves to be an excellent model system to study spinal cord regeneration because it can repair its disengaged axons and replace lost cells after injury, allowing the animal to make functional recovery. We have characterized injury response following crush injury, which is comparable to the mammalian mode of injury. Infiltrations of blood cells during early phases involve macrophages that are important in debris clearance and probably in suppression of inflammatory response. Unlike mammals where secondary injury mechanisms lead to apoptotic death of both neurons and glia, here we observe a beneficial role of apoptotic cell death. Injury-induced proliferation, presence of radial glia cells, and their role as progenitor all contribute to cellular replacement and successful neurogenesis after injury in adult zebrafish. Together with cell replacement phenomenon, there is creation of a permissive environment that includes the absence or clearance of myelin debris, presence of Schwann cells, and absence of inflammatory response.
Toxic oil syndrome (TOS) is caused by ingestion of denatured edible oils. Even though the etiolog... more Toxic oil syndrome (TOS) is caused by ingestion of denatured edible oils. Even though the etiology and pathogenesis of this disease are not fully known, it is quite clear that generation of free radicals caused by ingestion of fatty acid anilides is responsible for the pathogenetic mechanism in many TOS patients. Fatty acid anilides may also alter the free radical status of lungs and erythrocytes; this possibility may shed some light on understanding toxic oil syndrome. The present study describes the effects of oral administration of fatty acid anilides on the activities of major enzymes involved in the oxygen defense systems of lungs and erythrocytes. Feeding fatty acid anilides caused an increase in the superoxide dismutase (SOD) activity in erythrocytes, whereas it caused a decrease in the SOD activity in lungs. GSH-Px activity was not significantly changed in erythrocytes but was decreased in lungs. Although the activity of catalase was increased only by a higher dose in the erythrocytes, it was not affected in the lung at any dosage. Even though the ingestion of fatty acid anilides caused an increase in the SOD activity in the erythrocytes and a decrease in the SOD activity in the lungs, there was an increase in the lipid peroxidation in both cases. The increase in lipid peroxidation in erythrocytes is probably caused by the accumulation of H202, and that in the lungs is due to the accumulation of superoxide anion.
The International Journal of Developmental Biology, 2020
The zebrafish (Danio rerio), among all amniotes is emerging as a powerful model to study vertebra... more The zebrafish (Danio rerio), among all amniotes is emerging as a powerful model to study vertebrate organogenesis and regeneration. In contrast to mammals, the adult zebrafish is capable of regenerating damaged axonal tracts; it can replace neurons and glia lost after spinal cord injury (SCI) and functionally recover. In the present paper, we report ultrastructural and cell biological analyses of regeneration processes after SCI. We have focused on event specific analyses of spinal cord regeneration involving different neuronal and glial cell progenitors, such as radial glia, oligodendrocyte progenitors (OPC), and Schwann cells. While comparing the different events, we frequently refer to previous ultrastructural analyses of central nervous system (CNS) injury in higher vertebrates. Our data show (a) the cellular events following injury, such as cell death and proliferation; (b) demyelination and remyelination followed by target innervation and regeneration of synaptic junctions and...
In the present review we discuss two interrelated events-axonal damage and repair-known to occur ... more In the present review we discuss two interrelated events-axonal damage and repair-known to occur after spinal cord injury (SCI) in the zebrafish. Adult zebrafish are capable of regenerating axonal tracts and can restore full functionality after SCI. Unlike fish, axon regeneration in the adult mammalian central nervous system is extremely limited. As a consequence of an injury there is very little repair of disengaged axons and therefore functional deficit persists after SCI in adult mammals. In contrast, peripheral nervous system axons readily regenerate following injury and hence allow functional recovery both in mammals and fish. A better mechanistic understanding of these three scenarios could provide a more comprehensive insight into the success or failure of axonal regeneration after SCI. This review summarizes the present understanding of the cellular and molecular basis of axonal regeneration, in both the peripheral nervous system and the central nervous system, and large sca...
Spinal cord injury (SCI) in mammals leads to failure of both sensory and motor functions, due to ... more Spinal cord injury (SCI) in mammals leads to failure of both sensory and motor functions, due to lack of axonal regrowth below the level of injury as well as inability to replace lost neural cells and to stimulate neurogenesis. In contrast, fish and amphibians are capable of regenerating a variety of their organs like limb/fin, jaw, heart and various parts of the central nervous system (CNS). Zebrafish embryo and adult has become a very popular model to study developmental biology, cell biology and regeneration for various reasons. Adult zebrafish, one of the most important vertebrate models to study regeneration, can regenerate many of their body parts like fin, jaw, heart and CNS. In the present article we provide information on how to inflict different injury modalities in adult fish spinal cord. Presently, the significant focus of mammalian SCI is to use crush and contusion injury. To generate an entity comparable to the mammalian mode of injury, we have introduced the crush model in adult zebrafish along with complete transection injury, which is also known to be a valuable model to study axonal regeneration. Here we provide full description of the highly reproducible surgical procedures including some representative results. This protocol has been adapted from our previous publications, viz. Hui et al., 2010 and Hui et al., 2014. Briefly, we have described the two different injury modalities, crush and complete transection, and demonstrated the outcome of inflicting these injuries in the adult zebrafish cord by histological analysis of the tissues.
Regeneration in the animal kingdom is one of the most fascinating problems that have allowed scie... more Regeneration in the animal kingdom is one of the most fascinating problems that have allowed scientists to address many issues of fundamental importance in basic biology. However, we came to know that the regenerative capability may vary across different species. Among vertebrates, fish and amphibians are capable of regenerating a variety of complex organs through epimorphosis. Zebrafish is an excellent animal model, which can repair several organs like damaged retina, severed spinal cord, injured brain and heart, and amputated fins. The focus of the present paper is on spinal cord regeneration in adult zebrafish. We intend to discuss our current understanding of the cellular and molecular mechanism(s) that allows formation of proliferating progenitors and controls neurogenesis, which involve changes in epigenetic and transcription programs. Unlike mammals, zebrafish retains radial glia, a nonneuronal cell type in their adult central nervous system. Injury induced proliferation invo...
Zebrafish can repair their injured brain and spinal cord after injury unlike adult mammalian cent... more Zebrafish can repair their injured brain and spinal cord after injury unlike adult mammalian central nervous system. Any injury to zebrafish spinal cord would lead to increased proliferation and neurogenesis. There are presences of proliferating progenitors from which both neuronal and glial loss can be reversed by appropriately generating new neurons and glia. We have demonstrated the presence of multiple progenitors, which are different types of proliferating populations like Sox2 + neural progenitor, A2B5 + astrocyte/ glial progenitor, NG2 + oligodendrocyte progenitor, radial glia and Schwann cell like progenitor. We analyzed the expression levels of two common markers of dedifferentiation like msx-b and vimentin during regeneration along with some of the pluripotency associated factors to explore the possible role of these two processes. Among the several key factors related to pluripotency, pou5f1 and sox2 are upregulated during regeneration and associated with activation of neural progenitor cells. Uncovering the molecular mechanism for endogenous regeneration of adult zebrafish spinal cord would give us more clues on important targets for future therapeutic approach in mammalian spinal cord repair and regeneration.
Journal of muscle research and cell motility, 1998
To analyse the myogenic cell lineages in human foetal skeletal muscle, muscle cell cultures were ... more To analyse the myogenic cell lineages in human foetal skeletal muscle, muscle cell cultures were prepared from different foetal stages of development. The in vitro muscle cell phenotype was defined by staining the myotubes with antibodies to fast and slow skeletal muscle type myosin heavy chains using immunoperoxidase or double immunofluorescence procedures. The antibodies to fast skeletal muscle myosin heavy chains stained nearly all myotubes dark in cell cultures prepared from quadriceps muscles at 10-18 weeks of gestation. The antibodies to slow skeletal muscle myosin heavy chains, in contrast, stained only 10-40% of the myotubes very dark. The remaining myotubes were further subdivided into two populations, one of which was unstained while the other stained with variable intensity for slow myosin heavy chain. The slow myosin heavy chain staining was not influenced by the nature of the substratum used to culture these cells, although the growth of muscle cell cultures was greatly...
The International journal of developmental biology, 1994
The regenerating amphibian jaw represents an important model for studying pattern formation and t... more The regenerating amphibian jaw represents an important model for studying pattern formation and the mechanisms underlying regeneration of facial structures. We have studied regeneration of upper and lower jaws in the urodele amphibian, Notophthalmus viridescens, using whole mount preparations stained for bone and cartilage, scanning electron microscopy and immunocytochemistry to further characterize these regenerating systems. In addition, we have investigated whether lower jaws of adults and larvae display similar regenerative ability. Although in adult animals the original shape of both the lower and upper jaws is rather faithfully reproduced following amputation, and the teeth and oral mucosa with its specialized sensory organs fully regenerate, significant differences in the regenerative ability of the various skeletal elements are observed. In fact, only tooth-bearing skeletal elements ossify, while the other elements of the regenerated skeleton remain cartilaginous for as long...
The International journal of developmental biology, 1996
The vitamin A derivative retinoic acid (RA) is a powerful teratogen which can induce severe crani... more The vitamin A derivative retinoic acid (RA) is a powerful teratogen which can induce severe craniofacial and limb malformations if administered at certain stages of gestation. In addition this compound has been shown to affect patterning in regenerating systems. A classical example is the induction of supernumerary structures along the proximodistal axis of the regenerating amphibian limb. We have investigated the effect of RA on other regenerating systems, the amphibian lower and upper jaws, both in developing and adult animals. We report here that RA does not induce formation of extra structures either in the lower or in the upper jaw of adult newts under experimental conditions where duplications of the regenerating limb occur. However, RA selectively induces severe malformations in the upper jaw regenerate that resemble those induced in avian and mammalian embryos. Analysis of the expression of the newt retinoic acid receptors RAR alpha and delta in upper and lower jaws showed t...
In the present review we discuss two interrelated events-axonal damage and repair-known to occur ... more In the present review we discuss two interrelated events-axonal damage and repair-known to occur after spinal cord injury (SCI) in the zebrafish. Adult zebrafish are capable of regenerating axonal tracts and can restore full functionality after SCI. Unlike fish, axon regeneration in the adult mammalian central nervous system is extremely limited. As a consequence of an injury there is very little repair of disengaged axons and therefore functional deficit persists after SCI in adult mammals. In contrast, peripheral nervous system axons readily regenerate following injury and hence allow functional recovery both in mammals and fish. A better mechanistic understanding of these three scenarios could provide a more comprehensive insight into the success or failure of axonal regeneration after SCI. This review summarizes the present understanding of the cellular and molecular basis of axonal regeneration, in both the peripheral nervous system and the central nervous system, and large scale gene expression analysis is used to focus on different events during regeneration. The discovery and identification of genes involved in zebrafish spinal cord regen-eration and subsequent functional experimentation will provide more insight into the endogenous mechanism of myelination and remyelination. Furthermore, precise knowledge of the mechanism underlying the extraordinary axonal regeneration process in zebrafish will also allow us to unravel the potential therapeutic strategies to be implemented for enhancing regrowth and remyelination of axons in mammals.
We reported earlier on the occurrence of cholinephosphotransferase in the mitochondria of guinea ... more We reported earlier on the occurrence of cholinephosphotransferase in the mitochondria of guinea pig lung. In order to determine whether organ and/or species specificities exist in regard to the cholinephosphotransferase activity in mitochondria, we have compared the subcellular distribution of the enzyme in the liver and lungs of rats and guinea pigs. Even though the activity of the enzyme was higher in microsomes than it was in mitochondria, the mitochondrial activity was authentic in both tissues of both species. The authenticity of mitochondrial activity was established by marker enzyme studies and ultrastructural examination of mitochondrial preparations.
I t is known that thyroid hormone enhances the biosynthesis of phosphatidylcholine in the lung. T... more I t is known that thyroid hormone enhances the biosynthesis of phosphatidylcholine in the lung. The purpose of the present study was to investigate the effects of thyroid hormone on the activity of cholinephosphotransferase, the terminal enzyme in the CDP-choline pathway, in guinea pig lung mitochondria and microsomes. Intramuscular injection of triiodothyronine (T3, 0. 2 5 4 mglkg body wt) stimulated the activities of both mitochondria1 and rnicrosomal enzymes in a dose-dependent manner. However, the stimulation was much more pronounced in the microsomes than in the mitochondria. The stirnulatory effect of T3 was blocked by the intraperitoneal injection of both actinomycin D and cycloheximide in the microsomes, whereas in the mitochondria, the hormonal effect was blocked only by cycloheximide. Thus, it is suggested that T3 stimulates not only the nucleocytoplasmic system for the de novo synthesis of the enzyme, but possibly also the regulation of the transport of the synthesized protein into the mitochondria. Furthermore, administration of T3 produced an increase in the uptake and incorporation of [14C]choline into phospholipids of lung slices in vitro. However, this effect was blocked by intraperitoneal injection of both actinomycin D and cycloheximide. Thus, the change in CPT activity by T3 in mitochondria is not reflected by enhanced incorporation of choline into phosphatidylcholine.
We have reported earlier that cholinephosphotransferase (EC 2.7.8.2) is present in both mitochond... more We have reported earlier that cholinephosphotransferase (EC 2.7.8.2) is present in both mitochondria and microsomes of fetal guinea pig lung. This study was designed to compare the properties of mitochondrial and microsomal cholinephosphotransferase in fetal guinea pig lung. Various parameters, such as substrate specificity, K m values, sensitivity to N-ethylmaleimide, dithiothreitol and trypsin were measured. Both showed significant preference for unsaturated diacylglycerols over saturated diacylglycerols. Data on K m and Vmax indicate that the affinity of this enzyme for different diacylglycerols varies between the two forms. The IDs0 values for N-ethylmaleimide were 20 mM and 12.5 mM for the mitochondrial and microsomal form of the enzyme, respectively. Dithiothreitol showed an inhibitory effect on both; however, the mitochondrial form was inhibited less than the microsomal form. The effects of N-ethylmaleimide and dithiothreitol on both forms of enzyme indicated that the microsomal cholinephosphotransferase requires a higher concentration of-SH for its activity than the mitochondrial enzyme does. The enzyme was inhibited by trypsin in both mitochondria and microsome under isotonic condition suggesting that this enzyme is on the outside of the membrane in both endoplasmic reticulum and mitochondria.
Adult skeletal muscles are composed of different ®bre types. What initiates the distinctive muscl... more Adult skeletal muscles are composed of different ®bre types. What initiates the distinctive muscle ®bre type-speci®c specialization in a developing embryo is still controversial. In vitro studies of avian muscles have shown the expression of one of the slow myosin heavy chains, SM2, in only some myotubes. In this report we demonstrate the expression of another slow myosin heavy chain, SM1, restricted to only some chicken myotubes (presumptive slow) in vitro. We also demonstrate that as is the case for avian species, distinct fast and slow myogenic cells are detectable in mammalian species, human and rat, during in vitro development in the absence of innervation. While antibodies to fast myosin heavy chains stained all myotubes dark in these muscle cell cultures, antibodies to slow myosin heavy chains stained only a proportion of the myotubes (presumptive slow). The other myotubes were either unstained or only weakly stained with slow myosin heavy chain antibodies. The muscle cell cultures prepared from different developmental stages of rat skeletal muscles showed a reduction in the number of slow myosin heavy chain-positive myotubes with advancing foetal growth. It is concluded that embryonic myogenic cells that are likely to form distinct fast or slow muscle ®bre types are intrinsically heterogeneous, not only in avian but also in mammalian species, although extrinsic factors reinforce and modify such commitment throughout subsequent development. Ó Kluwer Academic Publishers.
Zebrafish proves to be an excellent model system to study spinal cord regeneration because it can... more Zebrafish proves to be an excellent model system to study spinal cord regeneration because it can repair its disengaged axons and replace lost cells after injury, allowing the animal to make functional recovery. We have characterized injury response following crush injury, which is comparable to the mammalian mode of injury. Infiltrations of blood cells during early phases involve macrophages that are important in debris clearance and probably in suppression of inflammatory response. Unlike mammals where secondary injury mechanisms lead to apoptotic death of both neurons and glia, here we observe a beneficial role of apoptotic cell death. Injury-induced proliferation, presence of radial glia cells, and their role as progenitor all contribute to cellular replacement and successful neurogenesis after injury in adult zebrafish. Together with cell replacement phenomenon, there is creation of a permissive environment that includes the absence or clearance of myelin debris, presence of Schwann cells, and absence of inflammatory response.
Toxic oil syndrome (TOS) is caused by ingestion of denatured edible oils. Even though the etiolog... more Toxic oil syndrome (TOS) is caused by ingestion of denatured edible oils. Even though the etiology and pathogenesis of this disease are not fully known, it is quite clear that generation of free radicals caused by ingestion of fatty acid anilides is responsible for the pathogenetic mechanism in many TOS patients. Fatty acid anilides may also alter the free radical status of lungs and erythrocytes; this possibility may shed some light on understanding toxic oil syndrome. The present study describes the effects of oral administration of fatty acid anilides on the activities of major enzymes involved in the oxygen defense systems of lungs and erythrocytes. Feeding fatty acid anilides caused an increase in the superoxide dismutase (SOD) activity in erythrocytes, whereas it caused a decrease in the SOD activity in lungs. GSH-Px activity was not significantly changed in erythrocytes but was decreased in lungs. Although the activity of catalase was increased only by a higher dose in the erythrocytes, it was not affected in the lung at any dosage. Even though the ingestion of fatty acid anilides caused an increase in the SOD activity in the erythrocytes and a decrease in the SOD activity in the lungs, there was an increase in the lipid peroxidation in both cases. The increase in lipid peroxidation in erythrocytes is probably caused by the accumulation of H202, and that in the lungs is due to the accumulation of superoxide anion.
The International Journal of Developmental Biology, 2020
The zebrafish (Danio rerio), among all amniotes is emerging as a powerful model to study vertebra... more The zebrafish (Danio rerio), among all amniotes is emerging as a powerful model to study vertebrate organogenesis and regeneration. In contrast to mammals, the adult zebrafish is capable of regenerating damaged axonal tracts; it can replace neurons and glia lost after spinal cord injury (SCI) and functionally recover. In the present paper, we report ultrastructural and cell biological analyses of regeneration processes after SCI. We have focused on event specific analyses of spinal cord regeneration involving different neuronal and glial cell progenitors, such as radial glia, oligodendrocyte progenitors (OPC), and Schwann cells. While comparing the different events, we frequently refer to previous ultrastructural analyses of central nervous system (CNS) injury in higher vertebrates. Our data show (a) the cellular events following injury, such as cell death and proliferation; (b) demyelination and remyelination followed by target innervation and regeneration of synaptic junctions and...
In the present review we discuss two interrelated events-axonal damage and repair-known to occur ... more In the present review we discuss two interrelated events-axonal damage and repair-known to occur after spinal cord injury (SCI) in the zebrafish. Adult zebrafish are capable of regenerating axonal tracts and can restore full functionality after SCI. Unlike fish, axon regeneration in the adult mammalian central nervous system is extremely limited. As a consequence of an injury there is very little repair of disengaged axons and therefore functional deficit persists after SCI in adult mammals. In contrast, peripheral nervous system axons readily regenerate following injury and hence allow functional recovery both in mammals and fish. A better mechanistic understanding of these three scenarios could provide a more comprehensive insight into the success or failure of axonal regeneration after SCI. This review summarizes the present understanding of the cellular and molecular basis of axonal regeneration, in both the peripheral nervous system and the central nervous system, and large sca...
Spinal cord injury (SCI) in mammals leads to failure of both sensory and motor functions, due to ... more Spinal cord injury (SCI) in mammals leads to failure of both sensory and motor functions, due to lack of axonal regrowth below the level of injury as well as inability to replace lost neural cells and to stimulate neurogenesis. In contrast, fish and amphibians are capable of regenerating a variety of their organs like limb/fin, jaw, heart and various parts of the central nervous system (CNS). Zebrafish embryo and adult has become a very popular model to study developmental biology, cell biology and regeneration for various reasons. Adult zebrafish, one of the most important vertebrate models to study regeneration, can regenerate many of their body parts like fin, jaw, heart and CNS. In the present article we provide information on how to inflict different injury modalities in adult fish spinal cord. Presently, the significant focus of mammalian SCI is to use crush and contusion injury. To generate an entity comparable to the mammalian mode of injury, we have introduced the crush model in adult zebrafish along with complete transection injury, which is also known to be a valuable model to study axonal regeneration. Here we provide full description of the highly reproducible surgical procedures including some representative results. This protocol has been adapted from our previous publications, viz. Hui et al., 2010 and Hui et al., 2014. Briefly, we have described the two different injury modalities, crush and complete transection, and demonstrated the outcome of inflicting these injuries in the adult zebrafish cord by histological analysis of the tissues.
Regeneration in the animal kingdom is one of the most fascinating problems that have allowed scie... more Regeneration in the animal kingdom is one of the most fascinating problems that have allowed scientists to address many issues of fundamental importance in basic biology. However, we came to know that the regenerative capability may vary across different species. Among vertebrates, fish and amphibians are capable of regenerating a variety of complex organs through epimorphosis. Zebrafish is an excellent animal model, which can repair several organs like damaged retina, severed spinal cord, injured brain and heart, and amputated fins. The focus of the present paper is on spinal cord regeneration in adult zebrafish. We intend to discuss our current understanding of the cellular and molecular mechanism(s) that allows formation of proliferating progenitors and controls neurogenesis, which involve changes in epigenetic and transcription programs. Unlike mammals, zebrafish retains radial glia, a nonneuronal cell type in their adult central nervous system. Injury induced proliferation invo...
Zebrafish can repair their injured brain and spinal cord after injury unlike adult mammalian cent... more Zebrafish can repair their injured brain and spinal cord after injury unlike adult mammalian central nervous system. Any injury to zebrafish spinal cord would lead to increased proliferation and neurogenesis. There are presences of proliferating progenitors from which both neuronal and glial loss can be reversed by appropriately generating new neurons and glia. We have demonstrated the presence of multiple progenitors, which are different types of proliferating populations like Sox2 + neural progenitor, A2B5 + astrocyte/ glial progenitor, NG2 + oligodendrocyte progenitor, radial glia and Schwann cell like progenitor. We analyzed the expression levels of two common markers of dedifferentiation like msx-b and vimentin during regeneration along with some of the pluripotency associated factors to explore the possible role of these two processes. Among the several key factors related to pluripotency, pou5f1 and sox2 are upregulated during regeneration and associated with activation of neural progenitor cells. Uncovering the molecular mechanism for endogenous regeneration of adult zebrafish spinal cord would give us more clues on important targets for future therapeutic approach in mammalian spinal cord repair and regeneration.
Journal of muscle research and cell motility, 1998
To analyse the myogenic cell lineages in human foetal skeletal muscle, muscle cell cultures were ... more To analyse the myogenic cell lineages in human foetal skeletal muscle, muscle cell cultures were prepared from different foetal stages of development. The in vitro muscle cell phenotype was defined by staining the myotubes with antibodies to fast and slow skeletal muscle type myosin heavy chains using immunoperoxidase or double immunofluorescence procedures. The antibodies to fast skeletal muscle myosin heavy chains stained nearly all myotubes dark in cell cultures prepared from quadriceps muscles at 10-18 weeks of gestation. The antibodies to slow skeletal muscle myosin heavy chains, in contrast, stained only 10-40% of the myotubes very dark. The remaining myotubes were further subdivided into two populations, one of which was unstained while the other stained with variable intensity for slow myosin heavy chain. The slow myosin heavy chain staining was not influenced by the nature of the substratum used to culture these cells, although the growth of muscle cell cultures was greatly...
The International journal of developmental biology, 1994
The regenerating amphibian jaw represents an important model for studying pattern formation and t... more The regenerating amphibian jaw represents an important model for studying pattern formation and the mechanisms underlying regeneration of facial structures. We have studied regeneration of upper and lower jaws in the urodele amphibian, Notophthalmus viridescens, using whole mount preparations stained for bone and cartilage, scanning electron microscopy and immunocytochemistry to further characterize these regenerating systems. In addition, we have investigated whether lower jaws of adults and larvae display similar regenerative ability. Although in adult animals the original shape of both the lower and upper jaws is rather faithfully reproduced following amputation, and the teeth and oral mucosa with its specialized sensory organs fully regenerate, significant differences in the regenerative ability of the various skeletal elements are observed. In fact, only tooth-bearing skeletal elements ossify, while the other elements of the regenerated skeleton remain cartilaginous for as long...
The International journal of developmental biology, 1996
The vitamin A derivative retinoic acid (RA) is a powerful teratogen which can induce severe crani... more The vitamin A derivative retinoic acid (RA) is a powerful teratogen which can induce severe craniofacial and limb malformations if administered at certain stages of gestation. In addition this compound has been shown to affect patterning in regenerating systems. A classical example is the induction of supernumerary structures along the proximodistal axis of the regenerating amphibian limb. We have investigated the effect of RA on other regenerating systems, the amphibian lower and upper jaws, both in developing and adult animals. We report here that RA does not induce formation of extra structures either in the lower or in the upper jaw of adult newts under experimental conditions where duplications of the regenerating limb occur. However, RA selectively induces severe malformations in the upper jaw regenerate that resemble those induced in avian and mammalian embryos. Analysis of the expression of the newt retinoic acid receptors RAR alpha and delta in upper and lower jaws showed t...
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Papers by Sukla Ghosh