Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.27 (AMPK)
 6,299 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Testicular cells composed mostly of germ cells and immature Sertoli cells from neonatal mice 2 and 5 days old were cultured to investigate germ-cell proliferation mediated by the c-kit receptor. The addition of antibody to block the interaction of the c-kit receptor with its ligand inhibited the proliferation of cultured spermatogonia from 5-day-old mice in a dose-dependent manner, but not from that of 2-day-old mice. The addition of anti-c-kit ACK2 monoclonal antibody also inhibited the proliferation of spermatogonia from 5-day-old mutant Sld/Sld mice but not of 5-day-old mutant Wv/Wv mice. The results indicate that c-kit-positive type A spermatogonia in the testes of 5-day-old mice require steel factor (kit ligand) for their proliferation, whereas self-renewal and differentiation of c-kit-negative primitive type A spermatogonia in the testes of 2-day-old mice do not.
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PMID:Switching of mouse spermatogonial proliferation from the c-kit receptor-independent type to the receptor-dependent type during differentiation. 752 77

In vivo injection of a neutralizing, monoclonal antibody (ACK2) to the receptor tyrosine kinase (c-kit) disrupts the normal motility patterns of the mouse small intestine. Immunohistochemical studies showed that cells expressing c-kit-like immunoreactivity (c-kit-LI) decreased in numbers in response to ACK2, but the identity of these cells is unknown. We investigated the identity and development of the cells that express c-kit-LI in the mouse small intestine and colon. Cells in the region of the myenteric plexus and deep muscular plexus of the small intestine and in the subserosa, in the myenteric plexus region, within the circular and longitudinal muscle layers, and along the submucosal surface of the circular muscle in the colon were labeled with ACK2. The distribution of cells that express c-kit-LI was the same as that of interstitial cells (ICs). In whole-mount preparations cells with c-kit-LI were interconnected, forming a network similar to the network formed by cells that stained with methylene blue, which has been used as a marker for ICs in the mouse gastrointestinal tract. Immunocytochemistry verified that ICs were labeled with ACK2. Multiple injections of animals with ACK2 between days 0 and 8 post partum (pp) caused a dramatic reduction in the number of ICs compared to control animals. From an ultrastructural point of view, the proliferation and development appeared to be suppressed in some classes of ICs, while others displayed an altered course of development. Functional studies showed that the decrease in ICs was accompanied by a loss of electrical rhythmicity in the small intestine and reduced neural responses in the small bowel and colon. Morphological experiments showed that c-kit-positive cells are ICs, and physiological evidence reinforced the concept that ICs are involved in generation of rhythmicity and translation of neural inputs in gastrointestinal smooth muscles. Controlling the development of ICs provides a powerful new tool for the investigation of the physiological role of these cells.
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PMID:c-kit-dependent development of interstitial cells and electrical activity in the murine gastrointestinal tract. 753 51

Studies of mice containing mutations in the genes for a receptor tyrosine kinase, c-kit, or its cognate ligand, Steel factor (SLF), establish that this signaling pathway is required for the development of melanocytes from their precursors in the embryonic neural crest (NC). In order to define the mechanism of this requirement, we have labeled cells expressing c-kit with an anti-c-kit antibody (ACK2) and studied the action of SLF on these cells in cultures of murine trunk NC. c-kit positive (c-kit+) cells first appeared after 2 days in culture and were morphologically indistinguishable from other NC cells. These cells subsequently expressed tyrosinase-related protein, an early marker for the melanocyte lineage, and became pigmented in the presence of a phorbol ester. Further, elimination of the c-kit+ population, by incubating the cultures in ACK2, resulted in the ablation of the melanocyte population, but had no effect on the generation of other neural crest derivatives. These data indicate that c-kit+ cells arising from the neural crest are melanocyte progenitors. The addition of SLF to these cultures stimulated an increase in the number of c-kit+ cells, and further studies indicated that SLF acts as both a survival and a proliferative factor for c-kit+ cells. These findings provide a mechanism of regulation of melanocyte development, whereby c-kit is exclusively expressed by melanocyte progenitors within the neural crest precursor population, and subsequent survival and proliferation of these progenitors is regulated by SLF.
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PMID:Steel factor directs melanocyte development in vitro through selective regulation of the number of c-kit+ progenitors. 754 Jan 55

Previous studies indicate that c-Kit is required for postnatal melanocyte development. To understand the precise mechanisms of c-Kit dependence, we studied melanocyte development in newborn C57BL/6 mice by means of peritoneal injection of a monoclonal anti-c-Kit antibody (ACK2), which blocks c-Kit functions. The mice were injected once or more with ACK2 at various intervals after birth. In experiment 1, skin samples were examined on day 10 post-partum and in experiment 2 they were examined daily until day 10 post-partum. We studied melanocytes in the hair follicles, epidermis, and dermis by light and electron microscopy with dopa reactions and immunohistochemistry. Epidermal melanocytes in untreated mice were dopa negative and c-Kit positive on day 0 post-partum but became dopa positive soon thereafter. In ACK2-treated mice, the earlier the mice received ACK2 injections after birth, the fewer melanocytes they had, not only in the epidermis, but also in follicles. In these mice, melanocytes that had undergone apoptosis in the dermis and the follicles were detected ultrastructurally. Some appeared to have produced tyrosinase, because they had dopa-positive melanosomes. These results suggest that melanocytes in newborn mice are c-Kit dependent and undergo apoptosis when c-Kit receptors are blocked by ACK2 in the early days after birth. During this c-Kit-dependent period, melanocytes differentiate from dopa negative to positive and migrate from the epidermis to hair follicles.
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PMID:Effects of monoclonal anti-c-kit antibody (ACK2) on melanocytes in newborn mice. 754 1

The monoclonal rat anti-c-kit antibody (ACK2), which abrogates colony growth supported by stem cell factor (SCF), significantly inhibited the interleukin-6 (IL-6)-dependent growth of hematopoietic progenitors derived from spleen cells of normal and 5-fluorouracil (5-FU)-treated mice and from bone marrow cells of normal mice in serum-containing culture. The numbers and types of colonies supported by IL-3, granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF), however, were not influenced by the addition of ACK2 to the cultures of the bone marrow cells from normal mice. In replating experiments with pooled blast cells, ACK2 caused a partial, but significant, inhibition of GM colony growth supported by a combination of IL-6 and fetal bovine serum (FBS), which suggests that FBS is one source of the SCF activity. Conversely, the addition of SCF or FBS with IL-6 to a serum-free culture had significant synergistic effects on the total number of colonies derived from post-5-FU spleen cells and from pooled blast cells. The dose response study showed that the ability of 30% FBS to interact with IL-6 on the colony growth by post-5-FU spleen cells was equivalent to that of approximately 5 ng/mL SCF. These findings suggest that c-kit plays an important role in the growth of hematopoietic progenitors responding to IL-6, and that SCF in the serum affects the development of hematopoietic progenitors in serum-containing cultures.
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PMID:Possible role of stem cell factor as a serum factor: monoclonal anti-c-kit antibody abrogates interleukin-6-dependent colony growth in serum-containing culture. 768 4

The protooncogene c-kit encodes a receptor type tyrosine kinase and is allelic with the W locus of mice. SLF, the c-Kit ligand which is encoded by the Sl locus, has growth promoting activity for hemopoietic stem cells. Previous studies demonstrated that c-Kit is functionally required for the proliferation of hemopoietic progenitor cells at various differentiation stages in adult bone marrow. However, the absence of functional SLF and c-Kit in fetuses with mutant alleles of Sl and W loci produces only minor effects on the myeloid and early erythroid progenitor cells in the fetal liver, although the level of the late erythroid progenitor cells is significantly affected. We used an anti-c-Kit monoclonal antibody to investigate the expression and function of c-Kit in murine fetal hemopoietic progenitor cells. Flow-cytometric analysis showed that hemopoiesis in the yolk sac and fetal liver started from cells that express c-Kit. The c-Kit expression decreased upon maturation into erythrocytes in each organ. By fluorescence activated cell sorting, the c-Kit+ cell population was enriched with the hemopoietic progenitor cells clonable in vitro (CFU-E, BFU-E and GM-CFC). To elucidate whether c-Kit functions in these progenitor cells in vivo, we took advantage of the antagonistic anti-c-Kit monoclonal antibody, ACK2, which can block the function of c-Kit. Administration of ACK2 after 12.5 days of gestation rapidly eliminated BFU-E and GM-CFC as well as CFU-E from the fetal liver. However, the number of these progenitor cells in the yolk sac and fetal liver was less affected when the fetuses were given ACK2 before 12.5 days of gestation. Our results provide evidence that there are two waves of hemopoiesis in murine embryos relative to c-Kit dependency. The c-Kit has an essential role on the growth of hemopoietic progenitor cells in the fetal liver after 12.5 days of gestation, whereas the progenitor cells in the liver and yolk sac of the earlier embryo do not depend on c-Kit and its ligand SLF.
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PMID:Expression and function of c-Kit in fetal hemopoietic progenitor cells: transition from the early c-Kit-independent to the late c-Kit-dependent wave of hemopoiesis in the murine embryo. 768 45

In the mouse testis, spontaneous death of spermatogonia has a large impact on the output of differentiating spermatids. The tyrosine kinase receptor c-kit is expressed in type A, intermediate, and B spermatogonia, and kit-ligand (KL) is expressed in Sertoli cells. Previous work indicated a depletion of type A spermatogonia after in vivo exposure to an antibody that blocks c-kit function. The present work was undertaken to determine whether blocking c-kit function results in apoptosis of spermatogonia or in an inability of spermatogonia to proliferate. Testes sections were stained by a method that detects apoptotic cells in situ. In testes of 8-day postnatal (P8) males, type A spermatogonia are the predominant germ cell type present. Stained sections from P8 males injected with the c-kit antagonistic antibody ACK2 showed a fivefold higher rate of cell death than uninjected controls. At least a twofold increase was observed in P12 and P30 injected males and in P30 SId/+ males as compared to uninjected controls. Determination of the stage of germ cell development that was affected in P30 males indicated that the frequency of gonial cell death was increased fourfold, but the frequency of death in spermatocytes around the time of the meiotic division was increased 15-fold. It is concluded that KL acts to prevent apoptosis in the testis in vivo, that the membrane bound form of KL may be more effective, and that survival of late meiotic and dividing spermatocytes is regulated by KL through an indirect mechanism probably mediated by Sertoli cells. Thus, KL is an important regulator of spermatid output.
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PMID:Kit ligand mediates survival of type A spermatogonia and dividing spermatocytes in postnatal mouse testes. 857 44

The injection of an antagonistic anti-murine c-kit monoclonal antibody ACK2 during mouse embryonic development produced three distinctive pigmentation patterns on the coat of the offspring. Pattern 1 consisted of pigmentation in craniofacial and caudal regions and was induced by an ACK2 injection between 9.5 and 11.5 days post coitum (dpc). In pattern 2, the entire coat was unpigmented and was induced by the injection at around 13.0 dpc. Pattern 3 consisted of pigmented patches spreading ventrolaterally from the dorsoanterior trunk regions towards the anterior and posterior directions and it was induced by ACK2 administered at 14.5-15.0 dpc. We investigated the embryological basis of these nonuniform pigmentation patterns to elucidate the process of melanoblast differentiation between lineage commitment and colonization into developing hair follicles. The results showed the following. (1) Melanocyte differentiation at the embryonic stage from 10.5 to 12.5 dpc progresses in a spatially nonuniform fashion, being faster in the craniofacial and caudal regions than in the trunk; pattern 1 reflects this. (2) Melanoblasts are activated to proliferate synchronously upon entering into the epidermis; pattern 2 correlates with this process. (3) c-kit functions as a survival signal for proliferating melanoblasts in the epidermis. (4) The melanoblasts that enter developing hair follicles can survive without a c-kit signal; pattern 3 essentially represents the hair follicles colonized by these cells. Analysis of the melanoblast distribution of ls/ls embryos that bear a loss-of-function mutation in the endothelin 3 gene suggested that endothelin 3 is required for early melanoblast differentiation before entering into the epidermis, whereas proliferation in the epidermis takes place without this molecule. Based on these data, we propose 4 distinct steps of embryonic melanocyte differentiation: (1) migration in the dermis, which requires both c-kit and endothelin 3; (2) a state before epidermal entry that is resistant to anti-c-kit mAb; (3) cell proliferation after entering the epidermal layer, which requires c-kit and endothelin receptor B but not endothelin 3 and (4) integration into developing hair follicles, which renders melanoblasts resistant to anti-c-kit mAb. Thus, melanoblast differentiation proceeds by alternately repeating c-kit -dependent and c-kit-independent stages and c-kit functions as a survival factor for the proliferating melanoblasts.
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PMID:Distinct stages of melanocyte differentiation revealed by anlaysis of nonuniform pigmentation patterns. 862 Aug 47

The phenotypes of mice that harbor a defect in the genes encoding either stem cell factor (SCF) or its receptor, c-kit, indicate that this ligand/receptor pair is necessary for maintenance of normal hematopoiesis in the adult. Our objective was to determine whether SCF, like erythropoietin, is necessary for acute erythroid expansion during recovery from hemolytic anemia. Monoclonal antibody ACK2, which recognizes the murine c-kit receptor, was used to selectively block the hematopoietic growth-promoting effects of SCF. Mice were treated with phenylhydrazine on day 0 and day 1 to induce hemolytic anemia and also received no antibody, control IgG, or ACK2 on day 0. The mice were killed on day 3 and the hematocrit (Hct), reticulocyte count, and numbers of erythroid and myeloid hematopoietic progenitor cells (colony-forming unit-erythroid [CFU-E], burst-forming unit [BFU]-E, and CFU-granulocyte-macrophage [GM]) were quantitated in the femoral marrow and spleen using hematopoietic colony-forming assays. Induction of hemolytic anemia with phenylhydrazine resulted in a drop in the Hct from approximately 50% to 30%, and an approximate 8- to 10-fold increase in the reticulocyte count. The numbers of CFU-E increased modestly in the femur, and approximately 25- to 50-fold in the spleen, in comparison with normal mice. BFU-E and CFU-GM values did not increase in the femur but expanded 6- to 10-fold in the spleen, in comparison with normal mice. This confirms that much of the erythroid expansion in response to hemolytic anemia occurs in the murine spleen. Neutralizing quantities of the ACK2 antibody reduced femoral CFU-E, BFU-E, and CFU-GM content to less than half that found in phenylhydrazine-treated control mice and nearly totally ablated splenic hematopoiesis. These results suggest that c-kit receptor function may be required for optimal response to acute erythropoietic demand and that erythropoiesis in the splenic microenvironment is more dependent on SCF/c-kit receptor interaction than is erythropoiesis in the marrow microenvironment. Because expansion of late erythropoiesis in the spleen was preferentially blocked, we tested the hypothesis that homing of more primitive hematopoietic cells to the spleen was dependent on c-kit receptor function. Lethally irradiated mice were injected with marrow cells obtained from mice that had received phenylhydrazine plus control IgG or with marrow cells obtained from mice that had received phenylhydrazine plus ACK2. In parallel experiments, normal murine marrow cells were treated in vitro with control IgG or with ACK2 and were injected into lethally irradiated mice. The fraction of BFU-E and CFU-GM retrieved from the marrow and spleen of the recipient mice 4 hours later was reduced by approximately 75% when progenitor cells had been exposed to ACK2, in comparison with control IgG. These data suggest that interaction of SCF with the c-kit receptor affects the homing behavior of hematopoietic progenitor cells in the adult animal.
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PMID:Interaction of stem cell factor and its receptor c-kit mediates lodgment and acute expansion of hematopoietic cells in the murine spleen. 870 4

Chronic injection of an anti-c-KIT receptor tyrosine kinase monoclonal antibody (ACK2) results in the disruption of the normal motility patterns of young BALB/c mice intestine. This effect is accompanied by a drastic decrease in the number of intestinal c-kit-expressing (c-kit+) cells when studied immunohistochemically with the fluorescence-labelled antibody. In order to clarify the mechanism underlying the ACK2 action and the physiological roles of intestinal c-kit+ cells, we studied the excitability of intestinal c-kit+ cells in primary culture by use of the nystatin perforated-patch-clamp technique. Under voltage-clamp at -40 mV, the majority of c-kit+ cells tested (59/70) elicited rhythmic current waves with an amplitude and frequency of 263 +/- 24 pA and 2.30 +/- 0.25 cycles/min (mean +/- SEM), respectively. Intracellular perfusion of the c-kit+ cells with ethylenebis (okonitrilo) tetraacetate (EGTA) as well as a nominally Ca(2+)-free external solution or low holding voltage (< -60 mV) prevented the rhythmic current. The reversal potential of the rhythmic current was close to the equilibrium potential for Cl-(ECl). Moreover the rhythmic current was depressed by a Cl- channel blocker, 4-acetoamido-4-isothiocyanat-ostilbene-2,2'-disulphoni c acid (SITS). The smooth muscle cells freshly dissociated from the same intestinal specimen revealed a Ca(2+)-activated K+ current, as has been described in a variety of smooth muscle cells. Cultured smooth muscle cells from the ileum preparation lacked neither the Ca(2+)-activated K+ nor rhythmic Cl- currents. Smooth muscle cells freshly dissociated from the same ileum preparation and those in culture showed no immunoreactivity with the labelled ACK2, which was consistent with our previous in situ study. Results provided direct evidence that the intestinal c-kit+ cells, but not the smooth muscle cells, possess a rhythmic Cl- current oscillation, suggesting their participation in pacemaker activity for the peristaltic gut movement.
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PMID:Rhythmic Cl- current and physiological roles of the intestinal c-kit-positive cells. 902 76


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