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PubMed2003

Expression of BDNF and TrkB in mouse taste buds after denervation and in circumvallate papillae during development.

BDNF (brain-derived neurotrophic factor) is a member of the neurotrophin family which affects the proliferation and survival of neurons. Using an immunocytochemical method, we examined the expression of BDNF and its receptor, TrkB, in the taste bud cells of the circumvallate papillae of normal mice and of mice after transection of the glossopharyngeal nerves. We additionally observed the expression of BDNF and TrkB in the developing circumvallate papillae of late prenatal and early postnatal mice. In normal untreated mice, BDNF was expressed in most of the taste bud cells; TrkB was detected in the plasma membrane of taste bud cells and in the nerve fibers. Double-labeling studies showed that BDNF and NCAM (neural cell adhesion molecule) or TrkB and NCAM colocalized in some of the taste bud cells, but that most taste bud cells were immunopositive for only BDNF or TrkB. NCAM-immunoreactive cells are known to be type-III cells, which have afferent synaptic contacts with the nerve terminals. Five days after denervation, the number of taste buds and nerve fibers markedly decreased; however, the remaining taste bud cells still expressed BDNF and TrkB. By 10 days after denervation, most of the taste buds had disappeared, and there were a few TrkB-immunoreactive nerve fibers in the connective tissue core. By 4 weeks after denervation, numerous TrkB-immunoreactive nerve fibers had invaded the papillae, and a few taste buds expressing BDNF and TrkB had regenerated. At E (embryonic day) 15 during development, the circumvallate papillae appeared, and then TrkB-immunoreactive nerve fibers entered the connective tissue core, and some of these fibers further invaded among the dorsal epithelial cells of the papillae. TrkB-immunoreactive oval-shaped cells were occasionally found in the dorsal epithelium. Such TrkB-immunoreactive nerve fibers and cells were also observed at E16-18. However, BDNF was not expressed in the papillae through the late prenatal days of E15 to E18. At P (postnatal day) 0, a cluster of BDNF-and TrkB-immunoreactive cells appeared in the dorsal epithelium of the papillae, and was presumed to be primitive taste buds. We conclude that TrkB-immunoreactive nerve fibers are necessary for papillary and taste bud formation during development and for the regeneration of taste buds after denervation. BDNF in the taste bud cells may act as a neurotrophic factor for innervating sensory neurons--through TrkB receptors of the axons of those neurons, and also may exert autocrine and paracrine trophic actions on neighboring taste bud cells by binding to their TrkB receptors.

Animals↗

PubMed1987

A sensitive period for the neural induction of taste buds.

Taste buds mature postnatally in the vallate papilla of the rat and reach a mean number of 610 by day 90. Although taste buds are neurotrophically dependent, the presence of widespread bilateral innervation permits more than 80% of the 610 vallate taste buds to survive after one IXth nerve is removed in adults. However, after a IXth nerve is removed at 0-3 d postpartum, about two-thirds of the vallate taste buds fail to develop. In the present investigation, the timing of the neural induction of taste buds was examined by unilaterally removing the IXth nerve at 12 different postnatal ages, from 0 to 75 d. Unilateral denervation revealed the existence of a sensitive period that is maximal from 0 to 10 d, when unilateral or bilateral interruption of the IXth nerve profoundly impairs the formation of taste buds. The number of taste buds that form is nonlinearly dependent upon the number of axons; at low levels of innervation, a doubling of the number of myelinated axons quintuples the number of taste buds. Thus, taste axons interact synergistically. In studying regeneration, we found that axons of both neonatal and adult IXth nerves elongate approximately 1.8 mm/d. Taste buds were re-formed more rapidly and a higher proportion were bilaterally innervated when regenerating axons and the sites of former taste buds were numerous. The proportion of bilaterally innervated taste buds could be approximated from the likelihood of random overlap of axons from the right and left IXth nerves. The greater ease with which taste buds are re-formed than developed suggests that taste bud regeneration does not recapitulate taste bud development.

Animals↗

PubMed2001

Role of ATP in influenza virus budding.

Influenza viruses bud from the plasma membrane of virus-infected cells. Although budding is a critical step in virus replication, little is known about the requirements of the budding process. In this report, we have investigated the role of ATP in influenza virus budding by treating influenza virus infected Madin-Darby canine kidney (MDCK) cells with a number of metabolic inhibitors. When WSN virus-infected MDCK cells were exposed to antimycin A, carbonyl cyanide m-chlorophenylhydrazone, carbonyl cyanide p-trifluoromethoxy-phenylhydrazone, or oligomycin for a short time (15 min or 1 h) late in the infectious cycle, the rate of virus budding decreased. This inhibitory effect was reversible upon removal of the inhibitors. The role of ATP hydrolysis was analyzed by treating lysophosphatidylcholine (LPC)-permeabilized live filter-grown virus-infected MDCK cells with nonpermeable ATP analogues from the basal side and assaying virus budding from the apical side. In LPC-permeabilized cells, membrane-impermeable ATP analogues such as adenosine 5'-O-(3-thiotriphosphate) or 5'-adenylylimidodiphosphate caused reduction of virus budding which could be partially restored by adding excess ATP. These data demonstrated that ATP hydrolysis and not just ATP binding was required for virus budding. However, inhibitors of ion channel (ATPases) and protein ubiquitinylation, which also required the ATP as energy source, did not affect influenza virus budding, suggesting that neither ion channel nor protein ubiquitinylation activity was involved in influenza virus budding. On the other hand, treatment with dimethyl sulfoxide (DMSO), which decreases membrane viscosity, reduced the rate of virus budding, demonstrating that the physical state of membrane viscosity and membrane fluidity had an important effect on virus budding. Data presented in the report indicate that influenza virus budding is an active ATP-dependent process and suggest that reduced virus budding by ATP depletion and DMSO treatment may be partly due to decreased membrane viscosity.

Acetylcysteine↗

PubMed1984

Morphogenetic tissue interactions during posterior commitment in palleal buds of the polystyelid ascidian, Polyandrocarpa misakiensis.

The development of chimeric double-anterior and double-posterior buds in the polystyelid ascidian, Polyandrocarpa misakiensis, was studied. Bud pieces used were allowed to develop for various time periods before the fusion operation. One-day double-half buds developed into complete zooids with normal anteroposterior polarity. In these cases, the bud half whose site of origin on the parent was higher (more posterior) than the partner formed the posterior organ, the digestive tract, of a resultant zooid. Two-day double-posterior buds developed into biposterior zooids that had two digestive tracts, whereas 2-day double-anterior buds still underwent pattern regulation in the same manner as 1-day buds (23-24 degrees C). Bianterior zooids could only be induced from 3-day double-anterior buds, suggesting that the anterior determination occurs later than the posterior determination. Next, a 3-day posterior half was combined with a 1-day posterior half from a higher site. Though "high-level" tissue has a high potential for posterior differentiation, the 1-day bud half failed to form the digestive tract. This result suggests that the 3-day bud half has acquired the ability to inhibit the formation of additional posterior structures. The kinetics of posterior-forming activity of developing bud pieces was measured using a 12-hr bud piece of the highest level as a probe. The activity increased with increasing developmental time, and the increase was accompanied by posterior inhibition activity. Buds of different positional levels showed different time courses of these activities. The results of this study show that the posterior end is the dominant region of developing ascidian buds.

Animals↗

PubMed2006

Terminal bud failure of black cottonwood (Populus trichocarpa) exposed to salt-laden winter storms.

At coastal sites, trees are exposed to marine aerosols that may cause foliar necrosis and shoot dieback, which can result in deformed crowns and contorted stems. A six-year study of leaf primordia in terminal buds of black cottonwood trees (Populus trichocarpa Torr. & Gray) on Heimaey Island off the south coast of Iceland was undertaken to elucidate the physiological events associated with salt-deposition-related bud failure. Leaf and bud lengths, dry mass, water content and chloride concentrations were monitored and related to four phenological stages: (1) bud set; (2) dormancy induction; (3) dormancy release; and (4) bud break. The trees set buds in July and shed their leaves by late September. Leaf primordia generally stopped growing by September 10 +/- 22 days and attained midwinter water content in late September. Leaf growth commenced in the terminal buds by March 2 +/- 16 days, but mean dates of bud swelling and bud break were April 29 +/- 19 and May 10 +/- 12 days. In summer and until November, chloride concentrations in leaf primordia were low, but increasing. Chloride concentrations remained stable from December to February, even though the dormant trees were exposed to large amounts of marine aerosols. In February and March, three events occurred more or less simultaneously: (1) leaf extension growth commenced; (2) chloride concentration surged in the leaf primordia; and (3) the leaf primordia began to hydrate. Following dormancy release, growth and hydration of leaf primordia were negatively related to chloride concentration in the leaf primordia, with inhibition of leaf growth, tissue hydration and chloride acquisition occurring at a chloride concentration threshold estimated at 7.3 mg Cl- g(-1) tissue water. Necrosis of leaf primordia was observed above 14 mg Cl- g(-1) tissue water. Growth and hydration of leaves at bud break in mid-May was explained by a three-parameter logistic model of chloride concentration in leaf primordia at the end of March. By mid-May, 90% of all buds remained non-necrotic, but only 56% the terminal buds had broken. Salt alone explained the observed growth suppression of leaf primordia in the buds and the resultant failure of terminal buds to break by mid-May.

Geography↗

PubMed1996

Temporal and spatial patterns of tenascin and laminin immunoreactivity suggest roles for extracellular matrix in development of gustatory papillae and taste buds.

Gustatory papillae are complex organs that are composed of 1) an epithelium, 2) specialized sensory cells within the epithelium (the taste buds), 3) a broad connective core, and 4) sensory innervation. During papilla development, cells in the various tissue compartments must divide, aggregate, detach, migrate, and reaggregate in relation to each other, but factors that regulate such steps are poorly understood and have not been extensively studied. All of these processes potentially require participation of the extracellular matrix. Therefore, we have studied temporal and spatial patterns of immunoreactivity for two extracellular matrix molecules, tenascin and laminin, in the developing fungiform and circumvallate papillae of fetal, perinatal, and adult sheep tongue. To determine relations of tenascin and laminin to sensory innervation, we used an antibody to growth-associated protein (GAP-43) to label growing nerves. Immunocytochemical distributions of tenascin and laminin alter during development in a manner that reflects morphogenesis rather than histologic boundaries of the taste papillae. In early fungiform papillae, tenascin immunoreactivity is very weak within the mesenchyme of the papilla core. However, there is a subsequent shift to an intense, restricted localization in the apical papilla core only--directly under taste bud-bearing regions of the papilla epithelium. In early circumvallate papillae, tenascin immunoreactivity is patchy within the papilla core and within the flanking, nongustatory papillae. Later, immunoreactivity is restricted to the perimeter of the central papilla core, under epithelium that contains developing taste buds. In fungiform and circumvallate papillae, the shift in tenascin immunolocalization is associated with periods of taste bud formation and multiplication within the papilla epithelium and with extensive branching of the sensory innervation in the papilla apex. Laminin immunoreactivity, although it is continuous throughout the basement membrane of general lingual epithelium, is interrupted in the epithelial basement membrane of early fungiform and circumvallate papillae in regions where taste buds are forming. The breaks are large in young fetuses, when taste buds first develop, and are evidenced later as punctate disruptions. Heparan sulfate proteoglycan immunoreactivity confirms that these are basement membrane discontinuities. GAP-43 label coincides with innervation of the papilla core and is most extensive in regions where tenascin immunoreactivity is weak or absent. GAP-43 immunoreactivity is also found in early taste buds: Later, it is extensive within more mature multiple taste buds, presumably in relation to synaptogenesis. We propose that tenascin has a role in promoting deadhesion of cells in the papilla epithelium during periods of taste bud formation and multiplication. Discontinuities in the epithelial basement membrane under developing taste buds, indicated with laminin and heparan sulfate proteoglycan immunoreactivity, may interact to facilitate taste bud morphogenesis and multiplication, to permit access of papilla innervation to the forming taste buds, and/or to allow epithelial/mesenchymal interactions during papilla and taste bud development.

Animals↗

PubMed1987

Taste bud development in chickens (Gallus gallus domesticus).

Oral epithelium in the anterior mandibular glands region was examined in embryonic, hatchling, and mature chickens to establish the timing of morphologic events during taste bud ontogeny. Hematoxylin-and-eosin-stained sections (10 microns) from 27 Anak (broiler breed) chickens were examined serially, and buds were quantified at 16-20 days of incubation (E) and, posthatch days 1 and 50-60. Taste buds were first recognized at the beginning of E17 as small clusters of cells in the basal epithelium. Only spherical-shaped buds were observed on E17 and E18, and these spherical clusters never penetrated to the surface of the stratified epithelial layer. E19 marked a transitional stage when mature bud features began to emerge: the buds assumed a more elongate shape, several kinds of cells comprising the bud were distinguishable and the first taste pores were observed. During the ensuing embryonic days, buds continued to elongate commensurate with the deepening oral epithelium and by hatching virtually all buds opened to the oral cavity. No marked morphological changes in taste bud structure were observed on the day of hatching and at 50-60 days posthatching. Taste bud numbers increased dramatically during E17 and E18, peaked on E19, and remained relatively constant thereafter. It is concluded that the morphological sequence of taste bud development in chickens is similar to that in mammals. The timing of bud ontogeny, though initiated only during the third trimester in ovo, essentially is completed by hatching, thus providing the precocial hatchling with the sensory apparatus essential for gustatory experience.

Age Factors↗

PubMed2001

Ultrastructure of the taste buds in the blind cave fish Astyanax jordani ("Anoptichthys") and the sighted river fish Astyanax mexicanus (Teleostei, Characidae).

This study describes the ultrastructure of the taste buds of the sighted river fish Astyanax mexicanus and of the blind cave fish Astyanax jordani (= Anoptichthys) (Teleostei, Characiformes, Characidae). In Astyanax and Anoptichthys, taste buds occur in the epithelia of the lips, oral cavity, and, in Anoptichthys, lower jaw. Both possess three types of taste buds: type I (elevated), type II (slightly elevated), and type III taste buds (not elevated or sunken). The taste buds are up to 60 microm high and up to 35 microm wide. The taste bud's sensory epithelium consists of 100--130 elongated cells: light cells, dense-cored-vesicles (dcv) -cells, dark cells, and degenerating cells. The dcv-cells are rich in dense-cored vesicles and are described for the first time in a teleostean taste bud. At the taste bud's base, there lie two to three basal cells. The basal cells of type I and type II taste buds have microvillus (spine)-like processes, in contrast to those of type III taste buds. The taste bud's nerve fiber plexus is situated between the bases of the elongated taste bud cells and the basal cells. Afferent synapses occur between dcv-cells and basal cells (presynaptic sides) and axons (postsynaptic side). Indistinct synapses occur between light cells and dark cells (presynaptic sides) and axons (postsynaptic side). The nerve fiber plexes of Anoptichthys type II and type III taste buds contain significantly more axon profiles than those of Astyanax. This may be associated with a compensatory improvement of the sense of taste in the blind, cave-dwelling fish.

Animals↗

PubMed1987

Neural induction of taste buds.

Bilateral innervation allows more than 80% of the 610 vallate taste buds to survive removal of one IXth nerve in adult rats. Removal of both IXth nerves in neonatal or adult rats results in the absence of taste buds. In studying development, we found that removing or crushing one IXth nerve in three-day-old neonates profoundly decreased the number of vallate taste buds that subsequently developed. Specifically, after removal of one IXth nerve at 3 days, only 228 taste buds formed, compared with 496 taste buds that one nerve would maintain in adults. Thus, during normal development, the right and left IXth nerves interact synergistically, as at least 150 more taste buds develop than predicted by the sum of the independent action of each IXth nerve. This suggests that vallate taste buds are induced by the IXth nerve. A second example of synergism, representing evidence for the neural induction of taste buds, came from experiments in which we crushed the left IXth nerve 3 days after birth and found that these regenerated IXth nerve axons induced 4 times as many taste buds in the presence of the normal right IXth nerve (118 taste buds) as in its early absence (30 taste buds). We conclude that taste buds are neurally induced and that axons of the IXth nerve interact synergistically in inducing them, rather than competing for targets. We propose that in development innervated progenitor cells form stem cells which lead to taste bud cells.

Animals↗

PubMed1994

Ontogenesis and taste bud cell turnover in the chicken. I. Gemmal cell renewal in the hatchling.

Taste bud cell turnover rate was examined in oral epithelium of the precocial chick, which at hatching contains the adult complement of taste buds. Forty newly hatched chicks received single or double pulse injections of tritiated thymidine (specific activity was 6.7 Curies/millimole; dosage was 0.5 microCuries/g body weight, intraperitoneally). Anterior mandibular epithelium was processed for light microscopic autoradiography at 2 and 16 hours, as well as 1, 2, 3, 4, 6, 8, 10, 12, 14, 16, 18, and 20 days after the initial pulse. In a coded and randomized procedure, the section (7 microns) through the bud's center was selected for counting > or = 6 silver grains over round-clear and gracile-dense gemmal cell nuclei. The mean number of labelled cells/bud varied significantly (P < or = 0.01) during the first four posthatch days, yielding the fastest gemmal cell turnover rates (3.4-4.4 days) yet reported in vertebrates. Average bud diameter also significantly changed during the first four posthatch days, and was reflected in shifts of the distribution of 40-69 microns and > or = 70 microns diameter buds. Both an increase in labelled bud cells and bud diameter during the first two posthatch days may reflect high proliferation rates in initially maturing buds. Subsequent decrease in bud diameter between 2 and 3 days postinjection may indicate splitting of large-diameter (> or = 70 microns) buds and/or normal bud cell death due to failure of sensory afferentation. Bud-splitting alone, however, cannot account for significant decreases in bud cell label which did not occur before 4-6 days postinjection.

Animals↗

PubMed2001

Effects of zinc deficiency on the vallate papillae and taste buds in rats.

BACKGROUND AND PURPOSE: Zinc deficiency is associated with multiple clinical complications, including taste disturbance, anorexia, growth retardation, skin changes, and hypogonadism. We investigated the zinc-deficiency-induced morphologic changes in the vallate taste buds of weanling and young adult male Wistar rats. METHODS: A total of 24 weanling and 30 young adult rats were used. Each age group was further divided into a control group fed a zinc-adequate (50 ppm) diet, a zinc-deficient (< 1 ppm) diet group, and a zinc-adequate pair-fed group who were fed the same amount of food as that taken by the zinc-deficient group. Weanling rats were fed for 4 weeks and young adult rats were fed for 6 weeks. The morphometry and morphologic changes of vallate taste buds were analyzed using light and transmission electron microscopy. RESULTS: Light microscopy revealed no significant difference in papilla size and morphology among the various groups. In both weanling and young adult rats in the zinc-deficient diet and pair-fed groups, the number of taste buds per papilla (per animal) and the average profile area of the taste bud were significantly smaller than those of the corresponding controls (p < 0.05). Ultrastructural changes were seen only in the taste buds of weanling rats fed the zinc-deficient diet, with derangement of the architecture of the taste bud and widening of the intercellular space between taste bud cells. The proportion of type I taste bud cells in the taste buds of weanling rats fed the zinc-deficient diet decreased from 59% to 39%, and that of type II taste bud cells decreased from 25% to 12%. No obvious changes in the ultrastructure of type III taste bud cells were observed. CONCLUSIONS: The main effects of zinc deficiency in weanling and young adult rats and in adequate diet pair-fed rats were changes in the number and size of taste buds, and fine structure changes in the taste bud cells, especially during the accelerated growth stage after weaning.

Aging↗

PubMed1997

Differential expression of alpha-gustducin in taste bud populations of the rat and hamster.

The G-protein subunit alpha-gustducin, which is similar to rod transducin, has been implicated in the transduction of both sweet- and bitter-tasting substances. In rodents, there are differences in sensitivity to sweet and bitter stimuli in different populations of taste buds. Rat fungiform taste buds are more responsive to salts than to sweet stimuli, whereas those on the palate respond predominantly to sweet substances. In contrast, hamster fungiform taste buds are more sensitive to sweet-tasting stimuli. Taste buds in the vallate and foliate papillae of both species are sensitive to bitter compounds. These differences in sensitivity should be reflected in the numbers of gustducin-containing cells in different taste bud populations. We examined taste buds in the rat and hamster for immunoreactivity to an antibody against alpha-gustducin. Immunofluorescence of labeled taste cells was examined by confocal microscopy, and the cells were counted. Gustducin-positive cells were seen in all taste bud regions; they were spindle-shaped, with circular cross-sections and apical processes that extended to the taste pore. Cells with this characteristic shape in rat vallate taste buds are Type II (light) cells. In the rat, taste buds of the fungiform papillae had fewer gustducin-positive cells (3.1/taste bud) than those of other regions, including the posterior tongue and palate (>8.9/taste bud). Hamster fungiform taste buds contained twice as many gustducin-expressing cells (6.8/taste bud) as those of the rat. These data support the hypothesis that alpha-gustducin is involved in the transduction of both sweet- and bitter-tasting stimuli by mammalian taste receptor cells.

Animals↗

PubMed1998

Bud formation precedes the appearance of differential cell proliferation during branching morphogenesis of mouse lung epithelium in vitro.

Cell proliferation is an essential requirement for epithelial expansion and tubular branching; however, little is known of how these events are coupled during morphogenesis. We have previously shown that, in the absence of mesenchyme, fibroblast growth factor 1 (FGF-1) elicits budding of the mouse lung epithelium cultured in a basement membrane matrix. Although bud formation seems to be the manifestation of a localized response of lung epithelial cells to FGF-1, it is unclear whether budding results from induction of differential rates of cell proliferation within the epithelium. We performed continuous labeling and pulse-chase experiments in FGF-1-treated mesenchyme-free lung epithelial cultures at distinct stages of bud induction using bromodeoxyuridine (BrdU), to determine when and to what extent cell proliferation contributes to bud formation. When explants were incubated with BrdU either before bud induction (0-18 hr in culture) or at the onset of budding (24-30 hr), labeled nuclei were found distributed throughout the entire explant. In contrast, BrdU incubation after the onset of budding (30-48 hr) resulted in labeling concentrated in the budding areas, and a decrease of labeling toward the proximal region of the explant, between buds. These results demonstrate that differential rates of cell proliferation between bud and nonbud areas do not appear until when buds are almost completely formed. Thus, in the developing lung epithelium in vitro, bud outgrowth is not triggered by induction of localized cell proliferation.

Animals↗

PubMed1994

Endogenous status of retinoids and their cytosolic binding proteins in limb buds of chick vs mouse embryos.

The morphogenetic role of all-trans-retinoic acid (RA) during limb development, especially its activity in directing anterior/posterior pattern formation remains controversial. We have measured retinoids and cytosolic binding proteins in anterior and posterior pieces of limb buds from comparably aged chick and mouse embryos expecting that localization patterns of morphological significance will be evident across species. Many species differences were found including: (1) nondetectable 3,4-didehydroretinoic acid (ddRA) in mouse limb buds, the predominant morphogenetically active retinoid in chick limbs; the precursor of ddRA, 3,4-didehydroretinol (ddROH), was also not present in mouse limb buds but found in high concentration in chick limb buds; (2) a higher concentration of morphogenetically active retinoid (RA + ddRA) in chick compared to mouse limb buds; (3) a high level of retinyl esters (1.5 microM) in chick limb bud, but undetectable concentration in mouse limb buds; and (4) a higher level of cytosolic retinoic acid binding proteins (CRABPs) in chick limb buds, especially CRABP II, which is 10X greater than in mouse limb buds. An interesting finding seen in mouse and chick limb buds was a disparity between the concentration of ligand and cytosolic binding protein. Retinol (ROH) and ddROH were present in much higher concentrations than cytosolic retinol binding protein (CRBP). Conversely, RA and ddRA were in far lower concentration than CRABPs. Any morphological significance of these disparities is unknown. A putative gradient of RA, high posteriorly, was found in chick limb buds as in earlier studies (Thaller and Eichele, 1987), but the magnitude of this gradient was less than previously reported. We also found ddRA in equal concentration in the anterior and posterior pieces of chick limb bud studied here, further weakening the idea of an RA gradient as the direct force in anterior/posterior pattern formation. The "free" concentration of retinoic acid, calculated from ligand and binding protein concentration and affinity, was slightly higher in posterior chick limb tissue (2.0X) and in mouse limb buds at a concentration similar to the Kd of murine nuclear retinoic acid receptors.

Animals↗

PubMed2003

Budding is useful to select high-risk patients in stage II well-differentiated or moderately differentiated colon adenocarcinoma.

PURPOSE: Budding at the invasive front of tumors has recently been thought to suggest greater malignant potential of the colorectal carcinoma. We examined whether budding is associated with poor prognosis after curative resection in Stage II and Stage III colon carcinoma. Furthermore, we examined whether budding is useful to select high-risk patients in Stage II colon carcinoma. METHODS: Surgically resected specimens of 196 Stage II and Stage III colon carcinomas were studied. All the resections were curative (R0), and the median postoperative follow-up was 75.5 months. Using hematoxylin-eosin-stained sections, we determined the presence or absence of budding according to Morodomi's criteria. Routine pathologic findings were also recorded. RESULTS: Budding was detected significantly more frequently in lesions with lymph node metastasis (Stage III) than in lesions without it (Stage II; P < 0.0001). Patients with budding-positive lesions had worse outcome than those with budding-negative lesions: 43 patients (50.6 percent) with budding-positive lesions and 9 (8.1 percent) with budding-negative lesions developed recurrence (P < 0.0001). Patients with budding-positive lesions had a worse prognosis than patients without it (P < 0.0001). Moreover, no significant difference in survival curves was observed between patients with budding-positive Stage II lesions and those with Stage III lesions (P = 0.930). Multivariate analysis revealed budding as the significant prognostic cofactor of postoperative survival in Stage II and Stage III colon carcinoma (P < 0.0001). CONCLUSION: Budding is useful to select high-risk patients in Stage II colon carcinoma.

Adenocarcinoma↗

PubMed1986

Experimental manipulation leading to induction of dorsal ectodermal ridges on normal limb buds results in a phenocopy of the Eudiplopodia chick mutant.

Elongation of chick limb buds depends on the presence of the apical ectodermal ridge which is induced by subjacent limb bud mesoderm. Recombination experiments have shown that the limb bud mesoderm loses the capacity to induce ridges by late stage 17. Moreover, in normal limb development only one ridge forms. However, in the eudiplopodia chick mutant accessory ectodermal ridges form on the dorsal surface of limb buds as late as stage 22. Tissue recombinant experiments show that the mutation affects the ectoderm, extending the time it responds to ridge induction (R.A. Fraser and U.K. Abbott (1971). J. Exp. Zool. 176, 237-248) while the mesoderm is normal. The result is polydactyly, with extra digits dorsal to the normal digits. Because eudiplopodia limb bud dorsal mesoderm can induce ridges at stage 22 but is unaffected by the gene, genetically normal dorsal limb bud mesoderm may also be able to induce ridges after stage 17. To test this possibility we grafted stages 14-18 flank ectoderm to normal limb bud dorsal mesoderm and found that mesoderm from stages 17 through 20 was able to induce a ridge and subsequently dorsal digits developed. Limbs with duplicate digits were similar to eudiplopodia limbs. In other experiments, stage 18, 19, and 20 leg bud dorsal ectoderm did not form ridges when grafted to leg bud dorsal mesoderm of the same stage, indicating a lack of response to the mesoderm. Finally, the inductive capacity of limb bud mesoderm appeared to be reduced compared to mesoderm at pre-limb bud stages. These experiments demonstrate a spatially generalized potential in limb bud dorsal mesoderm to induce ridges during the stages when the apical ridge is induced. The determination of where the ridge will form and the acquired inability of limb bud dorsal ectoderm to respond to induction by underlying mesoderm are necessary early pattern forming events which assure that a single proximodistal limb axis will form.

Animals↗

PubMed1992

Position-dependence of retinoic acid receptor-beta gene expression in the chick limb bud.

Retinoic acid and 3,4-didehydroretinoic acid are metabolites of vitamin A that can induce duplications and other malformations when locally applied to the anterior margin of the chick limb bud. There is evidence that they may be natural signaling substances in the limb bud. Both compounds are thought to act by binding to ligand-dependent transcription factors that belong to the steroid/thyroid hormone nuclear receptor superfamily. In situ hybridization analyses show that in the mesenchyme of the chick wing bud between embryonic stages 20 and 27, retinoic acid receptor-beta (RAR-beta) transcripts are restricted to the proximal region of the bud and are present at highest levels in the region of the limb bud mesenchyme that contributes to the shoulder. We have performed grafting experiments in order to examine whether RAR-beta gene expression in limb bud mesenchyme cells is cell-autonomous or whether it is dependent upon the cell's position within the limb bud. When tissue from the proximal region of the stage 22 wing bud, which contains high levels of RAR-beta transcripts, was grafted to the distal tip of the bud, RAR-beta transcripts were undetectable in the graft 6 hr later. When tissue from the distal tip of the bud was grafted to a proximal site, most of the grafts exhibited a slight increase in the level of RAR-beta transcripts, which was detectable 6 hr after grafting. However, the levels of RAR-beta transcripts in these grafts never approached those found in the proximal core of the bud. These data indicate that RAR-beta gene expression in the chick wing bud is position-dependent in that it is repressed at the distal tip of the bud and partially activated by grafting distal tissue to a proximal site. However, accumulation of RAR-beta transcripts to high levels appears to be a characteristic of mesenchyme that was initially specified to form proximal structures.

Animals↗

PubMed2005

Swe1p responds to cytoskeletal perturbation, not bud size, in S. cerevisiae.

BACKGROUND: S. cerevisiae cells must grow to a critical size in G1 in order to pass start and enter the cell cycle. A recent study proposed that in addition to the mother size control in G1, the bud must grow to a critical bud size in G2 in order to enter mitosis. Insufficient bud size would cause G2 arrest enforced by the mitotic inhibitor Swe1p, explaining previous findings that some perturbations that block bud growth also trigger Swe1p-dependent cell-cycle arrest. RESULTS: We tested the critical-bud-size hypothesis. We found that halting bud growth by inactivation of the myosin Myo2p did not trigger Swe1p-dependent arrest in budded cells, even when the buds were very small. Moreover, Swe1p did not affect cell-cycle progression in unstressed cells, even when bud size was decreased by overriding G1 size control. Actin depolymerization did cause Swe1p-dependent arrest in small-budded but not large-budded cells, as previously reported. However, we found that the key determinant of cell-cycle arrest in those circumstances was not bud size, but rather the relative abundance of the Swe1p mitotic inhibitor and the mitosis-promoting cyclins. CONCLUSIONS: Swe1p does not respond to insufficient bud size. Instead, actin stress empowers Swe1p to promote arrest. The effectiveness of Swe1p in promoting that arrest declines as cells progress through the cell cycle.

Animals↗