Bud Structure Research Articles

Bud and shoot structure may relate to the distribution area of South American Proteaceae tree species

The capacity of preformation and neoformation and the structure of winter buds are vegetative attributes that may vary between plant species and according to ontogenetic stages of the same species. The present study describes and evaluates these features for the four tree species of Proteaceae occurring in Patagonia. In particular, it analyzes the structure and development of the distal buds of the trunk and the preformed or neoformed nature of the organs involved. Two of the species, Embothrium coccineum and Lomatia hirsuta, have scaly buds, in which primordia of green leaves are covered by cataphylls. The shoots of both species may include neoformed organs, more frequently so in juvenile trees. Lomatia ferruginea and Gevuina avellana have naked buds with a low number of primordia; in juvenile and adult trees of both species trunk shoots are entirely preformed. The structure of buds and shoots suggests two different growth modalities of the axes, which would be related to ecological breadth (narrower in the species with naked buds than in those with scaly buds) and distribution area of these species. The considerable morphological differences between the two Lomatia species studied raise the question whether they ought to be included in the same genus.

Frost hardiness, carbohydrates and bud morphology of Picea abies seedlings after different lengths of freezer storage

In Nordic conditions, conifer seedlings are frozen stored up to eight months. However, there is only little information on the extended freezer storage (more than six months) on frost hardiness (FH) and carbohydrate concentrations in the shoots of Norway spruce seedlings. FH of two-year-old Norway spruce [Picea abies (L.) Karst.] container seedlings were placed in storage on 23 October and kept in storage for 172, 193, 228 or 256 days. Bud structure and carbohydrate concentrations of the needles were analysed. DT50 (temperature causing 50% increase in proportion of needles, stem and buds after freezing exposure) of the measured parts of the seedlings decreased, and changes in DT50 of buds and stems were small between the 172nd and the 193rd day of freezer storage. The concentration of starch increased and the concentration of soluble sugars decreased during the first 172 days of freezer storage. Longer duration of freezer storage, however, did not cause any further changes. The first phase of bud development (pointed lower needle primordial) was already seen in the autumn. The bud development did not change during freezer storage but both the length of the primordial shoot and that of the whole bud increased from October through mid-July. This study suggests that Norway spruce seedlings can be frozen-stored safely for longer periods (eight to nine months) than they are generally stored for currently (six to seven months).

Adipose Tissue-Derived Stem Cell in Vitro Differentiation in a Three-Dimensional Dental Bud Structure

Tooth morphogenesis requires sequential and reciprocal interactions between the cranial neural crest-derived mesenchymal cells and the stomadial epithelium, which regulate tooth morphogenesis and differentiation. We show how mesenchyme-derived single stem cell populations can be induced to transdifferentiate in vitro in a structure similar to a dental bud. The presence of stem cells in the adipose tissue has been previously reported. We incubated primary cultures of human adipose tissue-derived stem cells in a dental-inducing medium and cultured the aggregates in three-dimensional conditions. Four weeks later, cells formed a three-dimensional organized structure similar to a dental bud. Expression of dental tissue-related markers was tested assaying lineage-specific mRNA and proteins by RT-PCR, immunoblot, IHC, and physical-chemical analysis. In the induction medium, cells were positive for ameloblastic and odontoblastic markers as both mRNAs and proteins. Also, cells expressed epithelial, mesenchymal, and basement membrane markers with a positional relationship similar to the physiologic dental morphogenesis. Physical-chemical analysis revealed 200-nm and 50-nm oriented hydroxyapatite crystals as displayed in vivo by enamel and dentin, respectively. In conclusion, we show that adipose tissue-derived stem cells in vitro can transdifferentiate to produce a specific three-dimensional organization and phenotype resembling a dental bud even in the absence of structural matrix or scaffold to guide the developmental process.

Reduction of type II taste cells correlates with taste dysfunction after X-ray irradiation in mice

Taste dysfunction that develops after radiotherapy for head and neck cancer impairs patients' quality of life. Although taste cells have been shown to degenerate after exposure to X-ray irradiation, the alteration in taste cell population is unclear. This study investigated the histopathological change of taste bud structure and the taste cell population in X-ray irradiated mice. The head and neck region of C57BL/6J male mice was exposed to a single 15 Gy dose of X-ray irradiation and a chronological histopathological analysis of the circumvallate papilla was performed. Preference for sweet taste was measured using the two-bottle preference method. The histological analysis of the circumvallate papilla revealed that the basal cells had almost disappeared, but that there was not clear change in the spindle-shaped taste cells on day 4 after irradiation. The number of taste cells had decreased on day 8, and then remained unchanged until day 20, after which they increased and recovered to their original number by day 24. There was a more marked decrease in the number of alpha-gustducin-positive type II taste cells than in the number of serotonin-positive type III taste cells. Preference for sweet taste measured by the two-bottle preference method was decreased in parallel with taste cell number. These findings suggest that X-ray irradiation disrupts the basal cells, resulting in a decrease of the number of taste cells, particularly type II taste cells, which may be the cause of radiotherapy-induced taste dysfunction.

Volumetry of human taste buds using laser scanning microscopy

In vivo laser scanning confocal microscopy is a relatively new, non-invasive method for assessment of oral cavity epithelia. The penetration depth of approximately 200-400 microm allows visualisation of fungiform papillae and their taste buds. This paper describes the technique of in vivo volumetry of human taste buds. Confocal laser scanning microscopy used a diode laser at 670 nm for illumination. Digital laser scanning confocal microscopy equipment consisted of the Heidelberg Retina Tomograph HRTII and the Rostock Cornea Module. Volume scans of fungiform papillae were used for three-dimensional reconstruction of the taste bud. This technique supplied information on taste bud structure and enabled measurement and calculation of taste bud volume. Volumetric data from a 23-year-old man over a nine-day period showed only a small deviation in values. After three to four weeks, phenomenological changes in taste bud structures were found (i.e. a significant increase in volume, followed by disappearance of the taste bud and appearance of a new taste bud). The data obtained indicate the potential application of this non-invasive imaging modality: to evaluate variation of taste bud volume in human fungiform papillae with ageing; to study the effects of chorda tympani nerve transection on taste bud volume; and to demonstrate recovery of taste buds in patients with a severed chorda tympani nerve who show recovery of gustatory sensibility after surgery.

Morphogenetic pathway in petiole derived callus of Amorphophallus albus in vitro

Two different morphogenetic pathways, adventitious bud and corm-like structure (CLS), were observed on organogenic calli derived from the petioles of Amorphophallus albus in vitro. The organogenic calli was established via culture of petiole segments on Murashige and Skoog (MS) medium supplemented with 1.0 mg l−1 α-naphthaleneacetic acid (NAA) and 1.0 mg l−1 6-benzyladenine (BA) and subculture of the petiole-derived calli on MS medium with 0.5 mg l−1 NAA and 0.5 mg l−1 BA. These organogenic calli were used to induce morphogenesis via culture on MS medium with various concentrations of NAA and BA. BA alone favoured adventitious bud differentiation (57.0 ± 8.3% at maximum) from the organogenic calli but inhibited CLS formation. In the presence of NAA and BA, both adventitious bud and CLS were observed in a same culture system. The maximum CLS formation (71.2 ± 9.3%) were found on MS medium with 0.5 mg l−1 NAA and 2.0 mg l−1 BA, associated with 26.7 ± 8.6% adventitious bud differentiation. A small part of the adventitious buds developed into normal shoots which needed rooting culture phase to form complete plants. About 80% survival rate was obtained with these plants after transplantation to soil. More than 90% of the CLSs produced complete plants with shoots and root systems, regardless of the rooting media tested. Transplantation of the CLS-derived plants to soil gave 100% survival rate. Histological observations revealed both the two morphogenetic events originated from the meristematic cells located in superficial layers of callus tissue.

Does timing of boron application affect needle and bud structure in Scots pine and Norway spruce seedlings?

Loss of apical dominance is a well-known boron (B) deficiency symptom in trees. Recent field studies indicate that B deficiency may cause irreversible damage in emerging leader buds leading to bushy growth, and changes in developing needles in mature Norway spruce trees. We experimentally studied if timing of B application affects needles and buds of Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) seedlings with low initial B levels. The treatments were: no B (B0); B supply from the beginning of the simulated summer (B1); starting soon after bud burst (B2) and starting at the occurrence of first needle primordia in new spruce buds (B3). At the end of the experiment, B concentration in B1 was 23 mg kg−1 (pine) or 17 mg kg−1 (spruce) and lower in the later applications. In B0 it was at deficiency limit. In B0, B2 and B3, there were fewer sclerenchyma cells, and cavities occurred in vascular cylinders in pine needles, and in spruce buds there were more tanniferous cells in the primordial shoots compared to B1. Furthermore, in all but B1 there was cell collapse in the bud apex of some spruce seedlings. The experimentally induced changes were the same as earlier reported in B deficient conifers in the field, and indicate, similarly as in the field that adequate B is necessary throughout the growing season for healthy growth, particularly for spruce. The differences between spruce and pines are due, at least partly, to the differences in time frame of needle development and in the differences in development of conducting tissues in the buds.

Fungiform taste bud degeneration in C57BL/6J mice following chorda‐lingual nerve transection

Taste buds are dependent on innervation for normal morphology and function. Fungiform taste bud degeneration after chorda tympani nerve injury has been well documented in rats, hamsters, and gerbils. The current study examines fungiform taste bud distribution and structure in adult C57BL/6J mice from both intact taste systems and after unilateral chorda-lingual nerve transection. Fungiform taste buds were visualized and measured with the aid of cytokeratin 8. In control mice, taste buds were smaller and more abundant on the anterior tip (<1 mm) of the tongue. By 5 days after nerve transection taste buds were smaller and fewer on the side of the tongue ipsilateral to the transection and continued to decrease in both size and number until 15 days posttransection. Degenerating fungiform taste buds were smaller due to a loss of taste bud cells rather than changes in taste bud morphology. While almost all taste buds disappeared in more posterior fungiform papillae by 15 days posttransection, the anterior tip of the tongue retained nearly half of its taste buds compared to intact mice. Surviving taste buds could not be explained by an apparent innervation from the remaining intact nerves. Contralateral effects of nerve transection were also observed; taste buds were larger due to an increase in the number of taste bud cells. These data are the first to characterize adult mouse fungiform taste buds and subsequent degeneration after unilateral nerve transection. They provide the basis for more mechanistic studies in which genetically engineered mice can be used.

B118 ユリの花のつぼみ構造に関する力学的考察(B1-5 生物のバイオメカニズム)

B118 ユリの花のつぼみ構造に関する力学的考察(B1-5 生物のバイオメカニズム)

Macrophages promote collagen fibrillogenesis around terminal end buds of the developing mammary gland

Development of the ductal network in the mammary gland is dependent in part on the presence of macrophages. Here we utilize multi-photon microscopy and second harmonic generation to describe terminal end bud 3-dimensional structure and the organization of the surrounding collagen matrix. We have applied this approach to analyze the effect of macrophage deficiency on terminal end bud structure and collagen organization, using mice homozygous for a null mutation in the colony stimulating factor-1 gene (Csf1op/Csf1op). Primary terminal end buds have an oblong shape, with long collagen I fibers close to the neck of the terminal end bud and radiating upwards in the direction of growth. Around the terminal end buds, the amount of total collagen I detected by antibody staining was not affected by macrophage deficiency. However the amount of collagen I organized into long fibers, detected by second harmonic generation signal, was reduced in Csf1op/Csf1op mice. Macrophage deficiency also caused terminal end buds to be rounder and shorter. These studies reveal a role for macrophages in collagen fibrillogenesis and in organization of the structure of terminal end buds.

Does ice crystal formation in buds explain growth disturbances in boron-deficient Norway spruce?

Loss of apical dominance in boron-deficient trees has been suggested to be due to frost damage of terminal buds and leaders. Excessive nitrogen (N) supply can exacerbate boron (B) deficiency by the dilution-effect. N may also have direct effects on winter hardiness. We studied frost hardening of buds of Norway spruce (Picea abies L. Karst.) in healthy-looking trees and in trees with growth disturbances. The effect of B and N on frost hardiness was studied in a factorial fertilisation experiment during cold acclimation. Frost hardiness was determined by differential temperature analysis (DTA) and scoring of visual damage. In a DTA profile of apical buds with a piece of stem, low-temperature exotherm (LTE) predicted bud injury, while two of the observed high-temperature exotherms and two of the observed intermediate-temperature exotherms were non injurious. Appearance of LTE followed changes in air temperature. The risk of frost damage was not affected by fertilisation treatments or previously observed growth disturbances. However, when the bud structure was deformed by severe B deficiency, the supercooling ability disappeared. Such buds are probably killed by freezing in nature and therefore, frost damage may play a secondary role in the development of growth disturbances.

Confocal microscopy of the Peripheral Gustatory System: Comparison between Healthy Subjects and Patients Suffering from Taste Disorders during Radiochemotherapy

Laser-scanning microscopy (LSM) was used to compare taste buds and epithelia of fungiform papillae of healthy subjects with those of patients suffering from taste disorders during/after radiochemotherapy (RCT). Aim of the study was to investigate effects responsible for taste loss at a microscopic level. Prospective study. Data from 12 healthy subjects (mean age 52.4, SD 9.5 years) were compared with those of 12 patients (mean age 54.7, SD 8.5 years) with head and neck cancer suffering from taste disorders during RCT. Four parameters from LSM were selected for analysis: 1) distance between the pore of the taste buds of fungiform papillae and the crest of the papillary vessels; 2) epithelial cells of each taste bud at 34 mum; 3), cell density, and 4) area of the taste pore at 4 mum. These data were correlated to measures of gustatory sensitivity obtained with both the validated "taste strips" test kit and electrogustometry. Patients complaining from taste disorders during RCT exhibited a significant decrease of taste function assessed with both natural and electric stimuli. In these patients, we found thicker epithelia and smaller areas of the taste pores compared with healthy subjects. In 30% of those patients, no taste pores were detectable; in deeper sections, however, normal taste buds were present. In conclusion, in RCT patients with taste disorders, LSM indicates changes of epithelia of fungiform papilla but no changes of the taste bud structure. Damage of the chorda tympani nerve by scattered rays, direct or indirect mucotoxic effects of chemotherapeutic agents, and covering of taste pores by epithelial cells are likely reasons for taste loss during RCT.

Chorda tympani nerve transection at different developmental ages produces differential effects on taste bud volume and papillae morphology in the rat

Chorda tympani nerve transection (CTX) results in morphological changes to fungiform papillae and associated taste buds. When transection occurs during neonatal development in the rat, the effects on fungiform taste bud and papillae structure are markedly more severe than observed following a comparable surgery in the adult rat. The present study examined the potential "sensitive period" for morphological modifications to tongue epithelium following CTX. Rats received unilateral transection at 65, 30, 25, 20, 15, 10, or 5 days of age. With each descending age at the time of transection, the effects on the structural integrity of fungiform papillae were more severe. Significant losses in total number of taste buds and filiform-like papillae were observed when transection occurred 5-30 days of age. Significant reduction in the number of taste pores was indicated at every age of transection. Another group of rats received chorda tympani transection at 10, 25, or 65 days of age to determine if the time course of taste bud degeneration differed depending on the age of the rat at the time of transection. Taste bud volumes differed significantly from intact sides of the tongue at 2, 8, and 50 days post-transection after CTX at 65 days of age. Volume measurements did not differ 2 days post-transection after CTX at 10 or 25 days of age, but were significantly reduced at the other time points. Findings demonstrate a transitional period throughout development wherein fungiform papillae are highly dependent upon the chorda tympani for maintenance of morphological integrity.

A signaling pathway involving TGF-beta2 and snail in hair follicle morphogenesis.

In a common theme of organogenesis, certain cells within a multipotent epithelial sheet exchange signals with their neighbors and develop into a bud structure. Using hair bud morphogenesis as a paradigm, we employed mutant mouse models and cultured keratinocytes to dissect the contributions of multiple extracellular cues in orchestrating adhesion dynamics and proliferation to shape the cluster of cells involved. We found that transforming growth factor β2 signaling is necessary to transiently induce the transcription factor Snail and activate the Ras-mitogen-activated protein kinase (MAPK) pathway in the bud. In the epidermis, Snail misexpression leads to hyperproliferation and a reduction in intercellular adhesion. When E-cadherin is transcriptionally down-regulated, associated adhesion proteins with dual functions in signaling are released from cell-cell contacts, a process which we demonstrate leads to Ras-MAPK activation. These studies provide insights into how multipotent cells within a sheet are stimulated to undergo transcriptional changes that result in proliferation, junctional remodeling, and bud formation. This novel signaling pathway further weaves together the web of different morphogens and downstream transcriptional events that guide hair bud formation within the developing skin.

Links between signal transduction, transcription and adhesion in epithelial bud development.

The morphogenesis of organs as diverse as lungs, teeth and hair follicles is initiated by a downgrowth from a layer of epithelial stem cells. During follicular morphogenesis, stem cells form this bud structure by changing their polarity and cell-cell contacts. Here we show that this process is achieved through simultaneous receipt of two external signals: a Wnt protein to stabilize beta-catenin, and a bone morphogenetic protein (BMP) inhibitor to produce Lef1. Beta-catenin then binds to, and activates, Lef1 transcription complexes that appear to act uncharacteristically by downregulating the gene encoding E-cadherin, an important component of polarity and intercellular adhesion. When either signal is missing, functional Lef1 complexes are not made, and E-cadherin downregulation and follicle morphogenesis are impaired. In Drosophila, E-cadherin can influence the plane of cell division and cytoskeletal dynamics. Consistent with this notion, we show that forced elevation of E-cadherin levels block invagination and follicle production. Our findings reveal an intricate molecular programme that links two extracellular signalling pathways to the formation of a nuclear transcription factor that acts on target genes to remodel cellular junctions and permit follicle formation.

Postnatal development of the mouse volatile papilla taste bud cells.

In the present study, we examined specific markers for taste bud cells in the mouse and the postnatal development of volatile papilla taste bud cells in ddY mice. We examined the immunoreactivity of 4 types of carbonic anhydrase isoenzymes, CA I, CA II, CA III and CA VI, as specific markers for taste bud cells, and K8.13 cytokeratin antibody as a specific marker for the lingual epithelial cells. Of the carbonic anhydrase isoenzymes, only CA III immunoreactivity was clearly detected in the spindle shaped gustatory cells. CA VI immunoreactivity was detectable in suspentacular cells. CA I and CA II antibodies did not recognize any taste bud cell specifically. K8.13 cytokeratin immunoreactivity was detected in the lingual epithelial cells, but not in taste bud cells. At 7 days after birth, the suckling phase, very small taste buds developed from the anaplastic gustatory cells. At 14 days after birth, the taste buds showed larger size than those at 7 days after birth. At 21 days birth, after the weaning phase, taste bud structure approximated the mature structure. These results demonstrate the specificity of anti-CA III and anti-CA VI for gustatory cells and suspentacular cells, respectively. These markers should be useful for an analysis of taste bud development in mice.

Fine structure of undifferentiated gonads in Rana dalmatina tadpoles

The ultrastructure of Rana dalmatina tadpoles’ gonads is described during two early stages of development: the primary and the secondary undifferentiated condition. The gonadal bud structure in the first stage of differentiation is characterized, and it is clearly demonstrated that the cortex and the medulla are lined by an uninterrupted basal lamina along the margin adjacent to the primary cavity. The basal lamina that lines the cortex is a continuation of the one delimiting the somatopleura. In the second stage, it is shown that the medulla delaminates to form a secondary gonadal cavity known as the ovarian pocket, and that the cortex contains early germ cells, both isolated and undergoing mitotic division, corresponding to a germinal epithelium. In addition the diplotenic oocytes form a distinct layer within the primary gonadal cavity between the cortex and medulla. Each of the three layers (germinal epithelium, diplotenic oocytes, and hollow medulla) is delimited by its own basal lamina. The ultrastructure of the different germ and somatic cells is described.

Olive Floral Bud Growth and Starch Content During Winter Rest and Spring Budbreak

In the olive (Olea europaea L.), inflorescence and flower differentiation occur in the early spring following a period of winter chilling and dormancy of the potentially reproductive buds. We examined the size, structure, and starch content of these buds during winter rest in the field and during forcing under standard growth-chamber conditions. Basic bud structure and dimensions remained unchanged during the rest period, but starch content increased in the bud's central axis. When cuttings were forced in the growth chamber, the buds followed a morphogenetic pattern similar to that observed in the field, but the sequence of developmental events could be timed more precisely. The first changes observed were the onset of axis growth and the differentiation of axillary primordia within 3 days of transfer to the growth chamber. This was followed by the initiation of new nodes, and, at 15 to 18 days, by the first signs of floral differentiation in the terminal and axillary bud apical meristems. Bud growth and differentiation were accompanied by a decrease in starch content.

Neonatal chorda tympani transection permanently disrupts fungiform taste bud and papilla structure in the rat

The present report examined the morphology of fungiform papillae in adult rats that received bilateral chorda tympani transection at 10 days of age. Tongue tissue was examined using surface-structure analysis. Counts were made of fungiform papillae with a pore, fungiform papillae with no pore and fungiform papillae with a keratinized conical surface; a feature referred to as “filiform-like.” Neonatal chorda tympani nerve transection resulted not only in a loss of taste buds but also in a permanent loss in numbers of fungiform papillae. Compared with an average of 152 fungiform papillae in sham-operated control rats, there was an average of only 54 fungiform papillae after neonatal chorda tympani transection. Nearly 80% of these fungiform papillae in neonatal chorda tympani transected rats were filiform-like. No filiform-like papillae were noted in sham-operated rats. These results suggest that the chorda tympani nerve is necessary during an early postnatal period of development to maintain normal fungiform papillae morphology.

Sproßbildung einiger Orchidaceae der Kola-Halbinsel (Nordwest-Rußland): Shoot structure of some Orchidaceae of the Kola-PI. (N Russia)

Summary A study of the root-tuber, rhizome and root-cluster orchids demonstrated essential structural resemblance of their monocarpic shoots and particularities of their regeneration. Species studied here are of different growth forms but belong to the same “long-stalked sympodial” model (sensu T. I. S erebrjakova 1977) of shoot formation. On the basis of the bud structure and the spatial orientation of annual shoots three growth patterns of this model were described: the additive, circular and pendulum growth mechanisms. The root-cluster growth form represents the transitional form between the short-rhizome and the root-tuber growth forms. The root-tuber growth form seems to be the evolutionary youngest. The spatial structure of orchid populations of different growth forms can be explained through the specialities of their shoot development.