Number Of Cambial Cells Research Articles

Гістологічна будова травного тракту куликів (Aves, Сharadrii)

Досліджено гістологічну будову травного тракту 12 видів куликів (Aves, Сharadrii). Установлено, що стінка травного тракту куликів на гістологічному рівні складається із трьох оболонок: слизової (епітеліальний шар, власна пластинка слизової оболонки, підслизова основа), м’язової та серозної оболонки. У власній пластинці слизової оболонки стравоходу куликів виявлено велику кількість езофагальних залоз, які виділяють слиз і сприяють просуванню корму уздовж стравоходу. У залозистому шлунку куликів розташовані глибокі складні залози, парієтально-пептичні клітини, які продукують одночасно пепсиноген і соляну кислоту. Установлено адаптації травного тракту куликів на гістологічному рівні до далеких міграцій, пов’язані з будовою стінки кишечника: складне просторове розташування пластинок слизової оболонки та утворення лабіринтів і анастомозів, багатошарове розташування крипт у стінці тонкого кишечника та високий рівень проліферації камбіальних клітин, що забезпечує регенерацію ентероцитів. Усі вищезазначені особливості гістологічної будови стінки травної трубки сприяють інтенсифікації процесів травлення на міграційних зупинках і дозволяють куликам засвоїти за короткий термін велику кількість доступних кормів

Are neighboring trees in tune? Wood formation in Pinus pinaster

Neighboring trees growing under identical environmental conditions can exhibit different dynamics and periods of growth. Despite the recent advances in cambial biology, the exogenous and endogenous factors generating asynchronous xylem growths still remain undetermined. This study investigated timings and duration of xylem formation in maritime pine (Pinus pinaster Ait.) from an even-aged plantation in Portugal growing under Mediterranean climate. Cambial phenology and stem diameter were monitored weekly, from March to December 2010, on two classes of trees divided according to the tree ring widths of the last 15 years, but similar age and size: fast- and slow-growing trees. We tested the hypothesis that differences in tree ring widths result from cell production which in turn affects timings of xylogenesis and that the bimodal growth pattern, typical of the Mediterranean, originates from a double reactivation of the cambium: in spring and autumn. Cambial activity started earlier and ended later in fast-growing trees, confirming that cell production is a key factor determining the duration of xylogenesis. Intra-annual variations in stem diameter recorded by band dendrometers revealed two peaks of increment occurring in spring and late summer. However, the number of cambial cells did not increase in late summer, which suggested that the second peak of increment was caused by stem rehydration, rather than by a reactivation of cell division. These results demonstrated that the variability in the timings of xylem phenology observed among trees of the same age and size and growing under similar environmental conditions was closely related to cell production and not to age or size per se.

Participation of morphofunctional zones in aging processes

There are morphofunctional zones in organism tissues where proliferation and differentiation processes occur. Daughter cells are differentiated in the electric field excited by 12 mother and daughter cell pairs, produced during cambial cell division. With aging, the number of cambial cells is reduced to seven, which is close to threshold level (six cells) at which the differentiation of daughter cells is absent. The depression of number of cambial cells with aging is connected with the work of another morphofunctional zone, i.e., the hypothalamus, which is the major center of vegetative regulation and initially has very high RhoA activity, which is established during embryogenesis. Estrogens, which influence the hypothalamus and activate Src kinase in its nuclei and reduce the level of RhoA activity, including in the suprachiasmatic nucleus, are responsible for many of an organism’s biorhythms. As a result, hyperestrogenemia and, therefore, connective tissue develop first. Then, hypoestrogenemia takes place, which leads to a sharp drop in the proliferative activity of cells, causing a decrease in the number of cambial cells and the possibility of a malignant tumor development. Along with this, there are deep lesions of hormone regulation that lead to some lethal diseases. Thus, an increase in RhoA in the hypothalamus and especially in suprachiasmatic nucleus circadian rhythm can counteract the Src kinase intensifying and prevent the processes connected with this.

Characteristic features of proliferation and differentiation of cambial and daughter cells in morphofunctional zones in normal epithelium and cancer in age aspect

Work of cambial cells of normal epithelium occurs in morphofunctional zone consisting of two subunits with 12 cells in each. 12 pairs of maternal and daughter cells which have turned out at their division, create the electric field making a differentiation of daughter cells. But it is necessary to relax the cortex of epidermal daughter cells by expression of the SH3 domain of Src-kinase in them with the help of dermal cells that leads to depression of RhoA activity in epidermal cells and the further activation of the SH2 domain of Src in them responsible for a differentiation. With the years, the number of epidermal cambial cells falls from 12 in 20 years to 7 in 75+ in consequence of depression of influence of dermal cells on cambial epidermal cells, which results in dropping of expression of SH2 domain and change of a differentiation of epidermal daughter cells. The reduction of the number of cambial cells to threshold size (6) leads to sharp falling of expression of SH2 domain of Src in daughter cells. This involves augmentation RhoA in relation to Src, falling of formation of stresses-fibrils, microtubules. The stretching of nucleus is sharply decreased, which conducts to formation of incomplete loops of chromosomes, simultaneously nearby a centromere and telomere, thus the cell gets features of an epitheliocyte and a fibroblast, the transcription of proteins is broken, and the daughter epithelial cell becomes malignant.

Peculiarities of Proliferation and Differentiation of Cambial and Daughter Cells of Epidermal-Dermal Morphofunctional Zone in Normal Epithelium and in Cancer

The cambial and daughter cells of normal epithelium function in the morphofunctional zone consisting of two subunits with 12 cambial cells in each. Daughter cells are differentiated in an electrical field created by 12 pairs of maternal and daughter cells, products of division of cambial cells located in the same subunit. The differentiation requires relaxation of the cortex of daughter cells via expression of SH3 domain of Src kinase by dermal daughter cells, which leads to a decrease in activity of RhoA in epidermal cells, their stretching, and activation of SH2 domain of Src responsible for differentiation. Reduction of the number of cambial cells to 6 and, consequently, weakening of electrical field produced by them to a threshold value corresponding to very weak stretching of daughter epithelial cells results in a decrease in SH2 domain expression in these cells and its kinase contribution in Src. This leads to an increase in RhoA relative to Src, enhances cell contraction, impairs formation of stress fibrils and focal contacts, reduces cell flattening, and increases cell mobility. The decrease in the number of microtubules, intermediate filaments, and stress-fibrils changes the major cell axis direction, which, in turn, sharply reduces nucleus stretching and leads to impaired chromosome looping out near the centromeres and telomeres; the cells acquires signs of an epitheliocyte and a fibroblast, protein transcription is impaired, and daughter cells are transformed into malignant cell.

Differential anatomical responses to elevated CO2 in saplings of four hardwood species

To determine whether an elevated carbon dioxide concentration ([CO(2)]) can induce changes in the wood structure and stem radial growth in forest trees, we investigated the anatomical features of conduit cells and cambial activity in 4-year-old saplings of four deciduous broadleaved tree species - two ring-porous (Quercus mongolica and Kalopanax septemlobus) and two diffuse-porous species (Betula maximowicziana and Acer mono) - grown for three growing seasons in a free-air CO(2) enrichment system. Elevated [CO(2)] had no effects on vessels, growth and physiological traits of Q. mongolica, whereas tree height, photosynthesis and vessel area tended to increase in K. septemlobus. No effects of [CO(2)] on growth, physiological traits and vessels were seen in the two diffuse-porous woods. Elevated [CO(2)] increased larger vessels in all species, except B. maximowicziana and number of cambial cells in two ring-porous species. Our results showed that the vessel anatomy and radial stem growth of Q. mongolica, B. maximowicziana and A. mono were not affected by elevated [CO(2)], although vessel size frequency and cambial activity in Q. mongolica were altered. In contrast, changes in vessel anatomy and cambial activity were induced by elevated [CO(2)] in K. septemlobus. The different responses to elevated [CO(2)] suggest that the sensitivity of forest trees to CO(2) is species dependent.

Age-Specific Morphofunctional Changes in Cambial Cells and Their Derivatives in Human Skin

The count of cambial cells decreases with age in the total morphofunctional zone of the skin. However, their number determines the stretching of the daughter cells, which, in turn, activates the Src domain of protein SH2. Twelve cambial cells is the optimal quantity, at which the SH2 domain (responsible later for full-value stretching and looping of chromosomes near telomeres in the region of epithelial cells formation) is sufficiently active, which is characteristic of the age of 20-40 and 41-59 years. If the number of cambial cells is less than 12, stretching of the nuclei and expression of SH2 domain reduce, this leading to looping of lesser sites of chromosomes, modulating the transcription; the expression of Src and RhoA proteins is imbalanced, which leads to reduction of cell proliferation, modification of the direction of the cell's basic axis, and to hyperdesquamation. This is characteristic of the age of over 60 years. After 75 years of age the number of cambial cells in both subunits of the epidermal basal layer decreased to 7 and is close to the threshold level (6 cells), when interactions between fields of the two subunits are weak or zero. Therefore, despite the involvement of both subunits (14 cells), cell stretching and expression of the Src protein SH2 domain in them drop sharply, while activity of RhoA protein increased, which leads to looping of chromosomes closer to the centromeres, that is, to active development of fibroblasts, which is characteristic of subjects over 75 years of age.

Comparative Analysis of the Work of Morphofunctional Zones in Normal Epithelium, Fibroadenoma, and Cancer of the Breast

Twenty-four rosettes (proliferative epidermal units) in epithelial tissue are united into morphofunctional zones, where cambial cells proliferate with the formation of maternal and daughter cells and these latter ones differentiate under the influence of electrical field generated by 12 maternal cells. The number of cambial cells in morphofunctional zone of a malignant tumor is reduced at least 2-fold. Hence, the number of maternal cells is reduced to 6, which is insufficient for electric field generation and stimulation of daughter cells differentiation. The percentage of cambial cells in a benign tumor decreases 1.5 times. Daughter cells are differentiated in an electric field whose strength is below optimal, but above the threshold value at which cells do not differentiate; hence, differentiation is incomplete.

Asynchronous wood formation in youngAcacia mangium planted in Malaysia

In general, tropical trees have less-distinct growth rings. Even if the trees have some concentric structures, there is little information on the timing of their formation. The objective of this report is to show the asynchronous wood formation from the observation of indistinct, ring-like structures. YoungAcacia mangium planted in Malaysia was investigated for asynchronous wood formation anatomically and macroscopically. Tree heights and girths at breast height for 28 trees were measured every other week. Wood disks from four trees were sampled at breast height for this research. The radial variation of vessel dimensions and the number of cambial cells in different radial directions and the wood anatomy of discontinuous bands were investigated using thin sectioning and soft radiographic methods. The vessel dimension was quite different in their radial variation even for four radial directions with a similar radius. There was a large variation in the number of cambial cells among radial directions in youngAcacia mangium. Bands of low density included a layer of vessels aligned in a spiral rather than in a closed circle.