Average Cell Length Research Articles

Morphological evaluation of vascular smooth muscle cell: length and width from a single scanning electron micrograph of microvessels.

Accurate three-dimensional data on the structure of vascular smooth muscle cells is essential for understanding the microvascular system in both normal or disease conditions. The laborious serial reconstruction methods have limited the amount of data collected on the structure of individual vascular smooth muscle (VSM) cells. The circumferential viewing of whole vessel segments via scanning electron microscopy provides an alternative approach, but even this technique is highly specialized and tedious. This study presents a simplified method to determine the average cell length and width of individual VSM cells by using only one view of a microvessel (single view). The vessels do not have to be isolated for circumferential viewing and can be left in their host tissue if desired. Values for the average VSM cell length and width were obtained by both circumferential- and single-view approach on the same vessels. The average cell length and width obtained from the single-view method (using one-third circumference) duplicated the mean length and width measurements obtained by circumferential viewing.

Changes in the somatic musculature of the 4th-stage larvae of Ascaris suum Goeze, 1782 (Nematoda: Ascaridoidea) developing in swine.

Fourth-stage larvae of Ascaris suum, recovered from piglets at 11-22 days post-infection (p.i.), were examined by light microscopy for changes in the somatic musculature. During this time the estimated total number of muscle cells in the body increases from approximately 600 to 21 000 cells. This non-eutelic development appears to occur by division of platymyarian muscle cells into coelomyarian cells, thereby increasing the number of muscle cells/quadrant from 5 to 85. The incompleteness of these divisions results in sarcoplasmic connections among muscle cells, and between muscle cells and nerve chords. At 11 days p.i., immediately after the 3rd moult, the variation in muscle cell length in a quadrant, with the longest cells being at the lateral chords, has been established. The average muscle cell length at this point is 0.101 mm, the longest is 0.164 mm. These values have increased to 0.365 mm and 1.122 mm, respectively, by 22 days p.i. At 18 days p.i. those cells in the posterior section of the larva are still the shortest in the body.

Erickson and Sax's Analysis of Cell Production and Elongation During Root Growth

Erickson and Sax's equation for the analysis of cell production and elongation in root apices and Gandar's criticisms of this equation are reexamined It is shown that Erickson and Sax's equation can be applied to the analysis of growth, provided their terms for the rates of change of average cell length, and of file number, are interpreted as material derivatives

The Effects of Roughness and Shear on Vortex Shedding Cell Lengths Behind a Circular Cylinder

Circular cylinders of aspect ratio L/D=17 were tested in a wind tunnel under a wide range of spanwise upstream velocity shears. The correlation between upstream shear, characterized by a nondimensional shear parameter β, and the spanwise lengths of constant vortex shedding frequency was sought for both smooth and rough cylinders in transitional Reynolds numbers flows. Among the significant conclusions are that the spanwise range in shedding frequencies decreases with increasing roughness, the average constant shedding frequency cell length increases with increasing roughness for constant shear, and the average cell length decreases with increasing upstream shear for constant roughness.

Dimensional rearrangement of rod-shaped bacteria following nutritional shift-up. I. Theory

Theoretical expressions are derived for two models that describe average length and radius of a population of rod-shaped bacteria as a function of time following their transfer to a medium that supports a higher growth rate. The first attributes cell elongation to circular zones produced at a particular time during the cell cycle and which act thereafter at rates proportional to the growth rate; the second is formally identical but considers surface growth rather than length extension. Two possibilities are considered, that the zonal growth rate adjusts immediately to the transition, and that it does so gradually. The results are also displayed graphically, covering a broad range of each of the various parameters involved; values are chosen to permit a direct comparison between the models. Average cell length is seen to undergo a large overshoot and to approach its steady-state value from above, while cell radius remains almost constant or even decreases somewhat before increasing monotonically towards its asymptotic level; both require a considerable period of time to reach steady state. The transient behavior predicted by the two models is found to be quite different even when the steady-state dimensions are identical; the differences between immediate and gradual response of the zonal growth rate are even greater. It is shown that using a dimensionless measure of cell geometry, the aspect ratio, can facilitate selection of the appropriate model.

Relationship between extracellular enzymes and cell growth during the cell cycle of the fission yeast Schizosaccharomyces pombe. II. Sucrase.

By using intact cells of the fission yeast Schizosaccharomyces pombe, the derepressed activity of sucrase (EC 3. 2. 1.26), as extracellular enzyme located in the periphery of the yeast, was measured during the cell cycle, with cell length serving as the measure of cell growth. Both specific activity of sucrase and average cell length were constant through asynchronous cultures. Under the same experimental conditions as for asynchronous cultures, the specific activity of sucrase showed a pattern of periodic synthesis after either selection synchronization by the gradient sedimentation method or induction synchronization by pulse treatment with hydroxyurea (HU), an inhibitor of DNA synthesis. On the other hand, the specific activity of sucrase continued to increase exponentially when HU was added to the asynchronous culture or to the selection-synchronous culture, but decreased stepwise in induction- synchronous cultures in a poor medium after selection, in which the cells divided synchronously without cell elongation. The patterns of sucrase activity in all systems were parallel to those for average cell length.These results suggest that the synthesis of sucrase is dependent on the growth in cell length as well as acid phosphatase as we reported in a previous paper (1).

Hypertrophic smooth muscle. I. Size and shape of cells, occurrence of mitoses.

An extensive hypertrophy of the muscle coat develops in the small intestine of the guinea pig oral to an experimental stenosis. The profiles of smooth muscle cells become larger and irregular in shape. From the analysis of serial sections the arrangement of the muscle cells is less orderly than in control muscles. Many muscle cells are split into two or more branches over part of their length. The average cell volume is 3--4 times that of control muscle cells; the cell surface increases less dramatically and, in spite of the appearance of deep invaginations of the cell membrane, the surface-to-volume ratio falls from 1.4 to 0.8. The average cell length is only slightly increased compared with controls. Smooth muscle cells in mitosis are observed in all the hypertrophic muscles examined, in both muscle layers; in the circular musculature they occur mainly found in the middle part of the layer.

Relationship between extracellular enzymes and cell growth during the cell cycle of the fission yeast Schizosaccharomyces pombe: acid phosphatase.

By using the intact cells of the fission yeast Schizosaccharomyces pombe, the activity of acid phosphatase (EC 3.1.3.2) was compared through the cell cycle with the growth in cell length as a measure of cell growth. The cells of a growing asynchronous culture increased exponentially in number and in total enzyme activity, but remained constant in average length and in specific activity, In a synchronous culture prepared by selection or by induction, the specific activity was periodic in parallel with the increase in average cell length. When hydroxyurea was added to an asynchronous or a synchronous culture by selection, both specific and total activity followed the same continuous pattern as the growth in cell length after the stoppage of cell division. When oversized cells produced by a hydroxyurea pulse treatment to the culture previously syndronized by selection were transferred to a poor medium, they divided synchronously but could hardly grow in the total cell length. In this experimental situation, the total enzyme activity also scarcely increased through three division cycles. These results suggested that the increase in acid phosphatase in dependent on cell elongation.

Estimate of cellular force generation in an arterial smooth muscle with a high actin: myosin ratio.

An in vitro preparation from the media of the pig carotid artery develops somewhat higher force/cell cross-sectional area with one-fifth the myosin content of skeletal muscle cells. The following results suggest that this performance reflects cellular properties rather than the arrangement of cells within the tissue: (1) force development at the peak of the length-force curve is independent of the length of the tissue segment in a strip of constant cross-section, and (2) average cell length is directly proportional to tissue length. We conclude that the contractile system of arterial smooth muscle cells is specialized for force generation and that the mechanical properties of the pig carotid media preparation provide valid estimates of cellular function.

Deformation of human erythrocytes in a centrifugal field

A new method for altering red cell morphology by high-speed centrifugation of cells through a physiological medium is described. Cell shape is preserved for microscopic analysis by allowing the sedimenting cells to pass from the physiological medium into a glutaraldehyde fixative solution. Examination of the deformed, fixed cells indicates that the vast majority resemble spheres with a flat, triangular tail. Measurements of the overall length of deformed cells show a nearly linear relationship between cell length and centrifugal force; average cell length increased from 8 to 11 micrometer as the centrifugal field was increased from 2,000 to 15,000 g. These data suggest that this centrifugal technique may be useful for evaluating cellular deformability and, potentially, the material properties of red cells.

Seasonal size changes in certain diatoms and their possible significance

Cell sizes of two species of diatoms, Stephanodiscus astraea and Asterionella formosa, were determined in algal populations in four water bodies at various times of the year. Changes in the average cell diameter or length were observed throughout the growing seasons. The possible effects of these cell size changes are discussed in relation to parameters such as rate of sinking, nutrient absorption, temperature, viscosity and turbulence.

Control of cell length in Bacillus subtilis.

During inhibition of deoxyribonucleic acid synthesis in Bacillus subtilis 168 Thy-minus Tryp-minus, the rate of length extension is constant. A nutritional shift-up during thymine starvation causes an acceleration in the linear rate of length extension. During a nutritional shift-up in the presence of thymine, the rate of length extension gradually increases, reaching a new steady state at about 50 min before the new steady-state rate of cell division is reached. The steady-state rates of nuclear division and length extension are reached at approximately the same time. The ratio of average cell length to numbers of nuclei per cell in exponential cultures is constant over a fourfold range of growth rates. These observations are consistent with: (i) surface growth zones which operate at a constant rate of length extension under any one growth condition, but which operate at an absolute rate proportional to the growth rate of the culture, (ii) a doubling in number of growth zones at nuclear segregation, and (iii) a requirement for deoxyribonucleic acid replication for the doubling in a number of sites.

Quantal behavior of a diffusible factor which initiates septum formation at potential division sites in Escherichia coli.

Analysis of nucleated cell size in a minicell-producing strain of Escherichia coli and in its parental strain shows that the two distributions are considerably different. A model is proposed to account for this difference. The model states that: (i) in the mutant population, the cell poles are available as potential division sites in addition to the normally located division sites; (ii) the probability of a division occurring at any of the potential division sites is equal; and (iii) only enough "division factor" arises at each unit cell doubling to permit a single division. This factor is utilized entirely in the formation of a single septum. Thus, the occurrence of a polar division with the production of an anucleate minicell (which occurs only in the mutant strain) prevents the occurrence of a non-polar division, with the result that the average nucleated cell length is increased in minicell-producing strains. The model has been used to construct a theoretical population, and a number of parameters of the real and theoretical populations have been compared. The two populations are very similar in all of the parameters measured.

QUANTITATIVE THERMAL‐INDUCED CHANGES IN GROWTH AND CELL POPULATION KINETICS OF HELIANTHUS ROOTS

A complete kinetic analysis of temperature‐induced changes in primary root growth of Helianthus annuus was undertaken. Growth rate was expressed in terms of the rate of cell production per file and the average cell length at maturity. Growth rate increased from 0.014 cm · hr−1 at 10 C to a maximum of 0.162 cm · hr−1 at 25 C and decreased at higher temperatures. The rate of cell production per file, which is dependent on the mitotic cycle duration and the number of proliferating cells in the meristem, reached a maximum of 8.55 cells hr−1 at 25 C. The mitotic cycle duration decreased from 46.4 hr at 10 C to a minimum of about 6.3 hr at 30 and 35 C. The mitotic index remained constant between 10 and 35 C. At 30 and 35 C the duration of the S period was about 65% of the total cycle time, while at 10 C it was about 50 %. The number of proliferating cells in a meristem remained constant between 15 and 25 C and decreased with further increase in temperature. Therefore, the temperature at which the rate of cell production was maximum was not the temperature at which cycle time was minimum. The maximum length of mature cells occurred between 15 and 30 C. The contribution of each of the above parameters to temperature‐induced changes in growth rate is discussed.

Folic acid deficiency in lactobacillus casei

The effect of folate starvation on the biochemical constitution and morphology of Lactobacillus casei was studied by growing cultures in different concentrations of folic acid. Folate starvation leads to a marked reduction in the amount of DNA synthesized, a large increase in the average cell length and a striking loss of viability. In addition, extreme folate starvation leads to small reductions in the amount of RNA and protein synthesized. The similarities between folate deprivation in L. casei and in man suggest that the bacterial system may provide a convenient model of the condition in humans.

Studies on the relationships between cell population and growth kinetics of root meristems

Experiments were performed with three varieties of Pisum sativum (Alaska, Weitor, and Witham Wonder), Helianthus annuus and Vicia faba to further study the relationship between cell population and growth kinetics of root meristems. The duration of the mitotic cycle, DNA synthesis (S period), pre-DNA synthetic period (G1), post-DNA synthetic period (G2) and mitosis were measured by simultaneously marking meristematic cells with colchicine and 3H-thymidine. Autoradiography was used to distinguish the cells labeled with 3H-thymidine. The number of proliferating cells was estimated mathematically from cell population kinetic data and cell counts; the number of cell files was determined from cross sections of the meristem; the growth rate was measured once daily. The results indicated that the mitotic cycle, S, G1, G2, and mitotic duration were very similar in all varieties of Pisum; that Helianthus had the shortest G2 period of all plants tested, and that Vicia had a longer S and cycle duration. Root growth rate was shown to be the reflection of the rate of cell proliferation per file and the average cell length at maturity and that the latter can be estimated by cell population and growth kinetics. The studies also demonstrated that neither mitotic cycle duration, root growth, cell counts, nor mitotic indices exclusively measure the growth and proliferative capacity of a tissue but rather a combination of all four parameters are necessary for an accurate estimation.

An Analysis of Stamen Filament Growth of Nigella hispanica

The post-meiotic stamen filament of Nigella hispanica L. under greenhouse conditions grows in length from 1 mm to approximately 10 mm at maturity in 16 days. Analysis of the filament epidermis suggests that the intercalary meristem is diffuse along the filament with a mid-point of activity near the center of the filament. The point of maximal activity, while initially central, is variable as cell division nears completion. Measurement of cell lengths along filaments suggests that an elongation gradient from base to tip is operative in filaments 1 mm and longer. Average cell lengths of epidermal cells increase faster than do those of terminal cells. Once average cell length begins to increase in any region of the epidermis it continues to do so until flower maturity. At maturity the longest epidermal cells are near the filament base and the shortest cells are at the tip. The differences between cell division and cell elongation patterns suggest that these two processes are controlled by different sites or substances. A comparison is made between the development of the Nigella filament and other determinate organs having intercalary meristems.

AN ANALYSIS OF STAMEN FILAMENT GROWTH OF NIGELLA HISPANICA

The post‐meiotic stamen filament of Nigella hispanica L. under greenhouse conditions grows in length from 1 mm to approximately 10 mm at maturity in 16 days. Analysis of the filament epidermis suggests that the intercalary meristem is diffuse along the filament with a mid‐point of activity near the center of the filament. The point of maximal activity, while initially central, is variable as cell division nears completion. Measurement of cell lengths along filaments suggests that an elongation gradient from base to tip is operative in filaments 1 mm and longer. Average cell lengths of epidermal cells increase faster than do those of terminal cells. Once average cell length begins to increase in any region of the epidermis it continues to do so until flower maturity. At maturity the longest epidermal cells are near the filament base and the shortest cells are at the tip. The differences between cell division and cell elongation patterns suggest that these two processes are controlled by different sites or substances. A comparison is made between the development of the Nigella filament and other determinate organs having intercalary meristems.

GROWTH AND DIFFERENTIATION IN THE ROOT TIP OF PHLEUM PRATENSE

books usually figure the root tip in longitudinal section with various regions marked off: root cap, meristematic zone, zone of elongation, and zone of differentiation or maturation. Such descriptive demarcations fail to give quantitative information concerning the absolute or even the relative rates at which the various developmental processes, which are supposed to be occurring in these regions, are actually taking place. The nature of the transitions between one zone and the next are often completely ignored. 1Received for publication July 14, 1914. Growth rate measurements were made by the junior author, who is now serving with the armed forces. In 1939, Sinnott pointed out the suitability of certain species of small-seeded grasses for, studies of the growing root tip. In these species the transparency of the fine roots and the rudimentary character of the root caps permit unobscured microscopic observation of the surface of the living meristems. Brumfield (1942) has made some interesting experimental studies on one of these species, Phleum pratense L., in which rates of elongation of roots at various distances from the root apex were measured. In this paper methods are developed for determining rate of elongation of a root, cell elongation, rate of transverse cell division, and rate of increase in cell wall area, each expressed as a function of distance from the root apex. These methods are then applied to roots of Phleum pratense. The resulting data give a graphic picture of the above-mentioned developmental processes which are taking place within the growing region of a root and of the complex interrelations between them. Some further observations on the differentiation of vascular elements are correlated with these findings. THEORETICAL METHODS.-Rate of elongation.Seedlings of grasses such as Phleum pratense may be grown in vertical culture chambers so constructed as to allow examination of the root meristems under high magnifications with a compound microscope. It is possible to measure the amount of growth occurring during short time intervals between the root apex and characteristically-shaped epidermal marker cells. When such growth increments in unit time (r) are plotted against the initial distance (x) of the marker cells from the root apex, sigmoid curves, representing the rates of displacement of x from the root apex, are obtained (fig. 2). It should be pointed out that the time interval must be sufficiently short to prevent undue displacement of the marker cell from its original position, x units of distance from the root apex. The first derivatives of these sigmoid curves, dr/dx (the slope of the tangent to the curve at any point), give the rates of elongation of the roots as a function of distance from the tip (fig. 3). Average length of epidermal cells.-The length (1) of epidermal cells at various distances from the root apex may be readily determined. Camera lucida drawings of the surface of actively-growing roots cannot be made with sufficient rapidity to serve for this purpose. If large numbers of cells are to be measured, it may be convenient to make such measurements upon roots killed in fixatives which do not appreciably distort the cell dimensions, although measurements from photographs of living roots should be preferable. The length of cells in the subepidermal layers may be studied from longitudinal sections. Figure 4 shows the average length of epidermal cells with their basal ends at x.

DEVELOPMENTAL STUDIES WITH BRASSICA SEEDLINGS

DEVELOPMENTAL STUDIES WITH BRASSICA SEEDLINGS