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We used numerical solutions for cable equations representing nonuniform cardiac strands to investigate possible mechanisms of unidirectional block (UB) of action potential propagation. Because the presence of UB implies spatial asymmetry in some property along the strand, we varied membrane properties (gNa or leakage conductance), cell diameter, or intercellular resistance as functions of distance such that a propagating action potential encountered the parameter changes either gradually or abruptly. For changes in membrane properties there was very little difference in the effects on propagation for the gradual or abrupt encounter; but, for changes in cell diameter or in intercellular resistance, there were large differences leading to the production of UB over a wide range of parameter values.

Introductory Paragraph Rod-shaped bacteria grow by adding material into their cell wall via the action of two spatially distinct enzymatic systems: The Rod complex moves around the cell circumference, while class A penicillin-binding proteins do not. To understand how the combined action of these two systems defines bacterial dimensions, we examined how each affects the growth and width of Bacillus subtilis, as well as the mechanical anisotropy and orientation of material within their sacculi. Rod width is not determined by MreB, rather it depends on the balance between the systems: The Rod complex reduces diameter, while aPBPs increase it. Increased Rod complex activity correlates with an increased density of directional MreB filaments and a greater fraction of directional PBP2a enzymes. This increased circumferential synthesis increases the relative amount of oriented material within the sacculi, making them more resistant to stretching across their width, thereby reinforcing rod shape. Together, these experiments explain how the combined action of the two main cell wall synthetic systems builds and maintains rods of different widths. Escherichia coli Rod mutants also show the same correlation between width and directional MreB filament density, suggesting this model may be generalizable to bacteria that elongate via the Rod complex.

SYNOPSIS The carcinostatic action of phenazine-di-N-oxide against the Ehrlich tumour was subjected to closer study on individual cells. A method was devised whereby the increase in cell diameter could be followed by direct measurement on the projected microscope image. After standardization of the optics so that 1 μ on the slide equalled 1 mm on the ruler, 50 cells per 20 minutes could be measured randomly. Observations 24 hours after drug administration into a mouse bearing a 7-day tumour showed that treated cell diameters increased from a median diameter of 14 μ to a median of 21 μ (many had doubled in size) as compared to an increase of 1.9 μ in the controls. After 72 hours the treated cells reached a maximum diameter and disintegrated. By this time there was an absence of ascitic fluid. The drug acted by accelerating the growth and exaggerating the disordered mitoses of the tumour cells which were unable to cleave daughter cells, leaving a cluster of partially divided protuberances.

Various growth parameters of the rat extensor digitorum longus muscle were studied during the first week of neonatal growth, including changes in weight, length, girth and fiber number. These quantitative studies were supplemented by ultrastructural analysis of fiber diameter and morphology in an attempt to determine the source of “new” muscle fibers in the neonate. In the 2-day-old extensor digitorum longus many of the myofibers were enclosed with other filamented cells (a satellite myofiber and/or myotube) in a common basement membrane, forming a cluster. Clusters accounted for 40% of the total independent filamented cells and clusters in 2-day-old muscles, for 2% in the 5-day-old, and for less than 1% in the 8-day-old. The decrease in the percentage of clusters occurred concomitantly with an increase in the number of independent filamented cells. In the 2-day-old there were 2,932 ± 130 independent cells and clusters; this number increased by 90% in the 8-day-old muscle. Mean diameters of filamented cells (whether found independently or as part of a cluster) increased from 6.5 μm to 7.4 μm and to 9.5 μm on days 2, 5, and 8 respectively. Increased filamented cell diameter between days 2 and 5 was a result of growth of the smallest filamented cells into the medium-size compartment. Between the fifth and eighth day postpartum, the increase was due to the growth of both small and medium-size filamented cells. The largest fibers did not increase in diameter during the first week of postnatal development, maximal fiber diameter in the 2-day-old being 15.9 μm and in the 8-day-old, 16.1 μm. At two-days the area through the widest girth of the muscle occupied by filamented cells was 35% of the total cross-sectional area of the extensor digitorum longus. At eight days muscle fibers occupied 59% of the cross-sectional area. To accommodate the myofibers the muscle belly increased its girth, and there was a decrease in the percentage of the area occupied by interstitial tissue, nerves, and blood vessels.

Green algae of the genus Chlorella are widely used in photosynthesis research. The lack of morphological characters that are suitable for a traditional classification of this genus has led to the development of a biochemical taxonomy, which uses a key of easily determined biochemical and physiological characters for the delimitation and characterization of 14 Chlorella species with 88 strains (KESSLER, 1982).

Semiquantitative and quantitative assessments of the morphology of endomyocardial biopsies at light microscopic level have been undertaken to evaluate whether or not these methods are of use in analysing the biopsies — e.g., is it possible by using these methods to differentiate between a cardiomyopathy and a specific heart muscle disease of seemingly identical morphology?

A method is described in which the volume, surface area, and diameter of spherical cells can be quickly and easily determined from linear calibration curves using a flow cytometer which measures electronic volume and is equipped with a log amplifier.

Pulse labelling with tritiated thymidine was used to determine the time of the final division of the neuroblasts which subsequently form rat lumbar dorsal root ganglion neurones. The final division occurred during a 4 day period, the maximum frequency being on day 12 of gestation. Separation of the ganglion cells into large light neurones and small dark neurones showed that the large light neurones were formed earlier than the small dark neurones. In both cases the final divisions occurred over a period of 3–4 days, but the peak rate of formation of large neurones was on day 12, and that of the small neurones was on day 13.

An apparatus to measure the relative transit time of red cells through the aperture of the Coulter-type blood cell counter was developed. The times measured showed a high correlation with the diameters of the red cells tested. The findings suggested that the apparatus would be suitable for determining relative cell diameter. As a second experiment, a comparison of the transit times under two different aspiration pressures was carried out. Time ratios at two different aspiration pressures appeared to reflect red cell deformability.

The mean fat cell diameter was determined from measurements of abdominal adipose cells, obtained during inguinal hernia repair, of 126 white and 95 black males ranging in age from 1 through 48 months of age. The mean diameters of black and white subjects did not differ significantly, suggesting that differences in fatness among adults of these two ethnic groups have their origin beyond the age range of this study. The mean fat cell diameter increased through the 6-8 month age group, decreased until the end of the first year, and then levelled off through 48 months of age. Comparison of this curve with those for the triceps, subscapular, abdominal, and suprailiac skinfolds of the same subjects showed generally parallel courses except for the triceps, which continued to increase in size after the means of fat cell diameters and the other skinfolds had levelled off. Our data indicate that changes in body fatness on the trunk at least in the first 4 years of life may be accounted for by changes in fat cell size.

Cryptococcus neoformans yeast cells 40 to 60 micron in diameter were seen in an India ink preparation made from a human brain abscess specimen. In culture at 25 degrees C, uniform 5-micron-diameter yeast cells were produced. Inoculation into mice produced yeast cells up to 40 micron in diameter, and brain heart infusion broth culture at 35 degrees C produced yeast cells about 25 micron in diameter. A relationship of yeast cell diameter to incubation temperature is suggested.

Several subpopulations of hepatocytes with increasing cell diameters were isolated, the smaller cells were attributed to the periportal area, the larger ones to the perivenous region. Profiles of total cytochrome P-450, benzphetamine N-demethylation and ethoxyresorufin O-deethylation, cytochrome c-reductase, glucose-6-phosphatase and GPT activities were determined. With adult hepatocytes an increasing cytochrome P-450 concentration with increasing cell diameter could be observed, paralleled by increasing activities of monooxygenases. Glucose-6-phosphatase and GPT also revealed increasing activities with increasing cell diameter, but cytochrome c-reductase did not show a distinct zonation. Immature hepatocytes (age 11–15 days) were smaller, more fragile, and could not be isolated with the same enzyme solution as adult hepatocytes. They did not show any zonation of cytochrome P-450 whereas the zonation of the monooxygenases was almost fully developed. For cytochrome creductase a zonation with higher activities in the perivenous cells could be demonstrated, in contrast to the lack of zonation in adult rats. Glucose-6-phosphatase showed a decline with increasing cell diameter in immature hepatocytes, whereas GPT did not show any zonation. In rats aged 20 days the zonation of these parameters in liver was in between younger and older animals.

Only at cell concentrations of less than 10 7 /ml are E. coli in steady state as defined by three intrinsic properties: mean cell diameter, cellular specific gravity and the concentration of β-galactosidase per cell. Such concentrations are below the range of turbidimetry.

This experiment was designed to study the kinetics of glycerol and dimethyl sulfoxide (DMSO) in cultured cells of human leukemia and lymphoma at 0°C and 37°C. Quantitative photographic measurement of changes of cell diameter was used as assay of relative permeability. Movement of DMSO was generally found to be more rapid than that of glycerol. Movement of both agents was found to be more rapid at 37°C than at 0°C. Changes in cell diameter was marked with glycerol than with DMSO. Equilibration time of DMSO, as assayed by change in cell diameter at 0°C was approximately 15 to 20 minutes as contrasted with 20-25 minutes for glycerol.

Summary1. Beyond an early age (about 3 weeks), the proportion of brown fat within the hamster maintains a relative constancy. In contrast, the ratio of white fat to body weight increases precipitously with age until full maturity of the hamster. 2. Cortisone treatment results in a prompt hypertrophy of brown fat in hamsters and mice, reflected microscopically by measurable expansion of cell diameter. White fat is possibly somewhat reduced in weight. 3. The reactive hypertrophy of brown fat in cortisone-treated hamsters diminishes with increasing age, apparently caused in part by the increasing numbers of unresponsive white fat cells within the borders of brown fat masses.

Treatment of Sarcoma 37 ascites cells with trypsin was found to be associated with a significant loss of dry mass which was unaccompanied by any appreciable change in the mean cell diameter or the viability of the cells.

Summary Red-cell indices, including the diameter/thickness ratio (D/T) derived from mean cell diameter (MCD) and mean cell volume (MCV), were determined in a study of 203 medical out-patients. A close correlation was found between D/T and MCH and between D/T and MCHC.

IN experiments for inducing heteroploidy in the Mammalia, it is of utmost interest to follow the chromosome picture of a treated animal through the developmental period from immediately after fertilization of the egg until adult age has been reached, or at least until sexual maturity. Beatty and Fischberg1 have described a method for obtaining mouse blastocysts for chromosome counts three and a half days after treatment of tubal eggs with cold- or hot-shock, that is, at the pre-implantation stage when the dividing cells usually contain large chromosomes. In rabbits it is most convenient to work with blastocysts at the age of 5–5½ days after copulation. At this age the diameter of the eggs is about 1–1.5 mm., but large variations are found. In older blastocysts, for example, six days old, it is often difficult to get good squash preparations due to the explosive breakup of the blastocysts, after which the different layers are difficult to spread out; although this can be done after some experience with a pair of needles. In two- to three-day old eggs, the individual cells are a little larger than from the fourth day, but the number of divisions is smaller. (This is a subjective view; no direct measurements of the cell diameter have been made.) The disadvantage in using blastocysts in studies of the chromosome number lies in the fact that it is very difficult to separate the trophoblast cells from the inner layer, and, so far as we know, nothing is known about the difference or variation in chromosome number from these different tissues. This work requires further examination.

The paper deals with the description of method, proposed by authors, that determining the essential geometric characteristics of the metal foam structure with using of the analytical imaging software. Method use economically available technical apparatus and software with emphasis on maximum consideration of the measurement uncertainty by Kline-McClintock method. The image analysis used three kinds of metal foams with a pore density of 10 to 40 pores per inch. The most important parameter - the size of a metal foam cell ranged from 1,165 mm (for 40 PPI) through a 2,262 mm (for 20 PPI) to 5,660 mm (for 10 PPI).

We perform a detailed analysis of the migratory motion of human embryonic stem cells in two-dimensions, both when isolated and in close proximity to another cell, recorded with time-lapse microscopic imaging. We show that isolated cells tend to perform an unusual locally anisotropic walk, moving backwards and forwards along a preferred local direction correlated over a timescale of around 50 min and aligned with the axis of the cell elongation. Increasing elongation of the cell shape is associated with increased instantaneous migration speed. We also show that two cells in close proximity tend to move in the same direction, with the average separation of m or less and the correlation length of around 25 μm, a typical cell diameter. These results can be used as a basis for the mathematical modelling of the formation of clonal hESC colonies.

The superior hydrodynamics of circular tanks over rectangular tanks are well known by aquaculturists; yet rectangular tanks are still widely used because of their easier handling. As a consequence, several studies have focused on the hydrodynamics of rectangular tanks, where rotating flow cells are generated by injecting water tangentially to the tank wall with the outlet placed in the centre of the cell. In the present work, we evaluate the hydrodynamics in a rectangular tank with 4 rotating flow cells of 1 m diameter, which is called multivortex tank. We also analyze baffle placement between two consecutive water inlets and the characteristics of the water inlet (flow rate and inlet velocity), which then allows us to determine the average velocities and the distribution uniformity of these velocities. The obtained results are compared with a circular tank having the same cell diameter and inlet configurations as the multivortex tank. Baffle placement between two consecutive water inlets in the multivortex tank helps increase the average velocity, the uniformity of velocities and the symmetry in the rotating flow cells. In configurations without baffles, the combination of low flow rate and high impulse force present the lowest symmetry. Differences between intermediate and extreme cells were observed. In all configurations tested, velocities and uniformities were higher in extreme cells than in intermediate cells. In the circular tank the average velocities achieved were higher than in the multivortex tank with the same impulse force, but the uniformity of velocities were higher in the multivortex tank. Finally, the proportionality between the average velocity and the square root of the impulse force for a specific tank geometry has been corroborated in commercial scale models.

The coarsening of a liquid foam inside a tube was experimentally studied. A bamboo structure develops in the foam and the number of bamboo segments per unit length of the tube was measured as a function of time for various tube diameters. The results are consistent with a power relation dα tn for the time dependence of the average cell diameter d and give n ≈ 0·54. The average length of a bamboo segment in the final bamboo structure was found to be very close to the tube diameter.

The authors describe a process for fabrication of magnetic recording media through formation of an alumite layer by anodic oxidation, and electrodeposition of iron in pores of the cells in the alumite. By varying the voltage and duration of the anodic oxidation, the cell diameter and porosity of the alumite layer can be regulated. Hard disk media were fabricated by this process, which can be applied to flexible disk production also.

The age of introduction of solid foods and its effect on energy intake, growth and adiposity during the first 3 years of life were studied in 92 healthy male infants from the Greater Philadelphia area. The first solid foods introduced to infant diets were cereals (70%), fruits (4%), and a combination of cereals and fruits (26%). Solids were started by 2 months of age in 48% of infants, by 4 months in 89% and by 6 months in 99%. The age of introduction to solids was decided with basis on physicians' recommendation (39%), mothers' decision (38%), relatives' advice (11%), and other factors (12%). Infants introduced to solids by 2 months of age as compared to others introduced to solid foods after 2 months had: 1) higher but not statistically significant energy intake at 6, 12 and 18 months of age; 2) higher energy intake at 36 months (mean ± SEM 1585 ± 93 vs. 1375 ± 95 Kcal/day, p < 0.1); 3) greater triceps (8.2 ± 0.4 vs. 7.4 ± 1.1, p

An air-borne and footstep noise insulating panel of synthetic resin foam is provided for floating floor pavements or floating wooden floors, said panel having in the interior thereof a multiplicity of voids extending normal or obliquely from one panel edge to the opposite panel edge. The panel preferably consists of a flexible closed-cell synthetic resin foam having a volume weight of 15 to 25 kg/m3, especially less than 20 kg/m3, having a cell diameter of less than 0.3 mm, and exhibiting good elastic recovery. The insulating panel has a dynamic stiffness, measured according to DIN 52214, of 1 to 13 MN/m3 and also possesses the required properties regarding long-term, burning, and insulating behavior.

Oospores and oogonia of P. dissotocum, P. myriotylum, P. irregulare, and one isolate of P. ultimum increased in diameter after being subcultured for 30 mo. Oospores and oogonia of P. aphanidermatum and one isolate of P. ultimum decreased in diameter during this period. Sporangia of P. irregulare increased in diameter and of two isolates of P. ultimum decreased in diameter during this period. The taxonomic value of reproductive cell diameter in the genus Pythium is discussed.

exposures (10 to 1500 R; 60Co). The survival following all doses of radiation decreased as the cell size increased. The exponential dose-survival curves for each of the five size classifications consisted of two components; the percentage of survival decreased with doses up to about 300 R but became flat and independent of the radiation exposure at higher doses. The level of the flat portion varied inversely with cell diameter, decreasing from about 68% survival for the smallest (4.9 microns) to 12% for the largest (10.4 microns) cells. These data suggest that, once thymocytes are lethally injured by radiation, the rate of degeneration is governed by the rate of physical and chemical processes within the cell; the speed of these processes increases as the cell size increases. The slopes of the dose-dependent component of the dose-survival curves were found to be similar for cells from 4.9 to 7.9 microns in diameter, but were two- and fourfold greater for larger cells, indicating an increased radiosensitivity among the large cells of the isolated population.