Growth and death rates of bovine embryonic kidney cells in turbulent microcarrier bioreactors

Bead-bead collisions have been characterized using the velocity of the smallest turbulent eddies to calculate a turbulent collision severity (defined as the energy of collisions times their frequency), but a shear-based collision mechanism with a different dependence on the system variables is also applicable. This shearbased mechanism and the ratio of smallest eddy size to microcarrier diameter can explain the beneficial effects of both smaller diameter microcarriers and higher viscosity of the medium on the growth rate of bovine embryonic kidney cells. Death rates of these cells have also been measured at several levels of agitation. The decrease in apparent growth rate from increasing agitation is caused both by a higher rate of cell death as well as a lower intrinsic growth rate.List of Symbols B unspecified biological variable - d cm bead diameter - d _i cm impeller diameter - e error in estimate of power number - F _n , F _s (g·cm)/s² normal and shear forces on a cell - Fr Froude number - g 980cm/s² acceleration of gravity - k k^–1 first order death rate constant - m g mass of a bead - n s^–1 impeller rotational rate - n _b number of impeller blades - N _p impeller power number - R _i cm impeller leading edge radius - TCS (g·cm²)/s³ turbulent collision severity - V cm³ reactor volume - v _br cm/s rms relative velocity between beads - v _e cm/s velocity in smallest eddies - X number of cells/cm₃ cell population Greek Symbols volume fraction microcarriers - s^–1 shear rate - cm²/s³ turbulent power dissipation rate - cm size of smallest eddies - g/(cm·s) dynamic viscosity - h^–1 apparent growth rate of cells - ₀ h^–1 intrinsic growth rate of cells in absence of death - v cm²/s kinematic viscosity - _b g/cm³ bead density - _f g/cm³ fluid density - g/(cm·s²) shear stress     

A mutation in aspergillus nidulans that blocks the transition from interphase to prophase

In order to develop a method for obtaining mitotic synchrony in aspergillus nidulans, we have characterized previously isolated heat-sensitive nim mutations that block the nuclear division cycle in interphase at restrictive temperature. After 3.5 h at restrictive temperature the mitotic index of a strain carrying one of these mutations, nimA5, was 0, but when this strain was subsequently shifted from restrictive to permissive temperature the mitotic index increased rapidly, reaching a maximum of 78 percent after 7.5 min. When this strain was examined electron-microscopically, mitotic spindles were absent at restrictive temperature. From these data we conclude that at restrictive temperature nimA5 blocks the nuclear division cycle at a point immediately preceding the initiation of chromosomal condensation and mitotic microtubule assembly, and upon shifting to permissive control over the initiation of microtubule assembly and chromosomal condensation in vivo through a simple temperature shift and, consequently, nimA5 should be a powerful tool for studying these processes. Electron-microscopic examination of spindles of material synchronized in this manner reveals that spindle formation, although very rapid, is gradual in the sense that spindle microtubule numbers increase as spindle formation proceeds.     

Water Permeability during Tomato Fruit Development in Normal and rin Nonripening Mutant

This work tested one aspect of the relations between membrane permeability and fruit ripening. Membrane permeability was measured as [³H]water efflux rate from preloaded fruit pericarp disks. Different stages of fruit development were compared between two tomato (Lycopersicon esculentum Mill) strains: the normal Rutgers and the isogenic nonripening rin strain. The first significant increase in permeability was measured in Rutgers tissue at 110% of development, after fruit ripening had already begun as indicated by ethylene and CO₂ evolution and lycopene synthesis. The rin did not show any increase in tissue permeability during fruit development or maturation.     

The Influence of Auxin and Ethylene on Chromatin-directed Ribonucleic Acid Synthesis in Soybean Hypocotyl

Soybean seedlings treated with ethylene exhibited small increases in ribonucleic acid content in the elongating section of the hypocotyl. Chromatin isolated from the elongating section of ethylene-treated seedlings showed a 35 to 60% increase in the capacity for RNA synthesis. The ethylene-induced response was saturated at 1 microliter/liter of ethylene and was fully expressed after 3 hours. Auxin caused marked accumulation of RNA and DNA in the elongating and basal tissue of the hypocotyl. Chromatin isolated from these auxin-treated tissues showed an 8- to 10- fold increase in RNA synthetic capacity as measured in vitro. Ethylene added with auxin reduced the auxin enhancement of nucleic acid synthesis in the elongating and basal tissues. Both ethylene and auxin treatment of the seedlings inhibited nucleic acid accumulation and chromatin activity in the apical tissue. Ethylene did not appear to mediate the auxin effects on nucleic acid synthesis in soybean hypocotyl with the possible exception of inhibition in the apical tissue.     

Salmonellae as an Index of Pollution of Surface Waters

Screening enrichments of surface water specimens by means of a polyvalent fluorescent antibody reagent for the salmonellae yielded approximately 60% more positive specimens than was obtained by cultural procedures. It is not known what fraction of the excess of fluorescent antibody-positive over culturally positive specimens represents staining of non-salmonellae or non-arizonae as opposed to the staining of non-cultivatable organisms of these two genera. Cotton gauze and rayon-polypropylene fiber swabs were equally sensitive for collecting salmonellae from the streams examined. Tetrathionate enrichment incubated at 41.5 C appeared to be superior to selenite-cystine for isolation of salmonellae from surface waters. Twenty-eight serotypes of Salmonella and two serotypes of Arizona were identified in the 121 positive specimens. In water rated moderately polluted, 65% of all specimens tested were positive; in minimally polluted waters, 38% were positive; and in unpolluted streams, 44% were positive.     

RNA synthesis and the germination of light-sensitive lettuce seeds

Summary The germination of lettuce seeds is inhibited by the nucleotide base analogue 6-methylpurine. RNA synthesis has been measured during imbibition and germination as ³²P-phosphate incorporation into RNA species as fractionated by polyacrylamide gel electrophoresis. Seeds were surface sterilized and imbibed in the presence of various antibiotics. RNA preparations from lettuce seeds were coelectrophoresed with ³H-RNA prepared from bacteria to check for bacterial contamination of the seeds. There is a much higher rate of RNA synthesis in illuminated, germinating seeds as compared to dark, non-germinating seeds. This difference does not develop until after 12 hours of imbibition at 27°, which is the time of onset of germination and radicle growth.This investigation was supported by a contract from the United States Department of Agriculture (No. 616-15-3). Journal paper of the Purdue Agriculture Experiment Station.     

Evaluation of statistical methods for avoidance data of schooling fish

Concentrations of heavy metals blends avoided by schools of fathead minnows and alkaline pH levels avoided by schools of bluegill sunfish, fathead minnows, golden shiners, and rainbow trout were determined in a boundary layer avoidance chamber. Parameters measured were residence time, activity, and sequential fish location counts. Data were evaluated using linear, quadratic, and polynomial regression, log₁₀ transformations, analysis of variance, covariance analysis, Duncan's multiple range test, and Hochberg's GT2 test. The best methods of analysis are quadratic regression and covariance analysis.     

Photoperiodic stimulation of pubertal development in male deer mice: involvement of the circadian system

Pubertal development in prairie deer mice (Peromyscus maniculatus bairdii) is accelerated by exposure of juveniles to a long-day photoperiod, and, conversely, retarded by exposure to short days. The purpose of the present study was to evaluate the possible involvement of the circadian system in the photoperiodic regulation of puberty. Weanling males, previously housed on a short-day light cycle of 6L:18D, were subjected to a "resonance" protocol in which they received one of the following light cycles: 6L:18D, 6L:30D, 6L:42D, 6L:54D, or 16L:8D. Post-weaning exposure to cycles of 16L:8D, 6L:30D, and 6L:54D stimulated reproductive organ growth as measured at 6 weeks of age. Exposure to cycles of 6L:18D and 6L:42D failed to stimulate reproductive development. These data support the hypothesis that young male deer mice use a circadian rhythm of responsiveness to light to measure photoperiodic time and, consequently, regulate pubertal development.     

Isolation of Legionella pneumophila from Cooling Tower Water by Filtration

Methods are described for detection of Legionella pneumophila in cooling tower water or other water sources by direct fluorescent-antibody staining. A procedure for isolation of Legionella bacteria from water samples by guinea pig inoculation is described. Two different serogroups of L. pneumophila were isolated repeatedly from one of the cooling towers.     

Characteristics of environmental isolates of Legionella pneumophila.

Thirty-eight cultures of Legionella pneumophila isolated from surface waters were characterized by their morphological, tinctorial, biochemical, and serological properties and by their ability to produce disease in guinea pigs. Their susceptibility to antimicrobial agents also was tested. When they were compared with clinical isolates, no important differences were found between cultures from the two sources. Sodium hippurate hydrolysis, gelatin liquefaction, pigment formation, and beta-lactamase and alkaline phosphatase activity were useful in differentiating the four described species of Legionella. Hydrolysis of diacetylfluorescein and the inability to reduce nitrate help to distinguish Legionella species from other gram-negative bacterial rods.