Allelic variation at the frizzled locus of Drosophila

The epidermis of Drosophila has a tissue polarity that is manifested by a parallel array of polarized structures (primarily hairs and bristles). The production of normal tissue polarity requires the function of the frizzled (fz) locus. We have isolated a large number of alleles at this locus and have phenotypically characterized more than 25 of them. We have found extensive allelic variation that a previous study failed to detect. Most of the alleles fall into a hypomorphic to amorphic series. Two alleles, however, have unusual properties. These alleles, which in general are moderately strong alleles, fail to produce a rough eye phenotype that is characteristic of all the other moderate or strong fz alleles. Thus, these two alleles are tissue specific in effect. Furthermore, these two alleles also have a neomorphic or antimorphic effect on hair polarity in one region of the wing.     

Cell kinetics simulation languages

The use of stochastic simulation languages in cell kinetics research is discussed. Two special purpose simulation languages; CELLSIM and CELLGROW are described and example problems are presented.     

Physical mechanisms by which low-frequency magnetic fields can affect the distribution of counterions on cylindrical biological cell surfaces

Effects of dc and low-frequency ac magnetic fields on the motion and distribution of counterions on surfaces of cylindrical biological cells are examined. Magnetic fields along the cell axis as well as perpendicular to it are considered. When a dc magnetic field of any physically realizable magnitude is parallel to the cell axis it has no effect on ion motion, since the resulting Lorentz force is much smaller than the counterion-to-ion attractive force. However a dc magnetic field perpendicular to the cell surface will distort any preexisting ion motion and the resulting current (i) perpendicular to the original motion will be much larger than any current induced by a low-frequency ac magnetic field of the same magnitude as the dc field and parallel to it. Nevertheless i will still be much smaller than the current i_o constituting the original ion motion since (i/i_o)=/, where is the ion cyclotron frequency and the effective counterion collision frequency. With no preexisting coherent ion motion (i_o=0) the circulating current induced by a sinusoidally time-varying magnetic field parallel to the cell axis will be well below thermal fluctuation noise as long as only a single cell is considered; however when even an infinitesimal exchange of ions between adjacent cells is assumed the magnetic field will cause a redistribution of counterions on the cell surface. The resulting steady-state distribution becomes independent of the frequency of the applied magnetic field () when , where is 1/2 of the relaxation frequency for counterion diffusion. On the basis of these results it is suggested that whenever modification of cell behavior in response to application of a low-frequency magnetic field is established, measurements of dielectric permittivity versus frequency of the cell preparation be performed. Redistribution of counterions on the cell surface would be a likely cause if the noted effect becomes independent of the frequency of the applied magnetic field above the counterion dielectric relaxation frequency. It is also suggested that in magnetic field exposure of cell preparations the size of the sample (e.g. diameter of Petri dish) and direction of the magnetic field relative to average cell orientation can critically affect experimental results.     

Effects of CuDIPS and tween 80 on SJL/J tumorigenesis

Plasma copper and zinc levels were measured in SJL/J mice, an inbred strain characterized by a high, spontaneous incidence of reticulum cell sarcoma (RCS). The changes with age in mean concentrations of these metals were consistent with a physiological response that is required for remission of neoplasia. Treatment of SJL/J mice with a copper complex, Cu(II)(3,4-diisopropylsalicylate)₂ (Cu 3,5-DIPS), dissolved in a 10% Tween 80-saline solution revealed a decrease in survival and decline in the incidence of RCS at 52 wk of age. The toxic effects of Cu 3,5-DIPS therapy appeared to be related to the intraperitoneal route of administration and to extracellular deposition of collagen. The inhibitory effect on tumor development was not related to Cu 3,5-DIPS. Rather, Tween 80 was found to be the factor of importance.     

Thermodynamic stability of proteins in salt solutions: A comparison of the effectiveness of protein stabilizers

The denaturation of proteins by guanidine hydrochloride was studied in the presence of different concentrations of stabilizing salts, namely potassium phosphate, ammonium sulfate, and potassium acetate. The denaturation transition was followed by observing changes in the peptide circular dichroism atpH 7.0 and 25°C. From these results the free energy of stabilization for the process native denatured was determined. It was found that the stabilizing power of the anions increased in the order acetate < sulfate < phosphate, in agreement with the anionic lyotropic series. Ribonuclease A, which is known to have a site that can bind either a phosphate or a sulfate ion, showed a larger stabilization by these anions than that for lysozyme, pepsinogen, and myoglobin.     

Relationship between oxygen and siderophore synthesis inPseudomonas aeruginosa

Pseudomonas aeruginosa strain PAO1, growing in low-iron medium, produces two siderophores, pyochelin and pyoverdin, in massive bursts as the culture shifts from logarithmic phase to stationary phase. Two medium components, oxygen and iron, prolonged the logarithmic phase when they were added to the medium. Oxygen and iron appeared to be in demand during this period because, as heme synthesis increased in response to the low oxygen concentration in the medium, a situation resulting from the high density of bacteria present in the medium during late log phase, the iron content of the bacteria decreased. These phenomena resulted in the production of massive amounts of siderophores late in the log phase to supply iron for the increased heme synthesis.     

Studies on Inc-P plasmids in Erwinia carotovora subsp. carotovora

Abstract Inc-P plasmids, RP4, R751, pMO850, and pRK2013 were transferred to Erwinia carotovora . These plasmids were stably maintained in E. carotovora and the transconjugants were efficient donors of respective plasmids to other strains of E. carotovora and Escherichia coli . These plasmids were not able to mobilize chromosomal markers from one strain of E. carotovora to another strain of E. carotovora even in the presence of homologous DNA sequences on the plasmid and the bacterial chromosome. The presence of Inc-P plasmid does not affect the pathogenic phenotype of E. carotovora . A broad host range Inc-P cosmid, pLAFR1, was transferred to E. carotovora with the help of pRK2013, suggesting the potential use of a binary plasmid system for genetic complementation in E. carotovora .     

Menstrual cycle patterns of hormones and sexual behavior in gorillas

Oppositely sexed pairs of gorillas were tested behaviorally during the menstrual cycle to determine the relationship between hormone concentrations of the female and the frequency of sexual activity by the pair. Five females were tested individually during two cycles with each of two males, but serum samples for hormone assay were obtained from each female only during the first cycle of testing. There was no clear relationship between hormones and behavior for the single cycle in which the serum samples were obtained, with the exception that no copulations occurred after the early luteal phase, when progesterone was greater than 5 ng/ml. Normalized behavioral data from all four test cycles for all pairs suggested that female-solicited copulations were restricted primarily to the periovulatory period. Male sexual initiative (by one of the males) accounted for most copulations temporally dissociated from the periovulatory period. Normalized hormone data for all of the females suggested that (1) attractivity was associated with estradiol concentrations during the follicular phase, (2) proceptivity with estradiol and testosterone at midcycle, whereas (3) receptivity was not associated with hormone patterns or cycle phase. The data suggest that hormones are one of several variables that contribute to the regulation of sexual behavior in gorillas.     

Microheterogeneity of bovine myelin basic protein studied by nuclear magnetic resonance spectroscopy

Myelin basic protein isolated from bovine white matter is known to consist of a mixture of three or more “charge isomers”, which can be separated by cation-exchange chromatography. We are using 360-MHz ¹H-nmr spectroscopy to establish the chemical and structural differences among them. Preliminary studies by difference spectroscopy between two of the isomers suggest (a) all aromatic residues, and probably their nearest-neighbors, are unchanged; (b) the less cationic isomer lacks one (or two) of its C-terminal Arg residues; and (c) a significant fraction of the two Met residues in the less cationic isomer is present as methionine sulfoxide.     

Study of Glial Fibrillary Acidic Protein in a Human Glioma Cell Line Grown in Culture and as a Solid Tumor

Abstract: A continuous human glioma cell line grown in culture and as a solid tumor was analyzed for glial fibrillary acidic (GFA) protein. This material provided a rich source for GFA protein that could also be manipulated and controlled. Immunoperoxidase staining at the light and electron microscopic levels revealed that the cell culture and tumor specimens were strongly positive for GFA protein. When aqueous soluble fractions of the cell culture and tumor were separated by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis, electroblotted onto nitrocellulose and stained immunochemically, they contained exclusively low molecular weight (41–43 K-dalton) GFA peptides. SDS (0.15%)-soluble fractions contained either low molecular weight only (culture) or a mixture of peptides ranging from 41 to 49K daltons. SDS (1%) extracts of either cell culture or tumor contained only 49K dalton GFA protein. Two-dimensional gel separation revealed that the GFA protein extracted from either the culture or tumor with 1% SDS resolved to two or three spots at pH 5.8. Low molecular weight GFA peptides (<49K daltons) in aqueous and 0.15% SDS-soluble extracts became increasingly more acidic with decreasing molecular weight. The extremely rapid degradation seen suggests that this cell line may be a valuable system for further study of intermediate filament protein turnover.