Electron microscopic observations on the reactional changes occurring in insect nerve fibers after transection

Summary An electron microscopic study of the interganglionic connectives of an orthopteran (Laplatacris dispar) demonstrated that a reaction starts in the sectioned fibers very soon after transection (30 minutes). This reaction is closely similar to that observed in sectioned nerves of vertebrates and consists in the appearance of microvesicles and the proliferation of mitochondria. Sectioned connectives were studied from 30 minutes to 88 hours after section. The reaction mentioned increases progressively during the indicated lapse of time.This research was supported by the United States Air Force under Contract No AF 49 (638) 585 and Grant Af 61-64, monitored by the Air Force Office of Scientific Research, Air Force Research Division of the Air Research and Development Command.     

Studies on the transformation of rat embryo cells of low passage by carcinogenic fluorenylhydroxamic acids and their acetate esters

Summary Rat embryo cells of low passage subjected to a single treatment with certain carcinogenic fluorenylhydroxamic acids and their respective acetate esters showed signs of transformation in vitro, such as changes in phenotype, growth in soft agar and agglutination with concanavalin. A. In addition, certain changes in karyotype and loss of diploidy were observed. There was no evidence, either by electron microscopy or by assay of RNA-dependent DNA polymerase, for the presence of virus. None of these cell lines produced tumors after inoculation into the isologous host. The results of this study lead us to suggest that malignant transformation is a multistep process and that certain criteria of transformation of rat embryo cells are associated with the initial stage(s) in which the cells are transformed without being tumorigenic. The ultimate test for malignant transformation of rat embryo cells remains the production of tumors in a susceptible host after inoculation of treated cells. Supported by Grant CA-02571 from the National Cancer Institute (H. R. Gutmann) and by Grant CA-08832 from the National Cancer Institute (G. J. Vosika).     

Feline sarcoma virus induced in vitro progression from premalignant to neoplastic transformation of human diploid cells

Summary Human diploid cells morphologically transformed by feline sarcoma virus were serially propagated under selective cell culture conditions. When injected into nude mice prior to passage in soft agar (0.35%), morphologically transformed cells did not produce tumors. However, when propagated under selective cell culture conditions, transformed cells grew in soft agar and, when injected subcutaneously into the subcapsular region of the nμ/nμ mice, produced neoplastic nodules histopathologically interpreted as fibromas. Karyological examination of cell populations grown out from the tumors confirmed that the tumors were composed of human cells. Examination of electron micrographs of the excised tumor tissue revealed the presence of budding virus particles. Tumor cells isolated from nude mice and morphologicaly transformed cells both contained the feline concornativirus-associated cell membrane antigen. It was concluded that expression of feline oncornavirus-associated cell membrane antigen is associated with an early stage of feline rerovirus-induced carcinogenesis, namely focus formation. In addition, it was shown that FeLV-FeSV can induce morphological transformation in human cells in vitro and that there is a requirement for the cells to passage through soft agar before subsequent tumor formation (neoplastic transformation) can be demonstrated. This work was supported in part by NIH-NCI RO1-259007, NO1-CP-3571 and CPV08 103563, and Air Force F49620-77-C-110.     

Characteristics of rat normal mammary epithelial cells and dimethylbenzanthracene-induced mammary adenocarcinoma cells grown in monolayer culture

Summary The characteristics of normal mammary epithelial and 7,12-dimethylbenz[a]anthracene (DMBA)-induced adenocarcinoma cells derived from rats and grown in monolayer culture were compared. Normal mammary epithelial cells exhibited different morphology and agglutinability by plant lectins, slower growth rate, and lower saturation density and cloning efficiency. In addition, the normal cells were sensitive to the toxic effect of DMBA, and were unable to grow in soft agar or to form tumors, when inoculated into newborn Sparague-Dawley rats. The converse was true in each case for the adenocarcinoma cells. Supported by Public Health Service Research Grant CA 01237603 from the National Cancer Institute Portions of this paper were presented at the 65th Annual Meeting of the American Association for Cancer Research at Houston, Texas, 1974.     

Chromosome analyses and anchorage-independent growth of SV40-induced morphologically transformed epithelial cells from amniotic fluids

Summary Epithelial cells from amniotic fluid cell cultures are morphologically transformed by simian virus 40, 20 to 30 d after infection. The cells of the transformed colonies are highly basophilic, have a high nuclear-to-cytoplasmic ratio, and show a dense growth pattern. The cells are virus producers, and ultimately, after continuous passage, the cell lines reach a crisis situation with no growth. Twelve morphologically transformed cell colonies were isolated from five different individuals for chromosome analyses after approximately 18 population doublings (second bottle passage). For all cell lines diploid cells were observed. Banding of the chromosomes revealed normal morphology of euchromatic and heterochromatic regions. The suggestion is made that chromosome alteration is not necessary, nor a prerequisite, for the morphologically transformed phenotype to be expressed and that the transformation process per se causes chromosomal instability. Tests for colony formation of the 12 cell lines in semisolid medium showed that different transformed colony isolates from the same individual donor of the cells either formed or did not form colonies in agar. The size of the colonies was also consistent within individuals as compared to between individuals. These limited results are suggestive of a dependence upon the genetic constitution of the individual donor of the cells for colony formation in soft agar. Supported by National Science Foundation Grant PCM77-15876.     

An avoidance learning situation. A neural net model

A simple avoidance situation is considered in terms of a neural net learning model. Data for the control situation can be represented by an expression having three parameters which determine the initial and the steady state activities together with the transient aspects. The introduction of a learning parameter then allows one to calculate satisfactorily the results obtained in the experimental situation in which shock is applied. This research was supported in part by the United States Air Force through the Air Force Office of Scientific Research of the Air Research Development Command under Grant No. AF AFOSR 370-63 and in part by the United States Public Health Service Grant RCA GM K6 18,420.     

Ducts of the rat pancreas in agarose matrix culture

Summary Interlobular and intralobular ducts isolated from the pancreas of the rat by digestion with collagenase and chymotrypsin were cultured in an agarose matrix containing CMRL-1066 supplemented with insulin, dexamethasone,l-glutamine, soybean trypsin inhibitor, antibiotics, and fetal bovine serum. The cut ends of most interlobular ducts sealed to create encolosed lumina. Some ducts retained their original cylindrical organization; others enlarged to varying degrees, resulting in structures that ranged from cylindrical to spherical in shape. The duct walls consisted of viable epithelium and connective tissue, although the amount of connective tissue declined with age. Both epithelial and connective tissue cells became flattened in the enlarged ducts. Intralobular and small interlobular ducts often remained associated with the larger interlobular ducts. These duct fragments have been cultured for as long as 6 weeks. This study was supported by National Cancer Institute Grant CA 19177 through the National Pancreatic Cancer Project and by Biomedical Research Support Grant RR 07196 from the Division of Research Resources, National Institutes of Health.     

Keratinization and the effect of vitamin A in aggregates of a squamous carcinoma cell line NBT II

Summary The terminal differentiation, keratinization, of a rat bladder tumor cell line, NBT II, occurred in multicellular aggregates. After aggregation, these cells did not undergo a round of mitosis before keratinization. 5-Bromodeoxyuridine added to the monolayer cell culture 2 days before aggregation completely prevented this differentiation; it was ineffective when added at the time of cell aggregation. Vitamin A prevented the keratinization of NBT II cells in aggregates but did not inhibit aggregate formation; it enhanced the number of cells engaged in DNA synthesis. This model appears to be very useful for analyzing the mechanisms of terminal differentiation and its modulation by vitamin A in tumor cells. This research was supported by Institutional Research Grant 731-01-E from the American Cancer Society and in part by Research Grant CA 14137 from the National Cancer Institute to Dr. J. Leighton.     

Electron microscope study of the developing nerve terminals in the acoustic organs of the chick embryo

Summary The stages of growth of the acoustic pathway (peripheral branch) were studied with the electron microscope in serial sections of the acoustic organs of 3 to 7 day chick embryos.Migration of cells from the acoustic epithelium was found at three days of incubation. These cells are presumably the futur ganglion cells. Fascicles of nerve fibers penetrate the epithelium through gaps of the basement membrane at 4–5 days of incubation. A dilatation develops in the intraepithelial fibers at about six days and thin and long prolongations grow from these dilatations and distribute among the cells. In the course of the next day the fibers embrace the foot of the sensory cell and the prolongations become shortened. Many of these extensions are charged with vesicles. At this stage (seven days) specialized structures (synaptic bars) differentiate in the region of the sensory cell contacting the large nerve ending (calix) or its short extensions. Each cell may show several synaptic bars, and each prolongation may contact with more than one cell.Research sponsored by the Air Force Office of Scientific Research, Office of Aerospace Research, United States Air Force, under AFOSR Grant Nr. 313-67.     

A new traveling-wave solution of Fisher's equation with density-dependent diffusivity

A new traveling-wave solution of Fisher's equation is found when the diffusivity is taken to be a smoothed step function of the dependent variable. The form of the solution and a necessary relationship between the traveling wave's speed and the diffusivity are predicted. This is done using flux continuity considerations in the limit when the diffusivity is piecewise constant. The predicted form is verified by numerical integration of the equation with a slightly smoothed step function diffusivity.Work performed under the auspices of the US Army Research Office (Durham), Contract DAAL03-89-K-0014; the National Science Foundation, Grant DMS87-06642; and the Air Force Office of Scientific Research, Grant AFOSR-88-0269     

On the number of phenotype structures in genetic systems

Phenotype structures in genetic systems are carefully defined in an abstract setting so that a considerable amount of enumerative theory can be brought to bear on the problem of enumerating them. Recent results can be used to simplify the computations, and a natural correspondence is suggested which changes the problem of finding the number of phenotype structures to the problem of determining the numbers of certain graphs with colored points. Work supported in part by a grant from the National Science Foundation. Work supported in part by Grant 73-2502 from the Air Force Scientific Research.     

On visual adaptation: I. Photochemistry

Quantitative aspects of the photochemistry of visual adaptation are considered. A simplied model is given that fits data on changes of rhodopsin concentration during and following strong illumination. A variation on Wald’s compartment hypothesis is shown to fit the quasilinear dependence of log threshold upon pigment concentration. Finally, there is a brief review of pertinent data on cone pigments. This research was supported in part by the United States Air Force through the Air Force Office of Scientific Research of the Air Research Development Command under Contract No. AF(638)-414, and in part by the United States Public Health Service Training Grant 2G-833.     

Conduction in demyelinated axons—A simplified model

This paper is concerned with conduction of the nervous impulse in a myelinated axon and the effect of demyelination on conduction characteristics. A model of nerve conduction called the “gunpowder fuse” model is presented which accurately predicts conduction velocities in both myelinated and unmyelinated nerves. The effect on conduction velocity in this model by reducing myelin thickness is examined by utilizing basic data and building and equivalent circuit. The result is a curve relating reduced conduction velocity to reduced myelin thickness. A similar analysis and resultant curve is derived from a saltatory conduction model. Supported in part by National Multiple Sclerosis Society Research Grant No. 516 and Air Force Grant AFOSR 669-67.     

Detection of anaerobic mycoplasmas in cell cultures

Summary A commercially available anaerobic generator and incubation system that develops a low oxidation-reduction potential was used for the assay of cell cultures for mycoplasmal contamination. Mycoplasma broth and agar media supplemented with dextrose, yeast extract, and horse serum were used. This system supported growth of some mycoplasmas that failed to grow in incubators with 5% CO₂ in nitrogen previously used in culture of mycoplasmas in this laboratory. This work was supported by a grant from the John A. Hartford Foundation General Research Support Grant No. 5 SO1 RR05582-4 from the National Institutes of Health, and by a Grant-in-Aid Contract from the State of New Jersey.     

Cell transformation by viruses

Summary This paper describes some current work pertaining to transformation of cells by oncogenic viruses. Part I includes: (1) the effect of a deoxyribonucleic acid (DNA) tumor virus (SV40) on the antigenic characteristics of transformed cells; (2) in vitro and in vivo methods of detecting virus-specific surface antigens; (3) the role that the host cell may play in the expression of virus-coded antigens; and (4) the presence of virus-induced antigens as a possible mechanism of the apparent nononcogenicity of certain virus variants. Part II discusses (1) the physicochemical properties of the nucleic acid of a ribonucleic acid (RNA) tumor virus-the Moloney sarcoma-leukemia virus (MSV-MLV) complex —(2) a preliminary analysis of viral RNA replication in cells transformed by MSV-MLV, and (3) application to human tumors. Supported in part by Research Grant CA 04600 and by Research Contract PH 43-68-678 within the Special Virus-Cancer Program, National Cancer Institute, National Institutes of Health. Recipient of Research Career Development Award 5-K3-CA 38,614 from the National Cancer Institute, National Institutes of Health     

Growth responses of barley seedling to simulated weightlessness induced by two-axis rotation

Summary A device used for simulated weightless studies is described and is called the Nogravatron. The Nogravatron apparatus produces simulated weight-lessness by rotating seedlings simultaneously at the rate of 0.25 rpm and 1.0 rpm in two axes perpendicular to each other. Atlas barley seedlings grown on the apparatus grew at rates different from that of stationary controls. Coleoptile elongation in rotated barley was not inhibited by light during the first 55 hours of rotation treatment whereas stationary controls were photoinhibited. After 55 hours the growth of rotated coleoptiles was inhibited by light. The coleoptiles did not show movements and were oriented along the longitudinal axis of the seed. Roots also did not show geotropic movements but the growth direction was affected by the proximity of other roots. Coleoptiles rotated in dark were significantly longer than stationary controls on the third and fourth day but not so on the fifth day and later. Coleoptiles rotated in light were about 35 percent longer than the stationary coleoptiles by the third day and maintained this significant difference to the end of the experiment.Supported in part by NASA Grant NsG 538-63 and by Air Force Office of Scientific Research Office of Aerospace Research, United States Air Force, Contract No. AF 49 (638)-1387.     

A neural net model for escape learning

An escape learning situation is discussed in terms of a neural model in which a stimulus can result in a conditioned excitement and a specific conditioned response. By using the simplest relations between the strengths of conditioning and the number of reinforcements and by introducing a distribution of fluctuations occurring regularly in time, one can calculate the probabilities of various responses, as well as the various latencies, in successive trials. The results are in moderately satisfactory agreement with the data of R. L. Solomon and L. C. Wynne (Psychol. Monogr.,67, No. 4, 1953). Consequences of the model for various experimental situations are discussed. This research was supported in part by the United States Public Health Service Grant RCA GM K6 18,420 and in part by the United States Air Force through the Air Force Office of Scientific Research of the Air Research Development Command under Grant No. AF AFOSR 370-64.     

Stochastic models for subpopulation emergence in heterogeneous tumors

A stochastic analog to a deterministic model describing subpopulation emergence in heterogeneous tumors is developed. The resulting system is described by the Fokker-Planck or forward Kolmogorov equation. A finite element approach for the numerical solution to this equation is described. Four biological and clinical scenarios are simulated (emergence of heterogeneity, exclusion of a subpopulation, and induction of drug resistance in both pure and heterogeneous tumors). The results of the simulations show that the stochastic model describes the same basic dynamics as its deterministic counterpart via a convective component, but that for each simulation a distribution of tumor sizes and mixes can also be derived from a diffusive component in the model. These distributions yield estimates for subpopulation extinction probabilities. The biological and clinical relevance of these results are discussed. Research support provided in part by ACS Grant IN45-Z and ACS PDT 243 B. Research support provided in part by the National Science Foundation under NSF Grant MCS-8504316, and by the Air Force Office of Scientific Research under Contract F49620-86-C-0111.     

On visual adaptation: II. The electroretinogram and the bipolar cells

First a model for theb-wave of the electroretinogram is given. The essential part of the model is the diffusion into the rod-bipolar synapse of a transmitter substance, followed by the induction of an inhibitor. Making use of this model, adaptation to an illumination too weak to cause of significant decrease in the concentration of visual pigment is interpreted as due to a decreased effectiveness of the rod impulse in exciting the bipolar cell. The disparity between threshold changes for very small test spots and for relatively large spots is explained simply, without invoking any additional physiological mechanisms. This research was supported in part by the United States Air Force through the Air Force Office of Scientific Research of the Air Research Development Command under Contract No. AF(638)-414 and in part by the United States Public Health Service Training Grant 2G-833.     

Body weight decreases in some proton exposed primates

ImmatureMacaca mulatta were exposed to varying doses of whole body irradiations utilizing 2 MeV X-rays; 55, 138 and 400 MeV protons; and 2.3 GeV protons. Over 200 primates remain in a life-long study of space type irradiation effects. Mean body weight decreases as a function of age, sex, dose and irradiation type have been found in the 55 MeV proton exposed group but not in the other groups. The cause of the decreased weights is unknown at iresent, as is the reason for the lack of this effect in the more penetrating irradiations.The animals involved in this study were maintained in accordance with theGuide for Laboratory Animal Facilities and Care as published by the National Academy of Sciences — National Research Council.The research reported in this paper was conducted by personnel of the Radiobiology Division, USAF School of Aerospace Medicine, Aerospace Medical Division, AFSC, United States Air Force, Brooks AFB, Texas. Further reproduction is authorized to satisfy the needs of the U.S. Government.