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J F Aronson

Publications and source records attributed to J F Aronson.

32 records · Page 2Linked to original sources
PubMed1981

Culture of epithelial cells from the rat pleura.

Cells obtained by tryptic digestion of the surface of intact adult and fetal Fischer 344 rat lungs were plated on glass fragments. Epithelial cell lines were readily established by selecting fragments with 2 to 10 cells 2 days after plating and growing them in F12 K media containing 10% fetal bovine serum (FBS). These cell lines and new lines that can be easily obtained a provide a reliable source of diploid, density-inhibited epithelial cells. These cells of mesothelial origin may serve as models for the study of mesothelial cells in situ.

Animals↗
PubMed1976

Initiation of lung cell proliferation by trypsin.

The ability of trypsin to initiate DNA synthesis in alveolar epithelial cells of mice was tested by introducing solutions containing trypsin into the lung. The concentrations tested ranged from 0.01 to 1.0 mg. per ml., the site of action was identified by adding colloidal carbon as a tracer, and chromosomal DNA synthesis was detected by autoradiography on the basis of strong nuclear incorporation of tritiated thymidine. In the above concentration range trypsin did not cause cell necrosis, general fragmentation of cell processes, or loss of mechanical contact at epithelial cell junctions. Edema and focal acute inflammation were apparent at concentrations of trypsin above 0.1 mg. per ml. In the alveolar epithelium maximal labeling was seen 2 days after treatment with 0.5 mg. per ml. of trypsin. At this time electron microscope autoradiography covering two "S" periods showed that one-third of the type II cells were labeled. No labeled type I cells were seen. Trypsin at levels less than 0.1 mg. per ml. did not increase the frequency of labeled type II cells above that of the saline-colloidal ink solution alone. Mesothelial cells lining the lung were stimulated by trypsin (0.5 mg.) given intrapleurally. The frequency of mesothelial cell labeling peaked at 2 days with a labeling index for a single tritiated thymidine pulse of 18 per cent. Neither alveolar type II cells nor mesothelial cells showed increased labeling when trypsin inactivated by diisopropyl fluorophosphate was used.

Animals↗
PubMed1973

Nuclear membrane fusion in fertilized Lytechinus variegatus eggs.

Fusion of apposed nuclear envelopes is frequently seen at telophase during postmitotic reorganization of the nucleus, but only rarely at other times in the cell cycle. We attempted to define an experimental system for studying changes in the nuclear envelope related to the cell cycle by varying the time of pronuclear apposition in fertilized Lytechinus variegatus eggs. This approach was based on the assumption that the period from fertilization to metaphase of the first cleavage division corresponds to the period from telophase to metaphase in the generalized cell cycle. The experimental approach used was to block the movement of the pronuclei with Colcemid and then to release this block at varying times after insemination by photochemically inactivating the Colcemid. The results show that apposed pronuclear envelopes can fuse from soon after insemination until the anticipated time of prometaphase. Fusion occurred in about 3 min as scored by light microscopy and this time did not vary significantly with the time after insemination. The potential for nuclear fusion is not restricted to pronuclei alone since diploid nuclei in binucleate cells could be fused using centrifugation in solutions of Colcemid to bring the nuclei into apposition. It is suggested that the potential for nuclear fusion is not necessarily related to the cell cycle and that modification of the nuclear envelope, possibly by association with chromatin or other fibrous material restricts nuclear fusion in most multinucleated cells.

Animals↗
PubMed1967

Polarized light observations on striated muscle contraction in a mite.

Contraction of individual sarcomeres within the living mite Tarsonemus sp. was observed by polarized light microscopy. In unflattened animals the usual range of contraction was such that the minimum sarcomere length approximated the length of the A region, and the maximum sarcomere length was about twice the length of the A region. The central sarcomeres of the dorsal metapodosomal muscles were observed in detail. The A band length increased slightly with increasing sarcomere length since the regression of I region length on sarcomere length had an average slope of 0.91. When the A band length in a sarcomere which was shortening was compared with the length when the same sarcomere lengthened, no significant difference was seen. The A band of each sarcomere seemed to act as a not too rigid limit to further shortening; this agreed with the reversible shortening of a muscle in which the A band had been experimentally shortened. An H region was visible at long sarcomere lengths and was not visible at short sarcomere lengths, even when the muscle was actively shortening. The rate of change of H region length with sarcomere length suggested that I filament length may increase as sarcomere length increases. Despite this effect and the small increase in A length with sarcomere length, the results are considered to be consistent with a model in which shortening occurs by the relative movement of A and I filaments, with little or no change in length of either set of filaments. Sarcomere shortening was clearly associated with an increase in the retardation of the A region.

Animals↗
PubMed1966

A melting point for the birefringent component of muscle.

The A filament of the striated muscle sarcomere is an ordered aggregate of one or a few species of proteins. Ordering of these filaments into a parallel array is the basis of birefringence in the A region, and loss of birefringence is therefore a measure of decreased order. Heating caused a large decrease in the birefringence of glycerinated rabbit psoas muscle fibers over a narrow temperature range ( approximately 3 degrees C) and a large decrease in both the birefringence and optical density of the A region of Drosophila melanogaster fibrils. These changes were interpreted as a loss of A filament structure and were used to define a transition temperature (T(tr)) as a measure of the stability of the A region. Since the transition temperature was sensitive to pH, ionic strength, and urea, solvent conditions which often affect protein structure, it is an experimentally useful indicator for factors affecting the structure of the A filament. Fibers from glycerinated frog muscle were less stable over a wide pH range than fibers from glycerinated rabbit muscle, a fact which demonstrates a species difference in structure. Glycerinated rabbit fibrils heated to 70 degrees C shortened to about 40% of their initial length. The extent of shortening was not correlated with the loss of birefringence, and phase-contrast microscopy showed that this shortening occurred in the I region as well as in the A region. This response may be useful for studying the I filament and actin in much the same way that the decrease in birefringence was used for studying the A filament and myosin. The observations presented show that some properties of muscle proteins can be studied essentially in situ without the necessity of first dispersing the structure in solutions of high or low ionic strength.

Animals↗
PubMedDate not supplied

Human fetal lung fibroblasts: observations on origin and stability in culture.

The loosely associated lung mesenchymal cell found between the ducts of the 3-to 4-month fetus is considered to be the probable progenitor of lung fibroblast cultures and of alveolar interstitial cells. A possible stage- and tissue-specific property of this cell type, the reduction of cortisone to cortisol, is defined and its activity studied in a variety of cell lines. Fibroblast lines derived from both fetal and adult lung had about ten times the cortisone-reducing activity of corresponding skin fibroblast lines. This relatively high activity was also characteristic of cell lines established by cloning the initial fetal lung digest. Lines established from developmentally related esophagus and from trachea had less activity than corresponding lung fibroblasts. A high level of cortisone-reducing activity was maintained in four serially passaged lung fibroblast lines for at least 85% of the proliferative life span and a second cell property, the enhancement of this activity by pretreatment with cortisol, was also maintained in three of the four lines.

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