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Biomedical subjects

J J Eppig

Publications and source records attributed to J J Eppig.

At least 127 records · Page 7Linked to original sources
PubMed1978

An epithelial cell line with chronic polyoma infection established from a spontaneous mouse pancreatic adenocarcinoma.

The establishment of an epithelial cell line from a mouse pancreatic adenocarcinoma is described. The cell line, designated LTPA, was aneuploid and exhibited many transformed growth properties (rapid growth rate, failure to show density-dependent inhibition of growth, ability to grow in defined medium). A type C oncornavirus was isolated from the culture medium, and electron microscopy also revealed the presence of intracisternal type A particles. LTPA cells carried a persistent polyoma infection which produced only low levels of cytopathic effects. A mycoplasmal contamination was also carried. When injected s.c. into Swiss nu/nu mice, LTPA cells formed ductular structures which were destroyed by inflammatory reactions within 3 weeks.

Adenocarcinoma↗
PubMed1977

Exocrine pancreatic insufficiency syndrome in CBA/J mice. II. Biochemical studies.

Premature activation of proteolytic zymogens (trypsinogen, chymotrypsinogen) as an early step in the pathogenesis of exocrine pancreatic insufficency (EPI) syndrome in CBA/J mice was investigated in electrophoresed pancreatic homogenates. Polyacrylamide gels containing extracts from control pancreas required prior activation of trypsinogen and chymotrypsinogen (with exogenously added enterokinase and trypsin, respectively) to produce activity staining with specific synthetic substrates. On the contrary, bands of activity staining in gels containing homogenates from mice with EPI syndrome could be readily detected without trypsin or enterokinase preincubation. Subcellular fractionation of control and diseased pancreas revealed that the premature intracellular proteolysis was confined to the zymogren granule fraction, which, even in very moderately affected pancreases (10 to 30% acinar cell autolysis), was very labile in vitro. These proteolytic events reflect the biochemical consequences of zymogen granule destabilization that were observed at the ultrastructural level.

Animals↗
PubMed1977

Exocrine pancreatic insufficiency syndrome in CBA/J mice. Ultrastructural study.

The pathogenesis of a spontaneously occurring exocrine pancreatic insufficiency (EPI) syndrome in CBA/J mice was studied at the ultrastructural level. Initial cytologic manifestations of this syndrome are seen as a progressive digestion of the zymogen granules, beginning at the periphery and proceeding toward the granule interior. Granule membrane breakdown, fusion of neighboring granules, and a release of zymogen contents into the cytoplasm are frequently observed in later stages; in some cases the entire granule contents appear digested before membrane breakdown is observed. In either case, pathologic changes are subsequently observed in mitochondria and rough endoplasmic reticulum. Remnants of lysed cells are then engulfed by invading macrophages, and infiltration by fat cells is observed. Secretory ducts and islets of Langerhans show no pathologic changes even after total autolysis of the exocrine pancreas. Morphologic evidence showing zymogen granule destabilization, coupled with biochemical evidence presented in an accompanying paper, indicate that intracellular autodigestion is the mechanism of exocrine cell death.

Animals↗
PubMed1976

Protein labelling patterns in oocytes of Xenopus laevis.

Soluble and microsomal proteins synthesized at various stages of oogenesis in Xenopus laevis were compared by 3H and 14C dual-isotope labelling with subsequent mixing and analysis on sodium dodecyl sulfate (SDS)-polyacrylamide gels. The results indicated that the proteins labelled in all the stages of oogenesis studied are remarkably similar. However, the patterns in the small and medium-sized oocytes are more similar to one another than to the patterns characteristic of large oocytes. The greatest differences were found when comparing the microsomal proteins. The labelling patterns of oocyte proteins in vitro were not significantly different from the in vivo patterns for the stages of oogenesis studied. These results indicate that (1) there is little quantitative contribution of proteins to either the soluble or microsomal fractions from extra-oocytic sources in vivo and (2) the in vitro system itself has little effect on the labelling patterns over the incubation period.

Animals↗
PubMed1976

Analysis of mouse oogenesis in vitro. Oocyte isolation and the utilization of exogenous energy sources by growing oocytes.

A method is described for the dissociation of mouse ovaries and the isolation of oocytes free of somatic cells by agitating pieces of ovary in collagenase and deoxyribonuclease in a calcium and magnesium free salt solution. This method yielded about 50% of the growing oocytes from immature mice. The utilization of exogenously administered 14C-labelled energy sources by oocytes in various growth stages was determined by measurement of evolved 14CO2. Little or no evolution of 14CO2 was detected from oocytes of any size incubated in 14C-glucose, lactate or succinate. The production of 14CO2 from 14C-pyruvate increased logarithmically when plotted against increasing oocyte volume with a plateau occurring after occytes reached a volume of 65,500 mum3 (50 mum diameter). Thus, the pattern of energy metabolism for oocyte maturation and early egg cleavage, wherein glucose and lactate are not utilized as efficiently as pyruvate, has been established by the earliest stages of oocyte growth.

Animals↗
PubMed1976

Comparison of exogenous energy sources for in vitro maintenance of follicle cell-free Xenopus laevis oocytes.

The purpose of these experiments was to determine which exogenous energy sources are suitable for isolated follicle cell-free oocytes from the frog, Xenopus laevis. In order to compare prospective energy sources, follicle cell-free oocytes from 0.4 to 1.3 mm in diameter were incubated in a 1 mM concentration of each of a variety of energy sources and scored daily for the maintenance of morphological characteristics. Vitellogenic oocytes placed in succinate or fumarate deteriorated at the same time as those in saline alone. Oocytes incubated in oxaloacetate (OAA) appeared to remain in the best morphological condition, followed by oocytes maintained in pyruvate or glucose. Fully grown oocytes were tested at various times of incubation for their ability to respond to progesterone by undergoing germinal vesicle breakdown. These experiments showed that oocytes placed in OAA or pyruvate retained the ability to respond to progesterone longer than those in the other energy sources. Increased respiratory rates were stimulated in isolated oocyte mitochondria by succinate as well as pyruvate and OAA. However, oocytes incubated in labelled pyruvate evolved 80 to 140 times as much labelled CO2 as oocytes incubated in labelled glucose or succinate. In addition, it was found that the rate of uptake of pyruvate is 20 to 25 times greater than the rate of uptake of glucose or succinate. It is concluded from these experiments that OAA and pyruvate are the most effective exogenous energy source for the in vitro maintenance of Xenopus oocytes. On possible explanation for the ineffectiveness of glucose or succinate as exogenous energy sources is a restriction in their uptake into the oocytes.

Animals↗
PubMed1976

Defined nutrient medium for the in vitro maintenance of Xenopus laevis oocytes.

A procedure is described for the isolation and culture of large numbers of follicle cell-free Xenopus laevis oocytes in all stages of development. The isolation procedure involves the incubation of pieces of ovary in a calcium-free solution OR2 containing 0.2% collagenase. A defined nutrient medium for the maintenace of the oocytes in vitro is presented. It is shown that this medium, referred to as DNOM, can maintain certain morpological and functional characteristics of oocytes for periods up to 3 weeks.

Animals↗
PubMed1976

Culture of cells in beem capsules: a new technique for electron microscopic study of monolayer cultures.

A method is described for the monolayer cultivation of primary cell suspensions and established cell lines directly in carbon-coated BEEM capsules, BEEM capsules are routinely employed by electron microscopists in tissue embedding procedures; growing monolayer cultures directly on the lids of inverted BEEM capsules presents the obvious advantage of maintaining cell to cell and cell to substratum conthaets with a minimum of stress and damage in the preparative steps for electron microscopy.

Cell Division↗