ISSN:0095-9898    

DOI:10.1002/jcp.1030660302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1965

数据来源: WILEY

摘要:

AbstractA study has been made of the effect of acetylcholine upon the heart rate of the early chick embryo, and it has been noted that under certain experimental conditions acetylcholine stimulates the heart rate during the period of vagal innervation, while depressing the heart rate after the nerve supply is established. Isolated chick embryo hearts freely suspended in a phosphate‐buffered (bicarbonate‐free) medium beat at only about one‐third theirin ovorates, and acetylcholine produces biphasic effects of stimulation and inhibition of the heart rate depending upon the concentration of the drug and the age of the hearts, the maximal stimulation occurring at five days. When suspended in Krebs bicarbonate medium the hearts beat at rates of about 72 to 74% theirin ovorates, and acetylcholine produces only slowing of the heart rate. This effect of acetylcholine can be diminished or reversed when an inhibitor of endogenous acetylcholine, hemicholinium‐3 is added. We have postulated that both inhibitory and stimulatory receptors for acetylcholine exist in the early chick embryo heart and that the response to added acetylcholine depends in part on levels of endogenous acetylcholine already present in the heart. The role of endogenous acetylcholine in regulating heart rate is di

ISSN:0095-9898    

DOI:10.1002/jcp.1030660303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1965

数据来源: WILEY

摘要:

AbstractWhole chick embryo blastoderms at zero‐ to 7‐somites have been explanted onto a nutrient medium and incubated at 37°C for 20 hours, in order to develop to 18‐ to 19‐somites, when the heart rate is depressed by acetylcholine and even more strongly by a number of parasympathomimetic drugs and cholinesterase inhibitors. Hence we have concluded that receptors for acetylcholine are present in the early chick embryo heart before innervation by the vagus nerve is initiated, but that the receptors do not possess the specificity of adult acetylcholine cardiac receptors. Incubation of the zero‐ to 7‐somite blastoderms on media containing certain of the parasympathomimetic drugs and cholinesterase inhibitors greatly increased the sensitivity of the hearts to depression of rate by acetylcholine at 18‐ to 19‐somites, and we have concluded that development of acetylcholine receptors has been stimulated by the drugs. A possible stereochemical relationship between acetylcholine receptors and drugs that are able to stimulate the development of the recepto

ISSN:0095-9898    

DOI:10.1002/jcp.1030660304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1965

数据来源: WILEY

摘要:

AbstractThis study has attempted an evaluation of thein vitrometabolic characteristics of the epididymis of the mouse and a definition of areas for further research pursuant to the elucidation of the role of this organ in the process of sperm maturation and storage.Optimal conditions were ascertained for the manometric measurement of total respiration and for the estimation of glycolytic activity by assay of lactate accumulation and phosphate esterification in fluoride poisoned homogenates. Homogenates of mouse kidney were utilized in all experiments for comparative purposes.Thein vitrodata presented indicate the epididymis to be predominantly oriented to a glycolytic metabolism. It is suggested that this metabolic orientation when considered with the results of other investigators is compatible with a hypothesis for the secretion of lactic acid by the epididymal epithelium into the lumen of the epididymal canal for spermatozoan utilization.

ISSN:0095-9898    

DOI:10.1002/jcp.1030660305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1965

数据来源: WILEY

摘要:

AbstractThe purpose of the study is a comparison of respiratory metabolic rates and anaerobic glycolytic activity (lactate accumulation) in homogenates of epididymides from normal, orchidectomized and testosterone replaced‐orchidectomized mice. Animals subjected to vasa efferentiectomy were used to furnish sperm free homogenates as controls for the homogenates from orchidectomized animals, and to furnish estimates of the contribution of the spermatozoa to these metabolic parameters in homogenates of normal epididymides.Efferentiectomized mice yield homogenates with a significantly lowered rate of respiratory activity (30%). Experiments with fractions of these homogenates showed this reduction in activity to be equivalent to the contribution of the spermatozoa in homogenates from normal mice. No significant difference in the rate of respiratory metabolism was observed among homogenates obtained from efferentiectomized, orchidectomized, testosterone replaced‐orchidectomized, or testosterone injected‐efferentiectomized mice.Efferentiectomy also resulted in a lowered rate of anaerobic glycolytic activityin vitro. No further reduction or elevation of this activity was observed in homogenates from orchidectomized or testosterone injected animals. Further study indicated this loss following efferentiectomy to be due to a reduced glycolytic activity in the epididymal epithelium rather than to the absence of spermatozoan contribution to the metabolism.The evidence presented supports the hypothesis that the presence of some component of the spermatozoa or the fluids in which they reside controls the activation or inhibition of a segment of the lactic dehydrogenase activity which is responsible for the secretion of lactic acid into the epididymal canal for spermatozoan utiliz

ISSN:0095-9898    

DOI:10.1002/jcp.1030660306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1965

数据来源: WILEY

摘要:

AbstractIn freshwater the caiman gains water at the rate of 3.5 ml/kg hr or 1.1 μl/cm2hr. Of this 70% is the result of uptake through the skin, the rest being due to drinking. This gain in water is excreted by the kidneys as a hypotonic urine. Urine sodium losses are reduced by active sodium uptake from the urine during storage for 3 to 4 hours in the cloaca.In vitroandin vivoexperiments indicate that the skin is somewhat permeable to sodium, which moves along concentration gradients.In air the caiman loses water by evaporation (1.2 μl/cm2hr). About 75% of this takes place from the skin.In 3.3% NaCl solution caimans show elevated serum sodium concentrations and 20% of them die within 24 hours. The sodium accumulation is mostly due to drinking (4.4% of the body weight/day), and only to a minor extent to osmotic water loss through the skin (2.5% of the body weight/day or 0.6 μl/cm2hr). The permeability of the caiman is compared to that of fishes, Amphibia and other reptil

ISSN:0095-9898    

DOI:10.1002/jcp.1030660307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1965

数据来源: WILEY

摘要:

AbstractResults obtained from analysis of the early development of embryonic cells under tissue culture conditions apparently reflect both true developmental events and artificial changes consequent upon the isolation and transplantation of the tissues. The magnitude and mechanisms of such changes were examined in a model system, the differentiating metanephrogenic mesenchyme of mouse embryos, which we have used for several analytical studies in developmental biology. The results indicate that isolating and transplanting this tissue to organ culture conditions causes a marked decrease in nucleic acid metabolism, as measured in incorporation experiments. This lag period extends through the first 20 to 30 hours ofin vitrocultivation, after which normal metabolism is restored. The change does not seem to be related to cell loss, since viability counts reveal only a small percentage of cells to be dying during this period. Adding Zn++ions to the culture medium had a favorable effect on the incorporation of nucleic acid precursors during the lag period, suggesting that the enzyme treatment employed during isolation might have removed bivalent cations from this tissue.

ISSN:0095-9898    

DOI:10.1002/jcp.1030660308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1965

数据来源: WILEY

摘要:

AbstractA method is described for the cloning of normal mouse “mast” cells in tissue culture in a soft agar medium. The colonies contain cells in different stages of differentiation. It was shown that a colony can be initiated by a single colony forming unit, and that colonies are formed as a result of cell multiplication.Cell suspensions from adult spleen gave about 3 colonies per 105cells seeded. A re‐cloning of these colonies gave about 3 colonies per 103cells seeded.The frequency of colonies from SWR mice was higher with adult spleen than with adult thymus. No such colonies were obtained with adult lymph node cells.The formation of colonies was shown to require the presence of an embryo cell feeder layer. Since the feeder layers were seeded underneath the agar, the results indicate that the substance(s) required for the growth and differentiation of “mast” cells can pass thr

ISSN:0095-9898    

DOI:10.1002/jcp.1030660309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1965

数据来源: WILEY

摘要:

AbstractThe cells of an established mouse fibroblast line, 3T3, have a high plating efficiency and grow rapidly in sparse culture, but stop growing at a very low saturation density in comparison with other lines, because 3T3 is extremely sensitive to contact inhibition of cell division. After each medium change, however, there occurs in a small fraction of the cells in a saturation density culture a series of changes that results in a single rather synchronized division 30 hours later. This is due to a macromolecular substance in the serum which appears to act by reducing the sensitivity of the cells to contact inhibition. The first recognizable event following the addition of serum to a stationary phase culture is a ten fold increase in the rate of RNA synthesis, occurring within 30 minutes. An increase in the rate of protein synthesis follows several hours later. DNA synthesis does not begin before 12 hours, but by two hours after medium change an appreciable fraction of the cells become committed to eventual DNA synthesis and cell division. The sequence of event suggests that regulation of RNA synthesis is the means by which contact inhibition controls cell division.

ISSN:0095-9898    

DOI:10.1002/jcp.1030660310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1965

数据来源: WILEY

摘要:

AbstractThe rate of C14O2evolution from uniformly labeled glucose by washed white cells from peritoneal exudates increased several times after prolonged soaking of the cells in protein‐free medium and was repressed again upon incubation of the cells in peritoneal fluid of higher concentrations, whereas incubation in lower concentrations had a stimulatory effect, as compared to this rate by the cells incubated in protein‐free medium alone. Similarity of this effect of peritoneal fluid to the protective action of blood serum on the cells in tissue culture and the possible mechanism of action of both were discussed.It is suggested that the metabolism of the cells in multicellular organism is repressed by humoral macromolecular substances, and that the increase of glucose‐U‐C14oxidation by the cells after prolonged soaking in protein‐free medium is related to the first step in the processes by which the cells move from a dormant statein vivointo that of active growth and cell division

ISSN:0095-9898    

DOI:10.1002/jcp.1030660311

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1965

数据来源: WILEY