摘要:

AbstractIn the chrysomonadHymenomonas, a lamellar organelle of undefined function described previously in electron micrographs, is shown to be highly pigmented by absorption and fluorescence light microscopy. Absorption spectra of the lamellar organelle and the chloroplasts ofHymenomonasare presented. In comparison with the chloroplast the lamellar body appears to have an equal concentration of chlorophyll α and nearly three times the concentration of the 490 nm absorbing carotenoid. Fluorescence in the organelle is initially red as in the chloroplast; this is quickly replaced by an intense yellow emission. The rate at which the red fluorescence is replaced by the yellow is oxidation dependent and is quite rapid in the high intensity of the exciting light required for fluorescence micrographs. Possible roles of the organelle in cell metabolism or photochemistry which are considered and evaluated include: photosynthetic organelle, coccolithogenic organelle, symbiont and lysosome

ISSN:0021-9541    

DOI:10.1002/jcp.1040700202

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

年代:1967

数据来源: WILEY

摘要:

AbstractExponentially growingL‐cells were synchronized by the double thymidine‐block method and exposed to high specific activities of tritiated thymidine. DNA, RNA, and protein synthetic rates were measured through one cell cycle with 1‐hour pulses of the appropriate C14‐labelled precursors. Equivalent doses of tritiated water were substituted for tritiated thymidine in some experiments. Total amounts of DNA and histones per nucleus were determined photometrically in Feulgen and fast‐green stained cells.It was observed that incorporated tritiated thymidine has an effect distinct from that of tritiated water and that it enhances the incorporation of the precursors at specific stages of the cell cycle, to a degree roughly proportional to the dose. Photometric data indicated an increase in DNA net synthesis and a metabolic instability of histones in the H3‐thymidine‐treated cells, resulting in higher DNA:h

ISSN:0021-9541    

DOI:10.1002/jcp.1040700203

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

年代:1967

数据来源: WILEY

摘要:

AbstractTen amino acids, namely, arginine, histidine, lysine, tryptophane, methionine, phenylalanine, leucine, valine, threonine and serine were indispensable for growth of rabbit blastocystsin vitro; others were nonessential. Of all the essential amino acids, arginine and lysine were required in relatively high concentrations, 10−2M and 10−3M, respectively, for optimum growth. Complete omission of the non‐essential amino acids from the medium markedly reduced blastocyst growth. Interaction between serine and glycine demonstrated a partial sparing action on serine by glycine, similar to that observed between methionine and cysteine. The amino acid composition of a culture medium capable of providing continuous and consistent growth of rabbit blastocystsin vitrois desc

ISSN:0021-9541    

DOI:10.1002/jcp.1040700204

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

年代:1967

数据来源: WILEY

摘要:

AbstractData obtained from acid hydrolysis and extraction of yeast have demonstrated that routine saponification does not recover total sterol from the cells. This suggests the existence of a form of ergosterol resistant to saponification. Time course analyses of sterol synthesis by resting cell suspensions reveal an inverse relationship between the amounts of base labile and acid labile forms of sterol. These data give strong presumptive evidence for dual forms of ergosterol which are interconvertible according to the respiratory state of the cell.

ISSN:0021-9541    

DOI:10.1002/jcp.1040700205

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

年代:1967

数据来源: WILEY

摘要:

AbstractFifteen alcohol‐soluble carbohydrates have been isolated from logphase cultures ofTetrahymena. Preliminary results obtained by parallel chromatography of impure extracts indicate that some of the soluble components were 2‐D‐deoxyribose, ribose, mannose, fructose, arabinose, xylose, and glucose. Another elution gradient with extracts from cells washed several times, indicates that maltose and glucose were the only identifiable components as compared with 18 known standards. Differences were observed in the alcohol‐soluble carbohydrate content in log‐phase versus stationary‐phase cells. For example, it is clearly indicated that component 13 is missing in stationary‐phase cells while component 15 is missing in log‐phase cells. Fifteen alcohol‐soluble carbohydrates have been chromatographed from synchronized cells. All of these compounds show cyclic variation in relation to cell division. Component 13 accumulates in cells blocked in morphogenesis and decreases as oral development proceeds in s

ISSN:0021-9541    

DOI:10.1002/jcp.1040700206

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

年代:1967

数据来源: WILEY

摘要:

AbstractPrevious studies have demonstrated that a consistent maximum number of polytenic replication cycles occurs in the salivary gland nuclei of a wild‐type strain ofD. melanogaster. Since that number is achieved within the larval period, the DNA synthesis of the prepupal period is believed to be that of propagation of the final cycle. Photometric determinations have been made, in this study, of the salivary gland nuclei of larvae and prepupae of thetu‐hstrain in which the larval period has been extended as a consequence of delay or failure of pupation. The DNA values indicate that a higher maximum number of polytenic replications is achieved in such nuclei. It is inferred, thereby, that initiation of polytenic replication is a function of the larval state and, since it is terminated by the intervention of metamorphosis, a hormonal dependence is sugges

ISSN:0021-9541    

DOI:10.1002/jcp.1040700207

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

年代:1967

数据来源: WILEY

摘要:

AbstractA comparison has been made, by Feulgen photometry, of the polytene nuclei of the salivary glands of a wild‐type strain ofDrosophila melanogastergrown at 17°C and 25°C, respectively. Despite the fact that the time period of the larval stage was more than doubled at the lower temperature, the DNA values were the same in magnitude and similar in distribution of replication classes at each of the stages studied. The data have been interpreted as indicating that, so long as the larval state prevails, initiation of polytenic replication occurs upon completion of the previous cy

ISSN:0021-9541    

DOI:10.1002/jcp.1040700208

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

年代:1967

数据来源: WILEY

摘要:

AbstractCa45and Na22radioautographs using freeze‐substitution with 2‐ethoxyethanol have been prepared for hydra. They reveal a heavy accumulation of Ca and Na along the mesoglea. Microelectrode probes indicate that the positive resting potential in the hydra gut may be resolved into a series of three steps. These results in hydra epithelium suggest that hydra concentrate ions across the outer epidermal cell layer in much the same way that Na is transported across frog s

ISSN:0021-9541    

DOI:10.1002/jcp.1040700209

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

年代:1967

数据来源: WILEY

摘要:

AbstractIntracellular microelectrodes were used to measure resting and action potentials of electric eel electroplax cells from which the middle portion of the anterior moiety had been removed. External electrode studies of this preparation have been described by Chagas and Esquibel (C. R. Acad. Sc., Paris, 260: 3172 ('65)). In the present studies it was found that the resting and action potentials were almost as large as normal in the intact portion of the preparation, whereas these potentials were greatly reduced in the areas from which the anterior moiety had been removed. The reduction in amplitude was greater the farther the microelectrode was from the intact portion, indicating the possibility of decremental spread from the intact portions. The action potentials measured with external electrodes appeared to be an average of potentials from the various areas of the preparation. In other experiments the entire anterior moiety of the electroplax was removed, leaving only the innervated plasma membrane plus some adhering cytoplasm and extracellular material. Various high K+solutions were used to bathe the inner surface. No action potentials could be elicited from these preparations, but resting potentials as high as 51 mV were observed using external electrodes. The resting potential could be reduced reversibly by carbamylcholine applied to the outer surface. Carbamylcholine applied to the inner surface had no effect.

ISSN:0021-9541    

DOI:10.1002/jcp.1040700210

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

年代:1967

数据来源: WILEY

摘要:

AbstractThe melanocytes of isolated fish scales (Fundulus heteroclitus) immersed in 0.1 M aqueous KCl solution and in deuterated KCl solutions, in which 50–70% of the H2O was replaced by D7O, were observed at 300× magnification while they were subjected to increasing hydrostatic pressure, raised in increments of 1,000 psi in the range up to 16,000 psi. In one series of experiments the temperature was maintained at 20°C (± 0.2°), whereas in the other it was kept at 25°C (± 0.2).Initially, all the melanocytes in the KCl media displayed a contracted, or punctate, form. With increasing pressures, gradually, expansion, or pigment granule dispersal, occurred but the degree of expansion at a given pressure depended upon the percentage of deuteration and the temperature. At 20°C in aqueous medium, total expansion, in which the pigment extended all the way out into the peripheral tips of melanocyte branches, occurred at 8,000–9,000 psi. At lower pressure, the intermediate values, expressed as a percentage of the total, fell along a smooth, slightly sigmoid curve. In the deuterated media, similar curves were obtained, but the pressure levels required to produce a given degree of expansion were significantly higher. Thus, maximum expansion required the imposition of 14,000 psi in the 50% D2O medium and of 16,000 psi in the 70%. Upon decompression, at the end of each experiment, the melanocytes quickly contracted, reaching a completely punctate form within 3–4 minutes.Similar relationships were found at 25°C, except that all the pressure values were significantly higher than those at 20°C. In fact the values for 25°, with 50% deuteration, were very similar to those for 20°, with 70% D2O.The evidence tends to confirm conclusions, previously submitted, namely, that, as expansion occurs, the cytoplasm of the unicellular pigmentary effectors of the fish undergoes a progressive process of solation and that contraction involves a reestablishment of the original firm gel structure. Thus the well known solational effects of high pressure tend to be counteracted by agencies, such as increasing deuteration and temperature, which are known to foster protoplasmic gel

ISSN:0021-9541    

DOI:10.1002/jcp.1040700211

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

年代:1967

数据来源: WILEY