ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1981.tb02819.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1981.tb02820.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTStudy of microorganism growth kinetics requires measurement of maximal specific growth rate. Standard methods of measurement‐batch, semicontinuous and continuous steady state‐have sources of imprecision that can be substantially reduced by a modification of the continuous steady‐state method. Data are presented, using the ciliateTetrahymena pyriformis, that indicate that the theoretical foundation of the new method is firm and that precision can be incr

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1981.tb02821.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTVariations in DNA levels for log‐phaseEuglenahave been shown to be directly related to the pH of the culture medium. Data are presented here for cultures grown in Cramer and Myer's medium at pH 3.0 and 6.8. DNA levels are ∼50% greater forEuglenaat the higher pH value, confirming earlier repo

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1981.tb02822.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTDiscophrya colliniis a free‐living suctorian with retractile tentacles covered by a thick fibrous cortex. The tentacles contain a microtubular central canal surrounded at the base by a fibrous collar. Electrical stimulation induces a reproducible tentacle retraction. With extracellular electrodes, the tentacles nearest the anode respond initially, contracting by up to 75% of their original length. There is an inverse relationship between voltage level and duration of stimulus in producing a threshold response, and at a set voltage, between duration and degree of retraction. With intracellular electrodes, the membrane potential has been measured as ‐30 mV, and tentacle retraction occurs in response to as little as 1.25 nA when the intracellular electrode is made the cathode of the circuit. SEM studies show that retracted tentacles have a wrinkled cortex, while TEM shows that the microtubular canal bends as it enters the cytoplasm. No consistent changes occur in the microtubule configuration of the canal on retraction, suggesting that the microtubules are not directly involved in the contractile mechan

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1981.tb02823.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTInhibition of cell division inEuglena gracilisby visible light is pH‐dependent, being most severe in the pH range 3.5–5.0. Transfer of phototrophic cells from pH 6.8 to pH 4.2 can lead to cell death at modest light intensities (500 ft‐cd) and inhibition of division at lower intensities (300 ft‐cd). Inhibition is preceded by a large influx of phosphate, most of which remains in the cold PCA pool. It is suggested that light may act to reduce control over phosphate entry at these intermediate pH levels, and excess phosphate leads to inhibition of cell division o

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1981.tb02824.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTViable merozoites ofPlasmodium knowlesiwere isolated and the proteins that were labeled on intact merozoites by lactoperoxidase‐catalyzed radioiodination were identified. Sodium dodecyl sulfate polyacrylamide gel electrophoresis and autoradiography of Triton soluble extracts of labeled merozoites demonstrated eight major bands ranging in apparent molecular weight from 150,000 D to 22,000 D. Exposure of intact merozoites to trypsin (10 μg/ml) for 10 min resulted in the loss of the two highest molecular weight proteins (150,000 D and 105,000 D) and the appearance of two new bands at 70,000 D and 62,000 D. Trypsin treatment under these conditions also removed the receptor(s) for merozoite attachment to erythrocytes. Therefore, these high molecular weight proteins are candidates for the merozoite component that attaches to erythrocytes. There was no evidence that the labeled membrane components were serum or erythrocyte membrane components, two potential contaminants in the preparation. Anti‐rhesus erythrocyte antibody did not precipitate labeled merozoite proteins. Furthermore, the immunoprecipitation of labeled merozoite proteins by rhesus anti‐merozoite serum was not inhibited by erythrocyte

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1981.tb02825.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTGuanylate cyclase activity decreased during the division phase of heat‐shock synchronizedTetrahymena pyriformis, strain GL. However, when Ca2+was removed by EGTA to negate the effects of the Ca2+‐binding protein (calmodulin), which is required for the full activity of guanylate cyclase in this organism, no significant change in the enzymatic activity was observed throughout the cell cycle. On the other hand, the reduced guanylate cyclase activity at division phase was associated with a decreased level of calmodulin content. These results suggest that fluctuations in guanylate cyclase activity during the cell cycle would be dependent on the concentration of calmodu

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1981.tb02826.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTThe effect of holothurin (a marine biotoxin) on the resistance of mice toTrypanosoma musculiwas measured by studying changes in the parasite population in vivo. Swiss Webster (SW), Beige (BG), and Black (BL) mice treated with holothurin prior to and simultaneously with infection of trypanosomes had lower parasitemias than controls. Higher levels of parasitemia were observed in mice treated after infection with trypanosomes. The timing of administration of holothurin appeared to be an important factor in the observed effect. The minor variations in the parasitemia seemed to be related to the mouse strain.

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1981.tb02827.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTBy using fluorescent isothiocyanate‐conjugated concanavalin A (FITC‐Con A), cell surface events were examined under a light microscope during the early period of the conjugation process inTetrahymena thermophila. Until the two complementary mating types (D‐III and IV) were mixed, Con A‐binding activities were hardly detected on the cell surface of ciliates. After mixing, however, the FITC‐Con A (25 μg/ml) bound especially to the anterior cell surface at the early stage of conjugation, followed by characteristic changes of the Con A‐binding pattern and, subsequently, by formation of a bright fluorescent ring around the area of contact between conjugants. Such alterations of FITC‐Con A‐binding pattern were found to be interrupted or eliminated by cycloheximide (2 μg/ml). These findings are related to the onset and subsequent conjugation

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1981.tb02828.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY