摘要:

AbstractTheH‐2antigenic properties of lipoprotein fractions from malignant (L‐5178Y leukemia) and normal (spleen, thymus, liver, kidney) mouse tissues have been studied by serological and immunological tests, and the results compared to the previously described activities of these fractions in homograft‐sensitization tests. Although, in general, the relative activities in the different assays parallel each other some notable exceptions were found. The non‐microsomal lipoproteins from leukemic tissue, inactive in homograft‐sensitization tests, did elicitH‐2antibody. Also, the liver microsomal lipoproteins, which are inactive in homograft‐sensitization tests in amounts 400 × the minimal effective doses of spleen preparations, exhibited, inin vitroagglutinin‐inhibition tests, approximately one‐fourth theH‐2activity of the latter. Other findings of note include the high antibody‐eliciting potency of the spleen and leukemia microsomal lipoproteins (15 μg protein was sufficient to initiate primary immunization and 1 μg protein to cause an anamnestic response); and the quantitive identity ofH‐2antigen activity of the microsomal lipoprote

ISSN:0021-9541    

DOI:10.1002/jcp.1040680302

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

年代:1966

数据来源: WILEY

摘要:

AbstractUsing a method of cocultivation of embryonic Chinese hamster cells (CHEF) with Rous sarcoma cells and infection of CHEF by RSV‐SR, it was possible to obtain malignant transformation of hamster cells. The morphologically altered cells became apparent within 15–36 days.In the cells transformed by cocultivation, the genome of RSV was determined by the method of contact of the transformed cell and the chicken cellin vivo; the malignant character of the transformed cells was demonstrated by transfer to a homologous newborn host. Repeated attempts to detect virus production in transformed Chinese hamster cells failed.Prior to malignant transformation and in early transformed cultures the diploid stem‐line was maintained. A slight decrease in the proportion of diploid cells in transformed cultures was revealed in some experiments and is discussed. Prolonged cultivation of these cells, as also of control fibroblasts, shifts the stem‐line to the hyperdiploid or hypotetraploid region.The mechanism of malignant transformation by RSV is discussed with regard to the action of the viral genome and alteration of the genetic make‐up of the cell by

ISSN:0021-9541    

DOI:10.1002/jcp.1040680303

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

年代:1966

数据来源: WILEY

摘要:

AbstractEffects of KCN (10−4M), simultaneous presence of varying concentrations of D‐glucose and L‐sorbose, and temperature on transport of carbohydrate inC. luciliaehave been studied. The rate of carbohydrate entrance is inhibited, in all sugars used, ranging from 19% to 70% inhibition at 0.5 mM external concentrations. However, this inhibitor does not affect transport from external concentrations of the order of 0.02 M. At 20 mM external concentration, the rate of L‐sorbose entrance is greatly inhibited by the simultaneous presence of D‐glucose, and the transport mechanism shows enormously greater affinity for glucose than for other monosaccharides. However, at 0.5 mM external concentration, the rate of sorbose entrance is not inhibited at all by the simultaneous presence of D‐glucose. In the temperature interval 15°–25°C, the Q10for rate of entrance when the external concentration is 0.5 mM is 2.8 times larger than the Q10when the external concentration is 20 mM. These data are interpreted as strongly suggesting two mechanisms for carbohydrate entrance: (a) facilitated diffusion, of importance only at high external concentrations; (b) an active transport mechanism, active at low external concentrations and dependent upon a supply of metabolic energy. These results are compared with those reported in the literature for other

ISSN:0021-9541    

DOI:10.1002/jcp.1040680304

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

年代:1966

数据来源: WILEY

摘要:

AbstractThese experiments showed that an isolated muscle bundle could be used to study, simultaneously, ion transport and the activity of surface enzymes. Frog muscles were carefully dissected and incubated for four hours in Ringer's solution containing a tris buffer and 3 mM ATP; at various times samples of the medium were chromatographed and analysed spectrophotometrically for nucleotide content. Samples of the final medium were analysed for inorganic phoshpate and for ammonia. The results demonstrated the conversion of adenosine triphosphate to inosine monophosphate, via adenosine diphosphate and adenosine monophosphate. Under the conditions of the experiment IMP was detected on chromatograms within 20 minutes of incubation; at the end of four hours the media had concentrations of 2.3 mM IMP, 4.4 mM inorganic phosphate and 2.6 mM ammonia, showing a stoichiometric relation among the products formed. There was convincing evidence that the enzymes involved (ATPase, adenylate kinase and AMP deaminase) must be situated close to or on the muscle surface. No effect of ouabain (1 μM) on the activity of the ATPase, adenylate kinase or deaminase could be found in these experiments, but the drug inhibited Na and K recovery from a Na‐loaded, K‐depleted s

ISSN:0021-9541    

DOI:10.1002/jcp.1040680305

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

年代:1966

数据来源: WILEY

摘要:

AbstractThe progressive growth and development of spleen colonies was studied in heavily irradiated host mice in which erythropoiesis was modified by various procedures. Erythropoietic activity in non‐polycythemic hosts bearing spleen colonies was not increased by injections of exogenous erythropoietin. Detectable levels of erythropoietin were found in the heavily irradiated host mice suggesting that the failure of exogenous erythropoietin to modify erythropoiesis was because the host mice were already maximally stimulated by the high endogenous erythropoietin levels.Spleen colonies do not become erythroid in polycythemic mice. The injection of exogenous erythropoietin into heavily irradiated polycythemic hosts did not decrease the total number of spleen colonies produced by a given bone marrow transplant, as would be expected if erythropoietin acted directly on the colony‐forming cells. Comparison of growth curves for colony‐forming cells in the spleens of polycythemic hosts either receiving or not receiving erythropoietin indicated that the overall doubling time of colony‐forming cells during the first ten days after transplantation was not changed by the daily injection of erythropoietin.These experiments are consistent with the concept that erythropoietin is necessary for the development of erythroid colonies. Erythropoietin acts upon some progeny of the colony‐forming cell rather than the colony‐forming

ISSN:0021-9541    

DOI:10.1002/jcp.1040680306

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

年代:1966

数据来源: WILEY

摘要:

AbstractIsolated 3‐ and 5‐day chick embryo hearts contain sufficient endogenous substrates to maintain their pulsatile activity for several hours under aerobic conditions, and even after five hours in substrate‐free medium the rates are 40 to 50% of the original rates. Carbohydrate appears to be an important component of the endogenous substrates since 1 mM 2‐deoxyglucose causes rapid failure of rate, and glycolysis appears to be a major energy pathway since the rate is depressed only about 50% by 2‐hour's exposure to 10 mM fluoroacetate. In nitrogen the hearts rapidly become asystolic in the absence of added substrate. Recovery of the rate occurs if oxygen is reintroduced within one hour, but longer periods of anoxia result in progressively less recovery, especially with the 3‐day hearts which appear to be particularly susceptible to irreversible damage. With 5.55 mM glucose as substrate there is little decrease in the original aerobic heart rate during five hours, and the hearts can tolerate total anoxia for five hours with rates only slightly less than the aerobic rates. The hypothesis of a preferential pentose phosphate pathway of glucose catabolism in the very young chick embryo heart is discussed, but no direct evidence in support of its existence is revealed in

ISSN:0021-9541    

DOI:10.1002/jcp.1040680307

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

年代:1966

数据来源: WILEY

摘要:

AbstractProcedures have been devised for the isolation of the surface membranes of mouse fibroblasts (L cell) and a variety of other cells. The surface membranes are stabilized by various reagents in a hypotonic solution and are then removed intact or as large fragments with a Dounce homogenizer. The membranes are purified by differential centrifugation on solutions of sucrose or glycerol or on a column of fine glass beads. A trilaminar pattern can be seen in thin sections of the membrane in the electron microscope. Sufficient material can be conveniently obtained for chemical analyses.

ISSN:0021-9541    

DOI:10.1002/jcp.1040680308

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

年代:1966

数据来源: WILEY

摘要:

AbstractProperties of the fully developed phosphate transport system in the fertilized egg of the sea urchin,Strongylocentrotus purpuratus, were investigated. The rates of phosphate transport at concentrations of external phosphate of 1 to 44 μM, both in the absence and in the presence of 100 μM arsenate, exhibit typical saturation kinetics. At sea water concentrations of 2 μM phosphate, the rate of uptake is about 2 × 10−9μm/egg/minute at 15°C. Arsenate is a competitive inhibitor of phosphate transport, fully and immediately reversible in its effects, yielding Kivalues ranging from 10.5 to 14.1 × 10−6M in comparison to the corresponding apparent KM(Michaelis‐Menten) constants for phosphate of 5.6 to 7.5 × 10−6M (pH 8.0, 15°C).The rate of arsenate uptake in a phosphate deficient medium amounts to 2.8 to 2.9 × 10−10μm arsenate/egg/minute at an arsenate concentration of 2.9 to 10.2 μM arsenate (HAsO4−−), which is 9.5 and 5.6% of the rate of phosphate uptake at corresponding phosphate concentrations.Arsenate has essentially the same developmental effects at initial concentrations of 5–10 μM and 100 μM arsenate, namely no observable effects for exposure periods of 7.5 hours, although longer periods result in blockage of development at the early blastula stage.Outward flux of phosphate ions cannot be demonstrated by washing prelabelled eggs with sea water containing low or high concentrations of phosphate, even when phosphorylation has been blocked by exposing the eggs to a metabolic inhibitor.Phosphate uptake rates measured in the pH range from 5.0 to 10.0 reveal a sharp optimum at pH 8.8–8.9. Reference to the apparent pK' values of the phosphoric acid system indicate that the entering species is the HPO4−−ion. The effects on rates of phosphate uptake of exposure to sea water at pH values between 7 and 10 for 30 minute periods are fully reversible, but at lower pH values, reversal is delayed, and is only partial.Sodium molybdate (0.01 M), sodium pyrophosphate (1.5 × 10−4M), and adenosine triphosphate (1–5 × 10−4M) for exposure periods ranging from 40 to 180 minutes did not significantly affect phosphate uptake. Omission of Ca++ion from artificial sea water is without effect on phosphate uptake but the absence of both Ca++and Mg++results in profound and irreversible depression of both phosphate uptake and development.The data of this and the following paper are consistent with the conclusion that the transport of phosphate involves a surface located carrier.The apparent secondary and tertiary ionization constants of phosphoric acid in sea water (ionic strength = 0.6885) were measured, resulting in a value for pK′2= 6.14 and for pK′3= 10

ISSN:0021-9541    

DOI:10.1002/jcp.1040680309

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

年代:1966

数据来源: WILEY

ISSN:0021-9541    

DOI:10.1002/jcp.1040680310

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

年代:1966

数据来源: WILEY

摘要:

AbstractMetabolic inhibitors were applied after the transport system was fully developed in concentrations sufficient to block cleavage. 0.5–1.0 × 10−4M cyanide and anaerobiosis caused from negligible to moderate (40%) inhibition of phosphate uptake. The inhibition occurred late in the breeding season, and the inhibitory action of cyanide on uptake was associated with irreversible developmental effects. Azide (3 × 10−3M) did not inhibit uptake when the chamber method was used, but the aliquot and Hopkins' tube methods gave considerable inhibition. Purified preparations of 2,4‐dinitrophenol (1 × 10−4M) did not inhibit uptake. Sodium iodoacetate (up to 0.05 M) and phlorizin (0.005 M) exerted no effect.Calculations of the minimal work requirement for the transport process reveal that this amounts to only a small fraction (0.24% at an external phosphate concentration of 2 μM) of the total available metabolic energy.Exposure of eggs at five minutes after insemination (lag phase) to cyanide (5 × 10−5M), anaerobic conditions, or azide (3 × 10−3M) blocked the expected increase of phosphate uptake. Removal of the inhibitors led to resumption of development and the appearance of the phosphate transport system in an essentially normal pattern.Exposure of eggs to 1.4–2.0 × 10−4M p‐chloromercuribenzoate (p‐CMB) during the accumulation phase severely depressed phosphate uptake, but cleavage was not inhibited nor delayed; recovery from the inhibition was accelerated by 1 × 10−3M cysteine. Exposure to p‐CMB during the lag phase blocked the appearance of the transport system; cleavage proceeded normally. After the removal of p‐CMB little reversal occurred until the addtion of 1 × 10−3M cysteine, when the phosphate transport system developed in an essentially normal manner.Trypsin (0.001–0.01%) neither activates the transport system in unfertilized eggs, nor inactivates it in denuded fertilized eggs by removal of surface proteins.The data are consistent with the conclusion that (1) the phosphate transport system is newly synthesized at fertilization in energy dependent reactions, and (2) phosphate transport is a carrier mediated process no

ISSN:0021-9541    

DOI:10.1002/jcp.1040680311

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

年代:1966

数据来源: WILEY