bluuebunny/crossref_metadata_2025_split huggingface dataset:
A study of the crustacean axon repetitive response. III. A comparison of the effect of veratrine sulfate solution and potassium‐rich solutions
Authors: Wright Ernest B. , Tomita Tadao 
Published: February 2005

AbstractThe crustacean single nerve fiber gives rise to trains of impulses during a prolonged depolarizing stimulus. It is well known that the alkaloid veratrine itself causes a prolonged depolarization; and consequently it was of interest to investigate the effect of this chemically produced depolarization on repetitive firing in the single axon and compare it with the effect of depolarization by an applied stimulating current or by a potassium‐rich solution. It was found that veratrine depolarization, though similar in some respects to a potassium‐rich depolarization of depolarizing current effect, was in many respects quite different.(1) At low veratrine concentration, less than 1 Mg%, the negative after potential following a spike action potential was prolonged and augmented. At higher concentrations or after a long period of time, veratrine caused a prolonged steady state depolarization of the membrane, the “veratrine response”. The prolonged plateau depolarization response could be elicited with or without an action potential spike by a short or long duration stimulating pulse, but only if the veratrine depolarization was prevented or offset by an applied conditioning hyperpolarizing inward current.(2) The “veratrine response” resembled the potassium‐rich solution response in the plateau‐like contour of the depolarization and the very low membrane resistance during this plateau phase. Like the potassium response, it was possible to obtain a typical hyperpolarizing response with an inwardly directed current pulse if applied during the plateau phase. During the negative after potential augmented with veratrine, however, this hyperpolarizing response was not observed.(3) In contrast to the potassium response, however, the “veratrine response” is intimately associated with the sodium concentration in the external medium. The depolarization in millivolts is linearly related to the log of the concentration of external sodium. Moreover, during veratrine action there is a continuous and progressive inactivation of the sodium mechanism which ultimately terminates repetitive firing and abolishes the spike action potential. Then even with conditioning hyperpolarization only the slow response may be elicited in veratrine, occasionally with a spike superimposed if sodium is present, but without repetitive firing.(4) It is concluded that veratrine action is the result of a chemical or metabolic reaction by the alkaloid in the membrane. It is suggested that veratrine may inhibit the sodium extrusion mechanism, or may itself compete for sites in the membrane with calcium and/or sodium. This explains the inhibiting effect of high calcium, the abolition of the “veratrine response” with low temperature and high calcium combined and the progressive inactivation of the sodium system.
Metabolic control reactions of the intact urinary bladder of the toad
Authors: Canessa‐Fischer Mitzy , Davis Robert P. 
Published: February 2005

AbstractMetabolic control reactions have been studied in the intact toad bladder by means of fluorescence spectrophotometric measurement of reduced pyridine nucleotide and by measurement of respiration with the platinum electrode. substrates such as pyruvate and succinate lead to prompt increases in reduction level of pyridine nucleotide with only slight acceleration of respiration. major metabolic control is exerted by adp, which depletes the intact bladder of reduced pyridine nucleotide and accelerates respiration. respiratory control ratios, as for isolated mitochondria, depend upon the substrate being metabolized. a significant fraction of added adp appears to gain entry into the intact toad bladder and is converted to atp, anaerobiosis and amobarbital lead to increased levels of reduction of pyridine nucleotide. the spectroscopic and metabolic properties of the reduced pyridine nucleotide being studied identify it with that fraction of dpnh which is bound at one of the energy conservation sites linking phosphorylation reactions with electron transfer.
Membrane permeability changes in amphibian eggs at ovulation
Authors: Morrill Gene A. , Rosenthal Jean , Watson Donald E. 
Published: February 2005

AbstractElectropotential differences between the cytoplasm and external medium have been compared in the mature R. pipiens occyte and the ovulated unfertilized egg as a function of [Na]o, [K]o, [Ca]o and [Cl]o. In solutions containing 1.0 mM Ca++ the oocyte behaved as though it were predominantly permeable to K+ and Cl−, i.e., like a KCl electrode. However, the steady potential decreased with decreasing [Ca]o and in 5 × 10−4 mM [Ca]o the oocyte membrane behaved like a NaCl electrode. Studies on the steady potential as a function of [Na]o, [K]o and [Cl]o in 1.0 mM Ca++ or Ca‐free solutions suggest that Ca++ controls the passive permeability of the oocyte membrane to Na+ and Cl−. In the ovulated unfertilized egg the K+ selectivity of the cell membrane disappeared and the system behaved like a NaCl electrode. No effect of external Ca++ or K+ concentration changes on the steady potential was observed. These results indicate that the ion permeability properties of the ovulated egg are similar to that of the ovarian oocyte in Ca‐deficient medium, and suggests that the mechanism of ovulation may involve the removal of Ca++ regulation of ion permeability of the egg cell membrane.
The sodium and potassium activated atpase. II. Comparative study of intestinal epithelium and red cells
Authors: Berg G. G. , Szekerczes J. 
Published: February 2005

AbstractThe Na‐K ATPase found in sedimentable fractions of intestinal epithelium of rats hydrolyzed cytidine triphosphate nearly as well as ATP (25% to 50%); was active only in presence of divalent cations, with specificity for Mg (100%), Mn (50%) and Ca (10%); showed a plateau of activation when Mg concentrations were in excess of substrate; and was inhibited by a second divalent cation (Zn > Mn > Ca), and by 3 × 10−4 M ouabain (50%). Parallel assays of rat red cell ghosts showed differences in substrate specificity (CTP was not utilized), in activation kinetics (activation peak with Mg) and in greater specificity to Mg (Mn was a weaker activator and Zn was a weaker inhibitor). Stabilities also differed in the two preparations: NaK ATPase of intestinal epithelium was activated by sucrose extraction and denatured during cytolysis at room temperature, while that of red cell fragments was denatured during sucrose extraction and preserved by hemolysis at room temperature. Other properties of NaK ATPase studied in the two tissues included activation by monovalent cations (optimum at 160 mM Na, 15 mM K), specificity to monovalent cations, and sensitivity to lipid solvents and to some drugs. The data were discussed in terms of comparative properties of NaK ATPases of various cells.Residual ATPase activities of intestinal epithelium and red cell ghosts were shown to differ in substrate specificity, inhibition and activation. “Residual ATPase” from intestinal epithelium was a zinc‐activated nucleoside polyphosphate phosphohydrolase, while ghosts contained MgATPase. Only the latter enzyme was specific to ATP and Mg, activated by Ca in presence of Mg, and sensitive to inhibition by PCMB and Zn.
Potentiation of the colchicine effect on frog melanocytes by high hydrostatic pressure
Authors: Malawista Stephen E. , Asterita Harvey , Marsland Douglas 
Published: February 2005

AbstractIn dermal melanocytes of Rana pipiens, colchicine is known to produce a gradual, dosage‐dependent dispersion of melanin granules, irreversible over several hours. This effect is potentiated by a number of chemical agents that normally produce a reversible dispersion of granules. In the present study we examined the effect of high hydrostatic pressure on changes induced in melanocytes by colchicine.In Ringer's solution, samples of skin from a single frog were incubated for 30 minutes at room temperature with or without colchicine, 9 × 10−5 M. Then two samples, one of which had been pretreated with colchicine, were successively subjected to 12,000 psi for one hour at 25 to 26°C. The degree of dispersion of melanin granules in melanocytes was observed before, during and after the period of pressure.In frog skin pretreated with colchicine, the usually gradual, irreversible dispersion of melanin granules in melanocytes was potentiated.Since high pressure is known to produce solational changes in protoplasm, such changes may accompany dispersion of melanin granules in melanocytes. If this be so, then sol‐gel equilibria may be important in the action of dispersing and aggregating agents, many of which are hormones and other physiologically active agents. Finally, the present study supports the hypothesis that colchicine shifts protoplasmic sol‐gel equilibria toward a less gelated condition.
Effect of halothane anesthesia on extravascular mobilization of neutrophils
Authors: Bruce David L. 
Published: February 2005

AbstractThe ability of neutrophil leukocytes to extravasate into the peritoneal cavity in response to an intraperitoneal injection of bacterial endotoxin was studied in mice. The normal response of a marked accumulation of intraperitoneal neutrophils was completely abolished by halothane anesthesia. It was further shown that such abolition depended upon the presence of halothane duringthe time the extravasation would normally be occurring. The evidence points toward an effect on either the leukocyte or the vessel rather than a non‐specific “stress” effect. It is suggested that the effect is on the neutrophil, rendering it less deformable and, hence, less able to undergo trans‐vascular diapedesis.
The effect of erythropoietin on the growth and development of spleen colony‐forming cells
Authors: Schooley John C. 
Published: February 2005

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 cell itself.
The cellular composition of hemopoietic spleen colonies
Authors: Fowler J. H. , Wu A. M. , Till J. E. , McCulloch E. A. , Siminovitch L. 
Published: February 2005

AbstractThe cellular composition of individual hemopoietic spleen colonies has been studied using techniques which tested primarily for cell function rather than cell morphology. Erythroblastic cells were recognized by their capacity to incorporate radioiron, granulocytic cells by their content of peroxidase‐positive material, and hemopoietic stem cells by their ability to form spleen colonies in irradiated hosts. It was found that, 14 days after the initiation of spleen colonies, the distribution of these cell types among individual colonies was very heterogeneous, but that most colonies contained detectable numbers of erythroblasts, granulocytes and colony‐forming cells. An appreciable proportion of the cells in the colonies could not be identified as any of these three cell types. No strong correlations between numbers of erythroblasts, granulocytes and colony‐forming cells in individual colonies were observed, though there was a tendency for colonies containing a high proportion of erythroblasts to contain a low proportion of granulocytes, and for colonies containing a high proportion of granulocytes to contain a higher proportion of colony‐forming cells. An analysis of colonies which contained cells bearing radiation‐induced chromosomal markers indicated that 83–98% of the dividing cells within 14‐day spleen colonies were derived from single precursors.
Synchronized mammalian cell cultures. I. Cell replication cycle and macromolecular synthesis following brief colcemid arrest of mitosis
Authors: Stubblefield Elton , Klevecz Robert , Deaven Larry 
Published: February 2005

AbstractChinese hamster fibroblasts in monolayer cultures were synchronized by accumulating mitotic cells in the presence of Colcemid, removing the mitotic cells with a brief trypsin treatment, and growing them in medium lacking Colcemid. Such cultures grew normally and exhibited no significant deviations from control cultures in their mitotic interval, generation time, DNA synthesis kinetics, or proliferative capacity.The macromolecular composition of 106 mitotic cells was chemically determined to be: DNA, 15 μg; RNA, 28 μg; and protein, 190 μg. In stock cultures, the corresponding values were about 60% to 70% of those for mitotic cells.The kinetics of DNA, RNA, and protein synthesis were measured throughout a 12‐hour cell cycle by incorporation of tritiated precursors. DNA synthesis began two hours after, and continued until ten hours after Colcemid recovery, with 40 minute interruptions at five and eight hours. RNA synthesis commenced at one hour and continued linearly until the fifth hour, at which time the rate abruptly doubled. Protein synthesis began immediately after cell division (0.5 hour) and continued linearly until the sixth hour, at which time its rate also doubled.The simplest interpretation of the data suggests that most of the DNA involved in transcription was replicated in the first third of the DNA synthesis period. Thereafter, the rates of RNA and protein synthesis increased because of the doubling of the active template population in each cell.
Dynamic adhesion and separation of cells in vitro II. Interactions of cells with hydrophilic and hydrophobic surfaces
Authors: Weiss Leonard , Blumenson Leslie E. 
Published: February 2005

AbstractExperiments made on the passage of cells through untreated and siliconized glass beads, and on the adhesion and spread of cultured cells on glass and Teflon surfaces show that, in the absence of serum and in its presence in low concentrations, cell adhesion and spread is sensitive to substratum wettability. On the other hand, in the presence of 100% serum, no differences in adhesive parameters are detectable. It is concluded that arguments correlating cell adhesion to surface wettability, and, by inference, surface free energy, are unsubstantiated in 100% serum, which may well approximate to the in vivo situation.The results also show no correlation between parameters of cell adhesion and cell separation, and thereby support the hypothesis that these are different processes.
Colony stimulating activity of serum from germfree normal and leukemic mice
Authors: Metcalf Donald , Foster Roger , Pollard Morris 
Published: February 2005

AbstractSerum from germfree Swiss/HaM mice exhibited a reduced capacity to stimulate granulocytic and mononuclear cell colony formation by DBA/1 bone marrow cells in vitro when compared with serum from conventional Swiss/HaM mice. Sera from germfree preleukemic and leukemic AKR mice exhibited strong colony stimulating activity, indicating that the increased colony stimulating activity previously observed in the serum of conventional leukemic mice is not the consequence of bacterial or fungal infections supervening in leukemic animals with deficient immune responses.
Fluctuation of alkaline phosphatase activity in synchronized heteroploid cell cultures: Effects of prednisolone
Authors: Melnykovych George , Bishop Carole F. , Swayze Mary Ann B. 
Published: February 2005

AbstractIn two heteroploid cell lines synchronized with thymidine double block, activity of alkaline phosphatase decreased during the 12 hour period preceding mitotic peak. A return to high values was observed during the next 12 hours of synchronous cycle. Prednisolone (11β, 17α, 21‐trihydroxy‐1,4‐pregnadiene‐3,20‐dione), when added to such cell cultures increased alkaline phosphatase activity in one of the cell lines (Henle embryonic intestine) but had the opposite effect on another line (HeLa‐S3) in which the enzyme activity was decreased. Neither effect could be demonstrated if the hormone was added at the end of S phase or if cells were arrested in metaphase by vinblastine sulfate.
The influence of progressive growth on the specific catalase activity of human diploid cell strains. I. Effect of cellular genotype: Homozygous strains
Authors: Pan Yue‐Liang , Krooth Robert S. 
Published: February 2005

AbstractThe specific catalase activity of human diploid cell strains increases with progressive growth of the culture, and falls again following subculture. Although the increase is small, it is readily demonstrable, and is exponential with time.The response of catalase activity to proggressive growth of the culture was studied in three abnormal human cell lines. A diploid cell strain, developed from a patient homozygous for the gene causing acatalasia I, had no detectable catalase activity throughout the life cycle of the culture. Another diploid cell strain, developed from a patient homozygous for the gene causing acatalasia II, had about 5% normal catalase activity, but the proportionate increase in specific activity as the culture grew was the same as for normal cells. Thus the mutation causing acatalasia II does not change the responsiveness of the cell in terms of catalase activity to progressive growth of the culture. The behavior of a heteroploid line was similar to that of the normal diploid strains, but when the growth of the heteroploid cultures reached a plateau, their population densities were four times higher than those of the diploid strains and they had about twice the specific catalase activity.
Hemopoietic progenitor cells of W anemic mice studied in vivo and in vitro
Authors: Bennett M. , Cudkowicz G. , Foster R. S. , Metcalf D. 
Published: February 2005

AbstractThe proliferation and differentiation of hemopoietic cells from genetically anemic Wv/Wx,W/Wv, and Wv/Wv mice, and from nonanemic carrier W/+, Wb/+, and Wv/+ mice have been evaluated in vivo by transplantation techniques and in vitro by the agar gel culture method. Marrow from anemic and carrier mice contained progenitor cells which were decreased in number and formed small, often rudimentary, colonies in the spleens of irradiated recipient mice. Proliferation and differentiation of both erythropoietic and leukopoietic progenitor cells were delayed and reduced, but erythropoiesis was more severely affected than leukopoiesis. The severity of the hemopoietic impairment was gene‐dose dependent. The W gene effect on leukopoietic progenitor cells was not secondary to anemia or to abnormal erythropoiesis.The marrow cells of anemic and carrier mice which form colonies of granulocytic and mononuclear cells in vitro were neither decreased in number nor impaired in proliferation and differentiation. Hypertransfusion of red blood cells increased the frequency of in vitro colony‐forming cells, but not that of in vivo progenitor cells.The data demonstrate that colony‐forming cells which proliferate in the agar gel cultures in vitro are distinct from the in vivo colony‐forming cells and suggest that the former are primitive members of the granulocytic cell line. Perhaps in vitro CFU are in an intermediate stage of differentiation between in vivo CFU and myeloblasts, analogous to that which has been suggested for the erythropoietin‐sensitive cell in the red cell series. W mutant alleles appear to act, therefore, at or very near the beginning of hemopoietic differentiation.
Analysis of growth factor gradients in hydra
Authors: Macklin Martin 
Published: February 2005

AbstractDifferential equations have been written and solved to describe the concentration gradients for the two hydra growth factors. The equations consider diffusion, catabolism and synthesis of the materials based primarily on the model of hydra growth described by A. L. Burnett. Concentration gradient profiles were obtained which correspond with the concentration gradients deduced from experimental evidence. It has also been possible to show that in areas of high mitotic rate, mitotic rate is related to the calculated concentration ratio of the two growth factors (stimulator/inhibitor). However, the correspondence of mitotic rate to growth factor concentration ratio does not hold for extreme values of the ratio indicating that very high and very low concentration ratios are not conductive to mitotic activity.
Cytological effects on Chinese hamster cells of synchronizing concentrations of hydroxyurea
Authors: Yu C. K. , Sinclair W. K. 
Published: February 2005

AbstractThe cytological effects of 2 mM hydroxyurea upon Chinese hamster cells at various phases of the cell cycle were examined. Cells in the G1, G2, or M phases of the generation cycle treated with hydroxyurea showed no chromosomal aberrations. Cell treated in S phase became moribund and eventually lysed. Some of these moribund S cells reached mitosis much later and were found to have chromatid aberrations. Cells in the log phase of growth, surviving exposure to 2 mM hydroxyurea for six hours, also showed no aberrations. Thus, viable (colony‐forming) cells, resulting from synchrony procedures with hydroxyurea are free of chromosomal aberrations.
Role of phospholipids in the aerobic endogenous metabolism of freshwater mussel spermatozoa
Authors: Higashi Satoru , Kawai Kiozo 
Published: February 2005

AbstractAerobic incubation of the spermatozoa of freshwater mussel (Hyriopsis schlegelii) caused a reduction in acyl‐ester content and a corresponding diminution in lipid‐phosphorus content. Anaerobic incubation also caused a reduction in acyl ester but a smaller reduction in lipid phosphorus, while it brought on an accumulation of free fatty acids. It was mainly palmitic and stearic acids which were accumulated during the anaerobic incubation, and they were preferentially metabolized during the aerobic incubation. Complex lipids from the spermatozoa consisted mainly of diacyl glycerophospholipids, in which phosphatidylethanolamine was predominant, followed by lecithin, while plasmalogen was a minor component. After aerobic incubation of the spermatozoa, there was a marked decrease in ethanolamine‐containing phospholipid fraction. However, no diminution was observed in the plasmalogen content. These results lead to the conclusion that mussel spermatozoa utilize as a primary energy source fatty acids which are derived from the breakdown of intracellular diacyl glycerophospholipids.